Submitted to: Annual Meeting and Expo of the American Oil Chemists' Society
Publication Type: Abstract Only
Publication Acceptance Date: 1/15/2004
Publication Date: 5/1/2004
Citation: Haas, M.J., McAloon, A.J., Scott, K.M. 2004. Production of fatty acid esters by direct alkaline transesterification: process optimization for improved economics [abstract]. Annual Meeting and Expo of the American Oil Chemists' Society. p. 76.
Technical Abstract: We have recently described a new method for the production of fatty acid esters, for use as biodiesel, from the triacylglycerols residing in oilseeds. This method involves incubation of the oilseeds themselves in alkaline alcohol solutions at ambient temperature and pressure, using the same reagents as are employed in industry for the transesterification of purified oils and fats. This novel technique eliminates the need for isolation and purification of the oil prior to transesterification, and thus could reduce the cost of biodiesel by simplifying its production. To achieve near-quantitative transesterification of the oil within flaked soybeans by this process, however, it was necessary to use a 543-fold molar excess of methanol over acylglyerol. An economic analysis of the process resulted in an estimated production cost greater than US$ 3.00/gal of biodiesel. This is much greater than the typical current cost of biodiesel production using contemporary technology. The major contributor to this elevated cost was the expense of recovering the large amount of unreacted methanol. We have now determined that the requirement for a large excess of methanol is due to the moisture naturally present in the soybeans. By drying the soy flake substrate it was possible to substantially reduce the methanol input necessary to achieve high degrees of transesterification. Here we describe (a) the relationship between the moisture content of the substrate and the reaction conditions required for high level transesterification, (b) optimized conditions for methyl ester production from dried soy flakes, and (c) overall process economics for reactions using soy flakes containing various amounts of moisture.