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Waste Management & Research

DOI: 10.1177/0734242X0101900603

2001; 19; 473Waste Manag ResShan-Shan Chung and Chi-Sun Poon

Characterisation of municipal solid waste and its recyclable contents of Guangzhou

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Waste Manage Res 2001: 19: 473485

Printed in UK all rights reserved

Waste Management & Research

Copyright ISWA 2001

Waste Management & ResearchISSN 0734242X

473

IntroductionWaste characteristics, including both the physical and

chemical compositions, are essential data for designing

appropriate pollution control measures in the waste dis-

posal facilities and for waste management policy formu-

lation and evaluation. Waste recycling in particular is

material specific and has high specifications on the

homogenity of the waste materials. Composites, such as

liquid paper board1, composing more than one type of

generic material, would generally be more costly torecycle than other non-composite wastes. Waste-to-

energy is another treatment method that requires knowl-

edge of moisture contents and the make-up of the waste

streams. However, the waste characteristics of a city are

not always available in mainland China owing to the lack

of funding to carry out appropriate field studies and the

lack of awareness among local waste management offi-

cials of its importance.

Characterisation of municipal solid waste and itsrecyclable contents of Guangzhou

Shan-Shan ChungChi-Sun PoonResearch Centre for Urban Environmental Technology and

Management, Department of Civil and Structural Engineering,

The Hong Kong Polytechnic University, Hung Hom, Hong

Kong, China

Keywords Waste composition, recyclable contents, consumerbatteries, waste characterisation study, composite materials,

recyclability of waste, Guangzhou, mainland China

Corresponding author: C. S. Poon, Research Centre for UrbanEnvironmental Technology and Management, Department of

Civil and Structural Engineering, The Hong Kong Polytechnic

University, Hung Hom, Hong Kong, China

Received 05 May 2000, accepted in revised form 02 March 2001

Waste characteristics are essential data for waste dispos-

al facilities planning and waste management policy for-

mulation. However, waste composition studies are rarely

carried out in mainland Chinese cities and even when it

does, the methodologies used are not stringent. A year-

long field survey on the physical components of wasteand the recyclable in the waste stream has been con-

ducted in Guangzhou to fill the information gap and to

provide further experience for waste characterization

study in mainland China. It was found that the ash con-

tent in the waste stream has decreased considerably. But

the proportion of plastic materials in the waste stream

has increased and is now comparable to its more urban-

ized cities. Although this lends support to the recent

controls on expanded polystyrene food containers

implemented by the Guangzhou environmental protec-

tion bureau, more detailed analysis shows that the focusshould not only be on disposable food containers, but

also on film plastic waste. Furthermore, the abundance

of composite materials in the waste stream solicits atten-

tion from the waste management authority to step up

the monitoring of their generation pattern and to con-

sider imposing control measures.

1This is a formal term for paper board containers which are also lined with film plastics and/or metal foil.

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This paper presents the findings of a year-long field

study on waste characterisation in Guangzhou and com-

pares the results with those of the Hong Kong Self

Administrative Region (HK), Dublin (in Ireland) and

Heidelberg (in South Africa). The data of these three

cities were selected for comparison mainly for the reason

that the respective field characterisation study method-

ologies were also known either through published litera-

ture or through direct communication with the relevant

authorities. As the data and the methodologies form a

complete set and they have higher reference values. In

addition to the presentation of findings and the compar-

ison, the limitations of waste characterisation in the field

will be acknowledged and suggestions to improve on the

methodology of waste characterisation studies will be

made. The last two sections of this paper discuss how thefindings and experience gained in this research study can

be applied in waste management in Guangzhou.

Approaches in characterising municipal solidwaste and their pros and cons

Municipal solid waste (MSW) can be characterised by its

physical or chemical parameters. To characterise the

chemical fraction of the waste stream, representative

samples are to be prepared (careful mixing, grinding and

pulverising) for laboratory chemical analysis. However,

the metal fraction of the waste samples cannot be

addressed adequately by this method. Thus, Brunner &

Ernst (1986) suggested assessing the chemical composi-

tion of the waste stream from the products of waste treat-

ment process that involves substantial chemical

transformation of the waste matters, such as incinera-

tion, refuse-derived fuel processing and composting.

However, in a number of countries, including mainland

China, most of these processes or facilities are not in use

or found.More commonly, waste management authorities char-

acterised MSW by its physical contents. There are three

different ways to do this. One that is adopted by the

United State Environmental Protection Agency is the

material flows approach. In this approach, the waste

content and waste quantity are estimated on production

data for materials and products with adjustments for

imports, exports, recycling and product lifetimes

(Franklin Assoicates 1999). An inherent drawback of

this approach is that product residues associated with

other items (such as unconsumed fluid in containers) are

not accounted for. This is particularly a concern if the

moisture contents of waste are crucial data to the users.

In addition, this approach also fails to address variations

in local waste generation conditions (Martin et al. 1995).

Waste characterisation can also be obtained by con-

ducting questionnaire surveys on waste generators.

Although this is a lower cost alternative to other

approaches, researchers generally regard questionnaire

estimates as no more than an educated guess (Yu &

Maclaren 1995). An earlier study of Yu & Maclaren

(1995) showed that waste composition data on industri-

al waste obtained from questionnaire surveys correlates

poorly with field data.

