Kerbside garbage composition: recent
findings
Introduction
There have been significant changes to municipal waste collection systems in the past ten
years as increasing numbers of councils have introduced improvements and adopted “best
practice” recycling.
Looking at what is discarded in garbage bins by undertaking bin audits provides the means to
understand what the changes have achieved, and to better understand the composition of
waste going to landfill and what could be recovered for recycling or composting.
Accordingly, audits of household garbage bins were conducted to look at the composition of
materials discarded by households in metropolitan Melbourne (which accounts for 71% of
Victoria’s household waste1). These were conducted over a one week period in May 2008.
The audit involved the sorting, weighing and categorising of five tonnes of domestic garbage.
There were 150 randomly selected bins collected in a garbage truck from four metropolitan
local governments. The total 600 bins were delivered to a central audit site for sorting. The
categories and definitions are provided in the appendices.
To supplement the bin audits, Sustainability Victoria also conducted a review of the results of
bin audits conducted by metropolitan Melbourne local governments from 2005 to 2007.
Most local governments now have a two bin system and an increasing number of local
governments have downsized their garbage bins from 240L to 120L or 80L. There are 37
local governments providing a three bin system which separates out food and garden waste.2
1
Sustainability Victoria 2008 Victorian Local Government Annual Survey 2006-2007.
http://www.sustainability.vic.gov.au/www/html/1730-login.asp
2
Ibid p 7.
Kerbside bin audits of key municipalities
Building on the findings from the desktop review of existing kerbside bin audits to guide its
methodology and classifications, Sustainability Victoria commissioned a Victorian bin auditing
company, Wastemin, to conduct bin audits across four municipalities in metropolitan
Melbourne.
The kerbside bin audits, conducted over four municipalities, found that nearly 20% of garbage
bin content was made up of recyclables. Organics made up close to 50%, with more than
40% of this being food. Therefore nearly three quarters of waste going to landfill could be
recovered. Even the most conservative view of these figures (given the sample size) would
suggest at least half of the garbage stream is recoverable.
Figure 1 shows the composition of garbage bin audits undertaken in Victoria for four
metropolitan local governments during 2008. All figures provided below are by weight.
Figure 1: Garbage bin composition from bin audits of four metropolitan local governments
Garbage Bin Audits 2008, Metro Councils
(n=4)
Aluminium Cans / Foil
0.5%
Total Plastics (1 to 7)
2.7%
Glass
Steel Cans
1.2%
2.9%
Aerosol Cans
0.1%
Total Other
24.6%
Total Paper
12.1%
Nappies / sanitary
3.1%
Garden Waste
7.2%
Prohibited
2.7%
Hazardous
1.9%
Food Waste
41.0%
The composition of these audits show similar proportions to those found in the 2005-2007
audits. There is a large proportion of recoverable green and food waste found in the kerbside
garbage stream. These findings demonstrate the benefits of a three bin system. Local
governments with a two bin system (recyclables and garbage) have a much higher proportion
of garden waste compared to the three bin system. Figures 5 and 6 show this difference.
Figure 2 shows the local government with a two bin system. Nearly 15% of garden waste was
found in garbage bins in this audit.
Kerbside Garbage Composition: Recent Findings
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Figure 2: Garbage bin composition from metropolitan local government with two bin system
Garbage Bin Audits 2008, Metro Councils, 2 Bin System
(n=1)
Total Plastics (1 to 7)
4.0%
Aluminium Cans / Foil
0.5%
Steel Cans
0.8%
Glass
3.1%
Total Other
20.3%
Aerosol Cans
0.1%
Total Paper
12.0%
Nappies / sanitary
3.9%
Prohibited
3.0%
Garden Waste
14.6%
Hazardous
1.2%
Food Waste
36.4%
Figure 3 shows this is greatly reduced for local governments with a three bin system. These
bins held only 5% of garden waste. This is to be expected with the introduction of a green
organics bin.
Figure 3: Garbage bin composition from metropolitan local government with three bin system
Garbage Bin Audits 2008, Metro Councils, 3 Bin System
(n=3)
Aluminium Cans / Foil
0.5%
Total Plastics (1 to 7)
2.3%
Glass
2.9%
Steel Cans
1.4%
Aerosol Cans
0.1%
Total Other
25.8%
Total Paper
12.1%
Nappies / sanitary
2.9%
Garden Waste
5.0%
Prohibited
2.6%
Hazardous
2.2%
Food Waste
42.4%
Kerbside Garbage Composition: Recent Findings
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Review of kerbside bin audits previously undertaken
Sustainability Victoria engaged Hyder Consulting to conduct a desktop analysis of recent
household garbage audits conducted by local governments in metropolitan local government
areas. Twenty audits had been undertaken during 2005 to 2007 using the same approach
and were thus comparable.
