October, 2005:
In organisms that run the gamut from microbes to magnolias, photosynthesis creates biomass. Water (H2O) plus carbon dioxide (CO2) plus light energy (solar radiation) produces carbohydrates plus oxygen. Normally, no hydrogenase (a natural enzyme that promotes the formation of gaseous hydrogen) is involved in the process. But with microbes, it is possible to intervene genetically in ways that encourage the activation of hydrogenase enzymes. The end result is an altered photosynthetic process that produces less oxygen and more hydrogen.
Researchers at the National Renewable Energy Laboratory in Golden, Colorado, have already succeeded in converting solar energy directly and continuously into hydrogen by manipulating photosynthesis in Chlamydomonas reinhardtii, a common species of green algae. Biologist Michael Seibert and his colleagues found they could activate hydrogenase during photosynthesis by withholding sulfate. “This is a neat little system that shows that you can get an alga to produce hydrogen for days. In fact, we’ve now done it for about six months, continuously,” says Seibert.
Ramping up the efficiency and scale of the photosynthesis-to-hydrogen process to industrial production will be a challenge. But strange as it may seem, visions of pond scum may soon be dancing in energy analysts’ heads. Seibert offers this scenario: “Imagine if 200 million passenger vehicles in this country were fuel-cell driven—and that may be something that happens—and we could get this process working at a 10 percent conversion efficiency. Then it would take an area of bioreactors—hydrogen-impermeable covered ponds, essentially—equivalent to a square plot about 100 miles on each side in, say, New Mexico or Arizona to produce all the hydrogen needed to run those 200 million vehicles.”
No comments:
Post a Comment