Larvae of the black soldier fly, Hermetia illucens (Diptera: Stratiomyidae), are voracious feeders of organic material and may thus be used in simple engineered systems to reduce organic waste in low- and middle-income countries. Controlled feeding experiments with standard fodder were conducted to assess the optimum amount of organic waste to be added to a CORS system (Conversion of Organic Refuse by Saprophages). A daily feeding rate of 100 mg chicken feed (60% moisture content) per larva resulted in an optimum trade-off between material reduction efficiency (41.8%, SE 0.61) and biomass production (prepupal dry weight: 48.0 mg, SE 2.0). Applied to market waste and human faeces, this corresponds to a potential daily feeding capacity of 3—5 kg/m² and 6.5 kg/m², respectively. In addition, H. illucens prepupae quality was assessed to determine their suitability to substitute fishmeal in animal feed production. The chitin-corrected crude protein content ranged from 28.2 to 42.5%, depending on the amount of food provided to the larvae. Based on our study, a waste processing unit could yield a daily prepupal biomass of 145 g (dry mass) per m². We conclude that larvae of the black soldier fly are potentially capable of converting large amounts of organic waste into protein-rich biomass to substitute fishmeal, thereby contributing to sustainable aquaculture.

Valorisation of municipal organic waste through larval feeding activity of the black soldier fly, Hermetia illucens, constitutes a potential benefit, especially for low and middle-income countries. Besides waste reduction and stabilisation, the product in form of the last larval stage, the so-called prepupae, offers a valuable additive in animal feed, opening new economic niches for small entrepreneurs in developing countries. We have therefore evaluated the feasibility of the black soldier fly larvae to digest and degrade mixed municipal organic waste in a medium-scale field experiment in Costa Rica, and explored the benefits and limitations of this technology. We achieved an average prepupae production of 252 g/m²/day (wet weight) under favourable conditions. Waste reduction ranged from 65.5 to 78.9% depending on the daily amount of waste added to the experimental unit and presence/absence of a drainage system. Three factors strongly influenced larval yield and waste reduction capacity: (1) high larval mortality due to elevated zinc concentrations in the waste material and anaerobic conditions in the experimental trays; (2) lack of fertile eggs due to zinc poisoning, and (3) limited access to food from stagnating liquid in the experimental trays. This study confirmed the great potential of this fly as a waste manager in low and middle-income countries, but also identified knowledge gaps pertaining to biological larvae requirements (egg hatching rate, moisture tolerance, …) and process design (drainage, rearing facilities, …) to be tackled in future research.

The recycling of organic waste worldwide is not effective, which leads to water pollution and loss of potential crop fertilizers. Available resources have to be used more efficiently as the world population increases. An innovative solution is to use insects for the management of organic waste. Here, we used black soldier fly to convert organic waste into animal feed protein, as fly larvae, and plant fertilizer, as compost residue. A continuous fly reactor was monitored for 9 weeks. We analyzed physicochemical and microbial parameters, and we evaluated the sanitary risk. Results show 55.1 % of material degradation and 11.8 % of biomass conversion based upon total solids. We observed higher levels of N and P in the treatment residue than in the inflow material. Results also show a lower concentration of Salmonella spp. and viruses. Compost treatment with black soldier fly is therefore an efficient system for nutrient recycling.

In developing countries, effective waste management strategies are constrained by high collection costs and lack of adequate treatment and disposal options. The organic fraction in particular, which accounts for more than 50% of the waste production, constitutes a great, yet mostly neglected, reuse potential. Concomitantly, the demand for alternative protein sources by the livestock feed industry is sharply increasing. A technology that effectively transforms organic waste into valuable feed is therefore a timely option. Larvae of the non-pest black soldier fly, Hermetia illucens L. (Diptera: Stratiomyidae), may be used to reduce the mass of organic waste significantly. Concurrently, larval feeding converts organic waste into prepupae (last larval stage) which is high in protein. In combination with a viable market, this potential animal feed may cover the waste collection costs and thus promote innovative, small-scale entrepreneurs to establish a profitable business niche. Organic waste, however, often contains persistent pollutants, such as heavy metals, that may accumulate in the larvae and prepupae of black soldier flies and consequently in the food chain. In this study, we fed black soldier fly larvae chicken feed spiked with heavy metals (cadmium, lead and zinc at three concentrations each) to examine the extent of metal accumulation in the different life stages and the effect of heavy metal concentration in the feed on the life cycle determinants of the flies. The cadmium accumulation factor in prepupae (metal concentration in the body divided by metal concentration in the food) ranged between 2.32 and 2.94; however, the lead concentration remained well below its initial concentration in the feed. The bioaccumulation factor of zinc in prepupae decreased with increasing zinc concentration in the feed (from 0.97 to 0.39). None of the three heavy metal elements had significant effects on the life cycle determinants (prepupal weight, development time, sex ratio).