Recent progress in biodiesel-fueled ICEs and role of nano-additives in optimizing combustion and emissions with cost analysis- a comprehensive review

Biodiesel (BD) blends are attracting global interest as renewable alternatives to conventional diesel, with Indonesia leading at B35, followed by the United States (B20), Brazil (B13), and other countries adopting blends ranging from B5 to B10. This review highlights recent advancements in the implementation of biodiesel–diesel blends, with a particular focus on the integration of nanoparticle (NP) additives, which directly supports Sustainable Development Goals (SDGs) 7, 12, and 13. Although biodiesel typically exhibits lower combustion performance due to its higher viscosity and lower calorific value, feedstocks such as palm oil, karanja, and waste cooking oil offer improved performance owing to their higher cetane numbers and oxygen content. Nevertheless, challenges such as reduced brake thermal efficiency (BTE), increased brake specific fuel consumption (BSFC), and elevated NO_x emissions remain critical obstacles. Nanoparticle additives such as cerium oxide (CeO₂) and zinc oxide (ZnO) have shown the potential to enhance BTE by up to 13.94 % and reduce BSFC by up to 50.93 %, while also lowering emissions—such as carbon monoxide (CO) by up to 76.91 % and hydrocarbons (HC) by up to 46.4 %. However, further research is required to evaluate the long-term impacts of nanoparticles on unregulated emissions, engine durability, and overall cost-effectiveness to support widespread adoption. Economic analysis indicates that the cost of producing nanoparticle-enhanced biodiesel typically ranges from $0.024 to $0.037 per megajoule (MJ), depending on feedstock type, catalyst synthesis method, and production scale. These cost levels demonstrate competitive potential compared to conventional fuels, particularly when using low-cost or waste-derived feedstocks. However, accurate levelized cost of energy (LCOE) values for nanoparticle-based biodiesel systems have yet to be extensively established and warrant further investigation.