Biodegradable bags aren’t so biodegradable after all, according to researchers from the International Litter Research Unit of the University of Plymouth (UK). Professor Richard C. Thompson and Research Fellow Imogen E. Napper examined the degradation of five plastic bag materials widely available from retailers in the UK, according to a release from the University of Plymouth. The bags were left exposed to air, soil and sea environments, which could be encountered if discarded as litter.
The bags were monitored at regular intervals, and deterioration was considered in terms of visible loss in surface area and disintegration as well as more subtle changes in tensile strength, surface texture and chemical structure. It turned out that the biodegradable, oxo-biodegradable and conventional plastic formulations remained functional as carrier bags after being in the soil or marine environments for over three years.
“After three years, I was really amazed that any of the bags could still hold a load of shopping," said 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.”
That raises the question of whether biodegradable formulations can be relied upon to offer a sufficiently advanced rate of degradation [and be a] realistic solution to the problem of plastic litter, said the university’s report.
The compostable bag completely disappeared from an experimental text rig in the marine environment within three months; however, while showing some signs of deterioration, it was still present in soil after 27 months, said the news release.
European Bioplastics association questions biodegradability study methods
A response to the report came from European Bioplastics (EUBP), the European association representing the interests of the bioplastics industry and its value chain. “Contrary to what the headlines of some newspaper reports picking up the findings suggest, the study confirms that only certified biodegradable and compostable bags—designed to be collected with bio-waste and organically recycled in dedicated composting plants—even if mistakenly littered in the environment due to bad habits, have a reduced environmental impact,” said François de Pie, Chairman of EUBP. “While no plastic bag should end up in the environment, period, at least it is clear that certified compostable ones will not need decades to degrade, as conventional plastic bags do.”