Insect husbandry is an economically promising and environmentally responsible means to produce quality ingredients for fish feeds . Among all insects, one the best candidates for this role is the black soldier fly ( Hermetia illucens) which has already been tested on many species of fish . This insect is prolific, and its life cycle sufficiently well understood for a controllable husbandry. The black soldier fly (BSF) larvae grow very fast (2,000X gain in about 20 days) eating a wide variety of food waste materials and show excellent food conversion efficiency . Very i mportant for any animal growing industry, the BSF larvae cultures tolerate the highest known biomass density (in kg per volume of growth facility), and have the highest biomass yield, relative to any other farmed animal. Close to 100 million tons of surplus organics is available each year in the US alone . If all this waste material is steered toward farmed insects it would result in more protein than the global production of fish meal. Recent advances in the BSF science and industry create d an opportunity for rapid expansion of BSF protein as a reliable commodity. We review features that will heavily influence the contribution of the BSF protein industry to the evolution of fish farming. These are: requirements and solutions for high product quality; relationship between technological advances and production costs; and ecological impacts of the BSF industry.
With regards to product quality, we will discuss the importance of the BSF feed materials. The sourcing, composition and the pre-processing of the larvae feed have become key requirements for obtaining quality protein. We will also discuss how novel fermentation technologies led to an industry that is now safe fro m spreading food-borne pathogen s. The quality and consistency of the products (proteins and fats) are discussed , as well as other valuable byproducts of this industry (fertilizers and BSF-derived polymers) . Selection processes, novel genetic lines, larvae immunization for increased fish health and the monitoring of insect pathogens are promising research directions to the benefit of this industry .
At the technology level, four types of processes control product quality and the economic efficiency of the BSF protein industry. These are: the husbandry protocols , the biomass drying method, the defatting choice and the technologies used for mass transfer. We compare outcomes of the various technological choices that are presently implemented in th e BSF industry and what should be expected with regards to performance for fish feeds . The introduction of automation in large factories led to sizable BSF factories with improved economics. This is excellent news for urban areas that must manage large volumes of perishable food waste. For example, a one million people city, or a food pre-processing industry servicing one million consumers, will produce over 250 mt of food waste daily . On the other hand, e conomic analyses have indicated that minimalist dimensions to make a BSF protein factory sustainable begin at sizes as low as 40-80 mt of food waste per day. G reat prospects now exist for mutually beneficial symbios is between cities as little as 300,000 inhabitants and sustainable BSF factories.
Finally , the future of the BSF protein industry also depends on its environmental footprint. I t was shown that BSF protein has the lowest consumption of freshwater relative to other methods of producing feed- grade protein , and also the lowest GHG footprint relative to other methods of recycling food waste. For all these reasons, the BSF protein industry is only at the cusp of its potential as a global commodity and predicted to grow at an accelerated pace in the next decade.