Bioconversion of kitchen wastewater into high-value larval biomass using black soldier fly larvae

Efficient valorization of kitchen wastewater remains a critical challenge in sustainable waste management. This study evaluates the bioconversion potential of black soldier fly (BSF, Hermetia illucens L.) in treating kitchen wastewater using four substrates: kitchen waste (KW), fresh chicken manure (FM), dry chicken manure rehydrated with water (DW), and dry chicken manure amended with kitchen wastewater (DK). Bioconversion efficiency was assessed through the evaluation of larval nutritional composition, growth performance, ammonia (NH 3 ) emissions, and intestinal flora composition via 16S rRNA-based high-throughput sequencing. The KW group larvae showed the highest nutritional quality, as indicated by elevated levels of essential amino acids (Thr: 1.69%, Val: 2.52%), total amino acids (36.89%), and medium-chain saturated fatty acids (C12:0; 26.35%). They exhibited significantly higher biomass and more efficient fresh weight conversion than other groups, and also produced the lowest NH 3 emissions. In contrast, the DK group, where kitchen wastewater was used as a moisture source, produced larvae significantly enriched in glutamic acid (Glu; 5.18%), cysteine (Cys; 0.32%), and total unsaturated fatty acids (60.52%). Despite comparable total amino acid content (35.44%) to the KW group, the DK group showed better growth and lower NH 3 emissions than the DW group. Microbial analysis revealed that all gut communities were dominated by Firmicutes and Bacteroidota . The FM group exhibited the highest microbial diversity, while the KW group had the lowest. This study demonstrates a scientifically robust method for converting kitchen waste into high-value larval biomass using BSF. It highlights the potential of kitchen wastewater as a supplement to enhance resource recovery and reduce environmental impacts.