How compostable packaging can damage the environment

Shoppers trying to do their bit for the environment by reducing plastic consumption could unwittingly be causing more harm than good because of confusion over composting and recycling, scientists believe.

Items in supermarkets are increasingly made of packaging marketed as compostable or biodegradable as the retail sector embraces the green revolution. But ambiguity about what items are suitable for ‘‘green waste’’ and a lack of suitable industrial composting facilities mean many end up in the ground – and could do as much damage to the environment as plastics in the sea.

Dr Olga Pantos, from the Institute of Environmental Science and Research, said many plastics described as ‘‘biodegradable’’ only degraded into smaller microplastics, rather than being broken down biologically into nutrients and carbon that can be re-used in nature.

These tiny plastic particles can end up in the earth, possibly affecting soil and potentially ending up in the food chain. A recent study in Germany found compost from supermarket waste had almost 900 pieces of microplastic in a single 1-kilogram sample.

‘‘Some things in the past that are fully compostable have been described as biodegradable but there is a move towards making a clear distinction between the two,’’ Pantos said.

‘‘Something that’s compostable is biodegradable but something that’s biodegradable isn’t necessarily compostable. Biodegradable bags are made from traditional plastics such as polyethylene but have additives to enable them to degrade – fall apart – into small pieces. So your bag’s not there but the plastic still is; it’s just in such tiny pieces that you can’t see it.’’

Food companies are increasingly using compostable plastics in packaging, from plastic wrap for cheese, chocolate wrappers and coffee cup lids.

Pantos believes there is a lack of clarity and standardisation for consumers, both about what packaging is recyclable or compostable and also where they should put it after use, so too much ends up in the wrong place, causing more environmental harm than good.

While some composting can be done domestically, other items require certain conditions available only through industrial facilities – but there are too few in New Zealand to meet demand.

‘‘Plastics going through the compost into soils, we don’t really know at the moment how much plastic and what types of plastics they are,’’ Pantos said.

‘‘A lot will be from people not realising that the bags they are using to collect their compost in their kitchen is not actually fully properly compostable.

‘‘But then you’ll get other plastics coming through like the stickers on your fruit – these aren’t compostable in New Zealand.’’

While compostable plastics are fundamentally a good idea, Pantos says more is needed to be done to ensure people know what they can compost, how it can be done and for more suitable facilities to be set up.

‘‘We’ve just not got that option for handling the compostable things.

‘‘So it’s just education, and having the option to make sure that it goes in the right direction.’’

‘‘Something that’s compostable is biodegradable, but something that’s biodegradable isn’t necessarily compostable.’’ Dr Olga Pantos, Institute of Environmental Science and Research

Food packaging is increasingly made of material suitable for composting but can do the environment more harm than good.