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Insect decomposers are a missing link in our food and agricultural systems. Reintroduction of insects can help convert a linear food system, which creates unusable waste, to a "circular food system" that recycles waste to new products. The Black Soldier Fly (BSF), Hermetia illucens, is an ideal decomposer for circular food systems. BSF larvae (immatures) can turn any type of low-grade waste into body mass quickly. BSF biomass can then be harvested to use as feed for fowl or aquaculture, and to isolate high-end protein and fat, oil for biofuel and other valuable byproducts, such as chitin/chitosan and melanin. At the same time, these insects reduce the volume of waste and transform it into a nutrient-rich, compost-like substance called frass. Because of its efficacy in valorizing waste to usable products, BSF is now widely used around the world for waste management and decontamination. But until now, commercialized BSF operations have only been feasible at industrial scales, even though waste recycling and added revenue streams are needed across many sectors.Agriculture is one such sector where BSF have great potential to turn unusable outputs (e.g., unmarketable crops and some crop residues) into products that are usable on site (insect frass as fertilizer) and products that bring additional income (larvae or pupae). The frass produced by BSF larval feeding on waste is particularly useful to generate on-site. Frass contains both digested waste and insect exoskeletons made of chitin. It is rich in nitrogen and is a suitable replacement for environmentally damaging synthetic fertilizers. As it is broken down by microbial activity, the chitin in frass stimulates plant immunity against pests and pathogens and increases the abundance and diversity of beneficial microbes in the rhizosphere. This product is so versatile as a soil amendment, it is now being produced and marketed by the BSF industry.Despite the clear benefits of on-farm BSF rearing for cost savings on agricultural waste removal, fertilizer, soil and plant health maintenance, and generating additional income, BSF rearing remains confined to large, for-profit entities focused exclusively on insect rearing at industrial scales. This sector can absorb the labor costs of BSF production through the current standard "batch" method, whereby carefully measured cohorts of larvae are established with set quantities of food waste as a substrate, then maintained through development for harvest. However, BSF rearing on-farm using the batch methods adopted at industrial scales would involve manual labor inputs that would outweigh any cost savings gained through production of fertilizer or marketable larvae.An alternative that is more flexible, less labor intensive, and adaptable to on-farm scales is the "steady state" rearing method, which involves continuous rearing of BSF in bioreactors housing overlapping generations of BSF larvae. The bioreactor environment is partially open, allowing natural oviposition by adults and eliminating the need for labor intensive egg collection and weighing. The design also takes advantage of the natural "self-harvesting" behavior of mature larvae, which are known as prepupae when they stop feeding and darken. Insects in this stage remove themselves from the substrate and migrate to a waste-free and dry location (e.g., a bin) for final maturation to adults. Although less labor intensive than batch rearing, steady state rearing operations still require some human labor for maintenance. This includes dispensing of waste to bioreactors, stacking and de-stacking of bioreactor bins, removal of spent waste (frass product) to spent waste reservoirs, vacuum removal of self-harvested prepupae to collection vessels, and monitoring bioreactors for issues that would prompt corrective action (e.g., checking for excessive heat, monitoring carbon dioxide, ammonia, pH, moisture).The long-term goal of the proposed project is to automate steady-state rearing maintenance tasks that currently require human labor to enable on-farm use of BSF for agricultural waste recycling. The proposed project will address this goal through the following three objectives:Objective 1: engineer cost-conscious solutions to automate maintenance and monitoring tasksObjective 2: compare costs and returns of the automated system to more labor-intensive methodsObjective 3: evaluate and demonstrate the performance of an automated system in an agricultural context.Our efforts will produce the first prototype of a semi-automated steady-state BSF rearing operation suitable for use on small to mid-sized farms, as well as use in other contexts where food/green waste is abundant, but labor costs high (e.g., college campuses).

Gebiola, M.; Mauck, KE, .; Karydis, KO, .
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