Scientists from the University of Bayreuth have found increased amounts of microplastics in finished compost from German composting plants. The researchers criticize the legal regulations for limiting plastic particles in compost as insufficient.
Bayreuth (dpa / lby) - According to the findings of Bayreuth researchers, finished compost from German composting plants contains a large amount of microplastics. The scientists have systematically examined commercially available compost for biodegradable plastic particles, as reported by the University of Bayreuth. The researchers examined four urban organic waste recycling plants in Baden-Württemberg and discovered a large number of microplastic particles smaller than one millimeter.
According to the study, these particles accounted for 0.43 percent of the dry weight of the compost - only 0.1 percent is actually allowed under the German Fertilizer Ordinance. However, this limit only applies to microplastic particles that are larger than two millimeters.
"The legally defined limit value for the proportion of biodegradable microplastics should also include much smaller particles in the future in order to significantly reduce the pollution of agricultural land," said Professor Ruth Freitag, head of the study and holder of the Chair of Bioprocess Engineering at the University of Bayreuth, according to one Message.
This is also necessary because the particles often have properties that could significantly delay their biological degradation by microorganisms, according to the scientist: "The longer microplastic particles remain in the soil, the greater the risk that they will be ingested by soil organisms and get into the food chain."
The study also shows that the European certification standard EN 13432 for compostable and therefore biodegradable material is not very effective, the scientists criticize: According to the standard, plastics are considered biodegradable if they break down to 90 percent into particles that are smaller in less than twelve weeks than two millimeters. In modern composting facilities, however, composting takes place in shorter periods of time. This is possibly why residues of biodegradable material were still found in the finished compost, said Thomas Steiner, one of the first authors of the study.
