Investigation of Chemical Composition, Characterization and Determination of Biodiesel Content for the Oil Extracted from Waste Coffee Residue of Different Varieties of Coffee Beans Grown in Yirgachefie, Kocherea and Yirgalem Using Homogeneous Catalysis and Comparing it with Fossil Fuels

Abstract

Due to rapid population growth and development in the world there is high energy demand, energy consumption, sharp decline in petro fuels reserves, and greater environmental problems, as a result of using petroleum diesel constrained mankind to investigate newer and renewable feed stocks for liquid transportation fuels from vegetable oils by transesterification reaction. In this study oil of waste coffee residue of yirgachefie, yirgalem and kocherea (chellelleqtu) weredas were selected as potential raw from indigenous species for biodiesel production. Oil was extracted using n-hexane as a solvent from waste coffee residue of yirga chefie, yirgalem and kocherea weredas. The oil contents for yirgachefie, yirgalem and kocherea were 16.67% w/w, 19.7 % w/w and 16.9% w/w respectively. Transesterification were carried out for all oils using methanol in the presence of acidic and basic catalysts to produce biodiesel. The fatty acid methyl esters in the biodiesel prepared from the oil extracted from three waste coffee residues were analyzed by FTIR and GC-MS. Based on GC-MS analysis their chemical compositions were 37.7 wt. % methyl palmitate (C16:0), 41 wt. % methyl linoleate (C18:2), 13.5 wt. % methyl oleate (C18:1) and 8.5 wt. % methyl stearate (C18:0) for yirgachefie, 35.90 wt.% methyl palmitate (C16:0), 38.28 wt. % methyl linoleate (C18:2), 16.42 wt. % methyl oleate (C18:1) and 9.40 wt.% methyl stearate (C18:0) for kocherea and 26.62 wt. % methyl palmitate (C16:0), 35.18 wt.% methyl linoleate (C18:2), 19.72 wt. % methyl oleate (C18:1) and 18.48 wt.% methyl stearate (C18:0) for yirgalem. In addition to this the variables that affect the amount of methyl ester yield were determined and an optimum of 94.7 %, 95.84 and 94.56 fatty acid methyl ester (FAME) conversion were obtained at a methanol to oil molar ratio of 6:1, 1.0 % mass NaOH, 65 °C reaction temperature and 3 hour reaction time for yirgachefie, yirgalem and kochera respectively. The energy content of the oil and biodiesel were 38, 36.2, 37 MJ/Kg and 38.68, 38, 41 MJ/ Kg for yirgachefie, yirgalem and kochera respectively which is determined by bomb calorimeter. Other physicochemical properties of the biodiesel were determined and all these lie within the ASTM and EN biodiesel standards except acidic value. Therefore, coffee seed oil methyl ester could be used as an alternative energy resource in diesel engine.