Ethanol Technology Expands into Corn Stalks

A strain of yeast developed at Purdue University is helping the Canadian company Iogen more effectively make ethanol from agricultural residues that would otherwise be discarded, such as corn stalks and wheat straw. Iogen is an industrial manufacturer of enzyme products for the pulp, paper, textile and animal feed industries, and they own a non-exclusive license from Purdue for the genetically altered yeast.

West Layfayette, Indiana – July 22, 2004 [SolarAccess.com] Iogen owns and operates a cellulose ethanol demonstration scale facility that derives fuel from wheat straw. It is the final proving prior to the rollout of full-scale commercial plants. All vehicles can use a standard blend of up to 10 percent cellulose ethanol mixed with gasoline, with no changes required to the vehicle’s engine. The company is working with its partners, Petro-Canada and Shell Global Solutions, to finalize plant locations. “(This) marks the first concrete signal of a major change coming in the fuel market,” said Iogen President Brian Foody. “We have always looked to better and more efficient vehicles to reduce fossil fuel consumption. Now, new advanced fuels are ready to play a role too.” Unlike traditional ethanol feedstocks, such as corn kernels and cane sugar that contain one type of sugar, the cellulosic materials in corn stalks contain two major sugars, glucose and xylose. Saccharomyces yeast is used to ferment glucose, a six carbon sugar, but Xylose is a five-carbon sugar and cannot be fermented into ethanol by yeast or other microorganisms. The molecular genetics research group at Purdue, which is led by Nancy Ho, altered the genetic structure of the saccharomyces yeast so it will contain three additional genes that make it possible to simultaneously convert both glucose and xylose. Saccharomyces yeast has been used for centuries to make wine and bread, and is the standard microorganism used by the industry for large-scale ethanol production, Ho said. “It would cost too much money to separate the two sugars before proceeding with fermentation to ethanol, so being able to ferment both sugars together to ethanol is critical,” she said. Cellulose ethanol has at least two advantages over conventional ethanol, according to Iogen. First, the greenhouse gas emission reductions from cellulose ethanol are three times greater than those from grain based ethanol on a life cycle basis. Second, cellulose ethanol is made from a plentiful and renewable resource, the non-food portion of agriculture crops. By contrast, conventional ethanol is made from the food portion of agricultural crops, which are feed stocks that have important alternative demands. Cellulosic materials represent an opportunity to address the problem of residual crop waste, such as corn stalks from a corn crop, Ho said. “Corn-based ethanol production in the United States currently is about 3 billion gallons per year,” she said. “According to conservative estimates, 30 percent of the residue left behind in the cornfield after harvest could produce another 4 billion to 5 billion gallons annually. The use of cellulosic materials also could open up new markets for crops such as grasses, which can be grown on marginal lands.”
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