Proscrire les matières plastiques du compost domestique
29/11/2022
Expert assessment
2 mins

Plastics are not compatible with domestic composting

More than one in three French people recycle their waste in garden or community composters. In addition to putting vegetable peels and scraps in them, some people add plastic waste, in particular “biodegradable” or “compostable” single-use plastic bags. And yet the total degradation of such plastics is not guaranteed in these composters, which means that use of the resulting compost can pose a risk to humans and the environment. ANSES therefore recommends not placing any plastics in garden composters.

What are biosourced, biodegradable and compostable plastics?

Some of the plastic packaging and consumer goods available on the market are marked as "biosourced", "biodegradable" or "compostable". These terms can be confusing as they refer to different concepts.

  • “Biosourced” plastics are made from natural resources such as corn starch, although the level of these resources varies, with no minimum requirement. Single-use plastics must have a natural content of least 50%.
  • Plastics are said to be "biodegradable" if they are degraded by microorganisms.
  • “Compostable" plastics are biodegradable plastics that degrade in specific industrial or domestic composting conditions (temperature, humidity). According to current standards, these plastics must degrade by more than 90% within a maximum period of six or 12 months, depending on whether they are composted industrially or domestically.

Even “biodegradable” plastics are a potential source of pollution

Even for plastics claiming to be biosourced, biodegradable or compostable, there is no guarantee that they will completely degrade in garden composters, whose parameters are difficult to control. Therefore, when an individual adds compost to their vegetable garden, for example, possible contamination of the environment or local crops cannot be ruled out.

“This contamination can result from the various components of the plastics, or from microplastics produced during their degradation. The components in question may be polymers, residual monomers, additives or inorganic fillers posing potential risks to both human health and the environment" explains Stéphane Leconte, coordinator of the expert appraisal at ANSES.

ANSES therefore recommends not placing any plastics, even those labelled as "biodegradable" and/or "compostable", in garden or community composters.

Favouring industrial composting for all plastics

To minimise environmental contamination, ANSES recommends collecting, sorting and/or processing biosourced, biodegradable and compostable plastics through industrial channels, as is practised for all other packaging.

Moreover, to prevent any reference or encouragement to adding plastics to garden compost, ANSES recommends amending the regulations.  

Reviewing the composting standards and applying them more broadly

ANSES also advises reviewing the system regulating industrial and domestic composting.

It suggests introducing a single standard, including an assessment of biodegradability in all environmental media, and setting more stringent criteria such as the absence of endocrine disruptors and carcinogenic, mutagenic or reprotoxic substances.

The Agency recommends making it mandatory to implement this new standard on the composting of plastic products and articles claiming to be biodegradable or compostable in all sectors using them, not just the packaging sector.