Publications

Biodegradable Plastics - Developments and Environmental Impacts

Nolan-ITU Pty Ltd
Prepared in assocation with ExcelPlas Australia
October, 2002

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Executive Summary

Biodegradable plastics are a new generation of polymers emerging on the Australian market. Biodegradable plastics have an expanding range of potential applications, and driven by the growing use of plastics in packaging and the perception that biodegradable plastics are 'environmentally friendly', their use is predicted to increase. However, issues are also emerging regarding the use of biodegradable plastics and their potential impacts on the environment and effects on established recycling systems and technologies.

Environment Australia, in consultation with the Plastics and Chemicals Industries Association (PACIA) has engaged Nolan-ITU, in association with ExcelPlas Australia, to undertake a national review of biodegradable plastics with the primary aim of identifying and characterizing emerging environmental issues associated with biodegradable plastics to assist industry and the Commonwealth to develop initiatives to address these issues effectively.

Terms of Reference

The Terms of Reference of the review are to identify issues of relevance including the following:

1. Identify the various types and composition of biodegradable plastics available, and likely to be available in Australia.
2. Identify standards and test methods for biodegradable plastics in Australia.
3. Examine the range of disposal methods and identify the most frequent disposal option for each biodegradable plastic application at end of life.
4. Identify current technologies to avoid contamination and sort biodegradable plastics in Australia and overseas.
5. Describe and assess the current and potential future environmental impacts arising from the foreseeable increase in use of biodegradable plastics in various applications.
6. Identify possible and existing solutions to identified impacts and limitations.

Key Findings

The range of biodegradable plastics available include:

• Starch based products including thermoplastic starch, starch and synthetic aliphatic polyester blends, and starch and PVOH blends.
• Naturally produced polyesters including PVB, PHB and PHBH.
• Renewable resource polyesters such as PLA.
• Synthetic aliphatic polyesters including PCL and PBS.
• Aliphatic-aromatic (AAC) copolyesters.
• Hydro-biodegradable polyester such as modified PET.
• Water soluble polymer such as polyvinyl alcohol and ethylene vinyl alcohol.
• Photo-biodegradable plastics.
• Controlled degradation additive masterbatches.

There is a extensive range of potential applications. Some of these include:

• Film including overwrap, shopping bags, waste and bin liner bags, composting bags, mulch film, silage wrap, body bags/coffin liners, landfill covers, packaging - incl.O₂ & H₂O barriers, bait bags, nappy backing sheet, and cling wrap.
• Flushable sanitary products.
• Sheet and non woven packaging.
• Bottles.
• Liquid paper board.
• Planter boxes and fishing nets.
• Food service cups, cutlery, trays, and straws.
• Loose fill foam.

Whilst several biodegradable plastics are used for these applications in Europe, the current market penetration into Australia is low.

Several standards and test methods apply to biodegradable plastics internationally, however here are currently no Australian standards and test methods for biodegradable plastics. There is a need to establish Australian Standards that match the potential application areas and disposal environments in Australia.

The major potential disposal environments for biodegradable plastics are:

• composting facilities or soil burial;
• anaerobic digestion;
• wastewater treatment facilities;
• plastics reprocessing facilities;
• landfill;
• marine and freshwater environments; and
• general open environment as litter.

To a large extent, the nature of the biodegradable plastic application should dictate the disposal environment.

The risk of contamination by biodegradable plastics of conventional plastics which are currently recycled and reprocessed is a significant one, and the resultant effects on recyclate has the potential to undermine the growing confidence in recycled plastics. Effective methods for sorting biodegradable plastics would be needed in the event of their significant entry into the Australian market. Possible methods include near infra-red detection, which can be used in a positive sort system, or the use of a specific polymer code, and even colour, to differentiate biodegradable polymers from other recyclable polymers.

There are several identifiable environmental benefits that may potentially be derived from the use of biodegradable plastics compared to conventional petroleum-based plastics. These are:

• Compost derived in part from biodegradable plastics increases the soil organic content as well as water and nutrient retention, while reducing chemical inputs and suppressing plant disease.
• Biodegradable shopping and waste bags disposed of to landfill may increase the rate of organic waste degradation in landfills while enhancing methane harvesting potential and decreasing landfill space usage. Biodegradable landfill covers may also considerably extend landfill life.
• The energy required to synthesise and manufacture biodegradable plastics is generally much lower for most biodegradable plastics than for non-biodegradable plastics. The exception is PHA biopolymers which consume similar energy inputs to polyethylenes. New feedstock for PHA should lower the energy required for their production.
• Biodegradable plastics also offer important environmental benefits through, in many cases, the use of renewable energy resources and reduced greenhouse gas emissions.

Biodegradable plastics also pose some adverse environmental risks. These include:

• Pollution in waterways due to high BOD concentrations resulting from the breakdown of starch-based biodegradable plastic.
• Migration of plastic degradation by-products, (such as plastic residuals, additives and modifiers such as coupling agents, plasticisers, fillers, catalysts, dyes and pigments), via run-off and leachate from landfills and composting facilities to groundwater and surface water bodies.
• Trauma and death of marine species resulting from only partial or slow degradation of biodegradable plastic products in marine environments.
• Possible increase in the incidence of littering due to the belief that biodegradable plastics will disappear quickly.
• Soil and crop degradation resulting from the use of compost that may have unacceptably high organic and or metal contaminants derived from biogegradable plastic residuals, additives and modifiers such as coupling agents, plasticisers, fillers, catalysts, dyes and pigments.

Key Recommendations

For the successful introduction of degradable plastics into Australia it is essential that for any new application that the following are clearly identified:

• disposal route;
• appropriate recovery systems;
• processing infrastructure required; and
• the product has been tested against nationally agreed standards to ensure that the disposal route is appropriate and is environmentally sustainable.

For this to be achieved it will be necessary to establish a national framework for standards and testing. This can be based upon appropriate international standards. It is recommended that the Federal Government, through Environment Australia and in consultation with the plastics industry, take an initiating role in undertaking further research and developing these standards.

Further research focus areas include:

• Life-cycle assessment;
• Minimisation of the impacts on reprocessing;
• Determination of appropriate disposal methods; and
• Consumer education.