An efficient strategy to promote food waste composting by adding black soldier fly (Hermetia illucens) larvae during the compost maturation phase

The increasing generation of food waste (FW) poses a significant challenge to global food security and environmental sustainability. Composting is an effective way to recycle FW, while the disease risk of immature compost and the long durations needed for mature compost restrict the application. To address these concerns, black soldier fly larvae (BSFL) were applied in the maturation phase to improve composting efficiency. The results demonstrated that adding BSFL expedited the composting process, achieving the fully mature compost within 25 days. This was evidenced by the elevated nitrate content (1057.52-1475.58 mg/kg) and germination index (GI) (100.2%-107.03%), along with a decreased nitrification index (0.19-0.24) of the BSFLtreated composts. Microbial analysis revealed a discernible elevation in the relative abundance of Ureibacillus, Lysinibacillus, Paneibacills, and Brevibacillus within the compost attributed to the addition of BSFL. Furthermore, BSFL introduction might enhance metabolic functions such as glycolysis, inosine monophosphate biosynthesis, gluconeogenesis, and lysine biosynthesis. As composting progressed, the relative abundance of certain bacteria, like Moheibacter and Actinomadura (initially more prevalent in the compost pile), gradually increased in the gut of BSFL. These findings suggest the existence of complex microbial interactions between the BSFL gut and compost, reshaping the mutual bacterial community and exerting some influence on the compost's metabolic functions. Furthermore, redundancy analysis indicated significant associations between compost's physiochemical properties (i.e., electrical conductivity, moisture content, GI, pH, and NH+4-N) and microbial community across all experimental groups. The discoveries provide valuable insights for the further evolution and functional research of BSFL gut microbiota.