Fueling the future: Graphene-enhanced waste cooking oil biodiesel for reduced exhaust emission in diesel engines

The growing demand for sustainable and eco-friendly energy sources has intensified research into alternative fuels, particularly biodiesel derived from waste materials. This study investigates the use of waste cooking oil (WCO) biodiesel as a renewable fuel and examines the enhancement of its performance through the addition of graphene nanoparticles (GNPs). Various fuel blends, incorporating WCO biodiesel and GNPs at different concentrations, were tested in a single-cylinder diesel engine. The experimental fuels included Diesel, B15D85, D100G75, B15D85G75, and B15D85G80. Results revealed that the inclusion of GNPs significantly improved combustion characteristics, leading to increased power output and reduced brake-specific fuel consumption (BSFC). Notably, the B15D85G75 and B15D85G80 blends demonstrated power gains of 42% and 25.32%, respectively, over conventional diesel. Emission analyses indicated substantial reductions in harmful pollutants; B15D85G75 achieved a 37% reduction in CO emissions, while B15D85 recorded a 13% decrease compared to diesel. Unburned hydrocarbon (UHC) emissions at high loads were lower for biodiesel blends, with B15D85G75 and B15D85 emitting 35 ppm and 32 ppm, respectively, against 42 ppm from diesel. A remarkable 76.6% decrease in CO₂ emissions was observed with B15D85G80 at high load. Additionally, smoke opacity was reduced by 21.8%, and NOₓ emissions declined by 49.9% when using B15D85G80. Optimization using the response surface methodology identified the ideal operating parameters, yielding optimal values of 0.120 kg/kWh for BSFC, 24.934% for brake thermal efficiency, and significant reductions in CO, CO₂, UHCs, NOₓ, and smoke emissions.