Why a Hydrogen-Based Economy Makes Sense

"Drink your dihydrogen oxide, Dear."

It sounds outlandish to describe the world's humblest beverage thus, but it reminds us that our perceptions of the world can obscure important aspects of physical reality.

Take water, for example. The individually unseen atoms in a sip of it vanish into our bodies, then reappear elsewhere in a breath of wind, a flash of flame, or the brown organic mulch in a handful of earth. This shape-shifting is almost magical, and although I'm supposed to be a hard-nosed scientist, I sometimes feel like I'm entering a sort of shamanic trance when I glimpse the hidden atomic nature of things.

Fortunately, some investigators spend more time than the rest of us in that odd state of awareness, and by doing so they've discovered something amazing about the water we drink. It's not just sustenance for our bodies, but also a potential fuel.

If the hydrogen atoms in water are peeled away from their oxygen atom hosts, they can regroup into hydrogen gas, which is flammable. And if the combustion of that gas is harnessed, electricity can be generated from it. Though simply put, this is the reasoning behind an increasingly vigorous groundswell of interest in developing hydrogen-based economies. If we can extract hydrogen from water economically on a large enough scale, our energy-hungry planet will be literally awash in oceans of fuel.

And there's more. When hydrogen burns, it doesn't release heat-trapping carbon dioxide like coal, oil, and natural gas do. It releases water vapor, hence the name "hydro-gen." True, water vapor is also a greenhouse gas, but it doesn't pollute the air for millennia like CO2 does because it easily falls out as rain and snow. In some views of a carbon-free future, water is both fuel and exhaust, a phoenix-like substance that both consumes and renews itself in a perpetual cycle without polluting its surroundings.

How does one coax hydrogen and oxygen atoms into letting go of each other long enough to take a helpful spin through an engine or turbine? Coal and hydropower were once seen as the main sources of water-splitting energy, but that indirect approach is widely considered to be an inefficient waste of electricity except in places like Iceland, a geothermal paradise which is building hydrogen filling stations with an eye toward converting their entire transportation system by 2050 AD. The inefficiency of coal and hydropower made hydrogen seem too expensive to replace fossil fuels and it slowed the development of hydrogen-based electricity for transport, heating, and industry.

But new ways of turning water into fire are now emerging, thanks in part to an ancient technology that runs on sunlight.

Early efforts to jolt hydrogen loose from water with solar cells faced the same problems as other electrically-based methods: inefficiency and cost. But there's another potential source of solar hydrogen which is so obvious that it occurred to me, a non-engineer, decades ago while lecturing about photosynthesis. "Leaves trap sunlight with green chlorophyll and use it to split water for... hey, wait a minute..." If brainless plants figured this out millions of years ago, then why can't we?

Well, we can. Or some of us have, anyway. Plant physiologists and nanotechnologists around the world are now working out the last details of how that invisibly small botanical machinery works and adapting it for new uses. If they succeed, and I suspect they will soon, then we'll have a truly green source of energy to help wean us away from carbon-based fuels.

As best I can tell, there's no single hub of research and development into this subject; rather, the movement is sprouting weed-like from dozens of independently operating labs in a rather diffuse global network. Some teams are developing new water-splitting catalysts involving various metals, others are building co-polymer sheets that mimic photosynthetic membranes, and one group at Massachusetts Institute of Technology has even created a harmless synthetic virus that forms light-harvesting scaffolds studded with pigments and water-chopping molecules.

Imagine where this kind of direct solar hydrolysis could lead. Roofs thatched with leafy photosynthetic shingles. Lawns and golf courses pumping out clean hydrogen fuel. A self-replenishing hydrogen tank in the garage to run your lawnmower or furnace on, a recurved tailpipe on your car that directs steamy exhaust back into the fuel tank, or light-trapping tarps for emergency shelters and camping accessories.

OK, maybe I got a little carried away there. A more realistic carbon-free society might instead rely mostly on inexpensive electricity from relatively benign, thorium-based nuclear power plants, some of which could be used to supplement solar hydrogen production for aircraft and other things that don't run well on electricity. But direct solar hydrogen sources like the ones I just described could also represent important, if less centralized components of our energy landscapes.

So the next time you cross a verdant lawn, enter a lush garden, or trim a hedge, have some respect for those magical water-splitters that are rustling and photosynthesizing all around you. They've got something important to teach us.


Curt Stager is an ecologist, paleoclimatologist, and science journalist with a Ph.D. in biology and geology from Duke University. His new book is DEEP FUTURE: The Next 100,000 Years of Life on Earth (St. Martin's Press, March 2011).

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