Researchers at Virginia Tech have developed a pre-treatment process for biomass that promises to reduce the processing cost of cellulosic ethanol.
The challenge in using corn stover—the most abundant agricultural residue in the US—as an ethanol feedstock is in separating the sugars (that will be fermented into ethanol) from the lignocellulose—the combination of lignin, hemicellulose and cellulose that form plant cell walls.
Technologies are available to convert lignocellulose to sugars, but the costs are still high and sugar yields are low.
Y.H. Percival Zhang at Virginia Tech developed a pretreatment process that integrates three technologies: cellulose solvent pretreatment, concentrated acid saccharification, and organosolv.
Instead of a high pressure system that operates at between 150º and 250º C, Zhang’s reaction operates at atmospheric pressure and 50º C (120º F) to pre-treat residue to free the solid polymeric sugars.
In a several-step pretreatment system, Zhang uses a strong cellulose solvent instead of highly corrosive chemicals, high pressure, and high temperature to breakup the linkages among lignin, hemicellulose, and cellulose. There is no sugar degradation and inhibitor formation.
In the following step, he uses a highly volatile organic solvent to precipitate dissolved cellulose, extract lignin, and enable effective chemical recycling. After pretreatment and reagent recycling, lignocellulose can be fractionated into four products: lignin, hemicelluose sugars, amorphous cellulose, and acetic acid.
Co-products can generate more income, making biorefinery more profitable, and enable satellite biorefineries that fully utilize scattered lignocellulose resources. For instance, lignin has many industrial uses, from glue to polymer substitutes and carbon fiber; and xylose can be converted to a healthy sweetening additive – xylitol, or to the precursors for nylon 6.—Prof. Zhang
Zhang presented his paper on the process, “Novel lignocellulose fractionation featuring modest reaction conditions and reagent recycling, ” at the 231st American Chemical Society National Meeting in Atlanta.
Zhang and co-developer Lee Lynd have filed for a patent on the pretreatment process, which has been licensed to an ethanol start-up company, Mascoma.