A comparative environmental impact analysis of the soybean biodiesel production by two different technologies was done in this study. The production routes evaluated were the alkali-catalyzed (catalyst: sodium hydroxide) methylic transesterification and the enzyme-catalyzed (catalyst: lipase) ethylic transesterification. In an early work, simulations of the biodiesel production processes with the software Aspen HYSYS, from AspenTech Inc., were carried out. Now, a life cycle assessment (LCA) of the entire biodiesel production chain is done. The inventories related to each production subsystem were developed based on the mass and energy balances obtained from the simulations and on literature information. The results clearly indicated the best environmental performance of ethanol over methanol and of the enzymatic technology over the traditional alkaline technology, but also demonstrated some bottlenecks that should be attacked in a seek for more sustainable solutions.