Making packaging greener - biodegradable plastics

Pots you can plant

Another biodegradable plastic product is a plant pot produced by injection moulding. Gardeners and farmers can place potted plants directly into the ground, and forget them. The pots will break down to carbon dioxide and water, eliminating double handling and recycling of conventional plastic containers.

Different polymer blends for different products

Depending on the application, scientists can alter polymer mixtures to enhance the properties of the final product. For example, an almost pure starch product will dissolve upon contact with water and then biodegrade rapidly. By blending quantities of other biodegradable plastics into the starch, scientists can make a waterproof product that degrades within 4 weeks after it has been buried in the soil or composted.

Landfill sites aren't compost heaps

To maximise the benefit of the new bioplastics we’ll have to modify the way we throw away our garbage - to simply substitute new plastics for old won’t be saving space in our landfills.

Although there is a popular misconception that biodegradable materials break down in landfill sites, they don't. Rubbish deposited in landfill is compressed and sealed under tonnes of soil. This minimises oxygen and moisture, which are essential requirements for microbial decomposition. For biodegradable plastics to effectively decompose they need to be treated like compost.

Composting the packaging with its contents

Compost may be the key to maximising the real environmental benefit of biodegradable plastics. One of the big impediments to composting our organic waste is that it is so mixed up with non-degradable plastic packaging that it is uneconomic to separate them. Consequently, the entire mixed waste-stream ends up in landfill. Organic waste makes up almost half the components of landfill in Australia.

By ensuring that biodegradable plastics are used to package all our organic produce, it may well be possible in the near future to set up large-scale composting lines in which packaging and the material it contains can be composted as one. The resulting compost could be channelled into plant production, which in turn might be redirected into growing the starch to produce more biodegradable plastics.

An Olympic effort - recycling 76 per cent of waste

For anyone who thinks such schemes aren’t feasible, you only have to look at the recycling success of the Sydney Olympics to see that where there’s a will, there’s a way. More than 660 tonnes of waste was generated each day at its many venues. Of this, an impressive 76 per cent was collected and recycled. Part of this success was due to the use of biodegradable plastics used in the packaging of fast food, making the composting of food scraps an economic proposition as it eliminated the need for expensive separation of packaging waste prior to processing.

With intelligent use, these new plastics have the potential to reduce plastic litter, decrease the quantities of plastic waste going into landfills and increase the recycling of other organic components that would normally end up in landfills.