A steady-state system for farming black soldier flies to convert agri-food waste into frass and other value-added products

The black soldier fly (BSF), Hermetia illucens L. (Diptera: Stratiomyidae) is an insect decomposer used to valorize food and agricultural waste. Until now, large investments have been directed towards developing industrial-scale insect farming systems. Although there is potential for BSF farming to be adopted also by small and medium farmers, agricultural cooperatives, food processing facilities and university campuses, an affordable and easy-to-adopt BSF farming system has not been developed yet. Here we designed and tested a modular steady-state BSF rearing method for the rapid conversion of cafeteria waste into residual decomposed matter known as frass, a product made of insect excrements, residual undigested organic matter, insect exuviae, mineral nutrients, and a rich microbiota. We used the prepupae output (PP kg/m2-day) to track the efficiency of the system and compared it between a minimal and a multimetric monitoring approach. This comparison demonstrated how monitoring moisture, temperature, and pH in the system can produce a continuous, reliable yield of prepupae and frass, which increased by 47% and 42%, respectively, after the start of monitoring these metrics. The enhanced recovery of both outputs constitutes a potential source of revenue to offset operating costs. By enabling adult reproduction and egg laying to occur in the same space as larval fattening, and removing the need for rearing BSF in batches, our system can save on space and labor costs relative to established rearing options. This will increase BSF farming accessibility for smaller-scale users with limited resources and diverse waste management needs.