Emerging Trends in Biodiesel Research: Engine Performance, Nano Additives and Process Innovations

Biodiesel, a renewable and biodegradable fuel, has emerged as one of the most promising alternatives to reduce fossil fuel dependency and address environmental concerns. Over the past decade, research has expanded to improve biodiesel quality and sustainability through advanced feedstocks, innovative production methods, and nano additives that enhance combustion and emission characteristics. This review consolidates the most recent findings on biodiesel engine performance, critically evaluates the role of nano additives—including their benefits and unresolved challenges—and compares emerging transesterification process enhancements. Special emphasis is placed on life cycle assessment (LCA) and techno-economic factors, as well as policy frameworks that vary geographically. While biodiesel generally improves lubrication, reduces carbon emissions, and promotes a circular economy via waste utilization, issues like higher NOx emissions, nano-particle stability, and scaling up advanced processes persist. Future directions highlight integrated solutions encompassing multi-feedstock approaches, novel catalyst designs, extended long-term engine endurance testing, and robust regulatory support to ensure biodiesel remains economically viable and environmentally benign. Specific advancements, such as reductions in CO and HC emissions by 10-20% with nano additives, underscore the potential of biodiesel as a sustainable fuel.