Feeding black fly soldier larva using fermented solid residue generated from food waste three-phase separation

During the pretreatment of some food waste (FW) treatment plants, FW is centrifugated to separate crude oil for biodiesel processing, liquid phase for anaerobic digestion (AD), and solid residue for AD or incineration. To increase the benefits of FW treatment, in this study, we tried black soldier fly larvae (BSFLs) cultivation using the solid residue before and after fermentation and evaluated the quality of larvae as animal protein feed. The results showed that direct fermentation (lactic acid fermentation without any additives) and mixed fermentation (with yeast and cellulase addition) prompted the protein content of the solid residue to 45–48%, with lactic acid, acetic acid, and ethanol as the main products. When shifting the solid residue to the directly fermented or mixed-fermented residue, the average weight increment of BSFLs increased from 145 to 162 mg and 181 mg, the survival rate of BSFLs rose from 86.00 to 91.67% and 93.67%, and the protein content of BSFLs increased from 42.47 to 47.50% and 49.63%, respectively. The essential amino acid index of BSFLs rose from 0.92 to 0.95 and 0.96, verifying excellent protein feed. The results provide a new pathway to enhance FW resource utilization.