Waste Management: Research Advances to Convert Waste to Wealth (Waste and Waste Management)

WASTE AND WASTE MANAGEMENT

WASTE MANAGEMENT: RESEARCH ADVANCES TO CONVERT WASTE

TO WEALTH

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WASTE MANAGEMENT: RESEARCH ADVANCES TO CONVERT WASTE

TO WEALTH

A. K. HAGHI EDITOR

Nova Nova Science Publishers, Inc.

New York

Copyright © 2010 by Nova Science Publishers, Inc. All rights reserved. No part of this book may be reproduced, stored in a retrieval system or transmitted in any form or by any means: electronic, electrostatic, magnetic, tape, mechanical photocopying, recording or otherwise without the written permission of the Publisher. For permission to use material from this book please contact us: Telephone 631-231-7269; Fax 631-231-8175 Web Site: http://www.novapublishers.com

NOTICE TO THE READER The Publisher has taken reasonable care in the preparation of this book, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained in this book. The Publisher shall not be liable for any special, consequential, or exemplary damages resulting, in whole or in part, from the readers’ use of, or reliance upon, this material. Any parts of this book based on government reports are so indicated and copyright is claimed for those parts to the extent applicable to compilations of such works. Independent verification should be sought for any data, advice or recommendations contained in this book. In addition, no responsibility is assumed by the publisher for any injury and/or damage to persons or property arising from any methods, products, instructions, ideas or otherwise contained in this publication. This publication is designed to provide accurate and authoritative information with regard to the subject matter covered herein. It is sold with the clear understanding that the Publisher is not engaged in rendering legal or any other professional services. If legal or any other expert assistance is required, the services of a competent person should be sought. FROM A DECLARATION OF PARTICIPANTS JOINTLY ADOPTED BY A COMMITTEE OF THE AMERICAN BAR ASSOCIATION AND A COMMITTEE OF PUBLISHERS. LIBRARY OF CONGRESS CATALOGING-IN-PUBLICATION DATA ISBN: 978-1-61668-903-2 (eBook) Available Upon Request

Published by Nova Science Publishers, Inc. New York

CONTENTS

Preface vii Chapter 1 Converting Waste to Energy via Thermal, Biological

and Mechanical Processing in Developing Western Settings: An Analysis Based on Cases from England, Greece and the United States 1 Avraam Karagiannidis, Nicolas Themelis, John Barton, Stratos Kalogirou, Petros Samaras and Asterios Papageorgiou

Chapter 2 Municipal Solid Waste: Character and Composition 33 Libuše Benešová, Markéta Doležalová, Petra Hnaťuková and Bohumil Černík

Chapter 3 Waste Biomass Supply Chains for Energy Production: A Hierarchical Decision-Making Framework 81 E. Iakov, D. Vlachos and A. Toka

Chapter 4 Waste Picking at Landfills: A Source of Livelihood or Interference with Waste Disposal Processes? 121 Benjamin Bolaane

Chapter 5 Simultaneous Solution for Solid Waste Management and Waste Water Treatment: Cr(VI) Removal as a Case Study 137 Suresh Gupta and B. V. Babu

Chapter 6 Can Waste-to-Energy of as-Received or Pre-Processed (RDF/SRF) Municipal Solid Wastes Support the Electricity Generation Sector? EU Experience and a Case Study with Two Different Senarios for Greece 161 C. S. Psomopoulos

Chapter 7 The Use of Industrial Waste for the Production of New Blended Cement 191 M. C. Bignozzi

Chapter 8 Olive Mill Wastewater: Treatments and Valorisation 203 Manuela Taccari and Maurizio Ciani

Contents vi

Chapter 9 Methodological Approaches for Assessing Human Health Risks of Waste Management Plants. Experiences from Catalonia (Spain) 223 Martí Nadal and José L. Domingo

Index 235

PREFACE Waste has always been associated with human activity and is a necessary evil in any

developmental process. Today, the sheer quantity and diversity of wastes generated by industries and municipalities pose serious risks to both human health and the environment. It is imperative therefore to create awareness among entrepreneurs, manufacturers, local authorities etc. of the varied technologies evolved to treat and recycle wastes and convert it to wealth.

The arbitrary exploitation of natural resources and ignorance of the deleterious effects have resulted in the alarming increase of environmental pollution alongside the urbanization, industrialization and changing agricultural practices. Contrary to popular belief, the environmental pollution particularly in the developing countries, is not as much caused by industrial emissions or nuclear wastes as is caused by day-to-day living of human beings because industrial pollution is concentrated in certain towns and cities and can be ordered to close but no such measure can be taken for the sudden prohibition of human-derived pollution occurring at all places. The resulting solid waste, sewage and night soil pose the most daunting and widespread of all environmental problems. The disposal of the incessant piling of such waste requires proper Solid and Hazardous Waste Management

The present book is an attempt to put together the various options available to meet the twin goals of environmental conservation and sustainable development. The main aim of this new book is to bring to light the various ways of converting waste to wealth. The text throughout the book is supplemented with diagrams and tables which would facilitate quick grasping of the concepts. The book is of reference value and is intended for practicing engineers, entrepreneurs, consultants, financial institutions, researchers, and voluntary agencies. Besides, it will prove equally useful to environmentalist, development practitioners, and waste management experts.

Professor A. K. HAGHI Montréal, CANADA

In: Waste Management: Research Advances… ISBN: 978-1-61668-414-3 Editor: A. K. Haghi pp. 1-32 © 2010 Nova Science Publishers, Inc.

Chapter 1

CONVERTING WASTE TO ENERGY VIA THERMAL, BIOLOGICAL AND MECHANICAL PROCESSING IN

DEVELOPING WESTERN SETTINGS: AN ANALYSIS BASED ON CASES FROM ENGLAND,

GREECE AND THE UNITED STATES

Avraam Karagiannidis, Nicolas Themelis, John Barton, Stratos Kalogirou, Petros Samaras

and Asterios Papageorgiou

1. INTRODUCTION AND SUMMARY Municipal Solid Waste (MSW) management is a significant contributor of Greenhouse

Gas (GHG) emissions and especially the disposal of waste in landfills generates methane (CH4) that has high global warming potential. Waste management activities and especially disposal of waste in landfills contribute to global GHG emissions approximately by 4% (Bogner et al, 2007). The most common methods used for MSW, beside landfilling, include composting, recycling, mechanical-biological treatment (MBT) and waste-to-energy (WTE). The European waste policy force diversion from landfill and WTE is a waste management option that could provide diversion from landfill and at the same time save a significant amount of GHG emissions, since it recovers energy from waste which usually replaces an equivalent amount of energy generated from fossil fuels. However, disposal of MSW in sanitary landfills is still the main waste management method in many countries, both in the EU and internationally, although diversion from landfilling is generally promoted and the perspectives of new waste treatment technologies also evaluated. Thus, there are quite a few ‘developed’ countries which are really still in a developing stage in terms of sustainable MSW management and the balanced integration of WTE in their overall system. The following sections address 3 such cases from England, Greece and the US.

First, in section 2, a recent study is presented which assessed the GHG emission impacts of three technologies that could be used for the treatment of MSW in order to recover energy from it in the UK. These are Mass-Burn Incineration (MBI) with energy recovery, MBT via

Avraam Karagiannidis, Nicolas Themelis, John Barton et al. 2

bio-drying and Mechanical Heat Treatment (MHT), which is a relatively new and uninvestigated method, compared to the other two. MBT and MHT can turn MSW into Solid Recovered Fuel (SRF) that could be combusted for energy production or replace other fuels in various industrial processes. Moreover the study estimated the climate change impact of the expected increase on the amount of MSW treated for energy recovery in the UK by 2020.

Next, in section 3, another recent study is presented which aims to assess GHG emissions impact of different MSW treatment technologies currently under assessment in the new Attica’s Regional Plan in Greece. These technologies are MBT, MBI and Mechanical Treatment and are assessed in the context of different scenarios. This study utilized existing methodologies and emission factors for the quantification of GHG emissions from waste management process and found that all technologies under assessment could provide GHG emission savings. However, the performance and ranking of these technologies, is strongly dependent on the existence of end markets for the waste derived fuels produced by the MBT processes. In the absence of these markets, the disposal of these fuels would be necessary and thus significant GHG savings would be lost.

Finally, section 4 focuses in the current status of WTE in the US and especially the environmental benefits that this method offers over landfilling, in terms of GHG emissions, electricity production, land use and cost savings. Another important parameter presented here provides details in public health issues as these can be evaluated from the experience of the operating installations. The experience from the operating WTE power plants shows that the environmental impacts and important parameters regarding public health issues, such us dioxins and mercury emissions were reduced. Furthermore, the energy produced by this MSW management method enhances the benefits of the method due to the reduction of the demand in fossil fuels. In addition to this, the ongoing compatibility successful results of WTE and recycling are presented. Between 1996 and 2007, there were no new WTE facilities in the US because of environmental and political pressure. The major concern has been the perceived release of hazardous toxic substances into the environment. In the past, the primary focus of environmental groups has been on air emissions, especially of dioxins/furans and heavy metals. However, after the US Environment Protection Agency (EPA) required the implementation of the Maximum Available Control Technology (MACT) regulations in the 1990s, WTE emissions have been reduced to a point that in 2003 the US EPA named WTE one of the cleanest sources of energy.

It is aspired that, in each of the 3 presented cases, the drawn conclusions could be of further use and applicability also in other ‘developing’ MSW management systems of both ‘developed’ and ‘developing’ countries.

2. CLIMATE CHANGE IMPACT ASSESSMENT OF WTE TECHNOLOGIES IN ENGLAND

WTE is not widespread for the moment in England, by contrast to other European

countries where it is an important element of their national waste strategies. In 2005 only 9% of MSW in England was treated in WTE plants, the majority of which are MBI with energy recovery. MBI enable moving grate technology for the combustion of waste and they are designed to handle large volumes of MSW with no pre-treatment (Williams, 2005). Usually

Converting Waste to Energy via Thermal, Biological and Mechanical…

3

the heat from the incineration of waste is used in turbines to generate electricity, while the remaining heat of the process is discarded. In Combined Heat and Power (CHP) plants, the residual heat is recovered and exported to adjacent industrial premises or districts for space heating and hot water supply.

Another technology used for energy recovery from MSW is MBT that partially processes mixed MSW by mechanically removing some parts of the waste and by biologically treating others. There are numerous possible permutations of MBT with different outputs, such as metals, low-grade conditioner, stabilised waste for landfill or SRF (Juniper, 2005). In the case of SRF production, the most common configuration incorporates bio-drying prior to mechanical treatment. Bio-drying drives-off moisture from the waste using the biological activity in an aerobic in-vessel system but does not fully bio-stabilise the waste. The reduction of moisture and the degradation of a part of the more volatile biodegradable fraction of the waste, increase the calorific value of the produced SRF rendering it like this a very attractive option for thermal treatment with energy recovery or co-incineration in industrial processes (Juniper 2005, p.A-48).

A relatively new technology for the treatment of MSW is MHT. This technology uses a thermal or steam-based pre-treatment process prior to mechanical treatment of MSW. A commonly used steam based technique to treat the waste is via autoclave technology that has been used to sterilise medical waste for many years (DEFRA, 2004). In this plant, saturated steam at 160°C is first injected into the rotating vessel containing the waste over a period of 15 minutes, which may vary depending on the specific heat capacities of the waste materials being processed and the amount of waste in the autoclave. The vessel will be maintained at high pressure for a period of up to 45 minutes to allow the process to break the waste down into its organic and inorganic constituents. Processed waste is then treated by a series of screens and recovery systems to achieve secondary recycling and separation of the predominantly cellulose fibre, with residue left for landfilling. The resulting fibre comprises the putrescible, cellulose and lignin elements of the waste stream, could be used as SRF (Environment Agency [online], 2006).

2.1. Energy from Waste and Climate Change Many studies assessed the GHG emission impacts of MBI and found that not only it can

offer significant reduction of CH4 emissions compared to landfilling, but at the same time it can provide additional net GHG emission savings due to the recovery of energy (Porteous, 2005). Despite these benefits of this technology in terms of climate change, there is a strong opposition against MBI, as it is considered hazardous for the human health and it is claimed to undermine recycling of valuable resources. Nevertheless, even with the most optimistic estimations on waste minimization, reuse, recycling and composting, England will have a significant amount of residual MSW that will either have to be disposed or it could be treated for recovering energy from it. DEFRA in a review of England’s Waste Strategy (DEFRA, 2006) suggested that about 27% of the MSW stream will be treated for energy recovery by 2020, compared to 9% in 2005. MBI with energy recovery could be a potential treatment for this amount of waste, as well as MBT and MHT configured for SRF production. However, MHT is a relatively new technology and its climate change impact has not been assessed yet. On the other hand, there are studies that have assessed the GHG impact of MBT plants that


use aerobic biological treatment or composting for the stabilization of waste or production of compost. However, the most commonly used biological treatment method in MBT plants configured for production of SRF, is bio-drying and as this configuration has not been examined in detail in previous studies, it should be assessed as well.

2.2. Methodology

2.2.1. MSW Treatment Options A model was developed in order to assess the GHG emissions of the waste treatment

options under consideration in this study. The MSW management system for each of these options is presented in figure 2.1. MSW is transferred after a kerbside collection scheme, from households to the treatment facilities via a transfer station.

In Option 1, a part of the bottom ash from the MBI facility, as well as the metals in the bottom ash are sent to a reprocessor for recycling. The rest of the bottom ash and the ash from the Air Pollution Control (APC) system are landfilled. The examined MBI process in this study was based on the technology used in the SITA Kirklees plant and is described in the Waste Technology Data Centre (WTDC) (WTDC [online], 2006). Three different cases for the recovery of energy from waste were examined. In the first case, there is no recovery of energy whereas in the second case, the incinerator was assumed to generate electricity only, with a 25,4% efficiency. In the third case, the plant was assumed to be a CHP MBI with a 65% overall efficiency and a 0.4 average power-to-heat ratio.

In Option 2 the outputs of the MBT process are metals, residues and SRF. The metals are recovered for recycling and the residues are landfilled. Three different cases for the use of SRF have been examined, namely that it is either combusted in a CHP Fluidised Bed Incinerator (FBI), or it replaces coal in a power plant or in a cement kiln. The bottom and the APC ash from the FBI are landfilled. The ash from the combustion of SRF in the cement kiln is used for the production of clinker and the ash from the combustion of SRF in the power plant disposed with the rest of the produced ash. The examined MBT process is based on the MBT plant in Dresden, Germany that incorporates the Herhof bio-drying process. The process was sourced from the report MBT: A Guide for Decision Makers-Processes, Policies & Markets (Juniper, 2005).

In Option 3 the outputs of the MHT plant are recyclables, residues and SRF. The recyclables are metals and inert residue (mainly glass) that is used as secondary aggregate, while the residues are landfilled. Similarly with the MBT-option, the SRF is treated thermally either in a CHP FBI, or in a power plant or in a cement kiln. The examined process in the study is based on the proposed process of Thermsave that incoporates autoclaving of MSW and mechanical treatment and is presented in the WTDC (WTDC [online], 2006).

Mass balances for each of the examined processes were compiled, based on the residual MSW composition and a number of key assumptions on sorting fractions and efficiencies in the plants. The residual MSW composition was calculated from the MSW composition presented in the study Analysis of household waste composition and factors driving waste increases (Parfitt, 2002) and for a kerbside collection scheme with 60% paper recovery, 40% glass recovery, 10% textile recovery and 10% ferrous and non-ferrous metals recovery.


5

Figure 2.1. MSW management systems in the examined options.

2.2.2. Quantification of Emissions

A model was developed which aimed to quantify the emissions of Carbon Dioxide (CO2), Methane (CH4), Nitrous oxide (N2O), Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs) and Sulphur hexafluoride (SF6), which are the GHGs of interest under the Kyoto Protocol. In order to quantify the GHG emissions, Emission Factors (EFs) for the activities that are associated with the management of waste in each of the three options, were sourced from previous studies. When EFs could not be found in the literature, methodologies for the estimation of GHG emissions proposed by the Intergovernmental Panel on Climate Change (IPCC) in the Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories, were used. The calculated emissions of the activities were converted to CO2 equivalents using global warming potentials for a 100-year time frame (IPCC, 1996).

Figure 2.2. Model boundary.

In general, the model included both direct and indirect GHG emissions from the waste management system. Direct emissions result from waste treatment within the waste management system, i.e. material and energy flows within the system. Indirect emissions take place in systems outside the waste management system as results of activities within the latter and occur when material and energy flow to and from the waste management system (Soderman, 2003). Direct GHG emissions derive from the incineration and disposal of MSW or SRF and the consumption of fossil fuels inside the waste management system. Indirect emissions are generated by the consumption of electricity and indirect emission savings


derive from materials recycling and energy recovery from waste. The model boundary is summarised in figure 2.2.

2.2.3. Scenarios

The assessment of the climate change impact of the expected increase of MSW treated for energy recovery in England, from 9% in 2005 to 27% in 2020, was made in the context of five different scenarios. For the development of scenarios, it was assumed that the waste growth will be 1,5% per year, nationally and until 2020, as DEFRA suggests in the Review of England’s Waste Strategy (DEFRA 2006, p.17). The starting date for the scenarios was taken to be 2008 and it was assumed that the amount of residual MSW treated in WTE plants would increase gradually, from 2008 to 2020. By taking into account these assumptions, it was found that 3,8 million t of residual MSW in 2008, 7,7 million t in 2015 and 10,2 million t in 2020, would be treated for energy recovery. The developed scenarios are presented in table 2.1. The rationale behind the development of scenarios 4 and 5 is that the assumption in scenarios 2 and 3 that there will be an end market for the SRF is very optimistic. Recent studies have found that co-incineration of SRF in power plants is rather unlike, mainly due to technical, economical and regulatory constraints and only 346.000 t of SRF in 2008 and 439.000 t in 2020 are estimated to be co-incinerated in cement kilns (Juniper, 2005). Therefore, in scenarios 4 and 5 it was assumed that only a limited amount of MSW would be treated in MBT and MHT plants in order to produce an amount of SRF equivalent to the ‘realistic’ capacity of cement kilns for SRF.

Table 2.1. Presentation of scenarios.

Scenario Description Scenario 1 3,8 million t of residual MSW and 10,2 million t in 2020, will be incinerated with recovery of heat

and power. The majority of the existing incinerators in England recover only electricity; however it was assumed that they would change to CHP mode by 2008, whereas all the new incineratorswould be CHP applications.

Scenario 2 The capacity of MBI will increase to 3,7 million t until 2008. From 2008 onwards no newincinerators will be built and new MBT plants configured for SRF production will treat the remaining amount of MSW; there will be an end market for the produced SRF with half of it used in cement kilns and the other half in power plants.

Scenario 3 Like in scenario 2 from 2008 and onwards, no new MBI will be build and the majority of residual MSW will be treated in MHT for production of SRF that is used in power plants and cement kilns.

Scenario 4 Only a limited amount of residual MSW will be treated in MBT plants and converted to SRF, according to the ensured end market in cement kilns. The rest of the MSW that is expected to be treated for energy recovery will be incinerated in CHP MBIs.

Scenario 5 Like in scenario 4, only a limited amount of residual MSW will be treated in MHT plants and converted to SRF that will be co-incinerated in cement kilns. The rest of the residual MSW will be incinerated in CHP MBIs.

2.3. Results and Discussion

2.3.1. GHG Emissions for the Treatment Options

The results of the model are presented at this point. The overall emissions EFs (kg CO2-eq/t of MSW treated) as they were calculated for the MBI, MBT and MHT options are illustrated in Figure 2.3.


7

MHT/SRF to cement kiln

Figure 2.3. Overall EFs (kg CO2-eq/t of waste treated) for the MSW treatment options.

From figure 2.3 it can be seen that only the cases of incineration of MSW without energy recovery and incineration with electricity generation, produce GHG emissions. The treatment option that performs better is MHT, when the produced SRF is co-incinerated in a cement kiln and the next best option is MBT when the material is co-incinerated in a cement kiln, as well. Hence, it can be postulated that the way that the SRF is treated finally, affects the total EFs. For instance, if an end market can be identified and the SRF is co-incinerated in a cement kiln or a power plant, then MHT and MBT are great options for the treatment of MSW, with MHT performing fairly better than the MBT. On the other hand, it can be deduced from figure 2.3 that MBT with SRF combusted in a FBI performs worst than combustion of untreated residual MSW in a CHP MBI, whilst MHT with SRF performs slightly better than CHP MBI. Therefore, it can be concluded that MBT and MHT configured for SRF could provide significant GHG emission savings, provided that there is an end market for the SRF from the existing industry and especially power plants or cement kilns.

2.3.2. Sensitivity Analysis on Treatment Options: SRF Landfilling

There are examples of companies that use SRF, like the Castle Cement which is using it in its kilns (ENDS, June 2006, p.23); however, the market of these fuels is full of uncertainty and the current demand is not so high. Thus, it is still possible for these materials to end in a landfill. Apart from the increased cost to the operators due to landfill tax, landfilling of the SRF could have an adverse climate change impact. In the majority of the studies it is assumed that SRF is stabilised because of the biological treatment in the MBT and hence, will not produce significant amounts of CH4. However, the present study examined the case of a MBT plant incorporating a bio-drying process, that does not reduce the biodegradable content of the waste or it reduces only a small amount of it, namely about 10% (Juniper 2005, p.D-163). Therefore, if the SRF was landfilled, it could produce CH4. Regarding SRF from MHT, it is yet unknown what are the effects of the autoclaving process on the organic fraction of household waste, but in general it is unlikely that the process will reduce the biodegradable content of the organic waste fraction (AiIE, 2003). Hence, the landfilling of SRF from MHT could produce CH4 emissions as well. The new EFs for MBI as well as for MBT and MHT options when the SRF is landfilled are shown in figure 2.4. This figure demonstrates how


important is for the MBT and MHT options, the existence of an end market for the SRF. When there is no market and the SRF is landfilled, the total EFs for the MBT and MHT options are now positive and the performance of these two options is even worst than a MBI with electricity generation only.

MBT/SRF to landfill

Figure 2.4. EFs when SRF is landfilled.

2.3.3. Scenarios The scenario analysis has demonstrated that in all scenarios the expected increase in the

amount of residual MSW treated in WTE plants, will save a significant amount of GHG emissions. Thus, in scenario 1, net GHG emission savings in 2020 will be 1.3 million t CO2-eq. Likewise in scenario 2, emission savings in 2020 will be 2.8 million t CO2-eq and in scenario 3, 3.1 million t. In the most realistic scenarios 4 and 5, emissions savings in 2020 will be 1.5 million t and 1.6 million t CO2-eq, respectively. Overall results for Scenarios 1-5 are shown in figure 5. Hence scenario 2 and 3 perform much better than the others. For instance, in scenario 3 the emission savings are twice as much as in scenario 1. Nevertheless, the good performance of scenarios 2 and 3 depends strongly on the optimistic assumption that there is a market for the produced SRF.

2.3.4. Sensitivity Analysis on Scenarios with No End-Market for SRF

This section examines the case when there is no market for the SRF and the material would need disposal in a landfill. As it can be seen from figure 2.6, scenario 1 is not sensitive in this change and generates the same emission savings, as before. On the other hand landfilling of SRF affects substantially scenarios 2 and 3 and less 4 and 5. Especially scenario 2, in 2020 produces net GHG emissions. Thus when there is no market for SRF, the performance of scenarios 2 and 3 is suppressed, while the performance of scenarios 4 and 5 is not affected significantly, as the majority of MSW in these scenarios is treated in CHP MBI. Nevertheless, it can be noticed that scenarios 4 and 5 perform worse than scenario 1, in which all of the residual MSW is treated in CHP MBIs.

210,12

3,96

-128,92

88,1354,21

-200

-150

-100

-50

0

50

100

150

200

250

Kg

CO

2 -eq

/t of

was

te

MBI without energy recovery MBI with electricity generationCHP MBI MBT/SRF to landfillMHT/SRF to landfill


9

Figure 2.5. GHG emissions (kt CO2-eq) for all five scenarios.

Figure 2.6. GHG emissions (kt CO2-eq) for all five scenarios when there is no market for SRF

2.4. Conclusions

The study showed that all WTE options under consideration could save GHG emissions

under certain conditions. MBI saves emissions when it operates in CHP mode, whilst it produces emissions when it generates electricity only. Both MBT and MHT have significant GHG benefits, when the SRF output is co-incinerated in cement kilns or power plants, whereas when it is combusted in a CHP FBI it saves substantially less emissions. However the performance of MBT and MHT in terms of climate change impacts, depends strongly on the existence of an end market for the SRF. This approach was confirmed by a sensitivity analysis with which it was demonstrated that when the SRF is finally disposed to a landfill, both MBT and MHT generate net GHG emissions.

Furthermore, this study estimated the climate change impact of the increase in the amount of MSW. Scenario analysis showed that the expected increase of residual MSW treated for energy recovery, could ensure significant net GHG emission benefits in England, irrespectively of the used technology. Scenarios 2 and 3 showed great savings, but they were based on very optimistic estimations. The most realistic scenarios 4 and 5 took into account


the realistic potential capacity for SRF in cement kilns and demonstrated that the GHG emission benefits in this case are fairly more than scenario 1. Therefore, it could be deduced that the MHT and then the MBT option, in order of preference, should be used for treatment of residual MSW in the scale that SRF market could be established, while the rest of the residual MSW should be treated with CHP incineration. In this way additional GHG benefits could be achieved than in the case where all the residual MSW is treated in CHP incinerators.

The significance of the study presented in this section is that it has also assessed the GHG emission impacts of MHT which is a new treatment technology for MSW and has not been assessed yet. In addition, it has assessed the performance in terms of climate change, of a configuration of MBT that was not examined in detail in previous studies. Moreover, this study has carried out a comparative assessment in terms of climate change, for three WTE technologies, by taking into account the current practice and the policy and legislative framework of these technologies in England.

3. MSW MANAGEMENT SCENARIOS FOR ATTICA AND THEIR GHG EMISSION IMPACT

In Greece, the main method of solid waste management remains still landfilling; apart

from this, 22 Material Recovery Facilities (MRF) are in operation for source segregated ‘blue-bin’ recyclables, whereas 5 MBT plants processing residual Municipal Solid Waste (MSW) operate currently in Attica, Chania (Crete), Kefalonia, Herakleion (Crete again) and Kalamata (Psomopoulos 2008; HSWMA, 2009). Nevertheless increasing environmental concerns, public pressures and the European and Hellenic waste policy and legislation that force diversion from landfill through sustainable waste management, necessitate investments in more new treatment plants for MSW, including biological and thermal treatment of MSW. In this context, the 13 Regional authorities in Greece have issued Regional Plans, where the need for new MSW treatment facilities is recognized and operationalised (Hellenic Ministry for the Environment, Physical Planning and Public Works, 2007).

In Attica Region (i.e. the Greater Athens area) 2.200 million t MSW (wet weight) were generated in 2008, of which 12% were recycled and 350,000 t were treated in the existing MBT plant at the Liossia site (Eurostat, 2009;HSWMA, 2009) (Figure 3.1). Given that the Hellenic waste management policy only recently started to address waste minimization measures like home composting and Pay As You Throw (PAYT) schemes, the waste growth is anticipated to remain in the future at present levels (i.e. 1.1% per annum in 2007 – cf. Eurostat, 2009) or even to increase. By taking into account the forecasted growth on population (Eurostat, 2009), if waste growth rates remain at present levels, 2.8 million t of MSW will be generated annually by 2030. Even if source segregation is enhanced and consequently recycling rates increase, a significant amount of residual MSW will still have to be diverted from landfills in order for the targets of the Landfill Directive 99/31/EC to be met (Figure 3.1).

Therefore, new waste management infrastructure is necessary and in Attica’ s Regional Plan a new Integrated Waste Management Center (IWMC) in Liossia in Western Attica is proposed, where new plants with a total annual treatment capacity 1.1 milion t will be constructed and operated in conjunction with the existing MBT plant, providing a total


11

capacity of 1.45 million t of MSW. Moreover, two other IWMC are proposed in North-East and in South-East Attica of a total annual capacity of 250,000 t. For each of these two IWMC in Eastern Attica, MBT plants incorporating Anaerobic Digestion are proposed, while various waste management treatment technologies, such as MBI, MT and MBT have also been evaluated for the IWMC in Western Attica, which when completed is anticipated to become one of the largest IWMC in the world. The aim of the presented study was to assess the GHG emission impacts of the proposed technologies for the IWMC in Western Attica in the context of different scenarios.

Figure 3.1. Foreseen MSW management in Attica until 2030 according to existing facilities.

3.1. Treatment Technologies The majority of the WTE plants use moving grate technologies and they are designed to

handle large volumes of MSW with or without pre-treatment. As already described in section 3, usually, the steam produced from the incineration of waste is used in turbines to generate electricity, while the remaining heat of the process is discarded. In the Combined Heat and Power (CHP) incinerators, the residual heat is recovered and exported to adjacent industrial premises or districts for space heating, hot water supply, industrial heat demand and other duties (Williams, 2005).

Another technology for treatment of MSW is MT. A MT plant or ‘dirty’ MRF processes mixed residual MSW by contrast to a ‘clean’ MRF that process source segregated recyclables. A MBT plant incorporates trommel, conveyors and hand picking lines, separators, magnetic


separators, eddy current separators, and potentially near infrared detection devices, shredders and baling equipment (AEA, 2001). As MT plants receive mixed MSW with high putrescible content they usually recover metals and RDF from the coarse fraction of input material.

MBT is another treatment option for residual MSW. MBT partially processes mixed MSW by mechanically removing some parts of the waste and by biologically treating others. Generally a wide range of MBT plant configurations exist, depending on the various processes that are integrated into MBT and the outputs of the process. The biological process of a MBT plant may either take place prior to or after mechanical treatment of the waste, depending on the outputs of the plant and could be either aerobic composting (in-vessel or tunnel), or anaerobic digestion (AD) or bio-drying (Enviros Consulting Limited, 2007). Within this study MBT with aerobic composting is defined as MBT(C), MBT with AD as MBT(AD) and MBT with bio-drying MBT(BioD).

MBT(C) plants incorporate mechanical treatment for recovery of recyclables with aerobic in-vessel composting to minimise the biodegradability of waste and produce a bio-stabilised output. Usually in these plants Refuse Derived Fuel (RDF) is recovered from the coarse fraction of materials going to the biological process stage (Archer et al, 2005).

MBT(AD) plants include mechanical separation with anaerobic digestion to recover recyclables (and potentially RDF) and produce biogas that is usually combusted for energy recovery. Some MBT(AD) plants combine anaerobic digestion process with post-digestion aerobic composting that further bio-stabilize the biodegradable content of waste and produce a bio-stabilised output that could be landfilled or used as soil improver (Archer et al, 2005).

MBT(BioD) plants utilize bio-drying to drive-off moisture from the waste using the biological activity in an aerobic in-vessel system (boxes). The reduction of moisture and the degradation of a part of the more volatile biodegradable fraction of waste, increase waste’s calorific value and produce a Solid Recovered Fuel (SRF) rendering it an option for co-incineration and energy recovery. In MBT(BioD) plants the waste remains in the system usually for a week, by contrast to MBT(C) where the waste remains at least for 3 weeks and hence the bio-drying process does not fully biostabilise the waste. (Archer et al, 2005).

In the present section, both terms RDF and SRF are utilized. For the moment, there are is only the CEN 343 Draft European standard for SRF and the legal definition of the term SRF has not yet been finalized. In general, both terms are used across European countries to describe fuels derived from non-hazardous MSW. Quite often, the terminology used in different countries to describe waste-derived fuels may reflect the desire of the users to have the material treated in a specific way under existing national legislation (Gendebien et al, 2003). Within this section, the term SRF is used for fuels derived by MBT(BioD) as these plants are dedicated on the production of these fuels and therefore they are anticipated to amend their production lines, if it is necessary, in order to adjust the SRF attributes to the requirements of the new European Standard. The term RDF is used for fuels derived by MT, MBT(C) and MBT(AD) plants, as these fuels derive from the coarse fraction of waste before biological treatment and their quality will be more difficult to define.

In general there are various options for the utilization of RDF and SRF, such as combustion in WTE plants or pyrolysis or gasification plants for energy recovery, or even co-incineration in cement kilns and power plants, where they substitute fossil fuels; however the market of these fuels is extremely volatile and quite often end up in landfills, like the RDF produced by the MBT in Liossia as well (Tsatsarelis and Karagiannidis, 2007).


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3.2. Methodology The present study aimed to quantify Carbon Dioxide (CO2), Methane (CH4) and Nitrous

oxide (N2O) emissions from waste management activities in the Attica scenarios under assessment. CO2, CH4 and N2O are the major GHG emissions generated by MSW management and of significant interest under the Kyoto Protocol (IPCC, 1997; 2006). For the quantification of GHG emissions from the treatment of MSW in each of the scenarios, a validated methodology (Papageorgiou et al, 2009) was adopted and Emission Factors (EFs) were sourced from previous studies that assessed the GHG emissions impact of MSW treatment technologies and were applied in this study adjusted to the Hellenic MSW composition. It should be mentioned that the performance of the modelled technologies could potentially be different when applied to Greece, however due to lack of data, it was not possible model technology application specific to Hellenic conditions.

3.3. Treatment Scenarios Five scenarios described next were compiled based on published information on the

technologies proposed in the Attica’s Regional Plan and treatment capacities of the proposed plants. The MSW management system for each of the scenarios is presented in figure 3.2. In these scenarios residual MSW is transferred by means a kerbside collection scheme, from households to treatment facilities, via transfer stations.

Scenario 1

400,000 t of residual MSW are treated in a MBT(C) plant and 700,000 in a WTE plant. MBT(C) outputs include ferrous and aluminium metals, bio-stabilised output, residues and RDF. Metals are recovered for recycling, while the bio-stabilised output and residues are disposed in a landfill, whilst RDF substitutes coal in a cement kiln. The bottom ash from the combustion of RDF in the cement kiln is used for the production of clinker. In the WTE plant, the ferrous metals recovered from the bottom ash are sent to a reprocessor for recycling, whilst the bottom ash and the APC ash are both landfilled in a sanitary and a hazardous landfill cell respectively. The WTE plant recovers electricity only with a net electrical efficiency of 22.6 % (related to the NCV of waste), in order to be qualified as recovery operation according to the requirements new Directive on Waste (2008/98/EC) (Karagiannidis et al, 2009)

Scenario 2

400,000 t of residual MSW are treated in a MBT(AD) and 700,000 t in a WtE. MBT(AD) outputs are ferrous and aluminium metals (sent for recycling), residues and bio-stabilised output that are disposed to landfill, RDF that substitutes coal in cement kilns and biogas which is combusted for electricity generation with efficiency 37%. It is assumed that 33% of the produced electricity is used in-house for the operation of the plant and 65% is exported to the grid. The WTE plant is similar with that in Scenario 1.


Scenario 3 400,000 t of residual MSW are processed in a MBT(C) (like Scenario 1) and 700,000 t in

a MBT(BioD). MBT(BioD) outputs are metals sent for recycling, residues disposed to landfill and SRF that substitutes coal in a cement kiln. Ash from SRF combustion in the cement kiln is included in clinker production.

Scenario 4

400,000 t of residual MSW are treated in a MBT(AD) (like Scenario 2) and 700,000 in a MBT(BioD) (like Scenario 3).

Scenario 5

250,000 t of residual MSW are processed in a MT plant and 850,000 in a WtE. MT outputs are metals sent for recycling, RDF that substitutes coal in a cement kiln and residues that are landfilled.

Figure 3.2. Waste Management Scenarios for the IWMC in Western Attica.

SRF and RDF were assumed to substitute coal in cement kilns, as this would be the only option for these fuels in Greece, since there are no existing WTE at the moment, whereas coal


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power plants that could potentially combust these fuels are located in Northern Greece and SRF/RDF transportation from Attica might be very difficult due to logistics constraints. In Scenarios 1, 2 and 5, RDF from the MBT(C), MBT(AD) and MT plants could be combusted in the WTE plants instead, but this case was not assessed initially, as the proposed capacities of WTE plants in the Regional Plan, are only for residual MSW and not additional RDF. However, in case that there is no market for these fuels, WTE plants could combust them after investment for capacity extension.

It should be mentioned, that the case of CHP WTE plants was not evaluated as the demand for heat is anticipated to be low due to the current conditions in the Attica’s waste-derived heat and industrial market and system. CHP WTE plants would be beneficial in Greece only if they were sited near industries that have constant demand for heat and steam, but the Liossia site of the proposed IWMC is far from industries.

3.4. Residual MSW Composition

Table 3.1. MSW, packaging waste and residual MSW composition and physical analysis.

MSW composition, as well as the fraction of packaging waste in MSW in Attica are

displayed in table 3.1 (Technical Chamber of Greece, 2006; Eurostat, 2009). In the present analysis, it was assumed that the treatment plants in each scenario treat residual MSW, after kerbside collection. For the estimation of the future residual MSW composition, it was assumed that the targets set by the Packaging Waste Directive (99/42/EC) would be met and hence 60% w/w of packaging glass, 60% w/w of paper and cardboard, 50% metals w/w, 22,5% w/w plastic and 15% w/w wood would be recycled.


The residual MSW is taken as the input to the waste management system of each scenario and its composition is also shown in table 3.1. The same table displays the Net Calorific Value (NCV), moisture, carbon and Degradable Organic Carbon (DOC) content of residual MSW, as well as the fossil carbon fraction of total carbon in the residual waste (IPCC, 2006; Papageorgiou 2009). Based on the residual MSW composition, mass balances for each of the examined scenarios were compiled and are shown in figure 3.2.

Table 3.2. Direct and indirect emission impacts included in the model.


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3.5. Quantification of GHG Emissions In the present study the methodology presented in Papageorgiou et al, 2009 was applied

for the quantification of GHG emissions from the treatment of residual MSW in each scenario. This methodology proposes a life-cycle perspective for setting model boundaries and utilizes Emission Factors (EFs) based on Life-Cycle Inventories and methodologies proposed by the Intergovernmental Panel on Climate Change (IPCC, 1997; 2006) for emission quantification. In a full life-cycle perspective, biogenic CO2 emissions are considered neutral to global warming, because they originate from organic matter generated by an equivalent biological uptake of CO2 during plant growth. Conversely, emissions of CO2 from combustion of fossil carbon do have a global warming potential because this release is not balanced by a ‘recent’ uptake of CO2 (IPCC, 2006; Christensen et al, 2007).

In the present study, both direct and indirect GHG emissions generated by direct and indirect activities in the waste management system of each scenario, were accounted for (Consonni et al., 2005; Liamsanguan and Gheewala, 2008). Direct emissions result from activities within the waste management system, i.e. material and energy flows within the system, whilst indirect emissions take place in systems outside the waste management system, as a result of activities within the latter and occur when materials and energy flow to and from the waste management system (Soderman, 2003). The direct and indirect emission impacts that were included in the model are summarized below in table 3.2.

3.5.1. Direct Emission Impacts

Direct CO2 emissions derive from the incineration of fossil carbon in MSW or in RDF and SRF and they were calculated based on the on the composition of waste, the carbon content and the proportion of fossil carbon of each waste fraction in MSW, according to the methodology proposed by IPCC (IPCC, 2006). N2O emissions from the combustion of waste and wasted derived fuels are included in the model and the EF 0.02 kg/t MSW was applied (IPCC, 2006).

Moreover, CO2 emissions are generated by the consumption of diesel for the operation of the facilities and the EU EF for diesel consumption was utilized since there is no EF reported for Greece. The EU EF is 3.17 kg CO2-eq /kg of diesel and it was taken from GEMIS inventory (GEMIS, 2009).

CH4 and N2O emissions are generated from aerobic composting processes as well and they were included in the model for the MBT(C) plant. For the estimation of these emissions the EFs 1 kg CH4/t MSW and 0.1 kg N2O/t MSW were used (IPCC, 2006). For the MBT(AD) plant CH4 emissions due to leakage are assumed to be negligible, whilst CH4 and N2O emissions from bio-drying of MSW were not included in the model as they are anticipated to be very low due to small duration of the process (1 week) comparing to aerobic composting processes (3-4 weeks).

Finally, for the estimation of CH4 emissions from landfilling of residues from the treatment processes, the mass balance (Tier 1) method was applied. This method was proposed in the Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories (IPCC, 1997), which assumes that all the methane is released from the waste in the year of disposal. Although this method does not generate as accurate estimates as the First Order Decay method (Tier 2), it was preferred in this study as it can give an annual estimate of CH4 emissions per t of waste landfilled, which is necessary for the calculation of overall EFs for


the processes assessed in the scenarios. For the Tier 1 method, it was assumed that the landfill where the residues are disposed is an engineered landfill, where 80% of the landfill gas is captured and flared without energy recovery. DOC for every fraction of residual waste is presented in table 3.1. The Methance Correction Factor (MCF), Fraction by volume of CH4 in landfill gas, Oxidation factor and the fraction of DOC dissimilated (DOCF) were sourced from the more recent 2006 IPCC Guidelines for National Greenhouse Gas Inventories (IPCC, 2006).

3.5.2. Indirect Emission Impacts

For the estimation of indirect emission impacts from electricity provision for the operation of treatment plants information on energy utilization of MSW management systems were sourced from literature (AEA, 2001; Fischer, 2006). The EF for the average electricity mix of Greece is applied for estimating both the GHG emissions from consumption of electricity in the processes and the GHG emission savings from energy recovery. The EF for the Hellenic electricity mix is estimated to be 0.783 kg CO2-eq/kWh in 2010 according the Global Emission Model for Integrated Systems (GEMIS) inventory, which includes data for the whole life cycle of energy production (fuel extraction, transport, conversion, combustion, distribution) (GEMIS, 2009). In the case of co-incineration of RDF and SRF in a cement kiln, the fuel was assumed to substitute coal on an energy equivalent basis (i.e. 1 GJ of RDF/SRF substitutes 1 GJ of coal). Hence, the combustion of SRF replaces emissions from the combustion of coal that would generate equivalent energy. The NCV of coal used in cement kilns is 24.9 GJ/t (Papageorgiou, 2009) and the EF for the combustion of coal in cement kins is 93 kg CO2/TJ of fuel (EEA, 2007). Regarding recycling of metals, the EFs for recycling offset of ferrous metals is -434 kg CO2-eq/t and for aluminium metals -11634 kg CO2-eq/t (Fischer, 2006).

In this study carbon sequestration in landfills as well as in soils as a result of application of the bio-stablizied output from MBT plants has not been included in the model of this study, as it it is not considered in the IPCC methodology (IPCC, 1997; 2006)

GHG emissions from the use of fossil fuels for MSW transportation, were not included in the model as the proposed site for the new IWMC in Western Attica is common for all scenarios and, moreover, the sanitary landfill where the residues of the processes will be disposed is at the same site. The only differences on GHG emissions could be derived from transportation of waste and materials to various re-processors, RDF/SRF to cement kilns and APC ash to a hazardous waste landfill. However, main re-processors of recyclables in Greece are based near Attica, whilst there are two cement kilns near Athens that could be potential licensed users of RDF and SRF. Finally, the only hazardous landfill in Greece where APC ash could be disposed is in Attica (Laurio) as well. Thus, the differences on GHG emissions from the transportation of waste and materials via different routes, is estimated to be negligible.

The EFs (kg CO2-eq/t of MSW treated) estimated for all activities involved in the waste management system of every examined scenario, are summarized in table 3.3. The EFs of these activities were converted to CO2-eq using global warming potentials for a 100-year time frame (IPCC, 1996) and all are expressed in the units of kg CO2-eq /t MSW treated.


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Table 3.3. EFs for the waste management options in the scenarios (kg CO2-eq/t MSW)

3.6. Results and Discussion

Figure 3.3. GHG emissions (Gg CO2-eq) for all five scenarios.

From figure 3.3, where the results of the analysis are illustrated, it can be seen that all scenarios under assessment in this study for Attica could generate GHG emission savings. Scenarios 3 and 4 are those that perform better, followed by Scenarios 2, 1 and 5. Scenario 3 incorporates MBT(C) with RDF production and MBT(BioD) with SRF production. Both of these fuels were assumed to substitute coal in cement kilns, as this would be the only option for these fuels, since there are no WtEs in Greece for the moment. In general the performance of all Scenarios and especially Scenarios 3 and 4 are strongly dependent on the existence of a final market for the produced RDF and SRF. However the market for these fuels is extremely


volatile and there many cases where these fuels end up in landfills instead of being utilized for energy recovery. For instance, in Attica, the RDF produced from the only existing MBT in the Region is (up to 2009 still) landfilled, since the agreement for its utilization in a proximate cement kiln in Evoia, has so far failed to be implemented due to public opposition (Tsatsarelis and Karagiannidis, 2008). Similarly, in Germany in 2007, almost 7 million t of SRF were produced but only 3.2 million t of were used as secondary fuel in SRF-dedicated incinerators, coal-fired power plants and cement kilns, whilst the rest where stored for future use (Schingnitz et al, 2008). Therefore, it was deemed as absolutely necessary to perform a sensitivity analysis on the case where there is no market for these fuels.

3.7. Sensitivity Analysis on Scenarios The sensitivity analysis aimed to evaluate what would be the GHG emission impact in the

case that no end market is found for the produced RDF and SRF from the MT, MBT(C), MBT(BioD) and MBT(AD) plants in the assessed scenarios. In this case, GHG emission savings from energy recovery of these fuels should not be taken into account, whereas potential CH4 production from the degradation of the biodegradable content of these fuels should be assessed, if they are finally disposed in a landfill. Especially a MBT(BioD) plant incorporates a bio-drying process, that does not reduce the biodegradable content of the waste or it reduces only a small amount of it, about 10% (Adani et al 2002; Archer et al, 2005) and thus the disposal of SRF in landfill will surely generate CH4. Moreover, RDF in the MBT(C) and MBT(AD) plants is recovered before the biological process and thus the biodegradation of their organic fraction due to disposal in landfills will generate CH4 as well. The results of the sensitivity analysis and the GHG emissions from the treatment of MSW in each of the scenarios are displayed in figure 4. In the sensitivity analysis of the scenarios it was assumed that the WtE facilities in Scenarios 1, 2, 5 will increase their capacity and finally combust the surplus RDF from the MBT(C), MBT(AD) and MT respectively. On the other hand, in Scenarios 3 and 4, where no thermal treatment plant is foreseen, it was assumed that the produced RDF and SRF will finally end up in landfill.

From figure 3.4 it can be seen clearly how the performance of all scenarios depends strongly on the existence of end-market for the recovered RDF and SRF. Especially scenarios 3 and 4 generate net GHG emissions and thus the treatment of residual MSW in these scenarios, offers no benefit, at least on GHG emission savings. Therefore, in the event that a SRF market does not exist, then probably further aerobic treatment for RDF and SRF will be necessary in order to reduce its biodegradable content, since they will be disposed in landfills. On the other hand Scenarios 1, 2 and 5 can provide GHG emission savings as they incorporate WTE and MBT(AD) which recover electrical energy for which the demand is constant.

3.8. Conclusions The present study assessed the GHG emission impact of various treatment technologies

for the residual MSW in Attica Region in the context of five different waste management scenarios that were compiled according to information from Attica’s Regional Plan. The


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study has shown that all scenarios under assessment could save GHG emissions provided that there is an end market for the recovered RDF and SRF.

Figure 4.GHG emissions (Gg CO2-eq) for the five scenarios with no market for SRF/RDF.

In this case, co-incineration in cement of SRF from MBT(BioD) mainly and RDF from MBT(C), MBT(AD) and MT can generate significant emission savings. However, if these fuels are not utilized and disposed in landfills, then CH4 emissions could be generated from the biodegradation of their organic fraction. Therefore it is proposed that decision makers and planners evaluate the perspectives of these fuels in the Hellenic market and decide on which technology is more beneficial for the treatment of residual MSW in Attica. A superficial planning could result in large amounts of waste derived fuels disposed in landfills, that would have adverse GHG emission impact and moreover it would increase the cost of waste management in Attica due to additional disposal costs for RDF and SRF. In this case MBT(AD) or WTE plants are considered better options, as it has been shown in the sensitivity analysis, where Scenario 2 which incorporates a MBT(AD) plant and a WtE facility, performs best. In general, the conclusions of this study could support an integrated assessment that would assess additional environmental impacts of MSW treatment technologies and at the same time evaluate their perspectives in the Hellenic market, supporting like this the decisions makers. It should be also commented here that waste policy and planning in Greece for the moment does not promote waste minimization measures neither poses high recycling targets and instead promotes technologies and plants of large capacity that will treat mixed residual MSW. Thus, the potentials of waste minimization measures such as home composting and PAYT schemes in conjunction with new waste treatment plants should be pursued as well.


4. A REVIEW OF THE STATUS AND BENEFITS OF WTE IN THE US As everywhere in the world, the generation of MSW in the US has grown steadily. A

survey that is being carried out every two years by Columbia University and BioCycle journal has lately showed that the generation of MSW increased from 369.4 million (short) t in 2002 to 387.9 million t in 2004, an increment corresponding at a rate of 2.5% per year. Landfilling accounted for 248.6 million t or 64% of the MSW generated, followed by recycling (28.5%), and WTE in MBIs (7.4%) (Table 4.1). Most of the recycling is done in coastal states and most of the WTE facilities are on the East coast, corresponding to the 66% of the total WTE capacity in the US (Table 4.2).

Table 4.1. MSW generation and disposal in 2002 and in 2004 in the US.

generated recycled or composted WTE landfilled 2004, million t 387.9 110.4 28.9 248.6 2004, percent 100% 28.5% 7.4% 64.1% 2002, million t 369.4 98.6 28.4 236.8 2002, percent 100% 26.7% 7.7% 65.6%

Table 4.2. Major users of WTE in the US.

State Number of plants Capacity (t/day) Connecticut 6 6,500 New York 10 11,100 New Jersey 5 6,200 Pennsylvania 6 8,400 Virginia 6 8,300 Florida 13 19,300 Total 53 69,600

WTE power plants are in operation in 25 states. They are fuelled by 29 million t of MSW

and have a generating capacity of 2700 MW of electricity. They also recover about 0.7 million t of ferrous and non-ferrous metals. There are two main categories of WTE plants:

− MBI plants, where MSW are fed as collected into large furnaces. − RDF plants, where MSW are first shredded into small pieces and most of the metals

are recovered before combustion (Table 4.3).

Table 4.3. Operating US WTE plants.

Technology Number of plants Capacity, t/day Capacity, million t/year MBI 65 71,354 22.1 RDF 15 20,020 6.3

Thermal treatment facilities built in the 21st century have been based mostly on the grate

combustion of ‘as received’ MSW. US facilities follow this type of treatment and, in industrial scale, the dominant WTE technology is grate technology, because of its simplicity


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and relatively low capital cost. These figures are given also above in Table 3.3 where it is shown that the majority of the facilities (80 of the 87 total) are grate combustion (i.e. either MBI or RDF), while these facilities represent over 80% of the total capacity of WTE in the US. Three dominant technologies - those developed by Martin, Von Roll, Keppel-Seghers – are grate technologies. In terms of novel technologies, gasification (JFE), direct smelting (JFE, Nippon Steel), fluidized bed (Ebara) and circulating fluidized bed (Zhejiang University) are in operation around the world while some of them are under investigation and discussion for possible implementation in the WTE facilities that will be constructed in the US. One of the most successful US facilities is the RDF-type process of the SEMASS facility in Rochester, Massachusetts, developed by Energy Answers Corp. and now operated by American Ref-Fuel, has a capacity of 0.9 million t/year. This facility was considered to be among the 10 finalists for the Waste-To-Energy Research and Technology Council 2006 Industrial Award; thus to be among the best in the world on the basis of energy recovery in terms of kWh of electricity plus kWh of heat recovered per t of MSW, and as the percentage of thermal energy input in the MSW feed, level of emissions achieved, optimal resource recovery and beneficial use of WTE ash, the aesthetic appearance of the facility and the acceptance of the facility by the host community.

4.1. Benefits from WTE in the US

4.1.1. Energy Production and Reduction Of GHG According to actual operating data collected by the US WTE industry, on the average,

combusting one t of MSW in a modern WTE power plant generates a net of 550 kilowatt-hours of electricity, thus avoiding mining a quarter of a ton of coal or importing one barrel of oil. WTE is the only alternative to landfilling of non-recyclable wastes, where the decomposing MSW generates carbon dioxide and methane, a potent greenhouse gas, at least 40% of which escapes to the atmosphere even in the modern sanitary landfills that are provided with gas collection network and biogas utilization engines or turbines. Taking into account the electricity generated and the methane emissions avoided has led several independent studies to conclude that WTE reduces greenhouse gas emissions by an estimated 1.1-1.3 t of carbon dioxide per ton of MSW combusted rather than landfilled. Therefore, in addition to the energy benefits, the combustion of MSW in WTE facilities reduces US GHG emissions by about 40 million t of carbon dioxide. In Table 4.4, air emissions of WTE and fossil-fuelled power plants are compared.

Table 4.4. WTE and fossil-fuel power plants: Comparison of air emissions.

Fuel Air emissions (kg/MWh) Carbon dioxide Sulphur dioxide Nitrogen oxides

MSW 379.66 0.36 2.45 Coal 1020.13 5.90 2.72 Oil 758.41 5.44 1.81 Natural Gas 514.83 0.04 0.77


4.1.2. Source of Renewable Energy At this time, the U.S. DOE categorizes WTE as one type of biomass. The term "biomass"

means any plant-or animal-derived organic matter available on a renewable basis, including dedicated energy crops and trees, agricultural food and feed crops, agricultural crop wastes and residues, wood wastes and residues, aquatic plants, animal wastes, municipal wastes, and other waste materials. Even if one uses a more stringent definition of the term "renewable", one that includes only material from non-fossil sources, about 64% of the US MSW, after material recovery for recycling plus composting, are derived from renewable sources. This fraction of MSW can be used as clean, sustainable and arguably renewable fuel for the production of electricity and steam. The remaining non-renewable portion, however, has to be either separated or accepted as part of the fuel.

Table 4.5. Generation of renewable energy in the US in 2002, excluding hydropower.

Energy source kWh x109 generated % of renewable energy Geothermal 13.52 28.0% WTE 13.50 28.0% Landfill gas 6.65 13.8% Wood/biomass 8.37 17.4% Solar thermal 0.87 1.8% Solar photovoltaic 0.01 0.0% Wind 5.3 11.0% Total 48.22 100.0%

Table 4.6. Concentration of combustible materials in US MSW.

Biomass combustibles % Petrochemical combustibles % Paper/cardboard 38.6 Plastics 9.9 Wood 5.3 Rubber 1.5 Cotton/wool 1.9 Fabrics 1.9 Leather 1.5 Yard trimmings 12.8 Food wastes 10.1 Total biomass content 70.2% Total petrochemical content 14.3 %

In 2002, the US WTE facilities generated a net of 13.5x109 kWh of electricity, greater

than all other renewable sources of energy, with the exception of hydroelectric and geothermal power (Table 4.5). For comparison, wind power amounted to 5.3x109 kWh and solar energy to only 0.87x109 kWh. The combustible materials in MSW consist of 82% biomass (paper, food and yard wastes plus half of rubber, etc.) and 18% petrochemical wastes. Therefore, MSW is a renewable source of energy and it is included by the US DOE in the biomass fuel category of renewable energy sources.

4.1.3. Recycling and WTE

According to the US EPA, the current MSW recycling rate in the US is 28%. By comparison, 57% of the 98 WTE communities achieved a higher recycling rate of 33%. Ten years ago, WTE communities had an average recycling rate of 21% versus the national rate of


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17%. Among operating US WTE plants, 77% have onsite ferrous metal recovery programs. These facilities recover more than 773,000 tons of ferrous annually. Most of these metals are recovered at WTE MBIs from the bottom ash after combustion. In addition, 43% of the operating facilities recover other materials on-site for recycling (e.g., nonferrous metals, plastics, glass, white goods, and WTE ash that is used for road construction outside landfills); over 854,000 tons of these recyclables are recovered annually. Combining all onsite WTE recycling, 82% of the US facilities recycle nearly 1,627,000 t. In fact, all communities with operating WTE plants are linked to offsite recycling programs. The recycling operations associated with these programs may be public or private, residential or commercial. The programs may also operate outside of the community in which the plant is specifically located.

4.1.4. Saving of Land

With proper maintenance, WTE plants, can last well over thirty years. Considering that WTE plants do not require more land than the initial one, unless they are expanded to process more MSW, WTE plants do not have a continuing cost in land. Furthermore, the required land is significantly smaller than for the land used for landfilling the same quantity of MSW; thus the initial capital for land is very small. As an example, with landscaping and auxiliary buildings, a WTE plant processing one million t per year requires less then 100,000 m2 of land. In comparison, the landfilling of thirty million t of MSW would require an estimated 3,000,000 m2. Furthermore, a new plant could be built on the site of the old existing WTE plant, thus reducing in this way the capital cost for land in the new facility to zero. On the other hand, the landfill site cannot be used for anything else, ever, and new greenfields must be converted to landfills.

4.2. WTE Emissions and Public Health Issues In the distant past, many US cities had thousands of residential incinerators in the city

without any air pollution controls. For example, at one time, New York City had an estimated eighteen thousand residential incinerators and thirty two municipal incinerators. The environmental impacts can still be detected in deep lying cores of the Central Park soil. Understandably, this has left a bad image of incineration in New York City that persists to this day. The result is that the City transports most of its MSW to distant landfills in other states. Yet, the adjacent New Jersey and Long Island Sound communities depend largely on WTE and most of the Manhattan MSW is combusted in the Essex County WTE plant.

At this time, there are over 1500 incinerators of all types in the U.S. but only 87 WTE plants as mentioned above already. In the past, when the effects of emissions on health and the environment were not well understood, all high-temperature processes, including metal smelting, cement production, coal-fired power plants and incinerators were the sources of enormous emissions to the atmosphere. In particular, incinerators were the major sources of toxic organic compounds (called dioxins and furans) and mercury. However, in the last fifteen years and at the cost of about one billion dollars, the 87 WTE facilities operating in the U.S. have implemented APC systems that have led US EPA to recognize them publicly as a source of power “with less environmental impact than almost any other source of electricity”.

WTE facilities were subject to new Clean Air Act rules in 1995. In 1995, the US EPA


adopted new emissions standards for WTE facilities pursuant to the Clean Air Act. Their MACT regulations dictated that WTE facilities with large units (i.e. >250 t per day) should comply with new Clean Air Act standards by December 19, 2000. Small unit facilities (i.e. 35 to 250 t per day) represent only 5% of the US WTE capacity and by 2005 also met similar MACT rules. MACT includes dry scrubbers, fabric filter bag houses, activated carbon injection, selective non-catalytic reduction of NOx and other measures that were implemented at an estimated cost of over one billion dollars. WTE facilities now represent less than 1% of the US emissions of dioxins and mercury, as further discussed below.

