UK study raises doubts about biodegradable bags

Some supposedly biodegradable plastic bags are still strong enough to carry shopping items after being exposed in air, soil or sea for three years, scientists in the United Kingdom have found.

Research carried out by the University of Plymouth's International Marine Litter Research Unit has raised the question of whether the public has been misled about green issues, and whether biodegradable formulations can be relied on as a solution to the problem of plastic litter, The Guardian newspaper said.

The study, recently published in the journal Environmental Science and Technology, was the first to test compostable bags, biodegradable bags and conventional carrier bags after long-term exposure to natural environments.

None of the bags decomposed fully in any of the environments, although the compostable bag sample had disappeared after three months in the marine environment.

The so-called biodegradable bags, however, were still intact after being buried in the soil and sea. The compostable bag, which performed better, was present in the soil 27 months after being buried.

"After three years, I was really amazed that any of the bags could still hold a load of shopping," said Imogen Napper, who led the study team.

"For biodegradable bags 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."

More work needed

The researchers said more work is needed to establish what are the breakdown products of plastic bags, and to discover more potential environmental consequences.

Each year, the top 10 supermarkets in the UK use 1.1 billion single-use plastic bags and 1.2 billion plastic produce bags for fruit and vegetables, which produce 810,000 tons of plastic waste, according to a survey in November by environmental campaign group Greenpeace.

Under European Union law, plastic bags since 2015 have cost 5 pence (6.5 US cents) in shops. By 2018 usage of such bags had dropped by 30 percent, but the number of bags discarded each year is still significant.

Vegware, the company that produced the compostable bag used in the research, said the study was a timely reminder that no material was magical, and could only be recycled if done correctly.

yandongjie@chinadaily.com.cn

(China Daily 05/01/2019 page4)