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New Pre-Treatment Process for Corn Stover Could Advance Cellulosic Ethanol

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.


Rafael Seidl

This is good news. It's better to produce useful compounds from agricultural waste than from food.

Increased lignin availability should bring down the cost of carbon fibers to a point (~$3/lb) where carmakers can afford to use them more intesively for vehicle weight reduction and hence, fuel economy. Carbon fiber production ought to be a good use for all the flare gas being wasted by the oil industries of certain nations.


Good observation on the carbon fiber thing.


The more research like this I see, the more I smile. I wish them all success and a lot of profit besides.

The fact that this reduces the heat and pressure needed to pretreat the stover, as well as increase the amount of fermentible sugars, seems to indicate a better energy return.


I feel like most of the talk regarding cellulosic ethanol by-products has been focussed on agricultural feedstocks. If the excess lignin can legitimately be used to make carbon fiber materials, that seems like a much more important aspect to promote. Why have I not heard of that before???

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