A new method for ethanol production could make it a more viable alternative fuel.

In his recent State of the Union address, President Bush boldly called for bioethanol to replace 75% of the oil the US imports from the Middle East by 2025.
“By applying the talent and technology of America, this country can dramatically improve our environment, move beyond a petroleum-based economy and make our dependence on Middle Eastern oil a thing of the past,” the President said.
If the US is successful in meeting Bush’s goals, ethanol could become as synonymous with alternative fuel as Kleenex is to facial tissue—the standard.

The largest hurdle that stands between getting ethanol out of corn, from which it’s derived, and into cars is the economic costs of converting the plant into sugar, many experts say. That fiscal worry may be put to rest thanks to a new pretreatment process recently created by Y.H. Percival Zhang, an assistant professor of biological systems engineering at Virginia Tech.

“The obstacle for the whole process is the pretreatment cost, it’s so high,” said Zhang. “But if you can reduce it 20%, maybe a company will want to startup a business immediately.”
Scientists agree that to be economical, corn kernels need to be saved for food and the corn stover—what’s left over—should be sent for cellulosic breakdown and eventual distillation into ethanol.
Currently corn stover, the most abundant renewable natural resource in the US, according to Zhang, is turned into ethanol through a series of treatments using chemicals and enzymes under high pressure and temperatures up to 250° C. The explosive conditions are necessary for separating sugars from the lignocellulose—the combination of lignin, hemicellulose and cellulose, which has very strong cell walls and is found in the stover. But even with this high energy and expensive process, degradation causes the sugar yield to remain relatively low.
“Yield, yield, yield—like in real estate, location, location, location—the sugar yield is the most important thing for the whole process,” said Zhang. “This is why, in my method, we have a breakthrough, because we can get a higher sugar yield.”
Zhang’s procedure, which uses a strong chemical solvent, doesn’t use high pressure and can produce a higher sugar yield at temperatures of only 50° C. But more importantly, Zhang has found a way to extract coproducts from the corn stover that can be sold to boost the economic incentive of ethanol investors.
“During the process I can separate other components of lignocellulose that have a much higher selling price than glucose,” said Zhang.
Once the lignocellulose is separated into its main components, the hemicellulose can be used to create sugars, including xylitol, a healthy sweetener beneficial for diabetes patients. The lignin will have even broader applications, said Zhang, as the natural material can be used for the industrial production of glue and carbon fiber.
Selling these co-products could be very profitable, creating a sound business model for the production of ethanol fuel.
To achieve President Bush’s 2025 goal, the US will need to produce 30 to 60 billion gallons of ethanol, said Zhang. With the higher sugar yield and proper marketing of co-products it could be both environmentally sound and economically sane to reach even beyond those numbers.

Originally published March 30, 2006


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