Safety of black soldier fly (Hermetia illucens) larvae reared on waste streams of animal and vegetal origin and manure

Abstract

Abstract In Europe, commercial and scientific interest in black soldier fly larvae (BSFL, Hermetia illucens) as a new feed source has grown substantially, primarily because this species can be reared on waste-streams which are otherwise unsuitable. However, before BSFL may legally be reared on such materials, and subsequently fed to livestock animals, safety must be guaranteed. Many hazards could be relevant, depending on the origin of the waste stream. Small- and large-scale experiments were performed in which BSFL were reared on the organic wet fraction of municipal household waste (OWF), kitchen/fast food waste (FFW), mushroom feet stems (MF), pig manure liquid slurry mixed with roadside silage grass (PMLSG), pig manure solids (PMS), and secondary sludge from slaughter waste (SW). Larval yields were highest on the control (chicken feed + water) and the FFW. Substrates and larvae were analysed to determine the presence of heavy metals, acrylamide, pesticides, veterinary drugs, and pathogenic bacteria. Cadmium (Cd) bioaccumulated in larvae reared on all substrates, in line with previous research. Some pesticides and veterinary drugs were found in the substrates: concentrations in the larvae were low, but potential formation of metabolites could be studied further. Acrylamide was present in the FFW, but not in the larvae reared on it: more research is needed to determine the (metabolic) fate. Bacillus cereus and traces of Salmonella spp. were found on some larval samples, but appropriate processing is anticipated to minimize potential risks. Based on these results, we conclude that most tested substrates are suitable for rearing BSFL, and do not appear to present major safety concerns, aside from the need for monitoring Cd concentrations in the substrates, and control measures for pathogenic bacteria. Further verification to account for variance in contamination of substrates is needed for definitive conclusions on the safety.