Methodology review of the field characterisationapproach and its pros and cons

The last one is the field characterisation approach. This

is the most direct and often the only way to get to know

the waste stream, especially in small to medium-sized

open economies. As a result, it is more widely adopted.

Yet, a commonly recognised sample selection process to

minimise sampling bias does not exist.

A review of the required size of each sample extracted

for characterisation in the survey shows that there are

wide variations in practices. Tchobanoglous et al. (1993)

and Martin et al. (1995) suggested that each unit of the

sample should be about 91 kg while ERRA (1993) rec-

ommended a larger unit size of 100-200 kg. In South

Africa, each waste sample taken by Blight et al. (1999)

weighed from 20-30 kg or 85 litre in volume. Focusing on

a relatively small Irish community, Dennison et al.

(1996a, 1996b) were able to sort all the waste that had

been arranged to be delivered to the study site. In Hong

Kong and Germany, samples were extracted by volume.

One cubic metre of solid waste (average 190 kg) was

measured in Hong Kong (EPD 2000, pers. comm.) and1.1 cubic metre was used as the extraction standard for

each sample of waste in Germany (Federal Ministry for

Environment, Nature Conservation and Nuclear Safety

1993).

In Germany, the Federal Ministry for Environment

and Nature Conservation and Nuclear Safety (1993)

recommended a sampling time frame of 5 consecutive

seasons, with every sampling period consisting of 7 con-

secutive days, sampling about 5 to 7 tonnes of waste per

week for domestic waste. Similarly, the ERRA (1993)

S. S. Chung, C. S. Poon

474 Waste Management & Research

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recommended that to give the annual estimate, waste

analysis studies have to be carried out at three-monthly

intervals wherever budgetary and operational factors

allow. It also recommended that the sampling size should

vary according to the size of the population but with at

least 0.5 tonnes of waste to be sampled at each study

interval and up to 12.5 tonnes of waste if the number of

households at the population exceeds 50,000. Martin et

al. (1995), on the other hand, found that analysing 25

random samples, with each weighted at their recom-

mended fig., would give adequately accurate approxima-

tion at 2% error and 95% confidence level.

The sampling plans for a number of research studies

carried out in Chinese and European cities are also quite

different from the ones suggested above. Dennison et al.

(1996a, 1996b) carried out a waste characterisationstudy by performing field sorting on 57.1% of the target

households in their research (or 12 tonnes of waste in

aggregation) in just one season (autumn/winter period).

In Heidelberg, Blight et al. (1999) conducted waste char-

acterisation studies in all four seasons of the year2. In

Hong Kong, the characterisation study for the city aver-

age is obtained by field sorting on a 6-month interval at

two climatic seasons (summer and winter), but analysing

a larger number of samples. Usually, about 300 to 320

samples, adding up to 59 tonnes of waste, were analysed

in a year (EPD 2000). In Dongguan, a medium-sized city

in South China, the two most recent waste composition

studies were carried out in 1993 and 1995. In the 1993

study, six samples weighing about 0.6 tonnes in total

were randomly extracted for composition determination

and were analysed over a period of three consecutive

days in June, i.e. summer time (Lu 2000, pers. comm.).

In the 1995 study, again only six samples were analysed

(Zheng 1997, pers. comm.). Concerning sample extrac-

tion, ERRA (1993) and Tchobanoglous et al. (1993) pro-

posed using the coning and quartering method inextracting waste samples. The variation in these pro-

posed and adopted procedures suggests that waste char-

acterisation approaches are set out in accordance with

the availability of budget and the unique social and cus-

tomary practices.

Other than the lack of a standard sampling frame-

work, there are operational limitations in the field char-

acterisation approach. Sorting of waste with the pres-

ence of moisture means that small fragmented objects,

such as ashes, are likely to stick to the larger and entire

waste items. Thus, the resulting readings are likely to

overrepresent entire items but underrepresent smaller

waste items. However, this approach has several obvious

advantages over other appoaches. It can offer data on

specific waste streams and it does not require data on the

production sector and the ingress and egress of goods

and products for a place as in the material flow approach.

It also gives researchers firsthand data on the state of

waste and recyclable arisings of a place.

Limitations of previous waste composition

analysis in Guangzhou and objectives ofthe present studyGuangzhou is the capital city of the Guangdong

province. It is situated in the southern part of the

Peoples Republic of China. It has four distinct climatic

seasons with the wet seasons being in summer months.

As of 1998, it has a population of 3.99 million and a per

capita GDP of RMB 32,514 per year3 (Guangzhou

Yearbook 1999).

In mainland China, waste characteristics are not con-

sidered important and waste characterisation studies are

accorded low priority in view of general budget con-

straints. In a lot of mainland Chinese cities, waste char-

acterisation study, if carried out at all, is conducted on an

ad hoc basis, using single season data to represent a year-

round situation. Yet, the technical memorandum

released by the Chinese Ministry of Construction (1988)

required the waste composition to be known before

designing and constructing landfills.

A number of limitations are found with regard to the

previous waste composition analyses in Guangzhou.

