Artificial Leaves | Green Energy News

March 22, 2009 – Vol.14 No.1

ARTIFICIAL LEAVES.
by Bruce Mulliken, Green Energy News

Plants can do it. Why can’t we?

Plants and algae take water and carbon dioxide and through a process not entirely understood, combine the two, using the energy of the Sun, to make glucose. That process is known as photosynthesis.

Without photosynthesis, mankind (and just about every other critter on the planet) wouldn’t be here today. Not only would the carbon-hydrogen-oxygen food chain fall apart, but carbon dioxide from natural sources, such as volcanoes, would have no place to go: the planet would get hotter and hotter and by now we’d be as toasty as Venus.

The oceans, forests, organic matter, as well as organic matter in soils, hold and store carbon dioxide in various ways. But for now the only human-controlled, reliable and time-tested method of absorbing and storing CO2 from the atmosphere in large amounts is to plant more trees. And that method is always under attack by those who feel the need to cut those trees down to make products we could probably live without for the most part – like paper.

While some engineers and scientists are working on ways to capture CO2 from power plants and stuff it underground (like sweeping dirt under the rug) others, such as the China National Offshore Oil Corporation (CNOOC) and Carbon Sciences, Santa Barbara (see Don’t Store CO2, Put it to Work) think that captured carbon dioxide from power plants and industrial operations can be made into useful, salable products. CNOOC is already doing this by turning waste CO2 into food grade CO2 to make the bubbly in soft drinks and is also making CO2 into plastics. Carbon Sciences says it has a biocatalytic process to turn carbon dioxide into methanol which could then be converted to other fuels.

But using CO2 from power plants and industrial operations to make things would mitigate only part of the CO2 problem, that is the CO2 that comes from those sources. Further, it would require that all power plants install the necessary equipment at considerable expense. (That expense would be offset somewhat by the sale of products made from CO2, but at this very, very, very early stage it can’t possibly be determined what the value of that offset would be.)

A wider, grander, global approach would be to somehow remove CO2 from the atmosphere. That is, do artificially what trees do naturally. Instead of relying on the long, drawn-out process of waiting for trees to do their magnificent job of scrubbing the air and turning CO2 into something useful, we might be able to do it better and faster.

To do this gets us back to nature’s not fully understood photosynthesis. Is it possible that we could develop an artificial version – artificial leaves as it were?

Researchers with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) think they might be a step closer to a process that would use sunlight to produce liquid fuels from carbon dioxide and water. They’re about half way there by developing one of the two half reactions of an artificial photosynthesis system.

That half way point is the critical photosynthetic reaction of splitting water molecules; that is, using photons in sunlight to break up water into hydrogen and oxygen. To do this they needed a photon reactive metal to be a catalyst in the breakup and found that nano-sized crystals of cobalt oxide were just the ticket. This laboratory-made, man-made, solar-powered, water-splitting, photooxidation was found by the researchers to be faster, more efficient and more productive than the job Mother Nature was doing by herself.

The next step to the complete artificial photosynthesis process will be to integrate this photon powered water splitting process with a photon powered reaction that will combine the hydrogen and oxygen from water with CO2. The researchers are working on this.

The goal of the primary researchers, Heinz Frei, a chemist with Berkeley Lab’s Physical Biosciences Division, and his postdoctoral fellow Feng Jiao, is eventually to make what amounts to artificial leaves. Those artificial leaves would make a hydrocarbon fuel that would be endlessly renewable and carbon-neutral thus not make global warming any worse than it is.

The research was performed at the Helios Solar Energy Research Center (Helios SERC), a scientific program at Berkeley Lab, which is aimed at developing fuels from sunlight.

Links:

Berkeley Lab
http://www.lbl.gov

China National Offshore Oil Corporation (CNOOC)
http://www.cnooc.com.cn/yyww/default.shtml

Carbon Sciences
http://www.carbonsciences.com