Digestion of fruit wastes by black soldier fly (Diptera: Stratiomyidae) larvae alters moisture content and emissions of greenhouse gas, noxious gases, and odors

Black soldier fly, Hermetia illucens, (L.) (Diptera: Stratiomyidae) larvae convert organic wastes into insect biomass that can be used as livestock feed. Recent evidence also indicates larvae can reduce emissions of greenhouse gases and noxious odors; however, these benefits are substrate and scale dependent. The current study examined the impact of black soldier fly larval digestion on moisture level, greenhouse gas (i.e., carbon dioxide), noxious gases (i.e., ammonia, carbon monoxide, and hydrogen sulfide), and volatile organic compound production for coconut, honeydew, orange, and control (Gainesville diet) substrates at an industrial scale. Overall, moisture content for some substrates digested by larvae was significantly (P < 0.05) lower (>20%) than those without larvae. However, differences across substrate types were observed, with final moisture content ranging from 35% (coconut) to 52% (oranges). The presence of black soldier fly larvae did not significantly (P > 0.05) impact overall greenhouse gas emissions. However, significant differences were detected at select days of the experiment. From an industrial perspective, recycling waste with larvae (7-d process) would potentially result in reduced duration for producing greenhouse gases versus placing substrates in a landfill (weeks to months to compost). The presence of black soldier fly larvae did significantly (P < 0.05) impact overall volatile organic compound profiles of the substrates. Larval impact on volatile abundance, richness, and evenness was substrate dependent. These results demonstrate the need to formulate diets and engineer systems that maximize benefits associated with black soldier fly larvae, while minimizing greenhouse gas and volatile organic compound emissions.