Wednesday, May 7, 2008 - 1:30 PM
11-01

MixAlco process: fuels and chemicals from biomass

Mark T. Holtzapple and Cesar B. Granda. Chemical Engineering, Texas A&M University, 3122 TAMU, College Station, TX 77843-3122

The MixAlco process converts any biodegradable biomass (e.g., municipal solid waste, sewage sludge, manure, agricultural residues, energy crops) into fuels (e.g., primary alcohols, secondary alcohols) and chemicals (e.g., ketones, carboxylic acids).  To enhance digestibility, the biomass is treated with lime.  Then, the lime-treated biomass is fed to a mixed culture of acid-forming microorganisms derived from a marine environment.  The acids are neutralized with either calcium carbonate or ammonium bicarbonate, thus forming the corresponding carboxylate salts.  Using vapor-compression evaporation, the carboxylate salts are concentrated.  Finally, the carboxylate salts are chemically converted to a variety of products. 

Via “acid springing,” carboxylate salts are converted to carboxylic acids, which may be hydrogenated to primary alcohols (e.g., ethanol).  Alternatively, thermal conversion produces ketones, which may be hydrogenated to secondary alcohols (e.g., isopropanol).  If desired, the alcohols can be catalytically dehydrated to hydrocarbons, such as gasoline, diesel, or jet fuel.

The advantages of the MixAlco process follow:

 

·     No sterility required in the fermentation

·     No genetically modified organisms

·     No enzyme costs

·     Wide variety of feedstocks can be employed

·     Wide variety of fuel and chemical products

·     High energy density in fuels (secondary alcohols and hydrocarbons)

·     Low capital cost

·     Low product cost

 

Recent economic evaluations indicate that primary alcohols can be sold for about $1.13/gal (15% ROI, 10-yr depreciation, 15% working capital, $53/ton biomass cost).  The capital cost is estimated to be about $0.82/annual gallon.  A demonstration plant is under construction.



Web Page: www.terrabon.com/

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