From insect lipids to biodiesel through the bioconversion process of vegetable by-products.

Waste management and rising energy demand are two of the most pressing global challenges facing humanity. The Black Soldier Fly (BSF) offers a promising dual solution to both issues. As a key organism within the circular bioeconomy, BSF larvae (BSFL) convert organic waste into valuable biomass, producing high-value compounds such as lipids, proteins, and chitin. These bioconversion products have potential applications across multiple sectors, highlighting the insect's role in sustainable resource management and waste valorization. In this study, we tested the hypothesis that optimizing vegetable-based diets- particularly through supplementation with carbohydrate-rich bread-can improve BSFL survival, bioconversion efficiency, and lipid yield for biodiesel production, demonstrating the feasibility of managing vegetable waste while simultaneously producing biodiesel. Specifically, BSFL were reared on various vegetable waste substrates, with diets strategically enriched with bread to enhance performance. This dietary adjustment resulted in high larval survival rates, exceptionally high lipid yields of up to 60 %, and a significant increase in the saturated fatty acid content of the extracted lipids-yielding biodiesel that meets standard quality parameters. Furthermore, we report comprehensive bioconversion metrics, including larval growth, substrate reduction, and survival rates, to assess how different vegetable-based diets influence BSFL performance. To verify the industrial feasibility of our approach, we also conducted larger-scale experiments on BSFL rearing and lipid extraction, highlighting the key parameters that need to be controlled during scale-up. Overall, this study demonstrates a tailored diet formulation for maximizing biodiesel yield, showcasing the potential of BSFL to simultaneously address organic waste management and renewable fuel production. It presents a dual opportunity: waste management companies can significantly cut disposal costs, while biofuel producers gain access to a sustainable, cost-effective feedstock.