An article published on April 28, 2019 in the peer-reviewed journal Environmental Science & Technology reported on a long-term study of degradation behavior of single-use carrier bags made of different plastic formulations. Imogen Napper and Richard Thompson from the International Marine Litter Research Unit, School of Biological and Marine Sciences, University of Plymouth, UK, examined bags labeled as “biodegradable, oxo-biodegradable, [or] compostable” as well as a “conventional plastic carrier bag” made of high-density polyethylene. The bags were placed into three natural environments, i.e. “open-air, buried in soil, and submersed in seawater” or into “controlled laboratory conditions,” and followed over a three-year period.
The compostable bag “disappeared” after three months in the sea, but still persisted in other environments after 27 months. After nine months of exposure in the open-air, “all bag materials had disintegrated into fragments,” however, “none of the bags could be relied upon to show any substantial deterioration . . . in all of the environments” over a three-year period, the authors said. For example, both a conventional plastic bag and bags labeled as biodegradable were still able to carry a load of grocery shopping after being in seawater for three years. Based on their findings, Napper and Thompson concluded that it is “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.” Summarized in an article by EcoWatch, Thompson commented that “it is important that the right bag is matched to the situation in which it is most likely to be disposed of in an environmentally friendly way.” Therefore, “a bag that can and is reused many times presents a better alternative to degradability.”
In a press release published on April 30, 2019, industry association European Bioplastics (EuBP) commented that the “University of Plymouth study misleads on value of biodegradable and compostable plastics” and criticized the selection of the particular products used in the study. Francois de Bie, Chairman of EuBP, further pointed out that “the study confirms that only certified biodegradable and compostable bags . . . have a reduced environmental impact.” An article in The Guardian emphasized that a widespread availability of opportunities for correct end-of-life management (e.g., dedicated collection for industrial composting) would be key to unlocking the full benefits of biodegradable materials. However, such facilities are still underdeveloped in most locations.
Allan Williams (April 29, 2019). “Biodegradable bags can hold a full load of shopping three years after being discarded in the environment.” University of Plymouth
Sandra Laville (April 29, 2019). “’Biodegradable’plastic bags survive three years in soil and sea.” The Guardian
European Bioplastics (April 30, 2019). “University of Plymouth study misleads on value of biodegradable and compostable plastics.”
Olivia Rosane (April 30, 2019). “Biodegradable bags buried for 3 years still work.” EcoWatch
Packaging Europe (May 1, 2019). “New study ‘misleads on value of biodegradable and compostable plastics.’”
Plastics News Europe (May 2, 2019). “EUBP says UK study on plastic bag decomposition ‘misleading.’”
European Bioplastics (May 23, 2019). “The debate: Biodegradable and compostable plastic bags.”
Napper, I.E., and Thompson, R.C. (2019). “Environmental deterioration of biodegradable, oxo-biodegradable, compostable, and conventional plastic carrier bags in the sea, soil, and open-air over a 3-year period.” Environmental Science & Technology (published April 28, 2019).