Combustion Characteristics of Waste Cooking Oil–Butanol/Diesel/Gasoline Blends for Cleaner Emission

Sustainable green biofuels could replace a significant amount of fossil fuels responsible for environmental pollution. In this study, waste cooking oil (WCO) was tested in a diesel engine either neat or blended separately with diesel, butanol and gasoline, with an additive concentration between 10% and 30% by volume. The heating values of the WCO were slightly decreased when blended with butanol, whereas they increased when blended with either gasoline or diesel. The flash point temperatures decreased. All fuel samples were non-corrosive and non-acidic. At full load, the brake specific fuel consumption of the WCO−additive fuels was approximately 1−3% higher than diesel. The thermal efficiency of the neat WCO, neat diesel and WCO−10% diesel were very close to each other, whereas, in the case of 20% butanol blend, the efficiency decreased by about 2% when compared to the neat diesel value. The WCO−butanol fuel gave the lowest NOx emission and a 0.6% lower CO2 emission than diesel. Combustion characteristics results showed stable engine operation for all blends. The combustion duration was maximal with WCO−butanol blends. The study concluded that the WCO with 10−20% butanol or fossil diesel exhibited similar performance and emission characteristics observed for neat fossil diesel.