Sunday, April 29, 2007

Ethanol organosolv process: A biorefining platform for production of fuel ethanol, chemicals and materials from lignocellulosics

Xuejun Pan, Biological Systems Engineering, University of Wisconsin, 460 Henry Mall, Madison, WI 53706 and Jack N. Saddler, Wood Science, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada.

Biorefining of hardwood hybrid poplar and softwood lodgepole pine using ethanol organosolv process was investigated. The ethanol organosolv process is a unique biorefining platform different from most of the pretreatment technologies currently being widely investigated. The process uses aqueous ethanol, an inexpensive solvent and one of the main products of the bioconversion, to fractionate lignocellulosic biomass into cellulose, lignin and hemicellulose. The process calls for directly pretreating wood chips, thus eliminating the need for wood size reduction which is energy intensive and significantly compromises the process economics and energy efficiency. The results indicated that the resulting substrate fractions (rich in cellulose) were readily digestible and could be easily hydrolyzed over 90% (cellulose-to-glucose) within 24 hours with a low enzyme loading of 20 FPU/g cellulose. In addition to ethanol production, the cellulose fraction can be used as pulp for paper and further processed to dissolving pulp for cellulose derivatives. Characterization showed that the ethanol organosolv lignin precipitated after pretreatment had high purity, low molecular weight and many functional groups. The lignin was a good feedstock for production of carbon fibers, polyurethane foams and antioxidants. Monomeric and oligomeric saccharides recovered from water-soluble fraction were fermentable. The oligomeric saccharides could be used as additives in animal feed. In addition, high-value chemicals were also derived from the hemicellulosic sugars during the pretreatment, such as, furfural, hydroxymethylfurfural (HMF), and levulinic and other organic acids, which already have many applications.

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