You may have noticed the plastic bags with ‘biodegradable’ or ‘compostable’ written on them (usually in green colour). A new study unveiled the disheartening truth of the not-so-degradable plastic bags which are falsely advertised as compostable and biodegradable.
A report published in Environmental Science & Technology describes an experiment by researchers at the University of Plymouth, who sought to find out how five different types of plastic behaved in various environments over time.
Research fellow Imogen Napper and Richard Thompson, a marine biologist and head of the university’s International Marine Litter Research Unit, tested conventional plastic bags, compostable bags, biodegradable bags and two types of oxo-biodegradable bags (bags that do not need microorganisms to decompose).
This study examined the materials over a 3 year period. These materials were exposed in three natural environments; open-air, buried in soil, and submerged 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.
It claimed “…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.”
“I was really amazed that any of the bags could still hold a load of shopping,” says Napper. “For a biodegradable bag to be able to do that was the most surprising. When you see something labeled in that way, I think you automatically assume it will degrade more quickly than conventional bags. But, after three years at least, our research shows that might not be the case.”
One way to counteract the negative effects of plastic bags’ persistence in the environment might be to capitalize on their longevity by using them multiple times. “Perhaps durability in the form of a bag that can and is reused many times,” the study authors write, “presents a better alternative to degradability.”