Pass Those
Peas—or Put 'Em in the Gas Tank
"Eat those peas!" How
many times have you heard that from
your parents?
Well, one day, peas might be more
than just those little wrinkled green
things staring up at you from your
plate. That's because scientists with
the Agricultural Research Service (ARS)
in Peoria, Illinois, have figured out
how to turn peas into fuel.
That's right, fuel—the kind
that goes into cars, trucks, and other
vehicles.
Sound crazy? It's not, really. Have
you heard of ethanol (say "ETH-uh-nol")?
It's a fuel made from sugars naturally
found in starch—the same
silky smooth powder used to thicken
gravy and soups. Definition also given at story's end.
Peas also contain starch. But until
2005, no one had figured out how to
make fuel out of the sugars in pea
starch. That year, some Illinois farmers
asked ARS scientists Nancy Nichols
and Bruce Dien to give it a try. They
both had learned a lot about turning
cornstarch into ethanol as part of
their studies at ARS's National Center
for Agricultural Utilization Research
in Peoria.
Most of the peas that U.S. farmers
grow are sold as a protein-packed feed
for farm animals. The rest are sold
for people to eat as dried, split peas
in soups, salads, and other foods. The
Illinois farmers hoped to earn more
money from their peas, though, by turning
the crop's starch into ethanol.
Taking Peas Apart
In studies at Peoria, Nichols and
Dien experimented with different
methods until they found one that
worked best. First, they ground
hard, dried peas into a flour.
Then, they separated the starch
from protein. Next, they broke
the starch down into sugars. Using
substances called enzymes (say "EN-zimes")
or special yeasts, the scientists
fermented the sugars. This caused
them to produce carbon dioxide (the
same gas that makes sodas bubbly)
and alcohol, or ethanol. Enzymes and carbon dioxide are further defined at story's end.
What's so special about ethanol,
anyway? Why don't we just use gasoline?
One reason is that when ethanol burns,
it releases fewer chemicals that
can pollute the air. Another reason
is that gasoline comes from petroleum
(say "peh-TROL-ee-um"),
an oily liquid that is pumped out
of the ground. Once the petroleum
is gone, there's no replacing it.
But corn, peas, and other starch-producing
crops are easily replaced; farmers
need only reseed them from year to
year.
Peas produce less ethanol than corn—about
2 gallons (two big milk jugs) per bushel instead
of nearly
3. But pea starch is just as easy
to ferment. Besides earning a little
more cash from their pea crop to
make ethanol, farmers could also
sell the leftover protein.
Don’t forget, though, peas
are good for you. So next time somebody
passes them around at dinnertime,
go ahead and give them a try.
Definitions:
Starch: A a type of carbohydrate (say "car-bo-HI-drate"), a sugar that's used by plants as food. Besides peas and corn, rice and wheat are two other starch-producing crops.
Enzymes: Special proteins that trigger chemical reactions inside cells, like turning plant sugars into alcohol. The enzymes themselves don't change, though, and they're not damaged by the chemical reactions.
Carbon dioxide: A colorless odorless gas that's naturally present in the air. Plants use carbon dioxide to produce their food, and we naturally exhale carbon dioxide after taking a breath. Other human activities, like burning coal or gasoline, also release carbon dioxide. High up in the atmosphere, increasing levels of carbon dioxide and some other gases have interfered with the Earth's ability to vent some of its heat into space, causing climate changes around the world.
By Jan Suszkiw, Agricultural
Research Service, Information Staff
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