First, they were only occassionally carried out owing tobudget constraints and generally the data of only one

sampling period (covering one season only) were used to

represent a years waste composition (see Guangzhou

Environmental Health Institute 1996 and Lei 1997).

Second, researchers of past waste composition analyses

took samples from both selected waste collection points

at residential districts and at landfills. The data were


475Waste Management & Research

2The aggregated amount of waste sorted was not reported.31USRMB8.5


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then compiled to form one data set to represent a single

year. This ignores the fact that waste scavenging activi-

ties take place at all levels of the waste collection process

(see Chung & Poon 1998). As a result, waste at the land-

fills is generally scavenged more intensively than waste at

the waste collection points. Direct aggregation of the

waste composition data from two different waste collec-

tion levels has obscured the effect of waste scavenging inthe waste stream and the data will also have the recy-

clable portion overrepresented. Third, past studies only

surveyed the generic composition of the waste matter

but did not give information on the recyclable contents

and the recyclability of the materials is assumed on the

basis of their generic material types. Therefore, the

potential of recycling as a tool to reduce disposal waste

stream is not clearly known.

In view of these limitations, a full-year study was

carried out by the authors in collaboration with the

Zhongshan University of Guangzhou in 1999 to deter-

mine the percentage distribution of waste, recyclable

components and the moisture contents of domestic solid

waste in Guangzhou. The material flows approach is not

used as there is no detailed record of the flow of goods

and products in and out of the city. Also, in view of the

absence of incineration, refuse-derived fuel and compost-

ing plant in Guangzhou, deriving the chemical fractions

of the waste in Brunner & Ernsts (1985) approach is also

not an option. The traditional handsorting field charac-

terisation of the physical composition of MSW is, there-fore, the only feasible approach in the case of Guangzhou.

The findings and the lessons learnt from the study should

provide relatively reliable and updated data for the prepa-

ration of waste management plans for Guangzhou.

MethodologySampling plan

The sampling plan should be designed to capture repre-

sentative waste samples. Theoretically, the number of

samples for field determination of waste characterisation

depends on the variation in the waste composition of

each sample in the sampling point. With thorough mix-

ing, even a small number of samples can reliably reflectthe percentage composition of the waste stream. In real-

ity, however, ideal conditions are hard to find. Owing to

seasonal, demographic and customary factors4, waste

receiving at different points of time at the reception

facility may vary considerably. Thus, the timing of the

survey must be such that the main variations within the

designed research timeframe are captured but does not

include the one-off erratic cases. In addition, the deter-

mination of sample size also depends on the budget avail-

ability of the relevant authority.

In view of the lack of common consensus among

waste management practitioners and researchers in the

timing of the study and the sample size, and taking into

consideration the large seasonal range in the humidity of

the South China region, the authors decided to conduct

sampling in all four seasons. Field characterisation stud-

ies were carried out in four different periods, namely,

January, May, September and December of 1999, to find

out the representative composition and moisture con-

tents of the waste streams for the four seasons. Each field

study period lasted two to three consecutive days. Inorder to obtain samples that would be typical of all the

administrative districts in Guangzhou, an equal number

of samples5 were taken from the waste stream of each of

the eight administrative districts.



4Waste composition is influenced by customary practices in the following ways: i) the generation of greater amount of fruit skins, such as watermelon skins, in summer; ii) the generation of more textile waste and waste of durable goods during the late winter months prior to the ChineseNew Year; and iii) a greater amount of food and packaging waste is likely to be generated during early spring time soon after the Chinese New

Year and in mid-autumn after the Mid-Autumn Festival.5The actual residential/industrial/commercial mixes of waste among the eight districts are not known by the waste management authorities ofGuangzhou. Thus, an equal number of samples were taken from each district and the data from each district is also given an equal weight in

working out the total waste composition.

Table 1. Details of the sampling plan

Jan, 1999 (Spring) May, 1999 (Summer) Oct, 1999 (Autumn) Dec, 1999 (Winter)

No. of samples from each administrative district 2 6 6 6Total no. of samples 16 48 48 48

Total weight for the samples prior to sorting (kg) 1881 5090 4896 4796Total weight of the waste sorted (kg) 1588 4986 4507 4481No. of days for the field study 2 3 3 3


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The sample selection process started with selecting

the residential refuse collection points (they are also

called huan wei zhan, literally, environmental hygiene

stations, in mainland China). Two to six refuse collec-

tion points in the residential areas from each adminis-

trative district were randomly selected. The staff of the

selected refuse collection points were instructed not to

dispose of the waste in the normal location but at the

surveying field during surveying periods. A total of 160

loads of waste were sorted in the four field studies.

Table 1 states the details of the sampling plan for this

study. With the additional resources from the

Municipal Environmental Health Bureau of

Guangzhou, the study was able to expand the total

number of samples from 16 to 48 for the summer,

autumn and winter studies. The field work was carriedout at the Li Keng landfill, one of the two landfills in

Guangzhou. The Li Keng landfill was chosen as it

accommodates the majority of the solid waste in

Guangzhou and, thus, reducing the need for the refuse

collection vehicle drivers to change routing.

