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The need to avoid the use of unnecessary plastic is noble and necessary, but new research casts doubt on the environmental safety of some forms of biodegradable plastic.
The researchers found that the biodegradable and compostable labeled bags were still able to carry a full load of races after being allowed to degrade in the elements for three years – they do not decay as quickly as expected.
The study from the University of Plymouth in the United Kingdom raises the question of whether the biodegradable chemical mixtures contained in these bags go far enough. If the plastic is still in the environment three years after being scrapped, it is still a major problem in terms of waste and pollution that should be solved.
"After three years, I've been really surprised that one of the bags can still hold a lot of shopping," said researcher Imogen Napper. "For a biodegradable bag, it was the most surprising."
"When you see something like this, I think you automatically assume that it will degrade faster than conventional bags, but after at least three years, our research shows that this may not be the case."
The team tested a total of five types of plastic bags, all widely available in UK stores: two types of oxo-biodegradable bags, a biodegradable bag, a compostable bag and a conventional high density polyethylene bag.
Oxo-biodegradable plastics are designed to break down relatively quickly, but can still leave tiny microplastics, unlike true biodegradables. Compostable plastics, on the other hand, are a subset of biodegradable plastics that are developed to degrade faster.
The five types of plastic were tested in the open air, buried in the ground and immersed in the "ocean". The researchers measured surface loss and disintegration over time as well as tensile strength, surface texture and chemical structure.
In the open air, all the bags were put to the test, which fragmented in just nine months.
(University of Plymouth)
With regard to soil and water, the situation was different: the biodegradable, oxo-biodegradable and conventional plastic bags could still contain three years after their burial or immersion.
The type of compostable bag did its best: it disappeared from the aquatic environment in three months and was also fragmented in the soil environment – although fragments were always detected after 27 months of testing.
None of the bags have completely deteriorated in all three environments.
Through their analysis, researchers hope to better understand what is meant by "biodegradable" in plastic bags – a product that can be recycled under the heat and pressure of an industrial facility may not disappear as quickly in the natural environment. .
In other words, biodegradable as a label does not mean much without the conditions and time scale of the degradation attached.
The team also wants stricter international standards to define the definition of biodegradable. In the United Kingdom, single-use plastic bags have been subject to a 5 P tax since 2015 and are now removed from department stores.
A spokesman for Vegware, who provided one of the compostable bags, said The Guardian "It's important to understand the differences between terms such as compostable, biodegradable and oxo-degradable … compostable materials can compost in five essential conditions: microbes, oxygen, moisture, heat and time."
"This research raises a number of questions about what the public can expect when it sees something that is labeled as biodegradable," said one of the members of the committee. research team, Richard Thompson.
"We demonstrate here that the tested materials did not present any consistent, reliable and relevant benefit in the context of marine litter."
The search was published in Environmental Science and Technology.
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