DOI: 10.31025/2611-4135/2026.19590 ISSN: 2611-4135

Impact of different screening technologies on the separation of plastic, metal and glass impurities from composts

Erwin Binner, Peter Beigl, Benedikt Vay, Rene Schwarzl, Marion Huber-Humer, Christian Zafiu
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The application of compost is regulated in the EU member states mainly based on the quantity of hazardous chemical elements and compounds and on physical contaminants, such as glass, metals and plastics. A large fraction of impurities is removed by screening of the rotting material usually before the composting process is started or at the end of the process. Different screening technologies are used to obtain high quality composts. However, the removal efficiency of impurities for frequently used screening technologies was not thoroughly studied so far. In this study raw compost (rotting duration 6 weeks) from a composting plant, was treated by 6, 8, and 10 mm flip-flop screens and 12 and 25 mm drum screens. The produced composts were analyzed on their properties as well as quantities of impurities. In addition, plastic impurities in fraction down to 0.63 mm were investigated for their quantity in mass, the particle number, polymer, and form type (fiber, film and fragments). The results show that all investigated screening technologies were able to remove plastic-impurities to a level below the thresholds (limit-value 0.3 % DM in the fraction > 2 mm) for composts according to the EU fertilizer regulation. The deeper analysis, however, showed that plastics of different form types were separated with different efficiencies by flip-flop and drum screens. Additionally, microscopic analyses of the separated plastics indicated that film and fiber materials that were larger than the mesh sizes were not entirely separated by screening.

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