Bioconversion of spent mushroom substrate and wet distiller's grains by black soldier fly larvae: effect of substrates on larval treatment and residues

Abstract Spent mushroom substrate (SMS) and wet distiller's grains (WDG) are growing organic wastes. The black soldier fly larvae (BSFL) can convert multiple organic wastes. However, there is limited information on their conversion by BSFL. Therefore, this study explores the conversion of SMS and WDG of five proportions by BSFL. This study shows that BSFL can convert SMS, WDG and their mixtures, 100% WDG is suitable for the growth of the BSFL. BSFL can promote the humification of the substrate during the treatment process, increasing the content of total kjeldahl nitrogen, total organic carbon, total phosphorus and total potassium in the residues. The fractionation mode of carbon and nitrogen elements and the microbial community in residue is obviously different, but that is closely relates to the physicochemical parameters and the microbial community of the substrate. The mixture treated by BSFL is helpful to form a residue with higher humus, but it may be unstable.