BIODEGRADATION: 'Biodegradable' plastic bags survive three years in soil and sea.

11. June 2019 | Waste, Plastics | via


A plastic bag labelled biodegradable after three years in the marine environment. (Credit: Imogen Napper)

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, according to an article on

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 say 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 say 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.

Imogen Napper, who led the study, said: “After three years, I was really amazed that any of the bags could still hold a load of shopping. For biodegradable bags 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.”

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


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