4.2.1. Decrease in WTE Dioxin Emissions

The toxic effects of dioxins and furans were not realized, both in the US and abroad, untill the late eighties. Thanks to the implementation of MACT regulations, the “toxic equivalent” (TEQ) dioxin emissions of US WTE plants have decreased since 1987 by a factor of 1,000 to a total of less than 12 grams TEQ per year. In comparison, the major source of dioxin emissions now, as reported by EPA, is backyard trash burning that emits close to 600 grams annually. Table 4.7 shows the change in major sources of dioxins/furans air emissions in the US over the years.

Table 4.7. Sources of dioxin/furan air emissions in the US, in grams TEQ.

Year Source 1987 1995 2002

WTE facilities 8,877 1,250 12 Coal-fired power plants 51 60 60 Medical waste Incineration 2,590 488 7 Barrel backyard burning 604 628 628 Total US 13,998 3,225 1,106

4.2.2. Mercury Emissions

The use of mercury in US processes and products reached a high of 3,000 tons per year in the seventies. It decreased to less than 400 tons by 2002, due to the phasing out of most applications of this metal, as mandated by US EPA. For example, mercury activated switches and thermostats have been substituted and the mercury content of fluorescent lamps has been reduced substantially. Furthermore, many communities have put in place strong recycling programs that keep older mercury-containing products out of the MSW sent to WTE facilities. This trend, plus the implementation of the MACT regulations have decreased the mercury emissions of the WTE facilities from 89 tons of mercury in 1989 to less than one ton by 2008. By now the major sources of mercury in the atmosphere are the global coal-fired power plants. Table 4.8 represents the emissions from US WTE facilities reduction between the years 1990 and 2000, while Table 4.9 represents the average emission of 87 U.S. WTE facilities, the EPA standard requirements and the respective percentage considering the EPA limits.


27

4.3. Conclusions WTE facilities for MSW management serve about 30 million people in the US.

According to the US experience, the environmental impact of MSW management was reduced (lower GHG emissions, energy production, land saving, materials recovery, etc). Furthermore, emissions of toxic and dangerous substances like mercury and dioxins have been significantly reduced, thus protecting public health. Evaluating further these results, it can be seen that the WTE facilities have quite lower emissions compared to electricity production facilities from fossil fuels (except Natural Gas), further reducing GHG emissions from landfills while at the same time decreasing the dependency for power production on fossil fuels. In addition, 80% of combustible biomass included in MSW can be considered as renewable fuel, a fact that is already acknowledged by US DOE which categorizes MSW as biomass. One more significant parameter that was observed is that US communities that use WTE have a 17.8% higher recycling percentage than the US EPA national average. The later seems to counter the usual argument of environmental groups that building of new WTEs will result in lower recycling rates.

Table 4.8. Emissions from US WTE facilities.

Pollutant 1990 2000 Reduction (%) Dioxins/furans, grams TEQ* 4,260 g 12 g 99.7 Mercury 45.2 t 2.2 t 95.1 Cadmium 4.75 t 0.33 t 93.0 Lead 52.1 t 4.76 t 90.9 Hydrochloric acid 46,900 t 2,672 t 94.3 Sulfur dioxide 30,700 t 4,076 t 86.7 Particulate matter 6,930 t 707 t 89.8 * Toxic equivalent (sum of substance amounts multiplied by toxicity equivalency factors)

Table 4.9. Average emissions of 87 US WTE facilities.

Pollutant Average emission

US EPA standard

Average emission (as % of US EPA standard) Unit

Dioxin/furan, TEQ basis 0.05 0.26 19.2% ng/dscm Particulate matter 4 24 16.7% mg/dscm SO2 6 30 20% ppmv NOx 170 180 94.4% ppmv HCl 10 25 40% ppmv Mercury 0.01 0.08 12.5% mg/dscm Cadmium 0.001 0.020 5% mg/dscm Lead 0.02 0.20 10% mg/dscm CO 33 100 33.3% ppmv


5. CONCLUDING REMARKS MSW management is currently a major issue worldwide and will also continue to be in

the foreseeable future. Besides the numerous developing countries, many other countries that are not considered generally as developing ones, also find themselves also among rapid developments and challenges in their MSW management system. In this frame, WTE as a major element of the MSW management hierarchy after recycling and before disposal, has been well tested in many developed countries and in a manifold of technological variations, whereas it is continuously being developed and improved. However, in many transitional MSW management systems, also in developed countries, significant peculiarities of a complex socioeconomic nature are still prevailing which often raise barriers and problems in the balanced integration of waste-to-energy in an overall sustainable waste management hierarchy. This chapter has presented 3 cases of such developing systems from England, Greece and the US, where the penetration and integration of WTE is still relatively limited or at its infancy, but where extensive assessments are being currently performed and related large-scale projects put under way, due to mounting pressures and closing deadlines from the pertaining legislation.

ABBREVIATIONS

AD: Anaerobic Digestion APC: Air Pollution Control BioD: Bio-Drying CHP: Combined Heat and Power DOC : Degradable Organic Carbon DOE: Department of Energy EF: Emission Factor EPA: Environmental Protection Agency FBI: Fluidised Bed Incinerator GEMIS: Global Emission Model for Integrated Systems GHG: Greenhouse Gas IPCC: Intergovernmental Panel for Climate Change IWMC: Integrated Waste Management Center MACT: Maximum Available Control Technology MBI: Mass-Burn Incineration MBT: Mechanical Biological Treatment MBT(C): MBT with composting MBT(AD): MBT with AD MBT(BioD): MBT with bio-drying MCF: Methane Correction Factor MHT: Mechanical Heat Treatment MRF: Material Recovery Facility MSW: Municipal Solid Waste MT: Mechanical Treatment NCV: Net Calorific Value PAYT: Pay As You Throw RDF: Refuse Derived Fuel SRF: Solid Recovered Fuel


29

TEQ: Toxic Equivalent WTE: Waste-to-Energy

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Chapter 2

MUNICIPAL SOLID WASTE: CHARACTER AND COMPOSITION

Libuše Benešová*, Markéta Doležalová, Petra Hnaťuková and Bohumil Černík

ABSTRACT

This chapter analyzes municipal solid waste (MSW), its definition, brief history, and management. Life Cycle Assessment (LCA), which evaluates environmental impacts of MSW, is also referred. MSW is mentioned in terms of its characteristic as well as a method of collection, transport, recycling, treatment and disposal. The new methodology of sampling and analyses of MSW is also mentioned because the knowledge of the composition allows decision making based on what kind of handling will be optimal for wastes and the environment.

MSW management is one of the major environmental problem not only in EU countries but all over the world.

1. INTRODUCTION The production of MSW is as old as mankind itself. Every civilization, from the oldest to

the most modern economic society, has had to deal with MSW. Of course the style of handling is different comparing the earliest civilizations to the 21st century. Not only is the amount of wastes greater, but the composition of wastes is completely different. The industrial revolution between 1750 and 1850 led many people to move from rural areas to cities. The concentration of the inhabitants of towns and cities caused an increase in waste amount. These wastes generated contained a range of materials such a glass, food residue and human waste. An additional problem was the attraction of MSW for flies, rats and other vermin which can cause disease transfer. These conditions were very dangerous, and caused an actual threat to human health and the environment. * Institute for Environmental Studies, Faculty of Science, Charles University, Prague, [email protected]

Libuše Benešová, Markéta Doležalová, Petra Hnaťuková et al. 34

Today, the composition and amount of MSW is extremely variable as a consequence of seasonal, lifestyle, demographic, geographic, and legislative factors. This variability makes defining and measuring the composition of waste more difficult and at the same time more essential.

Municipal solid waste (MSW), also called urban solid waste, is a waste type that includes predominantly household waste (domestic waste), with sometimes the addition of commercial wastes, collected by a municipality within a given area. They are in either solid or semisolid form and generally exclude industrial hazardous wastes. The term residual waste relates to waste left over from household sources containing materials that have not been separated out or sent for reprocessing.

Waste management is the collection, transport, processing, recycling or disposal, and monitoring of waste materials (Tchobanoglous, 1993). The term usually relates to materials produced by human activities, and is generally undertaken to reduce their effect on health, the environment or aesthetics. Waste management is also carried out to recover resources. Waste management can involve solid, liquid or gaseous substances, with different methods and fields of expertise for each.

Effective waste management through MSW composition studies is important for numerous reasons, including the need to estimate the potential of material recovery, to identify sources of component generation, to facilitate the design of processing equipment, to estimate physical, chemical, and thermal properties of waste, and to maintain compliance with national laws and European directives.

2. MSW DEFINITION The definition of MSW is very important, because there can be great variation in the

composition of natural waste. The material is heterogenous and it is difficult to describe, define and classify.

In many cases, MSW is a mixture of different waste types and often is on the border between two categories. Therefore, the MSW must have a strict and legal definition. For EU countries there is definition given by European Community law. But this is complicated by the fact that each country and each administration derives its own definition from the EC Framework Directive (75/442/EEC as amended by 91/156/EEC).

The Czech Republic uses the definition given by the Act of waste no. 185/2001Coll. where MSW is defined as “all wastes generated on the territory of the municipality, that originate in the activities of natural persons, with the exception of wastes formed on the premises of legal persons or natural persons authorized to operate business”.

In recent years, there is support in the CR for an MSW concept including commercial wastes within the municipality area. Basic items are wastes from households (including bulky waste), services, and the unproductive assets of enterprise subjects (waste group 20 EWC).

Examples of other definitions of MSW, taken from various web sites, are: • Municipal solid waste (MSW), also called urban solid waste, is a waste type that

includes predominantly household waste (domestic waste) with sometimes the addition of commercial wastes collected by a municipality within a given area. They

Municipal Solid Waste: Character and Composition

35

are in either solid or semisolid form and generally exclude industrial hazardous wastes. The term residual waste relates to waste left from household sources containing materials that have not been separated out or sent for reprocessing (www. wikipedia.uk).

• The total waste generated by residents, businesses, and institutions (www.opala.org/solid_waste/glossary/Glossary.html).

• Solid waste originating from homes, industries, businesses, demolition, land clearing, and construction (weblife.org/humanure/glossary.html

• MSW is household waste (and some commercial waste) that is set aside for kerbside collection or delivered to a waste facility

• (www.plymouth.gov.uk/homepage/environmentandplanning/rubbishandrecycling/swdwp/swdwpfaqs/swdwpglossary.htm).

• Waste material that is collected from homes and businesses. Waste materials from industrial processes that are not considered safe to place into landfills are not allowed to become MSW, and recycled materials are not included in MSW. MSW is referred to in common parlance as garbage

• (www.alamedapt.com/electricity). • Waste generated in households, commercial establishments, institutions, and

businesses. MSW includes used paper, discarded cans and bottles, food scraps, yard trimmings, and other items. Industrial process wastes, agricultural wastes, mining wastes, and sewage sludge are not MSW

• (www.purdue.edu/envirosoft/housewaste/src/glossary1.htm). In Europe, wastes are defined by the European Waste Catalogue (EWC) Codes. EWC

Codes are 6 digits long, with the first two digits defining the over-arching category of waste, the next two defining the sub-category, and the last two defining the precise waste stream. Municipal Solid Waste comes under the "20" codes, for example: "20 01 02”corresponds to Municipal Solid Waste (20), components from separated collection (01) glass (02). Similarly 20 02 01 means Municipal Solid Waste (20), waste from garden and parks (02), biodegradable material (01).

3. A BRIEF HISTORY OF MSW The study of waste through history brought many insights into civilizations, and has

produced a relatively new research sphere – garbology. In the timeline of waste history, the problem of wastes was significantly acerbated when

people began to move to industrial towns and cities from rural areas. Prehistoric people discharged their waste in pits, because these wastes were mostly composed of only hunting and food preparation items. Due to the composition of wastes and the very low human population, there were no problems with contamination of water or soil (Pittchel, 2005). In early pre-industrial times, waste was mainly composed of ash from fires, wood, bones, bodies and vegetable waste. It was disposed of in the ground where it acted as compost and helped to improve the soil (Wilson, 1977). Ancient rubbish dumps excavated in archaeological digs reveal only tiny amounts of ash, broken tools and pottery. Everything that could be was


repaired and reused. However, the transition from nomadic hunter-gatherer to farmer meant that waste could no longer be left behind, and it soon became a growing problem.

In Mesopotamian and Egyptian civilizations the effect of solid waste became significant, and was connected with the gathering together of people. The first dumps were established, and they were situated away from settlements.

Minoan civilization had more advanced technology in dumping, and periodically covered waste with layers of soil. This was the first precaution for human health (Wilson, 1977). In capital of ancient Crete, there were not only sewage drains but also effective composting in pits. The first recorded regulations concerning the handling of MSW established during the Minoan civilization (Tammemagi, 1999).

There was great progress in MSW handling in Greek municipalities. During the 5th century B. C., dumps with controlled operations were established. Residents and every household were responsible for collecting and transport of their wastes beyond the city walls.

In ancient Rome, waste was dumped into the Tiber River or into open pits. This type of waste discharge led to health problems, and Rome was the victim of plagues in 23 B.C. and in 65, 79 and 162 A.D. (Vesilind, et al. 2002).We have evidence that older civilization reused and recycled wastes. Until the Industrial Revolution, when materials became more available than labor, reuse and recycling was commonplace. Nearly 4000 years ago, there was a recovery and reuse system of bronze scrap in operation in Europe, and there is evidence that composting was carried out in China. Traditionally, recovered materials have included leather, feathers and down, and textiles. Recycling included feeding vegetable wastes to livestock and using green waste as fertiliser. Pigs were often used as an efficient method for disposing of municipal waste. Timber was often salvaged and reused in construction and ship-building. Materials such as gold have always been melted down and re-cast numerous times. Later recovery activities included scrap metal, paper and non-ferrous metals.

When the Roman Empire ended, the „Dark Ages“ arose, with a significant loss of technical knowledge and the science of basic hygiene (Kelly, 1973). At that time, there was no organized method of waste disposal, and mankind mostly forgot these practices. The routine procedure was to simply dump wastes, including fecal matter, directly out of one’s windows.

In Prague in 14 century there were streets full of waste and according to the statement of Prague town councillor, vagabonds could hide in the heaps of wastes. Regular street cleaning in Prague begun in 1340. In 1470 there was a town order that nobody could empty chamber pots in the street, under a fine of 5 rap. The first really important attempt to clean Prague streets was done in 1621 by Karl von Lichenstein who assigned a town inspector who was responsible for cleaning. From History of Prague sewers- internet

The situation in the medieval period was terrible, with all manner of wastes in front of

houses. In summer there were intolerable bad smells, and in winter animals (like hens and pigs) were a typical phenomenon near large cities.

Another common practice was to discharge waste directly into surface waters. The plague of 1347 may have been precipitated by waste into the Thames River (Alexander, 1993).

The waste problems in Western Europe culminated at the end of the 15th and beginning of the 16th centuries.


37

The greatest cities such as London and Paris tried to solve these problems – they initiated street cleaning (paid for by public funds), and introduced the first basic methods of common hygiene.

The accumulation of refuse in the streets reached the point that in 1348 Phillipe VI de Valois passed an ordinance requiring the citizens to sweep in front of their doors and to transport their garbage to dumps or risk fines and imprisonment. He established the first corp of sanitation workers to clean the streets. Even with ordinances issued every few years, these brought little relief and were difficult to enforce. Garbage piled up in the streets, making some completely inaccessible. Finally in desperation, the King made Nobility set an example, and people began to follow the orders, (but now they dumped their waste on public property and out of the way places). From Parisian Sanitation from 1200-1789 - internet

The Great Fire of London in 1666 had some cleaning effects on the city environs, and

complaints about refuse in the streets eased to some extent (Wilson, 1977). The Industrial Revolution starting in the 18th century had the biggest influence on waste

handling. This was due to the increase in population and the massive migration of people to industrial towns and cities from rural areas during the 18th century. There was a consequent increase in both industrial and domestic wastes, posing threats to human health and the environment. And thus the subject of “recycling“ began to be used in our speech.

Henry Mayhew distinguished five categories of workers within the then largely in formal waste management and recycling collection in London: Street buyers – they bought any repairable items. They survived as “rag and bone men” until well after the Second World War. Street finders - the bone grubbers and rag gatherers were very much “on the bottom of the heap” eking out a miserable income from the dregs overlooked by others. More prosperous then were the more specialised finders, who focused on ‘pure’ (dog-dung, in demand for leather tanning), cigar-ends and old wood. Sewer and River finders - Included dredger-men, mud-larks and sewer-hunters. The mud-larks were generally children, who scavenged along the Thames beaches at low tide, before the embankments were built. Paid labourers - dust-men were employed by dust contractors, and scavengers (street sweepers) by their sub-contractors (as street cleaning was included in the dust contracts). ‘Night-men’ also removed night-soil (human sewage) that had a ready market as a fertiliser. Recycling shops - a huge variety of shops bought and sold reusable goods and recyclable materials. The most comprehensive were the ‘rag-and-bottle’ and ‘marine store’ shops, which bought direct from the public, from the street buyers and from the various ‘finders.’ The Rowlett’s rag-store in Lambeth (shown here) had been relatively prosperous, until they lost their entire stock of rags and waste paper in a tidal flood around 1870, and had to sell tons for manure. From Henry Mayhew (1862) ‘London Labour and the London Poor’, Volume 2 Griffin, Bohn and Company. - internet

In 19th and 20th centuries MSW management changed significantly. Many new

technologies were used, like controlled land disposal, incineration, composting or some combination of these basic methods. In the beginning of the 20th century, the most common method of MSW disposal was dumping.


In England and Germany, a very effective system for MSW disposal and stabilization was developed – incineration. The advantage of this method is not only volume reduction and stabilization, but energy production. The first municipal solid waste incineration system operated in England – Nottingham in 1874 (Murphy, 1993). After a cholera epidemic in Hamburg, the city decided to operate an incinerator designed with the cooperation of English engineers.

In the US the first incinerator was installed in 1885 in Allegheny, PA, but after 1910 incineration was widespread all over the US.

Incineration from a stationary source became a significant method of MSW disposal, especially when Great Britain and Germany developed technologies to recovery energy from incinerators.

Using dumps as a method of MSW disposal was a topic of discussion in 1900, as it still is today.

Land disposal or landfilling is still the most common method of MSW disposal in many countries. Numerous modifications have been made in the form of sanitary landfills – caps constructed of clay or impermeable synthetic materials, and subsurface and surface collection systems for capturing gas and leachates (Filip, at al., 2003; Bilitewski, at al., 2000). In spite of these technical advantages, there is continuing concern about groundwater contamination and methane emission.

Similarly, composting is a method which has been used for ages, and today it is most common especially in developed countries. In EU countries, composting is a supported method, but there are problems associated with product quality and the ability to sell the product.

The first separation and recycling programs were documented in Japan and Germany. (Alexander, 1993).

4. WASTE MANAGEMENT Waste management involves all those activities which are concerned with waste

handling, from planning to discharge. MSW management can be managed though a number of activities – waste prevention, recycling, composting, and so forth. Some of the most general, widely-used concepts include:

• Waste hierarchy • Extended producer responsibility • Polluter pays principle The National Waste strategy is a requirement for all member states of the EU, given by

the EC Directive 91/56/EEC. In particular, the Strategy must identify the type, quantity and origin of waste to be recovered or disposed of. In every EU country, the Directive requirement has been incorporated into nation laws. In the CR this was the Act on Waste No.185/2001 Coll., for Great Britain it was Environmet Act 1995, and likewise for all members of EU.


39

All EU members have attempted to focus the National Waste Strategy on the idea of sustainable development, in line with the 1992 United Nations Rio Conference on Environment and Development (the Earth Summit). The main requirement of the Conference was that society makes decision with proper regard to their environmental impact.

The treatment and disposal of waste is therefore one of the central themes of sustainable development.

4.1. Waste Hierarchy The EC strategy has been developed into the concept of “hierarchy waste management”:

Waste hierarchy refers to the "3 Rs" Reduce, Re-use and Recovery (Wiliams, 1998): 1. Reduction - the first in the hierarchy shows that waste production should be reduced.

It is realized by the development of clean technology and by the use of such processes which require less material and produce less waste during manufacture.

2. Re-use – the second step in hierarchy. There are many examples of suitable re-use technologies – tyre re-treading, glass bottles (e.g. from beer and milk). Re-use is not profitable in every case, but environmental aspects can outweigh the benefits.

3. Recovery - the last step in the hierarchy has a number different types: • Materials recycling – using waste material for producing a marketable product. A

typical example is the recovering of glass, because scrap glass can be ground and used for new glass production. In the CR, recycling of PET material is very high, and PET is re-used for many products, e.g. load-dependent carpets, car parts (steering wheel, dash-board), fillings for sport clothing. These examples show very suitable process of changing wastes to products, often with energy savings in comparison


with obtaining raw materials. But the recycling process assumes that there is a market for recycled materials. Otherwise, waste is produced.

• Energy recovery - this technology produces energy by incineration of wastes or by combustion of landfill gas. The energy potential of MSW is high, and has recently been increasing. The problem is that the incinerator installations require high initial capital costs. An additional problem is the necessity to install sophisticated flue gas cleaning equipment.

• Composting - uses the decomposition of the organic waste fraction to produce a stable product similar to fertilizer. But there is a problem with the pollution of raw material by heavy metals and toxic organic compounds. In the CR and other EU countries, there are very strict requirements on the quality of compost; all chemical properties concerning heavy metals and organic compounds are limited.

• Disposal - the last possibility of how to get rid of waste. The most common method is landfilling, which is the predominant method of waste disposal in Europe and North America. The problem is production of methane and therefore the necessity of gas emission controls to prevent potential air pollution.

4.2. Extended Producer Responsibility Extended Producer Responsibility (EPR) is a strategy designed to promote the integration

of all costs associated with products throughout their life cycle (including end-of-life disposal costs) into the market price of the product. Extended producer responsibility is meant to impose accountability over the entire lifecycle of products and packaging introduced to the market.

This means that firms which manufacture, import and/or sell products are required to be responsible for products after their useful life as well as during manufacture.

4.3. Polluter Pays Principle The Polluter Pays Principle is a principle where the polluting party pays for the impact

caused to the environment. With respect to waste management, this generally refers to the requirement for a waste generator to pay for the appropriate disposal of waste.

4.4. Integrated Waste Management The principles of Integrated Waste Management are defined in terms of the integration of

six functional elements (Tchobanoglous, 1993).

4.4.1. Waste Generation Waste generation encompasses activities in which materials are identified as no longer

being of value and are either thrown away or gathered together for disposal.


41

This section identifies the sources of solid wastes, provides general information on quantities, and identifies the potential effect of MSW on daily life and the environment.

Over the past few decades, the generation, recycling and disposal of MSW have changed substantially. The amount of MSW generated in a country is related to the rate of urbanisation, the types and patterns of consumption, household revenue and lifestyle.

The quantity of MSW generated in the OECD area has risen since 1980 and exceeded 619 tonnes in 2006 (580kg per capita), (OECD Environmental Indicators).

4.4.2. Waste Characterization, Handling and Separation

Waste handling and separation involves those activities associated with the management of wastes until they are placed in storage containers for collection. Handling also encompasses the movement of loaded containers to the point of collection. Separation of waste components is an important step in the handling and storage of solid waste at the source.

The general purpose of waste characterization is to promote the sound management of solid waste (Dobson, at al., 2003)

Specially, characterization can determine the following: • The size, capacity and design of facilities to manage the waste, • The potential for recycling or composting portions of the waste stream, • The effectiveness of waste reduction programs, recycling programs and the amount

of other methods of material disposal, • Potential sources of environmental pollution in the waste (Liu, at al. 1996). In practice there are one or two fundamentals methods to characterize solid waste in use.

The first – called materials flows technology - is to collect and analyze data on the manufacture and sale of products that become solid waste after use.

The second method is the direct field study of the waste itself. This second method is more accurate, but it is dependent on the number of workers available and is relatively expensive. The results of the study Ministry of Environment of the Czech Republic according to the second methodology is shown in Fig. 1.

There have been significant changes in the composition of household waste over the last 100 years which can be traced back to fundamental social and economic shifts affecting the way we live our everyday lives, as is traced in the above chronology (Sokka, at al., 2007). The arising of waste types can be difficult to quantify, and it is only over the last few decades that there have been any real attempts at estimating the composition of household waste.

The characteristic of MSW in a small town in the CR and its composition are shown in Fig. 2. and Fig. 3.

Americans generate almost 208 million tons of solid waste each year. By the year 2000, that number is expected to increase by 20%. Today, each American generates about 1,95 kg of waste per day. As a country, America generates more garbage than any other country by far. (EPA, 2008)


0

1

2

3

4

5

6

Tonn

es x

106 / y

ear

2007 2010 2013 2015 2020

Year

MSW totalMSW from residental areaMSW householdMSW residental activitiesMSW business

Source: Benešová, L., Černík, B., Kotoulová, Z.and Vrbová, M. (2000). Intensification of collection,

transport and sorting of MSW. Technical Report of Research and Development Project of the Ministry of the Environment of the Czech Republic 720/2/00, Charles University in Prague, Faculty of Science (in Czech with English summery)

Figure 1. Production of MSW in the CR, reality and predictions

Photo by L. Benešová

Figure 2. Characteristic MSW in CR.


43

Benešová, L. (2006). Biodegradable waste, Proceedings of IInd. Conference, Náměšť nad Oslavou, CR,

ZERA –local non governmental organization (in Czech)

Figure 3. The composition of MSW in a small town in the CR ( 2007)

Separation of solid waste is one way to minimize the amount of wastes. All EU countries separate some portions of solid waste. Basic recyclable materials in the EU countries are paper, glass, and plastic. In some EU countries biodegradable waste, aluminium, PET bottles and drinking cartons are also separated. Bulky items are usually placed at a point of collection. Hazardous wastes as a part of household wastes must be segregated and collected at special points (e.g. from chemists, various shops and backyards).

Czechs recycle regularly using a system of designated bins located in municipalities across the country: color-coded for the recycling of plastics, paper, and glass. Drop-off points are easily accessible, and it’s not uncommon on any given day at almost any hour, to hear smashing glass being thrown into bins or to hear the crunching of plastic bottles. Statistics recently released by Eurostat revealed that Czechs are leaders when it comes to plastics: in 2006 they recycled 44 percent of PET beverage bottles and other packaging – which is 3 percent more than traditional leader Germany. But it’s not all good news. Most are aware that the country still needs to do much more – and point out while successful in some areas, in others they are clearly lagging “Any reason for sorting waste is a good one” is a slogan underlining a current TV campaign promoting recycling in the Czech Republic, and most Czechs would agree recycling is a necessity. Source: Official TV campaign in Czech television , 2008.

Character of MSW

Knowledge of the properties of waste, their amount, and physical-chemical composition, is very important information not only for future handling of waste, but for the prediction of the behaviour of wastes and their influence on the environment (Chang, 2008)

Waste sampling and analysis is the first step in the determination of the character of MSW.


Sources of waste from which samples can be selected include individual municipalities, individual waste collectors, waste generation sectors such a restaurants, family hotels, or apartment buildings (Li’ao, at al., 2009; Pehlken, 2003).

Every sampling is affected by some variability.

Seasonal variability The season of the year strongly affects the amount of generated waste and its

composition. But the changes during the week are significant as well. During the summer and fall months the amount of the biodegradable portion increases. The results of seasonal variations can be seen in Fig. 4.

Benešová, L., Černík, B. Kotoulová, Z., Hnaťuková, P. and Doležalová, M. (2008). Research of

Character of MSW and Optimization its Using. Technical Report of Research and Development Project of the Ministry of the Environment of the Czech Republic SP/2f1/132/08, CR, Charles University in Prague, Faculty of Science (in Czech with English summery)

Figure 4. Seasonal variability of the amount of biodegradable waste in MSW in country houses and central dwelling 2008 (expressed as %)

The variability in content of biodegradable waste for the whole Czech Republic is given in Table 1.

Table 1. The amount of biodegradable portion in wastes in the CR, 2008

Biodegradable wastes ( %) Central dwelling Country houses Food waste 22,1 9,7 Wood 0,1 0,4 Textile 5,6 2,0 Paper 21,4 5,5 Benešová, L., Černík, B. Kotoulová, Z., Hnaťuková, P. and Doležalová, M. (2008). Research of

Character of MSW and Optimization its Using. Technical Report of Research and Development Project of the Ministry of the Environment of the Czech Republic SP/2f1/132/08, CR, Charles University in Prague, Faculty of Science (in Czech with English summery)


45

The physical-chemical parameters change as well, especially according to the area of collected wastes. The character depends on the type of heating, because individual coal heating produces more ash in the winter months. In Table 2., the proportion of ash is expressed as the fraction smaller than 8 mm.

Table 2. Seasonal variations of ash amount in four types of building houses – CR

(expressed as %)

Type of dwelling/Month and year

Autumn Winter Spring Summer Average

2000

2008

2000

2008

2000

2008

2000

2008

2000

2008

Residential area (C) 2,9 2,3 3,0 3,0 2,9 2,6 1,6 1,2 2,6 2,2 Older district house-building (M) 2,9 0,8 3,1 2,1 3,9 2,2 3,0 1,2 3,2 1,6

Family houses and apartment villas (V) 12,2 8,7 24,6 19,3 18,7 12,6 10,3 9,7 16,5 12,6

Country house-building (P) 16,5 18,8 39,6 40,9 39,2 30,8 20,6 22,3 29,0 28,2

Benešová, L., Černík, B., Kotoulová, Z.and Vrbová, M. (2000). Intensification of collection, transport and sorting of MSW. Technical Report of Research and Development Project of the Ministry of the Environment of the Czech Republic 720/2/00, Charles University in Prague, Faculty of Science (in Czech with English summery)

Benešová, L., Černík, B. Kotoulová, Z., Hnaťuková, P. and Doležalová, M. (2008). Research of Character of MSW and Optimization its Using. Technical Report of Research and Development Project of the Ministry of the Environment of the Czech Republic SP/2f1/132/08, CR, Charles University in Prague, Faculty of Science (in Czech with English summery) Municipal solid waste processing and disposal systems must take into account the

changes of quantities and composition during the week or year. This data can be very important e.g. for recycling programs with composting systems, which should expect higher quantities of biodegradable products in the spring and summer.

Regional Variations

Various countries and various parts of every country produce different types and different amounts of waste.

Countries with a warm, moist climate during the most of the year will produce more biodegradable materials like grass and garden waste than countries with a long winter or with severe frost. On the other hand,”northern“ countries with local heating will produce more ash and inorganic wastes (Fig. 5. and 6.)

Another example of regional variation is the use of PET bottles for bottled water in post communist countries after political changes. In the CR, the amount of PET bottle wastes in the last 10 years has increased more than 25 times. (Benesova, at al., 2000 and 2008), see Figure 7.


Photo by P. Hnaťuková

Figure 5. MSW material in fraction under 8 mm in “C” dwelling


Figure 6. MSW material in fraction under 8 mm in “P” dwelling


47

Benešová, L., Černík, B. Kotoulová, Z. and Vrbová, M. (2005). Wastes from municipalities –

environmental and social problem of the future. Technical Report of Research and Development Project of the Ministry of the Environment of the Czech RepublicSL/7/102/05, CR, Charles University in Prague, Faculty of Science (in Czech with English summery)

Figure 7. The yield of separated PET bottles in the CR.

Household Variations Studies have found that the number of persons per household can very significantly alter

the waste production (Rhyner, 1976 and Benešová, 2004), see Table 3.

Table 3. Variability in quantities of MSW according to the size of household.

Number of person in household Quantity of MSW (kg/day) 1 1,65 2 1,1 3 0,96 4 0,74 6 0,62 8 0,61



Variations According to GDP and Political Situation Since the 1980s, household waste increases in the UK have risen from just under 400 kg

per person to over 500 kg per person per year. Such an increase can be attributed to economic growth, social change, and waste collection methods. The increase in waste has closely mirrored that of Gross Domestic Product (GDP), while the increase in single person households and increase in wheeled bin household waste collections have exacerbated the problem. Today in the UK it is estimated that each household throws away over a tonne of waste annually. In addition, for every tonne of products we buy, ten tonnes of resources are used to produce them. Around 70% of our household waste has the potential to be either recycled or composted. Despite the fact that the majority of the general public regards recycling as worthwhile, and that over 65% of households have access to kerbside collection recycling schemes, only 14.5% of dustbin contents are recycled or composted.

The results of the Research and Development Project of the Ministry of the Environment of the Czech Republic „Wastes from municipalities – environmental and social problem of the future“ (SL/7/102/05) ( Benešová and Černík, 2006) found an interesting correlation between the political situation, increasing GDP and waste generation rates. After 1990, waste management in the Czech Republic has gone through fundamental changes in the property ownership, technologies and economics. Completely newly defined objectives of the municipal waste management system were defined as liberalised „enterprise opportunities“ contrary to the former „services for the public“. Subsequently, a significant outside factor has been the successive harmonisation of legal regulations in relation to EU membership by the CR since 2004. That has brought requirements for technical equipment in the country, as well as demands on understanding the role of public administration, and that is within the context of creating communal, regional and national waste management plans. This proceeds under the terms of a dynamic increase in household and commercial waste generation as a consequence of improving economic conditions for Czech households and the whole society. Over the last 15 years, the public and enterprise attitudes toward responsibility for environmental issues including waste management have undergone quite fundamental changes.

4.4.3. Projects of the Ministry of the Environment of the Czech Republic

All previous and following results based on data from the Research and Development Project of the Ministry of the Environment of the Czech Republic in the years 2000, 2005 and 2008. This project was based on the new methodology of sampling and analyses of MSW. This methodology allows decision making based on what kind of handling will be optimal for wastes and the environment.

Methodology is focused on the following points.

1. The composition of mixed household waste is determined by the method of screening analysis and manual sorting in a pre-determined set of material groups,

2. In every pursued house-building, three screens of size 40, 20 and 8 mm are useduniformly,

3. The household waste collected in a pre-determined region which has 1.000 up to 3.000 inhabitants is analysed. The amount of waste collected matches a full haulagevehicle (4 to 8 t according to the type of vehicle and house-building). The mass and


49

volume of the waste collected is determined, 4. The average sample of weights 100-200 kg according to the type of house-building

and waste homogeneousity is taken for the screening analysis, 5. The oversize fraction above 40 mm is fully materially analysed. From fractions of

20-40 mm and 8-20 mm a homogenized sample of approximately 20 % mass istaken, which is materially analysed only after drying (and re-calculated according to the original sample). The fraction smaller than 8 mm is not materially sorted,

The mass is measured for all groups of grain sizes and materials. The volume is measured only in material groups of the fractions above 40 mm.

The example of using the methodology Because the character of MSW is changeable and depends on many aspects, an

observation was done in four types of building-houses. A description of these types is given in Table 4.

Table 4. Description of four types of building-houses

C (central)

Residential area with the centralised heat supply systems, without the possibility of any recovery of waste at source in the town above 100.000 inhabitants.

M (mixed, sundry)

Mostly older district house-building with various heating systems using upgraded fuels (gas, oil), or electricity if appropriate, central heating systems by means of housing and block boiler-rooms as well as individual (local) heating systems using solid fuels in the town above 20.000-30.000 inhabitants.

V (villa-houses)

District house-building of family houses and apartment villas with local heatingsystems by means of as well solid as upgraded fuels, and with most part of the incineration of combustible components and composting in the town with 20.000 - 50.000 inhabitants.

P (provincial, suburban, country)

Suburban and country house-building with the heating systems mostly by means of solid fuels, and with the possibility to incinerate, treat by compostingand feed a great deal of the waste.

Following Table 5. shows a list of the analysed material groups:

Table 5. List of the analysed material groups in the following 3 steps

1st sorting stage 2nd sorting stage 3rd sorting stage Paper/cardboard/carton Paper packaging

Prints Other paper

Carton/cardboard Combined packaging Other packaging Newspaper/journals, Periodical Books Other prints

Plastics*) Plastic packaging Other plastics

Films PET bottles Other packaging


Table 5 (Continued)

Glass Non-returnable glass packaging Returnable glass packaging Other glass

Clear glass Brown glass Green glass

Metals Metal packaging Others

Fe - metals Al - metals

Organics Kitchen waste Garden waste

Textile Mineral waste Hazardous waste Combustible waste Leather/rubber/cork/wood

Sanitary products

Fine waste Residue 20-40 mm Residue 8-20 mm Fraction smaller than 8 mm

*) Material sorting: PET, PVC, PE, PP, PS and others

This monitoring was carried out regularly once a month in every house-building for three years during the time period of 2000 – 2009. Laboratory analysis of the sorted MSW included both physical and chemical indicators. For all the fractions the physical indicators are continuously determined as follows:

• humidity (gravimetricaly partly at 65 °C and partly 105 °C) • combustible substance (gravimetricaly in a furnace at a temperature of 550 °C) • heat of combustion (total heating value) • humidity of particular commodities – paper, textile and biowaste - is determined

independently For the fraction under 8 mm and 20-8 mm the chemical indicators are also determined as follows:

• total chlorides, total nitrogen, total fluorides, total sulphur • selected heavy metals – As, Cd, Cr, Cu, Hg, Mo, Ni, Zn, Mn, Ti and Pb. (after

microwave decomposition by aqua regia, detected by AAS method) selected organic matters (PCB, PAH, …)

Following Table 6. is an example of data treatment of the field analysis in 2008 in a

central dwelling:

Table 6. The data treatment of the field analysis in 2008 in a central dwelling

General information Number of sample 11200801 Weight of MSW (kg) 6370

Analyses date 6.11. 2008 Volume of MSW (m3) 25,2

Locality Labska kotlina Volume weight (kg/m3) 252,778

Type of dwelling housing estate Weight of sample (kg) 238,420


51

Name of worker Kotoulova Cartage period once a week Volume of MSW (m3) 1,6450

Fraction Material group Material subgroup Weight (kg) % of total Volume

(m3) % of total

Volume weight (kg/m3)

>40 mm >40 mm

Paper/ Cardboard

In total 20,550 8,62% 0,2050 12,46% 100,244 Paper packaging 8,750 3,67% 0,1100 0,07 79,545 Cardboard 2,400 1,01% 0,0300 0,02 80,000 Composite packaging 2,450 1,03% 0,0400 0,02 61,250 Other packaging 3,900 1,64% 0,0400 0,02 97,500 Printed material 6,650 2,79% 0,0500 0,03 133,000 Newspaper and journals 3,350 1,41% 0,0300 0,02 111,667 Books 0,000 0,00% 0,0000 0,00 – Leaflets 3,300 1,38% 0,0200 0,01 165,000 Other paper 5,150 2,16% 0,0450 0,03 114,444

Plastic

In total 26,600 11,16% 0,8600 52,28% 30,930 Plastic packaging 24,200 10,15% 0,8100 49,24% 29,877 PET bottles pure 1,650 0,69% 0,0800 4,86% 20,625 PET bottles coloured 2,250 0,94% 0,0800 4,86% 28,125 Foil packaging 5,650 2,37% 0,1700 10,33% 33,235 Foil non packaging 7,800 3,27% 0,2400 14,59% 32,500 Other packaging 6,850 2,87% 0,2400 14,59% 28,542 Other plastic 2,400 1,01% 0,0500 3,04% 48,000

Glass

In total 15,750 6,61% 0,0400 2,43% 393,750 Glass packaging non reversible 12,750 5,35% 0,0350 2,13% 364,286 pure 9,350 3,92% 0,0300 1,82% 311,667 green 2,900 1,22% 0,0040 0,24% 725,000 brown 0,500 0,21% 0,0010 0,06% 500,000 Glass packaging reversible 1,900 0,80% 0,0040 0,24% 475,000 Other glass 1,100 0,46% 0,0010 0,06% 1 100,000

Metals

In total 5,450 2,29% 0,0200 1,22% 272,500 Metallic packaging 2,450 1,03% 0,0150 0,91% 163,333 Fe 2,050 0,86% 0,0100 0,61% 205,000 Al 0,400 0,17% 0,0050 0,30% 80,000 Other metals 3,000 1,26% 0,0050 0,30% 600,000

Biowaste In total 34,900 14,64% 0,0900 5,47% 387,778 household 28,500 11,95% 0,0800 4,86% 356,250 garden 6,400 2,68% 0,0100 0,61% 640,000

Textile In total 26,100 10,95% 0,1200 7,29% 217,500 natural 8,050 3,38% 0,0210 1,28% 383,333 mixture 18,050 7,57% 0,0990 6,02% 182,323

Mineral waste In total 8,250 3,46% 0,0080 0,49% 1 031,250 Hazardous waste In total 3,300 1,38% 0,0080 0,49% 412,500

Combustible waste

In total 54,800 22,98% 0,1600 9,73% 342,500 sanitary goods 43,800 18,37% 0,1300 7,90% 336,923 other 11,000 4,61% 0,0300 1,82% 366,667

Electro waste In total 4,550 1,91% 0,0070 0,43% 650,000 In total 200,250 83,99% 1,5180 92,28% 131,917

Fraction Material group Weight (kg) % of total Volume (m3) % of total

Volume weight(kg/m3)

20-40 mm

Plastic 0,400 0,17% 0,0020 0,12% 200,000 Glass 0,400 0,17% 0,0050 0,30% 80,000 Metals 0,200 0,08% 0,0250 1,52% 8,000 Mineral waste 0,050 0,02% 0,0000 0,00% – Hazardous waste 0,100 0,04% 0,0000 0,00% –

Rest 18,850 7,91% 0,0500 3,04% 377,000 In total 20,000 8,39% 0,0820 4,98% 243,902

Fraction Material group Weight (kg) % of total Volume (m3) % of total



Table 6 (Continued)

8-20 mm Plastic 0,050 0,02% 0,0000 0,00% – Glass 0,010 0,00% 0,0000 0,00% –

Metals 0,050 0,02% 0,0000 0,00% – Mineral waste 0,000 0,00% 0,0000 0,00% – Hazardous waste 0,010 0,00% 0,0000 0,00% –

Rest 11,300 4,74% 0,0300 1,82% 376,667 In total 11,420 4,79% 0,0300 1,82% 380,667

Fraction < 8 mm Weight (kg) % of total Volume (m3) % of total


In total 6,750 2,83% 0,0150 0,91% 450,000

Sample in total Weight (kg) % of total Volume (m3) % of total


In total 238,420 100,00% 1,6450 100,00% 144,936 Methodology of analysis of MSW in CR is documented in Fig. 8. – 11.


Figure 8. Screens of size 40x40 and 20x20 mm - screening analyses of MSW


53


Figure 9. Screen 8x8 mm - screening analyses of MSW


Figure 10. Oversize fraction of MSW above 40 mm is fully materially analysedure



Figure 11. Fraction over the 20 mm of MSW

Figure 12.


55

Part of the research was a physical- chemical analysis. Some results are presented in the following Figures 12. - 15.

Figure 13.

Figure 14.


Benešová, L., Černík, B., Kotoulová, Z.and Vrbová, M. (2000). Intensification of collection, transport

and sorting of MSW. Technical Report of Research and Development Project of the Ministry of the Environment of the Czech Republic 720/2/00, Charles University in Prague, Faculty of Science (in Czech with English summery)

Figure 15.

Figure 12.-15. Content of Heavy Metals in P and C dwelling in two fractions in MSW in CR

Benešová, L., Černík, B. Kotoulová, Z., Hnaťuková, P. and Doležalová, M. (2008). Research of Character of MSW and Optimization its Using. Technical Report of Research and Development Project of the Ministry of the Environment of the Czech Republic SP/2f1/132/08, CR, Charles University in Prague, Faculty of Science (in Czech with English summery)

Figure 16. Content of Specific Organic Compounds in P and C dwelling in two fractions in MSW in CR.


57

Common Components in MSW

1. Paper and Paper Products Paper and paper products are generally the largest components of MSW. The proportion

of this commodity in European countries ranges between 10 and 45 % by weight, the OECD average is 15 %, in the USA 37 %, and Australian production is 26% (Davis, 2005).

In the CR, paper is the second most frequent commodity in MSW (Vrbova, 2006). The proportions of various forms of paper waste resulting from analyses in spring 2009 are shown in Fig. 17. – 23. (fraction above 40 mm)

Figure 17. Paper (mixed)

Figure 18. Carton / Cardboard


Figure 19. Composite packaging

Figure 20. Other packaging

Figure 21. Newspaper and journals


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Figure 22. Advertising

Photos by P. Hnaťuková

Figure 23. Other paper

2. Glass

Glass occurs in MSW in the form of bottles, jars, various appliances and electronics. The proportions of various forms of glass waste resulting from analyses in spring 2009 are shown in Fig. 24.-27. (fraction above 40 mm)


Figure 24. Glass (mixed)

Figure 25. Glass pure

Figure 26. Glass brown


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Figure 27. Glass green

3. Plastics The largest group of wastes in many countries are plastics. They are used as packaging

and in various goods and appliances. The proportions of various forms of plastic waste resulting from analyses in spring 2009 are shown in Fig. 28.-34. (fraction above 40 mm)

Figure 28. Plastics (mixed)

Figure 29. PET bottles pure


Figure 30. PET bottles coloured

Figure 31. Foil packaging

Figure 32. Foil non packaging


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Figure 33. Other packaging


Figure 34. Other plastics

4. Metal, Biowastes and Textiles Metals are divided into ferrous a non-ferrous materials. Among the non-ferrous materials

are mainly aluminium used as beverage containers, and other packaging. Biowastes include all putrescible material, especially food and yard waste. Textiles in MSW occur in the form of clothing and other goods. Some photos are

presented in the Fig. 35.-37.


Fig. 35. Metals from MSW- results of the survey in 2009, the CR, fraction > 40 mm

Figure 36. Biowastes from MSW- results of the survey in 2009, the CR, fraction > 40 mm


Figure 37. Textiles from MSW- results of the survey in 2009, the CR, fraction > 40 mm


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5. Hazardous Waste Most hazardous materials in household waste occur either as heavy metals, organic

compounds or asbestos Weigand (2005). Common household hazardous waste are various types of batteries (containing heavy metals), household cleaning products (organic compounds), paints (organic compounds), products for plant care (containing various herbicides), paint strippers and removers (organic compounds), asbestos-containing material and used motor oil (Williams, 1998)

4.4.4. Collection

The functional element of collection includes not only the gathering of solid waste and recyclable materials, but also the transport of these materials, after collection, to the location where the collection vehicle is emptied. This location may be a materials processing facility, a transfer station or a landfill disposal site.

According the style of collection the system can be divided into 5 types. Every type has some advantages and some disadvantages.

• Kerbside system - characterized by containers, dustbins or sacks beside every house

or residence (Fig.38). Collection crews empty containers into waste collection vehicles and returns the containers to their storage location. The advantage of these systems is relatively low price, regular collection according to a schedule and a specific storage locality. Disadvantages include the necessity of a schedule, problems with collecting crews, hygienic problems on collecting days - dust, noise, smell . Containers used in the CR include traditional metal or plastic dustbins, wheeled bins or sacks. Collection frequencies range from daily empting from each collection point (Paris) to three to one time per week in other cities. Once per week collection is a minimum for all cities.


Figure 38. Typical dustbins used in rural areas in the CR


• Setback collection - containers are placed in special places according to a scheduled collecting time, normally once or twice in a month. The schedule is given by the local municipality and announced on a public board or other messaging system. A special crew transports the containers and empty them in a storage location. In the CR, as is typical for other locations, this type of collecting is mostly used for bulky wastes (Fig. 39. – 40.).

Advantages are the big volume of the containers, containers are only present on a given

date in the street, and the special crew works very quickly and are responsible for cleaning of locality.

Figure 39. Collection of bulky wastes – Czech Republic 2009


Figure 40. Collection of bulky wastes – Czech Republic 2009


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• Backyard collection – in this method there is a special locality – given by the municipality- in which wastes are transported by residents and then sorted into special containers. In this method, wastes are deposited into containers and then transported by truck or cars to a processing facility. Advantages are daily operation, containers (Fig. 41) not present in the street, and wastes are sorted and not polluted. Disadvantages include that the method is time-consuming for the residents, is relatively expensive, and needs good organization in backyards with a semi-skilled crew (Fig. 42).

Figure 41. Example of backyard in Prague, CR


Figure 42. Example of backyard in Prague, CR


• Drop-off collection at a special collection point – residents transport the waste to a specified point, which can be a transfer station, shops, a petrol pump, etc. This type of collection is also suitable for hazardous wastes, e.g. medical products, pesticides, batteries, fluorescent lamp tubes etc. The advantages of the system are low price, small crew, and purity of the waste. Disadvantages include the necessity to transport waste by residents and the risk of illegal dumping if collection points are too far or not clearly described. In the CR, this type of collection is used for medicine, which are transported to chemists, and batteries, which are taken to various shops.

• Sorted waste collection - characterized by coloured containers placed in specially designated areas not far from residential houses. The residents transfer the sorted waste (in the CR paper, glass, plastic, and drinking cartons) to the various coloured containers. The distance can not be greater than 200 m from the residence. The advantages of this system are in the purity of wastes (material can be reused or recycled), and relatively low price (in the CR the system is supported by EKOKOM- authorized society for packing). Disadvantages are similar as in a kerbside system.

“Any reason for sorting waste is a good one” is a slogan underlining a current TV campaign promoting recycling in the Czech Republic, and most Czechs would agree recycling is a necessity. By and large, Czechs are conscientious recyclers, with around 70 percent regularly recycling plastics, paper, glass and other materials. In fact, statistics recently released by Eurostat revealed that Czechs are leaders when it comes to plastics: in 2006 they recycled 44 % of PET beverage bottles and other packaging – which is 3 % more than traditional leader Germany. But ITL not all good news. Most are aware that the country still needs to do much more – and point out while successful in some areas, in other they are clearly lagging. Source: Official TV campaign in Czech television , 2008.


Figure 43. Containers for the sorted wastes in the CR (blue – paper, green a white - glass, yellow – plastics).


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Waste collection methods vary widely between different countries and regions (Fig. 43. and 44.). Domestic waste collection services are often provided by local government authorities, or by private industry. Some areas, especially those in less developed countries, do not have a formal waste-collection system.

Photo by L.. Benešová

Figure 44. Containers for sorted waste in Australia – Perth. Every urban domestic household is provided with three bins: one for recyclables, another for general waste and another for garden materials - this bin is provided by the municipality if requested. Also, many households have compost bins.

Some examples of waste collection methods: • In European countries, kerbside collection of wastes is the most common system

throughout the countries. In the CR, 99,6 % of residential areas are covered by this system. In some more wealthy countries, a few communities use a proprietary collection system known as Envac , which conveys refuse via underground conduits using a vacuum system. A similar method is also in use in Canada.

• In Australia, kerbside collection is the main method of disposal of waste. Household waste is segregated: recyclables sorted and made into new products, and general waste is dumped in landfill areas. According to the ABS, the recycling rate is high and is increasing, with 99% of households reporting that they had recycled or reused some of their waste within the past year, up from 85% in 1992.

• In Taipei, the city government charges its households and industries for the volume of rubbish they produce. Waste will only be collected by the city council if the waste is disposed in government-issued rubbish bags. This policy has successfully reduced the amount of waste the city produces and increased the recycling rate.


Collection Equipment

Collecting equipment is usually divided between municipalities a private society. Generally used equipment includes collecting vehicles, trucks, and trucks with special equipment on board (computers for monitoring truck performance and collection operations). \examples of various collection equipment are shown in Fig. 45. and 46.

Photo by L.. Benešová

Figure 45. Waste collection equipment in Prague 2005


Figure 46. Waste collection equipment – Lyon (France), exhibition Pollutec 2008


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4.4.5. Separation and Processing and Transformation of Solid Wastes The types of means and facilities that are now used for the recovery of waste materials

that have been separated at the source include kerbside collection, and drop-off and buy-back centers. The separation and processing of wastes that have been separated at the source and the separation of commingled wastes usually occur at a materials recovery facility, transfer stations, combustion facilities and disposal sites.

The main processes in the transformation of solid wastes are reuse and recycling. Because of non-uniform terminology, it is necessary to define some terms.

First of all, it is important to clarify the difference between reuse and recycle, which are terms that are often misused.

Reuse – in our language, this means using an item again for its original purpose. The most common example is the returnable drink bottle (in the CR these include beer, milk and some mineral water bottles).

Recycling – is used for processed material, i.e. paper is processed to make recycled paper, cardboard or newspaper; plastic is shredded and processed into new products such as car steering wheels and clothing insulation filling; sorted glass is processed into new glass, etc.

The recycling mechanism has a universal symbol

One arrow in the symbol indicates source separation (removal of materials from the

waste stream), the second arrow symbolizes processing of the material, and the third represents the consumer.

Source separation is the removal of potentially recyclable material from the waste stream.

Residual waste is waste after the separation of recyclable materials. Reuse involves using a product more than once or reusing it in other applications. The

reuse of beverage bottles was very common until the 1980s (Wiliams, 1998). This scheme was widely used and cost effective, since collecting, washing and transporting returned bottles was more economic than manufacturing new ones. After the introduction of new materials, the reuse system of bottles declined. Some schemes have still survived, such as traditional beer or milk bottles.

Recycling processes have been known for a very long time, since we first realized that composting is a process which uses biodegradable waste and changes it into fertilizer. But in recent years, recycling efforts have focused on efforts to reduce the amount of wastes and especially to reduce the waste loads to local landfills.


Recycling of MSW Recyclable components include paper, plastics, glass metals and putrescible materials.

But, in some cases it is not possible to recycle some of the waste due to contamination. Approximately 40% of household waste is potentially recyclable after discounting the contamination of materials;

In some follow figures there are machines, which helps to sort a recycle waste . See Fig. 47. and 48.

Figure 47. Machine for sorting colour and white glass (Exhibitipon Pollutec,Lyon 2008)


Figure 48. Machine for liquid removal and pressing of PET and other packaging (Exhibition Pollutec, Lyon 2008)


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4.4.6. Transfer and Transport This element involves two steps: • the transfer of wastes from a smaller collection vehicle to larger transport equipment, • the subsequent transport of wastes, usually over long distances, to a processing or

disposal site. Special transport facilities are used for transportation of waste, especially over long

distances. The collection, temporary storage and transportation are controlled by regulations, and every county has its own special regulations.

I.E. according regulations 61-107.5 of Bureau of land and waste Management - Columbia :

− all vehicles used to collect MSW shall be constructed and maintained so as to preventdropping, sifting or blowing or other escapement of solid waste from vehicle.

− precautions shall be taken to prevent spillage, or leakage during transport from allvehicles used to collect and or transport MSW that produce leachate.

− all vehicles used to collect and or transport putrescible MSW shall be emptied on a daily basis , unless the exemption is requested and approved by the Department.

− Collection and transportation vehicles or other devices used in transporting putrescible MSW shall be cleaned and maintained as often as necessary to prevent odors, insects, rodents or other nuisance conditions.

From Regulations 61-107.5 SWM : Collection, temporary storage and transportation of Municipal Solid Waste, of Bureau of Land and waste Management division of Mining and Solid Waste Management - Columbia, May 1993

The transport of hazardous waste transport was treated as part of the Basel Convention.

This Convention was opened for signatures on 22 March 1989, and entered into force on 5 May 1992. A list of parties to the Convention, and their ratification status, can be found on the Basel Secretariat's. Of the 172 parties to the Convention, Afghanistan, Haiti, and the United States have signed the Convention but have not yet ratified it.

4.4.7. Disposal

The Basel Convention on the Control of Transboundary Movements of Hazardous Wastesand Their Disposal is an international treaty that was designed to reduce the movements ofhazardous waste between nations, and specifically to prevent transfer of hazardous waste fromdeveloped to less developed countries (LDCs). It does not, however, address the movement of radioactive waste. The Convention is also intended to minimize the amount and toxicity of wastes generated, to ensure their environmentally sound management as closely as possible to the source of generation, and to assist LDCs in environmentally sound management of the hazardous andother wastes they generate. Source: www.Wikipedia.org.

Today, the disposal of wastes by landfilling or landspreading is the ultimate fate of all

solid wastes, whether they are residential wastes collected and transported directly to a landfill site, residual materials from materials recovery facilities (MRFs), residue from the


combustion of solid waste, compost, or other substances from various solid waste processing facilities. A modern sanitary land is not a dump; rather, it is an engineered facility used for disposing of solid wastes on land without creating nuisances or hazards to public health or safety, such as the breeding of rats and insects or the contamination of ground water.

The basic methods for disposal of MSW are: • landfilling • incineration • composting

4.4.6.1. Landfilling Landfill is the oldest method for the disposal of wastes and is still currently the most

widely used technology for getting rid of MSW. About 120 million tonnes of controlled waste per year are landfilled in the UK, which

includes 90% of household waste. In Italy the proportion of landfilling waste is 54% (Newman, 2005)

In the CR, about 3 million tonnes of MSW per year are landfilled, which is 65 % of the total MSW production per year. See Table 7.

Table 7. Disposal of MSW in the Czech Republic (t)

Manner of use 2003 2004 Landfilling 2 924 458 2 997 185 Treatment by soil processes 18 117 4 074 Deep injection - 872 Deposition in the special technicallycontrolled landfills 414 6

Biological treatment 132 163 142 337 Physical-chemical treatment 8 835 6 577 Combustion 222 928 214 388 Final or permanent depositing 212 227 From Statistical Environmental Yearbook of the Czech Republic

4.4.6.2. Incineration

Incineration is the second major option for waste treatment and disposal in many countries in the world. In some countries such as Japan, Switzerland, Belgium and Sweden, incineration of MSW accounts for over 50% of the waste disposal.

Incineration of waste has a number advantage over the landfilling: • the waste is reduced into biologically sterile ash product. For MSW reductions result

in one tenth of the pre-burnt volume and one third of the pre-burnt weight. • Incinerations do not produce methane • Incinerators can be used as a source of energy to produce steam for electric power

generation, heat or hot water for district heating, and thereby conserves valuable primary resources.

• Of course incineration has also some disadvantages.


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• Generally the capital investment is very high, • In some facilities there is a lack of flexibility in the choice of waste • Every incinerator produces emissions which can have negative effects on human

health • Every incinerator produces a solid waste residue which requires management.

4.4.6.3. Composting

Composting is one of the oldest methods of recycling organic materials, and removes a large portion of the biodegradable waste from the waste stream.

In general, there is a relatively rapid aerobic biological degradation of organic waste, a process taking about 4 -6 weeks. The result of this biodegradation process is a stabilized product. Small scale composting has been practised for many years at the individual household level.

