Heavy metal bioaccumulation in prepupae of black soldier fly Hermetia Illucens (Diptera: Stratiomyidae) cultured with organic wastes and chicken feed

Larvae of the black soldier fly (BSF), Hermetia illucens can be reared in large quantities on organic wastes. The larvae are harvested at the prepupal stage and used as feed for poultry and aquaculture. BSF farms in Nigeria make use of a combination of chicken feed and organic waste in the rearing processes. Chicken feed and organic waste can contain varying levels of heavy metals, which may accumulate in the larvae. The aim of this study was to determine bioaccumulation of heavy metals, cadmium chromium, copper, lead, and zinc, in prepupae cultured on chicken mash and various types of organic wastes (food waste, brewery waste, and fruit waste). Bioaccumulation of a particular heavy metal occurs when the concentration of the metal is higher in the harvested prepupae than in the feed substrates (Factor > 1). The results of the study showed that bioaccumulation was more likely to occur in brewery waste than in the other substrates, while bioaccumulation factors greater than one were reported for three of the five heavy metals (copper, lead and chromium). All heavy metal concentrations reported in the study were below the safe limits for use in animal feeds. The use of organic waste rather than chicken mash for rearing BSF larvae should be considered in Nigeria. However, there must be quality control measures in place to ensure that the larvae's propensity for accumulating heavy metals are contained.