Widespread adoption of products labelled ‘biodegradable’ will not significantly decrease the volume of plastic entering the ocean or the physical and chemical risks that plastics pose to marine environment, concluded a UN report released today.

The report, “Biodegradable Plastics and Marine Litter. Misconceptions, Concerns and Impacts on Marine Environments”, finds that complete biodegradation of plastics occurs in conditions that are rarely, if ever, met in marine environments, with some polymers requiring industrial composters and prolonged temperatures of above 50°C to disintegrate. There is also some limited evidence suggesting that labelling products as ‘biodegradable’ increases the public’s inclination to litter.

The report finds that plastics most commonly used for general applications, such as polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC) are not biodegradable in marine environments. Polymers, which biodegrade under favourable conditions on land, are much slower to break up in the ocean and their widespread adoption is likely to contribute to marine litter and consequent undesirable consequences for marine ecosystems.

The study also analyzes the environmental impacts of oxo-degradable plastics, enriched with a pro oxidant, such as manganese, which precipitates their fragmentation. It found that in marine environments the fragmentation is fairly slow and can take up to 5 years, during which the plastic objects continue to litter the ocean.

Oxo-degradable plastics can pose a threat to marine ecosystems even after fragmentation. The report says it should be assumed that microplastics created in the fragmentation process remain in the ocean, where they can be ingested by marine organisms and facilitate the transport of harmful microbes, pathogens and algal species.

The report also cites research that suggested some people are attracted by ‘technological solutions’ as an alternative to changing behaviour. Labelling a product as biodegradable may be seen as a technical fix that removes responsibility from the individual, resulting in a reluctance to take action.

Sources: The United Nations Environment Programme