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Conversion of Soybean Hulls to Ethanol and High-Protein Food Additives

Soybeans can be consumed directly by humans and animals, or used as a source of oil for such products as cooking oil, soap, cosmetics, resins, plastics, inks, solvents and biodiesel. In the production of oil-based products, the soybeans are mechanically separated from their hulls. The hulls may then be mixed with animal feed to increase the fiber content, protein content and amino acid profile thereof.

Dartmouth inventors have recently developed a method of using soybean hulls as a source of biomass for the production of ethanol, with subsequent recovery of unfermented solids to be used as feed additives. Generally, the production of ethanol from biomass requires three steps. The first step is a thermochemical pretreatment step involving the use of acidic or basic reagents that initiate depolymerization of complex carbohydrates at elevated temperatures. These harsh pretreatment conditions tend to degrade proteins within the biomass, thereby reducing the nutritional value and palatability of the protein. The second step is enzymatic hydrolysis of the pretreated carbohydrates to produce simple sugars. Finally, fermentation of the sugars by microorganisms, such as yeast, produces ethanol.

The Dartmouth methods for producing ethanol from soybean hulls do not require an acidic or basic pretreatment step. Elimination of this pretreatment step amounts to a significant cost savings, as pretreatment generally accounts for about 18% of the cost of producing ethanol from biomass. Further, removal of the pretreatment step prevents degradation of the proteins found in the soybean hulls. The nutrient value (and amino acid profile) of the unfermented solids is therefore preserved, and the solids may be sold as food additives suitable for consumption by a wide variety of animals, including humans.

Results indicate that up to 85 gallons of ethanol can be produced per ton of soybean hulls, and there are approximately 5 million tons of soybean hulls produced per year in the United States (USDA: www.nass.usda.gov). Thus, the Dartmouth methods may be used to produce as much as 450 million gallons of ethanol and 450,000 tons of high-protein food additives domestically. Other countries, including Brazil, have soybean crops approaching the magnitude of the U.S. crop, as well as the ethanol production technology and infrast infrastructure for use of ethanol as a transportation fuel.

This technology is claimed in the published PCT Application No. PCT/US2007/078166. We are seeking an industrial partner interested in its commercialization. (Ref: J350)

Last Updated: 7/24/12