Comparative Analysis of Jatropha and Waste Cooking Oil Biodiesel Blends: Fuel Properties, Engine Performance, and Emissions

Abstract

This study evaluates the fuel properties, engine performance and emission characteristics of biodiesel-diesel blends prepared from Jatropha oil and waste cooking oil (WCO). Three biodiesel feedstock combinations were considered: J50W50, J70W30 and J60W40, where the notation represents the volume percentage of Jatropha biodiesel and WCO biodiesel in the biodiesel fraction. Four biodiesel-diesel blends, B20, B40, B60 and B80, were tested in a single-cylinder, four-stroke, direct-injection diesel engine at 1500 rpm and a fixed-load operating point corresponding to approximately 72% of the rated engine power. Fuel properties, brake power (BP), brake specific fuel consumption (BSFC), brake thermal efficiency (BTE) and exhaust emissions (CO₂, CO, HC and NOₓ) were measured and compared with diesel operation. The results show that biodiesel blends produced lower brake power and higher BSFC than diesel under the selected operating condition, while HC emissions were generally lower. CO and NOₓ trends were blend-dependent. However, the measured viscosity, density and calorific-value data for several high-biodiesel blends fall outside the expected ranges reported for biodiesel fuels and standards; therefore, the fuel-property results are treated as preliminary values requiring instrument calibration verification and repeated measurements. The revised analysis avoids using these questionable fuel-property values to draw strong combustion correlations and identifies J70W30-B60 CO₂ as an outlier requiring re-measurement. The study highlights the potential of Jatropha-WCO biodiesel blends while emphasizing the need for rigorous fuel-property validation before final performance-emission correlations are published.