Abstract
Simple SummaryIn the last few years great efforts have been made to find alternative protein sources to soybean meal and valorize organic by-product, which are produced in large amounts by food industries and are often inedible by humans. In this context, insects could be an alternative protein source. The aims of this study were to evaluate the growth performance, nutrient composition, and environmental impact of Hermetia illucens reared on a control hen diet and by-products diets (okara, maize distillers, and brewer’s grains). The rearing substrate affected larvae growth performance, nutritive value, and environmental impacts. Larvae fed on a hen diet and the maize distiller exhibited the higher final weight and required fewer days to reach the prepupal stage. The lipid content of the larvae was positively correlated to that of the insect diets. The environmental impact of larvae production on the hen diet, characterized by a high inclusion of soybean meal, was the most impactful for most of the environmental categories. Feed production activities were the main contributor to environmental impact. The use of by-products for larvae growth allowed us to reduce the environmental impact to produce 1 kg of protein in comparison with the use of soybean meal as a protein source.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.
Highlights
By-products are incidental or secondary products resulting from a production process, whose main purpose is not the production of the item itself
After analysing the climate change generated for the production of 1 kg of lipid (Figure 5), the results suggest that the production of 1 kg of lipids is generally more impactful than the production of 1 kg of protein, mainly because the feed used for animal diets are often by-products, and the major quantity of fat is extracted into the main product, the vegetable oil, used for human nutrition, or biodiesel
This study aimed to evaluate the growth performances and environmental impact of black soldier fly (BSF) reared on different by-products on a lab scale
Summary
By-products are incidental or secondary products resulting from a production process, whose main purpose is not the production of the item itself. A possible alternative exploitation of by-products is represented by their use as a rearing substrate for insects, constituting an interesting example of a sustainable circular economy [1,2,3]. In this context, organic by-products can be valorized to produce a valuable insect biomass, which is rich in protein and fat, for the animal feed industry [4,5,6] or biodiesel production [7,8,9]. Okara availability has been increasing throughout the world due to an increased production of soybeans, and the dumping of okara has become a problem due to its impact on the environment [10]
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