Conversion of wheat straw and food waste employing insect (Hermetia illucens) larvae into biomanure and protein-lipid-rich animal feed

Agricultural waste disposal has become a global problem, and its perilous discarding causes various issues of environmental pollution and resource inefficiency. Meanwhile, insect larvae have shown a promising ability to convert such waste substances into added-value materials. This study investigated the bioconversion of wheat straw (WS) and food waste (FW) employing black soldier fly larvae (BSFL). The lignocellulosic content in WS makes it unsuitable for larval feeding, therefore, we pre-treated WS with white-rot fungi for 28 days and then utilized it for larval feeding after mixing with FW in different ratios (25, 50, 75 and 100 %). Fungal pre-treatment caused a significant reduction in component loss (lignin, 30.41 %; cellulose, 16.05 %; hemicellulose, 17.86 %), making it suitable for BSFL feeding. BSFL showed a high relative growth rate (0.21 – 1.17 %), bioconversion rate (7.88 – 40.85 %), waste reduction index (7.69 – 13.79 %) and feed conversion ratio (1.33 – 2.72 %) in feed mixtures with 50 – 75 % WS. Harvested BSFL biomass exhibited (dry biomass basis) high protein N (3.6–4.7 %) and lipid (14.13 – 37.2 %) in different feed mixtures, suggesting its suitability as animal feed. The spent waste (larvae frass) exhibited a high content of nitrogen (1.70 – 2.03 %), total phosphorus (5.95 – 9.65 %), and potassium (0.74 – 1.81 %), suggesting its feasibility as manure for crop applications. In conclusion, BSFL could be a valuable tool for the bioconversion of WS and FW into nutrient-rich animal biomass and manure, as well under a waste-to-wealth approach.