The Big Compost Experiment
Are Home Compostable Plastics Really Sustainable?
With plastic waste continuing to pollute our planet, many people turn to biodegradable and compostable plastics as an eco-friendly alternative. But do these materials actually break down in home composting systems as intended? A recent study from University College London (UCL), called The Big Compost Experiment, explored this question using citizen science.
What Was the Study About?
The study aimed to assess the effectiveness of biodegradable and compostable plastics in UK home composting conditions. Over 9,700 UK citizens participated in an online survey about their attitudes and behaviours regarding compostable plastics, while 1,648 of them conducted home composting experiments.
Key Findings:
1. Widespread Confusion About Compostable Plastics
Many participants struggled to understand the labels on biodegradable and compostable packaging. About 46% of tested plastic items lacked proper compostability certification, while 14% were certified only for industrial composting—not home composting. 2.
2. Most «Home Compostable» Plastics Did Not Fully Degrade
Of the biodegradable plastics tested in home composts:
- 60% of items labelled “home compostable” did not fully break down
- Only 34% disappeared completely
- 11% broke down into small, but still visible, pieces
3.Composting Conditions Varied, But Results Were Similar
Factors such as the type of compost bin, duration of composting (3–21 months), and geographical location had minimal impact on decomposition rates. This suggests that home composting conditions may not be suitable for breaking down compostable plastics.
What Does This Mean for Sustainability?
- Home composting is not a reliable method for disposing of compostable plastics
- Misleading labelling contributes to consumer confusion
- Better infrastructure is needed, such as industrial composting facilities, to process these materials effectively
The Takeaway
While the idea of compostable plastics sounds promising, they may not be the sustainable solution we hope for—at least not in home composting conditions. Until proper collection and processing systems are established, consumers should be cautious about their choices and dispose of these materials correctly.
Read the full article here:
Purkiss, D., Allison, A.L., Lorencatto, F., Michie, S. and Miodownik, M., 2022. The Big Compost Experiment: Using citizen science to assess the impact and effectiveness of biodegradable and compostable plastics in UK home composting. Frontiers in Sustainability, 3, p.942724. https://doi.org/10.3389/frsus.2022.942724