Composting waste is heralded as being good for the environment. But it turns out that compost collected from homes and grocery stores is a previously unknown source of microplastic pollution, a new study April 4 in Science Advances reports.
This plastic gets spread over fields, where it may be eaten by worms and enter the food web, make its way into waterways or perhaps break down further and become airborne, says Christian Laforsch, an ecologist at the University of Bayreuth in Germany. Once the plastic is spread across fields, “we don’t know its fate,” he says.
Compost samples taken from supermarket waste contained the greatest amount of plastic particles, with 895 pieces larger than 1 millimeter found per kilogram of dry weight. Household compost in contrast contained 20 and 24 particles per kg of dry weight, depending on the size of the sieves used to sift the compost.