A study published on May 24, 2023, in the Journal PLOS ONE examined the degradability of biodegradable plastics in a real marine environment. The authors used polylactic acid (PLA) as a biodegradable material. The study focused on PLA in textiles, however, it is the same chemical composition that is used for plastic food contact articles, such as single-use cutlery. For materials to be declared as biodegradable, certain requirements must be met. Yet, the way these requirements are tested oftentimes does not represent actual ecological environments – such as the ocean, where a lot of plastic items will end up. The environment that the materials are tested for resembles more industrial composting settings (FPF reported).
To test environmental degradation, the team led by scientists from the Scripps Institution of Oceanography at UC San Diego submerged pieces of bio-based PLA, as well as oil-based polypropylene (PP) and polyethylene terephthalate (PET) at the sea surface and at 10 m depth for a total of 428 days in a metal cage. The results showed that the purportedly biodegradable PLA, together with the PP and PET, did not show any signs of degradation after the testing period. Inspection with Raman spectra also did not show any chemical changes in the materials. In contrast, natural and regenerated cellulose-based fibers that were tested in the same way degraded completely within approximately 35 days.
Finally, the authors conclude that “referring to compostable plastics as biodegradable plastics is misleading as it may convey the perception of a material that degrades in the environment.” Moreover, the scientists emphasize that the existence of degradable materials should not act as a rationale to continue a destructive and throw-away lifestyle.
For more information about plastics, the difference between bio-based and biodegradable, and the environmental and health impacts of these materials, the Food Packaging Forum has published short fact sheets with concise and scientific information on plastics, bioplastics, and more. Both fact sheets are available in English, French, and Spanish.
Reference
Royer S.-J., Greco F., Kogler M., Deheyn D.D. (2023). “Not so biodegradable: Polyactic acid and cellulose/plastic blend textiles lack fast biodegradation in marine waters.” PLOS ONE. DOI: 10.1371/journal.pone.0284681
Read more
Molly Taft (May 24, 2023). “Yikes: Biodegradable plastic doesn’t actually break down in the ocean.” Gizmodo
