Micro- and nanoplastic size affects uptake and digestive tract region residence time in black soldier fly larvae during food waste bioconversion

Black soldier fly (Hermetia illucens L.) larvae (BSFL) are promising recycling agents of food waste nutrients. However, BSFL ingest micro- and nanoplastics (MNPs) present in food waste, consequently introducing them into the food chain when BSFL-derived products are used as feeds or fertilizers. Our short-term exposure study (180 min ingestion, 1080 min egestion) deepens the understanding of particle transport during bioconversion by BSFL by determining how the size of nanoplastics (NPs, 220 nm) and microplastics (MPs, 10-20 and 53-63 µm) and food waste moisture content (65 % vs. 75 %) affect particle uptake, progression, and egestion across the different morphofunctional digestive tract regions of BSFL. Results demonstrate distinct differences in gut retention time among MNPs. NPs were taken up and transported more rapidly than larger MPs. Indigestible MPs (10-20 µm) exhibited different residence times than soluble blue dye, suggesting distinct particle residence times or discrimination between food and plastics within the BSFL digestive tract. In the short-term experiment, particle egestion was slower than ingestion. Higher moisture content increased the retention time of food waste, suggesting the need for further investigation into whether this can be used to manipulate the clearance of MNPs. The study findings contribute to safer bioconversion processes during circular food waste management.