Biodegradable or Compostable Plastics and the Transition to a Circular Economy

As part of its Circular Economy Action Plan, the EU Commission has been studying plastic products that are marketed as “biodegradable” or “compostable” and the extent to which these markers signal that these products would be beneficial in the context of transitioning to a circular economy.

The recent report by the EU Commission on the “Relevance of Biodegradable and Compostable Consumer Plastic Products and Packaging in a Circular Economy”, however, has found that there’s weak evidence in favour of the nutritional benefits to soil of products marketed as biodegradable/compostable. In fact, the report concludes that material choices for products should prioritize recyclability over composability (what cities and most in the waste management industry have been saying all along).

Here’s a few of the report’s findings that I thought were interesting and worth sharing:

1.    Soil does not get much, if any, nutritional benefits from the composting of compostable plastics, and at least half of the compostable plastic is lost in the air to CO2 emissions

2.    Most organic waste infrastructure in Europe (anaerobic digestion, in-vessel composting) leads to incomplete biodegradation of these materials, as the composting processes of this infrastructure are shorter than what’s required to biodegrade compostable plastics

3.    There’s a risk that compostable plastics may exacerbate microplastics in soil due to incomplete biodegradation/fragmentation (and, currently, the effects of microplastics in soil are not fully known but are thought to decrease nutrients in the soil due to adverse effects on earthworms and stunt plant growth)

4.    Landfilling of compostable plastics should be avoided to reduce climate change impacts from methane release

5.    If compostable/biodegradable plastics make their way into natural environments, it is likely that they will take a lot longer to biodegrade there (if at all) given that temperatures are lower than at industrial processing facilities or laboratories

6.    Labelling products as biodegradable or compostable may lead to increases in the littering of these products, as consumers may believe that littering these products is unlikely to be harmful to the natural environment

Overall, the report comes to the conclusion that “[t]here appears to be no evidence to suggest that home compostable plastic material itself provides any specific benefits to the home compost and in the context of the circular economy, the material is essentially lost”.