Sustainable utilization of Egyptian waste cooking oil biodiesel in diesel engines: performance and emission characteristics

Abstract This study experimentally evaluated waste cooking oil (WCO) biodiesel–diesel blends in an unmodified single-cylinder direct injection diesel engine operated at 1500 rpm under no load and 1–5 kW load conditions. Diesel and B10–B50 were compared in terms of brake-specific fuel consumption (BSFC), brake thermal efficiency (BTE), exhaust gas temperature (EGT), and CO, HC, CO 2 , and NO x concentrations. Across 1–5 kW, diesel produced a mean BSFC of 310 g kW −1 h −1 , while B20 showed the lowest value among the biodiesel blends at 320 g kW −1 h −1 . Mean BTE decreased from 29.0% for diesel (B0) to 27.8% and 27.0% for B10 and B20, respectively. Relative to diesel, B20 reduced mean CO, HC, and CO 2 concentrations by 17.5%, 13.0%, and 12.2%, respectively, but increased mean NO x by 11.5% and EGT by 5.8%. At 5 kW, B20 limited the BSFC, EGT, and NO x increases to 3.0%, 7.3%, and 8.9%, respectively, while reducing CO by 20.0%, HC by 9.1%, and CO 2 by 10.0%. Blend and load effects were significant for all responses ( p < 0.001). An equal-weight multi-criteria assessment ranked B20 first, followed by B10. B20, therefore, provided the best-balanced performance–emission compromise, whereas B10 was preferred when efficiency retention received dominant weighting.