Effect of the alcohol type used in the production of waste cooking oil biodiesel on diesel performance and emissions

Experimental results were obtained by testing two different alcohol-derived biodiesel fuels: methyl ester and ethyl ester, both obtained from waste cooking oil. These biodiesel fuels were tested pure and blended (30% and 70% biodiesel content, volume basis) with a diesel reference fuel, which was tested too, in a 2.2 l, common-rail injection diesel engine. The operation modes were selected to simulate the European Driving Cycle. Pure biodiesel fuels, compared to the reference fuel, resulted in a slight increase in fuel consumption, in very slight differences in NOx emissions, and in sharp reductions in total hydrocarbon emissions, smoke opacity and particle emissions (both in mass and number), despite the increasing volatile organic fraction of the particulate matter. The type of alcohol used in the production process was found to have a significant effect on the total hydrocarbon emissions and on the particulate matter composition. As the alcohol used was more volatile, both the hydrocarbon emissions and volatile organic fraction of the particulate matter were observed to increase.