Study reveals “biodegradable” bioplastics persist in soil and contaminate farmland

13 Nov 2023 --- A scientific study by Wageningen University in the Netherlands has revealed findings about the longevity of “biodegradable” bioplastics in agricultural soils, contradicting industry standards. 

Commissioned by the Dutch environmental charity Plastic Soup Foundation, the research unearthed “serious questions about the biodegradability credentials of bio-based plastics.” 

Soil samples taken from ditches surrounding agricultural fields showed a presence of approximately 3,000 microplastics per gram of sediment, signifying an accumulation of microplastics in the environment. Samples were taken at eight flower farms in the Netherlands in September 2022 and eight coriander farms in Spain in November 2022. 

Researchers found some 48 different types of microplastics across the tested samples. Approximately 61% of the microplastics detected were fossil fuel-based, while the remaining 39% were bio-based.

The primary culprit behind agricultural microplastic pollution was identified as the use of plastic mulch, employed to warm the soil and inhibit weed growth. The study found that these “biodegradable” plastic mulches persist in soils beyond the industry-prescribed two-year degradation period, a direct violation of the EN 17033 standard.

Dr. Esperanza Huerta Lwanga, the study’s lead researcher, emphasizes the findings’ gravity: “The concentrations of microplastics in agricultural soils and 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 questions since those particles move from soils and accumulate in sediments where they do not degrade anymore.”

Samples were taken at eight flower farms in the Netherlands in September 2022 and eight coriander farms in Spain in November 2022.Regulating plastic
The implications of this research have prompted campaigners to call for stricter regulations on the environmental claims made by bioplastic manufacturers. With the Global Plastic Treaty negotiations ongoing at the United Nations Environmental headquarters, various environmental organizations are advocating for comprehensive measures to combat plastic pollution. 

“On behalf of the Plastic Health Council, Plastic Soup Foundation and A Plastic Planet will plea together with leading scientists for a strong and comprehensive treaty that tackles plastic pollution on a global scale to protect the environment and human health,” the Plastic Soup Foundation shares.

The Plastic Soup Foundation’s director, Maria Westerbos, notes: “Farmers increasingly use biodegradable plastic mulches. Mulch is sold to farmers with the false promise of degradability within two years. ‘They can simply be left on the field and plowed under’ producers claim under false promises.”

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

Biodegradable credibility
The study’s revelations cast doubt on the credibility of biodegradability claims associated with bio-based plastics, urging urgent action to address the concerning impact of these materials on agricultural soils and the broader environment.

Packaging giant Mondi recently joined forces with Cotesi to tackle mounting concerns regarding the environmental impact of plastic mulch in agriculture with the release of Advantage Kraft Mulch, a 100% compostable kraft paper solution with no plastic or coating.

Within the EU, an estimated 80 million kilograms of mulch film are used annually, with 5% marketed as biodegradable, details the Plastic Soup Foundation. Despite the standard dictating that these plastics should degrade by 90% within two years, no regulations concerning degradation in ditch sediment currently exist.

“With the review of the EU Fertiliser regulation coming up in July 2024, it is essential that the findings of this research are taken into account,” the organization underscores.

By Radhika Sikaria