One problem with composts is the purity. All composting in the CR are controlled according to the Czech technical standard (ČSN). The limit concentrations of some hazardous items according the ČSN 46 5735 – Industrial compost are given in Table 8.

Table 8. The limit concentrations of heavy metals in compost according to �SN 465735

Heavy metals The limit concentrations of heavy metals in mg/kg Dried sample of compost Dried raw material I. class II. class

As 10 20 50 Cd 2 4 13 Cr 100 300 1000 Cu 100 400 1200 Hg 1 1,5 10 Mo 5 20 25 Ni 50 70 200 Pb 100 300 500 Zn 300 600 3000

Green waste includes garden trimmings, leaves, shrubs, plants, grass, street trees, and

tree trunks, park trees or twigs etc. that arise from households, maintenance of public parks and garden, and commercial premises.

If the quality of compost is suitable, it can be used as a fertilizer. Quality compost is stabilized, and adds materials that improve the soil nutrient content and structure (especially for clay soil), and helps soils to retain moisture.

Bulky waste or bulky refuse is a technical term describing waste types that are too large to be accepted by regular waste collection. In many countries, it is usually picked up regularly from the streets or designated areas. This service is provided free of charge in many places, but often a fee has to be paid.

Bulky waste items include discarded furniture (couches, recliners, tables), large appliances (refrigerators, ovens, televisions), and white goods (bathtubs, toilets, sinks). Branches, brush, logs and other green waste are also categorized as bulky waste, although they may be collected separately for shredding and/or composting.


In the CR, inhabitants may deposit bulky waste into Large Capacity Containers (LCC) withminimum volume 9m3. The Prague City Hall reimburses for the installation of 8, 764 such containers per year. LCCs are allocated to the City Districts depending on their respective populations, and every City districthas at least 24 LCCs at its disposal. Some City District Authorities place additional LCCs at theirexpense and decision. Inhabitants may also deposit bulky waste at the yards operated by the Prague City Hall. From Prague Environment 2006 Prague City Hall

Grapple trucks, also known as knuckleboom loaders, are often used to collect bulky

waste. In the EU, refuse collection vehicles (RCVs) or crushers are being increasingly phased out as more bulky waste is diverted for re-use and recycling.

5. LCA METHODOLOGY Evaluation of environmental impacts of MSW represents a very komplex multiparametric

and multicriteron problem. The evaluation methods and models should be preferably based on the following characteristics and essential qualities:

• complexity - the method should cover the most important environmental criteria, • time dependency - the method should consider the whole life cycle (ISO 14040), • probability - the evaluation method should respect the probability feature of the time

dependent problem. In CR has carried out studies using metodology under the LCA standard EN ISO 14040-

43 on the basis of terrain collection if primary data in the whole CR. Several municipal waste treatment methods were subject to this assassement Benešová, 2004):

• separate collection and recyclingat a paper mill glasswork and a mixed plastic

treatment facility • collection and energy recovery ( at incinerator in Pratur, Brno and Liberec) • collection and landfilling Environmetal inpacts were assessed through the use of cumulated values. One of the

interesting topic researched was, what changes would come in 2010 in comparison with 2004?

A deterioration in MSW management impact on the environmnt is awaited, particularly in the are of water management ( consumption, of tester water) emissions of CO, aromatic hydrcarbons and CO2eq.

Generally, LCA metod is a tool for investigating such waste management problems of the future.


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6. CONCLUSION A framework for classifying municipal solid waste , its composition, components and

basic disposal processes has been presented. There were described waste generation and handling which involves the activities associated with management of waste until they are placed in storage container for collection.

Great deal of the chapter is payied to separation of waste components which is an important step in the handling and storage of solid waste at the source.

Collection and disposal is another important step because the functional element of collection includes not only the gathering of solid waste and recyclable materials, but also the transport of these materials, after collection, to the location where the collection vehicle is emptied. This location may be a material processing facility, a transfer station or a landfill disposal site.

Disposal by landfilling or landspreading is the ultimate fate of all solid wastes, whether they are residential wastes collected and transported directly to a landfill site, residual materials from materials recovery facilities (MRFs), residue from the combustion of solid waste, compost or other substances from various solid waste processing facilities. A modern sanitary landfill is not a dump; it is an engineered facility used for disposing of solid wastes on land without creating nuisances or hazards to public health or safety, such as the breeding of rats and insects and the contamination of ground water.

Apart from process relating paramters include soci-economic long term trends often play a key role in the assessement of handling and disposal of wastes.

Because of heterogenity of minicipal solid waste reuse, recycling, incinertion and lanfilling all have their place in modern waste management. The only problem is to determine their respective optimal ratio.

REFERENCES

Alexander, J. H. (1993). In Defense of Garbage. Praeger, Westport, CT in Pitchel, J. (2005). Waste Management Practices: . USA:municipal, hazardous,and industrial. USA: CRC Press , Taylor and Francis Group

Benešová, L. (2004). MSW Management in the Czech Republic: LCA metodology. Warmer Bulletin, 958-10

Bilitewski, B., Härdtle, G. and Marek, A. (2000). Abfallwirtschaft Handbuch fur Praxis und Lehre. Berlin, Springr –Verlag, ISBN 3-540-64276-6

Černík, B. and Benešová, L. (2008). State and Prognosisof the Development of Municipal Waste Management System in Czech Republic, Part I. Acta Universitatis Carolinae Environmentalica, 22, 25-37

Davis,G. (2005). What’s in a bin? Waste Management, 2, 37-39 Dobson, G., Plochl, C., Buell, U. and Davidson, G. (2003). A proposal for Standard Waste

Classification System as Part of Standardised Methodology for Municipal Solis Waste Analyses in European Union. CIWM Scientific α Technical Review, 4, 21-39

Filip, J., Božek, F. and Kotvicová J. (2003). Municipal Solid Waste and landfilling. Brno: Mendels -Agricultural and Woods University, ISBN 80-7157-712-X ( in Czech)


Chang, N. and Davile, E. (2008). Municipal Solid Waste Characterizations and Management Strategies for the Lower Rio Grande Valley, Texas. Waste Management, 28, 776-794

Kelly, K. (1973). The history and Future of Garbage in America. New York, NY, Saturday Review Press

Li’ao, W., Ting’quan, P., Chuan, H. and Hui, Y. (2009) . Management of municipal solid waste in the Three Gorges region. Waste Management, 29, 2203-2209

Liu,D. H. F., Loptám, B. G. And Bouis P. A. (1997). Environmental Engineer’s Handbook (second Edition). New York, USA: Lewis Publisher

Pehlken, A. and Pretz, T. (2003). Qvalitätssicherung in der Abfallanalytik. Müll und Abfall, 35, 74-78

Pitchel, J. (2005). Waste Management Practices: . USA:municipal, hazardous,and industrial. USA: CRC Press , Taylor and Francis Group

Rhyner,C.R.(1992).The monthly variations in solid waste generation. Waste Management α Research, 10, 67 - 71

Sokka, L., Antikainen, R. and Pekka, E. K. (2007). Municipal solid waste prodiction and composition in the period 1960-2002 and prospects until 2020. Resources, Conservation and Recycling, 50, 475-488

Vesilind, P.A. ,Worrell, W. and Reinhart, D. (2002). Solid Waste Engineering, CA Briooks/Cole, Pacific Grove

Weigand,H. and Marb, C.(2005). Zusammensetzung und Schadstoffgehalt von Restmüll aus Haushaltungen. Teil II. Müll und Abfall, 37, 522-530

Wilson, D. G. (1977). Handbook of Solid Waste Management. New York, NY, Van Nostrand Reinhold Company

Williams, P.T. (1998). Waste teatment and Disposal. Great Britain: John Wiley α Sons Ltd, Tammemagi, H. (1999). The Waste Cisis. Landfils,Incinerations, and the Search for a

Sustainable Future, New York, NY, Oxford University Press Tchobanoglous, G. Theisen, H. and Vigil, S.(1993). Integrated Solid Waste Management:

Engeneering principles and Management Issues. New York: McGraw-Hill College.

TECHNICAL REPORTS

Statistical Environmental Yearbook of the Czech Republic (2005), Prague, CENIA – Czech Environmental Information Agency.


Benešová, L., Černík, B. Kotoulová, Z. and Vrbová, M. (2005). Wastes from municipalities – environmental and social problem of the future. Technical Report of Research and Development Project of the Ministry of the Environment of the Czech RepublicSL/7/102/05, CR, Charles University in Prague, Faculty of Science (in Czech with English summery)

Benešová, L. (2006). Biodegradable waste, Proceedings of IInd. Conference, Náměšť nad Oslavou, CR, ZERA –local non governmental organization (in Czech)


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Benešová, L., Černík, B. Kotoulová, Z., Hnaťuková, P. and Doležalová, M. (2008). Research of Character of MSW and Optimization its Using. Technical Report of Research and Development Project of the Ministry of the Environment of the Czech Republic SP/2f1/132/08, CR, Charles University in Prague, Faculty of Science (in Czech with English summery)

ELECTRONIC MEDIA

United States Environmental Protection Agency Office of Solid Waste (5306P) EPA530-R-08-010, November 2008, http://www.epa.gov/libraries/core/solid.htm (HTML)

OECD Environmental Indicators – www.oecd.org./env/indicators Newman, D.(2005). Residua Waste Management in Italy an Overview of Recent History and

Future Trend, Conference of the Future and residua Waste Management in Europe 2005 newman-doc.pdf | newman-ppt.pdf

Krupa, F. Urban Sanitation Before the 20th Century A History of Invisible Infrastructure. www.translucency.com/frede/parisproject

Hráský, J.,V. Stokování měst, čištění a užití vod stokových, Technický průvodce pro inženýry a stavitele, Kanálstory aneb Muži pod Prahou II., 1925 [email protected]

Regulations 61-107.5 SWM : Collection, temporary storage and transportation of Municipal Solid Waste, of Bureau of Land and waste Management division of Mining and Solid Waste Management - Columbia, May 1993, www.scdhec.gov/environment,

Prague Environment 2006 Prague City Hall, envis.praha-mesto.cz/rocenky/pr06 The Basel Convention on the Control of Transboundary Movements of Hazardous Wastes

and Their Disposal www.Wikipedia.org. U.S.Environmental Protection Agency’s (EPA’s) Climate Change and Waste Web site at

<www.epa.gov/ globalwarming/actions/waste/tools.html> or write to: EPA’s Office of Solid Waste (5306W), Ariel Rios Building, 1200 Pennsylvania Avenue, N.W., Washington, DC 20460, U.S.A.


Chapter 3

WASTE BIOMASS SUPPLY CHAINS FOR ENERGY PRODUCTION: A HIERARCHICAL

DECISION-MAKING FRAMEWORK

E. Iakov*, D, Vlachos and A. Toka

ABSTRACT

The development of renewable energy sources has clearly emerged as a meaningful intervention for enhancing the fragile global energy system with its limited fossil fuel resources as well as for reducing the numerous related environmental problems. In this framework, biomass utilization has proven to be a viable alternative for energy production even though its usage is still at its infancy on a global scale. Thus, a number of critical issues for all the involved stakeholders, such as potential investors, involved regulators and decision-makers, need to be addressed systemically.

One of the first challenges that hinders the increased biomass utilization for energy production is the cost of its respective logistics operations. What differentiates biomass supply chains from traditional supply chains is the importance of factors such as biomass product quality as this is dictated by the relevant energy production technology, weather related variability, localized agricultural capacity and seasonality, and stochasticity of demand. In this chapter, we present a novel methodological framework for the design and evaluation of sustainable waste biomass supply chains, taking into account the collection, storage, and transport operations for supplying facilities with organic raw materials for energy production.

First, the potential of waste biomass for energy production is presented, as well as the relevant regulatory incentives, the constraints and the critical issues that have to be tackled. Moreover, the generic system components of Biomass Supply Chains (BSCs) are described in conjunction with their relevant key variables and unique characteristics. Following that, we recognize the natural hierarchy of the decision-making process and propose an integrated methodological framework that spans all levels of the hierarchy. We then map the existing research efforts within the proposed framework in order to

* Laboratory of Quantitative Analysis, Logistics and Supply Chain Management, Department of Mechanical

Engineering, Aristotle University of Thessaloniki, Greece, [email protected]

E. Iakov, D, Vlachos and A. Toka 82

identify gaps and overlaps. We proceed with a taxonomy of the current state of the art research, based on the relevant modeling techniques in order to identify the limitations of the existing modeling efforts. We wrap-up by discussing our conclusions in the last section.

INTRODUCTION Renewable energy sources (RES) play a pivotal role in the current global strategies for

the attainment of a plethora of objectives such as reduction of greenhouse gas emissions, the partial replenishment of fossil fuels, the independence from external energy supply and the compliance with the obligations as dictated by the International Conference of Kyoto (United Nations, 1998). Reserves of fossil fuels, such as oil, gas and coal are the main sources of energy spread over a small number of countries, thus forming a fragile energy supply that is expected to reach its limit within the foreseeable future. Moreover, their usage leads to the degradation of the environment via atmospheric pollution, acidification and the emission of greenhouse gases (Richardson and Verwijst, 2007). According to the World Health Organization (WHO), the side-effects of climate change on human health are enormous and are expected to grow even more by 2020 (Asif and Muneer, 2007).

Biomass includes vegetation and trees, energy crops, as well as biosolids, animal, forestry and agricultural residues, the organic fraction of municipal wastes and certain types of industrial wastes. It emerges as a promising option, mainly due to its potential worldwide availability, its conversion efficiency and its ability to be produced and consumed on a CO2-neutral basis. Biomass is a versatile energy source, generating not only electricity but also heat, while it can be further used to produce biofuels (Veringa, 2006). Moreover, the production of second-generation biofuels obtained by waste biomass is promoted by governments in the context of an overall effort to avoid the direct and side effects that stem from the energetic utilization of energy crops, as well as to support effectively waste management policies. Waste-to-energy plants offer both environmentally safe waste management and disposal, and generation of clean electric power. Thus, maximizing the value of waste biomass and organic substrates for energy production is of an ever increasing priority.

One of the most critical bottlenecks in increased biomass utilization for energy production is the cost of its respective logistics operations. The rising demand for biomass and the increasing complexity of the often multi-level involved supply systems outline the need for comprehensive biomass supply chain management (SCM) approaches. The requirements with respect to biomass supply in terms of quality and quantity can differ substantially, depending on the energy demand trends, the energy production technology, the end use of the power generated and, the cost-efficiency and feasibility of its logistics operations. Additionally, various parameters can limit the effectiveness of biomass production systems including localized agricultural capacities and seasonality. To this end, SCM bears the challenge to develop optimal policies adapted to uncertain parameters and subject to additional local and inter-regional conditions and constraints, such as the existing infrastructure, geographical allocation of collection areas, the running regulatory and techno-economic environment, and the competition among several consumers.

Waste Biomass Supply Chains for Energy Production

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As energy production from biomass and organic substrates is still at its infancy on a global scale, a number of issues critical for all involved stakeholders, such as potential investors, involved regulators and decision-makers need to be addressed. Such critical questions that need to be answered are listed below:

• Which are the incentives for investing on waste-to-energy systems? • Does the current regulatory environment support biomass energy production? Are

there additional regulatory incentives for employing waste-to-energy systems? • Which types of biomass could be profitably utilized for a specific region, and why

should waste biomass be preferred as feedstock for producing energy instead of energy crops?

• Currently, is there an adequate amount of biomass resources available currently worldwide? What is expected to happen in the long-run?

• Which are the unique characteristics of biomass supply chains that differentiate them from conventional networks?

• How should waste biomass supply chain networks be designed? • Which are the state-of-the-art supply chain management practices that a potential

energy producer should adopt? • Which network configuration would be efficient enough at the present time but also

robust and flexible enough to adapt to inevitable changes in the long run? • Which kind of policies are required to achieve bio-energy systems’ sustainability? In this chapter, we propose a new methodological approach for the design and evaluation

of sustainable waste biomass supply chains, taking into account the collection, storage, and transport operations for supplying facilities with organic raw materials for energy production. More specifically, in Section 2 we first discuss the potential of waste biomass for energy production and then present the relevant incentives, the constraints and the critical issues that have to be tackled. In Section 3, the generic system components of Biomass Supply Chains (BSCs) are described along with the relevant key variables and their unique characteristics. We focus on systems that exploit various types of biomass from different sources and on the environmental impact of biomass logistics networks. In Section 4, following the natural hierarchy of the decision-making process, we propose an integrated decision-making framework and then classify accordingly the existing research. Subsequently, advanced modeling techniques for biomass supply chains are presented in Section 5 and a taxonomy of the existing modeling efforts is provided. Through this analysis of the current state of the research, we identify specific gaps that need to be addressed in the future. Finally, we sum up with the Conclusion Section.

THE PROBLEM UNDER STUDY

The Potential of Waste-to-Energy Policies In order to understand the future role of energy production from waste biomass on a

global level, it is important to investigate the drivers for its utilization against competitive


options for substrate resources for energy production, such as energy crops. Biomass in general is considered to be a promising option for substituting fossil fuels for energy production mainly due to its potential worldwide availability, its conversion efficiency and its ability to be produced and consumed on a CO2-neutral basis. According to the European Union’s Action Plan for Biomass (European Commission, 2005), an increase in biomass use could bring many benefits, as the diversification of Europe’s energy supply, the direct employment for thousands of people mostly in rural areas and the potential pressure on oil price.

However, despite the attention that the production of biofuels from energy crops (also referred as first generation biofuels) has attracted, a number of issues have emerged questioning the feasibility of this policy. According to a report published by OECD and the United Nations’ Food and Agriculture Organization (OECD/FAO, 2007), the increased demand for biofuels is causing fundamental changes to agricultural markets that drive up world prices for many farm products. The vast majority of first-generation biofuel feedstocks, especially in the case of bioethanol, are eatable products, which has led to concerns that biomass previously destinated for human consumption is diverted to fuel production. An additional concern relates to the inefficiency of first-generation biofuels, as a large amount of energy is expended on cultivating, harvesting and processing the biomass, while only a relatively small portion is used for energy production (van der Laak et al., 2007). Moreover, according to Bomb et al. (2007) crops used for first-generation biofuels’ production have lower energy content than conventional petroleum products, which implies that a larger volume of biofuels is consumed for the same amount of energy produced. According to a recent directive of the European Commission (EC), the EC shall monitor the origin of biofuels and bioliquids consumed within the EU, the impact of their production, the commodity price changes associated with the use of biomass for energy and any associated positive and negative effects on food security (European Parliament and Council, 2009a).

On the other side, second-generation biofuels obtained by waste biomass are not plagued by these problems, while at the same time they could support effectively waste management policies. Second-generation biofuels are obtained from feedstocks not traditionally used for human consumption. As a result, there is much less concern about their use leading to famine in developing countries, or adversely affecting consumer prices in the developed nations. Aside from reducing the threat of food supplies being diverted to fuel production, second-generation biofuels are argued to be more environmentally friendly than first-generation biofuels (Deurwaarder, 2005). In addition, the choice of feedstock is wide, including non-food parts of current crops, such as stems, leaves and husks that are left behind once the food crop has been extracted, as well as other crops that are not used for food purposes, such as switchgrass (a spreading perennial grass usually found in North America) or cereals that bear little grain, and industry waste including among others wood chips, skins and pulp from fruit pressing (Inderwildi and King, 2009).

Charles et al. (2007) argue that policy decisions that redirect traditional food crops to bioethanol or biodiesel will have limited benefit in the long run and argue that a more fundamental reorientation of agriculture is preferable in order to achieve greater production of second-generation biofuels. Large quantities of agricultural residues are produced annually worldwide and are vastly underutilised. According to current farming practice these residues are most of the times burnt, left to decompose, or grazed by cattle, while they can be collected and effectively utilized for energy production (Sims, 2002).


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From a policy-maker perspective, Kaya et al. (2008) discuss the benefits that stem from the use of agricultural waste for energy production and specifically: (i) lower CO2 emissions to the environment; (ii) reduced energy cost to the user, providing additional competitiveness for industrial and commercial users; (iii) large fuel cost savings; (iv) an opportunity to move towards more decentralized forms of electricity generation, where a plant is designed to meet the needs of local customers, avoiding transmission losses and increasing flexibility in system use; (v) improved local and general security of energy supply; (vi) an opportunity to increase the diversity of power generation plants and provide competition in generation; (vii) increased employment, especially in rural and farming communities, and (viii) economic development and growth in the agricultural sector. According to Porter and Reinhardt (2007), in addition to understanding its emissions related costs, every firm needs to systemically evaluate its vulnerability to climate-related risks. The authors suggest that business leaders need to approach global warming as any other strategic threat or opportunity, and not just as a philanthropic-individualized corporate social responsibility issue.

Taking all the above into consideration, maximizing value of waste biomass and organic substrates for energy production emerges as an ever increasing priority. Many past and recent research efforts document the (existing and potential) role of biomass in the future global energy supply. Theoretically, the total bio-energy contribution (combined in descending order of theoretical potential by agricultural, forest, animal residues and organic wastes) could be as high as 1100 EJ, exceeding the current global energy use of 410 EJ (Hoogwijk et al., 2003). Yamamoto et al. (2001) document using quantitative estimates that there will be a large bioenergy potential for biomass residues, such as cereal-harvesting residues, animal dung, roundwood felling residues, and timber scrap (277 EJ/yr in year 2100 on global level). Parikka (2004) suggests that covering the future demand for renewable energy by increasing the utilization of forest residues and residues from the wood-processing industry is a promising alternative. The author states that the total sustainable worldwide biomass energy potential, obtained from woody biomass, crops and straw represents about 30% of the current global energy consumption. Berndes et al. (2003) discuss the contribution of biomass in the future global energy supply based on a review of seventeen earlier studies on the subject, including residue generation and recoverability. A thorough overview of the global potential of biomass for energy to 2050 is presented in a report published by the International Energy Agency, an autonomous body established within the framework of the Organisation for Economic Co-operation and Development (OECD) to implement an international energy program (IEA Bioenergy, 2007).

Finally, addressing the issue at a European level, only a handful of papers focus on biomass availability (Eriksson and Björheden, 1989; Gielen et al., 2001; van Dam et al., 2007). Grahn et al. (2007) compare two models that investigate the cost-effectiveness of biomass utilization. As stated in the EC’s action plan for biomass dated in 2005, the Union should be meeting 4% of its energy needs from biomass (EC, 2005). According to this plan, the EU could more than double the biomass use by 2010 while complying with good agricultural practice, safeguarding sustainable production of biomass and without significantly affecting domestic food production. Furthermore, the EC presents certain conservative estimates on the potential to produce biomass for energy use, stating that the potential for 2010 is 2,5 times, the potential for 2020 is 3 to 3,5 times and for 2030 is 3,5 to 4,5 times the contribution of 2005. Forests, wastes and agriculture all contribute to this potential for growth.


Competing markets for biomass is another issue that has to be investigated when investing on bio-energy systems. The versatility of biomass with the diverse portfolio of conversion options makes it possible to meet the demand for secondary energy carriers, as well as biomaterials. (IEA Bioenergy, 2007). Furthermore, electricity production on average is expected to become less carbon-intensive in the long run due to the increased use of wind energy, PV and other solar-based power generation, carbon capture and storage technology, nuclear energy, and fuel shift from coal to natural gas. Using biomass for transport fuels is expected to gradually become more attractive from the perspective of reducing CO2 emissions. In addition, the use of biomass for biomaterials is expected to increase, both in well established markets (such as paper, construction) and possibly in large new markets (such as bio-chemicals and plastics) as well as in the use of charcoal for steel making.

State-of-the-art scenario studies on energy supply and mitigation of climate change agree that all climate-friendly energy options are needed to meet the future world’s energy needs and simultaneously drastically reduce greenhouse gas emissions. Sources such as wind and solar energy have good potential, but their utilization is also constrained by their integration into electricity grids. In addition, electricity production from solar energy is still expensive. Hydropower has a limited potential and utilization of geothermal and ocean energy has proved to be complex. Biomass in particular can play a vital role in the production of carbon-neutral transport fuels of high quality as well as in providing feedstocks for various industries. This is a unique property of biomass compared to other renewables and makes biomass a prime alternative to the use of mineral oil. Thus, as oil is the most limited of the fossil fuel supplies, biomass is particularly important for improving security of energy supply on the global as well as on a national level. It is therefore expected that biomass will remain the most important renewable energy carrier for many decades to come (IEA Bioenergy, 2007).

The Regulatory Environment Global warming has emerged as a critical issue for the international community. The

adoption of the United Nations Framework Convention on Climate Change (UNFCCC) in 1992 was a major step forward in recognizing the problem; it led to the Kyoto Protocol (adopted in 1997 and entered into force in 2005), that requires developed countries to reduce their greenhouse gas emissions below levels specified for each of them in the Treaty within the period from 2008 till 2012 (United Nations, 1998). After the conference on climate changes in Bali in December 2008, the parties of the UNFCCC have scheduled to meet for the last time on government level before the climate agreement needs to be renewed and are willing to end up with a Copenhagen Protocol to prevent global warming and climate changes (Climate Conference in Copenhagen, 2009).

On a EU level, the EC adopted a Green Paper in 1996, which calls for an increase in the proportion of renewable energy sources in the primary energy supply from 6% (1996) to 12% in 2010 (EC, 1996). This led to the adoption of two directives: (a) the Green Electricity Directive, which aimed to increase the portion of electricity from renewable energy sources to 22% by 2010 (European Parliament and Council, 2001a), and (b) the Renewable Transportation Directive which called for increasing the contribution of biofuels in transportation fuels to 2% by 2005, 5.75% by 2010 and 20% by 2020 (European Parliament and Council, 2003). Finally, Directive 2009/28/EC of the European Parliament and of the


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Council on the promotion of the use of energy from renewable sources, establishes a common framework for the promotion of energy from renewable sources, repealing both Directives of 2001 and 2003 (European Parliament and Council, 2009a). The EC sets mandatory targets for Member States to reduce their greenhouse gas emissions to meet the Community’s greenhouse gas emission reduction commitments up to 2020 (European Parliament and Council, 2009b).

The White Book titled “Energy for the future: renewable resources – White Book for a strategy and an action plan of the Community” (EC, 1997), proposes an action plan for the development of renewable resources, recommending that the main contribution to energy production should be provided mainly by biomass, and to a lesser degree by other renewable sources. In the wider context of an integrated and coherent energy policy and for the promotion of renewable energy sources, the EC’s action plan of 2005 (EC, 2005) sets out measures for increasing the development of biomass energy from wood, wastes and agricultural crops by creating market-based incentives to its use and removing barriers. Moreover, according to Directive 2009/28/EC (European Parliament and Council, 2009a) each Member State must have presented by June 2010 a national renewable energy action plan, including information on sectoral targets. The Commission’s Decision 2009/548/EC (EC, 2009) sets out the template for the national renewable energy action plans required by Directive 2009/28/EC. Specifically, the directive states that in order to exploit the full potential of biomass, the Community and the Member States should promote the greater mobilization of existing timber reserves and the development of new forestry systems. Bioenergy is also viewed by the EU as a solution for improving the security of supply by expanding the use of local energy resources (EC, 2001). Currently the EU imports about 50% of its energy requirements and the current trend indicates that its dependence on external energy sources will rise till about 70% in 2030.

Promoting waste-to-energy for its ability to reduce the volume of waste in an environmentally-friendly manner, to generate valuable energy and to reduce greenhouse gas emissions, EU member nations rely on waste-to-energy as the preferred method of waste disposal (Zafar, 2008). In fact, the EU has issued a legally binding requirement for its member States to limit the land filling of biodegradable waste. According to the Confederation of European Waste-to-Energy Plants (CEWEP), Europe currently treats 50 million tones of wastes at waste-to-energy plants each year, generating an amount of energy that can supply electricity for 27 million people or heat for 13 million people.

As far as the legislative framework for agricultural residue management is concerned, several regulations related specifically to agricultural waste have been developed. The EU’s agricultural policy with relevance to agricultural waste management and exploitation promotes efficiency and environmental protection in the management of agricultural by-products and waste, especially in the form of renewable energy (i.e. biomass energy) development. This policy is formed by the Animal By-Products Regulation No 1774/2002 (European Parliament and Council, 2002), the Regulation No 951/97 on improving the processing and marketing conditions for agricultural products (European Parliament and Council, 1997) and finally the agro-Environmental Measures Regulation (European Parliament and Council, 1992).

Various EU environmental directives have relevance to agricultural waste management and exploitation: the Waste Framework Directive (European Council, 1975), the Waste Incineration Directive (European Parliament and Council, 2000), the Large Combustions


Plants Directive on the limitation of emissions of certain pollutants into the air (European Parliament and Council, 2001b) and the Landfill Directive (European Council, 1999). Regulated issues include setting emissions’ limit for large combustion plants operated with biomass, and encouraging recycling, re-use, and reclamation of agricultural (and other) wastes, including the reclamation of waste for energy recovery. A comprehensive review of the EU policy and legislation relevant to agricultural waste can be found in (Kaya et al., 2008).

Finally, the EU has emerged as a global leader in addressing carbon dioxide emissions. It has established the European Union Emission Trading Scheme (EU ETS), the largest multi-national, emissions trading scheme in the world. Thus, a carbon market has been created and a growing number of businesses are making investment decisions for implementing climate-friendly policies. The European Parliament and Council in the context of the new targets it has settled for the EU regarding the lessening of CO2 emissions has published Directive 2009/29/EC so as to improve and extend the greenhouse gas emission allowance trading scheme of the Community (European Parliament and Council, 2009c). In addition, many governments are eager to reduce dependence on oil and gas imports and to further enhance energy security; this has led to the encouragement of energy efficiency and the promotion of domestic energy sources, including biomass (The Economist, 2007). The introduction of various regulatory interventions and supporting measures, such as governmental R&D programs, tax cuts and exemptions, investment subsidies, feed-in tariffs for renewable electricity, mandatory blending for biofuels or biofuel quotas, have been mostly temporary and tend to change frequently. Hence, the lack of a stable regulatory environment is a major impediment, as it discourages additional strategic investments.

BIOMASS SUPPLY CHAINS (BSCS) FOR ENERGY PRODUCTION

The Various Stages of Bscs

Figure 1. Graphical Representation of a Biomass Supply Chain.


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For designing biomass supply chain networks for energy production four general system components (basic operations) are identified: Biomass production / harvesting / collection (from single or several locations) and pre-treatment, storage (in one or more intermediate locations), transport (using a single or multiple echelons) and energy conversion (Figure 1). In the following paragraphs the system’s components are described and their special characteristics are discussed in order to identify the distinctive characteristics that differentiate BSCs from traditional supply chains, as well as to reveal their impact on the supply network’s efficiency.

Harvesting and Pre-Treatment Harvesting biomass represents one of the significant cost factors in BSCs. The harvesting

process is energy-intensive, primarily due to transport fuel costs, and can introduce contaminants, such as soil, which can subsequently lead to operational problems during processing to produce energy. The moisture content of the biomass varies with the time of harvest and for some crops it can introduce additional processing costs, due to the need to pre-dry, before processing further (McKendry, 2002a).

Woody species are harvested as felled-timber and are cut into lengths or chipped, depending on the subsequent energy conversion technology. The processing of biomass improves its handling efficiency and the quantity that can be transported. This can involve increasing the bulk density of the biomass (e.g. processing forest fuel or coppice stems into wood chips) or unitising the biomass (e.g. processing straw or miscanthus in the swath into bales). Woody biomass can be obtained as felling residues from traditional forestry timber growing activities, or as short rotation coppice timber (e.g. willow and poplar, grown for 3-4 years and then harvested). Herbaceous plant species are harvested as baled straw or grasses, or as seeds/grains. Processing can occur at any stage in the supply chain but often precedes road transport and is generally cheapest when integrated with the harvesting (Allen et al., 1998). Thus, harvesting costs depend on the type of biomass being produced and the processing costs necessary to provide a feedstock suitable for use in whichever biomass conversion process is to be used. The thoughtful development of a system to minimize machinery use, human effort and energy inputs can have a considerable impact on the cost of the biomass as delivered to the processing plant gate.

The harvesting approach fundamentally affects the storage, handling and transport requirements in the biomass supply chain, as there is a very high level of interconnection among the several operations. Several authors have discussed harvesting and especially methods, collecting machines, relative costs etc., along with storage or transportation issues, for specific biomass raw materials, such as switchgrass (Cundiff and Marsh, 1996), forest fuel (Eriksson and Björheden, 1989), cotton plant residues (Fischer and Gaderer, 2000; Gemtos and Tsiricoglou, 1992; 1999), herbaceous biomass in general (Cundiff and Grisso, 2008), logging residue (Nurmi, 1999) and corn stover (Shinners et al., 2007). Indicatively, Kinoshita et al. (2009) address the widespread adoption of woody biomass energy by presenting a cost model, focusing on cost-effective harvesting methods costs.

Additional processing of biomass on other stages after the time of harvesting is related to the conversion technology employed into the energy production facility. Unprocessed biofuel, in which case the material is used essentially in its natural form (as harvested) for direct


combustion, usually supplies cooking, space heating, or electricity production needs, although there are also small- and large-scale industrial applications for steam raising and other processes requiring low-to-medium temperature process heat. Processed biofuels in the form of solids (mainly charcoal), liquids (mainly alcohols), or gases (mainly mixtures with methane or carbon monoxide), can be used for a wide range of applications, including transport and high-temperature industrial processes (Kaltschmitt et al., 2004).

Storage The stage of biomass storage is a critical link of BSCs. In the case of biomass that is

harvested over a relatively short period of the year, such as straw and short rotation coppice, large quantities need to be stored in order that the supply of fuel is spread evenly on a year-round basis. This requires storage facilities that can be located on the farm/forest, at the conversion facility or at an intermediate site.

According to Rentizelas et al. (2009b), in most cases of the relevant research work low cost storage solutions are chosen, such as on-field biomass storage (Allen et al., 1998; Huisman et al., 1997; Sokhansanj et al., 2006). Both ambient and covered on-field storage have also been examined (Cundiff et al., 1997). The method of on-field storage has the advantage of low cost. However, biomass material loss is significant and biomass moisture cannot be controlled and reduced to a desired level, thus leading to potential problems in the power plant equipment. Moreover, the farmers may not allow on-farm storage of the biomass for a significant time period, as they may want to prepare the land for the next crop (Sokhansanj et al., 2006). Finally, health and safety issues exist due to increased moisture (Allen et al., 1998; Nilsson and Hansson, 2001).

Various studies consider the use of intermediate storage locations between the fields and the power plant (Allen et al., 1998; Nilsson and Hansson, 2001; Tatsiopoulos and Tolis, 2003). This storage scheme results in a higher delivered cost than a system in which there is only one road transport movement, as it requires that biomass material has to be transported first from farm/forest to the intermediate storage facility/facilities and then from storage to the conversion facility. According to Allen et al. (1998) using an intermediate storage stage may add 10–20% to the delivered costs, as a result of the additional transportation and handling costs incurred. However, in some cases intermediate storage may be inevitable as there are many biomass collection areas that cannot be easily accessed by road transport vehicles during wet winter periods while on-farm storage does not constitute a viable solution.

Finally, the option of settling the storage facility next to the biomass power plant has also been examined by several authors (Tatsiopoulos and Tolis, 2003; Papadopoulos and Katsigiannis, 2002). Papadopoulos and Katsigiannis (2002) present an innovative storage layout with biomass drying capability using dumped heat from the power plant. This concept aims at reducing faster the biomass moisture content and prevents material decomposition as well as fungus and spores formation. Using storage facilities attached to the power plant is the only viable option of accelerating the drying process of the biomass, as dumped heat may be used without need for extra energy consumption. However, most power stations or other energy production facilities to which biomass is supplied have limited on-site storage facilities, mainly due to the space required to stock large quantities of seasonal products that bears the physical and financial costs of holding stock (Allen et al., 1998). In this case,


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inventory management should be effective enough in order to ensure that a few days of supply are available on-site with low risk of stock-out.

Rentizelas et al. (2009b) compared the above mentioned three biomass storage solutions found in the literature, in terms of total system cost. The authors suggest the development of a multi-biomass system, i.e. the exploitation of various types of biomass or/and from different sources, aiming at reducing the storage space requirements. Another study has also proved that the multi-biomass concept may lead to significant system cost reduction (Nilsson and Hansson, 2001). Detailed description of storage methods as well as data for the cotton biomass behaviour and composition during and after each one of these procedures can also be found in McGowin and Wiltsee (1996) and Huisman et al. (2000).

Transport The transport element of the biomass supply chain links together all the activities that

have to take place between the point of production through to the point of use at the energy conversion facility and the locations at which they occur. Specifically, after the harvesting and processing of the material on first stage, in-field/forest transport takes place to move the biomass to a point where road transport vehicles can be used. Once the biomass has been moved to the roadside it will either have to be stored for some time or be directly transferred and loaded to road transport vehicles for transferring to the plant, where it has to be unloaded.

The transportation costs of supplying biomass to energy production facilities are mainly a function of the distance over which the material has to be moved, the type of transportation means selected to be used (trucks, ship or train), the type of biomass and the form in which it is transported (e.g. chopped or coppiced timber, compared with baled cereal straw), as well as the time spent for loading and unloading vehicles. For example, biomass fuels with relatively high bulk densities (such as coppice and forestry residue chips) are likely to require fewer vehicle movements to deliver a specified tonnage to a power station than biomass with lower bulk densities (such as miscanthus and straw). Moreover, the size of the storage facility either on an intermediate location or at the power plant affects the transport arrangements. A power station with a relatively small on-site stock level (e.g. a few days’ supply) will require more frequent, evenly spread deliveries than a plant with a large storage capacity. Low levels of stockholding at the power station will increase the importance of reliable and flexible transport (Allen et al., 1998). Furthermore, using heavy goods vehicles (rather than agricultural or forestry equipment) for transport to the power station is likely to be essential due to the average distance from farms to power station, and the carrying capacity and road speed of such vehicles, increasing further the total transportation cost. Finally, the catchment area for the biomass collection points and hence the transport distance over which biomass has to be moved depends on a number of factors. These include the size of the facility and the conversion technology used and thus, the quantity of biomass fuel required, the crop yield that is achieved, and the availability of the material for biomass resource.

Considering the typical locations of biomass fuel sources (i.e. in farms or forests) the transport infrastructure is usually such that road transport will be the sole potential mode for collection and transportation of the fuel. Additional factors that reinforce the use of road transport include the relatively short distances over which the fuel is transported and the greater flexibility that road transport can offer in comparison with other modes (Rentizelas et


al., 2009b). Other transportation means, such as ship or train may be considered when long distance biomass transport is examined (Hamelinck et al., 2005). According to the last authors, various studies have shown that long-distance international transport by ship is feasible in terms of energy use and transportation costs but the availability of suitable vessels and weather conditions (e.g. winter time in Scandinavia and Russia) need to be considered. However, local transportation by truck may be a high cost factor, which can influence the overall energy balance and total biomass costs. Harbour and terminal suitability to handle large biomass streams can also hinder the import and export of biomass to certain regions. Finally, the most favourable situation is when the end user has the energy production facility close to the harbour avoiding additional transport by trucks (Junginger et al., 2006).

Energy Production Different technological processes can be used to obtain the various energy products from

biomass. Most biomass used for energetic purposes is directly combusted to produce heat and/or power, but a huge variety of additional possibilities are available to provide environmentally sound heat and/or electricity as well as transportation fuels from organic material (McKendry, 2002a; Kaltschmitt et al., 2004; McKendry, 2002b). The purpose of biomass conversion is to provide fuels with clearly defined characteristics that can meet given fuel quality standards. The most important conversion options, as presented by Kaltschmitt et al. (2004) are depicted schematically in Figure 2.

In brief, thermo-chemical conversion processes convert biomass into a solid, liquid or gaseous fuel, (e.g. gasification, pyrolysis and charcoal production). The most significant options of bio-chemical conversion are alcohol production from biomass containing sugar, starch and/ or celluloses and biogas production from organic waste material (e.g. animal manure). Finally, physical-chemical conversion processes provide liquid fuels (e.g. biodiesel) through physical (e.g. pressing) and chemical (e.g transesterification) processing of dedicated energy crops. According to Demirbas et al. (2009) the main biomass processes that are expected to be utilized in the future in industrialized countries, are the direct combustion of residues and wastes for electricity generation, ethanol and biodiesel as liquid fuels, and combined heat and power production from energy crops. The future of biomass electricity generation lies in biomass integrated gasification/gas turbine technology which offers high-energy conversion efficiencies.

The choice of conversion process depends mainly upon the type and quantity of biomass feedstock, the preferred energy product, as well as environmental and economic issues. Raw products differ mainly in their suitability for different production processes, but also in their regional availability and their conversion costs according to their physical attributes. Consequently, it is important to obtain global insights about the effects of all these technological options on waste biomass supply chains; such understanding would allow the identification of optimal configurations for bio-energy supply systems, as well as of meaningful improvement options. As it is beyond the scope of this chapter to analyze in more detail energy conversion processes, the reader could consult state-of-the-art literature on this field, such as Kaltschmitt et al. (2004), Mitchell et al. (1995), Ravelli et al. (2008), Kirubakaran et al. (2009), Yanik et al. (2007), Kobayashi et al. (2008) and Wang and Chen (2007).


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Figure 2. Overview of renewable energy production from organic substrates (Kaltschmitt et al., 2004).

Key Variables and Characteristics

Biomass supply chains present several distinctive characteristics that differentiate them

from traditional supply chains, as described in subsection 3.1. The primary features that should be considered, when designing waste biomass supply networks for energy production, are summarized below:

Seasonality of biomass. Agricultural biomass types are usually characterized by seasonal availability, and thus there is a need of storing large amounts of biomass for a significant time period resulting in high holding costs, if year-round operation of the power plant is desired. The multi-biomass approach, as long as products have similar characteristics and fuel properties, may smooth significantly problems that stem from seasonality (see subsection 3.3 for additional analysis of such systems).

Variability of biomass production quantities and dispersed geographical distribution. As for all agricultural products, weather related variability and competing uses of biomass in a dynamically changing market have to be considered when determining the flows of material supply network, as the final amount of product available for procurement deviates from the predicted one.

Perishability of biomass. The complexity of biomass supply chains is even higher for perishable biomass products, where the transportation time of the products through the supply


chain and the opportunities to use inventory as a buffer against demand and transportation variability are severely limited.

Low density of biomass. Most forms of biomass and bioenergy carriers tend to have a relatively low energy density per unit of volume (e.g. GJ/m3) or mass (e.g. MJ/kg) compared with fossil fuels with the same energy equivalent. For example, ethanol has an energy content of ~22 MJ/l whereas gasoline is ~34 MJ/l; air dried woody biomass is around 12-15 GJ/t and sub-bituminous coal around 20-25 GJ/t (low heat values). This often makes handling, storage and transportation more costly per unit of energy carried.

Stochasticity of energy demand. Biomass supply chains need to be robust and flexible enough to adapt to unpredicted changes in market conditions, as the demand of the finally produced energy depends on the type of the conversion facility, the price of competitive fuel substitutes or other unexpected events that may occur during the production period.

Interdependencies of logistics operations. Upstream decision-making for the several activities that take place within biomass supply chains affects later activities in the chain and the interdependence between them is very strong. Allen et al. (1998) provide a representative example of the degree of interdependence among the logistics operations taking place in such networks, discussing the interdependency of harvesting, storage and transportation methods in the case of forest trees supply chains.

Taking all above into consideration, it is evident that there is need for a holistic supply chain perspective when planning any single activity in the chain rather than considering that activity in isolation. The harvesting approach fundamentally affects the storage, handling and transport requirements in the supply chain. On the other hand, when the supply system is designed from the other end of the chain as is common, the choice of power station technology, size and location dictates how all the upstream activities should be conducted so that biomass arrives at the conversion facility at the correct time, in the correct quantity, and at the desired quality. Theoretically, a large number of bioenergy chains can be envisioned. It is important to obtain insights in the effects of all logistics variables on the total cost and energy consumption of bioenergy chains. This would allow for the identification of best configurations for bioenergy supply systems, as well as for improvement options.

The key variables of biomass logistics systems have been identified in specific studies, investigating strategically the interdependencies between them and their effect on supply chain efficiency and cost. Their analysis could support strategic and tactical decision-making on biomass supply chains. Mitchell et al. (1995) provide a techno-economic assessment of biomass to energy and investigate the interrelationships between the stages in the supply chain. Allen et al. (1998) address the supply-chain considerations and costs of using biomass fuel on a large scale for electricity generation at power stations, recognizing the importance of logistics planning and management facets. An analytic supply chain modeling for five biomass types was performed, concluding that 20–50% of the biomass delivered cost is due to transportation and handling activities. Nilsson and Hansson (2001) examine the influence of various machinery combinations, fuel proportions and storage capacities on costs for co-handling of straw and reed canary grass to district heating plants.

Hamelinck et al. (2005) study for the first time systematically the influence of various parameters on the performance of complete transport chains, analyzing a generic international scenario that assumes five possible transfer points: the production site, a central gathering point (CGP), two transport terminals (export and import) and the energy plant. Caputo et al. (2005) investigate the economic profitability of biomass utilization for the direct production


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of electric energy taking into account the critical logistics aspects related to the overall bio-energy chain as well as the impact of the main logistics variables on the economics of such systems. Finally, Tatsiopoulos and Tolis (2003) present a model, which simulates the cotton biomass supply chain. Their study examines the feasibility and the problems that arise while trying to organize an integrated logistics network. Also, economic aspects of other logistics procedures like collection and warehousing are also investigated.

Multi-Biomass Systems The concept of multi-biomass utilization has captured the interest of researchers because

of its potential benefit on the total system cost. The work by Nilsson and Hansson (2001) is indicative of the cost reduction potential of the multi-biomass approach. The authors investigate the simultaneous use of straw and reed canary grass and conclude that the specific combination led to a total system cost reduction of about 15–20% compared to a single-biomass case, despite the increased production cost of reed canary grass compared to straw. The cost of producing energy using all the available biomass types in a certain region is determined by Voivontas et al. (2001). A case study for utilizing multiple forest biomass types for local district heating applications is presented by Freppaz et al. (2004), using GIS for logistics modeling. De Mol et al. (1997) study the multiple-biomass approach and discuss the benefits of employing an optimization - instead of a simulation - model to decide the optimal mixture of biomass types. Moreover, Hamelinck et al. (2005) acknowledge in their study the need for widening the operational window of biomass logistics by combining multiple biomass chains to minimize the share of capital costs. Frombo et al. (2009) develop an Environmental Decision Support System in which the woody biomass resources are partitioned into forest and non-forest resources.

Significant savings from the multi-biomass approach can also be realized in the stage of storage, as the inflow of biomass throughout the year may be smoother and the storage space required may be reduced. Furthermore, additional cost savings can be expected from smoother equipment and labour resource requirements at the biomass supply chain. Rentizelas et al. (2009b) compare three biomass storage solutions found in the literature, in terms of total system cost, adopting the multi-biomass approach by considering two locally available biomass types (cotton stalks and almond tree prunings). The authors conclude that multi-agricultural biomass approach appears to be attractive for systems where expensive storage solutions are used, in order to reduce the storage space required.

However, the concept of multi-biomass utilization has been scarcely investigated by researchers up to now due to the associated complexity. According to Faaij et al. (1997), organizational aspects, variations in availability, storage and backup fuel especially in winter months, are issues that require more detailed study. An interesting research examining the case of utilizing six biomass sources to identify the optimum biomass fuel mix, including municipal solid waste and the criterion for the technical capability of using the biomass mix is presented by Papadopoulos and Katsigiannis (2002).

Most biomass types can be processed into numerous forms, each one potentially requiring different equipment for handling, loading, unloading, transport and fuel feeding. Thus, it is important for the multi-biomass approach that all the potential sources may be processed in a form that will allow the use of only one type of handling and feeding


equipment or that will require small, inexpensive and easily made modifications and customizations.

One of the main technical challenges of the multi-biomass approach is the ability of the available energy conversion technology to use a fuel mix comprised of several biomass types with varying fuel characteristics, or a fuel that will vary its characteristics according to the season of the year. It is therefore essential that the selection of the biomass conversion technologies established on the production facility is made in conjunction with the selection of biomass suppliers. The different biomass types are characterized by a set of physical/chemical parameters that influence the efficiency of the various processes (McKendry, 2002a). Some technologies are more flexible in biomass characteristics variation (e.g. fluidized bed combustion) as opposed to others (e.g. pyrolysis), and some types of biomass have very similar characteristics whereas others may have totally different. However, there are technologies capable of coping with the simultaneous use of biomass types (Faaij et al., 1997).

There exist several families of biomass types that have very similar characteristics and fuel properties (e.g. woody biomass types, several cereal biomass types, etc.) and this has to be considered when designing specific multi-biomass supply chain networks. For example, Rentizelas et al. (2009b) assume in their case study that a suitable technology is considered to use the fuel mix that may result from the locally available biomass sources of the case study region. In another study the same authors present a decision support system (DSS) for multi-biomass energy conversion applications. The presented model is designed to incorporate parametrically a large number of biomass types. The outcome identifies the type and quantity levels of biomass that should be selected to optimize the financial yield (Rentizelas et al., 2009a).

Environmental Impact of BSCs The environmental impact of biomass fuel supply is of great importance as the rationale

driving the use of biomass fuel is that it is less harmful to the environment than traditional fossil fuels (Allen et al., 1998). The environmental benefits and energy production that results from using biomass fuel should at least outweigh the environmental impacts and resource consumption that their growth and supply incur. The most logistically efficient supply chain will not necessarily provide the best benefit to cost ratio in environmental terms.

Most activities that take place in biomass supply chains can be responsible for a significant proportion of the total energy use and the environmental impacts that arise in the biomass supply chain, like traffic generation, vehicle emissions, vehicle noise, visual intrusion and health and safety of workers and the public. Such activities include harvesting with various types of equipment using fuels, transportation with many vehicle movements, storage of perishable products for long time period and production of energy through technologies more or less friendly to the environment. Transportation is considered to have the most important impact on the environment and thus decisions regarding vehicle selection, routing and scheduling should be taken with respect to the total emissions estimated to be released during the networks lifetime. According to Allen et al. (1998), public perception often proves to be a significant factor in the acceptability and future development of an industrial or commercial activity and can influence location choices, land-use and transport


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planning decisions. Transport activities should therefore be planned as efficiently as possible in order to minimize their environmental impacts.

Moreover, interdependencies among biomass logistics operations affect the decisions regarding the environmental impact of a biomass supply chain. For instance, even if an alternative approach to storage and transport is known to be less harmful to the environment, the chosen harvesting system can preclude its selection.

As far as the environmental impact of waste biomass conversion to energy is concerned, when biomass is burned it releases carbon dioxide to the atmosphere in exactly the same way as the combustion of a fossil fuel does. However, the growth of an equivalent quantity of biomass absorbs the same amount of CO2 from the atmosphere, thus leading to zero contribution to atmospheric CO2 concentration in total. Moreover, biomass residues resulting from agriculture and urban living have traditionally been allowed to decompose. This decomposition leads to the significant release of methane, a more potent greenhouse gas than CO2, whereas burning waste in a biomass power plant prevents this methane release.

HIERARCHICAL DECISION-MAKING FRAMEWORK The structure of the global market for biomass and the associated supply chains is

evolving quite dynamically. Traditionally, biomass has been used for energy (mainly thermal) production in areas close to its production sites. However, an emerging practice for energy producers is to procure biomass from several suppliers to develop the critical mass necessary to develop an efficient energy production facility. The increased complexity of this system dictates the need for adopting more sophisticated supply chain planning and coordination methodologies that have been successfully used in traditional supply chain management, for which there is extensive literature (e.g. Min and Zhou (2002), Vidal and Goetschalckx (1997), Sarmiento and Nagi (1999) and Meixell and Gargeya (2005)).

Assessing BSCs for energy production involves a complex hierarchy of decision-making processes. Implementing the well-established conventional supply chain practices to BSCs is not necessary prudent since such networks are characterized by significant supply and demand uncertainty, as well as by perishable, often bulky, seasonal products (see also discussion in Section 3). Furthermore, in order to adequately plan BSCs’ operations it is necessary to develop specific planning models that capture issues such as harvesting policies, marketing channels, logistics activities, vertical coordination and risk management. Actually, few of these issues resemble to the ones appearing in the supply chain management of fresh agricultural products (Epperson and Estes, 1999). Iakovou et al. (2009) present a holistic approach that takes into account all major technological and managerial aspects in design and execution of waste biomass supply chains developed for energy production.

Recognizing the natural hierarchical decision-making process for the design and planning of BSCs and taking into account the existing academic research and industrial practices, we propose the comprehensive hierarchical decision-making framework exhibited in Figure 3. All issues that need to be addressed by the relevant stakeholders (such as system regulators, investors, decision-makers and planners) at the strategic, tactical and operational level are mapped in this framework. We proceed by discussing the decisions at each level of the hierarchy, while presenting the relevant research efforts.


Figure 3. Hierarchy of Decision Making for BSCs

Strategic Decisions

Decisions at the strategic level of decision making include: selection of suppliers /

collection sites, procurement of multiple types of biomass, ensuring long-term biomass supply and demand, sitting and optimal capacity of conversion facilities, allocation of storage facilities, network building, choice of suitable energy conversion processes, selection of collection, pre-treatment and storage methods, outsourcing of logistics operations and timing of pre-treatment. At this level, most decisions affect operations and impose a set of constraints to the lower decision-making levels. These decisions are discussed below.

Ensuring Long-Term Supply and Demand The global effort for the usage of biomass energy has led to a policy environment that is

defined by various regulatory interventions and stimulation measures, such as governmental R&D programs, tax cuts and exemptions, investment subsidies, feed-in tariffs for renewable


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electricity, mandatory blending for biofuels or biofuel quotas. However, these measures are mostly temporary and myopic in nature, and often the lack of a stable system discourages long-term serious investments. Thus, the stabilization of the external environment, sufficient biomass resources and a well-functioning biomass market that can assure reliable, sustainable, and lasting biomass supplies are crucial preconditions for the development of sustainable bioenergy systems.

Van Dam et al. (2005) discuss policies for securing renewable resource supplies for changing market demands in a bio-based economy. The authors suggest that the development of a sustainable bio-based economy requires a joint effort from the agricultural sector, industries, governments and consumer organisations, fully utilising the available scientific infrastructure and multidisciplinary expertise. Junginger et al. (2006) examine the opportunities and barriers in the context of securing sustainable bio-energy trade. A detailed analysis is carried out by Koopmans (2005) to determine the sustainability of biomass energy demand and supply in sixteen Asian countries. Nagel (2000) points out that as a result of the currently lower fossil fuel prices and the higher investment and operating costs of biomass-fired plants, the energy use of biomass is case-dependent. The author further documents that different factors can improve the economic viability of bio-energy systems, especially fuel prices/rates of fossil and biogenic fuels, sales of biogenic produced electricity, the investment costs for biomass-fired heating plants as well as co-generation plants. McCormick and Kåberger (2007) propose strategies including policy measures for altering the economics of bio-energy, pilot projects to stimulate the learning processes and guidance for network building and supply chain coordination.

An essential step in proceeding with the often large investment necessary for developing biomass conversion facilities is ensuring the uninterrupted supply of adequate biomass, as well as the critical mass of demand over the strategic horizon. To that end, contractual agreements that guarantee long-term supply and demand, while spreading “equitably” total profit among the supply chain partners from agriculture and forestry to energy consumers can be of great value. Various contract models have been presented in literature, which differ based on the contractual clauses between the buyers (retailers or manufacturers) and the sellers (suppliers) (Tayur et al., 1999). Several authors in the field of agricultural science discuss contracting with farmers, such as Key and MacDonald (2006), Hovelaque et al. (2009), Ligon (2003), Mathews (2008), Poole et al. (1998), Roumasset (1995), and Roumasset and Lee (2007). Kumar et al. (2002) discuss and propose methods for estimating the monetary value of agricultural residues used as biofuels, defining the minimum amount that a farmer has to be paid as well as the upper limit up to which the energy end-user can pay for the agricultural residues.

Design of BSC Networks The logistics network design is one of the most comprehensive strategic decision

problems that need to be optimized for the long-term efficient operation of BSCs. The configuration of BSC networks is comprised of critical decisions that affect the biomass flow and the associated costs. These refer to the identification of collection sites, potential procurement of a single or multiple types of biomass, purchasing quantities from each supplier, allocation and optimal capacity of intermediate warehouses and energy conversion


facilities, while taking into account key parameters such as the capacity limit of supply nodes or the potential fixed capacity of an existing power plant. The objective is to design or reconfigure a logistics network so as to minimize annual system wide costs, including harvesting, collection or purchasing costs, facility (storage, handling and fixed) and inventory holding costs, and transportation costs, subject to variety of service level requirements. The capacities and allocations decided on strategic level then become constraints in the aggregate planning that takes place on tactical decision making level. However, the supply chain configuration not only has to be efficient with respect to the expected conditions but also robust and flexible enough to adapt to potential changes in these conditions on the long run.

Selection of Collection Sites / Suppliers. The rather dispersed geographical distribution of significant biomass potential has raised the interest of researchers that either gather information about the available biomass through bibliographic study and other data sources (Skoulou and Zabaniotou, 2007) or use Geographical Information Systems (GIS). GIS have been widely used in existing literature for the evaluation of the biomass supply and characteristics, the selection of collection sites, or even the estimation of the transportation cost to existing power plants. For example, Voivontas et al. (2001) propose a GIS-based decision supporting tool to identify the geographic distribution of the economically exploited waste biomass potential for power production. Noon and Daly (1996) estimate the costs for supplying wood fuel to any one of its 12 coal-fired power plants, and Singh et al. (2008) make an attempt to evaluate the spatial potential of biomass and a mathematical model for collection of biomass in an Indian state. Certain studies assess the manure potential for energy production (Ma et al., 2005; Batzias et al., 2005; Dagnall et al., 2000). Ramachandra et al. (2004) propose a Decision Support System (DSS) for regional biomass assessment considering the resources available and deterministic demand. Kinoshita et al. (2009) address the widespread adoption of woody biomass energy by presenting a cost model, focusing on cost-effective harvesting methods costs.

Selection of Biomass Types for Procurement. Another strategic decision that has to be made when designing a BSC is whether it is more profitable to utilize multiple types of biomass for energy production than a single type. The exploitation of various types of biomass from different sources has captured the interest of certain researchers because of its potential benefit on the total system cost (Nilsson and Hansson, 2001; Voivontas et al., 2001; Freppaz et al., 2004; De Mol et al., 1997; Frombo et al., 2009, Rentizelas et al., 2009a; 2009b). Rentizelas et al. argue that the multi-agricultural biomass approach appears to be attractive for systems where expensive storage solutions are used, in order to reduce the storage space required (see discussion in subsection 3.3).

