(729e) Biofuel from Spent Coffee Grounds

As the fossil fuels reserves around the world are being depleted, the need for an alternative renewable source of fuel is evident. Currently, biodiesel serves as a promising source of renewable fuel. However, it is a fairly expensive process with its feedstock comprising the major cost. Therefore, the search for alternative feedstocks is important and spent coffee grounds (SCG) can be a large and economic source of vegetable oil. The present study involves the optimization of coffee oil extraction with hexane solvent and subsequent transesterification to biodiesel. This reaction was studied using inorganic base materials as catalysts, as well as the enzyme Lipase, both in solution and immobilized. The results so far indicate that an oil yield of 20 weight % from dry SCG can be obtained, and conversions to biodiesel of up to 50% can be achieved with both forms of the enzyme catalyst, with methanol or ethanol as reactants. The immobilized lipase is prefered because it can be used for extended times in a packed bed reactor (PBR) without production of undesired soap. The reaction kinetics were also studied in a lab scale PBR.