Page 85 - Materials Chemistry, Second Edition

Life Cycle Assessment: Principles, Practice and Prospects
72
one year compared with 520 bags in the single-use scenario). Clearly, the impacts of the Kraft
paper bag are halved if the bag is used twice by the consumer.
The single-use bags produce more litter due to the higher incidence of them being littered
compared with reusable bags (Fig. 6.12). The marine biodiversity category is mostly affected by
the propensity of the material to float or sink. Higher impacts are modelled in the marine bio-
diversity category if the material floats, as it is assumed to float for six months (three months
for the oxo-biodegradable bag). If it sinks, the material is assumed to sink over the course of
one day.
Polymer-based reusable bags have less environmental impacts than all of the single-use
bags. Degradable bags have similar greenhouse gas and eutrophication impacts to conventional
HDPE bags. If the degradable material can be kept out of landfill and managed through com-
posting, the greenhouse gas impacts will be reduced but not eliminated. The synthetic polymer
bags have greater effects on resources (abiotic depletion). In the study, indicators for litter are
developed in an attempt to represent some of the damage effects caused by litter. Litter impacts
are lowest for the reusable bags, but of all the single-use bags, the biodegradable ones generally
produce fewer emissions, although in the marine environment, it is the density of the material
that dominates the impact rather than degradability.

6.3 Conclusions
The first three case studies all indicate that dry material recycling is associated with improved
environmental performance. There is an overall benefit from source-separated aerobic or
anaerobic management of organic waste, for which most environmental categories show an
improvement over conventional landfill. Generally, landfill performs the worst of all technolo-
gies in relation to resource depletion, photochemical oxidation, water toxicity and greenhouse
gas emissions.
All of the case studies presented indicate the importance of carefully designed goal and
scope, assumptions and methodology in waste LCA. There is significant potential for changes
in assumptions to affect end results; for instance, recovery rates of materials in the recycling
system or the degradation rates of organic materials in anaerobic environments. Some form of
sensitivity analysis is important wherever there is significant uncertainty in key assumptions.
Methodological and technical considerations aside, the application of LCA has been suc-
cessful in significantly influencing waste management policy in Australia. For example, in
relation to the first case study, the equivalency factors generated have been used by Sustainabil-
ity Victoria (formally EcoRecycle Victoria) to report the benefits of recycling in the Annual
Survey of Victorian Recycling Industries reports. The second case study provided input into the
National Packaging Covenant, and the third case study on alternative waste treatment technol-
ogies was used in the development of Victoria’s solid waste strategy: Towards Zero Waste.
The application of LCA has also shown that recycling generally makes good environmental
sense, while also challenging the notion that biodegradable polymer or paper-based materials
are ‘better’ than petroleum-based plastics. Indeed, in the case of shopping bags only multi-use
bags are likely to outperform ‘traditional’ lightweight HDPE bags. Nevertheless, there remain
significant environmental problems associated with the generation and management of waste,
and LCA can be expected to continue to assist in identifying both intuitive and counter-intui-
tive performance aspects of different waste questions over the coming years and decades.

6.4 References
ABS (1996) Australians and the Environment. Australian Bureau of Statistics, Commonwealth
of Australia, Canberra.

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