Allocation of Energy Production Facilities. The allocation and the optimal capacity of energy production facilities have attracted the interest of several authors. To allocate conversion facilities researchers tend to use GIS-based methodologies. Panichelli and Gnansounou (2008) present a methodology that tackles the competition of various energy facilities through an allocation model based on least-cost biomass quantities. Graham et al. (1997) examine the effect of location and facility demand on the marginal cost of delivered wood chips from energy crops. Shi et al. (2008) evaluate the feasibility of setting up new biomass power plants and optimizing the locations of plants in a Chinese region and Zhan et al. (2005) investigate the economic feasibility of locating a switchgrass-to-ethanol conversion facility in Alabama. Another tool for locating conversion facilities is proposed by Papadopoulos and Katsigiannis (2002), while considering economic criteria for assessing the


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sustainability of the installation. Tembo et al. (2003) use an integrated mixed integer-programming model to determine the most economical source of biomass and the optimal biorefinery location that maximizes net present profit for a biomass-to-ethanol system. A methodology for the optimization of the installation of new biomass energy systems on a regional level is presented by Dornburg and Faaji (2001).

Optimal Capacity of Energy Production Facilities. An analytical framework for determining the optimal power plant size and the derivation of supply curves is presented by Gan (2007). Jenkins (1997) and Nguyen and Prince (1996) discuss the optimal sizing of a biomass utilization facility. The power cost and optimum plant size for power plants using three biomass fuels in western Canada are determined by Kumar et al. (2003), including agricultural residues and taking into consideration costs of loading and unloading. Bakos et al. (2008) develop an ‘energy-planning’ model that determines the number of biomass-fuelled power installed in a given area based on available biomass from agricultural residues in the island of Crete, Greece. Celma et al. (2007) study the waste-to-energy possibilities of the industrial olive and wine-grape by-products in Extremadura, whereby specific costs are analyzed assuming the products’ use in a centralized power plant, while taking into account logistics components. Freppaz et al. (2004) develop a decision support system for locating plants and computing their optimal capacity. Nagel (2000) formulates a problem to determine whether to construct or not a district heating network, a heating plant or a co-generation plant using information regarding the consumers’ annual heat consumption, as well as its seasonal distribution.

Allocation of Storage Facilities. The allocation of storage facilities is of critical strategic importance when designing a BSC. Certain authors examine the option of on-field biomass storage (Allen et al., 1998; Huisman et al., 1997; Sokhansanj et al., 2006; Cundiff et al., 1997), the use of intermediate storage locations (Allen et al., 1998; Nilsson and Hansson, 2001; Tatsiopoulos and Tolis, 2003) or the option of settling the storage facility next to the biomass power plant (Tatsiopoulos and Tolis, 2003; Papadopoulos and Katsigiannis, 2002). Rentizelas et al. (2009b) compare these three biomass storage solutions in terms of total system cost (see subsection 3.1.2).

Network Design. Several authors study the design of integrated biomass supply chains. An optimization model has been developed by De Mol et al. (1997) to optimize the network structure and the mixture of biomass types supplied to the energy plant. Rentizelas et al. (2009a) develop a simulation and optimization model to maximize the net present value (NPV) of the investment for bio-energy supply system’s lifetime, and decision variables include the optimum location and capacity of the bioenergy facility, as well as the types and optimal quantities of biomass that have to be procured. Tatsiopoulos and Tolis (2003) present a comparison for cotton-stacks supply chain methods and examine the feasibility and the problems that arise while trying to organize an integrated logistics network and optimize its transportation economy. Gronalt and Rauch (2007) describe a novel approach for configuring a wood biomass supply network for a certain region, providing their evaluation method for designing regional forest fuel supply networks. Frombo et al. (2009) present the application of the Environmental Decision Support System (EDSS) for agro-forest biomass use for energy production at a strategic level, in which the plant location is fixed and the variables to be optimized are the plant capacity and the quantity of material to be harvested in a specific location.


Selection of Energy Production Technologies The conversion of waste biomass and organic substrates into energy encompasses a wide

range of different types and sources of biomass, conversion options, end-use applications and infrastructure requirements. Factors that influence the choice of a conversion process include the type and quantity of biomass feedstock and the desired form of the produced energy, i.e. end-use requirements, environmental standards, economic conditions and other project-specific factors. Based primarily upon the biomass moisture content, the type of biomass selected subsequently dictates the most likely form of energy conversion process. High moisture content biomass, such as the herbaceous plant sugarcane, requires a ‘wet’ conversion process that involves fermentation, while a ‘dry’ biomass such as wood chips, is more economically suited to gasification, pyrolysis or combustion. However, there are additional factors which must be taken into consideration when determining the selection of the conversion process, apart from simply moisture content (McKendry, 2002a).

Several authors have included bioenergy conversion facility in their biomass supply chain modelling efforts. Indicatively, the results from using two biomass-to-electricity conversion technologies, a C/ST (fluidized bed combustion with steam turbine) and G/CC (fluidized bed gasification with combined gas–steam cycle), is compared by Caputo et al. (2005), concluding that 56–76% of the total system operational costs are due to the biomass logistics, thus indicating the potential for cost reduction. A comparative economic evaluation of various bioenergy conversion technologies was conducted by Mitchell et al. (1995), using a comprehensive biomass-to-electricity and ethanol model. Frombo et al. (2009) present, a geographic information system (GIS)-based Environmental Decision Support System (EDSS) for the optimal planning of forest biomass use for energy, structured properly to encompass different energy conversion technologies (pyrolysis, gasification or combustion) in the system. The International Energy Agency provides an overview of the perspectives for bioenergy processes combined with main biomass resources, as well as a summary of estimates for costs of various fuels that can be produced from biomass (IEA Bioenergy, 2007).

Balancing the Financial and Environmental Impact Sustainability of logistics operations is a critical issue that has to be taken into account

when designing and executing biomass supply chain networks for energy production. Thus, a comprehensive cost-benefit analysis that includes the environmental impact of the adopted technologies and transportation means is necessary. To that end, Forsberg (2000) presents a biomass distribution system investigating the resulting environmental load profiles of several bioenergy chains. Hamelinck et al. (2005) analyze a generic international logistic scenario that assumes five possible transfer points. In a modular approach the costs, energy use and CO2 emissions of each step in the selected chains were calculated. Frombo et al. (2009) suggest that running the strategic logistics model they develop for various technological options, the user can obtain the optimal results for combustion, gasification, and pyrolysis processes and compare results on the basis of economic and environmental considerations.

Elghali et al. (2007) develop a sustainability framework for the assessment of bioenergy systems to provide practical advice for policy makers, planners and the bioenergy industry,


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using multi-criteria decision analysis. Several other studies have recently been published, addressing the critical issue of designing and evaluating sustainable supply chains, in which profitability and environmental impacts are balanced (Linton et al., 2007; Neto et al., 2008, 2009).

Tactical and Operational Decisions As decision-making on the tactical and operational level for BSCs is similar to that of

traditional supply chain management, the related discussion here is in brief. The tactical level includes medium-term decisions such as aggregate planning, inventory management or fleet management. The operational level includes day-to-day decisions, such as inventory control, or second-stage pre-treatment operations into the facility.

Aggregate Production Planning Aggregate production planning in BSCs is concerned with the tactical determination of

production, inventory, and work force levels to meet energy demand requirements over a mid-term planning horizon. Computational stochastic simulation models are presented for exploiting forest-biomass (Gallis, 1996), cotton residue (Gemtos and Tsiricoglou, 1999) and herbal biomass (Huisman et al., 1997). De Mol et al. (1997) develop a simulation - optimization model to calculate energy consumption and cost to transport biomass from its source to its conversion plant. Cundiff et al. (1997) design a biomass delivery system that considers systems-related issues associated with the harvest, storage, and transport of herbaceous biomass from on-farm storage locations to a centrally located plant. A dynamic simulation model for baling and transporting wheat straw by Nilsson analyses a hypothetical straw-to-energy system for district heating plants in Sweden (Nilsson, 1999a; Nilsson, 1999b). Dornburg and Faaij (2001) study a mathematical model which analyses and processes past data of biomass distribution cases using linear or exponential regression models in order to predict and solve a similar biomass distribution problem. Hansen et al. (2002) develop a simulation model of sugar cane harvest and mill delivery in South Africa, whereas Tatsiopoulos and Tolis (2003) simulate a cotton biomass supply chain to find biomass delivery schedule. Moreover, Sokhansanj et al. (2006) develop a framework of a dynamic integrated biomass supply analysis and logistics model to simulate the collection, storage, and transport operations for supplying agricultural biomass to a biorefinery and Kumar and Sokhansanj (2007) use this model to evaluate switchgrass delivery system. Ravula et al. (2008b) simulate the transportation system of a cotton gin, using a discrete event simulation model, to determine the operating parameters under various management practices, while they provide a comparison between two policy strategies for scheduling trucks in a biomass logistics system (Ravula et al., 2008a).

Only a few research papers address inventory management and control, only a few research papers attempt to tackle this field (Tembo et al., 2003; Tatsiopoulos and Tolis, 2003; Gallis, 1996). The key variables of biomass logistics systems are addressed in three other studies, investigating strategically the interdependencies between them and their effect on supply chain efficiency and cost (Hamelinck et al., 2005; Caputo et al., 2005; Hamelinck et


al., 2003). Furthermore, Allen et al. (1998) address the supply chain considerations and costs of using biomass fuel on a large scale for electricity generation at power stations, recognizing the importance of logistics planning and management facets.

Selection of Collection, Storage, Pre-Treatment and Transportation Methods Selection, procurement or design of collection, storage, pre-treatment or transportation

methods are tactical decisions (or even strategic in cases of strong technological interdependence of the operations) that the research community has studied for specific biomass raw materials, such as switchgrass (Cundiff and Marsh, 1996), forest fuel (Eriksson and Björheden, 1989), cotton plant residues (Fischer and Gaderer, 2000; Gemtos and Tsiricoglou, 1992), herbaceous biomass in general (Cundiff and Grisso, 2008), logging residue (Nurmi, 1999) and corn stover (Shinners et al., 2007). McGowin and Wiltsee (1996) analyze several biomass treatment methods. Huisman et al. (2000) provide a generalized comparison of bale storage systems for biomass, whereas Rentizelas et al. (2009b) review research relevant to biomass storage and analyze three biomass storage methods, while applying the latter to a case study and presenting tangible comparative results.

During harvest, some of the decisions that need to be made include the timing for collecting the crops from the fields and the determination of the level of resources needed to perform this activity. Some other decisions made at harvest include the scheduling of equipment, labor, and transportation equipment. Jiao et al. (2005) present a harvest-scheduling model for a region in Australia with multiple independent sugar cane fields. Recio et al. (2003) embe a mixed integer program into a decision support system (DSS) that provides detailed plans for farmers’ activities such as crop selection, scheduling of field tasks, investment analysis, machinery selection and other aspects of the production process. Higgins and Neville (2002) develop models to deal with operational decisions for scheduling harvesting operations. Ferrer et al. (2008) determine a plan for the optimal scheduling of the harvest of wine grapes using an LP model with the objective of minimizing operational and grape quality costs.

Another critical decision is the most effective timing of the material’s pre-treatment and specifically whether it will take place before or after its transportation (e.g. production of wood chips, pellets and other compressed forms to facilitate the transportation and storage of biomass). De Mol et al. (1997) present a cost optimization mathematical model that determines biomass flows in multi-biomass supply chain networks, as well as the technical and economical feasibility of pre-treatment at the optimal energy conversion sites for each biomass type.

MATCHING OF THE PROPOSED FRAMEWORK WITH THE EXISTING RESEARCH

Our analysis has clearly demonstrated that biomass energy production is a rapidly

evolving research field. Table 1 displays matching of the critical waste biomass supply chain


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decisions identified in Section 4 with the relevant research efforts. This classification can be used to identify overlaps and gaps in the existing literature.

Table 1. Matching of the Proposed Framework with Existing Research

Decisions References

Collection

Selection of Collection Sites Skoulou and Zabaniotou (2007), Voivontas et al. (2001), Noon and Daly (1996), Singh et al. (2008), Ma et al. (2005), Batzias et al. (2005), Dagnall et al. (2000), Kinoshita et al. (2009), Ramachandra et al. (2004)

Exploitation of Multiple Types of Biomass

Nilsson and Hansson (2001), Voivontas et al. (2001), Tembo et al. (2003), Freppaz et al. (2004), De Mol et al. (1997), Frombo et al. (2009), Rentizelas et al. (2009a and 2009b)

Selection or Design of Harvesting Methods and Equipment

Cundiff and Marsh (1996), Gemtos and Tsiricoglou (1992), Shinners et al. (2007), Cundiff and Grisso (2008), Jiao et al. (2005), Recio et al. (2003), Higgins and Neville (2002), Ferrer et al. (2008)

Pre-treatment Selection or Design of Equipment Eriksson and Björheden, (1989); Cundiff and Grisso (2008)

Timing of Pre-treatment De Mol et al. (1997)

Transportation

Fleet Management Eriksson and Björheden (1989) Vehicle Planning & Scheduling Ravula et al. (2008a)

Outsourcing Tatsiopoulos and Tolis (2003)

Storage

Allocation of Storage Facilities

Allen et al. (1998), Huisman et al. (1997), Sokhansanj et al. (2006), Cundiff et al. (1997), Nilsson and Hansson (2001), Tatsiopoulos and Tolis (2003), Papadopoulos and Katsigiannis (2002), Rentizelas et al. (2009b)

Selection of Storage Methods

Gemtos and Tsiricoglou (1992), Cundiff and Marsh (1996), Shinners et al. (2007), Cundiff and Grisso (2008), Eriksson and Björheden (1989), McGowin and Wiltsee (1996), Fischer and Gaderer (2000), Nurmi (1999), Huisman et al. (2000), Rentizelas et al. (2009b)

Inventory Management & Control Tembo et al. (2003), Gallis (1996), Tatsiopoulos and Tolis (2003)

Energy Conversion

Allocation of Conversion Facilities

Panichelli and Gnansounou (2008), Graham et al. (1997), Shi et al. (2008), Zhan et al. (2005), Papadopoulos and Katsigiannis (2002), Tembo et al. (2003), Dornburg and Faaij (2001), Tatsiopoulos and Tolis (2003), Rentizelas et al. (2009a), Freppaz et al. (2004)

Optimal Size/Capacity & Number of Plants

Gan (2007), Jenkins (1997), Nguyen and Prince (1996), Kumar et al. (2003), Tembo et al. (2003), Bakos et al. (2008), Celma et al. (2007), Freppaz et al. (2004), Nagel (2000), Rentizelas et al. (2009a), Frombo et al. (2009)

Aggregate Production Planning

Gallis (1996), Huisman et al. (1997), De Mol et al. (1997), Cundiff et al. (1997), Gemtos and Tsiricoglou (1999), Nilsson (1999a), Nilsson (1999b), Dornburg and Faaij (2001), Hansen et al. (2002), Tembo et al. (2003), Tatsiopoulos and Tolis (2003), Sokhansanj et al. (2006)

Conversion Technologies Installed

e.g. McKendry (2002a), Kaltscmitt et al. (2004), Caputo et al. (2005), Mitchell et al. (1995), Frombo et al. (2009)

Design of BSCs

Nagel (2000), Cundiff et al. (1997), De Mol et al. (1997), Tatsiopoulos and Tolis (2003), Tembo et al. (2003), Gronalt and Rauch (2007), Gan (2007), Frombo et al. (2009), Ayoub et al. (2007), Freppaz et al. (2004), Rentizelas et al. (2009a)

Ensuring Long-term Supply and Demand

van Dam et al. (2005), Junginger et al. (2006), Koopmans (2005), Nagel (2000), McCormick and Kåberger (2007), Tayur et al. (1999), Key and MacDonald (2006), Hovelaque et al. (2009), Ligon, (2003), Mathews (2008), Poole et al. (1998), Roumasset (1995), Roumasset and Lee (2007), Kumar et al. (2002)

Balancing the Financial & Environmental Profit

Forsberg (2000), Hamelinck et al. (2005), Frombo et al. (2009), Elghali et al. (2007), Linton et al. (2007), Neto et al. (2008, 2009)

Symbols: S for Strategic, T for Tactical, O for Operational


Although the vast majority of the studies in the field of biomass-to-energy production examine the system from a purely technological or ecological point of view, there is a subset of the literature body that addresses the relevant and highly critical supply chain management issues. In fact, it is evident that the published works on BSCs have increased significantly during the last decade, indicating the increased importance of the efficient design and evaluation of sustainable biomass supply chain networks on a global level.

As exhibited in Table 1, the current research captures only a subset of the decisions needed to be taken at a strategic, tactical and operational level and focuses mainly on the first and the last level of BSCs, i.e. the collection of biomass and the energy production. More specifically, there is a plethora of literature findings regarding the assessment of biomass potential, the selection of collection sites and the allocation and optimal capacity of the energy conversion facilities. However, only a few of the existing research papers tackle the biomass supply chain network design systemically. In addition, despite the fact that sustainability of supply chains in general is a research field of emerging interest, only a handful of papers address the critical issue of designing sustainable BSCs in which profitability and environmental impact are balanced. Apart from the environmental impact of energy conversion technologies, decisions regarding biomass logistics operations should be of first priority as these operations could be rather harmful for the environment if not planned carefully.

Moreover, our analysis has demonstrated that strategic decisions on BSCs have attracted more the interest of the research community compared with the tactical and operational decisions. However, tactical decisions and mainly aggregate production planning emerge as further challenging research field that has not been investigated thoroughly this far. There are only a few studies that investigate inventory and fleet management in BSCs, while related scientific outcomes would be of great value due to the stochasticity of supply and demand, and the unique characteristics of biomass networks (as discussed thoroughly in subsection 3.2). Finally, another critical decision that has not been addressed this far is the optimal timing of the material’s pre-treatment.

MODELING TECHNIQUES FOR BIOMASS SUPPLY CHAIN MANAGEMENT: A TAXONOMY

In this Section we review supply chain planning models focusing on strategic and tactical

decisions and specifically on the design and aggregate planning of BSCs. In table 2, we provide a taxonomy of the research works already identified in Section 4 according to the modeling technique employed, such as spreadsheet modeling, mathematical programming and heuristics. On a second level, we present an additional classification according to the unique characteristics of the supply chains under study, such as transportation mode, environmental impact, storage options examined and other; these characteristics are presented in Table 3.

Table 2. Modeling approaches and software used in reviewed literature

Mitc

hell

et

al.,

1995

Gal

lis, 1

996

Cun

diff

et a

l.,

1997

Hui

sman

et

al.,

1997

D

e M

ol e

t al.,

19

97

Alle

n et

al.,

19

98

Nils

son,

19

99a&

b

Mitc

hell

et

al.,

1999

Nag

el, 2

000

Nils

son

&

Han

sson

, 20

01

Tem

bo e

t al.,

20

03

Tats

iopo

ulos

&

Tolis

, 200

3

Frep

paz

et

al.,

2004

C

aput

o et

al.,

20

05

Ham

elin

ck e

t al

., 20

05

Sokh

ansa

nj e

t al

., 20

06

Kum

ar a

nd

Sokh

ansa

nj,

2007

Gro

nalt

and

Rau

ch, 2

007

Rav

ula

et a

l.,

2008

a&b

Ren

tizel

as

et a

l., 2

009a

R

entiz

elas

e

t al.,

200

b Fr

ombo

et a

l.,

2009

Modeling Approach Energy conversion considered x x x x x x x x x Single-biomass problem x x x x x x x x x x x x x x Multi-biomass problem x x x x x x x x Uncertain biomass supply x x x x x x x Economics studied x x x x x x x x x x Stochastic demand x x x x Deterministic demand x x x x x x x x x x Spreadsheet modeling x x x x x x x Heuristic approach x x LP x x x NLP x MILP x x x SQP x Simulation x x x x x x x x x Software / Tools LINGO x x OMP x CPLEX x MATLAB x GAMS/CPLEX x GASP IV SIMAN (Arena) x x SLAMSYSTEM x EXTEND x x SIGMA x PROSIM x GIS x x x EXCEL x x x x x x

Development of DSS Noon and Daly (1996), Voivontas et al. (2001), Frombo et al. (2009), Mitchell et al. (1995), Mitchell (2000), Ramachandra et al. (2004), Freppaz et al. (2004), Rentizelas et al. (2009), Ayoub et al. (2007)


Spreadsheet Modeling Spreadsheet modeling has been used widely for the analytical evaluation of biomass

supply chain costs. Allen et al. (1998) perform an analytic supply chain modeling for five biomass types using a spreadsheet package, concluding that 20% –50% of biomass delivered cost is due to transportation and handling activities. Mitchell et al. (1995) provide a comparative economic evaluation of various bioenergy conversion technologies and examine alternative feedstock supply strategies using a spreadsheet-based decision support system. The cost of production, collection and storage of biomass from short rotation forestry (i.e. growing of trees, usually willow or poplar, in extremely dense stands) is also examined by Mitchell et al. (1999).

Hamelinck et al. (2005) compare long-distance bioenergy supply chains and assess the influence of key parameters, such as distance, timing and scale on performance. Moreover, the economical feasibility of biomass utilization for direct production of electric energy by means of combustion and gasification-conversion processes, along with a detailed evaluation of logistic costs, is examined by Caputo et al. (2004), taking into account total capital investments, revenues from energy sale and total operating costs.

Mathematical Modeling In the bioenergy supply chain literature, several optimization methods have been applied.

Cundiff et al. (1997) develop a linear programming optimization model to minimize a cost function that is comprised of the costs of biomass logistics activities between the on-farm storage locations and the centrally located power plant, the construction and expansion costs of storage facilities, as well as the cost of violating storage capacity or lost revenue in case of biomass shortage. Tatsiopoulos and Tolis (2003) develop a detailed cotton-stalk LP based supply chain model for biomass delivery scheduling. Similarly, Frombo et al. (2009) develop an LP optimization model for the determination of the site of a single energy conversion plant and the required harvested biomass quantities, taking into account regulatory and technological constraints.

A Mixed-integer linear programming (MILP) model is proposed by de Mol et al. (1997) to estimate the annual flows of biomass for designed networks under several scenarios, encompassing several pre-treatment options. Tembo et al. (2003) develop a multi-region, multi-period, MILP model that encompasses alternative feedstocks, feedstock production, delivery, and processing. Vlachos et al. (2008) develop a MILP model for supporting strategic decision-making by identifying the optimal location of a BSC’s nodes along with the associated network flows and implement it for the design of a regional BSC located within the Region of Central Macedonia, Greece. Finally, Nagel (2000) presents a methodology for biomass to energy supply at a regional level. The problem was formulated as a MILP model using a dynamic evaluation of economic efficiency, and binary decision variables to determine whether to construct or not a district heating network, a heating plant or a co-generation plant.


109

Simulation Modeling An activity oriented stochastic computer simulation model of forest biomass logistics in

Greece, based on the SLAMSYSTEM simulation language, has been developed by Gallis (1996). De Mol et al. (1997) implemented a simulation model to obtain insights into the costs and energy consumption of the logistics operations, using the PROSIM simulation package. A dynamic simulation model named SHAM (Straw HAndling Model) for baling and transporting wheat straw by Nilsson analyses a hypothetical straw-to-energy system for district heating plants in Sweden (Nilsson, 1999a; Nilsson, 1999b). The objective of the last two studies was to evaluate and optimize various alternatives for handling straw with respect to system performance, costs and energy needs. Moreover, the dynamic simulation model SHAM is used in a following study by Nilsson and Hansson (2001) aimed at satisfying a daily average heating demand load.

Sokhansanj et al. (2006) simulate the flow of biomass from field to a biorefinery, by developing the dynamic Integrated Biomass Supply, Analysis and Logistics model (IBSAL), in order to model climatic and operational constraints, to quantify resource allocations for biomass supply and transport operations and to calculate the biomass delivered cost. Kumar and Sokhansanj (2007) use the IBSAL model to evaluate delivery systems for three biomass collection options. Ravula et al. (2008b) simulate the transportation system of a cotton gin, using a discrete event simulation model, to determine the operating parameters under various management practices, while in another work they present a comparison between two policy strategies for scheduling trucks in a biomass logistics system (Ravula et al., 2008a).

Rentizelas et al. (2009a) simulate using Matlab the operation of a biomass-to-energy system comprised of the biomass supply chain, the bioenergy conversion plant and the DHC network that will supply the final customers with the energy products needed. Rentizelas et al. (2009b) analyze three biomass storage methods through simulation modeling and are applied to a case study to come up with tangible comparative results. Finally, Huisman et al. (1997) develop a detailed simulation model for Miscanthus giganteus biomass (a large perennial grass used for energy production).

OTHER MODELING APPROACHES A number of researchers attempt to tackle the biomass supply systems’ configuration

using interactive decision support systems (DSS). Moreover, GIS (Geographical Information System) methodologies have been employed in several studies to estimate the exact transportation distances for supplying specific amounts of energy crop feedstock, taking into account the spatial variability in their yield (Graham et al., 1997; Graham et al., 2000). Noon and Daly (1996) propose a GIS-based DSS for estimating the costs for supplying wood fuel to its twelve coal-fired power plants, able to analyze efficiently the transportation networks and estimate distances and costs. A GIS–DSS to estimate the power production potential of agricultural residues is developed by Voivontas et al. (2001). This analysis handled all possible restrictions and identified candidate power plants using an iterative procedure that locates bioenergy units and establishes the needed cultivated area for biomass collection.


Frombo et al. (2009) present a GIS-based Environmental Decision Support System (EDSS) for the optimal planning of forest biomass use for energy.

Moreover, Mitchell et al. (1995) develop a bioenergy assessment model for the techno-economic assessment of bioelectricity generation, heat and liquid fuels from a range of feedstocks and several conversion technologies. Later, Mitchell (2000) discusses the problems of modeling bioenergy supply systems and develops a DSS for bioenergy applications, focusing on harvesting wood for energy from conventional forestry and short rotation forestry. Ramachandra et al. (2004) develop a DSS to assess regional biomass energy potential. Freppaz et al. (2004) present a DSS methodology for the regional exploitation of available biomass supply for energy production, through a combination of GIS and mathematical modeling. Rentizelas et al. (2009b) develop a DSS for multi-biomass energy conversion applications. The system aims at supporting an investor by assessing investment scenarios in existing multi-biomass exploitation facilities for tri-generation applications (electricity, heating and cooling) in a given area. Ayoub et al. (2007) provide a two level general Bioenergy Decision System (gBEDS) for bioenergy production planning and implementation. Finally, Gronalt and Rauch (2007) propose a simple stepwise heuristic approach to solve the forest fuel supply network design problem.

LIMITATIONS OF EXISTING MODELING EFFORTS The taxonomy of quantitative-based biomass supply chain modeling efforts, as presented

in Tables 2 and 3 reveals several gaps in the existing research in the field of BSCs. Fistly, an interesting finding is that the use of integrated planning models for biomass SCM is still quite limited. The existing models address only a minor subset of the decisions needed to be taken at a strategic, tactical and operational level. Although integrated models are inherently more complex, their potential benefits outweigh the added complexity. The existing models focus mostly on the strategic design of BSCs and the allocation of its nodes, while only a few deal with tactical and operational planning, including inventory management and control, fleet management and vehicle scheduling.

A second finding is that planning models for biomass utilization rarely capture variability at the different echelons of the supply chain. For example, many authors manage to retain linearity and flexibility of their models as they model the biomass supply chain while omitting the energy conversion processes. Others capture the stochasticity of demand, as well as the probabilistic production or case-dependant constraints through simulation models. While spreadsheet modeling has been used to display analytically the economics of supply chain operations it is not effecting in identifying optimal supply chain designs. Hybrid methods have also been used when non-linearity is introduced in the models. The tradeoff between model’s solvability and realism is always in place. Models with different levels of detail and realism may be useful at different stages of the design process.

Table 3. Supply chain issues addressed in reviewed biomass supply chain planning models

Mitc

hell

et a

l., 1

995

Gal

lis, 1

996

Cun

diff

et a

l., 1

997

Hui

sman

et a

l., 1

997

De

Mol

et a

l., 1

997

Alle

n et

al.,

199

8

Nils

son,

199

9a&

b

Mitc

hell

et a

l., 1

999

Nag

el, 2

000

Nils

son

& H

anss

on,

2001

Tem

bo e

t al.,

200

3

Tats

iopo

ulos

&To

lis,

2003

Frep

paz

et a

l., 2

004

Cap

uto

et a

l., 2

005

Ham

elin

ck e

t al.,

20

05

Sokh

ansa

nj e

t al.,

20

06

Kum

ar a

nd

Sokh

ansa

nj, 2

007

Gro

nalt

and

Rau

ch,

2007

Rav

ula

et a

l.,

2008

a&b

Ren

tizel

as e

t al.,

20

09a

Ren

tizel

as e

t al.,

20

0b

From

bo e

t al.,

200

9

Collection Purchasing costs x x x x x x x x Harvesting costs x x x x x x x x x x x x x x x Production costs x x

StorageOn - farm storage x x x x x x x x x x x x x x Intermediate storage x x x x x x x x x In plant storage x x x x x x x x

Transportation Contracting with a 3pl x x x x x x x x Undertaken by farmers x x Road Transportation x x x x x x x x x x x x x x x x x x x Road, Rail or Water x x

Other parametersProcessing considered x x x x x x x x x x x x Environmental impact x x x x x x x x x Long-distance networks x Short-distance networks x x x x x x x x x x x x x x x x x x x

Biomass types studied

Fore

stry

and

sh

ort r

otat

ion

copp

ice

Fore

st b

iom

ass

Switc

hgra

ss

Mis

cant

hus G

igan

teou

s

Prun

ings

, was

te-w

ood,

se

wag

e sl

udge

, was

te p

aper

Fore

st fu

el, S

hort

Rot

atio

n C

oppi

ce, S

traw

, Mis

cant

hus

Stra

w

Shor

t rot

atio

n fo

rest

ry

Bio

mas

s

Cer

eals

traw

and

reed

can

ary

gras

s

Lign

ocel

lulo

sic

biom

ass

feed

stoc

k

Cot

ton

stal

ks

Fore

st &

was

te b

iom

ass

agro

-indu

stria

l and

woo

d w

aste

s

Fore

stry

resi

dues

and

en

ergy

cro

ps

Cor

n st

over

supp

ly

Switc

hgra

ss

Woo

d bi

omas

s & fo

rest

fu

els

Cot

ton

gin

Whe

at S

traw

, cor

n st

alks

, ol

ive

& a

lmon

d tre

e pr

unin

gs

Cot

ton

stal

ks, A

lmon

d tre

e pr

ooni

ngs

Fore

st, a

gric

ultu

ral,

indu

stry

. res

idue

s


Another byproduct of the taxonomy is that most modeling approaches of BSCs optimize a single objective such as cost or profit. However, the design, planning, scheduling of supply networks often involves trade-offs among different goals. An additional optimization goal in BSC modeling could be the minimization of CO2 emissions of its logistics operations. Finally, multi-objective optimization has been considered by different researchers. For example, Sabri and Beamon (2000) develop an integrated multi-objective supply chain model for strategic and operational supply chain planning under uncertainties of product, supply and demand.

CONCLUSION The merit of the gradual replacement of fossil fuel by renewable energy sources has been

clearly documented. Logistics and supply chain management are disciplines of critical importance for the successful energetic utilization of waste biomass and organic substrates. Interested stakeholders for designing and implementing such BSCs need to address systemically an array of decisions spanning all levels of the natural hierarchical decision-making process. To that effect, based on industrial practice and needs and existing research, we propose a novel comprehensive hierarchical decision-making framework. We identify gaps in the existing research and thus opportunities for additional research by matching the proposed framework with the existing state-of-the-art research. We then proceeded by additionally taxonomizing these modeling efforts based on the modeling techniques employed to unveil limitations of the existing efforts. We envision the developed framework to provide systemic guidance for researchers and practitioners alike, in their effort towards designing and executing efficient BSCs.

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Chapter 4

WASTE PICKING AT LANDFILLS: A SOURCE OF LIVELIHOOD OR INTERFERENCE WITH WASTE

DISPOSAL PROCESSES?

Benjamin Bolaane*

ABSTRACT

There appears to be a consensus that stakeholder participation is one of the key dimensions to realising sustainable waste management. Among the identified stakeholders are waste pickers. This chapter established the extent and manifestations of waste picking at the Gaborone landfill. The chapter used a cross-section of methods that included informal interviews, in-depth interviews and key informant interviews. It was found that there was extensive waste picking at the Gaborone landfill mainly constituted of informal waste pickers who irked a living directly from picking and formal waste pickers who were employed by the formal recycling sector to pick materials of their interest. However, the attitude of local authority officials who manage the landfill was to exclude the informal waste pickers through a permit system. Informal waste pickers were deemed to be uncontrollable and interfering with daily landfill activities. It was also found that waste pickers were engaged in collaborative efforts to support each other and enhance their earning potential. This provides an opportunity to build into the existing networks for integration of waste pickers into formal waste management activities. On the basis of the foregoing, this chapter proposes that to realise sustainability of waste management systems there should be recognition by waste management policy that waste pickers are a critical stakeholder who need recognition in waste management processes. The emphasis on government policy should be on educating all stakeholders on the symbiotic nature of their relationships.

* Department of Architecture and Planning, P.O. Box 601093, Gaborone, BOTSWANA, [email protected]

Benjamin Bolaane 122

1. INTRODUCTION Stakeholder participation is one of the key components of the integrated sustainable solid

waste management concept (van de Klundert and Aschütz 2001). Among the identified key stakeholders are waste pickers (Sudhir et al. 1997, Rouse 2006, Wilson et al. 2006). There appears to be a consensus that the primary objective of waste picking is earning a livelihood (Ahmed and Ali 2004, Hayami 2006, Olu-Olu and Omotosho 2007). In addition to the economic benefits of waste picking, there is continuing realization that the pickers also benefit local authorities by reducing the quantity of waste to be collected and disposed of (Baud et al. 2001, Hayami 2006). These positives attributes to waste picking have motivated most practitioners and researchers in the field to focus their efforts on identifying ways and means of integrating waste pickers in the waste formal management processes (Ali et al. 1999, Wilson 2006). But opponents of waste picking are mainly concerned with occupational health and working conditions of waste pickers (UNEP 2000, Torun et al. 2006). Others, primarily local authorities, argue that they interfere with operational activities of disposal sites (Baud et al. 2001, Rouse 2006). This concern has led to the landfill managers and other officials to work on mechanisms that are intended to exclude waste pickers from accessing landfills (Mitchell 2008). The rational for such conduct by the officials is informed by public policy that is often driven by the need to safeguard public health. This has often led to police harassment and eviction of waste pickers (Rouse 2006; Wilson 2006), who have often responded by blocking access of collection trucks, resisting extinguishing of landfill fires by water (Rouse 2006).While picking occurs at collection points, transfer stations and disposal sites (Sudhir et al. 1997, Wilson et al. 2006), it appears the primary concerns by the opponents of waste picking are mainly with regard to picking at disposal sites (Rouse 2006; Wilson 2006).

Waste picking is largely a phenomenon of developing countries, with relatively high levels of unemployment and poverty (UNEP 2000, Hayami 2006). Generally, the rise in wage rate and better employment opportunities in a country makes waste picking eventually unviable (Beede and Bloom 1995, Amin 2005). The majority of the countries where waste picking has been documented such as Vietnam, Pakistan, India, Phillipines and Indonesia are classified in the income categories of low to low-middle income (World Bank 2007). In Botswana, an upper middle income country, with income per capita of USA$ 6120 in 2007 (World Bank 2007), waste picking as a vocation is not common and it is mainly restricted to landfills. However, limited work has been done to establish the extent and manifestations of waste picking at the Gaborone landfill. Rankokwane and Gwebu (2006) on one of the few studies carried out at the Gaborone landfill concluded that even though waste picking at the Gaborone landfill may be hazardous to the informal entrepreneurs, it has the potential to sustain livelihoods. The objective of this chapter is to fill the existing knowledge gap by determining the character of waste picking at the Gaborone landfill and its contribution to livelihood diversification. More specifically, the study established the extent and magnitude of waste picking at the Gaborone; profiled waste pickers at the landfill and established their motives for engaging in waste picking and determined the contribution of waste picking to livelihood diversification of the pickers. The chapter recommends policy interventions that recognize the role of waste pickers as a stakeholder in waste management.

Waste Picking at Landfills

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2. CONCEPTUAL BENCHMARKS FOR SUSTAINABLE WASTE MANAGEMENT

Subsequent to the environmental concerns of waste generation, Integrated Waste

Management (IWM) emerged as a leading concept in sustainable solid waste management (Tchobanoglous 1993; Palmisano and Barlaz 1996; van Beukering et al. 1999). The broader concept implies that decisions on waste handling should take into account environmental, social and institutional dimensions. The integrative aspect of IWM lies in the tradeoff between these dimensions. Among the key elements of the integrated waste management approach is the waste hierarchy (Barret and Lawlor 1997 and Shah 2000). The waste hierarchy is an ordered list of approaches to deal with municipal solid waste (MSW), which ranks the options according to their environmental acceptability, with waste reduction the most preferred, and landfill disposal the least preferred. However, there is a school of thought that despite being generally accepted, the rigid use of the hierarchy will not always lead to environmentally and economically sustainable systems, and it makes no attempt to measure the impacts of the different options (White et al. 1995). The result of this school of thought is a proposal for a holistic approach that recognizes that all disposal options have a role to play in waste management. Van Beukering et al. (1999) are of the view that the waste hierarchy was never intended to be a dogma as its critics often argue, but was mainly intended to provide options for policy makers, and only referring to environmental effects not economic or social criteria. Overall, IWM seems to place emphasis of the different waste management system elements, and appears to be oblivious to the fact that waste management does not take place in a vacuum.

On realization that waste management, is much more that putting the traditional waste management systems in a certain order, the concept of Integrated Sustainable Waste Management (ISWM) was developed by WASTE, Advisors on Urban Environment and Development in 1995. It has three dimensions of Stakeholders, Waste System Elements and Aspects. It differs from the conventional waste management system by seeking stakeholder participation, covering waste prevention and resource recovery, including interactions with other systems and promoting an integration of different habitat scales (city, neighbourhood and household). While the ISWM concept is broad, with its dimensions over encompassing, researchers and practitioners seem to put emphasis of sustainability on resource recovery through initiating expensive source separation schemes in the richer countries and in supporting recycling initiatives by certain sectors of society in developing economies (Shekdar 2009). The emphasis for sustainability of waste management systems is placed on the stakeholder dimension of ISWM, with the view that each stakeholder has a role to play (Joseph 2006; Ahmed and Ali 2006; Rose 2006; Wilson et al. 2006). The informal sector or waste pickers, who depend on recycling materials from waste for their livelihood, have been identified as a key stakeholder (Wilson et al. 2006; Joseph 2006; Ahmed and Ali 2004). There is growing recognition of the economic, social and environmental benefits of waste pickers in waste management. This has led to considerable activity in many developing countries in developing policies, often led by NGOs that seek to integrate them into formal waste management activities (Joseph 2006; Wilson et al. 2006).

What seems to emerge from the preceding discussion is that sustainable waste management systems should be premised on multiple stakeholder approach, with each


stakeholder having a role to play. For this to be achieved there is need to build some consensus that apart from the limitations brought about by waste pickers in the waste management process, they are an important stakeholder. It is this consensus with other stakeholder in the sector that could realize formal recognition and integration of waste pickers as partners in waste management. That is not to say ISWM is a panacea to waste management issues, but rather, it provides a framework for the selection of appropriate technologies and institutional setup for development of sustainable waste management systems.

3. METHODOLOGY The study used a cross-spectrum of data collection techniques that included informal

interviews, in-depth interviews and key informant interviews and observations. Informal interviews preceded in-depth interviews and were mainly exploratory intended to establish rapport and identifying waste pickers that were cooperative and willing to share their experiences in relation to their waste picking endeavours. This was important in that waste pickers tend to have a spasmodic ‘work schedule’ and generally shy away from unfamiliar strangers prying into their business (Rankokwane and Gwebu 2006). The interviews were conducted in January 2006. At the time of the study, there were approximately between 200 and 300 waste pickers at the Gaborone landfill. Of these waste pickers, 61 were working for 6 middlemen, picking materials that included paper/cardboard, metal, tyres, glass bottles, plastic bottles and metal cans. In addition to waste pickers employed by middlemen, there were others who picked waste on an informal basis. Informal interviews were conducted with the 20 waste pickers, 10 from each category of pickers (formally employed or self employed). The interviewees were selected randomly subject to their agreement to engaging in the interview. A total of 6 in-depth interviews were carried out with waste pickers selected on the basis of whether they were employed by formal recycling company or self employed (2 formally employed and 4 informal pickers).

Key informant interviews were carried with the landfill management crew at the Gaborone landfill that included landfill manager, landfill security officer and landfill plant operator to establish the operational constraints associated with waste picking. Another key informant interviewed was a representative of Somarelang Tikologo (an environmental NGO) Formal sector entrepreneurs were also interviewed to establish the use to which they put the materials obtained from waste pickers. Observations mainly focused on the interactions of waste pickers and the operational activities of the landfill.

The raw data from interviews were processed using Microsoft Excel to provide tables and descriptive statistics for analysis. Observations and responses to in-depth interviews were organised into themes.

4. GABORONE LANDFILL AND WASTE PICKING ACTIVITIES The Gaborone landfill was opened in 1993. It is located about 5km from the city centre

(see Figure 1). Situated in a area measuring 630m by 340 m, it was designed to receive waste for 10 years. It was closed from receiving waste on 30th September 2009, following the


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opening of a new landfill that serves Gaborone and the surrounding areas. The main activities at the Gaborone landfill as observed during fieldwork involved daily delivery of waste from the different waste generators of households, commercial enterprises and light industries. Waste was delivered by local authorities’ trucks, private companies contracted by the local authority and individuals. As the collection vehicles entered the landfill, they were directed to the appropriate zone for unloading, depending on the materials to be disposed of. There were designated zones for refuse, garden waste, scrap metals and tyres. At construction, the landfill was security fenced to bar intruders including waste pickers. At the time of the study, the perimeter fence for the landfill was dilapidated and almost accessible at any point. It was not clear when informal waste picking started at the Gaborone landfill. But there were suggestions in the public media that it intensified with the dilapidation of the security fence. The intensity of waste picking was viewed by local authority officials to be interfering with daily landfill operations as waste pickers climbed into disposal vehicles as they arrived at the landfill (see Figure 2), getting on the way of the bulldozer and compactor as they spread and compacted refuse respectively and spreading refuse around the disposal area (Daily news 2005; Ontebetse 2007). Daily News (2003) reported on complaints by residents of neighbourhoods close to the landfill about smoke emanating from the landfill mainly attributed to burning of waste by waste pickers. There was also some public health concerns reported in the public media emanating from allegations that waste pickers were picking foodstuff such as chickens, expired canned food and drinks that they sold to food vendors (Ontebetse 2007, Daily News 2001)

Figure ii. Waste collection vehicle entering the landfill with waste pickers climbing it

On the basis of these concerns, Gaborone City decided to implement measures that were intended to restrict entry of waste pickers into the landfill. Among the measures implemented


were security patrol around the perimeter fence of the landfill and licensing of waste pickers. However, the landfill perimeter patrol initiative that involved four security personnel during the day and two during the night failed because they were overwhelmed by the numbers of waste pickers wanting to enter the landfill (Daily News 2005). The initial permits were given to formal recyclers who had lobbied the city council for access to the landfill to pick recyclables at the exclusion of informal waste pickers. The formal recyclers would in turn hire waste pickers who they had to register with the local authority to pick materials of their interest. At inception, four companies recycling paper, glass, plastic and metal cans were licensed. Figure 3 shows metal cans picked by this arrangement ready for collection by a company that provides intermediate markets for recyclables (see Bolaane and Ali 2005).

Figure iii. Picked metal cans ready for collection

The above discussions show that there was desire to access recyclables from the landfill by formal and informal sectors. This could be indicative of that recyclables are not readily accessible before they reach the landfill, primarily because there no established source separation. However materials obtained at the landfill could be of lower quality as a result of cross contamination. In addition to limited access to recyclables before they reach the landfill, there appears to be some power struggle to access recyclables between the formal and informal sector. The formal sector lobbied the local authority for access to recyclables at the exclusion of the informal sector. The local authority acceded to the formal sector request though the introduction of a permit system. This could indicate some prejudice on informal waste pickers by the local authority. This could possibly be a scenario where profit is given preference to livelihood.


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Box 1. Typical waste picking permit

CONDITIONAL PERMIT TO SALVAGE MATERIAL YOU APPLIED FOR TO COLLECT FROM GABORONE CITY COUNCIL – LANDFILL SITE

Your application can only be accepted if you can agree and promise to comply with the following conditions: 1. Provided you enter the landfill at 0.800 am and report to the main gate at 15.30 hrs to

knock-off on daily basis from Monday to Friday only weekends and public holidays excluded.

2. Collect only what you had applied for, and bring water for yourself for drinking purposes.

3. No babies and school going children less than 18 years will be allowed into the landfill site for safety and health reasons.

4. Permit cannot be passed on to the next person. 5. No one will be allowed to pick-up or scavenge foodstuff from the landfill site for

eating or selling purposes. 6. Be regular worker, but locals can absent themselves for three weeks, foreigners five

weeks consecutively for good reason, if you have a good reasons for exceeding the specified weeks, you should inform management.

7. Salvaged materials should not be left unattended for a long period of time such that they discourage smooth landfill operations

8. Termination of permit can be done any time by GCC in writing to the applicant SIGNED AGREEMENT I, …………………………….. the applicant hereby agree and promise GCC to comply with all conditions stated above and thereby append my own signature ……………………………….. ID……………………………. Passport No…………………………… PERMIT Permission is given to the applicant …………………………………to salvage ------------------------------------from GCC landfill starting from this day----------------------

Box 1 shows typical details provided in waste picking agreement entered into by the

waste pickers and Gaborone City Council. A closer reading of the conditions of the agreement shows that while it was initially given to formal recycling companies; it was also meant for individual waste pickers. The agreement also restricted times at which to pick recyclables and excluded food stuff from materials that could be picked, probably as a result of public health concerns. Overall, the permit system seems to be encouraging recycling through allowing waste picking waste picking by employees of the formal sector. However, if viewed against the concerns of the officials, it appears they do not encourage waste picking at the landfill because of concerns such as interference with landfill operations and public health threats of food obtained from the landfill. Despite these concerns, the desire to earn a living from waste picking by the informal sector made it inevitable; the only option left was an attempt at its regulation with the object of making it orderly. But sanctions for violation of the permit conditions were not clearly spelt out. Apart from that, the permit conditions are silent


on protective clothing which is necessary when working in an environment such as the landfill. This could expose waste pickers to occupational risks of waste picking.

The initial permits were not given to individuals. However, landfill security officials with the assistance of the police would often round up and chase away waste pickers who were not working for companies with permits. This was viewed as harassment and discrimination by waste pickers and they continued to force their way into the landfill until the security officials were overwhelmed. This forced the local authority to extend licensing of pickers to individuals. However, because of the large number of individual applicants, the licensing system collapsed and waste picking was free for all those interested. At the time, the landfill was also operating like a dump site, with limited or no daily cover and compaction (see Figure 4). In addition to the control measures that were implemented without success, the local authority also contemplated erecting a new electrified fence around the landfill as well as destroying food stuff before disposal at the landfill (Daily News 2005; Ontebetse 2007). These measures were however never implemented.

It is also clear from the licensing system and the contemplated security measures that they were deliberate efforts to exclude informal waste pickers from the Gaborone landfill. This may be a result of preconceived ideas that they were a nuisance to landfill operations. This attitude could stifle integration of waste pickers into formal waste management activities and deny them a means of livelihood.

Figure iv: Gaborone landfill operating like a dump site

4.1. Socio-Demographic Characteristics of Waste Pickers

Informal interviews revealed that most of the waste pickers were from the high density

and low income neighbourhoods of Old Naledi and Bontleng (see Figure 1). Others had


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erected makeshift housing structures that served as their permanent dwelling as they irked their living solely from waste picking. The housing structures have primarily been constructed from materials salvaged at the landfill, such as wood, cardboards, plastics and metal sheets. At the time of the study, because of the economic hardships in Zimbabwe, there was a reported increase in the number of Zimbabweans waste pickers, which often resulted in conflicts that are xenophobia in nature between the different nationalities. Table 1 shows the distribution of waste pickers by the materials picked from 61 waste pickers hired by formal recyclers issued with permits. A large proportion of pickers were employed to pick tyres (23%) followed by metals cans (20%) and Scrap metal (18%). These materials were mainly picked because of their established intermediate markets that had linkages with end-user markets outside the country (Bolaane and Ali 2005). Prevalence of waste pickers employed formally is a unique scenario in the waste picking vocation. This could indicate that there is limited opportunity to retrieve recyclables by the formal recyclers other than at the landfill.

Table 1. Distribution of formally employed waste pickers by material components

Recyclable materials No. of pickers employed % of pickers employed Paper 8 13 Scrap metal 11 18 Tyres 14 23 Glass bottles 6 10 Metal cans 12 20 Plastic bottles 10 16 Total 61 100

The age of those interviews ranged from 15 to 60. Of these, 35 percent were between the

ages of 15 to 24. They were mainly primary school dropouts who decided to engage on waste picking to generate personal income or just daily sustenance by consuming food materials at the landfill. The rest, 25 to 60 year olds started picking at an earlier age and grew up engaging in the vocation. Others came to town looking for employment without success or lost their jobs or family support network. Most of those interviewed reported that their first engagement with waste picking was an experiment that development into a livelihood strategy.

Of the 20 waste pickers that were interviewed, 11 were males while 9 were females. Overall, there appears to be more males than females at the landfill. This could be possible be explained by the risk associated with working at the landfill environment, with the physical men being able defend themselves more vigorously when their security is under threat.

4.2. Case Histories of Waste Pickers From in-Depth Interviews Box 2 through Box 7 presents brief case histories of waste pickers obtained through in-

depth interviews. Of the six waste pickers interviewed, two worked for formal recyclers and picked plastic bottles and paper, while four were self employed and picked metal cans, scrap metal, glass bottles and tyres. The case histories show that people are driven into waste picking primarily to earn a living. The materials they pick often have established markets that enable them to earn regular and stable income. It is also clear from the case histories that the


waste pickers realise the occupational hazards of working at the landfill, with some of them having adequate protective clothing. While the primary objective in waste picking is to pick recyclables that have established markets to earn some income, some waste pickers take advantage of their stay at the landfill to pick food stuff to supplement their ration. It also emerges from the case histories that informal waste pickers collaborate with each other at their own initiative to offer each other support and collectively increase their earnings. This is an important development to build onto because most waste management practitioners who have been working towards improving the working conditions of waste pickers, have always tried to form cooperatives that will enable them to speak with one voice. The case histories of waste pickers also show that they usually work beyond the stipulated hours in the permits. Apart from showing that the local authorities are not able to enforce their permit conditions, it also shows the desire of waste pickers to stay longer and the landfill to maximise their earning potential.

Box 2. Self-employed metal can picker

Waste Picker 1 Waste picker 1 is a 45 year old lady. She started waste picking in 1997 after the death of her husband in order to support her two children who at the time of the study were aged 22 and 25. She started by collecting paper, but later changed to metal cans because they were much easier to sort. Her typical day starts at 9 am and end at 5pm. She has some protective clothing that consists of knee high boots, hat, musk, work suit and thick hand gloves. She could easily be mistaken for a landfill management crew. Together with 12 others pickers who obtained permits for waste picking, they have grouped themselves to form one team (almost like a cooperative). Within this team, there were nine women and 3 men. The basis for their collaboration was to minimize transportation costs of recyclables as they transport them to intermediate markets. Every two weeks they each pay P10 for transport. At the end of the month they each get between P400 and P550. She does not particularly like the job, but does not have much option. She also dislikes the fact that they are usually harassed by street children who often roam around the landfill looking for food.

Box 3. Self-employed tyre picker.

Waste Picker 2 Waste picker 2 is a 23 year old Zimbabwean man, who started picking tyres in 2003, a month after he arrived in Botswana. He was mainly driven into picking by economic hardships in his native country. He usually starts work at 8 am and finishes at 5pm from Monday to Saturday. He works with other 13 tyre pickers, all Zimbabweans. Each one of the tyre pickers pays P350 to transport the tyres to the end user market in Zimbabwe. He makes between P700 and P750/month. His primary concern is that he is not able to get a work permit to enable him to stay longer in Botswana. He often has to go back to Zimbabwe to extend his length of stay in Botswana.


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Box 4. Self-employed glass bottle picker

Waste Picker 3 Waste picker 3 is a 56 year divorced woman who started picking glass bottles in 1997. She has two children aged 20 and 25 who are both going to the University of Botswana. She is very much looking forward to their graduation so that she could retire from waste picking. She works a five day week from 8 am to 5 pm. She sells the glass bottles she picks to a local company that operates a deposit refund scheme. She has a full complement of protective clothing consisting of knee level boots, must, work suit and gloves. She collaborates with another lady with whom they share the profits at the end of every month. Every two weeks they sell the bottles and deposit the money in a bank account. At the end of the month they withdraw the money and share it equally. On average, they each make P600/month.

Box 5. Self-employed scrap metal picker

Waste Picker 4 Waste picker 4 is a 50 year old man who is licensed to pick ferrous and non ferrous scrap metal. A market for scrap metal is readily available and is therefore popular with pickers without permits. There is lots of competition in picking scrap metal. To offset the competition brought about pickers without permits, Waste picker 4 has hired 10 other scrap metal pickers working under his permit. In addition to picking scrap metal, Waste picker 4 also transports scrap metal for others to the market. This earns him additional income. He has some protective clothing for himself, but not his workers. He reported that on average he makes more than P1000 in profit.

Box 6. Formally employed plastic bottles pickers

Waste Picker 5 Waste picker 5 is a 60 year old man who picks plastic bottles. He started picking independently in 1995. He was later hired by a company that recycles plastic bottles. He started working for the company in 1999, mainly motivated by a semblance of job security. Every morning himself and his co-workers are dropped off by the company vehicle at the landfill to start work from 9 am to 5 pm. The company provides them with protective clothing. They are paid according to the quantity of materials they pick. Even though he has been picking for a long time, he thinks waste picking lowers one’s dignity and exposes them to health hazards. He is however grateful that working at the landfill affords one the opportunities to pick other valuables including food.


Box 7. Formally employed paper picker

Waste Picker 6 Waste picker 6 is a 24 year older mother of one. She started picking in 2005. She dropped out of school while doing O-levels. She has been hired by a paper recycling company together with seven other waste pickers. When she went for a job interview at the company she was not aware that she will be working at the landfill. She almost quit the job when she saw the environment at the landfill, but persevered in order to support his son. Now she is used to the job, even though her age mates often make a mockery about her job. She starts work at the landfill at 8 am and end at 5 pm. She is paid according to the quantity of paper she picks. On average she makes between P400 and P500/month, which is enough for her daily needs. A large proportion of her food supply is obtained from the landfill.

5. MATERIALS, MARKETS AND INCOME Materials that were mainly picked by waste pickers included paper, scrap metal, tyres,

glass bottles, plastic bottles metal cans. These materials were mainly picked because they had established intermediate markets. Glass bottles were mainly returned to the local bottling company that operated a deposit refund scheme. Figure 5 shows a schematic diagram of materials flow from source to end user markets. The materials are recovered from the landfill by waste pickers hired by formal recyclers (intermediate markets) or informal waste pickers who would sell to intermediate markets. In all the two scenarios, the waste pickers are paid according the quantity of materials picked.

Landfill

Waste pickers (formal) Waste pickers (informal)

Intermediate Markets

Sorting, Cleaning, Bailing

Regional Markets

Source

Recovery

Markets

Processing

End use

Figure v: Materials flow from source to market


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The income obtained from waste picking depended on the type of material picked and on whether the waste picker is hired by a formal recycler or working informally. Waste pickers who worked informally collecting tyres, glass bottles and scrap metal made more money than other, usually in the range of P600- P1000/month, while those working for formal recycler picking paper, plastic bottles and metal cans made between P400 and P550. This could be explained by that glass bottles, tyres and scrap metal pickers sell directly to intermediate markets, and will often sell to the buyer who offers the highest price. While those hired by formal recyclers, the market and the price are pre-determined by the buyer. However, the earnings of waste pickers are significant, in some instances even higher than the wages in the formal sector.

6. STAKEHOLDER PERCEPTIONS The perception of other stakeholders such local authority officials, formal recyclers and

NGO officials are varied. Perceptions of landfill management crew were largely influenced by permit system put in place by the local authority. For example all interviewed landfill management crew indicated that they do not have any problems with the waste pickers with permits because they are cooperative and work with them in camaraderie relationship. The landfill management were of the view that informal waste pickers were the once who caused them a lot of problems and interfered with landfill operational activities. Their main concern was that these pickers would often climb into waste delivery vehicles and delay the unloading process. At times they would even block the passage of the vehicle from disposing of waste at the designated space. In addition, these pickers would often delay the processes of spreading and compacting of waste because the equipment had to wait until they have finished picking all the valuables. Despite the concerns of waste pickers interfering with waste management processes, landfill workers support regulated waste pickers, primary because they realise that it is a source of livelihood for those involved in the vocation. In fact some workers at the landfill are also engaged in buying materials from waste pickers to sell to intermediate markets, albeit at a limited scale.

Formal recyclers that provided intermediate markets for materials picked by waste pickers were of the view that the landfill provided a single source of a large volume of materials. This motivated them to hire waste pickers to pick materials from the landfill under the local authorities’ licensing system. These formal recyclers see their role as enhancing the livelihood of waste pickers by providing a market for picked recyclables. Somarelang Tikologo and Kgalagadi Conservation Society, local environmental NGOs have a contrasting view to that of formal recyclers. While they all agree that waste picking contributes to the economic wellbeing of waste pickers, they are of the view that the pickers are exploited by middlemen through paying below market prices for the materials. Their view is that to further enhance earning livelihood from picking, waste picking should be integrated into formal waste management process. As a precursor to integration, the NGOs are of the view that there should be concerted efforts towards improving the working conditions of waste pickers. Among the suggested improvements is creating awareness by educating pickers on safety and occupational health risks. In addition, to enhance the income earned by pickers, NGOs suggest that instead of selling their materials to middlemen, waste pickers should group


themselves and sell the materials direct to end users. Despite the suggested ideas of improving working conditions of waste pickers, these NGOs have not yet initiated practical projects that could improve the working conditions of waste pickers as is the case in other jurisdiction (Brazil Recycling Commitment 1996; UNEP 2000).

