Utilization of waste cooking oil in a light-duty DI diesel engine for cleaner emissions using bio-derived propanol

•Waste cooking oil from restaurants is recycled for use in diesel engines.•Ternary blends of WCO, n-propanol and diesel can reduce viscosity.•50% of diesel is replaced by 30% recycled component and 20% bio component.•N-propanol reduced NOx, smoke, CO and CO2 with respect to diesel. Waste cooking oil from restaurants could be efficiently reused in diesel engines by adding alcohols to make it less dense and viscous instead of preheating or trans-esterification to biodiesel. This study aims to replace diesel with waste cooking oil (WCO) as a reuse fuel and n-propanol as a renewable fuel by up to 50 %vol. Three blends D50-WCO45-PR5, D50-WCO40-PR10 and D50-WCO30-PR20 were prepared with this objective. n-propanol addition was expected to reduce the viscosity of WCO, the carcinogenic smoke emission (via its inbound oxygen) and the greenhouse gas NOx (via its higher vaporization latent heat). Fuel property tests by standard methods indicated that n-propanol reduced viscosity of WCO by 4.5 times along with densities comparable to diesel. Engine testing at the entire load spectrum revealed that, addition of n-propanol reduced NOx, smoke, CO and CO2 emissions with respect to diesel. However, addition of n-propanol to D50-WCO50 caused an increase in BSFC for all blends. BTE improved with n-propanol addition to D50-WCO50 at all loads but remained lower than diesel. Smoke emissions gradually decreased with increase in n-propanol fraction for all blends. HC emissions increased for all blends and CO emissions lowered with n-propanol addition. Both the greenhouse gas emissions of CO2 and NOx reduced with n-propanol addition. Thus WCO could be efficiently reused to reduce harmful emissions and reduce fossil fuel dependence with n-propanol addition instead of being an environmental hazard contaminating land and water resources.