Biodiesel production faces environmental and economic challenges due to the use of homogeneous catalysts, such as NaOH, KOH, NaOCH3, and KOCH3. Despite their good activity, these catalysts are toxic and almost impossible to recycle/reuse. Heterogeneous catalysts, otherwise, can be reused and easily separated from the final product, resulting in more sustainable and cost-effective production. However, these catalysts leach, losing activity through reaction cycles and contaminating the biodiesel This review has therefore addressed the use of CaO – a promising catalyst for biodiesel synthesis – and various biochar-derived catalysts. Particular attention was paid to studies involving the use of CaO in a biochar matrix (CaO/Biochar), given the support essential role in making the CaO use feasible. The use of catalysts derived from sugarcane bagasse biochar was also high-lighted, given this biomass importance, especially in Brazil. Studies have shown that biochar-derived catalysts have good activity, excellent stability, and can be reused for up to 10 cycles. Concerning CaO/Biochar, it was found that biochar significantly reduced Ca2+ leaching, but there is still a need to further reduce the Ca2+ release into biodiesel. There is also a need to give more focus on CaO leaching. Finally, a lack of studies on the use of catalysts derived from sugarcane bagasse biochar is notiable, showing no study involving the CaO-embedded sugarcane bagasse biochar.
