The ability of physical pretreatment of the feedstock to reduce the alcohol requirement for high yield fatty acid methyl esters (FAME) production during the in situ transesterification of soybeans was investigated. Four physical treatments were studied: (a) dehulling and flaking, (b) dehulling, flaking and passage through a twin screw extruder, (c) passage through an expander type extruder, or (d) conversion to a flour-like consistency (1–10 μm particles) via disruption in a Pulsewave disintegrator. Following drying, optimal reaction conditions for high yield, room temperature, in situ transesterification of the lipid-linked fatty acids resident in these materials were determined. Expander and Pulsewave pretreatment did not substantially reduce the amount of methanol required for high level FAME production below that required for flaked soybeans. However, the combination of flaking, extrusion and drying achieved a minimum nearly threefold reduction in the methanol requirement compared with that for soybeans that had been only flaked and dried. The flaking/extrusion/drying regime resulted in a minimum optimal molar ratio for (methanol/substrate fatty acid) of 9:1 for effective in situ transesterification. This is a 20-fold reduction in methanol usage compared to the previously reported ratio of 181:1 for the use of flaked-only soybeans. (Haas et al. in J Am Oil Chem Soc 81:83–89, 2004).
Biodiesel Fats and oils utilization Fatty acid ester In situ transesterification Transesterification