Ethyl biodiesel production from crude soybean oil using enzymatic degumming-transesterification associated process

Abstract

Brazil is one of the largest soybean producers in the world. Biodiesel production in Brazil (specially soybean oil biodiesel) has been growing every year and demanding more effective and sustainable technologies, which is the case of enzymatic processes. Enzymatic degumming could be an alternative to provide better quality products, before biodiesel production but also, in a one reaction step as a proposal to reduce time and costs. Therefore, this work was aimed at evaluating enzymatic degumming (previously optimized) of crude soybean oil using a phospholipase cocktail associated with transesterification using lipase from Aspergillus oryzae for ethyl biodiesel production. For this, transesterification was optimized for ethanol:oil (E:O) ratio, water and lipase % through a central composite rotatable design (CCRD). Optimal conditions were used to evaluate two degumming-transesterification associated processes: i) a one-pot reaction (OPR) where degumming and transesterification were performed at the same reactor; and ii) a two-pot reaction (TPR) where oil was first degummed, followed by transesterification. The optimal transesterification condition were achieved for E:O = 4.48:1, water = 3.41 % and lipase = 2.43 %, where 97 % fatty acid ethyl esters (FAEE) were obtained. Both OPR and TPR provided biodiesels with FAEE > 94 %: TPR was the best with 97.5 % and 99.98 % before and after biodiesel purification. Mineral elements (including phosphorus) and other impurities (anions) were low, and within quality standards. Glycerol produced also presented very low content of impurities which is quite advantageous. Although lipase achieves good conversion to FAEE (95.7 ± 0.29 %) using crude oil (Control), the final biodiesel carries many impurities (P=80.07 ± 0.1 mg/kg), thus requiring subsequent biodiesel purification steps. In addition, the high impurity content generates a biodiesel that does not comply with ANP legislative standards, P<10 mg/kg. The use of enzymatic degumming in the biodiesel production process generates a biodiesel with low impurities and higher final quality, in addition to being a process that generates less effluent. Enzymatic degumming was essential for obtaining high quality biodiesel and its association with transesterification showed to be a great option for decreasing time and costs for biodiesel production.