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Microplastics in composts, digestates, and food wastes: A review
Summary
This review examines how food waste composting and recycling processes can introduce microplastics into agricultural soil. When food waste mixed with plastic packaging is composted or processed through anaerobic digestion, microplastic fragments can end up in the soil amendments spread on farmland. The findings highlight an overlooked pathway by which microplastics enter the food chain, as crops grown in contaminated compost may absorb or accumulate plastic particles.
Diverting food waste from landfills to composting or anaerobic digestion can reduce greenhouse gas emissions, enable the recovery of energy in usable forms, and create nutrient-rich soil amendments. However, many food waste streams are mixed with plastic packaging, raising concerns that food waste-derived composts and digestates may inadvertently introduce microplastics into agricultural soils. Research on the occurrence of microplastics in food waste-derived soil amendments is in an early phase and the relative importance of this potential pathway of microplastics to agricultural soils needs further clarification. In this paper, we review what is known and what is not known about the abundance of microplastics in composts, digestates, and food wastes and their effects on agricultural soils. Additionally, we highlight future research needs and suggest ways to harmonize microplastic abundance and ecotoxicity studies with the design of related policies. This review is novel in that it focuses on quantitative measures of microplastics in composts, digestates, and food wastes and discusses limitations of existing methods and implications for policy.
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