7. CONCLUSION While waste picking has largely been a phenomenon of low income countries with high

unemployment rates as a source of income for those who participate in it, it has also been found to contribute to livelihood diversification of waste pickers in upper middle income countries like Botswana. But because relatively effective waste collection systems, that take the majority of recyclables to disposal sites, waste picking has mainly been taking place at the landfill. Waste picking at landfills, particularly informal picking appears not to be wholly embraced by official authorities. Their concerns over interference with landfill operation processes also appear valid. But the validity of their concerns should not compromise the desire of waste pickers to earn a leaving from waste. Rather, these concerns could be addressed by a collaborative effort with waste pickers by recognising them as stakeholders as opposed to being confrontational.

Instead of embracing waste pickers as a stakeholder in waste management processes, there has been a tendency by formal recyclers and official authorities to exclude informal waste pickers from accessing the materials at the landfill. These exclusionist tendencies by measures such as permits, policing and plans to erect electric fences could undermine the livelihood of informal waste pickers. Apart from that the attitude of official authorities towards informal waste pickers could make it difficult to integrate them into formal waste management processes. However the collaborative efforts of waste pickers where they voluntarily form working teams, provides an opportunity to use the established links to forge any form of cooperation with the official authorities.

It has been established that formal sector employment of waste pickers tends to reduce their earnings. This could mean that any assistance towards improving the working conditions of waste pickers as contemplated by other stakeholders such NGOs should entail establishing an enabling environment for direct access to the markets.

To realize sustainability of waste management systems, waste management policy should recognise the important role played by waste pickers in the waste management process. Government policy should emphasize educating all stakeholders on the symbiotic nature of their relationship. This would entail facilitating access to recyclables without interfering with landfill operation activities. This may include provision of infrastructure such as sorting platforms at the landfill, as is the case in other jurisdictions. But to minimize competition between the formal and informal waste recycling sectors, the formal sector should explore the possibility of cooperating with local authority to set up source separation schemes, that will in turn provide cleaner and high quality recyclables.


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Gaborone landfill to close sooner due to high amount of Refuse. (2003, January 20). Daily News Online edition. http://www.dailynews.gov.bw

Hayami, Y., Dikshit, A.K. and Mishra, S.N. (2006) Waste Pickers and collectors in Delhi: Poverty and environment in an urban informal sector. Journal of Development Studies Volume 42(1): 41-69

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Palmisano, A.C. and Barlaz, M.A. (1996). Introduction to Solid Waste Decomposition. Microbiology of solid waste, CRC Press, Boca Baton.

Rouse, J.R. (2006) Seeking common ground for people: Livelihoods, governance and waste. Habitat International 30(2006): 741-753

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Shah, K.L. (2000) Basics of solid and Hazardous Waste Management Technology, Prenctice Hall, Upper Saddle River.

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World Bank 2007. 2007 Data and Statistics (http://web)


Chapter 5

SIMULTANEOUS SOLUTION FOR SOLID WASTE MANAGEMENT AND WASTE WATER TREATMENT:

CR(VI) REMOVAL AS A CASE STUDY

Suresh Gupta and B V Babu*

ABSTRACT

Solid waste management is a major environmental issue all over the world. Uncontrolled solid waste disposal increases the risk of different diseases and health problems. Different ways of dealing with the solid waste issues are demonstrated in this chapter. Recycling of material for different purposes or for reprocessing into a different form is the most significant way of handling the solid waste. In this study, plant waste (tamarind seeds, neem leaves, sawdust) and the waste generated from coal burning (flyash) is used for recycling. Solid waste material used in this study is reprocessed into the form of adsorbents for the removal of hexavalent chromium [Cr(VI)] from the wastewater streams. The presence of highly toxic, mutagenic, and carcinogenic Cr(VI) in effluent streams is a major environmental issue. Adsorption process which is a cost effective and versatile method for the removal of Cr(VI) is chosen in this case study. The study includes the development of low-cost adsorbents such as activated tamarind seeds, activated neem leaves, sawdust, and activated flyash. The performance of above adsorbents are compared with the commercially available activated carbon which is a well known adsorbent used for the removal of Cr(VI) from wastewater. Batch and continuous adsorption experiments are conducted to evaluate the performance of developed adsorbents for the removal of Cr(VI) from wastewater. The maximum adsorption capacity is obtained as 62.9 mg/g for activated neem leaves among various developed adsorbents, while maximum adsorption capacity for commercially available activated carbon is found to be 71.7 mg/g at an initial pH value of 1. Desorption of Cr(VI) from adsorbents using acid and base treatment exhibit higher desorption efficiency by more than 95% except for activated flyash. A feasible solution is proposed, for the disposal of contaminant (acid and base solutions) containing high concentration of

* Dean-Educational Hardware Division & Professor, Chemical Engineering Group, Birla Institute of Technology

and Science (BITS), Pilani - 333 031, Rajasthan, INDIA. Phone: +91-1596-515259; Fax: +91-1596-244183; Email: [email protected] Homepage: http://discovery.bits-pilani.ac.in/~bvbabu/

Suresh Gupta and B. V. Babu 138

Cr(VI) obtained during desorption process. Continuous column studies are carried out for the removal of Cr(VI) from wastewater using activated tamarind seeds and sawdust as adsorbents in a fixed-bed adsorption column. The effects of influencing parameters such as flow rate, mass of adsorbent, initial Cr(VI) concentration are studied and breakthrough curves are obtained. The extensive cost analysis which is carried out for developed and commercial adsorbent show that the sawdust is most economically viable option for the Cr(VI) removal from wastewater. Through this work of Cr(VI) removal as a case study, it is demonstrated that the waste management and waste water treatment problems can be solved simultaneously.

Keywords: Solid waste, Recycling, Re-use, Adsorption, Hexavalent chromium, Batch studies, Continuous studies, Desorption, Cost analysis.

1. INTRODUCTION Solid waste has become serious concern for many environmental groups for decades.

There has been a significant increase in solid waste generation in all over the world. This is due to the increase in population growth and economic development. The first source of solid waste is the production of commodities and byproducts from solid materials. The things which are produced are discarded to the environment. Natural cycle of plant growth and decay is considered as second source of solid waste. The plant material which is not in use is discarded. This solid waste is the most variable source of municipal solid waste and is also source of bulky waste production. Yard waste which includes leaves, grass clippings & shrub and garden trimmings commonly account for as little as 5% to 20% of the municipal solid waste generated in any county. Generally, plant material wastes are available in abundant, when lots are cleared for new construction. Due to the increase in civilization, the waste generated became a problem of more complex nature.

The risk involved due to the unscientific disposal of solid waste include the population in areas where no proper disposal method is adapted, waste workers, and workers in facilities producing toxic and infectious material. A high-risk exists for the population living close to a waste dump and the water supply near these areas become contaminated either due to waste dumping or leakage from landfill sites. Uncollected solid waste also increases risk of injury, and infection. Various health related problems occur due to the solid wastes such as skin and blood infections resulting from direct contact with waste, eye and respiratory infections resulting from exposure to infected dust, different diseases resulting from the bites of animals feeding on the waste, cancers resulting from exposure to dust and hazardous compounds (UNEP, 1996).

The above mentioned harmful effects of solid wastes indicate that solid waste management has become a major environmental issue globally. The solid wastes can also be treated with different established waste treatment technologies such as composting, landfill, recycling, and windrow composting. The main disadvantages of these methods are to produce the secondary pollutants and economically not feasible. The environmentally beneficial ways of dealing with solid wastes or residues are to reduce, re-use, and recycle wastes. Reduction in waste quantity is possible by modification in the product design, change in the material specification, and improvement in production processes. Re-use of solid wastes means the thing continues to perform the function for which it was originally designed. The most

Simultaneous Solution for Solid Waste Management…

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significant way of dealing the solid waste issue is the recycling of the material for a different purpose or for reprocessing into a different form.

The plant and industrial waste materials such as tamarind seeds, neem leaves, saw dust, and flyash are available in abundance and have a major difficulty in disposal. Tamarind seeds are widely available in Asian and African continents as well as in many parts of tropical American region as they can be easily cultivated in variety of soils. Because of its widespread cultivation, it is used in cuisines all around the world. Freshly fallen as well as partially dried neem leaves are available in huge quantities in nature. This increases the quantity of municipal solid waste tremendously. Sawdust is composed of fine particles of wood material. Sawdust is produced from cutting the wood with a saw and it is the main by-product of sawmills. Flyash is one of the waste products generated in the combustion of coal. Fly ash is generally captured from the chimneys of coal-fired power plants. Disposal of large quantity of flyash generated in power plants is a challenge for these industries.

These are the biological waste products which are readily available in nature. The most significant way of handling these waste materials is the recycling. The biological waste products can be used as viable adsorbents for the removal of heavy metal ions which is a feasible solution for the other environmental problem of waste disposal. Heavy metals (Cr, Ni, Cu, Pb, As, etc.) are very toxic in nature and harmful to the environment (Uysal and Irfan, 2007). When toxic heavy metals enter lakes, streams, rivers, oceans, and other water bodies, they get dissolved or lie suspended in water or get deposited on the bed. This results in the pollution of water whereby affecting aquatic ecosystems. All over the world, chromium is abundantly available in nature and has a dominant presence in most of the effluent streams as compared to other heavy metal ions. Cr(VI) is widely used in various industries such as dyes, ink, plastics, paint, primers, glass, ceramics, fungicides, rubber, fertilizers, tanning, mining, metallurgical, etc. (Namasivayam and Yamuna, 1995; Radovic, 2000; Kaewsarn and Yu, 2001; Selatnia et al., 2004; Sankararamakrishnan et al., 2006;. Kumar et al., 2007; Venditti et al., 2007; Malkoc and Nuhoglu, 2007). Cr(VI) is highly mobile and is considered acutely toxic, carcinogenic and mutagenic to living organisms, and hence more hazardous than other heavy metals. Therefore, it is necessary to eliminate Cr(VI) from the environment, in order to prevent the deleterious impact of Cr(VI) on ecosystem and public health. Various methods are available for the removal of Cr(VI) from wastewater streams, among which adsorption is found to be a highly promising treatment method to purify industrial effluent streams contaminated with Cr(VI) (Alvarez-Ayuso et al., 2007).

The removal of heavy metal ions from industrial wastewaters is considered as an important application of adsorption processes using suitable adsorbent (Radovic, 2000; Babu and Gupta, 2008b). All solid materials including metal and plastics have the adsorption capacity. However, the solids having a porous structure and high surface area will have higher adsorption capacities (Ngah et al., 2006). This indicates that the selection of an adsorbent is a key for the use of adsorption as a treatment technique for Cr(VI) removal. The cost associated with commercially available adsorbents increases the overall cost of the adsorption process. This led to the search for new strategies for developing low-cost materials which are available in abundance with a good capacity for Cr(VI) removal (Aggarwal et al., 1999; Karthikeyan et al., 2005; Khezami and Capart, 2005).

Adsorption of Cr(VI) on low-cost adsorbents depends on physicochemical surface properties (surface area, porosity, ionic groups on surface etc.) of the adsorbents. Waste


materials can be utilized as low-cost materials and thier surface properties can be enhanced by a proper physical and chemical activation procedure (Mohan and Pittman, 2006).

In this chapter, abundantly available solid waste materials such as tamarind seeds, neem leaves, sawdust, and flyash are activated and used as low-cost adsorbents for the removal of Cr(VI) from wastewater which also solves the problem of waste management simultaneously. The adsorbents are prepared by giving physical and chemical activation of waste materials. The performance of these developed adsorbents is evaluated by conduction batch and continuous experiments. The saturated adsorbents are regenerated to check the applicability for re-use of this material. The cost analysis is carried out for low-cost adsorbents and compared with commercially available activated carbon adsorbent to see the economic feasibility of the process.

2. MATERIALS AND METHODS

2.1. Adsorbent Preparation

2.1.1. Activated Tamarind Seeds (ATS) Tamarind seeds are collected from the wastage of Cafeteria and Guest House (BITS -

Pilani) of the institute. The seeds are washed with distilled water and dried at 1100C for 5 h. The dried seeds are crushed into small particles by using Jaw crusher. Crushed seeds are sieved by 10-12 mesh BSS screens. The particles, having an average size of 1.85 mm, are treated with concentrated sulphuric acid (98% w/w) in 1:1 weight ratio and kept in an oven maintained at a temperature range of 1500C for 24 h. The carbonized material is washed with distilled water to remove the free acid. Then it is soaked in 1% sodium bicarbonate solution for two days. The material is then washed with distilled water and dried again at 1000C for 5 h (Ramadevi and Srinivasan, 2005; Gupta and Babu, 2009b).

2.1.2. Activated Neem Leaves (ANL)

Neem leaves are collected from the neem trees of institute campus (BITS – Pilani). Neem leaves are washed repeatedly with distilled water to remove dust and soluble impurities. Initially leaves are kept for drying at room temperature in a shade for 6 h and then in an oven at 800C till they turn pale yellow. Then they are crushed and passed through 15-20 mesh BSS screens. Neem leaves are activated by treating in a ratio of one part of neem leaves to 1.8 parts by weight of concentrated HCl (36.5 wt%) and by keeping them in an oven maintained at a temperature range of 1500C for 24 h. The treated leaves are washed with distilled water to remove free acid and dried at 1000C for 5 h. Then 10 g of activated neem leaves are treated with 100 ml of 100 mmol/L copper solution (initial pH 8.5). The mixture is shaken for 24 h at 300C and filtered with membrane filter paper. Copper impregnated neem leaves are washed several times with distilled water until the filtrate is free from copper. Finally, the adsorbent is dried at 800C for 6 h (Manju et al. 1998; Babu and Gupta, 2008a). \


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2.1.3. Sawdust (SD) Sawdust is collected from the carpentry section of the institute workshop (BITS – Pilani).

It is washed repeatedly with distilled water to remove dust and soluble impurities. It is then kept for drying at room temperature in shade for 8 h (Gupta and Babu, 2009a).

2.1.4. Activated Flyash (AFA)

The flyash used in this study is collected from National Thermal Power Corporation (NTPC), Tanda. The flyash is washed with distilled water and dried at 1100C for 5 h. The activation of flyash is carried out by treating it with concentrated sulphuric acid (98% w/w) in 1:1 weight ratio and is kept in an oven maintained at a temperature range of 1500C for 24 h. Again it is washed with distilled water to remove the free acid.

2.1.5. Activated Carbon (AC)

The activated carbon used in the present study is produced from coconut shell which has high surface area and purchased from market (S.D. Fine Chemicals, New Delhi).

2.2. Batch Experiments All the chemicals used in the present study are of analytical grade (CDH and Merck). A

stock solution of 1000 mg/L of Cr(VI) is prepared by dissolving 2.8287 g of 99.9% potassium dichromate (K2Cr2O7) in distilled water and total volume of the solution is made up to the 1000 ml. This solution is diluted as required to obtain standard solutions.

The batch experiments are carried out in 100 ml borosil conical flasks. A specific amount of adsorbent is added in 25 mL of aqueous Cr(VI) solution, and then shaken for a predetermined period ranging from 17 – 67 h for different adsorbents (found out from kinetic studies) at 300C in water bath-cum-mechanical shaker. Afterwards, the resultant solution is filtered using filter paper. Adsorption isotherm study is carried out with different initial concentrations of Cr(VI) ranging from 20 to 800 mg/L while maintaining the adsorbent amount of 10 g/L.

Desorption studies are conducted by batch experiments using the saturated adsorbent obtained from adsorption studies to make it reusable. The 15 g of saturated adsorbents with Cr(VI) is first treated with 150 mL of 1 N NaOH solution for 1 day. After the NaOH treatment, adsorbents are separated from the solution and washed with distilled water. Washed adsorbents are further regenerated with 150 mL of 1 N HCl. The adsorbents are washed with distilled water and dried at room temperature (~300C) for 6 h. Desorption experiments are carried out with different initial concentrations of Cr(VI) from 50 to 500 mg/L while maintaining the adsorbent amount of 10 g/L and an initial pH value of 1 at 300C.

2.3. Continuous Experiments Continuous fixed-bed experiments are performed to remove Cr(VI) from wastewater

using activated tamarind seeds and sawdust adsorbents. The schematic diagram of the experimental set up is given in Fig. 1. Stock solutions of Cr(VI) are allowed to flow through


the fixed-bed of adsorbents (activated tamarind seeds and sawdust) through a valve, by which the flow rate is controlled. The parameters varied in the continuous experiments are flow rate, bed height, and inlet Cr(VI) concentration. The following fixed-bed experiments are performed by changing the parametric values as given in Table-1.

21

3

4

5

6

7

8

1 Stored Cr(VI) solution2 Outlet collection tank 3 Pump 4 Fixed-bed column 5 Feed of Cr(VI) solution 6 Outlet control valve 7 Inlet control valve 8 Base 9 Liquid Rotameter

9

Figure 1. Fixed-bed continuous adsorption experimental setup for Cr(VI) removal from wastewater

Table 1. Variation of different parameters for fixed-bed adsorption

S No Adsorbents Parameter values

1 Activated tamarind seeds

Initial concentration (ppm) Mass(g) Flow rates (mL/min) 100 25 10 100 25 15 100 25 20 100 20 10 100 15 10 150 25 15 200 25 15

2 Sawdust

50 25 10 50 25 15 50 25 20 50 30 10 50 15 10 75 25 10 100 25 10


143

2.4. Analysis of Cr(VI) Ions In the present study, di-pheynl carbazide method is used for the analysis of Cr(VI) in the

solution. This method has been reportedly used in many studies for analysis of Cr(VI) at low pH (Malkoc and Nuhoglu, 2007; Alvarez et al., 2007). The concentration of Cr(VI) ions in the effluent is determined spectrophotometrically by developing a purple-violet color with 1,5-diphenyl carbazide in acidic solution as a complexing agent (APHA, 1985). The absorbance of the purple-violet colored solution is read at 540 nm after 20 min. To calculate the deviation of analytical method of Cr(VI) concentration, calibration curve is prepared from standard solutions. The standard deviation obtained for the calibration curve is 0.00453 which is indicative of a good fit of the data and within the error limits of ±1.64 %. This ensured high confidence limits of the experimental measurements.

3. RESULTS AND DISCUSSION

3.1. Batch Studies Batch adsorption experiments are carried out to estimate the maximum adsorption

capacity of various adsorbents such as activated tamarind seeds, activated neem leaves, sawdust, activated flyash, and activated carbon for Cr(VI) removal from wastewater. The equilibrium studies are useful to obtain the adsorption capacity of adsorbents for Cr(VI). The obtained data from equilibrium studies can be represented in form of adsorption isotherm. Adsorption isotherms are important to describe the adsorption mechanism in term of the interaction of Cr(VI) with adsorbent surface. An adsorption isotherm is characterized by certain constant values that express the surface properties and affinity of the adsorbent towards Cr(VI). Fig. 2 shows the adsorption isotherms for Cr(VI) removal using different adsorbents. The maximum adsorption capacity of developed adsorbents are 30.5 mg/g, 62.9 mg/g, 41.9 mg/g, 42.3 mg/g, and 71.7 mg/g using activated tamarind seeds, activated neem leaves, sawdust, flyash, and activated carbon respectively. The obtained adsorption capacity for low-cost adsorbents is comparable with the commercially available adsorbent (Gupta and Babu, 2009a). This indicates that the waste material can be utilized for the removal of Cr(VI) from wastewater streams.

In an adsorption, atoms, ions or molecules of an adsorbate diffuse to surface of a solid, where they either bond with the solid surface or are held thereby weak intermolecular forces. The electrostatic, chemisorptive and functional group interactions define the affinity of an adsorbent for a specific adsorbate. In the present study, activated tamarind seeds, activated neem leaves, sawdust, activated flyash, and activated carbon are used as an adsorbent for the removal of Cr(VI) from aqueous solution. The understanding of the solute transport mechanism onto the adsorbent surface is very crucial.

The adsorption process mechanism for the solute transport onto the adsorbent surface follows three steps: (i) external mass transfer of solute from the bulk fluid to the film surrounding the adsorbent (ii) from film to the adsorbent surface and (iii) from surface to the internal sites followed by binding of metal ions to the active sites. Generally it is observed that, the rate of adsorption process is controlled by either step (ii) or step (iii). Physical


attachment of adsorbate to adsorbent is not the actual rate controlling step (Sharma and Bhattacharyya, 2004). In fact, the adsorption of solute on adsorbent also depends on the surface available for adsorption, ionic groups present on to the surface of adsorbent, and pH of the solution.

0 40 80 1200

10

20

30

40

50

60

70

Ads

orpt

ion

capa

city

(mg/

g)

Equilibrium concentration (mg/L)

ATS ANL SD AFA AC

Figure 2. Adsorption isotherms for Cr(VI) adsorption on different adsorbents at 300C

The specific surface area of all adsorbents is measured using BET surface area analyzer (Smart Sorb 92/93, Smart Instruments Co. Pvt. Ltd., Thane). The measured value of specific surface area is obtained in the range of 0.5 – 15.03 m2/g which is higher as compared to other low cost adsorbents. Larger specific surface area is one of the important reason for the higher uptake of Cr(VI) on adsorbents used in the present study. Specific surface area of activated carbon is found to be more than that of the other adsorbents.

Cr(VI) adsorption also depends on both microporous structure and surface functionality (Park and Jang, 2002). The adsorption of Cr(VI) is more effective on acid-treated adsorbents (Mattson and Mark, 1971). In the present study, activated neem leaves, activated tamarind seeds and activated flyash are treated using concentrated acids (HCl, H2SO4) at lower temperature (1500C). At this temperature, adsorbent surface generally develop acidic surface oxides and lower solution pH. It is well documented in the literature that chemically activated naturally occurring adsorbent has a higher surface area and shows a larger capacity of Cr(VI) removal.

The metallic ions uptake on adsorbents mainly depends on (1) the ions concentration, and (2) adsorption and reduction phenomena that simultaneously take place on the adsorbent surface (Stumm and Morgan, 1996; Park and Jang, 2002). These phenomena are strongly related to the solution pH. Various mechanisms such as electrostatic forces, ion-exchange, chemical complexation must be taken into account while discussing the mechanism of Cr(VI) adsorption on adsorbents. The solution pH plays a major role in the adsorption of Cr(VI) and it can be related to the type and ionic state of the functional group present on the adsorbent


145

surface (Mohanty et al., 2006). In the present study, the initial pH of solution is maintained in the range of 1-3. Within the solution pH range of 1.0–6.0, chromium ions can exist in different forms, such as Cr2O7−, HCrO4−, Cr3O10

2−, Cr4O132− of which HCrO4− predominates.

The lower solution pH results in the formation of H+ ions on the adsorbent surface. The increase of Cr(VI) adsorption is due to the electrostatic attraction between positively charged groups of adsorbent surface and the HCrO4- which is dominant at lower pH. Another reason for the higher adsorption of Cr(VI) on adsorbent may be due to the reduction of Cr(VI) to Cr(III) in acidic medium. As the size of Cr(III) ions is small, they can be easily replaced by the positively charged ions present on the adsorbent.

3.2. Desorption Studies The saturated adsorbent which contains Cr(VI) is not safe for disposal due to the stringent

environmental constraints. It is important and appropriate to propose a method for regeneration and reuse of adsorbent so as to reduce the load on environment in terms of disposal of polluted adsorbent. In the present study, adsorbents (activated tamarind seeds, activated neem leaves, sawdust, activated flyash and activated carbon) are regenerated and are used for the removal of Cr(VI) at different initial Cr(VI) concentration range used in batch study (same ranges chosen for fresh adsorbents). Figs. 3 to 7 show the comparison for the percentage removal of Cr(VI) using fresh and regenerated adsorbents. Fresh and regenerated activated tamarind seeds are used for the adsorption of Cr(VI) having 50 mg/L and 500 mg/L of initial Cr(VI) concentration and the percentage removal of Cr(VI) decreased from 98.02% to 68.85% and 97.02% to 64.46% respectively. The percentage removal using activated neem leaves and sawdust as adsorbents in the initial concentration ranging from 50 to 500 mg/ is achieved in the range of 99.7% to 97.9% and 98.85% to 97.42% using fresh adsorbent, 99.7% to 95.7% and 87.59% to 83.99% using regenerated adsorbents respectively. The percentage removal for activated flyash and activated carbon is obtained in the range of 81.9% to 52.5% and 99.6 to 88.7% for fresh adsorbents and 73.08% - 35.03% and 99.4% to 80% for regenerated adsorbents respectively. These results exhibit higher desorption efficiency by more than 95% for the removal of Cr(VI) for all the adsorbents excluding activated flyash. Since, Cr(VI) adsorption is an example of physical adsorption, it is possible to regenerate the adsorbents, which are considered for reuse. The adsorption of Cr(VI) onto the adsorbents is highly pH dependent. Hence, desorption of Cr(VI) is accomplished by increasing the solution pH.

The major problem of desorption process is the disposal of the acid and base solution obtained which contain high concentration of Cr(VI) (Gupta and Babu, 2009c). One of the methods to tackle this problem is precipitation of Cr(VI) from the aqueous solution using barium chloride. Addition of barium chloride solution to a Cr(VI) solution precipitates bright yellow barium chromate, as given by the following reaction (Eq. 1):

(s)BaCrO(aq)CrO(aq)Ba 4

24

2 →+ −+ (1) The precipitated solid volume (2 mL) is very less as compared to the volume of the

solution (100 mL). Also the chromium present in the complex solid can be recovered and


reused by the industries. So this way the problem of disposal which is a major disadvantage of adsorption process can be solved effectively and efficiently.

0 100 200 300 40060

70

80

90

100%

Rem

oval

of C

r (V

I)

Initial Cr (VI) Concentration (mg/l)

Fresh Regenerated

Figure 3. Comparison for the percentage removal of Cr(VI) using fresh and regenerated activated tamarind seeds

0 100 200 300 400 50092

93

94

95

96

97

98

99

100

% R

emov

al o

f Cr

(VI)

Initial Cr (VI) Concentration (mg/l)

Fresh Regenerated

Figure 4. Comparison for the percentage removal of Cr(VI) using fresh and regenerated activated neem leaves


147

50 100 150 200 250 30080

84

88

92

96

100

% R

emov

al o

f Cr(

VI)

Initial Cr(VI) concentration (mg/l)

Fresh Regenerated

Figure 5. Comparison for the percentage removal of Cr(VI) using fresh and regenerated sawdust

50 100 150 200 250 300 350 400 450

35

40

45

50

55

60

65

70

75

80

85

% R

emov

al o

f Cr(

VI)

Initial Cr(VI) concentration (mg/l)

Fresh Regenerated

Figure 6. Comparison for the percentage removal of Cr(VI) using fresh and regenerated activated flyash


0 100 200 300 400 500 600 700 800 90078

80

82

84

86

88

90

92

94

96

98

100

% R

emov

al o

f Cr(

VI)

Initial Cr(VI) Concentration (mg/l)

Fresh Regenerated

Figure 7. Comparison for the percentage removal of Cr(VI) using fresh and regenerated activated carbon

3.3. Continuous Column Studies

Fixed bed column experiments are performed in order to generate the data for obtaining

the breakthrough curves. The breakthrough time and the shape of the breakthrough curve are very important characteristics for the determination of the dynamic response of the adsorption column. The breakthrough curve shows the loading behavior of Cr(VI) to be removed from solution in a fixed-bed and is usually expressed in terms of adsorbed Cr(VI) concentration (Cad) as given by Eq. (2):

tb0ad CCC −= (2)

where, Cbo and Ct are inlet Cr(VI) concentration and outlet Cr(VI) concentration respectively. The normalized concentration defined as the ratio of effluent Cr(VI) concentration to inlet Cr(VI) concentration (Ct/Cbo) as a function of time or volume of effluent for a given bed height (Aksu and Gönen, 2004).

Effluent volume (Veff) can be calculated from Eq. (3):

feff QtV = (3)


149

where, tf and Q are the total flow time (min) and volumetric flow rate (ml/min), respectively. Total quantity of adsorbed Cr(VI) (qt, mg) in the column for a given inlet Cr(VI) concentration and flow rate is calculated from Eq. (4).

∫=

=

==ltt

td dtCQQA

qtota

0a

ct 10001000

(4)

The area under the breakthrough curve (AC) is obtained by plotting the adsorbed

concentration (Cad, mg/L) versus time (t, min). Total amount of Cr(VI) sent to column (mt) is calculated from Eq. (5):

1000to

tQtCm = (5)

Total percentage removal of Cr(VI) is calculated from Eq. (6):

100)( Cr(VI) of removal percentage Totalt

t ×=mq

S (7)

Equilibrium Cr(VI) uptake (qeq) (or maximum capacity) in the column is defined as the

total amount of Cr(VI) adsorbed (qt) per gram of adsorbent (W) at the end of total flow time, as given by Eq. (8):

Mq

qeqt= (8)

The empty bed residence time (EBRT) is the time required for the liquid to fill the empty

column. The EBRT is given by Eq. (9):

liquid theof rate flow Volumetric volumeBed EBRT = (9)

The adsorbent exhaustion rate (Ra) is the mass of adsorbent used (W) per volume of liquid

treated at breakthrough point which is given by Eq. (10):

ghbreakthrouat treatedvolumecolumnin adsorbent of mass )( rate exhaustionAdsorbent a =R (10)

The breakthrough time is usually defined as the time of adsorption when the effluent

concentration from the column is about 3–5% of the influent concentration. The different parameters such as time equivalent to the total capacity of column (tt), total flow time (tf), breakthrough time (tb), total or stoichiometric amount of Cr(VI) adsorbed (qt), maximum or equilibrium Cr(VI) uptake (qeq), total amount of Cr(VI) sent to the column (mt), total


percentage removal of Cr(VI) (S), EBRT, adsorbent exhaustion rate (Ra) and fraction of unused bed length (y) are evaluated for Cr(VI) removal using activated tamarind seeds and sawdust in fixed-bed adsorption column for different operating conditions and reported in Table 2 and 3. In the present study, the effect of influencing parameters such as flow rate, mass of adsorbent and inlet Cr(VI) concentration on breakthrough curve are examined (Gupta and Babu, 2009c).

3.3.1. Effect of Flow Rate

The flow rate of wastewater stream flowing through the column plays a major role in designing an adsorption column for the removal of Cr(VI) from wastewater. The breakthrough curves are obtained for Cr(VI) adsorption by activated tamarind seeds and sawdust at different flow rates (10, 15 and 20 ml/min) by maintaining the constant adsorbent amount of 25 g and initial Cr(VI) concentration 100 and 50 mg/L respectively as shown in Figs. 8 and 9. It is clear from these two profiles that as the flow rate increases, breakthrough time is obtained earlier. The breakthrough times are obtained as 210, 115 and 80 min for activated tamarind seeds and 630, 440 and 240 min for sawdust for flow rate values of 10, 15 and 20 ml/min respectively for Cr(VI) removal. The total time, corresponds to stoichiometric capacity of the column, is found to be decreasing with increase in the flow rate as shown in Table 2 and 3 for both the adsorbents. The total percentage removal of Cr(VI) for the fixed-bed adsorption column is decreasing from 50 – 45.1% and 74.5 to 66.6% with increase in flow rate from 10 – 20 ml/min for activated tamarind seeds and sawdust respectively (Table 2 and 3). The fraction of unused bed length at breakthrough point shows an increasing trend with the increase in flow rate for both the adsorbents. It is observed from Figs. 2 and 3 that the breakthrough curve becomes steeper when the flow rate is increased.

The decrease in breakthrough time with an increase in flow rate may be because of a fixed saturation capacity of the bed based on same driving force giving rise to a shorter time for saturation at higher flow rates. The probable reason for the increase in steepness of breakthrough curve and decrease in removal efficiency (50 – 45.1% for activated tamarind seeds and 75.5 – 66.6% for sawdust) with increase in flow rate (10 – 20 ml/min) is that, when the residence time of Cr(VI) in the column is not long enough for adsorption equilibrium to be reached at that flow rate, the Cr(VI) solution leaves the column before equilibrium occurs. And hence the contact time for Cr(VI) using activated tamarind seeds and sawdust is very short at higher flow rates, causing a reduction in the removal efficiency which can be seen from Table 2 and 3.

3.3.2. Effect of Mass of Adsorbent

Effect of mass of adsorbent (activated tamarind seeds and sawdust) is also studied for 15, 20 and 25g for activated tamarind seeds and 15, 25 and 30 g using sawdust. The breakthrough curves obtained for this study are shown in Figs. 10 and 11. It can be seen from Figs. 10 and 11, as the mass of adsorbent increases, breakthrough time gets delayed. The breakthrough times are obtained as 110, 115 and 210 min and 310, 630 and 850 min for 15, 20 and 25 g of activated tamarind seeds and 15, 25 and 30 g of sawdust respectively. The total time corresponds to the stoichiometric capacity of the column is found to be increasing from 310 to 640 min and 660 to 1240 min with increase in the mass of adsorbents from 15 – 25 g and 15 – 30 g for activated tamarind seeds and sawdust respectively (Tables 2 and 3). The total percentage removal of Cr(VI) for the fixed-bed adsorption column increasesd from 39.7 –


151

50.0% and 59.4 to 74.6% with increase in mass of adsorbent from 15 – 25 g for activated tamarind seeds and 15 – 30 g for sawdust (Tables 2 and 3). The fraction of unused bed length at breakthrough point is obtained as approximately same (within the range of 0.64 – 0.67) using activated tamarind seeds. But it is found to decrease in the range of 0.53 to 0.31 for sawdust amount of 15 to 30 g (Table 3). It is observed from Figs. 10 and 11 that the breakthrough curve becomes steeper when mass of adsorbent is decreased. The rate of adsorbent exhaustion decreases in the range of 13.6 to 11.9 g/L and 4.8 to 3.5 g/L with increase in mass of activated tamarind seeds and sawdust respectively.

It is evident from Figs. 10 and 11 that with an increase in the amount of adsorbent, the capacity of the adsorption column to adsorb Cr(VI) increases which results in obtaining the breakpoint time early.

3.3.3. Effect Of Initial Cr(VI) Concentration

In the adsorption of Cr(VI), a change in initial Cr(VI) concentration affects the operating characteristics of the fixed bed adsorption column. The breakthrough curves obtained by changing initial Cr(VI) concentration from 100 to 200 mg/L for activated tamarind seeds and 50 to 100 mg/L for sawdust are shown in Figs. 12 and 13. It is observed from Fig. 12, that as the initial Cr(VI) concentration increases from 100 to 200 mg/L, the break point time decreases from 210 to 45 min. Similar trend is observed from Fig. 13 for sawdust where decrease in break point time is 630 to 280 min. The total time corresponds to stoichiometric capacity of the column is found to be decreasing from 640 to 210 min and 1080 to 740 min with increase in the initial Cr(VI) concentration from 100 – 200 mg/L and 50 – 100 mg/L for activated tamarind seeds and sawdust respectively (Tables 2 and 3). The total percentage removal of Cr(VI) for the fixed-bed adsorption column is decreasing from 50.0 – 30.4% and 74.5 to 55.6% with an increase in initial Cr(VI) concentration for activated tamarind seeds and sawdust (Tables 2 and 3). The fraction of unused bed length at breakthrough point is obtained in the range of 0.67 – 0.78 and 0.42 to 0.62 for sawdust for 100 – 200 mg/L and 50 – 100 mg/L of initial Cr(VI) concentration using activated tamarind seeds and sawdust (Tables 2 and 3). The rate of adsorbent exhaustion increases in the range of 11.5 to 37 g/L and 3.9 to 8.9 g/L with an increase in initial Cr(VI) concentration using activated tamarind seeds and sawdust respectively.

Table 2. Different parameters for the Cr(VI) removal using activated tamarind seeds in

a fixed-bed adsorption column for different operating conditions

S No Cb0 (mg L-1)

W (g) Q (mL min-1)

tt (min)

tf (min)

tb (min)

qt (mg)

mt (mg)

S (%) EBRT Ra (g L-1) y

1 100 25 10 640 1280 210 640 1280 50.0 2.25 11.9 0.672 100 25 15 440 1000 115 690 1500 46.0 1.50 14.5 0.743 100 25 20 320 710 80 640 1420 45.1 1.12 15.6 0.754 100 20 10 430 930 155 430 930 46.2 1.80 12.9 0.645 100 15 10 310 780 110 310 780 39.7 0.76 13.6 0.656 150 25 15 300 920 100 675 2070 32.6 1.50 16.6 0.667 200 25 15 210 690 45 630 2070 30.4 1.50 37.0 0.78


The increase in initial Cr(VI) concentration led to reach bed saturation earlier and obtaining breakthrough time quickly due to relatively slower transport due to a decrease in diffusion coefficient and decreased mass transfer coefficient at low Cr(VI) concentration (Aksu and Gönen, 2004). Binding sites, quickly filled at higher initial concentration, results in a decrease in the breakthrough time. It is observed that the adsorbent get saturated faster at higher concentrations of adsorbate due to the higher rate of adsorbent exhaustion at higher Cr(VI) concentration. For a low initial Cr(VI) concentration, breakthrough occurs very late and surface of the adsorbents is saturated with Cr(VI) at a relatively longer time. This fact is probably associated with the availability of adsorption sites around or inside the adsorbent particles that are able to capture the Cr(VI) at lesser retention time.

Table 3. Different parameters for the Cr(VI) removal using sawdust in a fixed-bed

adsorption column for different operating conditions

S No Cb0 (mg L-1)

W (g) Q (mL min-1)

tt (min) tf (min) tb (min)

qt (mg) mt (mg)S (%) EBRT (s)

Ra (g L-1)

y (-)

1 50 25 10 1080 1450 630 540 725 74.5 20 3.9 0.422 50 25 15 860 1240 440 645 930 69.4 13.3 3.8 0.483 50 25 20 660 990 240 660 990 66.6 10 5.2 0.634 50 30 10 1260 1690 850 630 845 74.6 24 3.5 0.315 50 15 10 660 1110 310 330 555 59.4 12 4.8 0.536 75 25 10 940 1470 420 705 1102 63.9 20 5.9 0.557 100 25 10 740 1330 280 740 1330 55.6 20 8.9 0.62

0 200 400 600 800 1000 12000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

C/C

0

Time (min)

Q = 10 mL/min Q = 15 mL/min Q = 20 mL/min

Figure 8. Effect of flow rate on breakthrough curve for Cr(VI) removal using activated tamarind seeds (C0 = 100 mg/L and W = 25 g)


153

0 200 400 600 800 1000 1200 14000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

C/C

0

Time (min)

Q = 10 ml/min Q = 15 ml/min Q = 20 ml/min

Figure 9. Effect of flow rate on breakthrough curve for Cr(VI) removal using sawdust (C0 = 50 mg/L and W = 25 g)

0 200 400 600 800 1000 12000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

C/C

0

Time (min)

Mass = 15 g Mass = 20 g Mass = 25 g

Figure 10. Effect of mass of adsorbent on breakthrough curve for Cr(VI) removal using activated tamarind seeds (C0 = 100 mg/L and Q = 10 mL/min)


0 200 400 600 800 1000 1200 1400 1600 18000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

C/C 0

Time (min)

Mass = 15 g Mass = 25 g Mass = 30 g

Figure 11. Effect of mass of adsorbent on breakthrough curve for Cr(VI) removal using sawdust (C0 = 50 mg/L and Q = 10 mL/min)

0 200 400 600 800 10000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

C/C

0

Time (min)

Cb0 = 100 ppm Cb0 = 150 ppm Cb0 = 200 ppm

Figure 12. Effect of initial Cr(VI) concentration on breakthrough curve for Cr(VI) removal using activated tamarind seeds (W = 25 g and Q = 15 mL/min)


155

0 200 400 600 800 1000 1200 1400 16000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

C/C 0

Time (min)

Cb0

= 50 ppm Cb0 = 75 ppm Cb0 = 100 ppm

Figure 13. Effect of initial Cr(VI) concentration on breakthrough curve for Cr(VI) removal using sawdust (W = 25 g and Q = 15 mL/min)

3.4. Cost Analysis

Cost analysis is the most important criteria for the selection of any treatment process for

the removal of heavy metals. Adsorption process cost is mainly dependent on the cost of adsorbent used for the removal of metals from wastewater. The most common adsorbent used for the removal of Cr(VI) is activated carbon which is quite expensive. It becomes more problematic for developing countries to afford the cost and demand of activated carbon. Hence, low cost materials are sorely needed which are comparable to activated carbon in terms of adsorption capacity, economic feasibility and should be locally available. Therefore, in the present work, an attempt is made to analyze the cost of low cost adsorbents such as activated tamarind seeds, activated neem leaves, sawdust and activated flyash. The cost for the preparation of these adsorbents is calculated based on the procedure given in section 2.1. The breakup cost of each step (including physical and chemical activation procedure) and the total cost for the preparation of each adsorbent is given in Table 4. The commercially available adsorbent, activated carbon, is purchased for Rs. 500 per kg in present studies. Based on adsorption capacity obtained in batch study for all adsorbents, the cost of each adsorbent is calculated for the removal of 1 g of Cr(VI) from wastewater streams (Table 5).

It is found that the cost of sawdust per gram of Cr(VI) removal is Rs 0.105 which is the least when compared with the cost of other developed adsorbents. It is due to the fact that no chemical activation costs are involved in the preparation of sawdust. It is furthermore seen that it has high adsorption capacity (41.9 mg/g) for Cr(VI) removal thus making it the most economically feasible adsorbent. The costs for removal of 1 g of Cr(VI) from waste waster using adsorbents such as activated tamarind seeds, activated neem leaves and activated flyash


are Rs. 1.276, Rs.1.289 and Rs. 1.640 respectively. This indicates that the cost associated with these adsorbents is quite lesser when compared to that of commercial activated carbon (Rs 6.97).

Table 4. Breakup and total cost for preparing 1 kg of adsorbent from naturally

available materials

S No Material Unit Cost (Rs.)

Activated tamarind Seeds

Activated neem leaves Sawdust Activated flyash

Amount usedNet Price (Rs.)



Amount used Net Price (Rs.)

1 HCl 9.84 - - 1.8 kg 17.69 - - - -

2 Copper solution 348.79 per kg - - 0.063 kg 21.97 - - - -

3 H2SO4 4.329 per kg 1 kg 4.33 - - - - 1 kg 4.33

4 NaHCO3 0.178 per liter 5 liter 0.89 - - - - - -

6 Cost of Drying 1 5 per kWh

0.83 kWh (1100C for 5 h)

4.16 0.83 kWh (800C for 5 h)

5.0 300C for 8 h (normal conditions)

4 0.83 kWh (1100C for 5 h) 4.16

7 Cost of drying 2 5 per kWh

0.83 kWh (1100C for 5 h)

4.16 0.83 kWh (1100C for 5 h)

4.16 - - 0.83 kWh (1100C for 5 h) 4.16

8 Cost of heating 1 5 per kWh

4 kWh (1500C for 24 h)

20 4 kWh (1500C for 24 h)

20 - - 4 kWh (1500C for 24 h)- 20

9 Cost of Heating 2

5 per kWh - -

0.83 kWh (800C for 6 h)

5 - - - -

10 Net cost (Rs.) 33.54 73.82 4 32.65

11 Other overhead costs (10% of net cost)

3.354 7.382 0.4 3.265

Total Cost (Rs.) 36.89 81.2 4.4 35.92

Table 5. Cost of adsorbent for the removal of 1 g of Cr(VI) from wastewater

S No Adsorbent Adsorption capacity (mg/g)

Cost of Adsorbent (Rs./kg)

Cost of adsorbent for removal of 1 g of Cr(VI) (Rs.)

1 Activated tamarind seeds 28.9 36.89 1.276

2 Activated neem leaves 62.97 81.2 1.289

3 Sawdust 41.9 4.4 0.105 4 Activated flyash 21.9 35.92 1.640 5 Activated carbon 71.7 500 6.97

CONCLUSIONS The solid waste generated from various sources can be re-used or recycled. The solid

waste materials such as tamarind seeds, neem leaves, sawdust and flyash are recycled in the form of adsorbents and found to be good adsorbents for the removal of Cr(VI) from


157

wastewater. The maximum adsorption capacity is found for activated neem leaves (62.9 mg/g) among low cost adsorbents which is quite appreciable as compared to commercially available activated carbon which is showing maximum adsorption capacity of 71.7mg/g. The maximum adsorption capacity of other developed adsorbents are 30.5 mg/g, 41.9 mg/g and 42.3 mg/g using activated tamarind seeds, sawdust and activated flyash respectively. The problem of disposal of used adsorbent bed with hazardous metal such as Cr(VI) is appropriately dealt with. It is found that all adsorbents show a higher desoprtion efficiency by more than 95% for the removal of Cr(VI) except flyash. A feasible solution is proposed, for the disposal of contaminant (acid and base solutions) containing high concentration of Cr(VI) obtained during desorption process. The fixed-bed column experiments are performed using activated tamarind seeds and sawdust and it is observed that the breakthrough point is obtained earlier by increasing the flow rate, decreasing the mass of adsorbent and increasing the initial Cr(VI) concentration. The economic feasibility study carried out of low cost adsorbents over activated carbon based on a detailed cost analysis showed positive results pointing to a tremendous potential these low cost adsorbents have for the removal of heavy metals. Sawdust found to be the cheapest adsorbent for the removal of Cr(VI). This study demonstrated that the environmental concern about the solid waste management and heavy metals removal can be solved simultaneously.

REFERENCES

Aggarwal, D., Goyal, M., Bansal, R.C., 1999. Adsorption of chromium by activated carbon from aqueous solution. Carbon, 37, 1989–1997.

Aksu, Z., Gönen, F.D., 2004. Biosorption of phenol by immobilized activated sludge in a continuous packed bed: prediction of breakthrough curves. Process Biochemistry, 39, 599-613.

Alvarez, P., Blanco, C., Granda, M., 2007. The adsorption of chromium (VI) from industrial wastewater by acid and base-activated lignocellulosic residues. Journal of Hazardous Materials, 144, 400–405.

Alvarez-Ayuso, E., Garcia-Sanchez, A., Querol, X., 2007. Adsorption of Cr(VI) from synthetic solutions and electroplating wastewaters on amorphous aluminium oxide. Journal of Hazardous Materials, 142, 191–198.

APHA, 1985. Standard methods for the examination of water and wastewater. 16th ed., APHA, AWWA, WPCF, Washington, D.C.

Babu, B. V., Gupta S., 2008a. Adsorption of Cr(VI) using Activated Neem Leaves as an Adsorbent: Kinetic Studies. Adsorption, 14, 85-92.

Babu, B. V., Gupta, S., 2008b. Removal of Cr(VI) from Wastewater Using Activated Tamarind Seeds as an Adsorbent. Journal of Environmental Engineering and Science, 7, 553-557.

Gupta, S., Babu B. V., 2009a. Removal of toxic metal Cr(VI) from aqueous solutions using sawdust as adsorbent: Equilibrium, kinetics, and regeneration studies. Chemical Engineering Journal, 150, 352-365.


Gupta, S., Babu B. V., 2009b. Utilization of Waste Product (Tamarind Seeds) for the Removal of Cr(VI) from aqueous solutions: Equilibrium, Kinetics, and Regeneration Studies. Journal of Environmental Management, 90, 3013-3022.

Gupta, S., Babu B. V., 2009c. Modeling, simulation, and experimental studies for continuous Cr(VI) removal from aqueous solutions using sawdust as an adsorbent. Bioresource Technology, 100, 5633-5640.

Kaewsarn, P., Yu, Q., 2001. Cadmium(II) removal from aqueous solution by pretreated biomass of marine alga padina sp. Environmental Pollution, 112, 209–213.

Karthikeyan, T., Rajgopal, S., Miranda, L.R., 2005. Chromium (VI) adsorption from aqueous solution by Hevea Brasilinesis sawdust activated carbon. Journal of Hazardous Materials, 124, 192–199.

Khezami, L., Capart, R., 2005. Removal of chromium (VI) from aqueous solution by activated carbons: kinetic and equilibrium studies. Journal of Hazardous Materials, B 123, 223–231.

Kumar, R., Bishnoi, N. R., Bishnoi, G. K., 2007. Biosorption of chromium (VI) from aqueous solution and electroplating wastewater using fungal biomass. Chemical Engineering Journal, 135, 202-208.

Malkoc, E., Nuhoglu, Y., 2007. Potential of tea factory waste for chromium (VI) removal from aqueous solutions: Thermodynamic and kinetic studies. Separation and Purification Technology, 54, 291–298.

Manju, G. N., Raji C., Anirudhan, T. S., 1998. Evaluation of Coconut Husk Carbon for the Removal of Arsenic From Water. Water Research, 32, 3062-3070.

Mattson, J. S., Mark Jr, H. B., 1971. Activated carbon, Marcel Dekker, New York. Mohan, D., Pittman Jr, C. U., 2006. Activated carbons and low cost adsorbents for

remediation of trivalent and hexavalent chromium from water. Journal of Hazardous Materials, B137, 762–811.

Mohanty, K., Jha, M., Meikap, B.C., Biswas, M.N. 2006. Biosorption of Cr(VI) from aqueous solutions by Eichhornia crassipes. Chemical Engineering Journal, 117, 71–77.

Namasivayam, C., Yamuna, R. T., 1995. Adsorption of Chromium (VI) by a Low-Cost Adsorbent: Biogas Residual Slurry. Chemosphere, 30, 561–578.

Ngah, W. S. W., Kamari, A., Fatinathan, S., 2006. Adsorption of chromium from aqueous solution using chitosan beads. Adsorption, 12, 249 – 257.

Park, S. J., Jang, Y. S., 2002. Pore Structure and Surface Properties of Chemically modified activated carbons for adsorption mechanism and rate of Cr(VI). Journal of Colloid Interface Science, 249, 458–463.

Radovic, L.R., 2000. Chemistry and physics of Carbon. Marcel Dekker Inc., 27, 227–405. Ramadevi, A., Srinivasan, K., 2005. Agricultural solid waste for the removal of inorganics:

Adsorption of mercury (II) from aqueous solution by Tamarind nut carbon. Indian Journal of Chemical Technology, 12, 407 – 412.

Sankararamakrishnan, N., Dixit, A., Iyengar, L., Sanghi, R., 2006. Removal of hexavalent chromium using a novel cross linked xanthated chitosan. Bioresource Technology, 97, 2377–2382.

Selatnia, A., Bakhti, M. Z., Madani, A., Kertous, L., Mansouri, Y., 2004. Biosorption of Cd(II) from aqueous solution by a NaOH-treated bacterial dead Streptomyces rimosus biomass. Hydrometallurgy, 75, 11–24.


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Sharma, A., Bhattacharyya, K. G., 2004. Adsorption of Chromium (VI) on Azadirachta Indica (Neem) Leaf Powder. Adsorption, 10, 327–338.

Stumm, W., Morgan, J.J., 1996. Aquatic Chemistry, 3rd edition., Wiley & Sons, New York. UNEP. 1996. Report of the Regional Consultations held for the first Global Environment

Outlook. UNEP. Nairobi. Uysal, M., Irfan, A., 2007. Removal of Cr(VI) from industrial wastewaters by adsorption Part

I: Determination of optimum condition. Journal of Hazardous Materials, 149, 482 – 491. Venditti, F., Ceglie, A., Palazzo, G., Colafemmina, G., Lopez, F., 2007. Removal of chromate

from water by a new CTAB–silica gelatin composite. Journal of Colloid and Interface Science, 310, 353–361.


Chapter 6

CAN WASTE-TO-ENERGY OF AS-RECEIVED OR PRE-PROCESSED (RDF/SRF) MUNICIPAL SOLID WASTES SUPPORT THE ELECTRICITY GENERATION SECTOR?

EU EXPERIENCE AND A CASE STUDY WITH TWO DIFFERENT SENARIOS FOR GREECE

C.S. Psomopoulos*

ABSTRACT

The European Union Landfill Directive (1999/31 EC) requires reducing the amount of wastes landfilled by means of recycling, composting and energy recovery. Accordingly, the member states are gradually adopting Waste-to-Energy (WTE) and also mechanical-biological treatment (MBT) methods for the recovery of energy and materials from municipal solid wastes (MSW). Under these conditions Waste to energy facilities have a clear dual role in the context of sustainable waste management: From the one hand, they have to reduce the volume and hazardousness of wastes that can receive no further treatment prior to disposal; on the other, they have to make the most out of the energy content of the treated wastes, in order to improve the environmental performance of the whole process. WTE facilities can combust either as-received MSW (stoker or “mass burn” technology) or pre-processed “refuse-derived” fuels (RDF or SRF) equipped with adequate Air Pollution Control (APC) systems. The latter have higher calorific values and can be used both in dedicated WTE plants and as fuel substitutes in cement kilns and coal-fired power plants.

This chapter presents firstly an overview of the state-of-the-art in this field, highlighting the energy recovery part of the procedure as well as the flue gas treatment. The surveyed technologies fall under the following categorization:

Pretreatment of wastes for subsequent thermal treatment and energy recovery; waste

derived fuels (refuse derived fuel, packaging derived fuel, solid recovered fuel).

* T.E.I. Piraeus, Dept. of Electrical Engineering, 250 Thivon str & P. Rali Ave, GR-12244, Egaleo, Greece, E-mail:

[email protected], Tel +302105381182, Fax: +302105381321

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Conventional incineration of as received wastes and residues with energy recovery and flue-gas treatment.

Co-firing of waste derived fuels in industrial furnaces. Secondly this chapter examines the energy generation potential, focusing on

electricity, for two scenarios for waste to energy in Greece, based on the National Plan for Waste Management of the Ministry of Environment. In the first scenario it is examine only production and utilization of Refuse Derived Fuels (RDF) and Solid Recovered Fuel from MSW, and the second scenario the application of the mass burn and the RDF/SRF options, for managing post-recycling MSW, both in the light of experience gained in E.U. and the U.S..

1. INTRODUCTION Economic development is always accompanied by higher consumption of goods and

services and attendant increased generation of solid wastes that need to be disposed somehow. The waste generation today is higher than the economic growth and different waste management methods aim to reduce the significant environmental and economic impact of this fact. In the generally accepted waste hierarchy, the first priority is for waste reduction, followed by recycling and also composting of clean biodegradable organic wastes (food and yard wastes). The EU promotes recycling over other waste treatment methods for recovering materials and energy, the latter either in the form of electricity/heat or production of waste derived fuels. In this way, physical resources are protected since paper, metals, glass, plastics that are recovered from the waste stream demand less resources and energy than the use of “virgin” materials. Also, the energy recovery provides electricity and heat to industrial, commercial and domestic consumers, and also minimizes the volume of wastes to be disposed. The goal of combining these approaches, as well as the additional option of composting, is to minimise the loss of resources to final inert landfill disposal [1-7].

Landfilling is the most common method for waste management in many EU Member States and in some cases this dependency exceeds 80%. The EU Landfill Directive of 1999 obliges Member States to progressively reduce the amount of organic waste going to landfill to 35% of the 1995 levels within 15 years aims to reduce such a loss of resources. This clear policy direction has put emphasis on waste management systems that increase and optimise the recovery of resources from waste – whether as materials or as energy. Accordingly, the member states are adopting Waste-to-Energy (WTE) and also mechanical-biological treatment (MBT) methods for the recovery of energy and materials from municipal solid wastes (MSW) and non – hazardous industrial wastes. Through the processes involved during MBT, several output streams are generated, including a compost-like digested material, a high calorific value fuel stream (15-18 MJ/kg), metals, and residuals. If the procedure includes anaerobic digesters biogas can be generated also. WTE facilities can combust either as-received MSW (stoker or “mass burn” technology) or pre-processed in MBT facilities, “refuse-derived” fuels (RDF or SRF). The latter have higher calorific values than as-received MSW and can be used both in dedicated WTE plants and as fuel substitutes in cement kilns and coal-fired power plants. In order to protect the environment from the emissions in energy recovery facilities, EU adopted the regulation on emission limits from waste incineration

Can Waste-to-Energy of as-Received or Pre-Processed (RDF/SRF)…

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plants (Directive 2000/76/EC), while the regulation on renewable energy sources (RES) (Directive 2001/77/EC), includes the biogenic fraction of wastes [1, 8-13].

This chapter presents electricity generation potential from MSW, by examining the application of mass burn and RDF/SRF utilisation options, as a part of the generation fuel mix. Furthermore one case study with two scenarios are presented for managing MSW in Greece (the only EU-Member State along with Ireland that do not have incineration), in the light of experience gained in E.U. and the U.S., and the National Plan for Waste Management of the Greek Ministry of Environment. The case studies showed that the potential electricity generation could be a notable percentage of the total annual electricity consumption.

2. MSW INCINERATION

2.1. Current Status i Europe The EU Landfill Directive of 1999 obliges Member States to progressively reduce the

amount of organic waste going to landfill to 35% of the 1995 levels within 15 years aims to reduce such a loss of resources. This clear policy direction has put emphasis on waste management systems that increase and optimise the recovery of resources from waste – whether as materials or as energy. Due to these restrictions in landfilling, thermal treatment plays an important role in European waste management systems, whereas an increasing role can be expected in the future. Thus, the Waste Incineration Directive is fundamental, as all EU member states have to meet the same incineration standard from now on. Furthermore, it is necessary consider the amount energy recovered from MSW incineration, as well the differences that exist in MSW management infrastructures between the European countries [1-3, 6-8, 12-17].

43.348.4

59.7

41.2

57

78.3

47

82.6

96.9

2.7 0.02

12.78.47.1

10.711.3

22.4

7.45.7

0

10

20

30

40

50

60

70

80

90

100

Aus

tria

Bel

gium

Den

mar

k

Fra

nce

Ger

man

y

Net

herla

nds

Nor

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Swed

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Switz

erla

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Fin

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Italy

Portu

gal

Spai

n

Uni

ted

Kin

dom

Cze

ch R

epub

lic

Hun

gary

Latv

ia

Pola

nd

Slov

akia

%

Figure 1. MSW incinerated as percentage of the total produced in European countries.

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Figures 1 and 2 illustrate the differences of the relevance of waste incineration in the European countries. While most of the highly industrialized countries of Western and Northern Europe incinerate more than 40 % of MSW the rate in the new member states is less than 10 %. Greece and Ireland do not include Waste-to-Energy in their MSW management systems. In Switzerland nearly the entire amount of MSW is being used in WTE plants [1,8, 11, 14-17].

In Europe, a wide variety of WTE plant sizes and types are operating at present. Finland and Poland for example have small installations (capacity = 50 kt/a) whereas the Netherlands have the largest installations with an average capacity of 500 kt/a. The most commonly used technology for MSW incineration is the grate furnace, but other proven technologies exist as well, such as fluidized bed furnaces. Figure 3 shows the incineration plants in Europe and Figure 4 the growth in million ton/y capacities [1, 6-8, 15-118].