About 6.6% of the waste (the discrepancy between

the weight of the sample before and after sorting of the

samples) taken was not sorted due to the following

reasons:

i. Wind blown error: since the sorting process was carried

out in the open, when wind is strong at times, especial-

ly during January and December, part of the sample,

especially the lighter portion, was blown away. It was

observed that film plastics were the most susceptible

materials to this cause. Paper waste, generally wetted,

was less affected. But it is believed that this is not a main

factor;

ii. Water loss error: evaporation and draining away of

leachate or fluid remaining in the waste matters were

the causes;

iii.Non-domestic waste: despite careful selection of sam-pling points, clinical wastes were found in the waste

samples. This is due to the presence of small state-run

out-patient clinics in the residential areas and the clini-

cal waste was handled together with domestic waste.

Since clinical waste is out of the scope of our research,

they were ignored in the subsequent weighing of indi-

vidual materials causing a discrepancy between the

extracted and sorted waste; and

iv. Human error: First, some sorters had the tendency to

keep the more valuable materials found during the sort-

ing process despite repeated warnings from the research

team. This was more prominently found during the first

survey. To minimise such error, sorters with poor disci-

pline were not hired in the subsequent surveys. Second,

due to the presence of moisture, the fine materials in the

waste were found to stick to the sorting platform, con-

tainers and tools. Researchers were not able to extract

them for further sorting and weighting. A third but minor

possibility was the cumulative error in weigh measure-

ment as a result of infrequent calibration of the scales.

The shares of individual waste materials presented in

Table 3 are expressed as a percentage of the waste sorted

(reported in row five of Table 1). Compared to the sam-

pling size of similar studies conducted in Hong Kong and

the recommended sample sizes of ERRA and theGerman environmental ministry, the sample size of the

present study is smaller. The residual or unknown

fraction (

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Characterisation process

A major step in a waste characterisation survey is to

decide how the waste shall be categorised. The classifi-

cation system used should be able to provide adequate

information for waste policy formulation and should also

be able to allow instant field identification. A principle

used in physical classification of waste is to group waste

types by the generic material types (such as plastics,

paper, textile, metals, glass, etc) of which the waste is

made up. In Hong Kong, for instance, liquid paper board,

composing mainly paper but consisting also of film plas-

tic and/or metal foil is classified as paper waste in Hong

Kong (EPD 2000, pers. comm.). This is also the

approach adopted in previous waste composition analy-

ses in the present study. It should, however, be noted that

in Hong Kong, some composite products, such as cam-eras, are classified in the others category, together with

unrecognisables and the less commonly found materials,

such as leather (EPD 2000, pers. comm.).

To render the findings from this study comparable to

previous findings, the classification system used in the

present study largely follows previous ones with the

exception of making consumer batteries a category on its

own. This is due to the consideration that Guangzhou

has plans to build a number of waste-to-energy facilities

in the near future and the heavy metal contents in

consumer batteries will, therefore, become a concern.

The classification for recyclable contents used in

Hong Kong was adopted in this study so that the findings

of the two cities could be directly compared. There was

also the intention to further sort each recyclable materi-

al according to its recyclability into good, average or

poor. Another more detailed classification system was

proposed by ERRA (1993) and was used by Dennison et

al. (1996a, 1996b) in their study.

The extracted sample was then handsorted into 19

categories (marked with * in Table 2) under the super-vision of the research team. For the readings of the

waste streams, the data from the 19 categories were

then regrouped into 12 principal categories (column 1

of Table 2). Active sorting was performed on all materi-

als, except for putrescibles. Towards the end of each

sorting exercise, the remaining waste matters were put

through a 15 mm sieve. Fine materials passing through

the sieve were classified as sand, ashes and fine unrecog-

nisables. Further detailed sorting was performed to pick

out all recognisable items (such as small pieces of paper,

plastics, stones, consumer batteries, etc) from the mate-

rials that did not pass through the sieve. The remains

were categorised as 15 mm putrescibles. The

40 mm and 20 mm sieves were used by the German

Ministry for Environment (1993) and ERRA (1993)

respectively to separate the fine particles from the rest

of the waste. But in this study, to be concordant with

previous waste composition analyses conducted in

Guangzhou, the 15 mm dimension was chosen for fine

particles.

During the sorting process, the contents of any con-

tainers or bags found in the waste were emptied. Liquid

was drained away and solid matters were sorted together

with all other waste. No further cleaning of the waste mat-

ters was performed before weighing. High-density polyeth-

ylene containers and rattan baskets with no covers were

used to contain the sorted materials. All the materialswere weighed with sorting containers on mechanical

scales that were calibrated each day before being used for

the measurements. The data on waste composition of this

study represent the percentage of the waste matters in the

domestic waste stream on a wet weigh basis.

