Waste-derived calcium oxide catalysts in biodiesel production: Exploring various waste sources, deactivation challenges, and improvement strategies

This review explores the use of waste-derived calcium oxide (CaO) catalysts in biodiesel production, highlighting their potential as sustainable and cost-effective alternatives to conventional catalysts. Unlike prior studies that broadly address catalysis, this work focuses on enhancing biodiesel yield and quality by identifying optimal strategies for CaO catalyst performance. Key elements addressed include: (i) customizing CaO catalysts for diverse feedstocks to enhance resistance to leaching and deactivation, (ii) mitigating the impact of free fatty acids and water content in feedstocks, which often cause unwanted side reactions, (iii) improving catalyst stability and efficiency through tailored preparation techniques, such as doping and support materials, and (iv) evaluating environmental and economic benefits. CaO catalysts derived from waste materials show promise due to their high basicity, reduced methanol solubility, and accessibility, offering a feasible route to biodiesel production at a lower cost. This review summarizes current advancements and suggests pathways for future development to improve the industrial viability of waste-derived CaO catalysts in biodiesel applications.