The Unchartered Territory of Biodegradable and Compostable Plastics

29th July 2020

In recent years the biodegradable and compostable plastics market has boomed in reaction to the tidal wave of concern around marine plastics and the corresponding commitments from brands. With lots of new materials in circulation, there is now some confusion among stakeholders around how these plastics fit in at a time when we’re trying to reduce our environmental footprint.

Simon Hann, Principal Consultant at independent environmental consultancy Eunomia, recently authored a report for the European Commission reviewing what role these materials can play as we transition to a circular economy, we asked him what those considering using these plastics need to think about.

Putting it into context

Simon said: “Our recent study highlights that the context that compostable plastics are used in often dictates whether they play an environmentally beneficial role. For example, when biowaste bags, made out of a compostable plastic, are used for food waste collection, they increase yields, offer an alternative to plastic bags, and can reduce contamination in processed compost. In this scenario the benefits can often outweigh environmental risks, but this is not always the case. In our report we assessed several product types by developing criteria which showed a sliding scale of products from beneficial to detrimental. Where the material ends up, and what existing waste management infrastructure is available also determines whether it is appropriate. In Italy, for example, the composting industry can accept compostable plastics as the process allows the material to be left to decompose for the required amount of time. Other countries however, apply partially decomposed compost directly to agricultural land – this is fine for organic matter, but less so for the compostable plastics. Unforeseen environmental damage may occur, such as microplastics accumulating in soil and running off into the water courses. Organic waste treatment systems were never designed to process compostable plastics, so many facilities would need significant investment to adapt. We recently completed a review for the Danish EPA assessing the evidence for how these materials interact with their existing set-up— there is no one size fits all.”

Terms and conditions – biodegradable or bio-based?

“There is currently a lot of plastic packaging on the market with various claims and terminology which makes it difficult for consumers to make informed decisions. The difference between compostable and biodegradable for example, is often not made clear to consumers, used interchangeably by brands, with the latter term being meaningless from a waste management point of view. In recognition of this issue the State of California banned the word biodegradable from all packaging in 2017 in order to prevent false and misleading claims with no scientific basis.

To further compound this confusion, plastics made from renewable biomass rather than fossil fuels are known as bio-based plastics (or bioplastic)—these terms have nothing to do with whether a plastic is biodegradable or compostable despite the similarity. With so many names and different, unverifiable claims, it’s easy to see why many consumers feel confused and ill-equipped to make the best choices.

Setting a standard

“Before deciding how we use biodegradable or compostable plastics, we also need to understand some of the potential consequences, including are we encouraging littering by using these products? Are we spreading irretrievably small microplastics across land and subsequently into the sea with no way of knowing if they are harmful? We explore some of this in the Danish EPA report. If we do accept these materials, I think it would be sensible for us to move quickly towards standardisation, funnelling it into good practice, or, legislate against bad applications going onto the market.”

Image courtsey of ACE Solid waste via flikr CC BY 2.0.