People should not put biodegradable plastic bags containing garden and food waste into compost, as they may contain chemicals that can only decompose under ideal conditions, a government environmental agency says.
French food and environment agency Anses issued the warning on November 22, as the government prepared to debate a European law on reducing waste.
The warning comes as millions of households in France prepare for new rules on separating food and garden waste that will come into force on January 1, 2024.
Read more: Explainer: Rules for composting in France from January 1
Anses says many biodegradable plastic bags are truly biodegradable using industrial composting methods that operate at higher temperatures than most household compost.
The cooler temperatures of household composts may mean that the bags only partially decompose and may contaminate the soil.
“This contamination can be in the form of various types of materials or microplastics resulting from their decomposition,” Anses science coordinator Stéphane Leconte wrote.
“Residual compounds can be polymers, residual monomers, additives or inorganic cargoes that pose potential hazards to both human health and the environment.”
What are biodegradable plastic bags?
Plastic bags offered as biodegradable come in three forms:
- ‘100% biodegradable‘, can be degraded by bacteria
- ‘Fully compostable‘ can be composted to 90% within 6 months (for industrial composting) or 12 months (for domestic composting) at certain temperatures.
- ‘Made from bio-sourced materials‘, must be made of at least 50% natural material such as corn starch.
While these products may be biodegradable under industrial conditions, they are unlikely to break down consistently in the inconsistent conditions of household composts.
Anses said that the labeling on these materials should be made clearer so that people are not misled.
It was also stated that stricter regulations are required to ensure that they do not contain “endocrine disrupting, carcinogenic, mutagenic or protoxic substances”.
What should people use to store food and garden waste?
Current recommendations from the French Ecological Transformation Agency Ademe are that people should store their waste in brown paper bags or a closed container such as a bin with handle.
Some local authorities will provide single-use biodegradable plastic bags for food and garden waste. However, these bags are not designed for residential composting, but rather to be collected at an industrial composting or biogas facility and then disposed of.
Most households in France are not ready to sort food waste Coming January 1