Biomass conversion to mixed alcohol fuels using the MixAlco process

The MixAlco process is a patented technology that converts any biodegradabl e material (e.g., sorted municipal solid waste, sewage sludge, industrial b iosludge, manure, agricultural residues, energy crops) into mixed alcohol f uels containing predominantly 2-propanol, but also higher alcohols up to 7- tridecanol. The feedstock is treated with lime to increase its digestibilit y. Then, it is fed to a fermenter in which a mixed culture of acid-forming microorganisms produces carboxylic acids. Calcium carbonate is added to the fermenter to neutralize the acids to their corresponding carboxylate salt. The dilute (similar to 3%) carboxylate salts are concentrated to 19% using an amine solvent that selectively extracts water. Drying is completed usin g multi-effect evaporators. Finally, the dry salts are thermally converted to ketones which subsequently are hydrogenated to alcohols. All the steps i n the MixAlco process have been proven at the laboratory scale. A techno-ec onomic model of the process indicates that with the tipping fees available in New York ($126/dry tonne), mixed alcohol fuels may be sold for $0.04/L ( $0.16/gal) with a 60% return on investment (ROI). With the average tipping fee in the United States rates ($63/dry tonne), mixed alcohol fuels may be sold for $0.18/L ($0.69/gal) with a 15% ROI. In the case of sugarcane bagas se, which may be obtained for about $26/dry ton, mixed alcohol fuels may be sold for $0.29/L ($1.09/gal) with a 15% ROI.