(Read a related feature on how fossil fuel use is changing Earth's carbon cycle.)
Writing in the April 15, 2007, issue of the journal Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Barber notes that recent research has identified the structure of water splitting's key enzyme, photosystem II.
Understanding this structure may help scientists replicate the enzyme artificially.
"This is a very difficult chemical problem and nature solved it," said Gary Brudvig, a biophysical chemist at Yale University who has also been researching photosystem II.
"We've first been trying to figure out how nature does the chemistry and—once we've obtained a reasonable idea of how the natural system works—we [will try] to replicate that in artificial systems."
Hydrogen produced by artificial water splitting could be used as a stand-alone fuel (related news: "Is Hydrogen the Gasoline of the Future?" [September 9, 2003]).
Alternatively, scientists could further mimic plants and combine the hydrogen with carbon compounds to produce fuels.
Many of today's carbon-based fuels are currently derived from photosynthesis that took place millions of years ago. That energy is stored in the form of oil, gas, and coal.
But, Brudvig said, a more efficient energy solution depends on duplicating natural systems rather than relying on dwindling supplies of fossil fuels.
"The first phase of using solar energy, I think, is probably to recruit natural photosynthetic systems [such as corn and other crops] that can make usable fuels" such as ethanol, he said.
"But these aren't very efficient and they may never be, because living organisms use energy to live—they use energy for processes not directly related to fuel production."
In other words, the amount of energy and other resources needed to grow crops for biofuels might be the same or greater than the energy derived for human use.
(Related news: "Ethanol Production Could Be Eco-Disaster, Brazil's Critics Say" [February 8, 2007].)
"I think to get really high efficiency, we'll have to have artificial systems come on at a later point," Brudvig said.
Imperial College's Barber agreed, noting that plant "biology solved its energy problem a very long time ago by using sunlight to split water into hydrogen and oxygen.
"If the leaf can do it, we can do it."
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