Plastics and persistent chemical contaminants in food waste: challenges for the circular economy

• Food waste carries microplastics, PFAS, BFRs and phthalates at measurable levels. • Valorisation methods seldom remove persistent contaminants effectively. • PFAS reach 676 µg/kg and microplastics exceed 300000 particles per kg in waste. • Phthalates and BFRs are poorly studied with uncertain fate and risks. • Harmonised methods and sensor based tools are needed for safer reuse pathways. Food waste surpasses 1 billion tonnes per year, contributing approximately 10% of global greenhouse gas emissions, underscoring the urgency of transforming this waste into a resource within a circular economy. Effective repurposing demands a robust understanding of contamination sources and management to mitigate the risks associated with valorised products. Plastics and persistent chemical contaminants such as brominated flame retardants (BFRs), per- and polyfluoroalkyl substances (PFAS), and phthalates—are pervasive in food waste due to their resistance to degradation, environmental ubiquity, and use in packaging and contact materials, presenting significant environmental and human health risks when retained in waste matrices. Microplastics arise from trace contaminants in food, disposal, and pre-treatment processes like de-packaging, with reported contamination ranging from 0.025–5.6% w/w or 20–300,000 particles/kg, though results vary by methodology. BFR concentrations in industrial composts range from 10–100 µg/kg and from 1.38–20 µg/kg in household kitchen waste, though data on source-separated streams are limited. PFAS contamination varies from 4.53–676 µg/kg. Though generally below regulatory thresholds, the persistence and bioaccumulation potential of these contaminants pose long-term risks. This review consolidates knowledge on plastics and persistent chemical contaminants in food waste, addressing their management in valorisation processes such as soil amendments, biorefineries, and animal feed. Critical gaps in harmonised analytical methods and baseline data hinder accurate risk assessment, highlighting the need for advanced quality assurance tools. Closing these gaps will require harmonised analytical methods, essential-use policies for persistent chemicals, and the integration of sensor-based monitoring technologies that enable real-time information collection and use, ensuring food waste valorisation is both safe and sustainable within a circular economy.