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By Charles Piddock

Is urine the natura

reso ce of tomor ow?

nvironmentalists envision a "green"

future. They picture a world in which
cars, homes, and industry rely on clean,
abundant, renewable resources, such
as wind and solar radiation. That future
might be as much yellow as green, though, thanks to
another natural resource: urine.
Earth's nearly 8 billion people flush away an estimated
10 billion liters (2.6 billion gallons) of urine every day.
Domestic mammals such as cows and pigs may release
twice as much. Geraldine Botte, a chemical engineer
at Ohio University, thinks throwing all that urine away
wastes a golden opportunity. Urine contains what
some scientists have called "the fuel of the future."
That fuel is hydro9'en.
"We believe we have made a breakthrough," says
Professor Botte.

Hydrogen is the most abundant element in the universe,

It isn't easy to access, though, It doesn't exist alone, but
rather in combination with other hydrogen atoms or
other elements. An economical way must be found to
break those chemica'i bonds, That's what Botte and her
team have attempted with urine.
Urine is made up chiefly of water, ammonia, and urea.
Urea is a waste product released by the liver. As you
can see from urea's chemical formula-(H 4 Np-the
compound's molecules contain hydrogen atoms. Those
atoms are much more loosely bound to each molecule
than they are in many other compounds.
Botte and her team have developed a catalyst that
prompts urea to quickly release its hydrogen, A catalyst is
a substance that starts or speeds up a chemical reaction
while undergoing no change itself. "Our process could
lead the way to using urine on a wide scale to obtain

8 Current Science

January 21,2011

pure hydrogen," she says. "[It] works at a small fraction

of the cost of other ways of obtaining hydrogen."
Once hydrogen is captured, it can then be supplied
to fuel cells, devices that generate electricity through
a chemical reaction. Some scientists have touted
hydrogen fuel cells as the best repl,acement for today's
generators and engines, which run on fossil fuels (coal,
oil, and natural gas). Fossil fuels release air pollutants
and carbon dioxide, the greenhouse gas most scientists
blame for global warming. Fuel cells release no pollution.
And their only by-products are water and heat.
Hydrogen fuel cells power the space shuttles' electri
cal systems. They also run a number of experimental
vehicles, including motor scooters and small airplanes.
General Motors, Ford, and Honda have each built
hydrogen-powered electric cars. As of last year, how
ever, only about 200 hydrogen-powered vehicles had
hit U.S. streets and highways, all of them in California.
Most hydrogen is obtained at a very high cost
from fossil fuels and from water. Once the hydrogen
is separated, it must then be stored, generally as
liquid hydrogen under high pressure at a very low
temperature. Unless a network of stored-hydrogen
"gas stations" can be developed, mass-produced
electric vehicles powered by fuel cells remain a dream.

Urine could make that dream possible. Theoretically,

motorists might one day drive up to a "gas station" that
dispenses hydrogen fuel derived from urea using a
refining process based on Botte's research.


Botte and her team are

currently working with the US
Army to develop a portable
electric generator. It will not
only process urine into electric
power for Army units but also
purify urine into clean water.
Another group of scientists, led by Shanwen Tao
at Heriot-Watt University in Scotland, is working on a
similar urine-based power source that doesn't produce
hydrogen. It uses urine directly to generate electricity.
So far, Tao's experiments have yielded only weak electric
power from urine. He hopes that further research will
produce more impressive results, making urine-run fuel
cells a popular source of electricity.

, .

Botte believes the day is not far off when farms will
generate their own electricity from urine. "The urine
produced by cows on a dairy farm, for instance, could
be used to produce all the energy needed to run the
farm," she says. The same holds true for office buildings
and other places where large numbers of people live
or work together, she says.
Neither Botte nor Tao believes that urine will ever
meet all renewable energy needs. Still, it could be an
important part of the clean energy mix that the world
needs along with other types of energy.
"Trying to find one solution is not the answer," says
Botte. "There is room for many energy technologies,
but energy from urine should have its place."
Top: Ohio Unlve"lty; Graphic leigh Hatge,

Howa Hydrogen Fuel Cell Works

Ahydrogen fuel cell produces an electric current
(and water) from astream of identical reactions.
Here is tile basic reaction.

External Circuit

o O<iE

Amolecule of hydrogen gas
(H,) Is pumped into one side of
the fuel <ell.

f) The H, molecule splits into

two hydrogen ions (H+) and two
electrons (e). An ion is an atom
that has gained or lost one or
more electrons.
~ The hydrogen ions

move through a membrane.

[J The electrons bypass the
membrane and move through
an external circuit, creating
an electriccurrent that can be
used to run an electric motor.


Water (H,O) by-product



g ..



11 Amolecule of oxygen gas (0,1


from the air enters the other side

of the fuel cell.

III The 0, molecule splits into

two oxygen (0) atoms.

A e~

/ .l


Hydrogen molecule (H,)

o An oxygen atom combines

with the two hydrogen ions
and two electrons from the
electrical circuit to form a
molecule otwater (H,O).

III Water is released as

a harmless by-product of
the reaction.
Oxygen molecule to,)

January 21, 2011

Current Science 9