Data collected indicated that about 50% of garbage collected consisted of organic waste (+/10%). All figures provided below are by weight. This confirms previous findings that food
waste contributes 41% and organic material (weeds, pruning and lawn clippings) contributes
20% by weight.3
Overall, results showed that two thirds of household garbage was potentially recoverable.
Approximately 15% of material (by weight) was recyclable (paper, plastics, aluminium, steel),
and over 50% could be composted (11% was garden organics and 42% was food organics).
Figure 4 shows the composition by weight of all bin audits undertaken during the 2005-2007
period.
Figure 4: Garbage bin composition from bin audit review
Garbage Bin Audits 2005-2007
(n=20)
Garden organics
11.4%
Total Other
24.5%
Total Paper
8.7%
Total Plastics
2.5%
Aluminium packaging
0.5%
Household hazardous
0.9%
Glass packaging
2.3%
Nappies/ sanitary
5.4%
Steel packaging
1.4%
Food organics
42.4%
Figure 5 shows the composition of the garbage bin stream from metropolitan councils that
used a two bin system from audits conducted during 2005. The recyclables bin used in the
two and three-bin system showed similar compositions apart from the proportion of garden
waste. The packaging waste stream (paper, plastics, aluminium glass and steel) made up
13.5% of the total compared to 15.9% in the three bin system.
3
Beverage Industry Environment Council 1997 National Recycling and Garbage Bin Analysis Recycling and Garbage Audit p.35.
These findings are based on an expanded sampling project conducted by BIEC and EcoRecycle Victoria.
Kerbside Garbage Composition: Recent Findings
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Figure 5: Garbage bin composition from bin audit review: two bin system
Garbage Bin Audits 2 bin systems 2006
(n=4)
Garden organics
18.8%
Total Other
22.8%
Total Paper
7.3%
Total Plastics
2.8%
Household hazardous
0.5%
Aluminium packaging
0.4%
Nappies/ sanitary
4.0%
Glass packaging
1.7%
Steel packaging
1.3%
Food organics
40.2%
As seen in Figure 6, the two bin system had 18.8% of garden waste in the waste stream. This
was more than double that found in the three bin system, which had 9.0% of garden organics.
Figure 6: Garbage bin composition from bin audit review: three bin system
Garbage Bin Audits 3 bin systems 2005-2007
(n=14)
Garden organics
8.8%
Total Other
24.9%
Total Paper
9.4%
Total Plastics
2.4%
Aluminium packaging
0.5%
Glass packaging
2.3%
Household hazardous
1.1%
Steel packaging
1.3%
Nappies/ sanitary
6.1%
Food organics
43.1%
Kerbside Garbage Composition: Recent Findings
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Observations
This review suggested a need for a desktop review of regional waste management practices,
similar to the metropolitan Melbourne desktop review, to gauge if there are significant
differences between regional and metropolitan areas.
A further finding from the study was that approaches towards bin audits vary to such an
extent that only indicative comparisons can be made between datasets. Sustainability Victoria
would benefit from consistent datasets that allow ready comparisons. Best practice guides
have been recently developed in New South Wales4, Western Australia and South Australia5
and a detailed protocol has been developed in New Zealand.6 Anecdotally, local governments
would appreciate guidance on a definitive approach to conducting bin audits to ensure
consistency.
To address the need for a standard methodology, Sustainability Victoria is producing a best
practice bin audit guide which will provide specific advice on sampling, categorisation and
operating procedures. More detailed information on categories and sampling will be
particularly pertinent to bin audits which need to consider specific components of different
waste material.
Conclusions
The 2008 garbage bin audits showed an increase in the proportions of packaging material
with an average of 15.4% to 20.5% in a two bin system and 19.3% in a three bin system. It is
suggested that this increase over previous audit periods of 2005–2007 may be an aberration
due to methodological inconsistencies, such as differing definitions of what constitutes
contaminants in the waste stream. This highlights the need for bin audits to be performed
regularly, using a consistent methodology.
The success in diverting garden waste using a three-bin system has the potential to
be extended to include food organics. The issues surrounding this are discussed in the
recently released Metropolitan Waste and Resource Recovery Strategic Plan.7
These findings were very similar to those of the 20 local government bin audits reviewed.
They clearly demonstrate that local councils can make a significant difference to the recovery
of material for composting and thus their landfill diversion by changing from a two bin to a
three bin system.
Sustainability Victoria is developing guidelines for bin auditing (garbage, recyclables and
green waste). The guideline will provide councils with a standardised and consistent bin
auditing methodology, and improve data collection and comparability. Local governments and
private operators will be able to use this advice on waste auditing methodology to better
analyse the performance of kerbside waste management services. The guide focuses on
weight based physical auditing of kerbside materials.
