The aim of the study was to evaluate the use of three by-products as growing substrates for Hermetia illucens (Black Soldier Fly (BSF)) larvae: okara, maize distiller, brewer’s grains, and a control hen diet. The study focused on larval growth and bioconversion performance, production of methane by larvae and environmental burden of larvae production, using Life Cycle Assessment (LCA) on a lab scale. Chemical composition of substrates differed: okara had the highest crude protein and ether extract contents, while brewer’s grains showed the highest fiber content. Larvae fed on a hen diet and maize distiller exhibited the highest final weights (2.29 and 1.97 g, respectively). Larvae grown on okara showed the highest indexes for waste reduction and efficiency of conversion of the ingested feed. The BSF larvae did not produce any detectable traces of CH₄. LCA evaluation showed that larvae production on a hen diet resulted in the most impact for most of environmental categories, for the inclusion of soybean meal in the diet (for climate change, 5.79 kg CO₂ eq/kg dry larvae). Feed production activities resulted in the main contributions to environmental impact. In order to compare the larvae production obtained on all substrates, an environmental impact was attributed to okara and brewer’s grain through a substitution method, and, by this approach, the best sustainable product resulted from the larvae grown on the maize distiller.

Hermetia illucens (L.) (Diptera: Stratiomyidae) is able to consume a wide range of organic matter and is of particular interest for waste management. The nutritional value of preimaginal stages, in particular the protein content, makes this species a valid candidate for use as feed for other organisms. Vegetables and fruits are promising rearing substrates for insects produced for this purpose according to the EU regulation. In order to examine the effects of diets on insect performance and chemical composition, larvae were reared on the following substrates: 1) fruit (apple, pear, and orange); 2) vegetable (lettuce, green beans, and cabbage); and 3) mixed fruits and vegetables. High percentages of survival were observed on all diets, but there were differences among weights of larvae, pupae, and adults, with weights of larvae reared on mixed fruits and vegetables lower than on other diets. Pupae reared on the mixed diet were heaviest, and also morphometric measurements of adults were highest. Larvae reared on fruit diets had the highest fat content, comprising mostly saturated fatty acids; the highest content of essential n-3 fatty acids was found in vegetable reared larvae and that of n-6 in mixed reared larvae. Larvae reared on the mixed diet had the highest protein content. Calcium contents were high and moderate amounts of iron and zinc were found. H. illucens showed the capability to develop on vegetable and fruits diets displaying different nutrient profiles and biological performances. The best-performing rearing strategy should vary in relation to the final use of H. illucens.

The worldwide growing consumption of proteins to feed humans and animals has drawn a considerable amount of attention to insect rearing. Insects reared on organic wastes and used as feed for monogastric animals can reduce the environmental impact and increase the sustainability of meat/fish production. In this study, we designed an environmentally closed loop for food supply in which fruit and vegetable waste from markets became rearing substrate for Hermetia illucens (BSF— black soldier fly). A vegetable and fruit-based substrate was compared to a standard diet for Diptera in terms of larval growth, waste reduction index, and overall substrate degradation. Morphological analysis of insect organs was carried out to obtain indications about insect health. Processing steps such as drying and oil extraction from BSF were investigated. Nutritional and microbiological analyses confirmed the good quality of insects and meal. The meal was then used to produce fish feed and its suitability to this purpose was assessed using trout. Earthworms were grown on leftovers of BSF rearing in comparison to a standard substrate. Chemical analyses of vermicompost were performed. The present research demonstrates that insects can be used to reduce organic waste, increasing at the same time the sustainability of aquaculture and creating interesting by-products through the linked bio-system establishment.

The aim of this work was to develop processing methods that safeguard the quality and antimicrobial properties of H. illucens and B. mori oils. We adopted a vegetable diet for both insects: leftover vegetables and fruit for H. illucens and mulberry leaves for B. mori. First, alternative techniques to obtain a good oil extraction yield from the dried biomass of H. illucens larvae were tested. Traditional pressing resulted to be the best system to maximize the oil yield and it was successfully applied to B. mori pupae. Oil quality resulted comparable to that obtained with other extraction methods described in the literature. In the case of B. mori pupae, different treatments and preservation periods were investigated to evaluate their influence on the oil composition and quality. Interestingly, agar diffusion assays demonstrated the sensitivity of Gram-positive Bacillus subtilis and Staphylococcus aureus to H. illucens and B. mori derived oils, whereas the growth of Gram-negative Pseudomonas aeruginosa and Escherichia coli was not affected. This study confirms that fat and other active compounds of the oil extracted by hot pressing could represent effective antimicrobials against bacteria, a relevant result if we consider that they are by-products of the protein extraction process in the feed industry.

Hermetia illucens is an efficient bioconverter able to grow on various different organic materials, producing larvae, which are a good source of protein and fat with applications in the animal feed and biochemical industries. This fly’s capacity to reduce huge amounts of waste presents an interesting opportunity to establish a circular food economy. In this study, we assessed the suitability of using organic wastes from cricket and locust farming to rear H. illucens. Larvae developed until adult emergence on all the wastes, with a mean survival of over 94%. Cricket waste allowed faster development of heavier larvae than locust waste. Substrate reduction was particularly interesting on cricket waste (<72%), while locust waste was only reduced by 33%. The nutritional composition of the larvae reflected that of the growing substrates with a high protein and fat content. These results demonstrate the potential of using H. illucens to reduce and valorise waste generated when farming various insects through the production of a larval biomass for use as a protein meal in animal feeds or industrial applications.

Spinosyns are a class of insecticides with a broad range of action against many insect pests belonging to different orders, noxious to a wide variety of agricultural crops; spinosyns were also used against insects of sanitary interest. Spinosyns are derivative of biological active substances produced by soil Actinomycete Saccharopolyspora spinosa; being of biological origin, they are considered to have a low environmental impact and they are not much aggressive against nontarget species. They act as allosteric activators of nicotinic acetylcholine receptors; thanks to their mode of action the resistance phenomena are uncommon, even few cases of resistance were recently reported. For all these reasons at present they are one of the most interesting product to be used in fighting against agriculture pests.