(*) Joao Mello – CEO – A&C consulting – jmello@andradecanellas.com.br

LANDFILL GAS POWER GENERATION - RECENT DEVELOPMENTS IN BRAZIL -

M.RODRIGUES J.MELLO (*) F.MOREIRA L. SANTOS J.NEGRI

A&C Consulting ESTRE Ambiental São Paulo Energy, Water & Sanitation Secretary

Brazil Brazil Brazil

SUMMARY Each person in Brazil generates from 0.5 to 1 kg of solid waste per day, an amount estimated to grow 5% yearly, that is deposited mainly in landfills (>70%). This waste is composed mainly by organic matter (60%), which enables a large caloric value and up to an average of 80 m³ per ton of waste of recovered methane. As this waste decomposes, it produces landfill biogas that contributes to the formation of smog, poses explosion hazard and is composed of more than 50% methane. If emitted to the atmosphere methane is a greenhouse 23 times more potent than carbon dioxide over a hundred year time period. Additionally, methane cycles through the atmosphere about 20 times more quickly than carbon dioxide, so its mitigation is a quick progress to slowing global climate change. Methane is also a valuable source of energy and landfill biogas is generated continuously constituting a reliable fuel for a range of applications, including power generation. Many opportunities exist across Brazil to harness the energy content in landfills. A shift occurred between 1995 and 2000 from 76% of solid waste residues being exposed in open dumps in Brazil to almost 70% being disposed in landfills. Regarding power generation the most widespread technology is the internal combustion spark ignition engines due to its high efficiency, relatively low cost and good size match with the gas output of many landfills. Engines are also more resistant to corrosion, deposits and erosion than its counterpart, the gas turbines. Although historically the efficiencies for engines that use landfill gas have been lower when compared to those running on natural gas, a new generation of engines start to present higher efficiencies (~40%), as they are specifically developed for this application. Major engine suppliers have or are designing engines for landfill gas application. This paper presents an overview on recent developments in power generation from landfill gas including performance and costs in Brazil, based on the two outmost relevant projects, Bandeirantes and Sao João. Furthermore a real life landfill development feasibility study is presented. It considers the choice amongst the main engine suppliers, assesses gas production, treatment requirements according to the landfill gas composition, investment Costs, O&M and emissions.

KEYWORDS Landfill Gas, Biogas Power Generation, CDM, Renewable Emerging Technologies

21, rue d’Artois, F-75008 PARIS D1-106 CIGRE 2008 http : //www.cigre.org

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1. INTRODUCTION - LANDFILLS IN BRAZIL The use of landfills as final destinations for waste is a relatively recent practice in Brazil. Although there has been a big shift between 1995 and 2000 in waste disposal, there is still the practice of disposing the waste in open fields and there are no policies concerning recycling and reuse. Currently about 70% of the waste in the country is destined to landfills but this percentage can be as high as 100% in municipalities located in more developed regions like São Paulo state. Figure 1 presents the main destinations for municipal solid residues in Brazil in 2000, a result from a National Sanitation Survey, produced by IBGE – Brazilian Geography and Statistics Institute. The category labeled as ‘Others’ includes open flooded fields, organic processing, recycling etc.

According to a similar IBGE survey published in 1991 [1], 76% of all wasted collected by the government administration was destined to open dumps. The data from 2000 shows a heavy decrease in this practice and the adoption of new and more environmentally friendly solutions such as sanitary landfills, responsible for 41% of the waste disposal that year. The amount collected by the government also

increased from near 100,000 metric tons per day in 1991 to almost 158,000 in 2000, with Southeast, most developed region, contributing with over 77,000 metric tons per day.

At the province of São Paulo, the Energy, Water & Sanitation Secretary (SP-EW&S), together with Environmental Secretary, initiated a study to monitor the conditions of systems of disposal and treatment of solid waste in each of the 645 of the state of São Paulo [2]. This study is updated annually and the conditions are determined through quality indicators that classify the landfills into inadequate, controlled and adequate. The results obtained at the beginning of this assessment in 1997 have demonstrated that only about 11% of the residues were disposed adequately. According to the 10th report issued in 2006, this number went up to 80,7 %. This represents a shift from around 2.000 tons in 1997 to 23.000 tons per day in 2006.

