Biodiesel process intensification through catalytic enhancement and emerging reactor designs: A critical review

In recent years, biodiesel has proven to become an acceptable alternative source of energy, due to its attractive properties such as reduced emissions, renewability, and energy sustainability. In this review, the processing methodologies for biodiesel are extensively evaluated, particularly the mechanisms and theories of the intensification approaches. Recent techniques implemented to produce biodiesel vary but are aimed at addressing production challenges such as the natural mass transfer limitation of reactants, feasibility in upscaling, and ease of downstream processing. Key trends within the context of biodiesel processing technologies include, transitions from batch-type to continuous reactors for transesterification, edible to non-edible biodiesel feedstocks, homogeneous to heterogeneous catalytic transesterification, and base-type to acid catalyst driven transesterification. Overarching insights indicate that the focus of interests are converging towards modularity and greater sustainability, while maintaining feasibility in commercialisation. Techno-economic analysis revealed that there are Southeast Asian nations that have immense potential for biodiesel production, and are able to almost replace their diesel consumption completely. Different biodiesel standards have localised context to facilitate the predominant feedstock used in the production, storage and usage. Therefore, the selection of biodiesel feedstock has to ensure lowered emissions when replacing diesel to mitigate potential health hazards.