The University of Plymouth International Marine Litter Research Unit have conducted research which contradicts the belief that biodegradable plastics can reduce ocean plastic pollution.
There is clear evidence that discarded single-use carrier bags are accumulating in the environment. As a result, various plastic formulations have been developed which state they deteriorate faster and/or have fewer impacts on the environment because their persistence is shorter. This study examined biodegradable, oxo-biodegradable, compostable, and high-density polyethylene (i.e., a conventional plastic carrier bag) materials over a 3 year period. These materials were exposed in three natural environments; open-air, buried in soil, and submersed in seawater, as well as in controlled laboratory conditions. In the marine environment, the compostable bag completely disappeared within 3 months. However, the same compostable bag type was still present in the soil environment after 27 months but could no longer hold weight without tearing. After 9 months exposure in the open-air, all bag materials had disintegrated into fragments. Collectively, our results showed that none of the bags could be relied upon to show any substantial deterioration over a 3 year period in all of the environments. It is therefore not clear that the oxo-biodegradable or biodegradable formulations provide sufficiently advanced rates of deterioration to be advantageous in the context of reducing marine litter, compared to conventional bags.