Enzymatic Synthesis and Fuel Characterization of Biodiesel from Waste Cooking Oil with Candida antarctica Lipase

One of the strategies towards sustainable production of energy is the upgrading of waste oils into biodiesel. Enzymatic transesterification with Candida antarctica lipase B is an alternative to traditional alkaline catalysis, which has low efficiency with low-quality feedstocks like used WCO. The present research examined the transformation of WCO to biodiesel by means of immobilized Candida antarctica lipase B. These were aimed at optimizing the conditions of the reaction and determining the properties of biodiesel fuels and the stability and reusability of catalysts. A conversion yield of 97% in 8 h was attained in mild conditions of optimization (35 °C, methanol-to-oil molar ratio of 4:1). The yielded biodiesel was in compliance with ASTM D6751 and EN 14214 requirements with appropriate kinematic viscosity (3.81 mm2/S−1), density (0.882 g cm−3), and low acid value (0.48 mg KOH g−1) which revealed high-quality fuels. The enzyme was immobilized and had more than 85% of its original activity even after ten cycles. In contrast to alkaline catalysis, enzymatic reaction did not produce the soap since free fatty acids were simultaneously esterified and triglycerides were simultaneously transesterified, which made their separation easier and gave high-purity glycerol. On the whole, the presented work proves that WCO-based biodiesel production catalyzed by lipase is a promising, sustainable and efficient way of valorizing WCO.