Moisture contents

Separate samples were randomly taken from the same

waste load. Each sample was extracted and put in alu-

minium containers, tightly covered and then transported



Table 2. Categorisation of waste and recyclables

Waste Recyclables

< 15 mm ash, sand & unrecognisables* 15 mm putrescibles*

Rock, stone & sand*Paper Newspaper*Other waste paper*

Ferrous metals*Non-ferrous metals*Rags & textile products*Bamboo, wood & rattan*Glass Tinted glass*

Clear glass*Plastics Expanded polystyrene food

containers*Other expanded polystyrene*Plastic beverage containers*Coloured plastic bags*

Clear/white plastic bags*Other plastics*

Rubber*Consumer batteries*


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to the laboratory for the drying and weighting process on

the same day when the sample was taken. The time lag

between the sample collection and such laboratory pro-

cessing varied from 4 hours (for the last batch of samples

of the day) to 12 hours (for the first batch of samples of

the day). A total of 1,024 samples were analysed for their

moisture contents in this study. This sample size was

comparatively large6.

Bulky waste

Bulky waste refers to white and brown goods, furniture

and large pieces made up of more than one generic mate-

rial. The present sampling method is not able to analysis

bulky waste contents in the waste stream as they are

transported to the landfill in separate trips by general

purpose trucks if they are not already recovered in the

waste transfer process. This is similarly the case in Hong

Kong where the bulky waste is delivered separately to

landfills or refuse transfer stations. In Western cities,white and brown goods are also considered special items

and collected on special trips at regular intervals by the

waste collection authorities.

ResultsWaste composition and moisture contents

Table 3 states the seasonal and yearly averages of the

waste composition of Guangzhou in 1999. Putrescibles

and plastics are the two main categories. As expected,

the moisture content of waste is strongly influenced by

the weather. It is the highest in summer and spring

months.

Recyclable contents

Table 4 states the proportion of recyclables found in the

waste stream. The data are expressed as percentages

(by weight) of the total waste stream. The measure-

ment of each subcategory, expressed as a percentage of

the total recyclables found in the waste stream is shown



6

In Hong Kong, only about 147 samples are taken for the measurement of moisture content in each half yearly survey (EPD 1999b, pers. comm.).

Table 3. Seasonal and yearly averages of waste components in Guangzhou (1994 and 1999)

% (by weight, on a wet basis)

Jan May Oct Dec Yearly average(1999) 1994

15 mm putrescibles 48.0 58.7 54.7 59.4 58.1 59.6Ferrous metals 0.3 0.3 0.5 0.2 0.3Non-ferrous metals 0.4 0.2 0.2 0.3 0.3 0.6Paper 8.4 6.4 6.9 5.8 6.3Rags 5.3 3.7 5.9 4.1 4.8Plastics 14.6 13.9 15.1 14.4 14.5 15.9Rubber 0.8 0.3 0.2 0.4 0.4

Wood, bamboo & rattan 3.8 2.9 3.2 2.3 3.1Glass 3.6 2.4 1.8 1.8 2.00 2.9Consumer battery 0.1 0.2 0.1 0.01 0.1 -Moisture content 48.9 51.5 45.9 43.2 47.4 -

(NB: Fig.s may not add due to rounding)

Table 4. Recyclable contents in the waste stream of Guangzhou

year average(on wet weight basis %)

Paper Newspaper 1.4Other paper 5.0

Metals Ferrous metals 0.3

Non-ferrous metals 0.3Rags Rags 4.8Wood, bamboo & rattan 3.1Glass Tinted glass 0.7

Clear glass 1.3Foam plastics Plastic foam containers 1.0

Other foam plastics 0.3Plastic beverage containers Plastic beverage containers 0.1Plastic bags Coloured plastic bags 6.1

Clear plastic bags 4.9Other plastics Other plastics 2.0Non-recyclables 68.8


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in Fig. 1. Among the plastic recyclables, which repre-

sent 47% of the total recyclables, the majority is made

up of plastic bags, especially coloured plastic bags.

DiscussionWaste composition

Table 3 states the waste composition of Guangzhou in

1994 and 1999. Over the four years, there has been a

decrease in the sand and ash content of the waste but

increases were found in the plastic, paper and rags waste.

The proportion of putrescibles reduced slightly but still

made up the majority of the waste stream.

Such changes in the waste composition are found to

be consistent with the trend of increasing domestic use

of fossil gas fuel to replace solid fuel for heating and

cooking purposes in Guangzhou7 and with the belief that

economic growth8 tends to increase the proportion of

manufactured materials, such as plastics, paper and rags,

in the waste stream.Other than having an implication on the physical

make-up of the waste stream, such a change has an addi-

tional implication on pollution control at the landfills.

Andreas & Bilitewski (1999) found that as the ash

content of waste decreases through time, the acid

neutralisation capacity of the landfill decreases.

Therefore, hazardous substances, such as heavy metals,

tend to be more mobile, making the leachate from these

newer landfills (with less alkaline ashes and fine materi-

als) more toxic.

Fig. 2 compares the domestic waste composition ofGuangzhou, Hong Kong, Dublin and Heidelberg, a medi-

um income community in South Africa. The main dif-

ferences in the domestic waste streams of the four cities

are that: a) Guangzhou has the least paper and metal

contents; and b) the amount of putrescible waste is the

highest. Other than that, the waste stream of Guangzhou

is similar to the other cities compared. The former is

probably a result of the highly efficient paper and metal

recovery system in Guangzhou. The high putrescible

content is, however, a traditional trend in the waste

stream of Guangzhou (see Table 3). An explanation usu-

ally given is that vegetable produce sold in Guangzhou is

not thoroughly pre-processed to eliminate the inedible

parts. Calculations show that about 25% of the pur-

chased fresh vegetable matter is discarded by Guangzhou

citizens (Guangzhou Construction Committee &

Guangzhou Environmental Health Bureau 1999). It is

also possible that passive sorting on the putrescible waste

has overrepresented its share in the waste stream as even

the finest sorting process will not be able to pick out all

the non-putrescible matter in the remaining waste.

