WEST LAFAYETTE, Ind. – After the massive combines sweep the millions of acres of corn in the fall and remove the kernels, what is left are millions of tons of stalks, cobs, husks and leaves of the corn plants.
Although this leftover material, called corn stover, provides nutrients for the soil and prevents erosion, it also has the potential for a new use: making ethanol.
Purdue University scientists say they believe they can put some of this corn stover to use as a fuel for automobile engines by converting it to ethanol. Ethanol can be used to boost octane and reduce engine knock, and it also can be blended with gasoline to make an environmentally friendly fuel.
Corn kernels. Currently ethanol can only be made in industrial quantities from starch extracted from corn kernels. However, Michael Ladisch, professor of agricultural and biological engineering, and Nancy Ho, molecular biologist, have developed a pretreatment process that also can convert the fiber left over when the starch is processed out of the corn kernel.
The process uses genetically engineered yeast, which was developed by Ho. The process is ready for development with corn stover, Ladisch said.
Corn stover fiber is different from the fiber found in the kernel but both materials contain cellulose, which can be converted into sugars and can then be fermented into ethanol.
The research is being conducted in Purdue’s Laboratory of Renewable Resources Engineering, an integrative center for biotechnology and engineering. To aid this next step in ethanol research, the Indiana Department of Commerce has given the center an $80,000 grant to modify the process.
Pilot-scale testing of the new process will be conducted at the Williams Bio-Energy facility in Pekin, Ill.
Developing a process that uses existing industrial equipment is a key to getting the technology accepted by the ethanol industry, Ladisch said.
“Then this process has the potential to greatly increase the amount of ethanol that will be produced from non-grain sources,” he said.
Increasing need. The need for ethanol is increasing. Ethanol can be used in automobile engines as a replacement for methyl tertiary butyl ether, which is a chemical derived from petroleum that is used to boost octane levels in gasoline.
The ether itself was a replacement for tetraethyl lead, but like the lead compound, scientists have found the substance causes environmental damage, and the U.S. Environmental Protection Agency is phasing out its use.
According to the Renewable Fuels Association, the United States made a record 1.77 billion gallons of ethanol in 2001.
But the U.S. Department of Energy’s National Renewable Energy Laboratory estimates that converting one-third of the nation’s corn stover to ethanol could produce an additional five billion to eight billion gallons of ethanol, enough to have a significant effect on the amount of petroleum used in this country.
More money. Nationally, about 244 million tons of corn stover is produced each year. Finding a market for corn stover could mean $10 more per acre for farmers, according to the National Renewable Energy Laboratory.
However, Purdue Extension corn specialist Bob Nielsen cautioned that before farmers strip their fields of corn stover, more needs to be known about the economic and agronomic effects.
“Crop residues provide benefits in terms of erosion control and soil moisture conservation in no-tillage systems,” Nielsen said. “Corn stover also provides nutrient recycling in the soil as it decomposes. The potential value for harvesting the stover for ethanol production would require gross returns to the farmer in excess of the cost of any additional nutrients that would be needed.”
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