5 things you may not know about biodegradable plastics

There has been a lot of debate in the media about biodegradable plastics – that’s because not all of these plastics are created equal, and some can have an adverse impact on nature especially if they don’t end up in the environment they are designed to break down in.

This is a particular issue in New Zealand, as we don’t yet have the nationwide infrastructure to ensure that commercially compostable plastics are collected and sent to commercial composting facilities to be processed in the right way. Compostable plastics are one type of biodegradable plastic and may either be commercially compostable or home compostable.

Here are 5 facts on biodegradable plastics that you may not know:

1. Not all biodegradable plastics are made from bio-based materials

Some biodegradable materials are made from plants. Others are made from petrochemical resources.

This diagram plots different plastics on axis. It shows non-biodegrable and biobased plastics (eg biobased PE, PET, PTT as biobased and non-biodegradable; Biodegradable and biobased plastics eg, PLA, PHA, PBS and starch blends as biobased and biodegradable; Conventional plastics eg, PE, PP, PET as non biodegradable and fossil based; Biodegradable and fossil based plastics eg, PBAT, PCL as biodegradable and fossil based

2. Biodegradable plastics do not all break down the same way.

There are a range of different biodegradable plastics and these break down at different rates depending on the environment they end up in. Factors like temperature, moisture and the presence of oxygen has a big impact on the rate at which microbes are able to consume the material. This means that materials which are designed to be processed in industrial composting facilities will not necessarily degrade in soil or marine environments.

3. Not all compostable materials will break down in a home compost.

Commercial composting systems are able to consistently operate at higher temperatures than home composting. This is due to their scale and better air flow. Some compostable plastics need to be held at a higher temperature in order to start the biodegradation process. If a plastic item is certified commercially compostable you will need to check if there is a commercial composting facility in your area that will accept it. If plastic is certified home compostable it can be composted at home.

4. Biodegradable plastics cannot be recycled in NZ.

Biodegradable plastics are designed to break down or ‘degrade’ which means they can’t be recycled in our current recycling systems in New Zealand. Never put these plastics in your recycling bin!

5. Reusable plastics are more environmentally friendly than biodegradable plastics

Having an item like a reusable water bottle or keep cup that can be used over and over again is generally a much better choice for nature than using an item once (single-use) even if it’s certified compostable. Keen to learn more about biodegradable plastics? The Parliamentary Commissioner for the Environmental recently released online resources to help New Zealanders navigate these plastics and make informed choices.

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5 things you may not know about biodegradable plastics