Recyclable contents

The researchers originally intended to further classify the

recyclables according to the level of contamination and

homogenity of the materials into recyclables having

good, fair and poor recycling values. However, dur-

ing the characterisation process, it was found that only a



Fig. 1. Composition of recyclables in Guangzhou (1999)

Fig. 2. The domestic waste composition of Guangzhou, Hong Kong,Dublin and Heidelberg. (Source of data for Hong Kong: EnvironmentalProtection Department 1999a; source of data for Dublin: Dennison etal. 1996a; source for Heidelberg: Blightet al. 1999)

7In 1994, about 84% of the households in Guangzhou were using fossil gas fuel with the remaining 16% using coal. In 1998, 99.2% of thehouseholds were using gas fuel (fig.s derived from Guangzhou Yearbook 1995and Guangzhou Yearbook 1999).8The per capita nominal GDP of Guangzhou in 1994 was 15497 and in 1998, this has risen to 32514 (Statistical Yearbook of Guangzhou

1997; Guangzhou Yearbook 1999).


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very small proportion (less than 5%) of the recyclables

could be considered good. It was also noted that even

the supposedly dry recyclables were found to be con-

siderably wetted and, thus, the surface was contaminat-

ed with fines. Three causes were noted:

1. Cross-contamination resulting from mixed waste

collection and transportation with putrescibles: paper

waste, film plastics and rags were particularly

vulnerable to such contamination;

2. The disposal habits of householders. Householders

tended to use the plastic bags as trash bags and

tended to put discards in unwanted containers before

putting out for waste collection; and

3. The presence of composite materials. A substantial

proportion of the materials in the other paper

category consisted of diapers, personal hygiene itemsand liquid paper board. This contributed to the low

recyclability of this category of products.

The research team was not able to determine which of

the above reasons was the main cause of the low recy-

clability of materials in the waste stream. But all phe-

nomena together confirmed that in addition to a source

separation network, product manufacturers/packagers

and waste generators alike have important roles to play

in enhancing the recyclability of materials.

Non-plastic recyclables

As previously reported (Table 4), recyclables accounted

for 31.2% of the domestic waste stream. Fig.s 3a and 3b

compare the recyclable contents in the domestic waste

streams in Guangzhou, Hong Kong and Dublin. In Hong

Kong and Dublin, about 51.4% and 50.5% respectively

of the waste matters are recyclables in the domestic

waste stream (EPD 1999a; Dennison 1996a). The lower

percentage of recyclables in Guangzhou is likely a result

of the more intensive profit-driven recovery activities bythe Guangzhou householders. Previous surveys found

that paper and metals are popular items set aside for

redemption at private recycling depots (see Chung &

Poon 2000). On top of this, another plausible reason for

the lower newspaper content in the waste stream of

Guangzhou is that newspapers in mainland China are

generally printed in thinner issues.

Plastic recyclables and plastic waste management

Management and control of plastic waste has become a

major issue in mainland China. The waste and litter

from plastic products has been dubbed the white pollu-

tion. The proportion of plastic waste as a whole in

Guangzhou is only slightly less than its more urbanised

counterpart, Hong Kong, and has already exceeded

those of other more developed Western cities (Fig. 2).

A closer examination of Fig. 3b reveals that plastic

beverage containers are found in relatively small

proportion and the majority in the waste stream is film

plastic products.



Fig. 3a. Non-plastic recyclables in the domestic waste stream ofGuangzhou, Hong Kong and Dublin

Fig. 3b. Plastics in the domestic waste stream of Guangzhou, HongKong and Dublin

(Source of data for Hong Kong: EPD 1999a; source of data for Dublin:Dennison et al. 1996; source of data for Guangzhou: authors)


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Composite materials

With the increasing application of composite materials

in products and product packaging, identification of

waste type in a field sorting survey according to the

above approach may be difficult. One example is to fit a

steel teaspoon with a large plastic handle into the tradi-

tional framework. It is not at all obvious whether it

should be treated as a metal item or a plastic item.

Another example is a household cleaning tool such as a

mop that is made with textile, plastics, wood and metals.

The textile part of a mop (after absorbing moisture) may

outweigh the wooden or plastic portion and be required

to be grouped into the rags category. But the same mop,

if it absorbs less moisture, can be classified as wood

waste. Determination of the major material constituent

(by weight) in a field survey situation has becomeincreasingly arbitrary also owing to the extensive appli-

cations of modern manufacturing technology. Two or

more generic materials can be manufactured to form a

new material, such as fibreglass. Modern manufacturing

and polymerisation technologies are also able to make

different materials look alike. As such, footwear made

with plastics may appear like leather shoes. To classify

these composite items using the traditional classification

framework without more detailed testing and measure-

ments reduces the accuracy of characterisation findings.

