Black Soldier Flies Rock

After all, they are an amazing species that is a versatile tool in improving the sustainability of both food production and waste management. Black soldier flies are also into heavy metal(s), as in accumulating them from feeding substrates. Unfortunately, this may prevent using black soldier flies for recycling certain types of wastes into harvestable biomass. On the plus side, this may also allow using them for reducing heavy metal pollution by extracting these chemicals from contaminated substrates.

Kofroňová, J., Melliti, A. and Vurm, R., 2024. Biogas Digestate and Sewage Sludge as Suitable Feeds for Black Soldier Fly (Hermetia illucens) Larvae. Toxics, 12(6), 414.

Hermetia illucens larvae can use organic wastes as a substrate, which makes them an interesting potential feed. However, waste may contain heavy metals, which are limited in feed. Here, we investigated the ability of H. illucens to grow on organic wastes and measured their heavy metal bioaccumulation. The larvae were fed with food waste, biogas digestates, and sewage sludge. When the first adult fly was visible, the tests were stopped and the larvae immediately processed. The samples (wastes before use, larvae after feeding) were analysed for mineral nutrient and heavy metal content using AAS and ICP-OES, respectively. The results show that the weight of the larvae fed with food waste increased sevenfold, which was broadly in line with expectations. Those fed with sewage sludge and digestate from biogas station increased threefold. While the larvae fed with sewage sludge exceeded the limits for heavy metals, particularly Cd and Pb, in feedstock, those fed with biogas digestate and food waste did not. These findings add to the literature showing the suitability of different wastes as H. illucens feed, and the importance of excluding waste contaminated with heavy metals from larvae intended for use as animal feed, or else diverting these larvae to non-feed uses.