Optimization of Enzymatic Biodiesel Production from Waste Cooking Oil Using Lipase: Process Modelling, Yield Enhancement, and Fuel Characterization

The energy crisis and environmental degradation caused by fossil fuels requires innovative sustainable alternatives. Biodiesel presents a viable solution through renewable feedstock conversion, yet traditional chemical transesterification encounters significant obstacles including soap formation, expensive purification processes, and free fatty acid (FFA) sensitivity. Waste cooking oil (WCO) remains underutilized primarily due to elevated FFA levels, making lipase-catalyzed transesterification an attractive eco-friendly approach. Response Surface Methodology with central composite design optimized key reaction parameters: lipase concentration, methanol-to-oil ratio, temperature, and duration. Statistical analysis revealed that individual lipase and methanol variations showed minimal significance; however, their combined interaction with temperature and time substantially affected biodiesel production. Maximum yield reached 85.6% at optimized conditions—10 wt.% lipase, 6:1 methanol-to-oil ratio, 60°C temperature, and 120-minute reaction time. Physicochemical testing validated product quality against ASTM D6751 and EN 14214 international standards. Measured properties included density at 872 kg/m3, kinematic viscosity of 4.5 mm2/s, flash point of 167°C, and copper strip corrosion rating of 1a. These findings demonstrate enzymatic catalysis as an effective green technology for converting WCO into high-quality biodiesel, simultaneously resolving waste disposal challenges while advancing renewable energy goals. The approach eliminates harsh chemical catalysts while maintaining commercial viability through acceptable conversion efficiency and product specifications.