Organic Fertilizers Rife With Microplastics: Study

Converting biowaste to plant food is an overlooked source of tiny plastic pollutants, researchers say.

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Shawna Williams

Shawna joined The Scientist in 2017 and is now a senior editor and news director. She holds a bachelor's degree in biochemistry from Colorado College and a graduate certificate and science communication from the University of California, Santa Cruz.

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Apr 4, 2018

compostISTOCK, MAERZKINDThe recycling of biological waste from homes and businesses to make fertilizer, either through composting or fertilization, is a source of microplastic pollution, according to a study published today (April 4) in Science Advances. The particles were present despite efforts to sort and sieve out plastic contaminants either before or after the waste was processed, the authors note.

“The recycling of organic waste through composting or fermentation and subsequent application on agricultural land is, in principle, an environmentally sound practice to return nutrients, trace elements, and humus to the soil,” the study authors write. “However, most household and municipal biowaste is contaminated by plastic material.”

See “Plastic Pollutants Pervade Water and Land

Microplastics, which the new study defines as plastic particles smaller than 5 mm, result from the breakdown of plastics, and are pervasive both on land and in the oceans. While the extent of...

In the new study, researchers at the University of Bayreuth in Germany investigated fertilizer produced by a biowaste composting plant (which treats waste aerobically) and a biowaste digester (which uses an anaerobic process). There were fewer than 25 microplastic particles per kilogram in the compost from the first plant, while the freshly-digested fertilizer from the second plant had up to 146 particles per kilogram of the pollutants. By contrast, no microplastics were found in digestate from an agricultural energy crop digester, suggesting that the contamination in the products from the first two plants originated in the homes and businesses that were the source of the waste used.

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Organic Fertilizers Rife With Microplastics: Study

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