Supposedly ‘biodegradable’ plastic bags are still capable of carrying a full load of shopping THREE YEARS years after they’ve been dumped, reveals new research.
While the study carries good news for shoppers, the shock findings raise questions whether ‘biodegradable’ materials can be relied on as a realistic solution to the plastic pollution problem.
Researchers looked at the degradation of five plastic bag materials widely available from high street retailers in the UK.
The plastic was then exposed to air, soil and sea and left in environments which they could encounter when thrown away.
The bags were checked at regular intervals for visible loss and disintegration as well as more subtle changes in strength, surface texture and chemical structure.
After nine months out in the open, all the materials had completely disintegrated into fragments.
But biodegradable, oxo-biodegradable and conventional plastic elements were still functional as carrier bags after being in the soil or even out at sea for more than three years.
The study was carried out at the University of Plymouth where researchers have been studying the environmental impacts of plastic bags for well over a decade.
University of Plymouth research fellow Imogen Napper, who led the study as part of her PhD, 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.”
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.
Researchers from the University’s International Marine Litter Research Unit, which has contributed extensively to national policy debates about the use of plastic bags, said the study poses a number of questions.
Miss Napper added: “The most pertinent is 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.”
According to a European Commission report from 2013, around 100 billion plastic bags were being issued every year.
Several governments, including the UK, have since introduced levies designed to combat the issue.
But many of these items have already entered the marine environment and previous studies at the university that explored their impact on coastal sediments have shown they can be broken down into microplastics by marine creatures.
Professor Richard Thompson OBE, head of the International Marine Litter Research Unit, was involved in those studies and gave evidence which led to the introduction of the 5p plastic bag levy.
He said: “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.”
He added: “It concerns me that these novel materials also present challenges in recycling.
“Our study emphasises the need for standards relating to degradable materials, clearly outlining the appropriate disposal pathway and rates of degradation that can be expected.”
Previous research by the University of Plymouth estimated a single plastic carrier bag could be shredded by marine organisms into around 1.75million microscopic fragments.
The latest findings were published in the journal Environmental Science and Technology.
By Ben Gelblum and Laura Sharman