Most landfill gas projects aim at the revenues from carbon credits of methane destruction. The main reason for that is the relatively small investment for the capture and combustion of Biogas that enables gains expected to be between 15 and 20 € per tone of carbon from 2008 on. Currently Brazil has 255 projects of greenhouse gases submitted for Clean Development Mechanism, placing Brazil on the 3rd position in project number, behind China and India only. Of the total number 171 projects have already been approved. Amongst the approved projects, 11 % are based on the mitigation of methane in sanitary landfills, equivalent to 20 projects that aim reducing the 47 million tons of CO2 in the next 10 years. When it comes to sanitary landfills, Brazil holds the first position in CDM projects. Figure 2 shows a landfill in the province of São Paulo nearby a mid-size district (1-2 million inhabitants) in which only the landfill gas is fired and it received methane mitigation CDM project label.

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Figure 1 - Waste Disposal in Brazil by Final Destination

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Figure 2 - Estre Paulina Landfill Gas Facilities

2. POWER FROM LANDFILL GAS IN SÃO PAULO The São Paulo province has around 43 million inhabitants which correspond to 21% of entire population of Brazil. It is also the biggest economy of Brazil representing around 30-35% GDP and growing faster. Consequently the energy consumption amounted to 30% of the national matrix and, industrial and transportation sectors have been the most significant energy consumers. Clearly, these sectors are the most important sources of CO2 emissions. The province has emissions profile nearly 25% of Brazil, which would become the province 39th largest emitter in the world. Recently, the carbon intensity in São Paulo was 32% lower than the national average. The provincial government has been taking some climate-friendly initiatives and landfill emission reduction through the improvement of waste disposal areas and landfills. This effort is giving results, like the usage of landfill gas to generate energy. São Paulo has the largest generation plant firing landfill gas in the world, Bandeirantes Landfill Thermal Plant, which has the capacity to produce 20 MW.avg until 2018. Besides there is a new one, quite similar in capacity commissioning in 2008, to operate for next 15 years (São João). The exploitation of landfill gas is a district concession given by the municipality.

Bandeirantes landfill is located in São Paulo Capital District serving a population around 6 million. The district has a total of 10 million plus other 10 in surrounding. The landfill started operations in 1979 and closed in March 2007 with around 2Mton per year of waste disposal, mainly residential. The location of landfill is shown in Figure

3.

Figure 3 – Bandeirantes Landfill Location (source: Biogás)

As can be seen the site is in the outskirts of São Paulo, a city with high emission control. A flow of 12.000 cu. meters per hour of landfill gas containing a minimum methane number of 50 is used in Bandeirantes power gen and it is equivalent to an emission reduction to reach 7.5 Mtones CO2e in the first crediting period (2004 – 2010) in CDM project. Bandeirantes landfill is divided into old and new cells. As can e seen in Figure 4 the landfill gas chain goes through a gas treatment prior to the power plant at the end.

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Gas collection Gas extraction andflare burner

EnergyUtilization

Figure 4 – Degasifying and energy utilization schemes (source: CDM PDD)

Figure 5 – Bandeirantes Landfill

Facilities

The power capacity is 22 MW with 24 Cat3516engines, nominal capacity of 925 kW, organized in two sets of 22 units. Almost fifty km of piping is installed together with vertical drains. The Brazilian knowledge is acquired from Van der Wiel – Dutch firm acting in the transport, infrastructure and environmental technique – and ArcadisLogos responsible for landfill gas capture engineering design.

The set of equipment used in this project are engines for power generation, flow meters, gas analyzer, and flares. Figure 5 illustrates snapshots of Bandeirantes facilities from landfill to power generator groups.

Power generation from biogas in Brazil only recently began to demonstrate economical feasibility as electricity prices increase over US$ 60/MWh for new power contracts. In Brazil the first biogas power plant to operate was Bandeirantes, mostly sold bilaterally as an IPP. The São João Landfill, located in eastern part of São Paulo, with an installed capacity of 22,4 MW, sold partially its energy in long term contracts (15-year duration) to DISCO utilities in a public auction.

3. POTENTIAL OF POWER GEN FROM LANDFILL GAS IN SÃO PAULO Given the excellent example of Bandeirantes Landfill, other similar projects have been rising in São Paulo province. However, the landfill gas capacity production to justify investments in power generation should be carefully evaluated. The application of landfill as the final destination of solid residues, mainly residential, is under debate.

The criticism and drawbacks are: (i) unavailability of cheap areas for new solutions nearby urban centers; (ii) some environmental concerns such as underground water contamination and repulsive smells; (iii) high costs of landfill operation, control, and recovering; (iv) possible further legislation banning new landfill solutions.

