Upscaling volatile fatty acids production: Demonstrating the reliability of anaerobic fermentation of food wastes from the lab towards industrial implementation

In recent years, the anaerobic fermentation (AF) of food waste (FW) has gained significant attention as a sustainable solution for waste valorization. However, the challenge of scaling up biotechnological processes for industrial applications remains a key barrier to commercialization. This investigation addressed this challenge by scaling up an auto-AF process from laboratory scale (4 L) to pilot (50 L) and demonstration scale in an industrial environment (250 L), using a lipid-rich FW (46.6 %, w/w) as the feedstock and endogenous microbiota as the inoculum. The applied operating conditions promoted the hydrolysis (>35 % volatile solids (VS) removal) and acidogenesis (>58 % of soluble chemical oxygen demand (sCOD) acidified) steps. As the reactor size for technology testing was increased, efficient mixing was crucial to ensure a proper homogenization of the fermentation broth. Lactic acid bacteria (LAB) prevailed in the endogenous microbiota, contributing to the enhanced hydrolysis and acidification efficiencies determined at all the scales. The minimal performance variations determined at different reactors' scales, along with the stability of the metabolite profiles, demonstrated the robustness and reliability of AF, opening the door to continue further industrialization.