Compostable Plastics and Other Confusing Terms

It is important to understand what these terms mean if you want to be able to make an informed choice and avoid greenwashing. The choice of preferable single-use packaging depends on where you will put it at the end of its life. In order of preference, the choice is recycling, composting then landfill.

There are some applications where recycling is difficult. This is particularly the case where the packaging is contaminated by food waste. In which case, composting is preferable to landfill. But don’t be fooled by the terms used. If the packaging is going to be composted, it needs to be certified as meeting the requirements of one of the standards below.

We have summarised some of the terms that often cause confusion.

Bioplastic, or bio-based plastic

These are plastics produced from natural origins, such as plants, animals, or micro-organisms. This organic material can be used to produce several different types of plastics. Because the raw materials are extensively modified in the production of the plastic, sometimes with the addition of non-organic additives, these plastic may not be biodegradable.

You can make both PE (polyethylene) and PET plastics from plant materials. These are the same as the products made from petrochemicals and can be recycled in the same way. Although made from plants these are not biodegradable.

Biodegradable Plastic

A biodegradable plastic is one that will biodegrade.

This means it will break down into CO2, water, and residual organic material with the help of microorganisms. The process depends on the conditions (e.g. location, temperature, humidity, presence of microorganisms, etc.) of the specific environment (industrial composting plant, garden compost, soil, water, etc.) and on the material or application itself. Consequently, the process and its outcome can vary considerably.

Compostable Plastic

This signifies that under “composting” conditions the plastic will biodegrade.

For this term to really mean anything the conditions need to be specified, and the product needs to break down within a certain time period under these conditions. Hence products must be certified against one of two Australian Standards:

• AS 5810-2010, for products that will break down in industrial composting, where relatively high temperatures are reached.

• AS 4736‐2006, for products that will break down in home composting. Where temperatures reached are much lower.

Even plastics certified as home compostable will break down very slowly if left in the environment, rather than in the compost bin. And if placed in landfill the decomposition will be extremely slow because of the lack of oxygen. And of course, a waste of resources.

Oxo-degradable Plastic

These are conventional plastics mixed with an additive which causes plastic to break down in the environment into smaller and smaller pieces, eventually becoming microplastics.

We do not support the use of oxo-degradable plastics in packaging as they are neither recyclable or compostable.



Wendy Chapman is the Business Development Manager at Clean Up Australia. She is passionate about helping individuals and businesses take the lead on sustainability issues.

Resources

Australasian Bioplastics Association

Ellen Macarthur Foundation Oxo Statement