UNReportA UN report, “Biodegradable Plastics and Marine Litter: Misconceptions, Concerns and Impacts on Marine Environments,” argues that the adoption of plastic labelled as ‘biodegradable’ will not bring about a significant decrease either in the quantity of plastic entering the ocean or the risk of physical and chemical impacts on the marine environment, on the balance of current scientific evidence.

The objective of the UN briefing paper was to provide a concise summary of some of the key issues surrounding the biodegradability of plastics in the oceans, and whether the adoption of biodegradable plastics will reduce the impact of marine plastics overall. According to the paper, it has been suggested that plastics considered to be ‘biodegradable’ may play an important role in reducing the impact of ocean plastics. Labelling a product as biodegradable may be seen as a technical fix that removes responsibility from the individual.

However, polymers which will biodegrade in the terrestrial environment, under favorable conditions (e.g. AcC, PBS, PCL, PES, PVA), also biodegrade in the marine environment, but much more slowly and their widespread use is likely to lead to continuing littering problems and undesirable impacts.

A further disadvantage of the more widespread adoption of ‘biodegradable’ plastics is the need to separate them from the non-biodegradable waste streams for plastic recycling to avoid compromising the quality of the final product.

The inclusion of a pro-oxidant, such as manganese, in oxo-degradable polymers is claimed to promote fragmentation by UV irradiation and oxygen. The fate of these fragments (microplastics) is unclear, but it should be assumed that oxo-egradable polymers will add to the quantity of microplastics in the oceans, until overwhelming independent evidence suggests otherwise. Oxo-degradable polymers do not fragment rapidly in the marine environment (i.e. persist > 2-5 years) and so manufactured items will continue to cause littering problems and lead to undesirable impacts.

The study states that some of the claims and counter-claims about particular types of polymer, and their propensity to biodegrade in the environment, appear to be influenced by commercial interests. Some evidence albeit limited suggests that public perceptions about whether an item is biodegradable can influence littering behavior; i.e. if a bag is marked as biodegradable it is more likely to be discarded inappropriately.

The report was commissioned by the Global Programme of Action for the Protection of the Marine Environment from Land-based Activities (GPA).

For the full report please click here