Influence of Biodiesel from Used Cooking Oil and Sunflower Oil on Engine Efficiency and Emission Profiles

This study evaluates the performance and emissions characteristics of a compression ignition engine fueled with biodiesel blends derived from used cooking oil (UO) and sunflower oil (SF) at concentrations of 5%, 10%, 20%, and 50%. Tests were conducted under different load conditions (20%, 50%, and 100%) across engine speeds ranging from 1500 to 3600 rpm, focusing on effective power, torque, brake specific fuel consumption (BSFC), and emissions of NOx, CO, HC, particulate matter (PM), smoke, and CO 2 . Consistent engine operating conditions were maintained for all fuel blends. The results indicated that increasing the biodiesel concentration led to a decrease in brake power and torque—up to 3.18% reduction for SF50 compared to diesel—due to the lower calorific value of biodiesel. For SF biodiesel, the BSFC increased with higher biodiesel content, while for UO biodiesel the results varied across concentrations. Emissions analysis revealed lower CO and HC at 2500 rpm for all biodiesel blends relative to diesel, while NOx emissions varied depending on fuel type and concentration. In terms of particles, both PM and smoke were measured, and while PM showed different results across blends, smoke was lower for all blends compared to diesel. Our overall analysis shows that biodiesel blends up to 20% can be effectively used in diesel engines without substantial modifications, offering a balance between performance and reduced emissions.