(679e) In-Situ Biodiesel Production From Microbial Lipids Using Supercritical Methanol

Our research group has demonstrated the production of fatty acid methyl esters (Biodiesel) using activated sludge generated from wastewater treatment facilities. Activated sludge is the microbial consortium used to treat wastewaters during conventional biological treatment. One of the main operating costs of this process is drying of the sludge prior to oil extraction. We have evaluated several alternatives to reduce biodiesel production cost from activated sludge, including in-situ transesterification and acid and base, water-tolerant, heterogeneous catalysts. The in-situ process consists of mixing the wet microbial mixture with an acid and methanol at relatively high temperature (75oC) to produce the fatty acid, methyl esters. Once the reaction is completed, the esters are separated from the mixture. One of the disadvantages of this process is the high acid concentration necessary to overcome the dilution effect of the water present in the mixture. Furthermore, the remaining acid cannot be recovered, adding to the potential process operating cost. Another, in-situ technique our group has evaluated is the use of supercritical methanol in the absence of catalyst. The wet mixture of microorganisms (15% solids) containing lipids inside the cell bodies was processed using supercritical methanol. The lipids were converted into fatty acid, methyl esters. The presentation will describe the application of the technology for several types of microbial consortiums. Additionally, an economic analysis will be presented comparing conventional biodiesel production, conventional dry and wet, in-situ esterification, and in-situ biodiesel production using supercritical methanol.