Bioconversion of expired canned cat food via Black Soldier Fly larvae: a sustainable approach to waste valorisation

The pet food industry generates significant waste, including expired products that are often discarded, contributing to environmental concerns. This study explores the potential of using expired canned cat food as a rearing substrate for Black Soldier Fly Larvae (BSFL, Hermetia illucens), evaluating its impact on larval growth and nutrient composition. Three expired canned cat foods (beef, chicken and salmon-based) were tested against a commercial broiler diet as a control (CTRL). Results indicate that BSFL successfully developed on all tested substrates, with the salmon-based diet (SD) yielding the highest growth rate (0.010 g/day, p < 0.01) and nutrient assimilation, similar to the control group. The beef-based diet (BD) resulted in lower lipid accumulation (16.98% DM, p < 0.05), while all substrates influenced the larvae’s protein (ranging from 43.12% to 45.64% DM) and fatty acid profiles. Notably, lauric acid, a key antimicrobial and metabolic compound, remained predominant in all larvae, with values ranging from 42.18% (BD) to 60.34% (CTRL) of total fatty acids (p < 0.01). These findings highlight the feasibility of expired pet food as a valuable resource for insect farming, promoting circular economic principles. However, regulatory constraints currently limit their use in feed applications. Future research should address legal considerations and optimise substrate formulations to enhance larval performance and industrial applications.