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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
Characterisation of municipal solid waste and its recyclable contents of Guangzhou
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.
S. S. Chung, C. S. Poon
476 Waste Management & Research
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
S. S. Chung, C. S. Poon
478 Waste Management & Research
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
Characterisation of municipal solid waste and its recyclable contents of Guangzhou
479Waste Management & Research
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
S. S. Chung, C. S. Poon
480 Waste Management & Research
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.
Characterisation of municipal solid waste and its recyclable contents of Guangzhou
481Waste Management & Research
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
S. S. Chung, C. S. Poon
482 Waste Management & Research
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
Characterisation of municipal solid waste and its recyclable contents of Guangzhou
483Waste Management & Research
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
S. S. Chung, C. S. Poon
484 Waste Management & Research
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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
ad