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There is over 200 MWavg of potential landfill in São Paulo province in 2007 and this value might increase to 250 MWavg by 2025 based on official inventory of waste on landfill (see Figure 6). This estimate takes into account the potential increase in gas generated based on EPA`s model [3] taking into account waste generated will stabilize and even decrease slightly. The potential calculations also considered that only residential municipal solid waste and leaving out waste from supermarkets, malls and other commercial buildings, so the actual potential might be higher. The calculations considered a scenario of “Landfill Constrained” with an annual increase of only 500.000 tones up to 2018 and finally reducing to 9 Mtones until 2021. For this scenario, Figure 7 presents the expected Biogas and methane composition based on simulations.

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year year Figure 7 – Expected Biogas Production – Scenario “Landfill Constrained”

For 2010 biogas production would be around 160.000 N.m³/h, resulting in a generation of 213 MW.avg, considering cycle Otto engines for biogas with a heat rate of 8.78 MJ/kWh (efficiency of 41%) e a biogas collection of 65%, average value in projects current running. In 2025, the biogas generation would stabilize around 180.000 N.m³/h and the capacity could reach 243 MW.avg in same conditions. Those values mean specific generation of 2 kWh/N.m³ from biogas.

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4. REAL LIFE PROJECT ASSESSMENT The real life “case study” herein presented is based on a technical and economical feasibility study of a power generation plant from landfill gases for the Center of Residue Management of ESTRE, in Paulínia, Campinas, in São Paulo province, presented in Figure 2. The landfill already has a CDM project namely Recovery landfill gas project, approved by the Brazilian CDM board. The capacity for this landfill is approximately 6.5 million tons of residues in its initial phase. The landfill receives approximately 3.000 metric tons per day of waste from nearby municipalities. The districts in São Paulo province are classified according the saturation degree of determined atmospheric pollution and many are considered saturated in ozone (O3), which by provincial Decree implies new plants to compensate emissions in levels equal or superior to: (i) particulate – 100 ton/y; (ii) NOx – 40 ton/y; (iii) Volatile Organics, except methane – 40 ton/y; (iv) SOx – 250 ton/y; (v) CO – 100 ton/y. The technical feasibility study comprised the gas treatment concept, engine selection and emission control equipment. The pre-combustion gas treatment is determined so that the raw gas is treated to meet the quality specified by warranty agreements of engines. The basic pretreatment concept required is presented in Figure 8. The concept was slightly changed for one of the configurations, as this engine requires a stricter cleaning, with the gas being cooled down to 4°C. The lower temperature results in a cleaner gas and consequently lower maintenance costs. Conversely, there is the need for a higher consumption of electricity.

ENGINES

C-01 Blower TQ-01 Leachate Tank TC-01 CondensorTQ-02 Knockout Drum C-02 Blower F-01 Filter

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Q = 3.095 Nm3/hP = 37 mmbar

T = 14ºCQ = 3.095 Nm3/hP = 32 mmbar

TQ-01

2T = 14ºCQ = 3.095 Nm3/hP = 32 mmbar

T = 27ºCQ = 3.095 Nm3/hP = 150 mmbar

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T = 14ºCQ = 3.095 Nm3/hP = 32 mmbar

TQ-01

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Figure 8 - Raw Gas Pretreatment

This system was designed so that is able to remove sulphur gases, halogenated compounds, ammonia, silicon compounds and siloxans. This clean-up process is widely adopted and is able to lower gas contaminants to maximum levels as required by engines from several manufacturers [4]. A number of engine models from major manufacturers were selected for this case. These engines models are either designed or adapted for the use of landfill gas. Some manufacturers also considered models with lean combustion technology to lower NOx emissions in detriment of efficiency. Table 1 presents only the lean combustion alternatives and the configurations 1 and 2 differ only by the number of engines.

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NOx and Carbon Monoxide emissions are major concerns in this case study as local regulation limits the net NOx emissions for new plants to 40 metric tons per years and the carbon monoxide to 100 metric tons per year. The emission constraints in ozone saturated regions of São Paulo are so strict that the lean combustion solution was not enough to comply and a Selective Catalyst Reduction (SCR) system had to be considered with a considerable impact on investment and O&M costs. Moreover, after burning of combustion exhaust is also required to mitigate CO emissions. Table 1 presents the main parameters for power gen. Total investment costs ranged from US$ 1200 to 1500/kWinstalled, total O&M average costs including overhaul, ranged from US$ 28 to 47/MWh. It is important to mention that the O&M comprises also the SCR and afterburning. Table 1 - Main Power Generation Parameters