Another defect with this traditional classification sys-

tem is the false impression created for the recyclability of

the waste stream. Whenever there is a lack of further

detail on the recyclable contents of the waste stream, the

natural approach is to treat the generic material groups

in the waste, such as paper, plastics, metals, and glass, as

recyclable items. This is in fact the only way to infer the

recyclable content of waste for Guangzhou in the past

(see Lu 1997). However, such an inference cannot

reflect the real recyclability of the waste stream should a

substantial proportion of waste items identified aspaper is, in fact, liquid paper board or nappies. And

this is exactly what was found with the domestic paper

waste stream of Guangzhou. Since composite materials

as such are difficult to be materially recycled, paper is

no longer an obviously recyclable material under this

classification.

An alternative is to make the composite waste mate-

rials a category of its own. In Germany (Federal

Environmental Agency 1998), three types of composites

in the domestic waste stream are separately measured:

disposable nappies, packaging composite and com-

posite (household appliances made of a number of

materials, also known as bulky waste in other waste

characterisation studies). This appears to be a more rea-

sonable approach as making arbitrary judgement in the

field for most composite items can be avoided. At the

same time, users of the information would have better

understanding of the recyclability of these materials.

One of the reasons for classifying waste according to

the traditional framework is that different generic mate-

rials have unique heat values. Thus, the heat value of

mixed waste can be estimated, among others, from the

proportion of these materials in the waste stream. In

order not to compromise on the informative level of

waste composition data by deviating from the tradition-al classification system, the stand-alone composite

materials group can be subdivided into two categories:

composite with metals or glass and composite without

metals or glass. This can limit the variation in the heat

values of the composite materials within each category.

Batteries

The heavy metal contents in consumer batteries have

been a worldwide concern. According to a rough esti-

mate (Ke 1998), consumption of consumer batteries in

mainland China is around 600,000 tonnes a year or

about 0.5 kg/capita yr1. Since 0.13% of the domestic

waste stream is made up of consumer batteries (see Table

3), about 2,161 tonnes per year9 or 0.54 kg/capita yr1 of

battery waste are generated in Guangzhou. This is very

close to the national estimate. In comparison, Dennison

et al. (1996b) found that the domestic waste stream of

Dublin consisted of only 0.03% of consumer batteries in

1991. It appears that the disposal rate of consumer

batteries in Guangzhou has been approaching that of

developed cities and China as a whole is also consumingmore consumer batteries than some developed areas.

Since the use of mercury and other toxic heavy metals in

consumer batteries is still legally permitted in China, a

high rate of battery consumption would be a waste man-

agement concern.

Uncertainties

Other than the errors that were reported earlier, there

are a number of uncertainties to be addressed for



9

This is derived from the daily waste generation rate of 4,555 tonnes for the domestic and commercial streams in 1998 (Lei 1999).


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improving future solid waste characterisation in

Guangzhou. First, although the quantity of battery waste

is known, the quantity and types of heavy metal used in

the batteries are not covered in this study. Generally,

heavy metals contents and the level of chlorine in the

waste stream are also important data for planning waste

management facilities. Thus, further studies on the

chemical compositions of the waste stream in

Guangzhou are desirable.

Second, the infrequent calibration of the weighing

equipment may be a significant cause of the 6.6% waste

loss in the characterisation process, although such an

error can easily be reduced in future studies.

Third, as scavenging of recyclables is also taking place

at the landfill proper in Guangzhou, what our study

shows are, therefore, the waste and recyclable contentswithout such landfill scavenging activities. The actual

proportion of recyclables landfilled should be less than

what we have found. However, it is difficult to obtain

accurate data for recyclables scavenged from the landfill

owing to the unwillingness of the recyclable contractor

to disclose such information.

Implications on waste management ofGuangzhou

Waste characterisation studies provide information on

the properties and make-up of the waste and waste

stream at the point of disposal. A number of inferences

pertinent to the management of waste can be derived

from such an experience.

Ash content and pollution control in landfills

With the rapid phasing out of solid fuel in domestic use,

ash contents in the waste stream have decreased rapidly.

Without the alkaline ashes as the agent for fixing themetals in general waste matters, it is not at all wrong to

say that the leachate from modern solid waste streams is

more toxic than in olden days. In particular, it is found

that the waste stream in Guangzhou contains quite a

high level of consumer batteries and plastics. Thus, the

heavy metals from batteries, from colourants in polymer,

plating of utensils, etc, are more likely to be leached from

the waste and found in the leachate. This underscores

the importance of planning for leachate collection,

wastewater treatment facilities and the use of engineer-

ing measures to reduce leachate at present and future

landfills. For Guangzhou, this would mean that a higher

landfill compaction ratio, more extensive leachate col-

lection systems and more efficient leachate treatment

systems should be aimed at in the future.

Cross-contamination and household waste managementeducation

Our present study shows that the waste in Guangzhou

has high moisture contents. Visual inspection of individ-

ual waste materials at the field indicated that even the

paper and plastics are moisture laden. However, it was

not known if they were wetted by the householders

before mixed waste collection or due to mixed collection.To find out the real cause of contamination, it would be

necessary to carry out studies in earlier points of the

waste flow such as at the door-to-door collection stage.