1.27

2.15

3.1

22.37

17.15

4.79

0.83

2.35

2.58

1.4

24.09

4.19

13.1

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4.18

1.13

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1.02

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1.04

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0.39

1.94

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0.08

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0.94

1.48

2.64

0.21

0.35

0.03

0.002

0.13

24.61

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28

Austria

Belgium

Denmark

France

Germany

Netherlands

Norway

Sweden

Switzerland

Finland

Italy

Portugal

Spain

United Kindom

Czech Republic

Hungary

Latvia

Poland

Slovakia

Mt/y

Figure 2. Total and incinerated amount of MSW in European countries


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Depending on the design the energy is recovered usually as cogeneration of heat and electricity, but the each percentage presents significant differences between European countries. A typical example can be given by comparing Germany and Italy. There were 67 MSW incinerators in operation in Germany at the end of 2005 with total capacity of these units is approximately 16,5 million ton/y; all wastes are processed in facilities with energy recovery and heat and/or electricity generation. In Germany, 71,7 % of the total energy potential was used for heat generation (16370 GWh) and approximately 29,3 % for electricity generation (6800 GWh). In Italy, the amounts were smaller, where 41 MSW incinerators in operation at the end of 2005 with total capacity of these units is approximately 3,1 million ton/y, only 19,6 % of the total energy potential was used for heat generation (575 GWh) while approximately 80,4 % for electricity generation (2356 GWh). Table 1 shows the number of incinerators, the MSW quantity incinerated and the energy recovered as heat and electricity, in selected European countries [1, 6-8, 15-23].

Figure 3. Distribution of Waste-to-Energy plants operating in Europe in the year 2006; numbers of facilities and millions of tons MSW incinerated annually are also indicated (source : www.cewep.com)

Beside the volume reduction and mineralization of waste, energy recovery has increasingly become an important objective. Due to the fact that waste has a role as a renewable energy source, it is attracting more and more attention in this respect. Nevertheless not all countries considered a part of the MSW as renewable energy source because of the other materials included in the mixed waste streams [1, 5-8, 15-17, 19-23].

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Table 1. Number of incinerators, quantity of MSW (incinerated and total) and energy recovered as heat and electricity.

EU Member State Number of incinerators

Quantity of MSW incinerated (total) Mton/yr

Energy Recovered in GWh (electricity/heat)

Austria 8 1.46 (3.14) 189/2094 Belgium 1 0.9 (3.38) 320/1800 Germany 67 16.5 (20.5) 6800/16370 Denmark 30 NA (3.4) 1447/6582 Spain 1 1.76 (22.7) 982/640 Italy 47 3.1 (31.1) 2356/575 Holland 11 5.4 (10.2) 2495/2646 Hungary 1 0.3 (4.7) 120/133 Portugal 3 1.1 (4.55) 593/ΝΑ Sweden 29 3.2 (4.2) 739/855 Czech Republic 3 0.4 (4.4) 17/34

32.736.5

4044.1

48 50.6 5254.9

64.3

72.4

0

10

20

30

40

50

60

70

80

1996 1997 1998 1999 2000 2001 2002 2003 2006 2009

Figure 4. Rise of capacity of incinerator plants in Europe in million ton/y. Greece and Ireland are the only EU countries that do not have incineration as part of their waste management strategies (source : Frost & Sallivan)

2.2. Common Used Technologies

MSW incinerators should be burned various waste categories with several characteristics.

This requires specifically designed combustors. On principle, a waste incineration plant consists of the main thermal process and the flue-gas cleaning. The thermal process usually


167

includes the following systems: storage, handling and waste feeding, followed by the combustion in the furnace, as well as the heat recovery with steam and electricity production [6-8, 13, 14-18, 21-24].

Table 2. New waste-to-energy systems in Europe with increased energy efficiency; the

estimated produced and exported electricity percentages are referred to the energy input of the waste (source: [24])

Plant Brescia # 1+2 (Italy) Brescia # 3

(Italy) Amsterdam # 5+6 (Netherlands)

Start-up 1998 2004 2007

Combustion system MARTIN reverse-acting grate

MARTIN reverse-acting grate MARTIN horizontal grate

Special feature Optimized for high efficiency

Optimized for high efficiency

Intermediate steam superheating and water condenser

Fuel MSW, sewage sludge, biomass

Biomass, sewage sludge MSW

Steam pressure (bar) 61 73 130 Superheated steam temperature (°C) 450 480 440

Gas temperature at boiler outlet (°C) 135 135 180 (135°C with additional heat

recovery) Electricity (%gross) 27 28 34 Electricity (%net) 24 25 30

The most common technology for the incineration of MSW is the moving grate system.

As an example, in Germany, more than 90% of MSW incinerators are grate firing systems. These systems require minimal pre-processing and are implemented in facilities of varying grate size from 2 t/h to more than 40 t/h. A disadvantage of the grate systems is the large excess of air (λ=1.6-1.8) which leads to energy losses over the stack by the flue gas. Independent of the incineration system, the combustion temperature has to be in the range of 850-1100 °C. The lower limit guarantees the complete destruction of harmful organic chemicals and the upper limit should prevent from unacceptable high production of thermal NOx. The efficiency of MSW incinerators with electricity generation is around 20% and can go up to 30% usually. Compared to fossil fired plants these values are low caused mainly due to the low steam parameters of approximately 400°C and 40 bar. Recent technological improvements have shown that the electricity generation can reach up to 34% while the steam pressure can reach 130bar 440°C (Table 2) [6-8, 13, 14-18, 21-24].

2.2.1. Mass-Burn Plants

Mass burning of MSW with power generation, in WTE plants is practiced widely in the EU, US and other developed countries. Requires minimum pre-processing of waste, mainly removal of bulky items like “white goods”, although in many facilities metals are recovered after shredding of the garbage bags, prior to charge the incinerator. The rest of the waste is charged to the furnace by means of a mechanical “claw” that deposits wastes and other items (most commonly biomass and/or sewage sludge) at the feed end of a metal grate that moves the waste materials slowly through the combustion chamber. Because of the large size of the

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items deposited on the grate mechanism, the oxidation rates are relatively slow. Because of the low rate of oxidation, a very large combustion chamber and grate are required and the intensity of combustion (rate of heat generation per unit volume) is correspondingly low. There have been improvements over the years in combustion efficiency and pollution control of mass-burn WTE plants, as already mentioned above [6-8, 13, 14-18, 21-27].

Figure 4. Schematic diagram of a typical WTE mass-burn (stoker) facility.

2.2.2. Fluidized-Bed Plants Another extensively used in Japan and can be found in European countries Waste-to-

Energy method is fluidized bed reactors. This method requires shredding (down to 5 cm) and removing of inert materials like glass and metals from the received MSW streams prior to the feed of the fluidized bed reactor. The wastes are fed on top of a fluidized bed of sand or limestone. Combustion under these conditions is more efficient and results in similar temperatures and higher energy recovery. The amounts of non-oxidized materials leaving the combustion chamber are lower and the required excess air is less compare to mass-burn plants. Fluidized-bed combustors operate at temperatures in the range of 830–910oC and can use additional fuel as required and thus they can burn materials with very high moisture content. Because of the lower uniform temperatures, “slagging” and corrosion problems in the furnace are kept to a minimum [6-8, 13, 14-18, 21-27].

2.2.3. A State-o-Art WTE Plant i US

The SEMASS facility at Rochester, Massachusetts is an indicative example of a state-of-art WTE plant. The feed material consists of the entire (wet+dry) MSW stream including Refuse Derive Fuel. The facility serves 50 communities in a 110-km radius. The plant consists of three parallel combustion units and processes over one million tons per year. The first two units were built in 1989 and Unit 3 in 1994 [7, 15, 26, 27].


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Figure 5. Schematic diagram of the SEMASS process at Rochester, Massachusetts, USA.

Waste brought to plant is dumped on a tipping floor (Figure 6). Bulk wastes that could jam the shredders or hazardous wastes are removed prior to shredding. The wastes are shredded in one of two large hammermill shredders that produce a blended material of 15-cm size coarse RDF (figure 7). The shredded material is conveyed under overhead belt magnets for the first round of ferrous metal recovery and is then stored in bays in a closed building [7, 15, 26, 27].

Figure 6. SEMASS Tipping Floor Waste Receiving.

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Figure 7. Shredded wastes and RDF loading.

The shredded MSW fuel is conveyed to bins and from there is ejected through inclined chutes into the three combustion chambers. The feed rate is adjusted by means of automated temperature controls (it is critical for the procedure to keep certain temperature limits-low and high). The bottom of the combustion chamber consists of a moving grate that collects inert materials and heavy combustibles after they are blown into the boiler. These materials settle on the end of the grate away from the feed end and gradually move towards the feed end. An upward airflow through the grate is provided for completing combustion, during the first two thirds of the travel. With the same airflow the ash towards the end of the travel, is partially cooling of. This heat exchange mode allows good heat recovery and eliminates the need for quenching the bottom ash with water [7, 15, 26, 27].

2.3. Emissions MSW incineration plants are often subject of controversy, usually because of their flue-

gas emissions. Due to public health issues central governments adopted very strict emission limits from waste incineration facilities, as it is proven that the burning of wastes is responsible for a significant number and volume of hazardous substances. The adopted emission limits required significant investmens in flue-gas treatment devices like acid-gas scrubbers, electrostatic precipitators or baghouse filters. Figure 8 presents the flue-gas cleaning system of the SEMASS Waste-to-Energy Plant. As it can be seen the gas control system consists of dry scrubbing, activated carbon Injection and fabric filter bag-house Table 3 presents the limits for Waste Incineration Plants in Germany. The amount of dioxins in Germany dropped from 1990 to 2000 to 1/1000. In 1990 one third of all dioxin emissions in Germany came from waste incinerator plants, whereas for the year 2000 the contribution was less than 1% as shown in Table 4 [4, 7-8, 13, 15-18, 23-27].


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Table 3. Emission limits for waste incineration in Germany

Parameter Unit Emission limit Dust mg/Nm3 10 TOC mg/Nm3 10 HCl mg/Nm3 10 HF mg/Nm3 1 SO2 mg/Nm3 50 NOx mg/Nm3 200 CO mg/Nm3 50 Cd+Tl mg/Nm3 0.05 Hg mg/Nm3 0.03 Metals mg/Nm3 0.05 Dioxins/furans ng TE/Nm3 0.1

Figure 8. Air Cleaning System of SEMASS WTE facility (Energy Answers Co.)

Table 4. PCDD/F emission sources in Germany (www.umweltbundesamt.de)

sources Emission per year in g TE 1990 1994 2000

metal industry 740 220 40 sintering plants 575 168 < 20 iron and steel production 35 10 < 5 waste incineration 400 32 < 0,5 municipal solid waste 399 30 < 0,4 hazardous waste 2 0,04 medical waste 0,1 0,0002 sewage sludge < 0,1 0,03 power plants 5 3 < 3 industrial combustion facilities 20 15 < 10 domestic stoves 20 15 < 10 traffic 10 4 <1 crematoria 4 2 < 2

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Depending on the waste composition MSW consists of a biogenic or renewable part from 57 % to 73 % by weight. The main biogenic fractions are yard and kitchen waste, paper, cardboard and wood. Considering the fossil carbon content and the respective heating values, the emission factors for MSW and selected fossil fuels are given in Table 5. It is obvious that the emission factors (related to the energy content) of the waste types are clearly below those of the fossil fuels but this does not mean that the waste incineration with energy recovery always obtains a CO2 reduction. The reduction potential by WTE plants depends on the fuel and the efficiency of the energy production compared to the alternative use as, for example, RDF in power plants [4, 7-8, 13, 15-20, 23-27].

Table 5. Waste–to–Energy and Fossil Fuel Power Plants – Comparison of Air Emissions

(O’Brien, 2006)

Fuel Air Emissions (kg/MWh) Carbon Dioxide (CO2) Sulphur Dioxide (SO2) Nitrogen Oxides

MSW (fossil-C) 379.66 0.36 2.45 Coal 1020.13 5.90 2.72 Oil 758.41 5.44 1.81 Natural Gas 514.83 0.04 0.77

3. RDF AND SRF PRODUCTION AND UTILISATION

3.1. RDF and SRF Definitions Refuse derived fuels cover a wide range of waste materials which have been processed to

fulfil guideline, regulatory or industry specifications mainly to achieve a high calorific value. Waste derived fuels include residues from municipal solid waste (MSW) recycling, industrial/trade waste, sewage sludge, industrial hazardous waste, biomass waste, etc [8-11].

Refuse is a general term for municipal solid and commercial wastes and the terms ‘Refuse Derived Fuel (RDF)’ and ‘Solid Refuse Fuel (SRF)’ usually refer to the segregated high calorific fraction of MSW, commercial or industrial process wastes. RDF and SRF are produced during Mechanical Biological Treatment (MBT) of wastes. Other terms are also used for MSW derived fuels such as Recovered Fuel (REF), Packaging Derived Fuels (PDF), Paper and Plastic Fraction (PPF) and Process Engineered Fuel (PEF). REF, PDF, PPF and PEF usually refer to a source-separated, processed, dry combustible MSW fraction (e.g. plastics and/or paper) which are too contaminated to be recycled. It has a higher calorific value, lower moisture content and lower ash content (on combustion) than RDF derived from mixed waste fractions. Table 6 presents typical properties of RDF, and Table 7 shows theoretical characteristics of RDF. The calculations are based on screening (screen only) as well as screening and separation of heavy materials (screen+heavy). Screening sizes are 40 mm (medium) and 100 mm (coarse). [8-11, 18, 28-33].


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Table 6. Typical ranges of RDF properties

Chemical Properties Mechanical Properties Calorific Value 11-18 MJ/kg Particle size 10-300 mm moisture 10-30 % wt Bulk density 120-300 kg/m3

ash 10-20 % wt Cl 1,0-1,8 % wt S 0,3-0,8 % wt

Table 7. Theoretical calculation of levels of harmful substances in RDF

(All values for dry matter)

Theor. RDF (medium) (screen only)

Theor. RDF (coarse) (screen only)

Theor. RDF (medium) screen+heavy

Theor. RDF (coarse) screen+heavy

Cl overall in % 0.89 1.89 0.77 0.59 S overall in % 0.26 0.33 0.3 0.28 Pb in mg/kg 1600 3770 130 170 Cd in mg/kg 3.3 7.5 1.8 1.0 Cr in mg/kg 290 340 66 86 Hg in mg/kg 2.55 3.87 0.23 0.14

The terms ‘Secondary Fuel, Substitute Fuel and Substitute Liquid Fuel (SLF)’ are used

for processed industrial wastes which may be homogeneous or mixed to specification. Examples of these fuels include waste tyres, waste oils, spent solvents, bone meal, animal fats, sewage sludge and industrial sludge (e.g. paint sludge and paper sludge). These terms can also refer to non-hazardous packaging or other residues from industrial/trade sources (e.g. plastic, paper and textiles), biomass (e.g. waste wood and sawdust), demolition waste or shredded combustible residues from scrap cars [8-11, 18, 31, 32].

3.2. RDF and SRF Production RDF and SRF produced from MSW through a number of different processes consisting

in general of: [8-11, 31, 32]

Sorting or mechanical separation Size reduction (shredding, chipping and milling) Separation and screening Blending Drying and pelletising Packaging and Storage.

Typically, the waste material is processed to remove the recyclable fraction (e.g. metals),

the inert fractions (such as glass) and separate if it is possible the fine wet organic fraction (e.g. food and garden waste) containing high moisture and high ash material before being pulverised. This procedure was described extensively by Keldenich and Marzi. The wet organic materials can then undergo further treatment such as composting or anaerobic

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digestion, and can be used as a soil conditioner for landfill restoration work or be landfilled. In some cases, the putrescible fraction is kept in place to enable the mass of material to be dried through biological treatment (the process of ‘dry stabilisation’) [8-11, 31].

The coarse fraction is either rejected or returned to the pulveriser. The medium fraction, consisting of paper, card, wood, plastic and textiles can either be burnt directly as coarse fuel or dried and pelletised into dense RDF. The decision as to whether or not to pelletise is usually based upon the location of the RDF manufacturing facility relative to the combustion facility [8-11, 18, 30-33].

There are two technologies which have been developed and which produced from MSW a high calorific fraction which can be used as RDF

Mechanical Biological Treatment plant and Biological Drying Process.

In a mechanical biological treatment plant (MBT), metals and inerts are separated out and

organic fractions are screened out for further stabilisation using composting processes, either with or without a digestion phase. It also produces a residual fraction which has a high-calorific value as it is composed mainly of dry residues of paper, plastics and textiles. Tables 8 and 9 present the RDF production and composition from MSW in selected EU Member States, respectively [1, 6, 8-11, 16, 18, 30, 31, 34].

RDF and SRF can also be produced through a ‘biological drying’ process, in which residual waste are effectively dried (and stabilised) through a composting process, leaving the residual mass with higher calorific value and suitable for combustion. The inerts and metals are removed through mechanical process before or after the bio-drying depending of the technology applied for bio-drying [6, 8-11, 16, 18, 30-34].

Table 8. RDF production from MSW in selected EU Member States, 2001 (source : [8-

11].

Country Type and Numberof plant

Waste input Fuel output Capacity (x103Mg/y)

Quantity processed (x103 Mg/y)

Quantity produced (x103 Mg/y)

Austria 10 MBT+ (2) 340+ (60) 340 ¹ 70 Finland 12 + (8) 200-300 140-300f) 40-90* Germany 14 1100 330* Italy 16MBT +6 + (3) 1500 1000 300* Netherlands 13 + (12) 2000 (+1300) 2000 700 UK 3MBT 250 250 90 Total EU >50 > 5500 >3700 ≈ 3000 Notes: Plants producing RDF planned or under construction are given into brackets * Assuming a RDF production rate of 30% ¹ Including MSW, sewage sludge, waste wood and commercial waste


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Table 9. RDF composition (typical) from different EU regions, (source : [8-11, 31])

Waste Fraction Greece UK Italy Flemish Region MBTC Plant (%) (%) (%) Sorting Process

(%) MBT (%)

Printed material 37,0 84,0 44,0 13,0 64,0a) Remaining Papers 6,60

Printed packing 18,10 Plastic packing 22,90 11,0 23,0 31,0 9,0 Remaining plastic 1,70 Textile 10,80

5,0c) 12,0 14,0

27,0b) Wood 0,40 4,5 12,0 Organic -others 1,30 16,5 30,0 a) Includes paper, textile, wood b) Includes rubber, synthetic material c) Includes glass, wood, textiles and metals

2000 : 1.4 MT produced

Austria 7,00%

Belgium 6,00%Finland 12,00%

Netherlands 18,00%

UK 4,00%Sweden 4,00%

Germany 36,00%

Italy 13,00%

2005 : 12.4 MT produced

France 8.00%Greece 4.00%

Ireland 4.00%Spain 8.00%

UK 2.00% Netherlands 12.00%

Portugal 4.00%

Italy 13.00%

Germany 30.00%

Finland 3.00%

Austria 4.00%

Belgium 2.00%

Sweden 4.00%

Compound annual growth rate = 54%

Sources : CEN/FEAD estimates

Figure 9. Projected growth in RDF and SRF production volumes, selected EU countries, 2000 – 2005 (source [8]-[10], [23]).

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Common to most RDF and SRF production concepts is a certain degree of size reduction and removal of organic and inert material. As a result, RDF has, on average, higher heating value, lower ash content, and a lower bulk density compared to untreated waste. Note that the majority of pollutants such as chlorine, sulphur and heavy metals are not affected by the pre-treatment, even though the metals removal systems minimize the present of metal in the produced fuel. Wide variations in the properties and composition of RDF and SRF – even when it is produced by one particular system – have been observed and the term seems to cover at least as wide a variety of fuels as the term ‘biomass’ [6, 8-11, 18, 31].

The production of RDF and SRF, from household and business waste has grown from 2000 to 2005 from 1.4 million to 12.4 million tons/year as shown in Figure 9. Up to the year 2007 the total amount of RDF produced in Europe can be estimated to 15x106 t/y, approximately, of which Germany alone produced approx. 7 million. The incineration of this amount of RDF is not easy. In Germany roughly one million tons of RDF is kept on stock without the chance to be burned in the next few years. The lack of capacity for the incineration of RDF has a number of reasons with fuel quality being the most important. [6, 8-11, 31]

3.3. RDF and SRF Utilisation The RDF is a fuel with very diverse qualities therefore needs to be handled in different

ways. Table 4 compares SRF from MBT process of MSW with typical fossil fuels. The production of steam and/or electricity can be done in power plants or specially designed fluidized bed reactors. Also, RDF can be used to produce cement, asphalt or bricks. Every application demands a different quality in the RDF production. Chlorine and heavy metals are limiting factors, but already these fuels are in use for energy production in many sectors, including power generation and cement industry, in EU (Table 5) and around the world [1, 8-11, 18, 21, 30-33].

Table 10. Comparison of CO2 emissions from the use of fossil fuels and Secondary

Derived Fuel produced by processed MSW (MBT process).

Fuel Type Calorific Value MJ/kg

Total CO2emission g CO2/kg

Renewable energycontent % renewable

CO2 emissionloading Mg CO2 / TJ

Lignite 8.6 955 0% 111 Pit Coal 29.7 2762 0% 93 Heating Oil 35.4 2620 0% 74 Natural Gas 31.7 1775 0% 56 MSW 8-9 1170 50.0% 45

SRF from MBT 14-18, 15 aver. 1067 66.8% 24

Table 11 compares several refuse-derived fuels with the characteristics of primary energy

fuels and the demands of the cement industry. A comparison between Table 7 and Table 11 highlights the fact that a further reduction in the level of harmful substances is feasible. Practical tests have confirmed these theoretical calculations.


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Table 11. Characteristics of primary and secondary fuels

(All values for dry matter

Brown coal literature

Brown coal VEAG

RDF in the cement industry

RDF Velsen RDF Herne

Dry stabilized residues

(Bünsow and Dobberstein, 1985)

(Heering et al., 1999)

Calorific value kJ/kg 8,000-20,000 8,496-8,854 13,000 14,560 –14,820 13,130 16,000 Chlorine overall in % < 0.06 0.01-0.02 <1.5 0.76-0.97 0.56 0.44 S overall in % 0.3-5 0.56-0.7 <0.4 0.15-0.19 0.14 0.45 Pb in mg/kg 7.9-34.1 1.3-7.1 <150 212.4-401.8 138.1 230 Cd in mg/kg 0.1-0.23 0.2-4.5 <10 5.32-6.12 4.45 2.2 Cr in mg/kg 28.1-91.1 6.12-13.5 <150 90.5-127.8 67.1 60 Hg in mg/kg 0.07-0.19 0.1-0.54 <1.5 0.84-1.08 1.25 0.75

Table 12. Utilisation of RDF from MSW in selected EU Member States, 2001 (source :

[8-11]).

Country Number Quantity/ Capacity (x103Mg/y) Dedicated plant Italy (2) C Sweden 1400 United Kingdom 1 30 Power plant Italy (3) T (1200) United Kingdom 1 50 Paper mill Finland 200 District heating plant Finland 50 50 Cement kiln Belgium 1 15 Italy 5 300 Denmark 1 2.6 Notes: Figures into brackets are referring to quantities for which information was incomplete or

uncertain Τ : in trial, C : In construction

According to several studies carried out around the world, the following options for the

utilisation and conversion of RDF and SRF from MSW to energy have been already used or could be used in the future: [1, 6-11, 18, 21, 26-38]

on-site in an integrated thermal conversion device, which could include grate or

fluidised bed combustion, gasification or pyrolysis off-site at a remote facility employing grate or fluidised bed combustion, gasification

or pyrolysis co-combustion in coal fired boilers co-incineration in cement kilns co-gasification with coal or biomass.

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The total quantities of RDF from processed MSW used in Europe in dedicated waste to energy installations, in power generating plants, district heating plants and industrial processes such as paper mills and cement kilns has been estimated to amount to more than 2 million tonnes per year in 2001. It was reported that it is not always possible to secure an outlet for RDF and in Germany for example, quantities have to be stored. The quantities of RDF burnt are expected to increase in the future with planned increased capacity for RDF utilisation mainly in Belgium, Italy and in the UK. There are also plans for using RDF from MSW in other processes such as gasification and pyrolysis [8, 11, 18, 21, 26-38].

Power plants, based on hard coal or lignite, use their fuel in powdered form, briquettes or in form of small milled grain. The types of furnace are optimized in respect of the used type of coal or lignite. These circumstances determine the quality of RDF used in different kind of power plant. In Table 13 the specifications of RDF of different power plants in Germany are listed. The power plants have the biggest potential for co-incineration of RDF if one calculates a substitution of 5 to 10 % for coal and lignite. But in reality, most power plants did not burn the authorized amount of secondary fuel from MBT and sorting plants due to mainly the technical risks, low quality of RDF/SRF, etc. New developments are the gasification of RDF combined with a power plant or cement kiln. The main problem with this combined plant is the availability of the gasification units [8-11, 28, 30, 32, 33].

Germany is a representative example supporting the above. Currently, a total of 6.1 million tonnes per year of high calorific waste (i.e. calorific value > 11 MJ/kg) is available in Germany. Part of this is produced by MBT facilities, part of it concerns commercial waste. Nearly 2.1 million tonnes per year, mainly the fraction with a heating value in excess of 18 MJ/kg, is used for co-combustion coal fired power plants. But in reality, most power plants did not burn the authorized amount of secondary fuel from MBT and sorting plants, as only 38% of the authorized capacity was used. In addition, 2.8 million tonnes per year, with a heating value typically between 11 and 15 MJ/kg, are treated in Waste-to-Energy (WtE) plants. The remaining, amounting to 1.3 million tonnes per year, is put in temporary storage or exported. Long term prognoses of the market volume show an increase until 2010, followed by a small and gradual decline towards 2020 [8-11, 28, 30, 32, 33].

Table 13. RDF specification of different power plants in Germany (Eckardt, 2005)

Parameter Hard coal Lignite water content 10-20 % 20-25 % ash content 10-25 % 5-40 % Sulphur 0.5-1.0 % 0.4 -2.0 % Chlorine 0.4-1.0 % 0.4-1.0 % Fluorine 0.05-0.2 % 0.05-0.2 % Cadmium 0.1-10 mg/kg Mercury 1.0 mg/kg Chromium 150 mg/kg

The RDF/SRF from MSW utilisation in cement kilns is rather small mainly due to the

following reasons : 1. Quality specifications are not met (chlorine content too high, heating value too low,

metal content too high).


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2. The additional investment for storage, handling and chlorine by-pass is too high. 3. The RDF ashes do not match the recipe for high quality cement Germany which is among the major producers and consumers of RDF/SRF from MSW

utilizes in cement kilns less than 10 % of RDF from MBT and sorting plants is used as energy substitute. Germany have the permit to burn 2,673 million tons/y of secondary fuel, 22 % of the energy demand of the cement producing industry is covered by secondary fuel, with commonly used wastes including waste tyres, waste oil, waste wood, plastic and textile wastes.

Here, it must be stressed that co-incineration of waste in plants that were not designed to incinerate waste should not be allowed to cause higher emissions of polluting substances in the stack gas of such operations than those permitted for dedicated incineration plants and, therefore, should be equipped with adequate Air Pollution Control (APC) systems [3, 4, 8-11, 14, 18, 20, 22, 24, 25].

Because of the difficulties of acceptance of RDF in power plants and in cement kilns, a number of specially designed plants for RDF have been built around EU, using fluidized bed reactors and grate firing plants. Most of these incineration plants are connected with industrial plants with a high demand of steam and electricity on a 24h-basis (e.g. paper mills), in order to optimize the energy utilisation. In Germany for example 530,000 tons/y RDF are currently burnt in fluidized bed reactors (60%) and grate firing plants (40%) [8-11, 18, 21, 30, 32].

As proven technologies both grate and fluidized bed are able to incinerate RDF/SRF from MSW. The water-cooled grate is the right choice for this material; whereas both the Circulating fluidized bed (CFB) as well as the stationery bed is used for RDF. The main restriction of fuel from waste to be incinerated in the fluidized bed is the particle size. To ensure that the incineration process is working without problems, the particle size should not exceed 100 mm and no metal or heavy material like stone, glass etc. should be present in the fuel. On the other hand in the grate technology, particle size can be bigger and the restriction on the feed material is normally less strict. The fluidized bed has a higher efficiency and fewer problems with NOx and volatile heavy metal, but often more problems with erosions. Both plant types have problems with high temperature corrosion depending on the amount of chlorine in the RDF. The classic solutions are cladding of the boiler tubes, flue gas recirculation and/or reduction of steam parameters [8-11, 18, 21, 30, 32, 33].

4. THE CASE STUDY OF GREECE

4.1. MSW Production and Management in Greece MSW production in Greece is increasing over the years, as everywhere in the world.

Figures 10 and 11 present this growth as well as the mean composition of MSW respectively, as it has been reported by the Greek Ministry of Environment, Planning and Public Works. A constant increase over the past years is observed and is estimated to continue in the foreseeable future. A large fraction of the MSW tonnage is generated in the Regions of Attica (39%) and Central Macedonia (16%), where the largest cities, Athens and Thessaloniki are situated. The composition of MSW in Greece is similar to the European average with the only

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differences being a higher organic fraction and moisture content up to 40%. The MSW management methodologies in Greece, as they were applied in 2004, were landfilling (91.8%) and recycling (8.2%). At present, there is no WTE capacity in Greece, while some mechanical treatment units, producing RDF or SRF, are operating or are under construction [1, 7, 39-44].

0

0,5

1

1,5

2

2,5

3

3,5

4

4,5

5

kg/d & res 0,83 0,97 1,03 1,06 1,09 1,14Mtons/year 3,2 3,95 4,08 4,26 4,45 4,56

1991 1997 1998 1999 2000 2001

Figure 10. Annual production of MSW in Greece; Source: Ministry of Environment, National Plan for Solid Waste Treatment 2003

Other 9,00%

Lether - Wood - Rubber 2,00%Metal 3,00%

Glass 3,00%

Plastic 14,00%

Paper/Cardboard 29,00%

Organic 40,00%

Figure 11. Mean composition of MSW in Greece; Source: Ministry of Environment, National Plan for Solid Waste Treatment 2003


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Table 14. Input and output streams as per initial design of plant and average composition of RDF produced at Ano Liossia MBTC Plant in 2006-2008(source [12-15]).

Input Stream Output Stream RDF Mean Composition Materials Quantity (t/day) Materials Quantity (t/day) Materials Quantity (%) MSW 1200* Compost 300 Printed Paper 37.80 Sewage sludge 300 RDF 360 Other Papers 4.90 Green wastes 130 Fe 35 Paper packing 16.50 Al 5 Plastic packing 26.20 Wastes 330 Other plastics 1.30 Water 500 Textiles 11.00 Volatiles 100 Wood 0.40 Organic 0.80 *at present, the MSW feed to this plant is reported to be 700 tons/day.

Table 15. Potential for processing MSW to SRF/RDF in Greece, as per the MSW

Management Strategic Plan of Greece [11-13,15].

Regions / Prefectures Plants Waste Quantities (x103 t/y)

SRF Quantities (x103 t/y)

Attica MBTC I 495 148.5* MBTC II 660 198.0*

Central Macedonia

NW Thessaloniki MBT 180¹ 180² 360³ 54† SA Thessaloniki MBT 120¹ 180² 240³ 36† Serres MBT 90¹ 90² 100³ 27† Imathia MBT 50¹ 55² 60³ 15† Pellas 30² 35³ 9‡ Pierias 30² 35³ 9‡ Kilkis 35³ 10.5

Western Macedonia MBT 150# 106# 19.5 Peloponnese 255 76.5

Crete Chania MBT 70 + Iraklio ¦ BioDry 70 210 35

Notes : The quantities have been calculated with factor 0.3 based on existing MBTC Plant operating in Ano Liossia, with the exceptions noted below or on the Table.

* : The quantities have been calculated considering that 120x103 t/y in MBTC I and 160x103 t/y in MBTC II of sewage sludge will be treated also.

¹,²,³ : planned quantities for the years 2010, 2013, 2020 respectively †, ‡ : The quantities have been calculated for the years 2010, 2013 respectively # : 150x103 t/y is the scheduled capacity, 106x103 t/y is the foreseen processed quantity for 2011 and the

SRF production rate is around 18%. ¦ : In Iraklio Prefecture of Crete a Bio-drying Plant producing SRF with approximately 50% SRF in the

output stream is under construction with capacity 70x103 t/y, which is planned to be increased in 210x103 t/y in 2010. As of November 2006, the MSW Mechanical Biological Treatment and Composting

(MBTC) Plant at Ano Liosia (Attica) has produced 220000t per annum of RDF of 27.4% moisture, and Cl content of 0.4%. Table 14 presents the main composition of the produced RDF and shows the input and output streams as were planned for the MBTC Plan in Ano Liossia. The production of this fuel justified the investment of the MBTC facility and was

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projected to be financially advantageous to the conventional approach of mass-burning of solid wastes. Nevertheless this fuel has not as yet been used in cement production or power generation, even though the utilisation potential is quite high [6-11, 15-16, 31-33].

The National Plan for Waste Management for 2007-13 (Ministry of Environment, Planning and Public Works), foresees a number of Plants for RDF/SRF production in several areas of Greece, but does not mention the need for RDF-dedicated WTE facilities, because it is assumed that this material would be co-combusted in existing industrial plants. However, if this route does not materialize, as it did not for the MBTC of Ano Liossia, it would be necessary to build combustion plants fuelled by RDF [39-41].

According to the National Plan for Waste Management as was published by the Greek Ministry of Environment, Physical Planning and Public Works for 2007-2013 a number of Plants for RDF and SRF production is foreseeing, in several areas of Greece. Table 15 gives the Regions/Prefectures where the RDF/SRF production plans are foreseeing, and their annual capacity. It must be noted that MSW Processing Plants have also been included in the National Plan for MSW for the Regions of Western Greece, Central Greece, Thessaly, Epirus, East Macedonia and Thrace; however, the number and capacities of such plants have not been defined to this date. As it can be seen, the potential production of RDF/SRF is quite high, especially in the cases of Attica and Central Macedonia Regions where the expected annual quantities are 345000t and 132000t respectively [39-41].

4.2. Electricity Generation Potential from Waste Combustion in Greece The direct combustion of “as-received” MSW (mass burn) is widely used through the

developed world and it is less costly to implement than the combination of an RDF generating facility (e.g., like the MBTC facility at Ano Liossia) followed by an RDF-dedicated power plants However, the RDF option offers advantages in cases where the RDF can be co-combusted with lignite in existing industrial plants equipped with Air Pollution Control systems that can meet the EU standards for volatile metals, dioxins, and particulate matter. Another possibility is the implementation of distributed small RDF/SRF plants that reduce the weight of MSW processed and produce a higher calorific value fuel that can then be transported easier to a regional WTE facility. The advantage of such a configuration would be that a few WTE facilities, strategically located across Greece, may be less costly to implement than many small WTE plants [3, 4, 7-11, 18, 19, 21, 22, 28, 36-41].

In the case of co-combustion (direct method, where RDF/SRF is blended with coal or other fuel and supplies the burner directly) and co-gasification (indirect method where RDF is gasified in a separate chamber and then the produced gas mixture is injected in the combustion chamber (European Commission, 2003) of SRF with lignite, significant research has been conducted already. Figure 12 illustrates the location of lignite power plants in Greece, as they should be considered as potential future recipients of RDF/SRF. Some of these studies have indicated that the SRF quantities to-be-produced in Western Macedonia can be utilised by the Kardia Power Plants, by substituting 2-3% of lignite in one of the three 300MW units. The same scenario has been proposed for the SRF production in Peloponnese, by using the Megalopolis III Thermal Power Station where a new desulphurisation unit, under construction, is projected to reduce current emissions substantially [28, 32, 36-38, 42].


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Figure 12. Location of coal- fired power plants in Greece.

Nevertheless the possibility for toxic emissions from co-combustion exists due to the wastes composition and the fact that these plants were not designed to incinerate waste or RDF/SRF. Thus these plants should not be allowed to cause higher emissions of polluting substances in the stack gas of such operations than those permitted for dedicated incineration plants. Presumably, most of the objects that contain volatile metals will be removed during the RDF preparation process. An analysis of the RDF produced at Ano Liosia has shown that it contains very low concentrations of these metals [35]. However, the typical MSW contains 0.5% chorine, half of which derives from organic wastes and salt, and half from chlorinated wastes. Recent works showed that the RDF produced from MSW in Greece will contain almost the same concentration of chlorine [35]. Even very small concentrations of chlorine lead to the in-situ formation, during cooling of the combustion gases, of the toxic compounds that are called dioxins and furans. All modern WTE plants are equipped with activated carbon injection (ACI) so that any volatile metals or dioxin/furans molecules in the process gas are attached to the carbon particles and are then removed from the gas stream in the subsequent fabric filter baghouse. The final concentration of dioxins/furans in the stack gas must be, according to EU and US regulations be less than 0.1 Toxic Equivalent nanograms per standard cubic meter. The EU and US WTEs plants emit less than 0.03 TEQ ng/Nm3. Therefore, lignite power plants that will co-combust RDF must be equipped with adequate Air Pollution Control (APC) system [3, 4, 7, 8, 13-16, 26, 27, 30, 42-43].

4.2.1 Scenario 1: RDF/SRF Utilisation for Electricity Production

Based on the above studies, it may be feasible to utilise the SRF produced by the Western Macedonia and Peloponnese facilities in the nearby thermoelectric power plants. On the basis of this scenario and the results of studies that indicate that 1 kg of SRF can substitute 1kg of lignite and, also, reduce fossil carbon emissions by 1kg CO2 per kg of SRF, co-combustion of SRF in lignite power plants may reduce use of lignite by 20000t per year in Western

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Macedonia and reduce carbon dioxide emissions by the same amount; also, there would be a saving of 76000t of lignite per year and 76000t of CO2 emissions avoided in Peloponnese [35-38, 42-44].

Table 16. Potential for electricity production and lignite savings in Greece by RDF/SRF

utilisation.

Region Electricity Production / Lignite Savings Remarks

Attica 221x106 kWhe/y 1 dedicated RDF/SRF utilization plant of at least 345Kt/y capacity

Central Macedonia 85.8x106 kWhe/y 1 dedicated RDF/SRF utilization plant of at least 132Kt/y capacity

Crete 70x106 kWhe/y 1 dedicated RDF/SRF utilization plant of at least 105Kt/y capacity

Western Macedonia 20x103t/y Co-combustion / co-gasification on existing coaled fired power plants

Peloponnese 76x103t/y Co-combustion / co-gasification on existing coaled fired power plants

Epirus*† 32x103t/y MBT Plants in Epirus and co-combustion/co-gasification on existing coaled fired power plants in Western Macedonia

Western Greece* 60x103t/y Co-combustion / co-gasification on existing coaled fired power plants

Central Greece* 65x106 kWhe/y 1 dedicated RDF/SRF utilization plant of at least 100Kt/y capacity Thessaly*

Eastern Macedonia –Thrace* 60x103t/y Co-combustion / co-gasification on existing coaled

fired power plants * : The quantities have been calculated based on existing data of 1997, increased from 1997 by 20%,

with a recycling rate of 25% (150% increased from the present one, following the target values of the Ministry).

† : The quantities have been calculated with factor 0.3 based on existing MBTC Plant operating in Ano Liosa For the case of Crete a dedicated utilisation plant is foreseen in the National Plan for

Solid Waste Treatment. The quantities foreseen after 2010 are in the average of the dedicated plants as they are 105x103 t/y. Based on the international experience, such a plant could provide at least 70GWhe, assuming that 1t SRF provides to the grid 650kWhe, in the island of Crete covering a significant part of electricity needs [2, 6, 35-38, 42-44].

The cases of Attica and Central Macedonia are complicated due to the public acceptance. The quantities are quite high and thus based on international experience the best method for utilisation is the dedicated plants in each region. Following the same assumption as above, that 1t SRF provides to the grid 650kWhe, the production of electricity would be at least 221GWhe and 85.8GWhe, for Attica and Central Macedonia respectively. Based on the fact that because of the small distance that these power plants will have from the consumers (Athens and Thessaloniki) the benefit is even higher due to lower network losses from the construction of these plants. In addition a significant volume of wastes will be treated in a way that reduces their volume, reducing the landfilling requirements for waste management.


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The benefit is quite high both in electricity supply and to the environment, in these regions [34]-[40].

These plants based on the fact that 1 kg CO2 emissions/kg SRF can be prevented, can reduce the GHG emissions of the Power Generation Sector by a significant number of MtCO2 and reduce the dependency from imported fossil fuels, supporting the efforts for economic growth of Greece. The potential benefits are huge: Over 0.5 billion kWhe/y, almost 1% of the total electricity production of Greece in 2006 will be generated, and over 248000 t of lignite will be saved annually [6-9, 35-44].

4.3.2. Scenario 2: Mass-Burn and RDF/SRF Utilisation for Electricity Production

Based on the above studies, it may be feasible to utilise the SRF produced by the Western Macedonia and Peloponnese facilities in the nearby thermoelectric power plants. On the basis of this scenario and the results of studies that indicate that 1 kg of SRF can substitute 1kg of lignite and, also, reduce fossil carbon emissions by 1kg CO2 per kg of SRF, co-combustion of SRF in lignite power plants may reduce use of lignite by 20000t per year in Western Macedonia and reduce carbon dioxide emissions by the same amount; also, there would be a saving of 76000t of lignite per year and 76000t of CO2 emissions avoided in Peloponnese [35-38, 42-44].

For the case of Crete, a dedicated RDF-combustion plant is foreseen in the National Plan for MSW Treatment that would combust 105000t per year of RDF. Based on the international experience (about 650kWh/t RDF), such a plant would generate about 70GWh of electricity annually [35-38, 42-44].

The cases of Attica and Central Macedonia are more complicated due to public acceptance. The quantities of produced MSW are very high and thus, based on international experience, the best method for energy recovery seems to be mass-burn WTE combined with RDF/SRF streams produced at communities far away from the WTE facility. Following the same assumption as above, that 1 tonne of SRF combusted can generate about 700kWhe for the grid, and one tonne of MSW as-received 650kWhe, Table 17 shows the proposed scenarios for electricity production for all mainland regions in Greece, including those for which there are no data presented in the National Strategic Plan. Due to the fact that the major WTE power plants will be close to the consumers (Athens and Thessaloniki), the benefit is even higher due to lower electricity network losses. Combustion with energy recovery will also result in a 90% reduction in the volume of wastes to be landfilled, in case that beneficial uses of WTE ash are not developed. The resulting benefit will be quite high, both in terms of electricity supply and environmental quality in regions that are facing major problems in managing their wastes [6-9, 15, 16, 25, 26, 36-38, 42-44].

Implementation of the above scenario will reduce the GHG emissions of the Power Generation Sector in Greece and reduce the nation’s dependence on imported fossil fuels, thus supporting the efforts for economic growth of Greece. These additional benefits to the ones already mentioned prove that the use of MSW and RDF/SRF for energy production will provide significant benefits not only to the environment but also to the economy and Power Generation Sector in Greece. The potential benefits are huge: Over 1.5 billion kWhe/y, almost 2.5% of the total electricity production of Greece in 2006, will be generated, and over 128000 t of lignite will be saved annually [6-9, 15, 16, 25, 26, 36-38, 42-44].

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Table 17. Potential for electricity production and lignite savings in Greece by WtE (mass-burn and RDF/SRF utilisation).

Region Electricity Production /

Lignite Savings Remarks

Attica 650x106 kWhe/y WtE facilities of at least 1Mt/y capacity for mixed streams of MSW and RDF/SRF

Central Macedonia 325x106 kWhe/y WtE facility with 0.5Mt/y capacity for mixed streams

of MSW and RDF/SRF

Crete 70x106 kWhe/y 1 dedicated RDF/SRF utilization plant of at least 105Kt/y capacity

Western Macedonia 20x103t/y Co-combustion / co-gasification on existing coaled

fired power plants

Peloponnese 76x103t/y Co-combustion / co-gasification on existing coaled fired power plants

Epirus*† 32x103t/y MBT Plants in Epirus and co-combustion/co-gasification on existing coaled fired power plants in Western Macedonia or W. Greece

Western Greece* 130x106 kWhe/y 1 WtE facility with 0,2Mt/y capacity for mixed streams of MSW and RDF/SRF produced locally

Central Greece* 195x106 kWhe/y

1 WtE facility with 0,3Mt/y capacity for mixed streams of MSW and RDF/SRF produced locally in the Regions Thessaly*

Eastern Macedonia – Thrace*

130x106 kWhe/y 1 WtE facility with 0,2Mt/y capacity for mixed streams of MSW and RDF/SRF produced locally

* : The quantities have been calculated based on existing data of 1997, increased from 1997 by 20%, with a recycling rate of 25% (150% increased from the present one, following the target values of the Ministry).

† : The quantities have been calculated with factor 0.3 based on existing MBTC Plant operating in Ano Liosa

5. CONCLUSION The use of MSW, in mass burning WTE facilities, or in the form of SRF/RDF in

dedicated combustion facilities or as fossil-fuel substitute in lignite-fired power results in significant energy-security and environmental benefits. Countries that have included energy recovery (either as heat or as electricity) from MSW have reduced their dependency on fossil fuels and at the same time are complied with the EU Directives in waste management. Southern EU countries mainly are focused on electricity generation for MSW incineration, fact that supports the role of WTE facilities in electricity generation sector. The case study presented in this chapter, concerns an EU country without any WTE facility in operation, and where still the WTE role in electricity generation and management of MSW haven’t been proved yet, beyond any doubted both for the public and the stakeholders. The current conditions, the volume and energy content of MSW generated, and the National Plan for Solid Waste Treatment in Greece indicate that the potential for electricity production from MSW is quite high even though the calculations were based on rather low efficiency factors in electricity generaton. The results of past studies show that there it may be possible to use


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SRF in existing power plants of Macedonia and Peloponnese, while Athens, Thessaloniki, Thessaly and Western Greece require mass burn WtE facilities in combination with SRF/RDF facilities. In Crete, an RDF/SRF utilisation in dedicated power plant is foreseen. Significant environmental benefits would be derived, including reduced need for fossil fuels, decreasing dependence on import fuels, reducing the Greenhouse Gas emissions of the Power Generation Sector, and avoidance of landfilling. Therefore, it is imperative that Greece should take into full consideration the ramifications of using MSW as a fuel, either in mass burn WTE facilities or in the form of RDF combusted in dedicated facilities or co-combusted in lignite thermoelectric power plants equipped with adequate Air Pollution Control (APC) systems.

REFERENCES

[1] European Environmental Agency (EEA) : Europe’s Environment, The Fourth Assessment, Copenhagen 2007.

[2] EU Directive 1999/31/EC of 26 April 1999 on the landfill of waste. [3] EU Directive 2000/76/EC of 4 December 2000 on the incineration of waste. [4] EU Directive 2001/80/EC of 23 October 2001 on the limitations of emissions of certain

pollutants into the air from large combustion plants. [5] EU Directive 2001/77/EC of 27 September 2001 on the promotion of electricity

produced from renewable energy sources in the internal electricity market. [6] http://www.assure.org, accessed May 2006 [7] www.seas.columbia.edu/earth (accessed January 3-4, 2007) [8] Karagiannidis, A.; Bilitewski, B.; Tchobanoglous, G.; Themelis, N.J.; Wittmaier, M.;

Tsatsarelis, Th. In Waste Management Research Trends; Golus T.V.; Nova Science Publishers; N.York, NY, 2008; pp 105-163.

[9] Archer, E., Baddeley, A., Klein, A., Schwager J. & Whiting, K. Mechanical-Biological-Treatment: A Guide for Decision Makers Processes, Policies and Markets. (Juniper Consultancy Services Ltd., 2005)

[10] European Commission – Directorate General Environment: “Refuse Derived Fuel, Current Practice and Perspectives (B4-3040/2000/306517/Mar/E3), Final Report”, July 2003.

[11] Glorius, T., Van Tubergen, J., & Waeyenbergh E. (2005). Classification of Solid Recovered Fuels. www.erfo.info

[12] European Commission, Integrated Pollution Prevention and Control, Reference Document on “Best Available Techniques for the Waste Treatments Industries”, August 2006.

[13] European Commission, Integrated Pollution Prevention and Control, Reference Document on “Best Available Techniques for the Waste Incineration”, August 2006

[14] Confederation on European Waste to Energy Plants (CEWEP). (2006). Statement on the Waste Framework Directive. http://www.cewep.com

[15] http://www.wtert.gr, (accessed March, 2008) [16] www.cewep.com, accessed May 2008 [17] Reimann, D.: ‘CEWEP Energy Report (Status 2001-2004). Results of Specific Data for

Energy, Efficiency Rates and Coefficients, Plant Efficiency Factors and NCV of 97

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European W-t-E Plants and Determination of the Main Energy results’, Bamberg October 2005, Update July 2006.

[18] Wilén, C., Salokoski, P., Kurkela, E., & Sipilä, K. (Helsinki 2004). Finnish expert report on best available techniques in energy production from solid recovered fuels, Technical Research Centre of Finland. www.environment

[19] Otoma, S.; Mori, Y.; Terazono, A.; Aso, T.; Sameshima, R. Resources Conservation and Recycling, 1997, 20, 95–117.

[20] Murphy, J.D.; McKeogh, E. Renewable Energy, 2004, 29, 1043–1057. [21] Hernandez-Atonal, F.D.; Ryu, C.; Sharifi, V.N.; Swithenbank, J. Chemical Engineering

Science, 2007, 62, 627 – 635. [22] Marsh, R.; Griffiths, A.J.; Williams, K.P.; Wilcox, S.J. Fuel Processing Technology,

2007, 88, 701–706. [23] Kleis H., & Dalager S. (2004). 100 Years of Waste Incineration in Denmark : From

Refuse Destruction Plants to High – Technology Energy Works. www.wte.org [24] Gohlke O.; Martin J. Waste Manage Res, 2007, 25, 214–219 [25] Bilitewski, B. Proc. Int. Conf. Envir. Manag. Eng. Plan. Econ. (CEMEPE), Skiathos,

Greece, June 2007, 1549-1554. [26] Psomopoulos, C.S.; Bourka, A.; Themelis, N.J. Waste Management, 2009, 29, 1718 -

1724. [27] Themelis, N.J.: “Older and Newer Thermal Treatment Technologies from a Reaction

Engineering”, IT3, Montreal, Canada, 2008. [28] Hilber, T.; Maier, J.; Scheffknecht, G.; Agraniotis, M.; Grammelis, P.; Kakaras, E.;

Glorius, T.; Becker, U.; Derichs, W.; Schiffer, H-P.; De Jong, M.; Torri, L. J. Air Waste Manag. Assoc., 2007, 57(10), 1178-89.

[29] Garg, A.; Smith, R.; Hill, D.; Simms, N.; Pollard, S. Environ. Sci Technol., 2007, 41(14), 4868-74.

[30] Bilitewski, B. Proc. Int. Conf. Envir. Manag. Eng. Plan. Econ. (CEMEPE), Skiathos, Greece, June 2007, 1543-1548.

[31] Keldenich K. & Marzi Th. (2006), European Study on RDF, Frauenhofer Institute for Environmental Safety and Energy Technology Umsicht.

[32] RECOFUEL; TREN/04/FP6EN/S07.32813/503184; http://www.eu-projects.de/ recofuel .

[33] CERTH/ISFTA, 2002. Co-gasification of coal and wastes for power generation, THERMIE-SF/08/98/DE, Final Report.

[34] Grammelis, P.; Kakaras, E.; Skodras, G. J. Air Waste Manag. Assoc., 2003, 53(11), 1301-11.

[35] Kakaras, E.; Grammelis, P.; Agraniotis, M.; Derichs, W.; Schiffer, H-P.; Maier, J.; Hilber, T.; Glorius, T.; Becker, U. Thermal Sci. J., 2005, 9, 17-30.

[36] Koukouzas, N.; Katsiadakis, A.; Karlopoulos, E.; Kakaras, E. Waste Management, 2008, 28, 1263–1275.

[37] Envitec, S. A., The MSW Recycling and Composting Plant in Ano Liosia, Information brochure, 2004

[38] Association of Communities and Municipalities in the Attica Region (ACMAR), 2009. Project: Composition and physicochemical properties of MSW of Attica 2006-2008. Presentation in Environmental Protection Committee of The Greek Parliament, January 29, Athens, Greece.


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[39] Economopoulos, P.: Methodology for Development of an Optimized Waste Treatment Plan in the Attica Region, Presentation TEE, December 2004.

[40] Theochari Ch., Aravossis K., Varelidis P., Diavatis I., Ziogas, Ch. Iatrou, S., Bourka A., Economopoulos A., Papagrigoriou S., Pantelaras P., and Frantzis, I.: ‘Solid waste management in Greece, The Attica case’, Technical Chamber of Greece, Athens, November 2006, Final Report.

[41] Statistical Data About Solid Waste Treatment in Greece, Ministry of Environment, Department of Environmental Planning, Section of Solid Waste Treatment: Record Nr. 109947/3120, December 2004

[42] Tsatsarelis Th.; Karagiannidis A. Proc. 2nd Int. Conf. Eng. Waste Valorisation, Patra, Greece, June 2008, 1-8.

[43] Psomopoulos C.S.; Themelis, N.J. Proc. of the 2nd Int.CEMEPE & SECOTOX Conf., Mykonos, Greece, June 21-26, 2009, II, 1121-1126

[44] Psomopoulos, C.S.; Batakis, A.; Daskalakis, J. 6th Mediterranean Conference and Exhibition on Power Generation, Transmission and Distribution, IET Hellas (MedPower 2008), Thessaloniki, 2-5 November 2008, Paper No145, 1-6.


Chapter 7

THE USE OF INDUSTRIAL WASTE FOR THE PRODUCTION OF NEW BLENDED CEMENT

M. C. Bignozzi*

ABSTRACT

Industrial waste of different origins and nature can be used as unconventional constituents for the preparation of new blended cements. This study collects different researches previously carried out with the aim to highlight the feasibility of this recycling route that can be considered highly rewarding for the cement industry. Chemical, physical and mechanical properties of the new blended cements are reviewed and compared with the requirements set by EN 197-1 for common cements.

INTRODUCTION The worldwide cement production in 2007 was 2.77 billion tons [1]: Asia is the first

producer (70%), followed by European Union countries (9.5%). Indeed, cement industry can be considered strategic: in fact, from one side, it produces an essential product in building and civil engineering for the construction of safe, reliable and long lasting buildings and infrastructures. On the other side it is very important from the economic point of view (for example Indian cement industry is playing a very import role in the economic development of the country). However, cement industry environment-wise is also responsible for a large use of not renewable raw materials (clays and calcium carbonate) and fossil fuels (e.g. clinker, the main cement constituent, is obtained at T= 1500°C) resulting in heavy emissions of carbon dioxide (CO2) in atmosphere. In fact, in 2006, the European cement industry used an energy equivalent of about 26 Mt of coal for the production of 266 Mt of cement [2] and it is estimated that 1 ton of CO2 is emitted for each ton of cement produced. This induces cement industry to consider the possibility to introduce waste of different nature and origin in cement

* Dipartimento di Chimica Applicata e Scienza dei Materiali, Facoltà di Ingegneria, Università di Bologna, Italy,

[email protected]

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productive process. Two routes are currently taken into consideration: one involves the use of waste as alternative fuel, the other considers waste as a new cement constituent. However, both routes generate concerns. Using waste as an alternative fuel, it must be excluded the possibility that dangerous volatile compounds such as dioxins can be emitted into the environment during clinker production. Using waste as new cement constituent, it must be ascertained the absence of substances that can negatively interfere with cement reaction.

European standard EN 197-1 [3], providing a complete classification of cements valid in Europe, confirms that a constituent of cement can also be a waste. In fact, except the ordinary Portland cement (OPC) constituted by 95% of clinker (CEM I), blended cements contain, besides clinker, other constituents coming from waste of different productive processes. Blast furnace slag, silica fume and fly ash respectively derive from iron ore processing for cast iron and steel production, from silicon and ferrosilicon alloys production and from coal combustion for electric energy production. Cement classification based on the different constituents is reported in Table 1. It has been proved that the addition of waste such as blast furnace slag, silica fume and fly-ash leads to several advantages for the relevant cements: (i) the lower content of clinker compare to OPC allows to classify these binders as low-heat cements; (ii) the development of cement mechanical strength, although it is slower at the early curing age, noteworthy increases with time, even after 28 days; (iii) durability behavior improves due to a less content of Portlandite, usually formed during OPC hydration reactions. Moreover, blended cements always need less clinker for their production thus involving a minor use of natural raw materials and fuels, less quarries exploitation and lower CO2 emission. When the new cement constituents are waste, benefits as the safeguard of disposal sites and saving of natural raw materials must be added at the above quoted list.

Not all the cement types reported in Table 1 are usually manufactured: so far, as a consequence to produce less clinker, CEM II is the most produced cement with a percentage of 80.8 and 56.1 over the total production, in Italy and Europe respectively. Figure 1 shows how CEM II is fractioned on the market [4,5]: although Portland-limestone cement is the most popular, CEM II based on waste (blast furnace slag, silica fume, fly ash, with an amount ranging from 6 to 35%) is 48.2% in Europe, thus meaning that recycling is already successfully adopted in cement industry.

With the aim to pursue waste suitable to work as new cement constituents, several researches have been carried out specifically studying ground glass [6-8], matt waste [9,10], rice husk ash [11], municipal solid waste incinerator bottom ash [12], ceramic waste [13], ferroalloy industry waste [14], electric-arc furnace slag [15], etc..

In this work industrial waste and relevant new blended cement constituted by 25 wt% waste and 75 wt% CEM I, previously separately investigated [9,10,13,15], are collectively reported and compared.

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Table 1. Cement classification according to EN 197-1 (wt%) (Minor additional constituents (0-5%) are not reported for brevity sake).

