Performance and emission characteristics of waste cooking oil biodiesel blends in sustainable fuel applications

This study examines the effect of biodiesel derived from waste cooking oil, blended with single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs), on the performance and emissions of a compression ignition engine. Experiments were conducted at torque levels of 2, 4, and 6 Nm, with the results compared to those of conventional petroleum diesel. Key performance parameters brake-specific fuel consumption (BSFC), brake-specific energy consumption (BSEC), brake thermal efficiency (BTE), and engine noise—were analyzed alongside emissions, including hydrocarbons (HC), carbon monoxide (CO), particulate matter (PM), carbon dioxide (CO 2 ), and nitrogen oxides (NOx). Biodiesel alone reduced brake-specific fuel consumption (BSFC) by 19.5%, brake-specific energy consumption (BSEC) by 5.9%, and brake thermal efficiency (BTE) by 5.8%. SWCNT additives moderated these reductions to 10.7%, 0.71%, and 3.7%, while MWCNTs showed reductions of 14.7%, 4.1%, and 6.4%. Emission analysis revealed substantial decreases in HC, CO, and PM (up to 89% for biodiesel, 95% for SWCNTs, and 96% for MWCNTs). However, CO 2 and NOx emissions increased significantly—by up to 39.9% and 79.9% with biodiesel, 55.9% and 62.2% with SWCNTs, and 50.2% and 59.9% with MWCNTs.The findings indicate that while biodiesel and CNT additives enhance engine efficiency and reduce certain pollutants, their trade-offs in CO 2 and NOx emissions necessitate further efforts to achieve a sustainable balance between performance and environmental impact.