Knowing these would give insights to how and at what

point source separation should be carried out and what

roles household waste management education should

play in enhancing extensive recycling.

The role of composting

From the findings reported in previous sections,

putrescibles have been the major component in the

domestic waste stream of Guangzhou. Thus, large scale

or centralised composting should be able to achieve

effective diversion from the disposal facilities in

Guangzhou given the implementation of source separa-

tion programmes.

Management and control of film plastic waste

From the present study, it is no false alarm that reduc-

ing the generation of plastic waste should be of top pri-

ority in Guangzhou. However, the current waste policyin Guangzhou is dominated by the measure10 to render

the relatively minor plastic waste stream, namely, the

EPS food containers, biodegradable. The effectiveness

of the ban on non-biodegradable EPS food containers

has been broadly criticised (see Zhao 1998). In our sur-

vey, despite the ban, these containers were still com-

monly found and used. Our study has pinpointed that

film plastic waste is equally a concern, if not more, in



10See the law on banning the use, manufacturing, and sale of non-biodegradable food containers which was enacted in 1997 (A Compendium ofEnvironmental Protection Laws 1994-1997).

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waste management terms. Other than advocating

source separation and greater recyclability, imposing a

product charge on film plastic products and packaging

should also be considered.

Implications on future waste characterisationstudies in mainland China

The review on the way domestic waste characterisation

studies have been carried out shows that there is no sin-

gle standardised way to select samples, sample sizes and

to categorise waste materials. In the course of this study,

a number of deficiencies and limitations are noted on the

characterisation methodology and classification system

commonly used in mainland China. This section focuses

on addressing these limitations and deficiencies and,whenever possible, suggestions for improvement are rec-

ommended. Some of the suggested modifications to the

traditional approach on waste characterisation studies

have implications in a much wider context.

Sampling recyclable contents

This is largely ignored in mainland China. Even in more

developed countries, such information is not always

available. Our experience has shown that combining

recyclable content surveys with routine waste character-

isation studies will only marginally increase the costs of

the survey while valuable information can be obtained.

Thus, it is urged that recyclable content survey shall be

considered an important extension of traditional waste

characterisation studies.

Composites

Generally, it is taken for granted that materials classified

as paper, plastics, metals, etc, are recyclables. With the

increasing use of composite materials, a simple classifica-

tion system may need to be revised. It is recommendedthat the traditional classification scheme for waste char-

acterisation studies shall be modified to include two

additional waste groups: composite with glass/metal

and composite without glass/metal. The data set will

then be a better indication of the recyclability of materi-

als in the disposal waste streams. Such data will also be

more useful for monitoring the trend of the generation of

such difficult-to-recycle materials and become one of the

decision-making bases for introducing, if necessary, pro-

ducer responsibility measures.

Sampling points

In Guangzhou, as well as in other developing country

cities, waste scavenging is common in all parts of the

waste flow. It is recommended that only measurements

deriving from the same level in the waste disposal route

can be aggregated. Measuring the moisture contents of

different categories of waste materials at various nodes of

waste collection will also show the effect of mixed col-

lection on cross-contamination of recyclables. As dis-

cussed above, this will have an implication on the role of

household waste management education.

Bulky waste

From our experience, bulky waste cannot be readily

analysable with normal household wastes. Where weigh-

bridges are available, it would be more appropriate toestimate the proportion of bulky waste in a waste stream

by measuring the bulky waste and normal household

waste streams separately.

ConclusionIt was found that the waste composition of Guangzhou

has experienced two major changes in the past half a

decade: a decrease in the ash content and an increase in

the share and absolute amount of manufactured product

wastes, such as paper, glass and plastics. While this is

generally believed as a sign of urbanisation and econom-

ic growth, it also indicates the necessity to set out corre-

sponding waste management measures. Particularly of

concern are the high percentages of film plastics and

consumer batteries in the waste stream when compared

to other modern cities. In view of this, carrying out a

chemical composition analysis on the waste stream

would be desirable before planning for future waste man-

agement facilities, such as waste-to-energy plants, in

Guangzhou.Knowing the waste characteristics is important to

waste policy making and monitoring. However, in most

part of mainland China where even the basics of waste

management, for example, waste collection and public

cleansing, are not carried out in a satisfactory manner,

it is of no surprise that waste characterisation has not

been assigned enough importance. However, with the

landfill crisis and the growing awareness of the need

to reduce and recycle, it is expected that waste charac-

terisation studies will play a more important role in




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assisting policy formulation.

Past waste characterisation studies carried out in

Guangzhou and in other mainland Chinese cities left

much to be desired in terms of their sampling proce-

dures, sampling sizes and the waste classification

schemes used. The findings brought out by this paper

should be able to refocus attention on this investigation

tool. This paper also states the significance and the

necessity of extending the scope of purely waste char-

acterisation to examine recyclable contents at different

points of the waste flow in future studies in mainland

China. In short, waste and recyclable content surveys

should no longer be treated as an ad hoc or dispensable

assignment but be regarded as a regular operation in

cities of mainland China.

AcknowledgementsThe authors would like to thank the Hong Kong

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