The growing use of biodegradable plastics will not significantly decrease the volume of plastic entering the world’s oceans or the physical and chemical risks that plastics pose to the marine environment, a new report by the United Nations says.
The report, entitled “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.
“Recent estimates from the UN Environment Programme (UNEP) have shown as much as 20 million tonnes of plastic end up in the world’s oceans each year,” said UNEP’s Executive Director Achim Steiner in a statement. “Once in the ocean, plastic does not go away, but breaks down into microscopic 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 is produced globally each year and only a very small percentage is recycled. Instead, some of that plastic ends up in the world’s oceans, costing several billion dollars annually in environmental damage to marine ecosystems.
According to the new UN report, plastics most commonly used for general applications, such as PE, PP, and PVC – which biodegrade under favorable conditions on land (in soil, landfill, or a composter) – are much slower to break up in the ocean, and sometimes are not biodegradable at all.
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.
The report also cites research that suggested some people are attracted by “technological solutions” as an alternative to changing behavior. “Labeling 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 report said.
“On the balance of the available evidence, biodegradable plastics will not play a significant role in reducing marine litter,” the report concluded.