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Indian Express, India
02/18/05
Corn Power
By Matthew L. Wald (NY Times)
The endless fields of corn in Midwest America 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 US 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 fertiliser
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 George W Bush called for research on ‘‘cutting-edge methods of
producing ethanol’’. 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.
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. ‘‘It’s a renewable
substitute for natural gas,’’ said Norman Reese, general manager of Frontline
Bioenergy.
(New York Times)