Metabolic performance of black soldier fly larvae during entomoremediation of brewery waste

This study aims to evaluate the metabolic performance, in terms of specific rates of growth and feed assimilation, as well as the cost of growth and maintenance of black soldier fly larvae, BSF, Hermetia illucens on brewery waste, a potential worldwide available resource for industrial scale insect production. Brewery waste lacks starch and thus has a nutritional profile substantially different from chicken feed, which is a well-established and excellent starchy food source for BSF larvae. It is therefore interesting to gain insight into how BSF larvae perform on brewery waste. Larvae of the BSF were reared on chicken feed, on brewery waste and on mixtures of the two. Measurements of the weight of the larvae and their respiratory CO₂ production were used to estimate metabolic performance on daily basis. The BSF larvae grew on all the substrates. They reached the highest weight on chicken feed, but their specific growth and feed assimilation rates were highest on the mixed substrates, in which the larvae also reached their maximal weight in the shortest time. Substrate-dependent costs of growth were not observed while maintenance rates tended to be only slightly lower on the mixed substrates. Overall, the BSF larvae converted the low-starch brewery waste and the starchy chicken feed into larval biomass about equally efficiently, although brewery waste led to smaller larvae and mixing of the two substrates enhanced feed assimilation and growth. Brewery waste seems thus a suitable resource for BSF larvae, comparable with chicken feed, with respect to their metabolic performance.