Global Challenges/Chemistry Solutions

New Fuels: Biofuels: A more economical process for making ethanol from non-food sources

June 10, 2010



Switch grass swaying in the breeze
could become a more economical
source of ethanol to power cars down
the highway thanks to discovery of a
way to reduce the cost of making
ethanol from non-food biomass.

Credit: U.S. Dept. of Agriculture
(High-resolution version)

Summary

Scientists in Wisconsin are reporting discovery of a way
to lower the cost of converting wood, corn stalks and
leaves, switch grass, and other non-food biomass
materials into ethanol fuel. The process reduces amounts
of costly enzymes needed to break down tough fibrous
cellulose matter in biomass for fermentation into alcohol.

Scientists in Wisconsin are reporting discovery of a way to lower the cost of converting wood, corn stalks and leaves, switch grass, and other non-food biomass materials into ethanol fuel. The process reduces amounts of costly enzymes needed to break down tough fibrous cellulose matter in biomass for fermentation into alcohol.

The finding could have a major impact on the economics of cellulose to biofuels conversions. The founder of Cellulose Sciences International in Madison, Wisconsin, Rajai Atalla says it could make cellulose significantly more competitive with corn as the primary source of glucose as a feedstock for biofuels.

Atalla described this process at the 239th National Meeting of the American Chemical Society in San Francisco:

“The theme of the national meeting of the ACS is chemistry for a sustainable world, and I believe it’s appropriate that we’re making our first public report on this work at this meeting. As perhaps you’re aware, cellulose is the most abundant of renewable resources because it’s the primary structural component of all plant cell walls. It’s been used since the beginning of time in textiles and paper. It is logical since it was the primary source of energy in olden times that this is the resource that would be considered for generating liquid biofuels.”

Indeed ethanol has become a mainstay in stretching out supplies of gasoline as the United States and other countries seek renewable sources of energy to help reduce dependence on fossil fuels and imported oil. But most of the ethanol added to gasoline comes not from cellulose but from the starch and sugar in corn, sugar beets, sugar cane, and other food crops. There have been questions, though, on whether the utilization of starch can be sustained and about its immediate impact in increasing food prices and reducing the availability of food.

Atalla’s involvement with research on cellulose dates to the 1960s, but it was a recent experience that inspired much of his focus on ethanol from cellulose rather than corn. In 2007, he read about people in Mexico struggling with the high cost of corn due to increased demand for corn to make ethanol.

“I thought to myself, ‘This is ridiculous.’ If we can produce it from cellulose, we would not be competing with food products. The key issue here is corn-based ethanol is fine except that it continues primarily from subsidies and it’s putting away a significant amount of food crop away from the market. It seemed to me if I had the knowledge and expertise to do it out of cellulose I should try.”

The conversion to glucose from cellulose has long remained a challenge for scientists because of its resistance to change into simpler sugars. The process that Atalla and colleagues have developed makes cellulose break down more easily, and it consumes less energy than other biofuel conversion processes, such as biomass gasification.

Experiments showed Atalla’s team was able to convert up to 80 percent more cellulose when compared to traditional conversion processes.

Here’s Dr. Atalla:

“Our process makes the cellulose porous at the nanoscale level so that the enzymes, which are typically four to six nanometers in diameter, can penetrate into the cellulose. It’s almost like making the microscopic particles of cellulose into small nanoscale sponges. Our process once it is optimized, we expect it’s going to be able bring down the cost of enzymes by a factor of 10.”

Atalla says the per gallon cost of enzymes for starch is about two cents, but the same amount for cellulose is a whopping 25 times more expensive. His new process could reduce the price of cellulosic enzymes to only four cents per gallon, making cellulosic ethanol an economically viable competitor to ethanol from starch.

Smart chemists. Innovative thinking.

Smart chemists. Innovative thinking. That’s the key to solving global challenges of the 21st Century. Be sure to check our previous podcast episodes on new fuels. Today’s podcast was written by John Simpson. For the American Chemical Society, I’m Adam Dylewski in Washington.