Bioconversion of Different Waste Streams of Animal and Vegetal Origin and Manure by Black Soldier Fly Larvae Hermetia illucens L. (Diptera: Stratiomyidae)

SIMPLE SUMMARY: The worldwide waste problem has large environmental impacts and huge efforts have been made to mitigate this problem. Black soldier fly (Hermetia illucens) larvae (BSFL) were proposed as an efficient way to get rid of organic waste, acting by converting the waste into a protein- and lipid-rich biomass suitable for various purposes such as animal feed, biodiesel and chitin. This article studies larval growth and development and waste reduction and conversion indexes of BSFL when reared on six different waste streams and a control substrate (chicken feed): pig manure slurry mixed with roadside silage grass, the organic wet fraction of municipal household waste, secondary sludge from slaughter waste, fast food waste, mushroom stems and pig manure solids. In addition, the larval fatty acid profile and the chemical composition of the frass were also analyzed. The larval growth as well as the waste reduction index and the efficiency of conversion of ingested substrate were highest in the fast food waste (FFW) substrate. The larvae reared on FFW had high fat content and produced fat-rich frass with high dry matter content. Slaughter waste, pig manure and mushroom stems also showed good potential for bioconversion and led to protein-rich larvae. ABSTRACT: Black soldier fly larvae (BSFL) are considered a commercially viable solution for global organic waste problems. The objective of this study was to assess the feasibility of rearing BSFL on a wide range of low-value waste streams and its potential to transform them into high-quality animal feed and fertilizer. Six waste streams of different origins were selected and each tested in triplicate. Several parameters were analysed: growth performance, waste reduction index (WRI), conversion efficiency (ECI) and larval composition. Frass composition was also analysed. Larvae reared on fast food waste (FFW) had the highest ECI and WRI and the lowest values when reared on pig manure slurry mixed with silage grass (PMLSG) and slaughter waste (SW). The highest protein content was found for larvae reared on mushroom stems (MS) although this substrate had the lowest protein content. Moreover, the frass nutritional profile was proportionally related to the substrate’s nutritional profile: the protein-rich substrate (SW) resulted in protein-rich frass and the low-protein substrate (MS) resulted in protein-poor frass. The same was true for the lipid content. In conclusion, this study showed that BSFL can be successfully reared on a wide range of waste streams that can affect the larval and frass chemical compositions.