Plastics and associated chemical contaminants in black soldier fly larvae food waste bioconversion

Abstract

Insect-based food waste valorization is expanding globally, particularly through the use of black soldier fly larvae (BSFL). However, post-consumer food waste often contains plastic debris and associated persistent chemical contaminants, raising safety concerns for food, feed, and environmental health within circular economy systems. This review examines the fate of micro- and nanoplastics and associated chemical co-contaminants, specifically phthalates, brominated flame retardants (BFRs), and per- and polyfluoroalkyl substances (PFAS), selected due to their widespread occurrence in plastics, persistence, and potential for transfer through waste streams. Current evidence suggests BSFL are relatively robust to microplastic exposure. Larger microplastics are typically egested, while retention time depends on polymer type, particle size, and larval composition. In contrast, the behavior of nanoplastics remains poorly understood due to analytical limitations and limited experimental evidence. Chemical contaminant fate is strongly governed by compound chemistry. Phthalates may undergo partial microbial transformation within BSFL systems, although the toxicological implications of metabolites such as monophthalates remain unclear. PFAS show inconsistent bioaccumulation patterns across studies, while the behavior of BFRs in BSFL systems remains largely uncharacterized. Many contaminants partition into frass, raising concerns about soil accumulation and potential reentry into food chains. Post-harvest processing, such as blanching or drying, may redistribute rather than eliminate contaminants, depending on their solubility and binding behavior. Most studies rely on spiked exposure designs that poorly represent real waste streams. Harmonized contaminant screening, realistic exposure studies, and fit-for-purpose regulation are needed to ensure safe scaling of insect-based circular bioeconomy systems.