Are plastic bags biodegradable? Not really, says new UK research
India, United Kingdom and several countries have taken steps to curb the use of plastic amid growing concerns over pollution, but claims that some bags are biodegradable don’t stand up to scrutiny, new research released on Monday says.
Biodegradable and compostable plastic bags are still capable of carrying full loads of shopping after being exposed in the natural environment for three years, the study by researchers from the University of Plymouth says.
Degradation of five plastic bag materials widely available from retailers was examined in the study. They were then left exposed to air, soil and sea, environments which they could potentially encounter 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 assessments of more subtle changes in tensile strength, surface texture and chemical structure.
The biodegradable, oxo-biodegradable and conventional plastic formulations remained functional as carrier bags after being in the soil or the marine environment for over three years, the study published in Environmental Science and Technology says.
The compostable bag completely disappeared from the experimental test rig in the marine environment within three months but, while showing some signs of deterioration, was still present in soil after 27 months.
The study questions whether biodegradable formulations can be relied upon to offer a sufficiently advanced rate of degradation to offer any realistic solution to the problem of plastic litter.
Researcher Imogen Napper said: “After three years, I was really amazed that any of the bags could still hold a load of shopping. For a biodegradable bag to be able to do that was the most surprising”.
“When you see something labelled 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”.
Richard Thompson, head of the university’s International Marine Litter Research Unit, added: “This research raises a number of questions about what the public might expect when they see something labelled as biodegradable. We demonstrate here that the materials tested did not present any consistent, reliable and relevant advantage in the context of marine litter”.