Road to hydrogen cars may not be so clean
detnews.com
Saturday, December 25, 2004
Road to hydrogen cars may not be so clean
By Keay Davidson / Scripps Howard News Service / San Francisco Chronicle
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Auto-industry ads depict hydrogen cars as the vehicular route to clean, blue skies.
President Bush is among their biggest champions.
Enthusiasm for the technology - a leading proposal to solve global warming - is shared by many scientists.
But reality could prove more complex, some critics say. Among the problems detailed at the recent American Geophysical Union conference in San Francisco:
- Hydrogen is a very "leaky" gas that could escape from cars and hydrogen plants into the atmosphere. This could set off chemical transformations that generate greenhouse gases that contribute to atmospheric warming.
- The extraction of hydrogen for cars from methane, which is currently the richest available source of hydrogen, will generate carbon dioxide, a major greenhouse gas.
- Hydrogen can also be extracted from ordinary water via a process called electrolysis. However, using current technology, mass electrolysis of water would require intense sources of energy. If those energy sources burn fossil fuels, they, too, would generate greenhouse gases.
These problems are not necessarily showstoppers, and they may be overcome by future technical innovations. In any event, many scientists believe the environmental problems posed by hydrogen cars may prove to be less severe than the problems generated by today's fossil-fuel-dependent cars.
But given such issues, some experts are cautioning that much more research is needed before the nation prematurely commits itself to developing the "hydrogen economy."
"I'm supportive of research and development, but we are at least two decades away from (deploying) the vehicles on a mass level," said MIT-educated physicist Joseph J. Romm, a former U.S. Department of Energy official. Romm's book, "The Hype About Hydrogen: Fact and Fiction in the Race to Save the Climate," was published this year by Island Press.
"Americans are very much believers in technology and optimism, and yet when you look at the compelling details" about hydrogen cars, Romm said, "it doesn't make bloody much sense."
Economically, hydrogen devices remain highly unattractive: "Fuel cells are very expensive," Romm said. "The demonstration vehicles all cost hundreds of thousands of dollars."
Atmospheric scientists, meanwhile, are trying to figure out how Earth's atmosphere would be affected by leaked hydrogen from cars, hydrogen gas stations, delivery trucks and hydrogen production plants. Unfortunately, the politicians aren't necessarily getting the best scientific advice on the atmospheric issue, said Professor Michael J. Prather of the University of California, Irvine.
A 2004 National Academy of Sciences report on "The Hydrogen Economy" was prepared by "economists and engineers, remarkably lacking any atmospheric scientist or biogeochemists who understand the natural (atmospheric) cycle of H2," said Prather, a professor of Earth system science and former editor-in- chief of Geophysical Research Letters. "It is surprising that all of these groups examining a hydrogen economy are secure in the belief that H2 is a pure fuel, safe and harmless to the environment," although studies suggest otherwise.
One problem is that hydrogen leaked into the atmosphere binds with oxygen molecules, forming water vapor and clouds. A change in cloud abundance in some regions might alter the local temperature and climate - for example, the climate might warm if the clouds trap heat like blankets, or the climate might cool if they reflect sunlight back into space.
"The widespread use of hydrogen fuel cells ... would cause stratospheric cooling, enhancement of the heterogeneous chemistry that destroys ozone, an increase in noctilucent clouds, and changes in tropospheric (lower-atmosphere) chemistry and atmosphere-biosphere interactions," scientists from Caltech and Jet Propulsion Laboratory in Pasadena proposed in the journal Science in 2003. Noctilucent clouds are eerie high-altitude clouds whose abundance, some scientists suspect, is influenced by climate change.
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