Green solvent extraction of lipids from spent coffee grounds: A computational fluid dynamics approach

Background: The rising production of food waste presents significant environmental and economic challenges worldwide. This study investigates the valorization of food waste, specifically focusing on spent coffee grounds, by extracting lipids using environmentally friendly solvents for biodiesel production. Method: We developed and experimentally validated a comprehensive computational fluid dynamics (CFD) model to optimize the lipid extraction process. The model examines the impact of solvent velocity, inlet temperatures, and material bed thickness on extraction efficiency. Significant findings: Our study shows that increasing solvent velocity enhances lipid recovery by 45 % due to improved mass transfer. Ethanol yielded the highest extraction efficiency (26.2 %), followed by ethyl acetate (24.9 %) and hexane (21.2 %) at 0.0004 m/s and 25°C. Lipid extraction improved with temperature, reaching 30 % at 40°C and 40 mm bed thickness. Under optimal conditions (0.0004 m/s, 40°C, 40 mm), ethanol achieved a peak extraction of 38 %. These findings highlight the potential of spent coffee grounds for biodiesel production and the effectiveness of ethanol in sustainable lipid recovery.