Biodiesel: A comprehensive review of properties, catalyst types, and feedstock sources
V.S. Shanthini, D. Chitra, Ganesh Moorthy
Abstract
Current biodiesel production faces three primary bottlenecks: variability in feedstock quality, difficulties in scaling laboratory-scale processes to industrial levels, and substantial life cycle carbon emissions. Addressing these challenges requires the development of feedstock-flexible processes, scalable reactor designs, and strategies to minimize environmental impacts. This review provides a comprehensive examination of biodiesel production, emphasizing catalyst development and feedstock selection. Catalysts are categorized into homogeneous, heterogeneous, and biocatalysts, with particular focus on the sustainability and economic advantages of waste-derived heterogeneous catalysts. For example, calcium oxide–based catalysts derived from biomass and industrial-derived waste residues can lower production costs by up to 20 % while maintaining high conversion yields (>95 %), process scalability, and life cycle assessment. Biodiesel characterization is addressed through advanced analytical techniques, including Fourier-transform infrared spectroscopy (FT-IR) for functional group identification, proton nuclear magnetic resonance (1H NMR) for conversion verification, and gas chromatography (GC) for assessing purity and composition, ensuring conformity with ASTM and EN fuel quality standards. By focusing on biodiesel properties and sustainable feedstock utilization, this review proposes strategies to mitigate challenges related to feedstock variability, industrial scalability, and life cycle environmental performance, thereby contributing to the advancement of biodiesel's role in the global renewable energy portfolio.