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 (CO2), 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, CO2 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 CO2 and NOx emissions necessitate further
efforts to achieve a sustainable balance between performance and environmental impact