Cascade resource recovery from municipal biowaste in an integrated black soldier fly biorefinery: experimental evaluation and energy balance

Recovering the energy and material value of organic municipal waste requires treatment systems that integrate biological conversion with downstream product recovery. This study experimentally investigated an integrated biorefinery based on black soldier fly larvae (BSFL), in which organic fraction of municipal solid waste (OFMSW) was converted into multiple products through larval bioconversion, mechanical lipid recovery, ultrasonic-assisted biodiesel synthesis, and anaerobic digestion of the remaining frass. Biodiesel synthesis reached a conversion efficiency of 94% after 30 min, and the subsequent digestion of frass produced 185 mL CH₄ g−¹ VS. Analysis of material flows showed how the principal biomass streams could be directed toward biodiesel, biomethane, defatted protein-rich meal, glycerol, and nutrient-rich digestate. Extrapolation to the daily OFMSW generation in Tehran indicated a net energy gain of 3.15 GWh day−¹ and a net energy ratio of 3.42. The corresponding gross greenhouse gas (GHG) avoidance was estimated at 1,509 t CO₂-eq day−¹, principally through the assumed substitution of fossil diesel, grid electricity, and natural-gas-derived heat. The findings are based on laboratory-scale experiments, while the city-scale energy and GHG estimates represent extrapolations from the experimental results rather than measurements from a full-scale facility. Overall, the results demonstrate the potential of integrated insect biorefineries as a cascade resource-recovery strategy for simultaneously recovering energy, nutrients, and value-added products from OFMSW while reducing residual waste and associated environmental burdens.