Dec. 15, 2010 at 5:35 PM ET
An ocean microbe may open a new frontier in the search for clean, renewable energy: In a sense, it makes hydrogen — a clean-burning fuel — out of the air.
The bug, a cyanobacterium called Cyanothece 51142, performs photosynthesis during the day and fixes nitrogen at night. Hydrogen is a byproduct of the nitrogen fixation process. And when you burn hydrogen, the main byproduct is water.
"This fits in very nicely in the overall green energy concept of going directly from sunlight and CO2 production to production of hydrogen," Himadri Pakrasi of Washington University in St. Louis told me.
All cyanobacteria make oxygen by splitting water — that's the photosynthesis part, he said. That oxygen, however, is toxic to nitrogenase, the key protein that fixes nitrogen and produces hydrogen.
"This bug has figured out how to do both in the same cell by using a diurnal cycle," Pakrasi said.
During the day, the bug fixes carbon dioxide via photosynthesis and stores it away in glycogen — a bunch of glucose molecules stored in one place. At night, it draws on this stored energy.
"The energy that is coming out of this glucose utilization is then used for the nitrogenase reactions, which in turn produces hydrogen," Pakrasi said.
What makes this strain of cyanobacteria outclass others, he added, is that "they know how to divide up all the things they are supposed to do in a day into daytime and nighttime activities."
The bug produces five to 10 times more hydrogen naturally than any other bug known, but we are still a long way from establishing the infrastructure for a hydrogen economy and putting these bugs to work in the real world, Pakrasi noted.
The problem comes down to engineering and physics, he said.
"Hydrogen is tomorrow's energy carrier, not today's energy carrier, because it is not the energy itself, it is how to deliver the hydrogen at the place where it is going to be used," he said.
Unlike coal and oil, hydrogen is not energy-dense. For example, to run a truck on hydrogen with today's technology would require the truck's fuel tank to be half the size of the cargo load.
Use of palladium to store hydrogen and thus make it easier to use is prohibitively expensive, he added.
"We as scientists would love to talk about how our own personal new findings are going to solve the world's energy future," Pakrasi said. "But we are not there yet."
To date, the research has been done in the lab. The next steps will be to scale up the technology and deploy it in the real world.
Pakrasi and colleagues describe the findings in the Dec. 14 online issue of Nature Communications.
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John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).