Configuration Efficiency (on site)

Power generated

(MW)

# of engines

Installed capacity (MW)

Engine Availability

Internal consumption

(kW)

AverageAvailable

power (MW)

1 39,0% 7,35 6 9,0 93% 941 5,89

2 39,0% 5,88 5 7,5 93% 941 4,53

3 35,1% 5,99 8 7,2 91% 941 4,52

4 31,8% 5,99 7 7,35 95% 941 4,75

5 33,9% 5,88 7 7,13 91% 1.043 4,31

4.1. Economic Feasibility The power production from landfill biogas has sustainable market opportunities with specific benefits. Among the main incentives, can be distinguished: (i) reduction of 100% in the network use tariff; (ii) commercialization as Distributed Generation (DG) directly to the local utility up to 10% of its market; (iii) yearly assured energy for trading defined based on the average generation; (iv) long term bilateral contracts with Discos; through public auctions, as new energy assets; (v) direct trading with deregulated consumers with demand above the 500kW.

The economic feasibility analysis provides the price of energy considering engine options and the investor’s required return. Technical analysis provides inputs to the economic-financial model such as capital expenditure (CAPEX) and O&M expenses (fixed, variable and overhaul) for each engine option in Table 1. The main input is the energy production, which varies according to annual biogas production in the landfill, as consequence of the yearly deposited quantity of waste until achieving full capacity. Projected cash flows allow the calculation of the Internal Rate of Return (IRR) given an energy price, or an “Equilibrium Energy Price” for a given Rate of Return. Power generation from biogas can be divided in

two main steps: landfill gas collection for combustion (landfill gas collection) and landfill gas for power generation. Possible engine options and configurations were ranked by their equilibrium energy price. Figure 9 besides shows

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the relative difference among engine configurations investigated to generate power from landfill gas in Paulinia.

As can be seen, lowest prices are found in configurations 1, 2 and 5 and, therefore, their equilibrium energy prices shows these have more margin to be competitive in the energy market. Moreover these results are suitable to the investor target looking for bilateral contracts in deregulated market. In turn, configurations 3 and 4 have been rejected.

The results were mainly influenced by the high conversion efficiency of engines of configurations 1 e 2 and good environmental performance (no need for SCR with configuration 2). Configuration 5 main competitive advantage was the lower maintenance costs that resulted from a stricter gas treatment process.

5. CONCLUSIONS In the real life assessment of Landfill gas Power Generation investigated, despite environmental constraints associated with NOx and CO emissions, three solutions demonstrated cost effectiveness. This means that power generation from landfill biogas has real opportunities in Brazilian power market. The result could be much better if the solution is to be implemented is regions less saturated with ozone, where emission controls are usually binding. It is important to emphasize that the pretreatment scheme was designed to meet the engine material requirements firing an aggressive gas.

There is still a large potential in Brazil for the use of Landfill gas for Power Generation, and as São Paulo accounts for 20% of solid waste collection, the potential for Brazil can be over 1 GW. The emerging technologies should be frequently applied in Landfill gas Power Generation and better emission control, improve efficiency of conversion, enhance gas treatment to perform better the engine, are undoubtedly issues to be supported.

The logistic and infra-structures are important and the cost effectiveness could be improved if an optimization was performed in the use of gas allowing the use of the gas generation peak with mobile engine modules able to serve several landfills with flexible logistic.

ACKNOWLODGMENTS The authors gratefully acknowledge all A&C consulting team members directly involved with landfill projects, in special Economic & Financial and Thermal Generation teams; and for engineer Manzano and Mr. Koza for their continuous support. The technical team of ESTRE gently supports all requirements and the authors acknowledge and are very pleased with them.

BIBLIOGRAPHY [1] PNSB – National Basic Sanitation Survey in English, published by Instituto Brasileiro de

Geografia e Estatística (IBGE – Brazilian Geography and Statistics Institute in English), São Paulo, Brazil 2000.

[2] Monitoring of conditions of system disposal and treatment of solid residues, CETESB, 2007 (in Portuguese).

[3] A Liability into an Asset: A Landfill Gas-to-Energy Project Development Handbook, Washington, D.C; EPA; USA, Sept. 1996.

[4] Guidance on gas Treatment Technologies for Landfill Gas Engines, SEPA, Environment Agency, Bristol , UK, August 2004.

[5] J.Mello et alli, Electricity Generation with Biomass and Biogas, Special Committee of Bioenergy in São Paulo State, 2007 (in Portuguese).