Chapter 21 - Black soldier fly biorefinery: A novel upcycling route for municipal biosolids

Abstract

The identification of novel waste management strategies is pivotal in establishing the circular economy for low-value organic matter. Conversion of organic refuse by saprophages offers a promising alternative for nutrient recovery from organic waste and has been identified as a sustainable upcycling alternative of protein production for humans and animal feed. Black soldier fly (BSF) larvae (Hermetia illucens) can grow on a wide variety of organic materials during their development from eggs to pupae and have been used to convert organic waste of different origin into high-value compounds and compost. The purpose of this research was to understand the potential use of BSF larvae for upcycling municipal sludge and the link between substrate and larvae composition, with particular attention to the change in proteins. Sludge (S)–containing media (50%) was used for larvae growth in combination with different proportions of brewery spent grains (B), coffee waste (C), and whey (W). Larvae size and weight, in addition to protein and lipid content, were measured at different stages of the larvae growth to assess their suitability for animal feed and product extraction. BSF larvae completed their development on all media with the exception of that containing a high percentage of whey (S5BCW3, S:B:C:W 50%:10%:10%:30%). Significative differences (p-value < 0.05) in larvae size and weight were found between the control media (containing no sludge) and media with high content of whey (S5BCW3) and coffee (S5BC3W, S:B:C:W 50%:10%:30%:10%). However, there were no significative differences (p-value > 0.05) between the control and media containing 50% wastewater sludge and 50% brewery by-products (S5B5) or high content of brewery spent grains (S5B3CW, S:B:C:W 50%:30%:10%:10%).