Biodegradable and compostable plastics

The Ministry recommends reusable bags over single-use plastic bag alternatives marketed as compostable or biodegradable. These alternatives can be harmful to nature if they are not processed properly.

What is biodegradable plastic?

Biodegradable plastic is plastic that will break down through the action of living organisms, usually microbes. To fully break down, biodegradable plastics require the right environment, which usually means commercial processing.

If biodegradable plastic is left to break down in a natural environment – such as in landfills or the sea – it often only breaks down into micro-plastics. These micro-plastics can create ‘plastic smog’ in parts of the ocean and accumulate in soils.

What is compostable plastic?

Compostable plastic is plastic that will break down entirely into its nutrients and natural substances (ie, return to nature). Compostable is a subset of biodegradable.

We recommend that you read the label to determine if a compostable item is designed to break down in a typical compost bin. There are few standards relate to home composting environments.

Most compostable plastics are designed to break down in a commercial compost and may not break down in a natural environment. If it is labelled as commercially compostable, we recommend you only buy the item if you have access to a local commercial compost collection service.

Collection and processing of biodegradable and compostable plastics

The majority of New Zealanders do not have access to systems that collect and process biodegradable plastics properly.

If disposed to landfill biodegradable plastic is likely to produce methane, a known greenhouse gas.

Don’t put biodegradable and compostable plastics into soft plastic or kerbside recycling

They are not designed to be processed by recycling facilities that deal with all other plastics.

Find out more

For more information on biodegradable and compostable plastics see the detailed resource on the Parliamentary Commissioner for the Environment’s website.

Reviewed:
08/08/18