Dividing Corn Stover Makes Ethanol Conversion More Efficient

Not all parts of a corn stalk are equal, and they shouldn't be treated that way when creating cellulosic ethanol, say Purdue University researchers. When corn stover is processed to make cellulosic ethanol, everything is ground down and blended together. But a research team found that three distinct parts of the stover -- the rind, pith and leaves -- break down in different ways.

Michael Ladisch, a distinguished professor of agricultural and biological engineering and director of Purdue's Laboratory of Renewable Resources Engineering; Eduardo Ximenes, a Purdue research scientist in LORRE; and doctoral graduate student Meijuan Zeng are trying to determine if there is a better method to process corn stover and optimize efficiency.

Cellulosic ethanol is created by using enzymes to extract sugars from cellulosic feedstocks, such as corn stover, grasses and woods, and then fermenting and distilling those sugars into fuels.

"Today, researchers grind the parts together and treat it based on what's needed to get at the hardest part," Ximenes said. "We show that there are major differences in degradability among the tissues."

Stover's pith, the soft core that makes up more than half the weight of a corn stalk, is the easiest for enzymes to digest, according to the findings in two papers published in the journal Biotechnology and Bioengineering. Rind is the most difficult, while leaves fall in between. Significant amounts of lignin, the rigid compound in plant cell walls, make the cellulose resistant to hydrolosis, a process in which cellulose is broken down into sugars.