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Degradable Plastics
If you have another question please email plastics@environment.gov.au or phone Angela Gillman on (02) 6274 1902.
Are biodegradable plastic bags a solution to the plastic carry bag problem?
Biodegradable plastics are seen by many as a promising solution to the problem of single-use conventional plastic bags. Although there are a variety of degradable plastics, which may assist reducing the resource inefficiency and litter problems associated with plastic carry bags, there is unfortunately no easy solution.
For example, in accordance with the waste hierarchy - 'Refuse, Reduce, Reuse, Recycle' - the best thing is to avoid using any sort of disposable bags (including degradable bags) in the first place. Life-cycle assessments undertaken for our report The Impact of Degradable Plastic Bags in Australia showed that reusable bags have a lower environmental impact than either conventional or degradable single-use bags. We therefore recommend you remember to take along a reusable bag and that you use fewer disposable bags. If you forget, at least try and reuse the bags you get for a few more shopping trips or as bin liners.
The degradable versus conventional plastic bag argument is very complex. Some question whether there is any benefit in using degradable plastic bags if they are just going straight to landfill, as they may not break down in the dry anaerobic conditions found in most Australian landfills. Alternatively if they do break down they may contribute to the generation of methane, which is a potent greenhouse gas (although if methane capture technologies for energy generation are in place at the landfill this may not be such a problem). The impact of degradable plastic bags on recycling programs for conventional plastics still requires further research. Generally it is feared that contamination of recycling processes with degradable plastics may interfere with the recycling processes and undermine the durability of the recycled plastics products produced.
As far as litter goes, you shouldn't litter any bag, even if it is degradable. This is because bags can travel great distances on the wind and you don't know where they'll end up. Depending on where they land, the bags may take a long time to fully degrade. They may not be exposed to soil microorganisms which assist breakdown if caught in a tree. Even bags exposed to soil may still not receive the right conditions to enable them to quickly break down.? ). Taking greater care and reducing the use of disposable plastic bags in the first place is the best way to avoid litter. More information on plastic bags.
Will degradable plastics break down in landfill?
Our consultancy report, The Impact of Degradable Plastic Bags in Australia, found that there is probably little benefit obtained by using biodegradable plastics if you dispose of them to landfill. This is because microorganisms cannot survive the dry, oxygen-deprived conditions normally found in landfills.
All sorts of biodegradable materials, including food and paper, have been found 'mummified' and preserved in such conditions. Even if the biodegradable materials do degrade, the low oxygen levels mean that they can release methane as they break down - a potent greenhouse gas. If the methane is captured and used for energy, this is not such a problem.
Normally the main problems to be resolved in landfill are the volumes of waste and toxicity of the materials. Plastic bags and films that are most commonly replaced by degradable plastics actually make up a small amount (by volume) of the waste going to landfill, and most plastics are inert and do not contribute to toxic emissions or leachate.
The role of degradable plastics in landfill is a complex issue subject to ongoing debate. Bioreactor or wet landfills are designed to encourage the break down of organic matter and capture the methane emitted for energy generation. Contrastingly, many local governments are now trying to keep organic matter out of landfills) through collecting garden and food waste and then composting it. Degradable plastic bags are increasingly popular overseas to make food scrap collection more convenient.
There are also resource efficiency issues associated with waste generally. The best action you can take is to refuse, reduce, reuse and recycle. Recycling conventional plastics or composting biodegradable plastics are other ways to improve resource efficiency.
Further FAQs are under development, please visit again soon.