A new United Nations report has concluded that 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.
The report, Biodegradable Plastics and Marine Litter. Misconceptions, Concerns and Impacts on Marine Environments, found that complete biodegradation of plastics occurred in conditions that are rarely, if ever, met in marine environments.
The report added that some polymers required industrial composters and prolonged temperatures of above 50 degrees Celsius to disintegrate.
There was also limited evidence suggesting that labelling products as ‘biodegradable’ increased the public’s inclination to litter.
The report was launched to mark the 20th anniversary of the Global Program of Action for the Protection of the Marine Environment from Land-based Activities (GPA), an intergovernmental mechanism hosted by the United Nations Environment Program (UNEP).
UNEP Executive Director Achim Steiner said, “Recent estimates from UNEP have shown as much as 20 million tonnes of plastic end up in the world’s oceans each year.
“Once in the ocean, plastic does not go away, but breaks down into microplastic particles.
“This report shows there are no quick fixes, and a more responsible approach to managing the lifecycle of plastics will be needed to reduce their impacts on our oceans and ecosystems.”
In 2014, a study by UNEP and partners estimated that about 280 million tonnes of plastic was produced globally each year and only a very small percentage was recycled.
Instead, some of that plastic ended up in the world’s oceans, costing several billion dollars annually in environmental damage to marine ecosystems.
In recent years, concern has grown over microplastics (particles up to 5mm in diameter, either manufactured or created when plastic breaks down).
Their ingestion has been widely reported in marine organisms, including seabirds, fish, mussels, worms and zooplankton.
The new report aimed to verify a thesis that plastics considered ‘biodegradable’ may play an important role in reducing these negative environmental impacts.
The report found that plastics most commonly used for general applications, such as polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC) were 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 analyses 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 was fairly slow and could take up to five years, during which the plastic objects continued to litter the ocean.
Oxo-degradable plastics can pose a threat to marine ecosystems even after fragmentation.
The report said it should be assumed that microplastics created in the fragmentation process remain in the ocean, where they could be ingested by marine organisms and facilitate the transport of harmful microbes, pathogens and algal species.
The report also cited research that suggested some people were 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.
The full report can be downloaded at: http://unep.org/gpa/documents/publications/BiodegradablePlastics.pdf
