ABSTRACT

This study investigated the potentials ofthree different biodiesel feedstock (jatropha, cottonseed and waste cooking oil) as alternative fuels for diesel engines. It involved the fuel production, as well as the engine performance and their analysis phase. In the first phase, jatropha, cotton seed and waste cooking oils (WCO) were extracted and transesterified by heating them with anhydrous methanol using potassium hydroxide as a catalyst to hasten the reaction. The fuel properties (such as kinematic viscosity, Cetane number, density, flash and boiling points, cloud and pour points. methanol values, water contents and heats ofcombustion (lower calorific values)) were determined for each feedstock and compared with those ofthe fossil diesel and the American Standard Testing and Materials (ASTM) recommended values for biodiesel. From the analysis, the calorific values of the biodiesel feedstock (41.23, 41.18 and 40.01 MJ/kg for the jatropha, cottonseed and WCO) were lower than that of the fossil diesel (45.345MJ/kg), while their viscosities (3.97, 3.65 and 4.1mm/s2), flash points (121, 123 and 130°C) and Cetane numbers (51.2, 51.8 and 52) were respectively higher than that of the fossil diesel fuel values (3.41mm/s2, 65°C and 46). In the second phase, a diesel engine was fuelled with the three biodiesel samples and fossil diesel fuel. one after the other, and the engine performance criteria (indicated power, brake power, brake thermal efficiency, mechanical and volumetric efficiencies as well as specific fuel consumption) comparatively analyzed. The results revealed that the biodiesel samples exhibited similar performances on the diesel engine when compared to the fossil diesel, and possessed better emission characteristics, as the preferred fuels for powering diesel engines. Cotton seed oil biodiesel from the study, performed best than the other two biodiesel samples, due mainly to its higher energy content (calorific value) as well as its lower density. Also, the biodiesel produced from jathropha oil performed better than that from the WCO, probably because the WCO was made up of different vegetable oils which might have resulted in its high density, high viscosity and lower calorific value. The result overall, presented the biodiesels to possess higher oxygen contents than the fossil diesel fuel, resulting in better combustion ofthe biodiesel fuels.