Truth about Trade & Technology, IA
02/08/06
Corn Power Put to the Test
by: Matthew Wald
Ames, Iowa — The endless fields of corn in the Midwest can be distilled into
endless gallons of ethanol, a clean-burning, high-octane fuel that could end any
worldwide oil shortage, reduce emissions that cause global warming, and free
the United States from dependence on foreign energy.
There is only one catch: Turning corn into ethanol takes energy. For every gallon
that an ethanol manufacturing plant produces, it uses the equivalent of almost
two-fifths of a gallon of fuel (usually natural gas), and that does not count the fuel
needed to make fertilizer for the corn, run the farm machinery or truck the ethanol
to market.
The use of all that fossil fuel to make ethanol substantially reduces its value as
an alternative source of energy. Not that ethanol is useless. For one thing, it is far
easier than natural gas to use in motor vehicles.
Production is expected to hit five billion gallons this year, equal to more than 3
percent of gasoline supplies, and more ethanol distilleries are being built. [In his
State of the Union message, President Bush called for research on "cutting-edge
methods of producing ethanol."]
But if ethanol is to realize its potential, its proponents recognize that they will
have to develop new ways to make it without using so much natural gas — or
coal, as some distilleries are doing to save money.
"In this industry, you can't take a parochial view of your business," said William A.
Lee, general manager of Chippewa Valley Ethanol, in Benson, Minn., and former
chairman of the Renewable Fuels Association, an ethanol trade group. "We have
to be headed to a more sustainable future." Engineers are trying a variety of
methods. Here are several of the most promising.
Get Help From the Cow
Some companies are building ethanol plants next to cattle feeding operations, so
that corn can go through the ethanol distillery, and then residues from the
operation — basically corn, minus the starch — can go straight to the cattle as
feed.
The corn passes through the cow, and the manure may come back to the plant
and go into a contraption called an anaerobic digester, which mimics the
conditions in a cow's stomach so that bacteria can produce methane, a
component of natural gas.
Get Closer to the Cow
The corn residues, called distillers grains, can be exposed to high-temperature
steam, to turn their carbohydrates into hydrocarbons. If the distillers grains are
used as cattle feed, the resulting manure can also be exposed to steam to
produce hydrocarbons.
Ethanol takes energy to make because it requires a lot of steam. Typically, the
steam is used to blast cornstarch and water into a smooth mixture, keeping the
mixture at an ideal temperature for enzymes to break down the valuable
chemicals in the starch and for yeast to turn corn sugars into alcohol. Then the
mixture is heated to distill off the alcohol, and the remaining distillers grains are
usually dried to extend their shelf life until they can be eaten by cattle.
Some ethanol producers skip the drying, if there are enough cattle nearby that
the grains can be eaten promptly. In Sioux Center, Iowa, at the Siouxland Energy
and Livestock Cooperative, local farmers opened a plant in 2001 that is adjacent
to a 10,000-head feedlot.
By not drying the grains, Siouxland has reduced its natural-gas consumption to
24,000 B.T.U. per gallon of ethanol — meaning that the natural gas it uses has
an energy value less than one-third that of the ethanol it makes, creating 85,000
B.T.U. a gallon when burned. (This calculation does not count the electricity the
plant uses, or the diesel fuel used to haul the ethanol to a filling station.)
Make a New Kind of Gas
At the Iowa Energy Center, a state-financed lab here amid the cornfields near the
Iowa State University campus, engineers are experimenting with another
technique.
A cluster of steam pipes, gleaming steel tanks, augers and hoppers, assembled
by a start-up engineering firm called Frontline Bioenergy, is replacing natural gas
with another gas on a small scale, for now.
The new gas is made from the part of the corn plant that is not the kernel,
chopped into pieces half an inch long and dumped into a tank with steam and a
limited amount of air.
In a process called partial oxidation, the steam breaks apart the plant's
carbohydrates into two gases: elemental hydrogen and carbon monoxide. Both
burn nicely as a substitute for natural gas.
About 90 percent of the material turns to gas; some of the remainder is minerals
that can be sold for other uses. The process consumes natural gas to get started,
but after that, it burns the gas it makes to sustain itself.
"It's a renewable substitute for natural gas," said Norman Reese, general
manager of Frontline Bioenergy.
The corn parts that the process uses, called stover, are left in the field. They
could be burned directly but would be much dirtier that way.
But Back to the Cow
A variety of materials can be turned into gas, including manure.
"Manure is just partly processed biomass," said Jerod Smeenk, engineering
manager at Frontline Bioenergy.
Chippewa Valley Ethanol, the Minnesota company, plans to have a pilot-scale
plant running in about a year, using distillers grains. The choice is not ideal,
because the grains are not waste; they have a market value as cattle feed. But it
is a low-risk choice for Chippewa, which can invest in the equipment needed to
gather stover if the gasifier works as promised.
Companies like Chippewa may promote their aspiration to protect the
environment, but they are also driven by price. When the ethanol industry started
20 years ago, it took twice as much natural gas to make a gallon of ethanol as it
does now, said Mr. Lee, the general manager. But gas was much cheaper then.
Right now, Chippewa is paying as much as $12 per million B.T.U. for natural gas,
compared with $2 in the mid-1980's, and Mr. Lee said gasification "makes
economic sense" when gas costs $10 or more per million B.T.U.
At Frontline, John Reardon, the research and development manager, said of the
gasification project: "It's just a step. But our whole economy is based on fossil
energy, and we have to make a step somewhere."