Nanotechnology applications in biodiesel processing and production: A comprehensive review

The wide application of diesel engines globally and the resulting exhaust emissions have been the driving force behind producing eco-friendly alternatives to fossil diesel. Biodiesel derived from triglycerides is a promising replacement for fossil diesel due to less contribution to greenhouse gases and other harmful emissions. Transesterification is a widely adopted production method for converting triglycerides into alkyl esters, primarily owing to its superior conversion efficiency. Both homogeneous and heterogeneous catalysts, as well as enzymes, can be utilized to catalyze this process. However, commonly used catalysts often exhibit significant technical, economic, and environmental challenges, which can compromise the sustainability aspects of biodiesel production. Consequently, efforts are being directed towards developing sustainable catalysts in alignment with the United Nations Sustainable Development Goals. Among the proposed solutions, the application of nanomaterials has emerged as a promising avenue to address the limitations of conventional catalysts in the transesterification reaction. Compared with conventional catalysts, nanocatalysts have a substantially higher surface-to-volume ratio, amplifying the catalytic activity and eliminating many intrinsic limitations. In addition to their increased surface-to-volume ratio, nanocatalysts provide enhanced activity, stability, and reusability, along with greater resistance to saponification. Moreover, nanomaterials can enhance lipid extraction from feedstocks, especially from third-generation resources, due to the lack of toxicity and, subsequently, less environmental concern. While achieving promising outcomes, advancing nanotechnology as an environmentally friendly and economical approach to processing feedstocks and biodiesel production necessitates continued scrutiny. This issue is due to the potential for nanomaterials to infiltrate living systems, giving rise to various safety concerns. Thus, this review summarizes the opportunities and limitations of the mainstream applications of nanotechnology in biodiesel research.