Mineral profile and heavy metals bioaccumulation in black soldier fly (Hermetia illucens, L.) larvae and frass across diverse organic substrates

Organic wastes from vegetable mix (V) and butchers (B) were used as substrates (V100%, V75%+B 25%, and V50%+B50%) for Hermetia illucens to assess the mineral profile of the larvae and frass, and the potential bioaccumulation of toxic elements (As, Cd, Pb, Hg). The V100 larvae had the highest concentrations of all minerals, except for Se and P, higher in the control group (poultry diet as substrate) (p <.01). The V50B50 and V75B25 larvae showed lower (p <.01) mineral concentrations than the other groups. The V50B50 group had the highest (p <.01) bioaccumulation factor (BAF) for Cd (8.52%), the V100 for Pb (p <.01). The equations to estimate the mineral content of larvae from the substrate were significant only for Ca and Mg (p <.05). The V100 frass had the highest (p <.01) levels of As, Cd, Pb, Fe, K and Mg, while the control group showed the highest (p <.01) levels of Se, Zn, Ca, P and K. Toxic elements can accumulate in black soldier fly larvae and frass, with the exception of Hg. However, organic wastes from V and B had a very low content of toxic elements and that strongly reduced the risk of excessive bioaccumulation in larvae. Indeed, the content of toxic elements in larvae is lower than the maximum values established for feed materials by EU regulations. In conclusion, organic substrates from vegetables or butchery wastes can be used for BSF larvae growth without the risk of accumulation of toxic elements.