Enhancement of bioconversion of vegetable biowaste by black soldier fly larvae: Influence of mechanical and thermomechanical pretreatments

• Thermomechanical pretreatment enhances biowaste reduction and bioconversion efficiency. • Comparative analysis of mechanical and thermomechanical pretreatments on BSFL growth. • BSFL contribute significantly to waste reduction and the production of usable biomass. • The impact of pH and polyphenol concentration on larval development is highlighted. In many countries, the growing production of biowaste poses a major environmental threat, requiring significant budgets for its management. This issue has driven the development of innovative valorisation methods, such as bioconversion. Black Soldier Fly Larvae (BSFL) present a promising solution, capable of converting biowaste into larval biomass rich in proteins and lipids. In this study, we evaluated the impact of mechanical and thermomechanical pre-treatments, combined with optimized substrate formulations, on the performance of BSFL. Thermomechanical pre-treatment significantly improved nutrient solubility, reduced inhibitory compounds such as polyphenols from orange peels, and enhanced larval growth compared to mechanical pre-treatment alone. Mixed substrates showed optimal performance, with a survival rate of 98.3%, a bioconversion rate of 31.11%, a reduced development time of 18 days, and a biowaste reduction efficiency of up to 83%. However, coffee grounds, due to their high lignin content and recalcitrant compounds, exhibited low biodegradability and limited availability of soluble nutrients, even after thermomechanical pre-treatment. These results demonstrate that the use of mixed substrates, combined with appropriate pre-treatments, enables increased waste reduction and improved larval performance. This study highlights the importance of pre-treatment and substrate formulation in maximizing BSFL efficiency for biowaste valorization while promoting sustainable waste management and a circular bioeconomy.