A review of breakthroughs in biodiesel production with transition and non-transition metal-doped CaO nano-catalysts

The rising energy demand, coupled with increasing pollution and the depletion of fossil fuel reserves, has led to an urgent need for sustainable fuel alternatives like biodiesel. However, biodiesel production is not without its challenges, especially when using homogeneous catalysis, which often results in soap formation and high wastewater production. This review focuses on the use of heterogeneous base catalysts, particularly calcium oxide (CaO) doped with transition and non-transition metals, as a more efficient method for biodiesel production from various raw materials. The inclusion of transition and non-transition metal dopants in CaO catalysts plays a crucial role in enhancing their performance. These dopants significantly increase the surface area of the catalysts, leading to higher biodiesel yields (84.9–99.7%) and offering a marked improvement over traditional homogeneous catalysis methods. The study delves into the reaction mechanisms, thermodynamics, comparison of economic aspects of using heterogeneous and homogeneous catalysts, life cycle assessment (LCA), and practical implications of this study. It highlights that metal-doped heterogeneous catalysts are not only more efficient but also offer environmental benefits such as the emission of fewer pollutants and cost benefits due to reusability, ease of separation, and cheaper maintenance. In addition, future research should explore the untapped potential of new dopants and waste materials for developing cost-effective and sustainable catalysts. Investigating statistical methods and optimization models is crucial for finding optimal conditions for efficient biodiesel production.