Wed, May 01, 2019 - Page 6 News List

‘Biodegradable’ plastic still intact after sea, soil burial

LITTERING:Plastic bags that claim to be biodegradable did not show any substantial deterioration over a three-year period in all environments, UK researchers found

The Guardian

Volunteers fish plastic out of the canals after King’s Day in Amsterdam, the Netherlands, on Sunday.

Photo: EPA-EFE

Plastic bags that claim to be biodegradable were still intact and able to carry shopping three years after being exposed to the natural environment, a study found.

The research for the first time tested compostable bags, two forms of biodegradable bag and conventional carrier bags after long-term exposure to the sea, air and earth.

None of the bags decomposed fully in all environments.

The compostable bag appears to have fared better than the so-called biodegradable bag.

The compostable bag sample had completely disappeared after three months in the marine environment, but researchers said that more work is needed to establish what the breakdown products are and to consider any potential environmental consequences.

After three years the “biodegradable” bags that had been buried in the soil and the sea were able to carry shopping.

The compostable bag was present in the soil 27 months after being buried, but when tested with shopping was unable to hold any weight without tearing.

Researchers from the University of Plymouth’s International Marine Litter Research Unit said the study — published in the journal Environmental Science and Technology — raises the question of whether biodegradable formulations can be relied on to offer a sufficiently advanced rate of degradation and therefore a realistic solution to the problem of plastic litter.

“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. “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.”

About half of plastics are discarded after a single use and considerable quantities end up as litter.

Despite the introduction of charges for plastic bags in the UK, supermarkets are still producing billions each year.

A survey of the top 10 supermarkets by Greenpeace showed that they were producing 1.1 bilion single-use plastic bags, 1.2 billion plastic produce bags for fruit and vegetables, and 958 million reusable “bags for life” a year.

The Plymouth study says that in 2010 it was estimated that 98.6 billion plastic carrier bags were placed on the EU market and about 100 billion additional plastic bags have been placed every year since.

Awareness of the problem of plastic pollution and the impact on the environment has led to a growth in so-called biodegradable and compostable options.

The research said that some of these products are marketed alongside statements indicating they can be “recycled back into nature much more quickly than ordinary plastic” or “plant-based alternatives to plastic.”

However, Napper said the results showed none of the bags could be relied on to show any substantial deterioration over a three-year period in all 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,” the research found.

The study showed that the way compostable bags were disposed of was important. They should biodegrade in a managed composting process through the action of naturally occurring micro-organisms.

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