http://www.nature.com/nsu/030609/030609-14.html

Hydrogen fuel could widen ozone hole
Likely leaks blot green power's perfect reputation
13 June 2003
PHILIP BALL

[ See image from original article... ]

CAPTION:
"Extra hydrogen would wet the stratosphere. © ESA"


A hydrogen economy could create bigger, longer-lasting ozone
holes over the poles, a new study claims.

If hydrogen catches on as a 'non-polluting' fuel for energy
production, leaks from its production and transport could
increase the amount of the gas in the atmosphere. This change
would worsen ozone depletion, calculate Yuk Yung and co-workers
at the California Institute of Technology in Pasadena 1.

In a world of imperfect technology, their research suggests,
hydrogen is not quite the perfect green fuel it is sometimes
made out to be. Although its environmental benefits would
still far outweigh any drawbacks.

Cell out

Devices called fuel cells convert the energy from burning
hydrogen directly into electricity. Using these in place of
internal combustion engines to power vehicles would drastically
reduce emissions of greenhouse gases, which cause global warming,
and cut pollutants such as nitrogen oxides, carbon monoxide and
small carbon particles.

The world's major automobile companies are currently exploring
fuel-cell technology. President George W. Bush has even pledged
US$1.2 billion to develop a commercially viable hydrogen-fuelled
vehicle.

The idea of a broader hydrogen economy, with the gas fuelling
other power-generation demands still faces big hurdles - not least
the problem of making hydrogen without relying on fossil-fuel
energy - but world leaders are keen to see it happen.

Gas leak

Yung's team estimates that around 10% of all hydrogen manufactured
will leak into the atmosphere during production, storage and
transport. Current losses are already greater than this.

If so, and if all fossil-fuel energy generation were to be replaced
by hydrogen fuel cells, around 60 million tonnes of human-made
hydrogen would leak into the atmosphere every year: roughly four
times the current amount. There are natural sources of hydrogen
too, so this increase would roughly double the total hydrogen
input into the atmosphere.

Being so light, hydrogen rises rapidly through the atmosphere.
In the upper reaches, or stratosphere, it reacts with oxygen
to form water.

A hydrogen economy, say the researchers, would make the
stratosphere wetter. This would cool the lower stratosphere,
particularly in the polar regions, where most hydrogen is
converted to water vapour.

This, they calculate, would disrupt the ozone layer, which
protects the Earth's surface from harmful ultraviolet light.
It could bring about up to 8% more depletion over the North
Pole, and up to 7% more over the South Pole.

Whether this will actually happen greatly depends on
how quickly a hydrogen economy is introduced. The use
of ozone-depleting CFC propellants and refrigerants has
been largely discontinued in most developed countries,
and their concentrations in the atmosphere are declining.

If it takes more than 50 years for hydrogen to become widely
used as a fuel, CFCs will have largely disappeared and ozone
depletion will no longer be a problem. By then, hydrogen
transport and production might also be less leaky.

References

NaTrompme, T. K., Shia, R.-L., Allen, M., Eiler, J. M. & Yung,
Y. L. Potential environmental impact of a hydrogen economy
on the stratosphere. Science, 300, 1740 - 1742, (2003).

© Nature News Service / Macmillan Magazines Ltd 2003

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