Catalytic applications of biochar in biodiesel production: Insights and comparisons with Sulfonated chars

The urgent need to mitigate climate change demands the development of low‐carbon fuels, especially for the aviation and maritime sectors where internal combustion engines remain essential and alternatives like batteries and hydrogen face limitations. This review examines biomass‐derived carbon‐based heterogeneous catalysts as a sustainable route for biodiesel production from waste cooking oils and non‐edible fats. Transesterification of triglycerides and esterification of free fatty acids benefit from such catalysts owing to their reusability, ease of recovery, and lower downstream processing requirements. Evidence from books, patents, and peer‐reviewed studies shows that tailoring the surface area, porosity, and acidity of biochar and hydrochar – particularly through sulfonation (–SO 3 H functionalization) – enhances catalytic performance. Interdisciplinary insights highlight opportunities for improving efficiency and durability, while challenges such as sulfonic group leaching and catalyst deactivation are critically assessed alongside regeneration strategies. Economic analyses confirm the viability of biodiesel production, with char‐based catalysts improving sustainability by valorizing biomass waste and reducing chemical dependence. Future directions include scalable catalyst fabrication, integration into circular bioeconomy frameworks, and deeper mechanistic studies. Overall, this work underscores the global relevance of char‐based catalysts for advancing biodiesel as a cost‐effective and environmentally responsible alternative to fossil fuels.