Main types

Notations Main Constituents Clinker K

Blast Furnace slag S

Silica fume D

Pozzolana Fly ash Burnt shale T

Limestone

nat P

natural calcined Q

Sil. V

Calc. W

L

LL

CEM I Portland Cement CEM I 95-100 - - - - - - - - -

CEM II

Portland slag cement

CEM II/ A-S 80-94 6-20 - - - - - - - -

CEM II/ B-S 80-94 21-35 - - - - - - - -

Portland silica-fume cement

CEM II/A-D 90-94 - 6-10 - - - - - - -

Portland pozzolan cement

CEM II/A-P 80-94 - - 6-20 - - - - - -

CEM II/B-P 65-79 - - 21-35 - - - - - -

CEM II/A-Q 80-94 - - - 6-20 - - - - -

CEM II/B-Q 65-79 - - - 21-35 - - - - -

Portland fly-ash cement

CEM II/A-V 80-94 - - - - 6-20 - - - -

CEM II/B-V 65-79 - - - - 21-35 - - - -

CEMII/A-W 80-94 - - - - - 6-20 - - -

CEMII/ B-W 65-79 - - - - - 21-35 - - -

Portland burnt shale cement

CEMII/ A-T 80-94 - - - - - - 6-20 - -

CEMII/ B-T 65-79 - - - - - - 21-35 - -

Portland limestone cement

CEM II/A-L 80-94 - - - - - - - 6-20 -

CEM II/B-L 65-79 - - - - - - - 21-35 -

CEM II/A-LL 80-94 - - - - - - - - 6-20

CEM II/B-LL 65-79 - - - - - - - - 21-35

Portland composite cement

CEM II/A-M 80-94 6-20

CEM II/B-M 65-79 21-35

CEM III

Blast furnace cement

CEMIII/A 35-64 36-65 - - - - - - - - CEMIII/B 20-34 66-80 - - - - - - - - CEMIII/C 5-19 81-95 - - - - - - - -

CEM IV

Pozzolan cement

CEMIV/A65-89 - 11-35 - - - CEMIV/B 45-64 36-55 - - -

CEM V Composite cement

CEMV/A 40-64 18-30 - 18-30 - - - - CEMV/B 20-38 31-50 - 31-50 - - - -

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Figure 1. Italian and European market division (%) for the different types of CEM II [4,5].

Their chemical, physical and mechanical characteristics are discussed in the framework of the requirements imposed by the European standard EN 197-1. The industrial waste considered is matt waste (MW), which derives from purification processes of cullet coming from separated glass waste collection, polishing (PR) and glazing (GR) residues, coming from porcelain stoneware polishing and glazing sludge, respectively, and ladle electric-arc furnace slag (LS), generated in the refining process of electric-arc furnace steels production. The four types of waste, coming from glass, ceramic and steel industry, are produced in large amount (6000 ÷ 25000 t/y), thus ensuring a noteworthy quantity of recyclable material for cement production.

THE CHEMICAL-PHYSICAL CHARACTERIZATION OF THE INVESTIGATED WASTE

A highly representative batch of each of the investigated waste was collected: MW was

kindly supplied by Sasil, Gruppo Minerali (Novara, Italy), LS by Acciaieria di Rubiera (Casalgrande, Reggio Emilia, Italy), porcelain stoneware polishing and glazing sludge by S.A.T. S.p.A. Service for the Environment (Sassuolo, Modena, Italy) and by different glazing lines of a single Italian manufacturer, respectively. All the materials were submitted to some treatments before their use. Porcelain stoneware polishing and glazing sludge were dried (T=105°C for 24-36 h) to obtain solid residues (PR and GR) and ground in a laboratory ball mill to reach a grain size distribution close to that of commercial cement. MW was also ground for the same reason. Ladle slag, although is produced as a very fine powder, was sieved to eliminate the fraction greater than 0.106 mm. Figure 2 collectively reports the grains size distributions of MW, LS, PR, GR and that of a commercial OPC CEM I 52.5 R: the average size, ranging from 6 to 20 μm, increases in this order: LS > CEM I > GR > PR > MW.

A chemical and mineralogical characterization of the materials was then carried out to establish the main oxide constituents and mineralogical phases. The results are summarized in Tables 2 and 3: SiO2 is the main constituent of MW, GR and PR, but while MW has the typical chemical-mineralogical composition of soda-lime glass (about 10 and 13 wt% content of CaO and Na2O, respectively, and amorphous silica phase), GR and PR are also rich in Al2O3 (15-20 wt%) and ZrO2 (1-3 wt%), minerals such as zircon, quartz and albite deriving


195

from glazing and porcelain stoneware body, respectively. The main constituents of LS are CaO (55 wt%), SiO2 (24 wt%) and Al2O3 (13wt%) with mineralogical crystalline phases as calcium silicates and aluminates.

Figure 2. Grains size distribution of the investigated industrial waste.

Table 2. Chemical analysis (main oxide, wt%) of the investigated industrial waste (x-ray fluorescence spectrometer, XRF, PW 1414, Philips).

Oxide MW (%)

LS (%)

GR (%)

PR (%)

SiO2 71.04 23.85 52.36 62.19 Al2O3 2.02 13.69 19.37 15.75 TiO2 - 0.20 0.45 0.34 Fe2O3 0.35 3.85 0.84 0.59 CaO 10.58 55.24 5.73 2.24 MgO 1.75 3.22 2.43 6.75 K2O 0.75 0.22 1.32 1.46 Na2O 13.52 0.31 3.90 3.71 ZrO2 n.d. <0.10 3.01 1.19 MnO n.d. 0.32 <0.10 <0.10 ZnO n.d. <0.10 0.99 0.12 BaO n.d. <0.10 0.54 <0.10

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Table 3. Main mineralogical phases of the investigated industrial waste (x-ray diffractometer with Ni-filtered Cu Kα (λ = 1.54 Å) radiation, XRD PW 1840, Philips).

MW LS GR PR

Crystalline phase n.d. olivine (γ−C2S), ghelenite, mayenite, iron silicates, iron magnesium calcium silicate

quartz, zircon, albite

quartz, albite calcian

Amorphous phase silica n.d. silica silica EN 197-1 sets specific requirements concerning the amount of chloride and sulphate in

cement; loss of ignition (LOI) must be also limited to a value ≤ 5.0%. These limitations are necessary to ensure that deleterious reactions, such as steel bar corrosion and/or delayed ettringite formation, induced by Cl- and SO4

-2 respectively, do not occur in cement base materials.

Table 4 reports the values determined according to EN 196-2 [16] for the investigated materials and OPC CEM I 52.5R. MW, LS and GR values agree with all the limits sets, whereas PR exhibits a higher Cl- content and slightly overcomes the limit LOI value. Cl- derives from the salts (AlCl3, FeCl3) used as flocculants in the separation process and from the magnesium chloride matrix of abrasive tools used for polishing. The LOI value is mainly related to the presence of calcite phase and SiC, coming from the abrasive tools. However, both the data can be acceptable as PR is going to be used mixed with CEM I 52.5 R (25 and 75% respectively), hence the overall Cl- % and LOI will be inside the limits required for cement.

Besides chemical requirements, physical properties such as setting time and soundness [17] are very important to establish if a cement based binder is suitable to be adopted in the building industry. Setting time is a measurement of the time required by a cement paste to start hydration reactions thus leading to a loss of workability at the fresh state; soundness test allows to determine if volume expansion of cement paste occurs under accelerated curing conditions. Deleterious expansion phenomena are usually caused by the presence of free CaO and MgO in the binder. Table 5 reports the results obtained on the new blended cement based on the investigated waste, having the general composition: 75 wt% CEM I 52.5 R + 25 wt% waste. The results determined for 100 wt% CEM I 52.5 R are reported for comparison as well as the limits set by EN 197-1. Soundness results of all the new blended cement are comparable with that of CEM I and well below the limit; the same can be observed for the initial setting time, except for that of the binders containing MW and GR, which are slightly higher than 107 min. Such increase, although still acceptable for cement binder, has been ascribed by organic impurities (≤ 1%) that leads to a slight slow down of initial setting reactions.

The chemical and physical parameters obtained for MW, LS, GR and PR allow their use as new constituent for cement production according to the restrictions reported by the European standard.


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Table 4. Chemical analysis results of the investigated industrial waste and CEM I 52.5 R (average of 2 measurements). Limits set by EN 197-1 for cement are also reported.

MW LS GR PR CEM I 52.5 R

Limits set by EN 197-1 for cement

Chloride (wt %) EN 196-2 0.04 ≤ 0.01 ≤ 0.01 0.24 0.04 ≤ 0.1

Sulfate (SO3 wt %) EN 196-2 ≤ 0.01 0.38 0.06 0.09 0.65 ≤ 3.5

Loss of Ignition (wt %) EN 196-2 0.8 2.7 2.9 5.2 3.6 ≤ 5.0

Table 5. Physical properties of the investigated binder based on industrial waste and

CEM I 52.5 R (average of 2 measurements). Limits set by EN 197-1 for cement are also reported.

binder Initial setting time (min)

Soundness (mm)

CEM I 52.5 R 107 0.2 75% CEM I 52.5 R + 25% MW 134 0.3 75% CEM I 52.5 R + 25% LS 106 0.4 75% CEM I 52.5 R + 25% GR 117 0.2 75% CEM I 52.5 R + 25% PR 105 0.2

Limits set by EN 197/1 for cement 32.5 R ≥ 75

≤ 10 42.5 R ≥ 60 52.5 R ≥ 45

THE BEHAVIOR OF THE NEW BINDERS AT THE FRESH AND HARDENED STATE

Two parameters are extremely important for a binder involved in concrete production:

workability and compressive mechanical strength determined at the fresh and hardened state respectively. For the binders under studying, workability was measured by minislump test [18] on paste sample prepared with a water/binder ratio equal to 0.5. The results, reported in Table 6, shows that workability increases in this order: CEM I > MW-binder > LS-binder > GR-binder > PR-binder. Workability is strictly related to waste average size, shape and its tendency to form particles agglomerates.

As far as concern mechanical requirements, EN 197-1 sets for each kind of cement reported in Table 1 a division based on cement mechanical strength: three classes (32.5, 42.5 and 52.5 N/mm2 determined at 28 days of curing) are identified and each class can have a normal (N) or rapid/early (R) strength development (Table 7).

Compressive strength was determined on mortar samples prepared, by Hobart planetary mixer, according to the normalized mix-design (binder, sand and water in a weight ratio of 1:3:0.5) and procedure for cement mechanical strength determination (EN 196-1, [19]).

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Mortar samples were named M, followed by the acronym of the waste type used; mortar prepared with CEM I 52.5 R was identified as MREF. Figure 3 collectively reports the compressive strength at 2, 7 and 28 days and the following observation can be drawn: (i) all the new blended cements exhibit a compressive strength lower than that of CEM I 52.5 R at all curing times; (ii) according to the limits reported for cements, all the new blended binders overcome the threshold values at 2 and 28 days required for 42.5 R strength class; (iii) only the PR based binder reaches the limits required to be classified in the 52.5 R strength class.

Table 6. Workability results at the fresh state (average of 2 measurements).

binder water/binder ratio

minislump (mm)

CEM I 52.5 R 0.5 80 75% CEM I 52.5 R + 25% MW 0.5 70 75% CEM I 52.5 R + 25% LS 0.5 62 75% CEM I 52.5 R + 25% GR 0.5 55 75% CEM I 52.5 R + 25% PR 0.5 45

It is usual that the addition of a constituent with a different chemical composition from clinker may decrease the development of mechanical strength in the first 28 days of curing, however pozzolan and blast furnace slag constituents usually lead to a continuative increase in the mechanical properties with curing, even after 28 days. A useful tool to understand if a new constituent is involved in mechanical strength development at long curing time is the determination of the activity index (AI). This index, reported in EN 450-1 [20] for concrete fly ash, is the compressive strength ratio between samples containing 75% CEM I 52.5 R + 25% waste and reference mortar with 100% CEM I 52.5 R, cured at 28 and 90 days. Values of AI ≥ 75 and 85% at 28 and 90 days, respectively, mean that the new constituent is active in the strengthening development. The data, collected in Table 7, show that the activity index of the investigated waste increases with this order: PR>MW>GR>LS.

LS and GR exhibit a lower/almost equal AI than the limit at 90 days, thus indicating that their action as cement constituent is limited to a filler effect. Activity index of MW and PR largely overcomes the limit, thus meaning that MW and PR actively participate in mechanical strength development.

Table 7. Cement classification based on the development of compressive strength.

Strength class Compressive strength (MPa) 2 days 7 days 28 days

Limits set by EN 197-1 for cement

32.5 N ≥ 16.0 ≥ 32.5 ≤ 52.5 32.5 R ≥ 10.0 -

42.5 N ≥ 10.0 ≥ 42.5 ≤ 62.5 42.5 R ≥ 20.0 -

52.5 N ≥ 20.0 ≥ 52.5 52.5 R ≥ 30.0 -


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0

10

20

30

40

50

60

70

MREF MMW MLS MGR MPR

Com

pres

sive

stre

ngth

(MPa

) 2 days 7 days 28 days

Figure 3. Compressive strength at different curing time of mortar samples prepared with the investigated binders.

Clearly, the different behavior of the industrial waste is strictly related to their nature: the amorphous phase of MW makes it similar to an artificial pozzolan constituent (fly ash, silica fume), whereas PR, containing both amorphous and crystalline phases, contributes to the formation of two different types of gels during hardening process, as previously ascertained [13]. Both MW and PR are thus chemically involved in clinker hydration reactions, leading to matrices with very compact microstructures [9,13].

Table 8. Activity index for the investigated industrial waste.

Binder Activity index 28 days 90 days

75% CEM I 52.5 R + 25% MW 84 92 75% CEM I 52.5 R + 25% LS 80 67 75% CEM I 52.5 R + 25% GR 84 88 75% CEM I 52.5 R + 25% PR 90 101 Limits set by EN 450-1 ≥ 75% ≥ 85%

CONCLUSIONS The investigated waste is chemically, physically and mechanically suitable as 25 wt%

constituent for the production of new blended cements. PR blended cement can be classified as 52.5 R strength class, whereas MW, GR and LS blended cement belong to 42.5 R strength class. The waste behaviour is different:

M. C. Bignozzi

200

− GR and LS work more as inert addition (filler effect) than as active constituents of the relevant blended cements. The reason can be found in the crystalline phases characteristic of the two types of waste that are not able to take part/collaborate to the clinker hydration process.

− PR and MW have an active role in the relevant blended cement: activity index of both waste at 90 days is close to 100, thus indicating that compressive strength of mortar samples increases with curing time, event after 28 days.

More investigations concerning microstructure of the mortar samples prepared with MW,

LS, GR and PR and their comparison with an OPC mortar, are reported elsewhere [9,13,15].

REFERENCES

[1] Activity Report of 2007, The European Cement Association, www.cembureau.eu, 2008. [2] Sustainable cement production, The European Cement Association,

www.cembureau.eu, 2009. [3] EN 197-1, 2004. Composition, specifications and conformity criteria for common

cements. [4] Data from The European Cement Association, www.cembureau.eu, 2005. [5] Data from AITEC, www.aitecweb.com, 2006. [6] T. D. Dyer, R. K. Dhir, Chemical reactions of glass cullet used as cement component, J

. Mater. Civ. Eng. 13, 412–417 (2001). [7] C. Shi, Y. Wu, C. Riefler, H. Wang, Characteristics and pozzolanic reactivity of glass

powders, Cem. Concr. Res., 35, 987–993 (2005). [8] M. C. Bignozzi, “Glass and concrete: together for sustainability in construction

industry” in Proceedings of the 1st International Conference of Recycling and Reuse of Materials, July 17-19th, 2009, Kottayam, India.

[9] M. C. Bignozzi, A. Saccani, F. Sandrolini, Matt waste from glass separated collection: An eco-sustainable addition for new building materials, Waste Management, 29, 329 – 334, (2009).

[10] [10] M. C. Bignozzi, A. Saccani, F. Sandrolini, Matt waste from glass separated collection: A reactive addition to cement, submitted to Building and Construction.

[11] M. Anwar, T. Miyagawa, M. Gaweesh, Using rice husk ash as a cement replacement material in concrete, Waste Management Series, 1, 671-684 (2000).

[12] A. Saccani, F. Sandrolini, F. Andreola, L. Barbieri, A. Corradi, I. Lancellotti, Influence of the pozzolanic fraction obtained from vitrified bottom-ashes from MSWI on the properties of cementitious composites, Materials and Structures, 38, 367-371 (2005).

[13] F. Andreola, L. Barbieri, M. C. Bignozzi, I. Lancellotti, F. Sandrolini, New Blended Cement from Polishing and Glazing Ceramic Sludge, International Journal of Applied Ceramic Technology, DOI: 10.1111/j.1744-7402.2009.02368.x.

[14] [14] M. Frıas, C. Rodríguez, “Effect of incorporating ferroalloy industry wastes as complementary cementing materials on the properties of blended cement matrices,” Cement & Concrete Composites, 30, 212–219 (2008).


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[15] M.C. Bignozzi, F. Sandrolini, F. Andreola, L. Barbieri, I. Lancellotti, Recycling Electric Arc Furnace Slag as Unconventional Component for Building Materials, submitted for the Proceeding of 2nd International Conference on Sustainable Construction Materials and Technologies, 28-30 June 2010, Ancona (Italy).

[16] EN 196-2, 2005. Methods of testing cement - Part 2: Chemical analysis of cement. [17] EN 196-3, 2005. Methods of testing cement Part 3: Determination of setting times and

soundness. [18] D. L. Kantro, Influence of water reducing admixtures on properties of cement paste. A

miniature slump test, Cem. Concr. Aggreg. 2, 95 (1980). [19] EN 196-1, 2005. Methods of testing cement - Part 1: Determination of strength. [20] EN 450-1, 2007. Fly ash for concrete - Part 1: Definition, specifications and conformity

criteria


Chapter 8

OLIVE MILL WASTEWATER: TREATMENTS AND VALORISATION

Manuela Taccari* and Maurizio Ciani

ABSTRACT

Olive mill wastewaters represent a serious environmental problem in Mediterranean countries, as the high concentrations of phenols, lipids and organic acids can have phytotoxic effects. On the other hand, this waste also contains valuable compounds, such as a large amounts of organic matter and a wide range of nutrients that could be recycled. In this chapter, the most interesting physico-chemical and biological processes for the treatment of these effluents are presented. Remediation by means of physical and chemical methods are generally expensive, and they do not often provide complete purification. Indeed, despite the effectiveness of such techniques, few of them have been applied on an industrial basis. Biological processes for the treatment of olive mill wastewaters have seen worldwide applications, and they are considered to be environmentally friendly, reliable and, in most cases, cost effective. Moreover, some biological treatments are effective for the valorisation of this organic waste.

1. INTRODUCTION

1.1. Olive Oil Extraction Systems and the Wastes Produced Olive oil production is one of the most important agro-food sectors in the whole of the

Mediterranean area, and it is still of primary importance for the economy of several Mediterranean countries. Spain is the main World producer of olives, followed by Italy, Greece, Turkey, Syria and Tunisia. Among these countries, the European Union (i.e. Spain, Italy, Greece) provide about 75% of the World production. However, many other countries,

* Dipartimento S.A.I.F.E.T., sez. di Microbiologia Alimentare, Industriale e Ambientale, Università Politecnica

delle Marche,Via Brecce Bianche, 60131 Ancona, Italy, [email protected]

Manuela Taccari and Maurizio Ciani

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such as Argentina, Australia and South Africa, are newly emergent producers, since they are promoting intensive olive tree cultivation.

There are two main olive oil production systems: (i) the traditional pressing system that has been used for many centuries with only minor modifications; and (ii) the continuous, three-phase and two-phase systems that were introduced over the last few decades in order to increase the processing capacity and the extraction yield (Fig. 1) (Alburquerque et al., 2004).

Washing (Cold)

Olive oil (≈20 kg)

Decanting separation by gravity or by centrifugation

Olives (100 kg)

Milling and beating

Mechanical pressing

Traditional system

(10-50 L) Washing water

Olive oil(≈21 kg)

Oil washing/ recovery of the oil in the liquid fraction

Olives(100 kg)

Milling and beating

Centrifugation(three-phase decanter)

Washing(Cold)

(70-100 L) OMW

Olive cake(30-60 kg)

Three-phase system

Washing water

Hot water (50- 85 L)

(0-18 L)

Olive wetcake

(70-80 kg) Centrifugation

(two-phase decanter)

Olives (100 kg)

Milling and beating

Washing (Cold)

Two-phase system

Olive oil (≈20 kg)

Oil washing Waste water

Washing water

Figure 1. The olive oil extraction processes (Alburquerque et al., 2004; IMPEL 2003).

The traditional system is still being used by some olive oil producers. After the extraction by the pressing of the olive husk, a solid by-product is obtained, along with an emulsion that contains the olive oil and the vegetation water, known as the olive mill wastewater (OMW); these are separated by decanting or using a vertical centrifuge.

The three-phase system generates three fractions at the end of the process: olive oil, vegetation water and a solid residue composed of the olive skin and stones (olive husks). Even though this system has advantages when compared to traditional pressing (e.g. continuous, automated, high percentage of oil extraction, better oil quality), it has some disadvantages too (e.g. greater water and energy consumption, higher wastewater production) (Roig et al., 2006).

In both of these systems (traditional and three-phase), the environmental problems lie in the large volumes of water that have to be added and in the elimination of the substantial quantity of waste that is generated. This wastewater is characterised by high organic matter concentrations and phytotoxicity, and despite current legislation, it is frequently discharged into rivers and the soil without prior treatment. This practice can lead to serious environmental problems in the Mediterranean area.

In recent years, a new, “ecological”, two-phase extraction process has been introduced in modern mills. This has reduced the amounts of water needed and the waste produced during

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olive oil extraction (Azbar et al., 2004). This two-phase process generates two fractions: the olive oil and a new semi-solid by-product that is often referred to as “pomace” or “alperoujo”, and is characterised by a high moisture content (from 55%-70%). Although this new system has environmental advantages, the management of the by-products that contain considerable amounts of lipids, organic acids and phenols has became a serious problem for olive mills (Alfano et al., 2008; Baeta-Hall et al., 2005; García-Gómez et al., 2003). Usually, this solid waste is dried and subjected to a subsequent extraction with organic solvents, which improves the yield of oil and produces a dry olive residue. The fact that with considerably less water is required for this two-phase system, this has encouraged its widespread adoption in Spain and Croatia. However, it has not significantly penetrated olive oil production in the other countries, probably due to the difficulties involved in the handling of the waste (Fig. 2) (McNamara et al., 2008).

0%

20%

40%

60%

80%

100%

Spain Italy Greece Portugal Croatia

press 3-phase 2-phase

Figure 2. Olive oil extraction technologies used by European olive oil mills (IMPEL, 2003).

1.2. Olive Mill Wastewater Characteristics

The composition and chemical characteristics of OMW are not constant (Table 1), either

qualitatively or quantitatively, and they can vary according to the climatic conditions and the olive varieties, ripeness, cultivation methods, and oil extraction procedure (Filidei et al. 2003; Martines-Garcia et al. 2007; Paredes et al. 2005; Piperidou et al. 2000; Vlyssides et al. 2004). Typically, the weight composition of OMW is 83% to 96% water, 3.5% to 15.0% organics and 0.5% to 2.0% mineral salts. The organic fraction is composed of sugars (1.0%-8.0%), N-compounds (0.5%-2.4%), organic acids (0.5%-1.5%), fats (0.02%-1.0%) and phenols and pectins (1.0%-1.5%) (Martinez-Garcia et al., 2009). The maximum biological oxygen demand (BOD5) and chemical oxygen demand (COD) of OMW are as high as 100 and 220 g l-1, respectively (Azbar et al., 2004; Sabbah et al., 2004).


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Another characteristic of this kind of waste is the ease with which it can ferment during storage, which gives rise to substantial changes in its composition, although this does not necessarily result in its complete biodegradation.

Table 1. Chemical characteristics of olive mill wastewater across several studies in the

literature.

Parameters (a) (b) (c) (d) (e) (f) (g) Dry matter (%) 6.35 n.d 1.9 n.d 7.1 7.19 n.d pH 4.8 5.1 5.5 5.04 4.93 5.17 5.46 EC (dS/m) 12.0 8.9 0.53 n.d 7.3 5.50 n.d OM (g l-1) 57.4 n.d 13 n.d n.d 46.5 n.d TOC (g l-1) 39.8 25.5 n.d 29.2 n.d 34.2 n.d TN (g/l) 0.76 0.6 n.d n.d 0.62 0.63 1.35 P2O5 (g l-1) 0.53 0.03 0.1 0.23 n.d 0.31 0.72 K2O (g l-1) 2.37 8.8 1.2 n.d n.d 4.46 4.44 Na (g l-1) 0.30 0.94 n.d n.d n.d 0.11 n.d Ca (g l-1) 0.27 1.2 n.d n.d n.d 0.30 n.d Mg (mg l-1) 50 187 n.d n.d n.d 129 n.d Fe (mg l-1) 32 32 41 n.d n.d 68.5 n.d Cu (mg l-1) 6 n.d 1 n.d n.d 1.5 n.d Mn (mg l-1) 12 n.d 1 n.d n.d 1.1 n.d Zn (mg l-1) 12 n.d 4 n.d n.d 4.1 n.d d (g/cm3) 1.048 n.d n.d n.d n.d 1.02 n.d Lipids (g l-1) 1.64 n.d n.d 0.02 8.6 3.1 n.d Polyphenols (g l-1) 10.7 9.2 n.d 0.7 0.98 1.6 7.18 Carbohydrates (g l1) 16.1 n.d n.d n.d 4.8 8.79 n.d COD (g l-1) 93 72 n.d 90 67 n.d 100 BOD5 (g l-1) 46 13 n.d n.d n.d n.d 29.4 EC, Electrical Conductivity; OM, organic matter; TOC, total organic carbon; TN, total nitrogen; d,

density; COD, chemical oxygen demand; BOD5, biological oxygen demand; n.d., not determined. Data extracted from (a) Vlyssides et al. (2004); (b) Mekky et al. (2009); (c) Paredes et al. (2005); (d)

Martines-Garcia et al. (2007); (e) Filidei et al. (2003); (f) Piperidou et al. (2000); and (g) Dhouib et al. (2006). For the phenols in OMW, these are usually low-molecular-weight compounds

(hydroxytyrosol, tyrosol, catechol, methylcatechol, caffeic acid), along with the polyphenols that result from polymerisation of the simple phenolic compounds (Tziotzios et al., 2007). The concentrations of phenolic compounds in OMW can vary greatly, from 0.5 to 24.0 g l-1 (Paraskeva, and Diamadopoulos, 2006). The toxicity, antimicrobial activity and consequent difficult biological degradation of OMW is essentially linked to this phenolic fraction (Aggelis et al., 2003; Mekki et al., 2006), which is characterised by its great complexity, with more than 20 different phenolic compounds having been identified (Bianco et al., 2003). Indeed, olives are very rich in phenolic compounds, although just 2% of the total phenolic content of olives remain in the oil phase; the remaining phenolic contents of the olives is lost in the OMW (53%) and the pomace (45%) (Rodis et al., 2002). Nevertheless, polyphenols are not necessarily solely responsible for the phytotoxic properties of OMW. Capasso et al. (1992) demonstrated that OMW remained phytotoxic to vegetable marrow and tomato plants even after the total extraction of the polyphenols, while Pérez et al. (1986) reported that


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totally removing the organic matter from OMW did not avoid the phytotoxicity toward barley and tomato germination and early plant growth. These studies suggest that other factors contribute to the phytotoxicity of OMW. According to Paredes et al. (1999), the phytotoxic activity of OMW is also related to its low pH and low salt levels, in addition to the phenols.

1.3. Olive Oil Production and the Environment In the olive oil production process, the disposal of OMW represents the main

environmental problem. In total, Mediterranean countries produce around 30 million m3 of OMW annually. Due to the importance of OMW as a pollutant, its disposal constitutes a serious problem, and the development of effective treatment technologies remains a priority, particularly as in many countries OMW is still discharged directly into the environment, without any treatment. Indeed, at present there is no European legislation regulating olive mill discharges, as it has been left to individual countries to specify their own standards. In Morocco, OMW is often illegally spread on the soil, poured directly into the sewage system, or evaporation in lagoons to reduce its volume (El Hassani et al., 2009; Zenjari et al., 2006).

For other countries, the only “treatment” process used in Tunisia is atmospheric evaporation in open-air ponds under natural conditions (Hachicha et al., 2009 a), although Greece regulation requires that liquid OMW disposal is carried out in septic tanks or in subterranean irrigation. The prefectures also often demand the neutralisation of OMW, with the addition of lime prior to its disposal in surface water (Kapellakis et al., 2006). In Spain, a law has prohibited the discharge of OMW into public waters since 1983, which has pushed olive mill operators to avoid the three-phase centrifugation system that involves OMW production (Sierra et al., 2001). One alternative that is economically advantageous is the controlled land application of OMW. In Italy, although under restricted conditions, the law allows the spreading of up to 50 m3 ha-1 and 80 m3 ha-1 per year for OMW that is generated by the pressing and continuous centrifugation methods, respectively (Law N°. 574, 1996). In this respect, OMW is considered as a useful, low-cost adjunct and fertiliser, which at the correct application rate is not harmful to crops and can be disposed of without causing environmental damage.

Several studies have investigated the effects of spreading OMW directly on agricultural soils, with contradictory results. An increase in productivity in response to OMW spreading was seen in soil cultivated with different types of cereal crops (Rinaldi et al., 2003; Montemurro et al., 2004). Other studies explored the impact of OMW on various chemical properties of the soil and showed a temporary decrease in soil pH, with increased salinity and elevated phenol concentrations (Paredes et al., 1999; Zenjari et al., 2001). In a recent study, Di Serio et al. (2008) reported an increase in the soil total microflora and a reduction of the total content of phenols in the soil after OMW spreading in soil cultivated with olive trees. Another study reported that OMW additions without pre-treatment resulted in a modification of physicochemical characteristics of the soil (Mekki et al., 2006). Indeed, the same authors confirmed more recently that OMW treatment is necessary before its application to the soil, to limit the negative impact on the biological activities of the soil (Mekki et al., 2009).

Thus these data are somewhat contradictory, and the practice of spreading OMW onto agricultural soil has until now been a subject of great controversy in the scientific community.


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2. OMW TREATMENT AND VALORISATION In recent years, many different processes have been proposed for the treatment and

valorisation of OMW, including the use of physical, chemical, biological and combined technologies. In addition to being technically feasible, any OMW treatment processes must be efficient and provide a cost-effective solution. Remediation by means of physical and chemical methods are generally expensive, and they often do not provide full purification of OMW, and despite the effectiveness of some of these techniques, few of them have been applied on an industrial basis.

Biological processes for the treatment of OMW have seen worldwide applications and they are considered environmentally friendly, reliable and, in most cases, cost effective. Such treatments include aerobic activated sludge and anaerobic digestion. Aerobic treatments have been proposed based on the actions of various microorganisms, such as filamentous fungi, yeasts and aerobic bacteria, for the reduction of the organic load and to remove phytotoxic compounds and the dark coloration. Anaerobic digestion treatments have also been carried out successfully on OMW. These result in biogas production and much less waste sludge, but their costs do not make them economical for small-scale olive mills (Filidei et al., 2003; Marques, 2001; Hamdi, 1996; Rozzi and Malpei, 1996).

2.1. Physico-Chemical Treatments Simple physico-chemical processes, such as dilution, evaporation, combustion,

coagulation and flocculation, have been used to treat OMW. However, none of these processes alone can reduce the organic load and the toxicity of OMW to acceptable limits (Paraskeva, P., and Diamadopoulos E., 2006). Dilution is often used prior to biological treatments, to reduce toxicity to the microorganisms responsible for the organic matter decomposition (Asses et al., 2000; Ben Othman et al., 2008; Fadil et al., 2003; Tziotzios et al., 2007).

The use of evaporation ponds reduces the volume of OMW without treating the pollutants in the wastewater, and a black, foul-smelling sludge is produced that is difficult to remove. Moreover, this method needs large areas and produces several problems, such as bad odours and permeation (Ginos et al., 2006; Kapellakis et al., 2006; Jarboui et al., 2008; Saez et al., 1992).

Irreversible thermal treatments, such as combustion, have also been attempted as a means of recovering energy for co-fuelling the olive oil extraction plant. Combustion has the advantage that it can overcome the problems of the concentrated residue produced by evaporation treatment, and it provides the possibility of energy recovery. However, this requires expensive facilities and gives rise instead to atmospheric pollution due to the toxic products (Paraskeva et al., 2006).

Coagulation with materials such as lime, alum, ferric chloride and ferrous sulphate has also been used for OMW treatment. Jaouani et al. (2005) demonstrated a two-stage process that comprised aerobic degradation followed by lime coagulation, while Beccari et al. (1999) proposed a pre-treatment by lime coagulation and adsorption on bentonite, followed by


209

anaerobic digestion; they also indicated that this pre-treatment considerably enhanced the anaerobic treatability of the original effluent.

A new technology that has been developed consists of the flocculation of the organic matter of OMW with several cationic and anionic poly-electrolytes (Sarika et al., 2005). This process produces water that can be used for irrigation and a solid fraction that can be composted with other agricultural by-products (Negro and Solano, 1996; Garcia-Gomez et al., 2003). This technology has provided encouraging results, despite the relatively high cost of poly-electrolytes compared to lime and other inorganic materials.

2.2. Biological Treatment of OMW

2.2.1. Aerobic Treatment

Heterotrophic Aerobic Bacteria A number of different bacteria belonging to the species Bacillus pumilus (Ramos-

Cormenzana et al., 1996), Pediococcus pentosaceus (Ben Othman et al., 2008), Lactobacillus plantarum (Ayed and Hamdi, 2003) Arthrobacter sp.(Knupp et al., 1996), Azotobacter vinelandii (Costantinos et al., 1999; Balis et al., 1996; Piperidou et al., 2000), Pseudomonas putida and Ralstonia sp.(Di Gioia et al., 2001a, b) and various bacterial consortia (Borja et al., 1995; Zouari and Ellouz,1996; Tziotzios et al., 2007) have been indicated as being suitable for aerobic biodegradation and detoxification of OMW (see also Table 2). These studies now focus on the degradation of the phenolic compounds, with heterotrophic aerobic bacteria shown to be very effective against some phenolic compounds, but relatively ineffective against others. For example, Ramos-Cormenzana et al. (1996) showed that Bacillus pumilus cannot degrade tyrosol, while another study reported the complete transformation of tyrosol by Arthrobacter sp. (Knupp et al., 1996).

Several studies of bioremediation of OMW have focused on A. vinelandii, a free-living, N2-fixing bacteria that has been shown to degrade phenolic compounds and to use them as carbon and energy sources. A strain of A. vinelandii isolated from soil repeatedly treated with OMW (Papadelli et al., 1996) was used as an inoculum for aerobic treatment of OMW (Ehaliotis et al., 1999; Piperidou et al., 2000). These investigations have shown that the phytotoxicity of OMW can be reduced by over 90% after an adaptation phase where the presence of the phenolic compounds limits the A. vinelandii growth. In a recent study, some polyphenolic compounds, such as protocatetic acid and p-hydroxybenzoic acid, were demonstrated to facilitate the growth of Azotobacter chroococcum (Juárez et al., 2008).

Lactic acid bacteria have also been proposed for the removal of phenolic compounds from OMW. Pediococcus pentosaceus was tested to determine its ability to decolorise OMW and to remove phenolic compounds (Ben Othman et al., 2008). This study indicated that there was indeed removal of high molecular weight and simple phenolic compounds. Similar results were seen with Lactobacillus plantarum and Lactobacillus paracasei growth on fresh OMW, resulting in polyphenols hydrolysis and an important pH decrease (Ayed and Hamdi 2003; Aouidi et al., 2009).

Bioremediation of OMW using bacterial consortia coming from activated sludge (Borja et al., 1995; Benitez et al., 1997), soil and wastewater (Zouari and Ellouz, 1996), and using


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olive fruit bacteria (Tziotzios et al., 2007) have provided significant reductions in the COD of up to 80%, along with a decrease in the phytotoxic compounds.

Filamentous Fungi and Yeasts

The activity of ligninolytic fungi for aerobic OMW bioremediation has been extensively demonstrated. Basidiomycetes fungi belonging to the “white-rot” group that has been shown to be active for the reduction of the phytotoxic and antibacterial activities of OMW. While monomeric phenols show phytotoxic and antimicrobial activities (Capasso et al., 1992), polymeric phenols have a lignin-like structure as their most recalcitrant fraction, and these are mainly responsible for the typical colour of OMW (Hamdi, 1993).

It is generally believed that the ligninolytic enzymes lignin peroxidase (LiP), manganese peroxidase (MnP) and laccase that are characterised by low substrate specificities are involved in fungal degradation of the polyphenols in OMW (Sayadi et al., 1995; Vahabzadeh et al., 2004). In this context, lignocellulosic substrates, such as wheat straw or hemp woody core, have roles as inducers in the production of ligninolytic enzymes (Arora et al., 2002; Kapich et al., 2004).

Several studies have investigated the potential applications of white-rot fungi for the decoloration and detoxification of OMW (Aloui et al., 2007; Garcìa Garcìa et al., 2000; Jaouani et al., 2003; Kissi et al., 2001). Among the white-rot fungi, Phanerochaete chrysosporium has been described as the most efficient OMW decolorising strain (Dias et al., 2004; Ahmadi et al., 2006; Kissi et al., 2001). Other studies have demonstrated that the edible white-rot fungus Pleurotus can degrade OMW (Aggelis et al., 2003; Fountoulakis et al., 2002 Olivieri et al., 2006; Kissi et al., 2001; Tsioulpas et al., 2002). The white-rot fungi thus appear to be quite effective, as they can achieve removal rates as high as 88% for the COD, 100% for phenolics, and 81% for coloration. In a comparative study of aerobic pretreatment of OMW, the use of two white-rot fungi (Phanerochaete chrysosporium and Geotrichum candidum ) and two species of Aspergillus (A. niger and A. terreus) was investigated (Garcia Garcia et al., 2000). This study indicated that G. candidum can grow in OMW and decrease its organic charge, but here G. candidum did not affect the phenolic content, while for the other organisms tested, their efficiencies for the removal of total phenols showed the following order: Phanerochaete chrysosporium > Aspergillus niger > Aspergillus terreus. In a recent study, Afify et al. (2009) used Aspergillus wentii, Aspergillus niger and Pleurotus ostreatus for the biological treatment of OMW, and they showed that the optimum OMW dilution was 10-fold, where the maximum COD removal (62.2%) and maximum phenolic compound reduction (80.9%) by A. wentii were obtained.

A comparative study on the biodegradation of fresh OMW and stored black OMW by G. Candidum indicated that a reduction of COD (65%) and colour (75%) occurred when the G. Candidum was grown in fresh OMW, while no decoloration was seen for the stored black OMW (Assas et al., 2002). The reduction of COD and colour removal after this treatment of OMW is thus different, even with the same microorganism and operating conditions, because of the variable polymerisation of the phenolic compounds in the OMW during storage, which can cause difficulties for the biodegradation.

Recently, several investigations have evaluated the ability of yeast to detoxify OMW, as well as to produce biomass and/or other valuable products, such as enzymes and organic acids (D’Annibale et al., 2006a, b; Lanciotti et al., 2005; Papanikolaou et al., 2008; Scioli and Vollaro, 1997). Indeed, yeast are well adapted for growth in OMW, since they can resist the


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high concentrations of phenols and the low pH (Amaral et al., 2008; Shivarova et al., 1999; Yan et al., 2005). Moreover, yeast appear to be the dominant microorganisms in the OMW, as compared to bacteria and moulds (Ben Sassi et al., 2006). Yeast species such as Candida tropicalis, Candida cylindracea and Yarrovia lypolitica have been shown to be suitable for aerobic biodegradation and detoxification of OMW (Crognale et al., 2006; D’Annibale et al., 2006; Gonçalves et al., 2009; Lanciotti et al., 2005; Martinez-Garcia et al., 2007; Martinez-Garcia et al., 2009; Scioli and Vollaro, 1997). Recently, Gonçalves et al. (2009) reported that Candida cylindracea was the best species relative to lipase production and for COD reduction, while catechol was shown to be the most inhibitory phenolic compound for this yeast. Several strains with different origins and belonging to Yarrovia lypolitica, a lipolytic yeast species, have been tested for their ability to grow in OMW and to metabolise its lipid fraction (Lanciotti et al., 2005). From the screening carried out, some strains are good candidates for the reduction of polyphenol content and for the production of enzymes and metabolites, such as lipase and citric acid.

Summarising the results of these investigations, it is possible to conclude that instead of thinking in terms of “disposal”, a better approach for OMW would be to consider this waste as a possible resource to be valorised. Indeed, OMW can be considered as a useful growth medium for various biotechnological fungal applications, e.g. metabolite production and/or biotreatment, that can also aim at improving its characteristics as a potential fertiliser.

Table 2. COD and phenol effects of treatment of olive mill wastewater with various aerobic cultures.

Culture COD reduction (%)

Phenol reduction (%) References

Candida cylindracea 70 27 Gonçalves et al., 2009 Candida tropicalis 62 51 Martinez-Garcia et al., 2009 Lactobacillus paracasei 16 22.7 Aouidi et al., 2009 Aspergillus niger > 60 > 60 Hamdi et al., 1992 Geotrichum candidum 65 - Assas et al., 2002 Geotrichum candidum 60 - Asses et al., 2009 Pleurotus ostreatus - 95 Olivieri et al., 2006 Phanerochaete chrysosporium 45 90 Dias et al., 2004 Phanerochaete chrysosporium 50 90 Ahmadi et al., 2005 Geotrichum spp. Aspergillus spp. Candida tropicalis

55 52.5 62.8

46.6 44.3 51.7

Fadil et al., 2003

2.2.2. Anaerobic Treatment

Anaerobic digestion can be defined as the biological conversion of organic material into a variety of non-biodegradable end products, including “biogas”, the main constituents of which are methane (65%-70%) and carbon dioxide. The advantages of anaerobic digestion include low levels of biological sludge, a high efficiency, and the production of methane, which can be used for production.

A variety of anaerobic methods have also been applied to the treatment of OMW, such as: use of granular activated carbon (Bertin et al., 2004); an up-flow anaerobic sludge blanket


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reactor (Boari et al.,1984; Ubay et al., 1997); a silica beads packed bioreactor (Bertin et al., 2004); and anaerobic filters (Mechichi et al., 2005). A reduction in COD from 70% to 89% has been achieved for anaerobic processes (Borja et al., 1996; Marques et al., 1997; Marques, 2001). For example, Dalis et al. (1996) used a two-stage anaerobic reactor with the inoculant undergoing large reductions (>75%) in both toxic phenols and volatile fatty acids. However, the major limitation of these treatments is the inhibition of methanogenic bacteria by the phenolic compounds (e.g., condensed tannins; Zouari and Ellouz, 1996) and the long-chain fatty acids in OMW (Hwu and Lettinga, 1997). One possible approach to resolve this problem is to dilute the OMW to reduce the concentrations of phenolics and fatty acids, although this method was still found not to be satisfactory (Gharsallah, 1994).

Another approach is the use of an aerobic pretreatment of OMW to remove the toxic compounds, thus rendering the effluent more amenable to subsequent treatments. Ruiz-Ordaz at al. (1998) and Martinez-Garcia et al. (2007) used C. tropicalis for aerobic pre-treatment prior to anaerobic digestion. This method does not require dilution and achieves a reduction in the phenol (54%) and COD load.

Fungi have also been used in the pretreatment of OMW prior to anaerobic digestion. Gharsallah et al. (1999) showed that pretreatment of OMW with P. chrysosporium reduced COD but had little effect on the polyphenolics, which remained in the effluent and inhibited subsequent methane production. Different results were obtained by Dhouib et al. (2006), who showed that a pretreatment with P. chrysosporium or Trametes versicolor can lead to a large removal of organic matter, and a decrease in the COD/BOD5 ratio and the toxicity of OMW. The subsequent anaerobic digestion of the OMW pretreated with white-rot fungi showed higher methanisation yields.

Aerobic pretreatment with G. candidum provided a reduction in COD and the phenolic and fatty acid contents of OMW, and an increased substrate uptake during anaerobic digestion was obtained (Martin et., 1993). Furthermore, pretreatment of OMW with the different microorganisms Geotrichum candidum, Azotobacter chroococcum and Aspergillus terreus was shown to reduce the phenolic concentrations and the toxicity of OMW by 59%, 87% and 79%, respectively (Borja et al., 1998). It is also interesting to note that while white-rot fungi appear to be the most effective microorganisms in these aerobic treatment processes, they are sometimes the least effective organisms for pretreating OMW for anaerobic digestion.

2.2.3. Composting

Composting is a widely used treatment for organic wastes, and the composting of OMW to obtained organic fertilisers could be an economical and ecological solution. During the composting process, the organic fraction is aerobically degraded by microorganisms, to give carbon dioxide, water, mineral salts and a stable organic material containing humic-like substances (Paredes et al., 2005). Under optimal conditions, composting proceeds through three phases: (1) the mesophilic phase; (2) the thermophilic phase, which can last from a few days to several months; and (3) the cooling and maturation phase, which lasts for several months (Tuomela et al., 2000). The composting process requires adequate conditions of pH, temperature, moisture, oxygenation and nutrients, to allow the development of the microbial population (Vlyssides et al., 1996). Therefore, changes in these conditions during the process will affect the proliferation of certain microflora that have different enzymatic activities, and which control the organic matter degradation.


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The aerobic composting technologies consist of the windrow (turned pile), aerated static pile and in-vessel techniques, with the first two being the most commonly used. These technologies vary in the methods for the air supply, temperature control, mixing/turning of the material, and time required for composting (Baeta-Hall et al., 2005; Cayuela et al., 2006). The OMW has to be absorbed into a solid substrate before processing it by composting, and various suitable materials have been used as bulking agents, including olive husks (Abid and Sayadi 2006, García-Gómez et al., 2003), wheat straw (Taccari et al., 2009), barley straw (Zenjari et al., 2006), cotton-gin waste (Paredes et al., 2005), poultry manure (Hachicha et al., 2009a) and sesame bark (Hachicha et al., 2009b).

Co-composting OMW sludge with other organic residues so as to provide adequate chemical composition (particularly for the C/N, C/P and N/P ratios) can reduce the phytotoxic effects of the phenolic and lipid compounds in OMW sludge. The resulting compost has shown a high degree of humification, no phytotoxicity effects, and improved mineral nutrient content (Abid et al., 2006; Hachicha et al., 2009 b; Paredes et al., 2002; Zenjari et al., 2006). The application of OMW as a compost to soil has produced positive effects on physical, chemical and biological properties of the soil and a crop production that was comparable to inorganic fertilisation (Hachicha et al., 2008; Paredes et al., 2005). The microbial activity has the main role in the transformations that occur during composting. The inoculation with proper microorganisms may activate the biodegradation of organic matter and improve the quality of the compost. Moreover, ligninolytic microorganisms appear to be the best to conduct the humification process when the substrates being composted are of agricultural origin (Zeng et al., 2009). Taccari et al. (2009) showed that inoculation of P. chrysosporium during compost maturation provided both degradation of the soluble phenols in the OMW and release of water-soluble phenol substances, resulting in a consistent reduction in phytotoxicity after 36 days of colonisation. P. chrysosporium can be profitably used during compost maturation of mixtures of OMW and agricultural wastes (rich in lignocellulose compounds), so as to improve compost maturity and to reduce the phytotoxic effects of the phenols.

3. CONCLUSIONS OMW production is an environmental problem of great concern in countries where olive

oil production is an important economic activity. However, treatment of OMW is a complex problem that has not been satisfactorily resolved yet. Safe and economical disposal of OMW by effective bioremediation can result in significant reductions in COD, phenolic compounds and colour .

Different factors should be considered when selecting the valorisation method: the seasonality of olive oil production, the highly variable chemical composition of the waste, the investment required to perform the treatment, and the local laws. In recent years, many of the management solutions proposed for the valorisation of OMW have been aimed at a reduction in its phytotoxicity and for its re-use for the recycling of organic matter for agricultural purposes. Among these technologies, composting is one of the most promising for the transformation of this waste material into a valuable organic additive. Through the use of substrates of agricultural origin, inoculation of OMW with ligninolytic fungi can be a useful tool for the acceleration of humification and to improve the compost maturity. Moreover, the


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valorisation of OMW using yeast species has been shown to be suitable for aerobic biodegradation and detoxification of this OMW waste, while at the same time producing biomass and/or other valuable products, such as enzymes and organic acids.

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Chapter 9

METHODOLOGICAL APPROACHES FOR ASSESSING HUMAN HEALTH RISKS OF WASTE MANAGEMENT PLANTS. EXPERIENCES FROM CATALONIA (SPAIN)

Martí Nadal* and José L. Domingo

ABSTRACT

Because of the concern among the population, much attention has been paid in recent years on the impact that waste management facilities, and particularly incinerators, might have on the environment and the human health. As a consequence, the number of studies to evaluate the exposure to pollutants potentially released by waste treatment plants has notably increased. This book chapter presents a review of studies on human health risk assessment of waste management plants located in Catalonia (Spain). Different methodological approaches are presented, while a number of case-studies is summarized. Among them, environmental monitoring studies are, by large, the most frequently used, although biomonitoring and environmental modeling are also good alternatives. All they have been proven to be suitable complementary methods to assess the environmental and human health risks, as well as to evaluate the efficiency of new cleaning systems.

INTRODUCTION On the most crucial issues of modern societies is the disposal of waste, while

guaranteeing the environment and the human health. Municipal solid waste (MSW) is increasingly generated in big quantities, although its content may change along time. Moreover, concern is not only on MSW but also on other waste typologies such as hazardous waste (HW) and medical waste, whose generation volumes are lower but they may be highly toxic. The European Union has published different directives for waste management to

* Corresponding author: Phone: +34 977 759325; Fax: +34 977 759322; e-mail: [email protected]. Laboratory of

Toxicology and Environmental Health, IISPV, “Rovira i Virgili” University, Sant Llorenç 21, 43201 Reus, Catalonia, Spain

Martí Nadal and José L. Domingo

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protect the environment and the human health in waste treatment processes. These regulations are based on three principles: waste prevention, recycling and reuse, and finally, improvement of the final disposal. Among the different alternatives, incineration with energy recovery seems to be one of the best options. However, all waste management facilities in general, and incinerators in particular, have been traditionally affected by the NIMBY (Not In My Back Yard) syndrome (Pol et al., 2006; Schively, 2007). Thus, in many countries the potential health risks associated with stack emissions, especially those of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), have become a cause of great controversy and concern. However, other waste treatment facilities such as MSW landfills or composting plants have also been NIMBY-affected as they potentially release chemical and biological pollutants to the environment which may have an ultimate notable impact for the health of the population living nearby (US EPA, 1994; Chen and Kao, 2008).

Catalonia (NE of Spain) covers an approximate surface of 32,000 km2 and has a population of over 7 million inhabitants (data of 2009). With a similar tendency to other developed countries, in 2008 the mean amount of municipal solid waste (MSW) generated by the Catalan population was calculated in 1.59 kg/person·day. The treatment of MSW is done in different facilities, including landfills, incinerators and anaerobic digestion plants. Because of the public opposition to the sitting and permitting of MSW management plants, and particularly but not only incinerators, since mid-90s various studies have been performed in Catalonia to assess the environmental and human health risks of a number of facilities, as well as to evaluate the efficiency of new cleaning systems. Therefore, a huge amount of information is now available regarding the pollution state and the temporal trends of contamination near MSW and HW incinerators, together with other waste treatment plants. This book chapter presents a review of studies on human health risk assessment of Catalan waste management plants published in the literature. Different methodological approaches, which may be applied elsewhere, are presented, while a number of examples of each method are summarized.

HUMAN BIOMONITORING Biomonitoring (or biological monitoring) is the analytical measurement of biomarkers in

specified units of human tissues or body products (Albertini et al., 2006), generally called biomonitors. These represent an integration of the total exposure to specific chemicals from all routes of uptake and all sources, which are relevant making it an ideal instrument for risk assessment and risk management (Angerer et al., 2007). Data from biologic monitoring studies are more advantageous than other obtained through indirect methodologies, such as the environmental monitoring, particularly at the individual level. In fact, biomarkers are often used, when available, as a better substitute of environmental monitoring (Manno et al., 2009). Handicaps of this method are, for instance, that sampling is usually more difficult, as well as the complexity to discriminate among different sources of exposure. Although a varied number of biomonitors has been used to evaluate the human exposure to chemicals, blood is one of the most recurrent. However, there exist other alternatives, such as urine, hair, nails, breast milk, and adipose tissue, among others. The choice of a specific biomonitors depends basically on two main factors: a) physical-chemical and bioaccumulation properties

Methodological Approaches for Assessing Human Health Risks…

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of the target chemical; and b) simplicity to obtain samples. Bimonitoring has a fundamental role in occupational risk assessment, but is not limited to that, as it has been gaining an increasing interest to assess non-occupational exposure to environmental pollution.

Human biological monitoring studies have been largely performed worldwide to assess the occupational exposure and the health risks for workers of waste treatment plants, and particularly, waste incinerators (Linzalone and Bianchi, 2009). Since 1999, a continuous surveillance program of the occupational exposure in the hazardous waste incinerator (HWI) of Constantí (Tarragona County, Catalonia, Spain) is being carried out. Concentrations of a number of metals and organic substances, such as hexachlorobenzene, polychlorinated biphenyls (PCBs), PCDD/Fs, chlorophenols, and 1-hydroxypyre, in blood and urine samples are determined yearly. In the baseline study (1999), the body burden of the target chemicals was evaluated in individual samples from 28 volunteer participants (Domingo et al., 2001b). The pollutant exposure of workers in specific workplaces was studied in detail. In subsequent studies, composite samples were obtained to register temporal trends of pollutants in the same biomonitors (Schuhmacher et al., 2002a; Agramunt et al., 2003). According to the results from the most recent campaign of the surveillance program (2007), the HWI do not show evident signs of occupational exposure to a number of metals and organic substances, with values similar or even lower than the respective baseline levels. In fact, a significant reduction of PCDD/Fs in plasma of plant workers was observed (from 26.7 pg I-TEQ/g lipid to 2.5 pg I-TEQ/g lipid after 8 years of regular operations). This decrease would be in agreement with the notable reduction in the dietary intake of PCDD/Fs recently noted for the population of the same area (Martí-Cid et al., 2008).

Complementarily to the biomonitoring of workers of the HWI of Constantí, a wide biomonitoring program to assess the non-occupational exposure for the population living nearby was initiated three years before the plant started regular operations (Schuhmacher et al., 1999a,b,c). This program was mainly focused on determining the human health risks derived from the emissions of the HWI through both biological and environmental monitoring. Plasma, breast milk and adipose tissue samples from individuals living in the vicinity of the facility were used as monitors of PCDD/Fs. In turn, blood, human hair and other human tissues (brain, bone, kidney, liver, and lung autopsy samples) were collected to analyze the intake of heavy metals. In 2002, after approximately 3 years of regular operations, a new survey was again carried out using samples of the same biological monitors. A significant reduction of PCDD/F levels in plasma, breast milk and adipose tissue was noted (Schuhmacher et al., 2004c; Schuhmacher et al., 2004b; Agramunt et al., 2005), probably due to a lower ingestion of dioxins and furans through food consumption (Bocio and Domingo, 2005a). Metal concentration in the body burdens also decreased (Bocio et al., 2005b). The biomonitoring is still continuing and, in 2007, new human biological samples were collected from the local population (Ferré-Huguet et al., 2009). The results of the last campaign indicated that the emissions of pollutants from the HWI should not mean a significant additional exposure for the people living near the facility (Nadal et al., 2008). The use of complementary monitors revealed the suitability of plasma as a better biological indicator with respect to others (Nadal et al., 2009b). In recent years, only another biomonitoring study to evaluate the occupational and non-occupational exposures to PCDD/Fs and PCBs has been performed. This investigation was aimed at assessing the impact of the municipal solid waste incinerator (MSWI) of Mataró (Barcelona, Spain) on the human health of the population (Gonzalez et al., 1998). Since 1995, concentrations of the abovementioned pollutants have


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been analyzed in blood samples from workers as well as from subjects living near and far the incineration plant (Gonzalez et al., 2000). The results of the 5th phase of the study showed a reduction of the PCDD/F levels in plasma in the period 1999-2005, in contrast with the slight increasing tendency observed between 1995 and 1999. The most updated results were actually lower than those obtained in the baseline survey.

ENVIRONMENTAL MONITORING As stated, sampling is one of the most difficult issues when carrying out biomonitoring

studies. In order to solve that problem, the analysis of environmental monitors may be a good alternative. In fact, the easiness to get environmental samples has meant that this kind of investigations has been very frequently applied to assess the environmental impact of not only waste management plants, but also other industrial facilities, densely-populated areas, etc. Among the different possibilities of environmental monitors, soils have been the most widely used, although levels in air, vegetation and sediments are also usually studied. Soil and herbage have been determined to be good long- and short-term environmental monitors, respectively, while air sampling is ideal to represent point atmospheric conditions (Nadal et al., 2009a). Further, the pollutant concentrations in environmental monitors may be used to indirectly determine the exposure to chemicals through various pathways such as soil ingestion, dermal absorption and air inhalation to, ultimately, assess the human health risks. Because of the concern of the population and the local authorities, much attention has been paid on waste incinerators. The presence of a MSWI and a HWI in the area of Tarragona (Catalonia) has led to obtain a large amount of data regarding the environmental concentrations of some pollutants potentially emitted by both facilities, and very particularly PCDD/Fs and metals in soil and vegetation. The first environmental surveillance program of an incineration plant in Catalonia was done in mid-90s. In 1996, a wide surveillance program was initiated to provide information on the environmental impact of the MSWI of Tarragona (Schuhmacher et al., 1997b). Soil and vegetation samples were collected before (1996-1997) and after (1999) the implementation of new cleaning measurements (Llobet et al., 1999; Schuhmacher et al., 1999d). In 2002, a second campaign was initiated. During a period of 4 years (2002-2005), soil and vegetation samples were periodically collected and analysis of the levels of metals and PCDD/Fs was performed. According to the results obtained, it was concluded that no significant health risks might be expected for the population living in the neighborhood of the facility due to stack emissions (Mari et al., 2007a). However, a raise of the concentration of some specific PCDD/F congeners was noted. A detailed study of the results associated that episode with a forest fire occurred in the zone immediately before sampling, evidencing the incidence of other potential sources in the area. This reasserted the necessity to make a drift in the environmental surveillance program to discriminate the influence of the MSWI under evaluation with respect to these other sources in the same zone (Vilavert et al., 2009a). Therefore, a change in the monitoring program was implemented by including the monitoring of ambient air samples through active and passive sampling devices, together with those of soil and vegetation. The preliminary results of the on-going program indicate that the environmental impact of the MSWI of Tarragona is not significant, with relatively low concentrations in comparison with other areas under the influence of emissions


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from waste incinerators. Reported immission PCDD/F levels were 12.04 and 15.21 fg WHO-TEQ/m3 in 2007 and 2008, respectively.

