D2.2: Indirect plastics pollution of the environment

Microplastic contamination in organic waste-derived products such as compost and digestate is an emerging environmental concern due to their application in agricultural soils. In this study, plastic particles larger than 630 µm were analysed in compost (300 g) and digestate (100 g) per sample from four European locations, two from Finland and one each from Germany and Slovenia (NIC, RE, HSY, and PJH). The results revealed significant variation in both abundance and polymer composition across samples. Compost samples were primarily dominated by polyethylene and polypropylene, indicating contamination from packaging materials, whereas digestate samples showed a more variable composition, including a high proportion of polyester PES in certain cases. Notably, PES was identified in the form of flakes rather than fibers, suggesting fragmentation of plastic materials rather than textile-derived contamination. The lowest plastic abundance was observed in compost derived from source-separated green waste, highlighting the importance of feedstock quality. Overall, the study demonstrates that both composting and anaerobic digestion processes do not eliminate plastics and may contribute to their persistence and fragmentation into micro/nano plastics. These findings underline the need for improved waste management practices to reduce plastic contamination in organic fertilizers.