4
Department of Environment and Climate Change NSW (2008) Guidelines for Conducting Household Kerbside Residual Waste,
Recycling and Garden Organics Audits in NSW Local Government Areas 2007
http://www.environment.nsw.gov.au/resources/warr/200846KerbsideAudits.pdf
5
Zero Waste SA (2007) Guide to Kerbside Performance Reporting http://www.zerowaste.sa.gov.au/kerbside_grants.php
6
New Zealand’s Solid Waste Analysis Protocol http://www.mfe.govt.nz/publications/waste/solid-waste-analysis-mar02/index.html)
7
See Sustainability Victoria’s website for more detail: http://www.sustainability.vic.gov.au/www/html/2408-metropolitan-waste-andresource-recovery-strategic-plan.asp
Kerbside Garbage Composition: Recent Findings
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Appendix One: Explanation of materials classification
Category
Recyclables
Classification
Glass
Description
Brown, green, and clear glass beverage and non-beverage
containers such as beer and wine bottles, jam jars, and
medicine bottles.
PET (1)
Polyethylene terephthalate – clear and/or coloured soft
plastic drink bottles and containers bearing the ‘1’ plastics
identification code or the ‘R’ recycling symbol.
HDPE (2)
High Density polyethylene- containers made from opaque or
solid coloured plastic and bearing the ‘2’ plastics
identification code, such as 2L and 3L plastic milk bottles,
cream and fruit juice containers and detergent bottles.
PVC(3)
Polyvinyl chloride- clear or coloured plastic containers
bearing the ‘3’ plastics identification code, usually sauce or
detergent containers.
LDPE (4)
Low Density polyethylene- plastic items bearing the ‘4’
plastics identification code, usually ice cream container
lids and some food containers.
PP (5)
Polypropylene Plastic containers bearing the ‘5’ plastics
identification code, usually margarine, ice cream or other
food containers.
Polystyrene (6)
Plastics bearing the ‘6’ plastics identification code, excluding
expanded foam, such as meat trays and packaging for
fragile items, but including rigid containers such as for
yoghurt.
Other plastic and
packaging
Any plastic item or container bearing the number ‘7’ or
bearing no plastics identification number. Some
unnumbered items are no doubt made from one of the six
plastics listed above but were not included in that group if
they did not bear the identification number. This group
typically includes scrap plastic, plastic toys, plastic lids and
take away food containers, plastic bags, plastic sheets and
packaging film.
Aluminium cans and Foil
Cans made from aluminium mainly beer and soft drink and
non contaminated foil wrap and food containers
Steel cans
Kerbside Garbage Composition: Recent Findings
Cans made from steel tinplate, mainly food, dog food,
Page 7 of 9
cooking oil and coffee. Also paint cans containing small
amounts of dry paint.
Aerosol cans
Liquid Paperboard (MilkJuice)
Paper and
cardboard
Paper / Newspaper
Pressure packs; does not include pump packs
Gabled and aseptic containers primarily used for milk or fruit
juice.
Recyclable paper including newspaper, coloured advertising
material, magazines, office/computer paper and envelopes.
Cardboard
Includes both flat cardboard such as cereal packets and
corrugated cardboard such as bulk supermarket boxes.
Organics
Garden Waste
Waste that includes trees, shrubs, grass clippings and
prunings.
Food Waste
Organic kitchen waste, including meat and vegetables, meal
preparation scraps, table scraps, spoiled food and fruit.
Disposables
Nappies
Non recyclable hard
plastic
Disposable nappies
Any plastic item not bearing any plastics identification
number. Some unnumbered items are no doubt made from
one of the six plastics listed above but were not included in
that group if they did not bear the identification number. This
group typically includes scrap plastic, plastic toys, plastic lids
and take away food containers.
Non recyclable plastic film
This group typically includes plastic bags, plastic sheets and
packaging film.
Other (specify)
Any material not covered in the above categories. Includes
glass, ferrous, rubber, clothing, (refer list)
Kerbside Garbage Composition: Recent Findings
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Appendix 2: Domestic waste audit data template collection sheet
Weight (g)
Volume (l)
Material classification
RECYCLABLES
Glass
PET(1)
HDPE(2)
PVC(3)
LDPE(4)
PP(5)
PS(6)
Other Plastic(7)
Aluminium Cans / Foil
Steel Cans
Aerosol Cans
Liquid Paperboard
Subtotal Recyclables
PAPER & CARDBOARD
Paper / Newspaper
Cardboard
Subtotal Paper/Newspaper/Cardboard
ORGANICS
Garden Waste
Food Waste
Subtotal Organics
HAZARDOUS
Hazardous Group
Batteries
Subtotal Hazardous
PROHIBITED
Inert
Building Materials (incl. timber)
Subtotal Prohibited
DISPOSABLE
Clothing/Textiles/Fabrics
Nappies
Fluorescent tubes
Non recyclable HARD plastic
Non recyclable plastic FILM
Other …..
Subtotal Disposable
TOTAL
Kerbside Garbage Composition: Recent Findings
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