Experimental investigation of influence of methyl, ethyl and methyl-ethyl ester blends of used cooking oil on engine performances and emissions

The twin crises of fossil fuel reserves depletion and environmental degradation have motivated industrial and research community to seek alternative and renewable energy sources. Biodiesel has dominated the global scene due to numerous advantages associated with it. In this study, biodiesel was synthesized by transesterifying used cooking oil with three different alcohols: methanol, ethanol and mixed methanol-ethanol. The biodiesel samples produced using methanol, ethanol and mixed methanol-ethanol were denoted as BM, BE and BME, respectively. The properties of the biodiesel samples produced were evaluated in accordance with ASTM standards, and a B20 blend of the three kinds of biodiesel (BM20, BE20 and BME20) was tested in a compression ignition engine to evaluate its performance and emission characteristics. Results from the GC-MS analysis showed that alkyl (methyl or ethyl) ester content in BM, BE and BME samples were 97.72%, 91.83% and 84.65%, respectively, indicating that methanol-based biodiesel satisfied the minimum requirement of EN 14214 standard. In addition, a total of 27.6% methyl and 57.05% ethyl esters were contained in the BME sample, suggesting high ethyl ester conversion during methanolysis-ethanolysis reaction. CO emission values of BM20 blend were lower than those of B0, BE20 and BME20, while the B0 discharged the least NOX amongst the fuels tested. In addition, BM20 discharged the least HC compared to B0 and two other biodiesel blends. Based on this finding, it could be concluded that BM20 exhibited the best performance, combustion and emission characteristics amongst the fuels tested in diesel engine.