Transesterification and esterification for biodiesel production: A comprehensive review of catalysts and palm oil feedstocks

• Compares catalytic systems for biodiesel synthesis, highlighting performance and limits. • Identifies palm oil derivatives as innovative and sustainable feedstocks for biodiesel synthesis. • Introduces novel strategies to mitigate high free fatty acid content via advanced pretreatments. • Explores the interplay of key process parameters to maximize biodiesel yield and efficiency. • Evaluates the environmental impact and feasibility of palm oil biodiesel through LCA. This review presents a comprehensive and critical evaluation of biodiesel production, emphasizing the synergistic integration of feedstock optimization and catalytic advancements to achieve enhanced efficiency, sustainability, and economic viability. The study systematically analyzes core production methods, including transesterification, direct esterification, and two-step processes, while evaluating the impact of crucial parameters such as alcohol-to-oil molar ratio, catalyst type and concentration, reaction temperature, and reaction time. A thorough assessment of catalytic systems is provided, encompassing homogeneous (alkaline and acidic) and heterogeneous catalysts, with special attention to advanced categories such as bifunctional, biological, and nanocatalysts. The review also examines the transformative potential of palm oil-derived feedstocks, including crude palm oil, kernel palm oil, refined palm oil, palm oil sludge, and used cooking palm oil, critically assessing their viability for biodiesel production. Additionally, the review includes an in-depth Life Cycle Assessment (LCA) of palm oil biodiesel, evaluating its environmental impact and long-term sustainability. By addressing significant research gaps, particularly the linkage between feedstock properties and catalytic performance, this work offers a cohesive framework for advancing biodiesel technology. The findings underscore the potential of customized catalytic systems and diverse feedstock utilization in driving sustainable, economically viable biofuel production. As such, this review serves as an essential resource for researchers, policymakers, and industry leaders committed to solving global energy and environmental challenges.