Bioplastic marketed as ‘biodegradable’ are remaining in soils and ditches for longer than the two-year industry standard, a scientific study has found.

Every year in the EU 80 million kilograms of mulch film are being used, of which is 5% biodegradable (4 million kilograms).

The study was conducted by researchers at Wageningen University in the Netherlands.

It was commissioned by Dutch environmental charity Plastic Soup Foundation.

Researchers found some 3,000 microplastics per gram of sediment in samples taken from ditches surrounding agricultural fields. This is evidence that microplastics accumulates in the environment, which is a violation.

The main reason for the microplastic pollution in soils is the use of plastic mulch used to warm up the soil and to prevent weed growth.

Industry standard EN 17033 states that biodegradable plastic mulches should be biodegraded in soils by 90% within two years time. No regulation related to degradation in sediment of ditches is in place.

The study found high concentrations of microplastics derived from bio-degradable plastic mulches that did not degrade in two years time under field conditions. This violates Standard EN 17033.

Samples were taken at eight flower farms in the Netherlands in September 2022 and at eight coriander farms in Spain in November 2022.

Researchers found some 48 different types of microplastics across the tested samples.

Some 61 percent of the microplastics detected were found to be fossil fuel-based, while the remaining 39 percent were bio-based.

Campaigners say the study raises serious questions about the biodegradability credentials of bio-based plastics.

And they have called for tighter regulations on the environmental claims made by bioplastic manufacturers.

Lead researcher Dr Esperanza Huerta Lwanga said: “The concentrations of microplastics in agricultural soils and in ditch sediments are high, and vary according to the sampling place. This is worrying and shows the need for more studies, and further measures.

“Biodegradable plant-based mulches were specifically developed to quickly degrade in soil. However this study indicates that these biodegradability claims are open to serious question, since those particles move from soils and accumulate in sediments where they do not degrade any more.”

Maria Westerbos, director of Plastic Soup Foundation said: “Biodegradable plastic mulches are increasingly used by farmers. Mulch is sold to farmers with the false promise of degradability within two years. ‘They can simply be left on the field and ploughed under’ producers claim under false promises.”

“This study shows that these mulches risk contaminating the soils in which the food we eat is grown.”

“A wide body of evidence has linked microplastic pollution with serious health threats. Because of this I urge the plastic manufacturers to urgently cease selling products to farmers with dubious claims of biodegradability.”

From 13 – 19 of November 2023 the negotiations for a Global Plastic Treaty continue at the United Nations Environmental (UNEP) headquarter in Nairobi. On behalf of the Plastic Health Council, Plastic Soup Foundation and A Plastic Planet, will plea together with leading scientist for a strong and comprehensive treaty that tackles plastic pollution on a global scale, to protect the environment and human health.

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