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United States Department of Agriculture

Agricultural Research Service


Location: Sustainable Biofuels and Co-products Research

Title: Sweet sorghum biorefinery for production of fuel ethanol and value-added co-products

item Nghiem, Nhuan - John
item Nguyen, Chon
item Drapcho, Caye
item Walker, Terry

Submitted to: Biological Engineering (ASABE)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/28/2013
Publication Date: 11/8/2013
Citation: Nghiem, N.P., Nguyen, C.M., Drapcho, C.M., Walker, T.H. 2013. Sweet sorghum biorefinery for production of fuel ethanol and value-added co-products. Biological Engineering Transactions (ASABE). 6(3):143-155.

Interpretive Summary: We developed a new process to convert sweet sorghum into biofuels and value added food and feed ingredients. Previous processes to make fuel ethanol from sweet sorghum only converted the sucrose (sugar) in the stems to ethanol and left huge amounts of the crushed stems, called bagasse, to be disposed. We developed a process to treat bagasse with ammonia, which facilitated its subsequent conversion into cellulosic ethanol and also into valuable ingredients for energy drinks (ribose) and aquaculture feeds (astaxanthin). Now companies who want to make biofuels from sweet sorghum have more options for their processes and products, which should improve their economic viability so they can provide less expensive biofuels from non-food crops to meet our transportation needs.

Technical Abstract: An integrated process has been developed for a sweet-sorghum biorefinery in which all carbohydrate components of the feedstock were used for production of fuel ethanol and industrial chemicals. In the first step, the juice was extracted from the stalks. The resulted straw (bagasse) then was pretreated using the soaking in aqueous ammonia (SAA) process, which did not result in significant loss of hemicellulose, to enhance subsequent enzyme hydrolysis for production of fermentable sugars. Following pretreatment the straw was hydrolyzed first with a commercial enzyme product containing high hemicellulase activity (Accellerase XY). The xylose-rich solution obtained after solid/liquid separation was used for production of value-added co-products using suitable microorganisms. The value-added co-products produced to demonstrate the feasibility included astaxanthin and D-ribose. The residual solids then were hydrolyzed with a commercial enzyme product containing high cellulase activity (Accellerase 1500) with the juice extracted in the first step being used as make-up water. By combining the sugar in the juice with the glucose released from the residual solids by enzyme hydrolysis high ethanol concentrations could be achieved, which resulted in lower distillation cost than if pure water were used for enzyme hydrolysis and subsequent fermentation as normally performed in cellulosic ethanol production.

Last Modified: 10/16/2017
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