In addition to the occupational and the non-occupational exposure surveillance programs of the HWI of Constantí, since 1996 a large environmental monitoring study has been being developed to assure that the potential stack emissions of PCDD/Fs and metals would not mean a health risk for the local population. In 1996-1998, a pre-operational survey was done by analyzing the levels of those chemicals in soil and vegetation from 40 different locations around the plant (Schuhmacher et al., 1997a; Llobet et al., 2000; Schuhmacher et al., 2002b). Since then, the annual variation of the levels of PCDD/Fs and metals in soil and/or vegetation are investigated. Subsequently, the risks of the local population derived from an exposure to PCDD/Fs and metals are also being controlled (Ferré-Huguet et al., 2006). The most recent investigations show that the HWI do not either mean additional significant risks for the health of the individuals living in the vicinity of the facility (Ferré-Huguet et al., 2007; Mari et al., 2007b).

From 1975 to 2004, a MSWI was operating in Montcada (Barcelona, Catalonia, Spain). In 1999, measures were taken to reduce notably PCDD/F emissions and a modernization of the flue gas cleaning system was carried out. An acid gas (HCl/SO2) and metal emission limit equipment was installed and an active-carbon adsorption filter was added to the fabric filter. As a consequence, PCDD/F emissions dropped, on average, to 0.086 ng I-TEQ/Nm3, which is below the legal limit of 0.1 ng I-TEQ/Nm3 (Schuhmacher and Domingo, 2006a). To establish the environmental levels in the area under potential influence of the MSWI, as well as to assess the suitability of new filtering measures, metals and PCDD/Fs were analyzed in soil and herbage samples in 1996-1998 and 2000-2000, before and after the introduction of the air-cleaning device, respectively (Meneses et al., 1999; Domingo et al., 2001a). Additionally, airborne PCDD/F levels were determined by means of passive air devices (Schuhmacher et al., 2006b). A substantial and continuous decrease of the PCDD/F levels in vegetation through time was noted. However, from an accurate inspection of the PCDD/F congener profiles, it was also concluded that emissions of PCDD/Fs were neither the only nor the main responsible for the presence of these pollutants in soil and vegetation samples collected in the area under direct influence of the plant (Domingo et al., 2000a), while other PCDD/F emission sources in the same area seemed to have a notable environmental impact (Nadal et al., 2002). Although the results of that study indicated that the human health risks of PCDD/Fs for the population living in the vicinity of the facility after introduction of a modern technology were in fact negligible in comparison with the dietary exposure, the population of Montcada maintained the perception of health risks due to the previous situation. Therefore, local authorities decided to cease the activities of the MSWI of Montcada, which was definitively closed in September 2004 (Schuhmacher et al., 2006a).

Environmental monitoring studies have also been performed in the vicinity of other waste incinerators located in Barcelona County. Since 1975, a MSWI has been operating in Sant Adrià del Besòs (Barcelona). Between 1998 and 1999, an environmental monitoring study was carried out to determine the state of pollution in the surroundings of the plant. PCDD/F levels in soils and vegetations were monitored, and the temporal trend was established (Domingo et al., 2000b; Schuhmacher et al., 2000). Just after the 1999 collection, an adaptation to the EU legislation on pollutant emissions from the stack was carried out in this facility (Domingo et al., 2002b). In 2000 and 2001, new samples of the same monitors were collected and the PCDD/F levels were again determined. A significant (30%) decrease was


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found in the levels of PCDD/F in herbage samples collected in the vicinity of the MSWI, as a result of the technical improvements of the incinerator (Domingo et al., 2002a). A few years later (2005-2006), a new monitoring campaign was executed in the same area of Sant Adrià del Besòs (Mari et al., 2008a). Because of the increasing urbanization, soil and vegetation samples had to be changed by samples of ambient air. Active air devices were used to examine the concentrations of PCDD/Fs, PCBs and polychlorinated naphthalenes (PCNs) as well as a number of metals around the MSWI and in a background/control area. These data were used to validate the suitability of passive samplers to determine persistent organic pollutants (POPs) concentrations in air in areas with various potential emission sources (Mari et al., 2008b). On the other hand, an environmental monitoring survey was initiated near the MSWI of Mataró (Barcelona, Catalonia, Spain) complementarily to the biomonitoring study which is being carried out for workers and non-occupationally exposed populations. Air and soil concentrations of PCDD/Fs and metals were analyzed as a first step to evaluate the health risks for the population living near and far the incineration plant [unpublished results].

Although incinerators are the waste management facilities which have traditionally received more pressure, the shift in the model of the treatment of waste, as well as the drastic reduction of the influence of MSWIs on the state of pollution of specific zones, has given place to implement monitoring programs to other waste treatment facilities. In recent years, the Autonomous Government of Catalonia is reinforcing new methodologies to reduce the percentage of MSW deposited on landfills. In the metropolitan area of Barcelona, various MSW management facilities (known as Ecoparcs) are being built. Three facilities are currently already operative. Ecoparcs are set up to get a valorization of energy and materials through two operation lines to treat the MSW organic fraction, and the remaining fraction. In spite of the advantages of these systems, human health risks due to the release of chemical and biological agents may be of importance from the point of view of workers and people living around (Domingo and Nadal, 2009). Because of that, new investigations have been done in Ecoparcs, as well as in composting and mechanical-biological treatment (MBT) plants. Very recently, the occupational exposure to chemical and biological agents was evaluated for workers of the Ecoparc-2 of Montcada i Reixac (Barcelona, Catalonia, Spain). The total concentrations of volatile organic compounds (VOCs) as well as bacteria and fungi (at 25 °C and 37 °C), including Aspergillus fumigatus, were determined on a 3-month basis in various areas of the composting plant (Nadal et al., 2009c). According to the results, a series of recommendations was given to prevent the exposure to biological and chemical agents, such as the use of P3 filter masks and gloves, and the humectation of waste and the installation of biofilters. Other studies consider the analysis of VOCs and bioaerosols in ambient air around new composting facilities. A new MBT plant is planned to be constructed adjacently to the MSWI of Tarragona. In order to evaluate its potential impact and to differentiate the impacts of MSWI from those of the MBT when the latter is operative, a pre-operational survey was initiated by determining the concentrations of VOCs and some microbiological pollutants in airborne samples around the MSWI (Vilavert et al., 2009b). The compilation of these data, together with those concerning to PCDD/Fs and heavy metals, will allow to carry out a complete human health risk assessment in the area under study.

Although landfills are only considered as the last alternative for waste management, some processes such as incineration or sintering, continue to generate a residual fraction which cannot be valorized and has to be safely deposited in hazardous waste landfills (HWLs) due to its toxic potential. Therefore, environmental monitoring programs are also suitable to


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assess the impact for the human health of these facilities. Since 1984, a class III hazardous waste landfill (HWL) has been operating in Castellolí (Barcelona Province, Catalonia). In 1998, it started to receive hazardous input materials such as municipal waste incinerator fly ashes (characterized by their high content of heavy metals and PCDD/Fs), asbestos, as well as other inert wastes. Although the HWL operates according to the regulation, the population living nearby is worried about the potential release of pollutants into air, water, and soil, as well as about the consequences that those eventual discharges may have on the ecosystems and the human health. Because of that concern, since 2007, the concentrations of metals and PCDD/Fs are being monitored in air and soil samples from the landfill and close towns. In the first campaign, metal and PCDD/F levels were relatively low in air and soil samples (Mari et al., 2009), indicating that it is highly unlikely that there are any additional non-carcinogenic and carcinogenic risks for the population living near the HWL.

ENVIRONMENTAL MODELING When no information from biological and environmental monitoring is available, the

application of fate and transport models may be useful to get estimative values of pollutant concentrations in the environment. These can be estimated using an air dispersion model, which simulate the atmospheric dispersion using meteorological and topographic information of the area under evaluation (Meneses et al., 2004). Air dispersion modeling has been executed to assess the environmental impact of waste management plants, with a special emphasis on waste incinerators (Cangialosi et al., 2008). Models are fed with site-specific information such as stack emission rates, meteorological data, stack parameters, and cartographic data (Schuhmacher et al., 2004a). In addition, several models of uptake of organic chemicals by plants and soils have been reported in the literature (Meneses et al., 2002).

In 2000, an investigation was conducted near the MSWI of Montcada i Reixac (Barcelona, Spain) to establish the potential reduction on human health risks as a consequence of the adaptation to the EU legislation on pollutant emissions from the MSWI stack (Meneses et al., 2004). Predicted results were obtained by means of a simple-compartment-multimedia model (air-soil-vegetation model), and compared with analytically measured PCDD/F concentrations in soils and vegetation to validate the model. Emissions of PCDD/Fs decreased, on average, from 111.39 ng I-TEQ/Nm3 to 0.036 ng I-TEQ/Nm3, after the installation of the new cleaning gas system. The modeling results indicated that the reduction had not been as great as it could be expected according to the very pronounced decreases in PCDD/F emissions from the stack. The application of atmospheric dispersion models of pollutants has been executed in other MSWIs of Catalonia, such as that of Campdorà (Girona). Recently, an exhaustive study to determine the temporal trends of air pollutant concentrations in ambient air around that facility was performed (Serra and Ubach, 2008). Immission levels of several inorganic gasses, such as NO2, SO2, CO and HCl, as well as particulate matter (PM) were modeled through time. The authors concluded that the progressive installation of methodological improvements resulted in a substantial reduction of the levels of those contaminants around the incineration plant.


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CONCLUSION An important number of human health risk assessment studies have been performed and

are being performed in Catalonia in recent years. Most investigations have been aimed at evaluating the risks of occupational and non-occupational exposures to chemicals, with a special emphasis on PCDD/Fs and heavy metals potentially released by incinerators. Additionally, the influence of other facilities such as landfills and MBT plants for the surrounding environment has also been studied. Examples of different approaches have been presented, highlighting their advantages and inconveniences. Human health risk assessment can be done by applying different complementary tools according to the needs of decision-making stakeholders. Because of the easiness in sampling and chemical analysis, the most frequently used method is, by large, the environmental monitoring, while biomonitoring and environmental modeling are not so usually applied. However, to the best of our knowledge, no epidemiological investigations have been carried out in Catalonia to evaluate the incidence of waste management plants on human health, although observational studies are sometimes used (Giusti, 2009). It must be taken into account that the difficulty of developing reasonably good epidemiological investigations is an important disadvantage when assessing human health risks derived from the exposure to chemicals, which may otherwise be successfully covered by other methods such as biological and environmental monitoring.

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Domingo, JL; Bocio, A; Nadal, M; Schuhmacher, M; Llobet, JM. Monitoring dioxins and furans in the vicinity of an old municipal waste incinerator after pronounced reductions of the atmospheric emissions. Journal of Environmental Monitoring 2002a, 4, 395-399.

Domingo, JL; Schuhmacher, M; Müller, L; Rivera, J; Granero, S; Llobet, JM. Evaluating the environmental impact of an old municipal waste incinerator: PCDD/F levels in soil and vegetation samples. Journal of Hazardous Materials 2000b, 76, 1-12.

Domingo, JL; Schuhmacher, M; Agramunt, MC; Llobet, JM; Rivera, J; Müller, L. PCDD/F levels in the neighbourhood of a municipal solid waste incinerator after introduction of technical improvements in the facility. Environment International 2002b, 28, 19-27.

Ferré-Huguet, N; Nadal, M; Schuhmacher, M; Domingo, JL. Environmental impact and human health risks of polychlorinated dibenzo-p-dioxins and dibenzofurans in the vicinity of a new hazardous waste incinerator: A case study. Environmental Science and Technology 2006, 40, 61-66.

Ferré-Huguet, N; Nadal, M; Schuhmacher, M; Domingo, JL. Monitoring metals in blood and hair of the population living near a hazardous waste incinerator: Temporal trend. Biological Trace Element Research 2009, 128, 191-199.

Ferré-Huguet, N; Nadal, M; Mari, M; Schuhmacher, M; Borrajo, MA; Domingo, JL. Monitoring metals near a hazardous waste incinerator. Temporal trend in soils and herbage. Bulletin of Environmental Contamination and Toxicology 2007, 79, 130-134.

Giusti, L. A review of waste management practices and their impact on human health. Waste Management 2009, 29, 2227-2239.

Gonzalez, CA; Kogevinas, M; Huici, A; Gadea, E; Ladona, M; Bosch, A, et al. Blood levels of Polychlorinated dibenzodioxins, Polychlorinated dibenzofurans and Polychlorinated biphenyls in the general population of a Spanish Mediterranean city. Chemosphere 1998, 36, 419-426.

Gonzalez, CA; Kogevinas, M; Gadea, E; Huici, A; Bosch, A; Bleda, MJ, et al. Biomonitoring study of people living near or working at a municipal solid-waste incinerator before and after two years of operation. Archives of Environmental Health 2000, 55, 259-267.

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232

Llobet, JM; Schuhmacher, M; Domingo, JL. Observations on metal trends in soil and vegetation samples collected in the vicinity of a hazardous waste incinerator under construction (1996-1998). Toxicological and Environmental Chemistry 2000, 77, 119-129.

Llobet, JM; Granero, S; Schuhmacher, M; Domingo, JL. Temporal variation in metal concentrations in soils and vegetation in the vicinity of a municipal solid waste incinerator. Toxicological and Environmental Chemistry 1999, 71, 63-73.

Manno, M; Viau, C; Cocker, J; Colosio, C; Lowry, L; Mutti, A, et al. Biomonitoring for occupational health risk assessment (BOHRA). Toxicology Letters 2009, , in press,

Mari, M; Nadal, M; Schuhmacher, M; Domingo, JL. Monitoring PCDD/Fs, PCBs and metals in the ambient air of an industrial area of Catalonia, Spain. Chemosphere 2008a, 73, 990-998.

Mari, M; Schuhmacher, M; Feliubadaló, J; Domingo, JL. Air concentrations of PCDD/Fs, PCBs and PCNs using active and passive air samplers. Chemosphere 2008b, 70, 1637-1643.

Mari, M; Nadal, M; Schuhmacher, M; Domingo, JL. Exposure to heavy metals and PCDD/Fs by the population living in the vicinity of a hazardous waste landfill in Catalonia, Spain: Health risk assessment. Environment International 2009, 35, 1034-1039.

Mari, M; Ferré-Huguet, N; Nadal, M; Schuhmacher, M; Domingo, JL. Temporal trends in metal concentrations in soils and herbage collected near a municipal waste incinerator: Human health risks. Hum Ecol Risk Assess 2007a, 13, 457-472.

Mari, M; Nadal, M; Ferré-Huguet, N; Schuhmacher, M; Borrajo, MA; Domingo, JL. Monitoring PCDD/Fs in soil and herbage samples collected near a hazardous waste incinerator: Health risks for the population living nearby. Human and Ecological Risk Assessment 2007b, 13, 1255-1270.

Martí-Cid, R; Bocio, A; Domingo, JL. Dietary exposure to PCDD/PCDFs by individuals living near a hazardous waste incinerator in Catalonia, Spain: temporal trend. Chemosphere 2008, 70, 1588-1595.

Meneses, M; Schuhmacher, M; Domingo, JL. A design of two simple models to predict PCDD/F concentrations in vegetation and soils. Chemosphere 2002, 46, 1393-1402.

Meneses, M; Schuhmacher, M; Domingo, JL. Health risk assessment of emissions of dioxins and furans from a municipal waste incinerator: Comparison with other emission sources. Environment International 2004, 30, 481-489.

Meneses, M; Llobet, JM; Granero, S; Schuhmacher, M; Domingo, JL. Monitoring metals in the vicinity of a municipal waste incinerator: Temporal variation in soils and vegetation. Science of the Total Environment 1999, 226, 157-164.

Nadal, M; Agramunt, MC; Schuhmacher, M; Domingo, JL. PCDD/PCDF congener profiles in soil and herbage samples collected in the vicinity of a municipal waste incinerator before and after pronounced reductions of PCDD/PCDF emissions from the facility. Chemosphere 2002, 49, 153-159.

Nadal, M; Mari, M; Schuhmacher, M; Domingo, JL. Multi-compartmental environmental surveillance of a petrochemical area: Levels of micropollutants. Environment International 2009a, 35, 227-235.

Nadal, M; Domingo, JL; García, F; Schuhmacher, M. Levels of PCDD/F in adipose tissue on non-occupationally exposed subjects living near a hazardous waste incinerator in Catalonia, Spain. Chemosphere 2009b, 74, 1471-1476.


233

Nadal, M; Perell, G; Schuhmacher, M; Cid, J; Domingo, JL. Concentrations of PCDD/PCDFs in plasma of subjects living in the vicinity of a hazardous waste incinerator: Follow-up and modeling validation. Chemosphere 2008, 73, 901-906.

Nadal, M; Inza, I; Schuhmacher, M; Figueras, MJ; Domingo, JL. Health risks of the occupational exposure to microbiological and chemical pollutants in a municipal waste organic fraction treatment plant. International Journal of Hygiene and Environmental Health 2009c,

Pol, E; Di Masso, A; Castrechini, A; Bonet, MR; Vidal, T. Psychological parameters to understand and manage the NIMBY effect. Revue Européenne de Psychologie Appliquée/European Review of Applied Psychology 2006, 56, 43-51.

Schively, C. Understanding the NIMBY and LULU Phenomena: Reassessing Our Knowledge Base and Informing Future Research. Journal of Planning Literature 2007, 21, 255-266.

Schuhmacher, M; Domingo, JL. Long-term study of environmental levels of dioxins and furans in the vicinity of a municipal solid waste incinerator. Environment International 2006a, 32, 397-404.

Schuhmacher, M; Domingo, JL; Garreta, J. Pollutants emitted by a cement plant: Health risks for the population living in the neighborhood. Environmental Research 2004a, 95, 198-206.

Schuhmacher, M; Jones, KC; Domingo, JL. Air-vegetation transfer of PCDD/PCDFs: An assessment of field data and implications for modeling. Environmental Pollution 2006b, 142, 143-150.

Schuhmacher, M; Domingo, JL; Kiviranta, H; Vartiainen, T. Monitoring dioxins and furans in a population living near a hazardous waste incinerator: Levels in breast milk. Chemosphere 2004b, 57, 43-49.

Schuhmacher, M; Domingo, JL; Hagberg, J; Lindström, G. PCDD/F and non-ortho PCB concentrations in adipose tissue of individuals living in the vicinity of a hazardous waste incinerator. Chemosphere 2004c, 57, 357-364.

Schuhmacher, M; Granero, S; Llobet, JM; De Kok, HAM; Domingo, JL. Assessment of baseline levels of PCDD/F in soils in the neighbourhood of a new hazardous waste incinerator in Catalonia, Spain. Chemosphere 1997a, 35, 1947-1958.

Schuhmacher, M; Domingo, JL; Llobet, JM; Müller, L; Jager, J. Levels of PCDDs and PCDFs in grasses and weeds collected near a municipal solid waste incinerator. Science of the Total Environment 1997b, 201, 53-62.

Schuhmacher, M; Domingo, JL; Llobet, JM; Kiviranta, H; Vartiainen, T. PCDD/F concentrations in milk of nonoccupationally exposed women living in southern Catalonia, Spain. Chemosphere 1999a, 38, 995-1004.

Schuhmacher, M; Domingo, JL; Llobet, JM; Lindström, G; Wingfors, H. Dioxin and dibenzofuran concentrations in blood of a general population from Tarragona, Spain. Chemosphere 1999b, 38, 1123-1133.

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Schuhmacher, M; Domingo, JL; Agramunt, MC; Bocio, A; Müller, L. Biological monitoring of metals and organic substances in hazardous-waste incineration workers. International Archives of Occupational and Environmental Health 2002a, 75, 500-506.


234

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Vilavert, L; Nadal, M; Mari, M; Schuhmacher, M; Domingo, JL. Modification of an environmental surveillance program to monitor PCDD/Fs and metals around a municipal solid waste incinerator. Journal of Environmental Science and Health, Part A: Toxic/Hazardous Substance & Environmental Engineering 2009a, 44, 1343-1352

Vilavert, L; Nadal, M; Inza, I; Figueras, MJ; Domingo, JL. Baseline levels of bioaerosols and volatile organic compounds around a municipal waste incinerator prior to the construction of a mechanical-biological treatment plant. Waste Management 2009b, 29, 2454-2461.

INDEX

A

acid, 27, 137, 140, 141, 144, 145, 157, 170, 206, 209, 211, 212, 219, 227

activated carbon, 26, 137, 140, 141, 143, 144, 145, 148, 155, 156, 157, 158, 170, 183, 211, 215

active site, 143 adaptation, 209, 227, 229 adipose, 224, 225, 232, 233 adipose tissue, 224, 225, 232, 233 adsorption, 137, 139, 141, 142, 143, 144, 145, 146,

148, 149, 150, 151, 152, 155, 157, 158, 159, 208, 227

adsorption isotherms, 143 aerobic bacteria, 208, 209, 216 aesthetics, 34 Afghanistan, 73 age, 32, 129, 192 agricultural market, 84 agricultural sector, 85, 99 agriculture, 84, 85, 97, 99 air emissions, 2, 23, 26, 230 alcohol, 92 alcohol production, 92 alternatives, 109, 223, 224 aluminium, 13, 18, 43, 63, 157 ambient air, 226, 228, 229, 232 anaerobic digesters, 162 anaerobic sludge, 211, 217 analytical framework, 101 APC, 4, 13, 18, 25, 28, 161, 179, 183, 187 aqueous solutions, 157, 158 Argentina, 204 Aristotle, 81 aromatic compounds, 216, 221 asbestos, 65, 229

ash, 4, 13, 18, 23, 25, 35, 45, 74, 139, 170, 172, 173, 176, 178, 185, 192, 193, 198, 199, 200, 201

Asia, 191 Asian countries, 99, 136 Aspergillus terreus, 210, 212, 217 assessment, 2, 6, 10, 13, 19, 21, 30, 31, 32, 94, 100,

102, 106, 110, 112, 113, 117, 118, 217, 225, 230, 233

atoms, 143 Australia, 69, 104, 204 Austria, 166, 174 authority, 121, 125, 126, 128, 133, 134 authors, 85, 89, 90, 91, 92, 95, 96, 99, 100, 101, 102,

110, 207, 229 autopsy, 225, 230 availability, 82, 84, 85, 91, 92, 93, 95, 152, 178 awareness, vii, 133

B

bacteria, 209, 210, 211, 212, 220, 228 bacterial strains, 216 barley, 207, 213 barriers, 28, 87, 99, 116, 117 batteries, 65, 68 behavior, 148, 192, 199 Belgium, 74, 114, 166, 177, 178 bicarbonate, 140 binary decision, 108 binding, 87, 143 bioaccumulation, 224 biodegradability, 12 biodegradable materials, 45 biodegradation, 20, 21, 75, 206, 209, 210, 211, 213,

214, 216, 221 biodiesel, 84, 92 bioelectricity, 110

Index

236

bioenergy, 32, 85, 94, 99, 101, 102, 108, 109, 110, 112, 113, 115, 116, 117, 118, 119, 120

biofuel, 84, 88, 89, 99, 120 biological activity, 3, 12, 217 biological processes, 203 biomarkers, 224 biomass, 24, 27, 29, 81, 82, 83, 84, 85, 86, 87, 88,

89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 106, 107, 108, 109, 110, 111, 112, 113, 115, 116, 117, 118, 119, 120, 158, 167, 172, 173, 176, 177, 210, 214

biomaterials, 86 biomonitoring, 223, 225, 226, 228, 230, 231 bioremediation, 209, 210, 213 blood, 138, 224, 225, 231, 233 bone, 37, 173, 225 Botswana, 122, 134, 135 brain, 225 Brazil, 134, 135 breast milk, 224, 225, 233 breeding, 74, 77 Brno, 76, 77 burn, 161, 162, 163, 168, 178, 179, 182, 185, 186,

187 burning, 26, 97, 125, 137, 167, 170, 182, 186 buyer, 133 by-products, 87, 101, 113, 114, 205, 209, 221

C

calcium, 191, 195, 196 calcium carbonate, 191 Cambodia, 135 Canada, 69, 101, 117, 188 candidates, 211 carbon, 16, 17, 18, 23, 86, 88, 90, 97, 115, 137, 143,

145, 155, 156, 157, 158, 172, 183, 185, 191, 206, 209, 211, 212, 227

carbon dioxide, 23, 88, 97, 184, 185, 191, 211, 212 carbon monoxide, 90 carrier, 86 case study, 30, 32, 95, 96, 104, 109, 115, 118, 119,

137, 163, 186, 218, 230, 231 case-studies, 223 cast, 36, 192 categorization, 161 cellulose, 3 cellulose fibre, 3 ceramic, 192, 194 chemical properties, 40, 207 China, 36, 119 chlorine, 176, 178, 179, 183 chromium, 137, 138, 139, 145, 157, 158

City, 25, 29, 76, 79, 125, 127 classification, 105, 106, 192, 193, 198 Clean Air Act, 25 cleaning, 36, 37, 40, 65, 66, 166, 170, 223, 224, 226,

227, 229 climate change, 2, 3, 6, 7, 9, 10, 82, 86, 119 CO2, 5, 6, 7, 8, 9, 13, 17, 18, 19, 21, 82, 84, 85, 86,

88, 97, 102, 112, 172, 176, 183, 185, 191, 192 coagulation, 208, 217, 218 coal, 4, 13, 14, 18, 19, 23, 25, 26, 45, 82, 86, 94,

100, 109, 137, 139, 161, 162, 177, 178, 182, 183, 188, 191, 192

combustion, 2, 4, 7, 12, 13, 14, 17, 18, 22, 23, 25, 40, 50, 71, 74, 77, 88, 90, 92, 96, 97, 102, 108, 113, 114, 118, 139, 167, 168, 170, 171, 172, 174, 177, 178, 182, 183, 184, 185, 186, 187, 192, 208

commodity, 57, 84 community, 23, 25, 86, 104, 106, 207 compatibility, 2, 31 competition, 82, 85, 100, 118, 134 competitiveness, 85, 113 complexity, 76, 82, 93, 95, 97, 110, 206, 224 compliance, 34, 82 components, 35, 41, 49, 57, 72, 77, 81, 83, 89, 101,

122, 129 composition, 4, 13, 15, 16, 17, 31, 33, 34, 35, 41, 43,

44, 45, 48, 77, 78, 91, 172, 174, 175, 176, 179, 180, 181, 183, 194, 196, 198, 205, 206, 213

compost, 4, 35, 40, 69, 74, 75, 77, 162, 213, 214, 219, 220, 221

composting, 1, 3, 10, 12, 17, 21, 24, 28, 36, 37, 38, 41, 45, 49, 71, 74, 75, 138, 161, 162, 173, 174, 212, 213, 214, 215, 216, 217, 219, 221, 224, 228, 231

compounds, 40, 65, 138, 183, 192, 203, 205, 206, 208, 209, 210, 212, 213, 214, 215, 217, 218, 221

computing, 101 concentration, 33, 97, 137, 142, 143, 144, 145, 148,

149, 150, 151, 152, 154, 155, 157, 183, 221, 225, 226

concrete, 197, 198, 200, 201 configuration, 3, 4, 10, 83, 99, 109, 182 conformity, 200, 201 consensus, 121, 122, 124 conservation, vii construction, 25, 35, 36, 86, 108, 125, 138, 174, 177,

180, 181, 182, 184, 191, 200, 232, 234 consultants, vii consumers, 82, 99, 101, 162, 179, 184, 185 consumption, 5, 17, 18, 32, 41, 76, 84, 96, 101, 114,

162, 163, 225 contaminant, 137, 157, 234 contamination, 35, 38, 72, 74, 77, 126, 224

Index

237

control, 103, 110, 128, 168, 170, 212, 213, 228 conversion, 18, 82, 84, 86, 89, 90, 91, 92, 94, 96, 97,

98, 99, 100, 102, 103, 104, 106, 107, 108, 109, 110, 117, 118, 120, 177, 211

cooling, 110, 170, 183, 212 corn, 89, 104, 111, 119 corrosion, 168, 179, 196 cost accounting, 30 cost saving, 2, 85, 95 cost-benefit analysis, 102 costs, 21, 40, 85, 89, 90, 91, 92, 93, 94, 95, 99, 100,

101, 102, 104, 108, 109, 111, 112, 113, 117, 118, 155, 156, 208

cotton, 89, 91, 95, 101, 103, 104, 108, 109, 115, 119, 213

covering, 85, 123, 184 Croatia, 205 crop production, 213 crops, 24, 82, 83, 84, 85, 87, 89, 92, 100, 104, 111,

115, 207 crystalline, 195, 199, 200 cultivation, 139, 204, 205 curing, 192, 196, 197, 198, 199, 200 customers, 85, 109 Czech Republic, 34, 41, 42, 43, 44, 45, 47, 48, 56,

66, 68, 74, 77, 78, 79, 166

D

data collection, 124 ecision making, 33, 48, 98, 100 decision-making process, 81, 83, 97, 112 decisions, 21, 84, 88, 96, 97, 98, 99, 103, 104, 105,

106, 110, 112, 123 decomposition, 40, 50, 90, 97, 208 definition, 12, 24, 33, 34 degradation, 3, 12, 20, 75, 82, 206, 208, 209, 210,

212, 213, 214, 215, 217, 218, 219, 221 delivery, 103, 108, 109, 113, 116, 117, 118, 125, 133 Denmark, 29, 166, 177, 188 density, 89, 94, 128, 173, 176, 206 Department of Agriculture, 116 Department of Energy, 28 desorption, 137, 145, 157 developed countries, 28, 38, 69, 73, 86, 167, 224 developed nations, 84 developing countries, vii, 28, 31, 84, 122, 123, 135,

136, 155 developmental process, vii dibenzo-p-dioxins, 224, 230, 231 dietary intake, 225 digestion, 12, 31, 174, 208, 209, 211, 212, 215, 216,

217, 218, 219, 224

dioxin, 26, 170, 183 directives, 34, 86, 87, 223 discharges, 207, 229 discrimination, 128 distilled water, 140, 141 distribution, 18, 93, 100, 101, 102, 103, 119, 120,

129, 194, 195 district heating, 74, 94, 95, 101, 103, 108, 109, 118,

178 diversification, 84, 122, 134 diversity, vii, 85 division, 73, 79, 194, 197 dry matter, 173, 177 drying, 2, 3, 4, 7, 12, 17, 20, 28, 48, 90, 140, 141,

156, 174, 181 dumping, 36, 37, 68, 138

E

earnings, 130, 133, 134 East Asia, 117 Eastern Europe, 120 economic activity, 213 economic development, 85, 138, 191 economic efficiency, 108 economic evaluation, 102, 108 economic growth, 48, 162, 185 economics, 48, 95, 99, 110, 135 ecosystem, 139 EDSS, 101, 102, 110 EEA, 18, 29, 187 effluent, 137, 139, 143, 148, 149, 209, 212 effluents, 203, 215, 220 electricity, 2, 3, 4, 5, 6, 7, 8, 9, 11, 13, 18, 22, 23, 24,

25, 27, 35, 49, 82, 85, 86, 87, 88, 90, 92, 94, 99, 102, 104, 110, 114, 115, 162, 163, 165, 166, 167, 176, 179, 184, 185, 186, 187

electroplating, 157, 158 emission, 1, 2, 3, 5, 7, 8, 9, 10, 11, 16, 17, 18, 19, 20,

26, 27, 31, 38, 40, 82, 87, 88, 114, 162, 170, 171, 172, 176, 192, 227, 228, 229, 232

employment, 84, 85, 122, 129, 134 energy consumption, 85, 90, 94, 103, 109, 204 energy density, 94 energy efficiency, 88, 167 energy recovery, 1, 2, 3, 6, 7, 9, 12, 18, 20, 23, 29,

31, 76, 88, 161, 162, 165, 168, 172, 185, 186, 208, 224

energy supply, 82, 84, 85, 86, 92, 101, 108, 112, 114, 115, 117, 119

England, v, 1, 2, 3, 6, 9, 10, 28, 29, 31, 38 entrepreneurs, vii, 122, 124

Index

238

environment, vii, 2, 25, 29, 32, 33, 34, 37, 40, 41, 43, 48, 79, 82, 83, 85, 88, 96, 97, 98, 106, 114, 128, 129, 134, 135, 138, 139, 145, 162, 185, 188, 191, 207, 217, 220, 223, 229, 230

environmental effects, 123 environmental impact, 2, 21, 25, 27, 32, 33, 39, 76,

83, 96, 97, 102, 103, 106, 226, 227, 229, 231 environmental issues, 48 environmental protection, 87 Environmental Protection Agency, 28, 79, 234 environmental standards, 102 enzymes, 210, 214 EPA, 2, 24, 25, 26, 27, 28, 32, 41, 79, 224, 234 epidemic, 38 equilibrium, 143, 149, 150, 158 estimating, 18, 41, 99, 109 ethanol, 92, 94, 100, 102, 119, 120 EU, v, 1, 17, 31, 33, 34, 38, 39, 40, 43, 48, 76, 84,

85, 86, 87, 88, 113, 161, 162, 163, 166, 167, 174, 175, 176, 177, 179, 182, 183, 186, 187, 227, 229

Europe, 35, 36, 40, 79, 84, 87, 113, 117, 163, 164, 165, 166, 167, 176, 178, 187, 192

European Commission, 29, 30, 84, 113, 114, 182, 187

European Community, 34 European Parliament, 84, 86, 87, 88, 114 European Union, 77, 84, 88, 114, 161, 191, 203, 217,

223 evaporation, 207, 208, 220 expertise, 34, 99 exploitation, vii, 87, 91, 100, 110, 115, 116, 192 exposure, 138, 223, 224, 225, 226, 227, 228, 230,

231, 232, 233 external environment, 99 extraction, 18, 204, 205, 206, 208, 214, 221

F

family, 44, 49, 129 family support, 129 farmers, 90, 99, 104, 111 fatty acids, 212 fermentation, 102, 214 fertilizers, 139 financial institutions, vii Finland, 164, 174, 177, 188 fires, 35, 122 First World, 115, 116 flexibility, 75, 85, 91, 110 flocculation, 208, 209, 218, 220 flue gas, 40, 161, 167, 179, 227 fluidized bed, 23, 96, 102, 118, 164, 168, 176, 179 focusing, 89, 100, 106, 110, 162

food, 24, 33, 35, 63, 84, 85, 125, 127, 128, 129, 130, 162, 173, 203, 225

food production, 85 forest resources, 95 formal sector, 126, 127, 133, 134 fossil, 1, 2, 5, 12, 16, 17, 18, 23, 24, 27, 81, 82, 84,

86, 94, 96, 97, 99, 112, 167, 172, 176, 183, 185, 186, 191

France, 30, 70, 116 frost, 45 fuel, 18, 20, 23, 24, 27, 30, 32, 81, 84, 85, 86, 89, 90,

91, 92, 93, 94, 95, 96, 97, 99, 100, 101, 104, 109, 110, 111, 112, 113, 115, 118, 161, 162, 163, 168, 170, 172, 174, 176, 178, 179, 181, 182, 186, 192

fungi, 208, 210, 212, 213, 216, 217, 218, 228 fungus, 90, 210, 217, 221 furan, 26, 27

G

garbage, 32, 35, 37, 41, 167 gases, 90, 183 gasification, 12, 23, 92, 102, 108, 113, 116, 177,

178, 182, 184, 186, 188 gasoline, 94 GDP, 48 generation, 7, 8, 13, 22, 34, 40, 41, 44, 48, 73, 74,

77, 78, 82, 84, 85, 86, 92, 94, 96, 99, 101, 104, 108, 110, 112, 113, 117, 119, 123, 138, 162, 163, 165, 167, 176, 182, 186, 188, 223

Germany, 4, 20, 30, 32, 38, 43, 68, 113, 115, 165, 166, 167, 170, 171, 174, 176, 178, 179

germination, 207, 219 goods and services, 162 governance, 135 government, iv, 69, 82, 86, 88, 99, 121, 170 government policy, 121 grains, 89, 194 grass, 45, 75, 84, 94, 95, 109, 111, 118, 138, 219 grasses, 89, 233 Great Britain, 38, 78 Greece, v, 1, 2, 10, 13, 14, 15, 17, 18, 19, 21, 28, 30,

31, 32, 81, 101, 108, 109, 112, 115, 119, 120, 161, 162, 163, 164, 166, 175, 179, 180, 181, 182, 183, 184, 185, 186, 188, 189, 203, 207, 218

greenhouse gases, 82 group interactions, 143 groups, 2, 27, 48, 49, 138, 139, 144, 145 growth, 6, 10, 17, 85, 96, 97, 138, 164, 175, 179,

207, 209, 210, 211, 219 Guangdong, 119 guidance, 99, 112

Index

239

H

Haiti, 73 harassment, 122, 128 hardening process, 199 harmful effects, 138 harvesting, 84, 85, 89, 91, 94, 96, 97, 100, 104, 110,

115 hazardous materials, 65 hazardous substances, 170 hazardous wastes, 34, 35, 68, 169 hazards, 74, 77, 130 health, vii, 2, 3, 25, 32, 33, 34, 36, 37, 75, 82, 90, 96,

114, 127, 137, 138, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232

health problems, 36, 137 heat, 3, 4, 6, 11, 15, 23, 49, 50, 74, 82, 87, 90, 92,

94, 101, 110, 112, 113, 115, 162, 165, 166, 167, 168, 170, 186, 192

heating, 3, 11, 45, 49, 50, 90, 99, 101, 108, 109, 110, 156, 172, 176, 177, 178

heavy metals, 2, 40, 50, 65, 75, 139, 155, 157, 176, 225, 228, 229, 230, 232

height, 142, 148 hexachlorobenzene, 225 households, 4, 13, 34, 35, 48, 69, 75, 125 housing, 49, 50, 129 human exposure, 224 humidity, 50 Hungary, 166 Hunter, 112 hydrogen peroxide, 217 hydrolysis, 209 hygiene, 36, 37

I

ideal, 224, 226 Impact Assessment, 2 implementation, 2, 23, 26, 110, 112, 119, 182, 226 imports, 87, 88 imprisonment, 37 impurities, 140, 141, 196 incentives, 81, 83, 87 incidence, 226, 230 income, 37, 122, 128, 129, 133, 134 independence, 82 India, 122, 136, 200 indicators, 50, 79 Indonesia, 122 industrial emissions, vii industrial revolution, 33

industrial wastes, 82, 162, 173 industrialized countries, 92, 164 industry, 7, 23, 32, 69, 84, 85, 102, 111, 119, 171,

172, 176, 177, 179, 191, 192, 196, 200, 216, 217 infancy, 28, 81, 83 infection, 138 informal sector, 123, 126, 127, 135, 136 infrastructure, 10, 82, 91, 99, 102, 134 ingestion, 225, 226 inoculation, 213, 220 inoculum, 209 insects, 73, 74, 77 institutions, 35 insulation, 71 integration, 1, 28, 40, 86, 121, 123, 124, 128, 133,

224 interactions, 123, 124 interdependence, 94, 104 interference, 127, 134 internet, 36, 37 interrelationships, 94 intervention, 81 interview, 124 investment, 15, 75, 88, 98, 99, 101, 104, 110, 119,

179, 181, 213 investment appraisal, 119 investors, 81, 83, 97 ion-exchange, 144 ions, 139, 143, 144 Ireland, 163, 164, 166 iron, 171, 192, 196 isolation, 94 isotherms, 143, 144 Italy, 32, 74, 79, 165, 166, 167, 174, 175, 177, 178,

191, 192, 194, 201, 203, 207, 219

J

Japan, 30, 38, 74, 168 jobs, 129 jurisdiction, 134

K

kinetic model, 220 kinetic studies, 141, 158 kinetics, 157, 215

L

labor, 36, 104

Index

240

land, 2, 25, 27, 35, 37, 73, 74, 77, 87, 90, 96, 120, 207

land disposal, 37 land use, 2, 25 landfills, 1, 10, 12, 18, 20, 21, 23, 25, 27, 35, 38, 71,

74, 122, 134, 224, 228, 230 landscapes, 135 land-use, 96, 120 language, 71, 109 laws, 34, 38, 213 LDCs, 73 learning process, 99 legislation, 10, 12, 28, 88, 204, 207, 227, 229 life cycle, 18, 40, 76, 115 lifestyle, 34, 41 lifetime, 96, 101 lignin, 3, 210, 214, 220, 221 limestone, 168, 192, 193 limitation, 88, 114, 212 linear programming, 108, 113 lipids, 203, 205 liquid chromatography, 215 liquid fuels, 92, 110 liquids, 90, 115 livestock, 36, 112, 113 local authorities, vii, 122, 125, 130, 133, 226, 227 local government, 69 logging, 89, 104, 118 logistics, 15, 81, 82, 83, 94, 95, 97, 98, 99, 101, 102,

103, 106, 108, 109, 112, 113, 115, 117, 118, 119 Louisiana, 31 low risk, 91 Luxemburg, 29

M

Macedonia, 32, 108, 179, 181, 182, 183, 184, 185, 186, 187

machinery, 89, 94, 104, 118 magnesium, 196 maintenance, 25, 75, 114 management, 1, 2, 4, 5, 10, 11, 13, 17, 18, 21, 27, 28,

30, 31, 33, 34, 37, 38, 41, 48, 73, 75, 76, 77, 82, 83, 87, 91, 94, 97, 103, 106, 109, 110, 112, 113, 120, 121, 122, 123, 124, 133, 134, 135, 136, 138, 162, 163, 164, 180, 186, 205, 213, 218, 223, 224, 228

manganese, 210, 214, 220, 221 Manju, 140, 158 manufacturer, 194 manufacturing, 71, 174, 215 manure, 37, 92, 100, 213, 217

market, 6, 7, 8, 9, 10, 12, 15, 19, 20, 21, 37, 40, 87, 88, 93, 94, 97, 99, 114, 120, 132, 133, 135, 141, 178, 187, 192, 194

marketing, 87, 97, 114 markets, 2, 86, 118, 126, 129, 132, 133, 134 mass spectrometry, 215 mathematical programming, 106 matrix, 196 maturation, 212, 213, 220 MBI, 1, 2, 3, 4, 6, 7, 8, 9, 11, 22, 23, 28 measurement, 196, 224 measures, 10, 21, 26, 87, 88, 98, 99, 125, 128, 134,

227 mechanical properties, 198 media, 125, 219 Mediterranean, 189, 203, 204, 207, 231 Mediterranean countries, 203, 207 mercury, 2, 25, 26, 27, 158 Mercury, 26, 27, 32, 178 metabolites, 211 metal recovery, 25, 169 metals, 3, 4, 12, 13, 14, 15, 18, 22, 25, 36, 40, 50, 51,

65, 72, 75, 125, 129, 139, 155, 157, 162, 167, 168, 173, 174, 175, 176, 182, 183, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234

microorganism, 210 Microsoft, 124 microstructure, 200 microstructures, 199 mineral water, 71 miniature, 201 mining, 23, 35, 139 mixing, 213 model, 4, 5, 6, 13, 16, 17, 18, 30, 89, 95, 96, 100,

101, 102, 103, 104, 108, 109, 110, 112, 115, 117, 118, 119, 120, 214, 228, 229

modeling, 82, 83, 94, 95, 106, 107, 108, 109, 110, 112, 115, 117, 223, 229, 230, 233

models, 76, 85, 97, 99, 103, 104, 106, 110, 111, 120, 229, 232

modernization, 227 moisture, 3, 12, 16, 75, 89, 90, 102, 168, 172, 173,

180, 181, 205, 212 moisture content, 89, 90, 102, 168, 172, 180, 205 molecular weight, 209, 220 molecules, 143, 183 movement, 41, 73, 90

N

nation, 38, 185 natural gas, 86 natural resources, vii

Index

241

NCV, 13, 16, 18, 28, 187 Netherlands, 113, 164, 167, 174 network, 23, 83, 89, 93, 95, 98, 99, 101, 106, 108,

109, 110, 115, 129, 184, 185 NGOs, 123, 133, 134 Nigeria, 135 nitrogen, 50, 206, 215, 219 nodes, 100, 108, 110 noise, 65, 96 North America, 40, 84 nutrients, 203, 212

O

occupational health, 122, 133, 232 occupational risks, 128 OECD, 30, 41, 57, 79, 84, 85, 118 oil, 23, 49, 65, 82, 84, 86, 88, 179, 203, 204, 205,

206, 215, 216, 217, 218, 219, 220, 221 oil production, 203, 205 oils, 173 olive oil, 204, 205, 207, 208, 213, 214, 215, 216,

217, 218, 219, 220, 221 operator, 124 optimization, 95, 101, 103, 104, 108, 112, 113, 115,

117, 119 optimization method, 108 order, 1, 4, 5, 6, 10, 12, 13, 20, 36, 81, 83, 84, 85, 87,

89, 90, 91, 95, 97, 100, 103, 109, 123, 139, 148, 161, 162, 179, 194, 197, 198, 204, 210, 226, 228

organic chemicals, 167, 229 organic compounds, 25, 40, 65, 228, 234 organic matter, 17, 24, 50, 203, 204, 206, 207, 208,

209, 212, 213, 217 organic solvents, 205 oxidation, 168, 217 oxides, 23, 144 oxygen, 205, 206

P

Pacific, 78 packaging, 15, 40, 43, 49, 50, 51, 58, 61, 62, 63, 68,

72, 161, 173 Pakistan, 122, 135 parameter, 2, 27 parameters, 2, 45, 82, 94, 96, 100, 103, 108, 109,

111, 138, 142, 149, 151, 152, 167, 179, 196, 197, 215, 229, 233

Parliament, 86, 87, 88, 188 particles, 139, 140, 152, 183, 197 passive, 226, 227, 228, 232

PCDD/Fs, 224, 225, 226, 227, 228, 229, 230, 231, 232, 234

permit, 121, 126, 127, 130, 133, 179 Perth, 69 PET, 39, 43, 45, 47, 49, 50, 51, 61, 62, 68, 72 pH, 137, 140, 141, 143, 144, 145, 206, 207, 209,

211, 212 phenol, 157, 207, 211, 212, 213, 217, 220, 221 physical and mechanical properties, 191 physical properties, 196 physicochemical properties, 188 physics, 158 pigs, 36 planning, 21, 32, 38, 94, 97, 100, 101, 102, 103, 104,

106, 110, 111, 112, 118, 119, 135 planning decisions, 97 plasma, 225, 230, 233 plastics, 25, 43, 49, 61, 63, 68, 72, 86, 129, 139, 162,

172, 174, 181 Poland, 164 police, 122, 128 policy makers, 102, 123 pollutants, 88, 114, 138, 176, 187, 208, 223, 224,

225, 226, 227, 228, 229, 233 pollution, vii, 25, 40, 41, 82, 139, 168, 208, 220,

224, 225, 227, 228, 231 polychlorinated biphenyls (PCBs), 225 polychlorinated dibenzofurans, 230 polyphenols, 206, 209, 210, 215 polyurethane, 120 polyurethane foam, 120 population, 10, 35, 37, 135, 138, 212, 216, 223, 224,

225, 226, 227, 228, 229, 230, 231, 232, 233 population growth, 138 Portugal, 166, 214 power, 2, 4, 6, 7, 9, 12, 15, 20, 22, 23, 24, 25, 26, 27,

74, 82, 85, 86, 90, 91, 92, 93, 94, 97, 100, 101, 104, 108, 109, 112, 113, 117, 119, 120, 126, 139, 161, 162, 167, 171, 172, 176, 178, 179, 182, 183, 184, 185, 186, 188

power plants, 2, 6, 7, 9, 12, 15, 20, 22, 23, 25, 26, 100, 101, 109, 119, 139, 161, 162, 171, 172, 176, 178, 179, 182, 183, 184, 185, 186, 187

precipitation, 145 prediction, 43, 157 preference, 10, 126 present value, 101 pressure, 2, 3, 84, 167, 228 prevention, 38, 123, 224 price changes, 84 prices, 84, 99, 133 primary data, 76 primary school, 129

Index

242

producers, 97, 179, 204 product design, 138 production technology, 81, 82 productivity, 117, 207 profit, 99, 101, 112, 126 profitability, 94, 103, 106 program, 85, 104, 225, 226, 234 public administration, 48 public health, 2, 27, 74, 77, 122, 125, 127, 139, 170 public policy, 122 pulp, 84, 220 purification, 194, 203, 208, 218 purity, 68, 75 PVC, 50 pyrolysis, 12, 92, 96, 102, 120, 177, 178

Q

quality standards, 92 quartz, 194, 196 quotas, 88, 99

R

radiation, 196 radioactive waste, 73 range, 12, 33, 65, 90, 102, 110, 133, 140, 141, 144,

145, 151, 167, 168, 172, 203 raw materials, 40, 81, 83, 89, 104, 191, 192 reactivity, 200 reality, 42, 178 reason, 43, 68, 144, 145, 150, 194, 200 recognition, 121, 123, 124 recovery, 2, 3, 4, 6, 9, 12, 13, 23, 24, 27, 31, 34, 36,

38, 40, 49, 71, 73, 77, 123, 161, 162, 163, 167, 170, 185

recycling, 1, 2, 3, 4, 6, 10, 13, 14, 18, 21, 22, 24, 26, 27, 28, 31, 33, 34, 36, 37, 38, 39, 41, 43, 45, 48, 68, 69, 71, 75, 76, 77, 88, 121, 123, 124, 126, 127, 134, 136, 137, 138, 139, 161, 162, 172, 180, 184, 186, 191, 192, 213, 224

regeneration, 145, 157 region, 32, 48, 78, 83, 95, 96, 100, 101, 104, 108,

116, 135, 139, 184 regulation, 127, 162, 207, 229 regulations, 2, 26, 36, 48, 73, 87, 183, 224 regulators, 81, 83, 97 relationship, 133, 134 relevance, 87, 164 remediation, 158, 219 renewable energy, 24, 81, 85, 86, 87, 93, 112, 114,

163, 165, 187

reprocessing, 34, 35, 137, 139 residues, 4, 13, 14, 17, 18, 24, 82, 84, 85, 89, 92, 97,

99, 101, 104, 109, 111, 115, 117, 138, 157, 162, 172, 173, 174, 177, 194, 213, 214, 219

resource allocation, 109 resources, 3, 34, 48, 74, 81, 83, 84, 87, 95, 99, 100,

102, 104, 118, 162, 163 revenue, 41, 108 rice, 192, 200 rice husk, 192, 200 risk, 37, 68, 97, 116, 117, 129, 137, 138, 223, 224,

227, 228, 230, 231, 232 risk assessment, 223, 224, 228, 230, 231, 232 risk management, 97, 224 room temperature, 140, 141 routing, 96 rubber, 24, 50, 139, 175 rural areas, 33, 35, 37, 65, 84 Russia, 92

S

safety, 74, 77, 90, 96, 133, 136 salt, 183, 207 salts, 196, 205, 212 sampling, 33, 43, 44, 48, 224, 226, 230 saturation, 150, 152 savings, 2, 3, 5, 7, 8, 9, 18, 19, 20, 21, 39, 95, 184,

186 sawdust, 137, 140, 141, 143, 145, 147, 150, 151,

152, 153, 154, 155, 156, 157, 158, 173 Scandinavia, 92 scheduling, 96, 103, 104, 108, 109, 110, 112, 115,

118 seasonality, 81, 82, 93, 213 Second World, 37, 115 security, 84, 85, 86, 87, 88, 112, 114, 124, 125, 126,

128, 129, 186 sediments, 226 sensitivity, 9, 20, 21 separation, 3, 12, 38, 41, 71, 77, 123, 126, 134, 172,

173, 196, 217 septic tank, 207 sewage, vii, 35, 36, 37, 111, 167, 171, 172, 173, 174,

181, 207 shade, 140, 141 shape, 148, 197 side effects, 82 SIGMA, 107 silica, 159, 192, 193, 194, 196, 199, 212, 215 simulation, 95, 101, 103, 109, 110, 115, 118, 158 sintering, 171, 228 SiO2, 194, 195

Index

243

skin, 138, 204 slag, 192, 193, 194, 198 sludge, 35, 111, 157, 167, 171, 172, 173, 174, 181,

194, 208, 209, 211, 213, 215, 216, 217, 219 smoke, 125 social change, 48 social responsibility, 85 soil, vii, 12, 25, 35, 36, 37, 74, 75, 89, 174, 204, 207,

209, 213, 216, 218, 219, 220, 221, 226, 227, 228, 229, 231, 232, 234

solid state, 214 solid waste, vii, 10, 29, 30, 31, 33, 34, 36, 38, 41, 43,

45, 65, 71, 73, 75, 77, 78, 95, 122, 123, 135, 136, 137, 138, 139, 140, 156, 158, 161, 162, 171, 172, 182, 192, 205, 223, 224, 225, 230, 231, 232, 233, 234

solvents, 173 South Africa, 103, 204 Southeast Asia, 135 space, 3, 11, 90, 91, 95, 100, 133 Spain, vi, 118, 166, 203, 205, 207, 223, 224, 225,

227, 228, 229, 230, 232, 233, 234 spatial information, 119 species, 89, 209, 210, 211, 214, 219 specific heat, 3 specific surface, 144 spectroscopy, 215 Spring, 45 stabilization, 4, 38, 99, 218 stack gas, 179, 183 stakeholders, 81, 83, 97, 112, 121, 122, 133, 134,

186, 230 standard deviation, 143 standards, 26, 182, 207 statistics, 68, 124 steel, 86, 171, 192, 194, 196 steel industry, 194 stock, 37, 90, 91, 141, 176 storage, 41, 65, 66, 73, 77, 79, 81, 83, 86, 89, 90, 91,

94, 95, 96, 97, 98, 100, 101, 103, 104, 106, 108, 109, 111, 113, 115, 116, 118, 119, 167, 178, 179, 206, 210

strain, 209, 210, 219 strategies, 2, 29, 82, 99, 103, 108, 109, 118, 120,

139, 166 strength, 192, 197, 198, 199, 200, 201 substitutes, 13, 14, 18, 94, 161, 162 substrates, 82, 83, 85, 93, 102, 112, 210, 213, 218 sugar, 92, 103, 104, 116, 118 sugarcane, 102, 116 sulphur, 50, 176 summer, 36, 44, 45 suppliers, 96, 97, 98, 99

supply, 3, 11, 49, 81, 82, 83, 85, 86, 87, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 106, 107, 108, 109, 110, 111, 112, 113, 115, 116, 117, 119, 120, 138, 185, 213

supply chain, 81, 82, 83, 89, 91, 92, 93, 94, 95, 96, 97, 99, 100, 101, 102, 103, 104, 106, 108, 109, 110, 111, 112, 116, 117, 119, 120

supply curve, 101 surface area, 139, 141, 144 surface properties, 139, 143 surveillance, 225, 226, 227, 232, 234 sustainability, 83, 99, 101, 102, 106, 113, 121, 123,

134, 200 sustainable development, vii, 39, 135 Sweden, 74, 103, 109, 166, 177 Switzerland, 74, 164 Syria, 203

T

tannins, 212 targets, 10, 15, 21, 87, 88 tax cuts, 88, 98 taxonomy, 82, 83, 106, 110, 112 television, 43, 68 temperature, 25, 29, 50, 90, 140, 141, 144, 167, 170,

179, 212, 213 textiles, 36, 173, 174, 175 thermal energy, 23 thermal properties, 34 thermal treatment, 3, 10, 20, 30, 161, 163, 208 threat, 33, 84, 85, 129 threats, 37, 127, 135 timber, 85, 87, 89, 91 time frame, 5, 18 timing, 98, 104, 106, 108 total energy, 96, 165 total product, 192 toxic effect, 26 toxic products, 208 toxic substances, 2 toxicity, 27, 73, 206, 208, 212, 217 trade, 99, 112, 116, 172, 173 trading, 88, 114, 116 traffic, 96, 171 transesterification, 92 transformation, 71, 209, 213 transformations, 213 transition, 36, 135 transmission, 85 transport, 18, 33, 34, 36, 37, 42, 45, 47, 56, 65, 68,

73, 77, 78, 81, 83, 86, 89, 90, 91, 94, 95, 96, 97, 103, 109, 113, 114, 115, 143, 152, 229

Index

244

transport costs, 115 transportation, 15, 18, 73, 79, 86, 89, 90, 91, 92, 93,

94, 96, 100, 101, 102, 103, 104, 106, 108, 109, 115, 118

treatment methods, 104 trees, 24, 75, 82, 94, 108, 140, 207 trimmings, 24, 35, 75, 138, 234 Turkey, 116, 203

U

UK, 1, 29, 30, 32, 48, 74, 113, 117, 174, 175, 178 unemployment, 122, 134 unemployment rate, 134 uniform, 71, 168 United Kingdom, 29, 177 United Nations, 39, 82, 84, 86, 119 United States, v, 1, 73, 79, 113, 116 urbanisation, 41 urbanization, vii, 228 urine, 224, 225, 231

V

vacuum, 69, 123 validation, 233 variability, 34, 44, 81, 93, 94, 109, 110 variables, 81, 83, 94, 95, 101, 103, 108, 113 vegetation, 82, 204, 215, 226, 227, 228, 229, 231,

232, 233, 234 vehicles, 65, 70, 73, 76, 90, 91, 125, 133 Vietnam, 122

W

wage rate, 122 waste disposal, 36, 40, 74, 87, 139 waste incineration, 31, 162, 164, 166, 170, 171, 172,

233

waste incinerator, 170, 225, 226, 227, 229, 230, 231, 232, 233, 234

waste treatment, 1, 4, 5, 21, 29, 74, 76, 138, 162, 223, 224, 225, 228

waste water, 138, 215, 217, 219 wastewater, 137, 139, 140, 141, 142, 143, 150, 155,

156, 157, 158, 204, 206, 208, 209, 211, 214, 215, 216, 217, 218, 219, 220, 221

web, 34, 136 weight ratio, 140, 141, 197 Western Europe, 36, 115 wheat, 103, 109, 120, 210, 213, 214, 219 winter, 36, 45, 90, 92, 95 women, 233 wood, 15, 24, 35, 37, 50, 84, 85, 87, 89, 100, 101,

102, 104, 109, 110, 111, 113, 115, 129, 139, 172, 173, 174, 175, 179

wood waste, 24, 111 wool, 24 workers, 37, 41, 96, 133, 138, 225, 228, 230, 231,

233 working conditions, 122, 130, 133, 134 World Bank, 122, 136 World Wide Web, 29, 32 worry, 135

X

xenophobia, 129 XRD, 196

Y

yeast, 210, 214, 220, 221

Z

Zimbabwe, 129 ZnO, 195

Waste Management: Research Advances to Convert Waste to Wealth (Waste and Waste Management)

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Transcript of Waste Management: Research Advances to Convert Waste to Wealth (Waste and Waste Management)