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You're listening to ALL THINGS CONSIDERED from NPR News.

Sunlight sends a lot of energy to the surface of the Earth. The challenge is how to capture it and turn it into fuel for cars and trucks. After all, fossil fuels won't last forever.

NPR's Richard Harris reports on one potential way to do that, using a common material you've probably never heard of.

RICHARD HARRIS: A gold star for you if you remember hearing about an element called cerium in your chemistry class. That's spelled with a C, by the way: Atomic number 58, symbol Ce.

Professor SOSSINA HAILE (Materials Science, Caltech): It's chemically similar to what we call the rare Earth metals, but it turns out not to actually be rare.

HARRIS: Caltech chemist Sossina Haile says, as a matter of fact, the metal is about as abundant as copper. And it turns out to be quite useful. She's been noodling around with cerium because, at the right temperature, you can use it to turn carbon dioxide gas and water into energy-rich fuels.

Dr. HAILE: The catch is certainly that the temperatures have to be high.

HARRIS: Really high, like nearly 3,000 degrees Fahrenheit. Obviously, this process would be utterly useless if you had to use an energy guzzling furnace to make fuels. So earlier this year, Haile got together with some colleagues in Switzerland and figured out how to put cerium inside a device that can generate those tremendous temperatures by concentrating solar energy.

And, lo and behold, they were able to take carbon dioxide and water and turn them into synthetic fuel. As they report in Science magazine, the system wasn't very efficient - less than 1 percent of the solar energy got converted into fuel. But there's hope.

Dr. HAILE: If we had a perfect reactor, we should easily get 10 percent efficient.

HARRIS: And the cerium doesn't get consumed in the reaction, so you can use it over and over again. This is starting to sound interesting.

Dr. HAILE: We went through the big numbers and said: Would this make any dent on U.S. energy production? And the answer is yes.

HARRIS: The trick, with any technology, is to figure out whether you can develop it in a practical and inexpensive way. A few years ago, the Department of Energy recognized the promise - and the perils - of technologies that use solar energy to make liquid fuels, rather than electricity, as solar panels do. It established an organization called ARPA-E, the Advanced Research Projects Agency for Energy.

Eric Toone from Duke University directs a program at ARPA-E that supports research on ideas that incorporate biology to accomplish what Haile is trying to do with straight chemistry and engineering.

Dr. ERIC TOONE (Deputy Director for Technology, ARPA-E, Duke University): The ultimate goal is the same, right? The ultimate goal is to say, How can we take solar photons and convert that into a liquid fuel at higher efficiencies than we know we can do using plants?

HARRIS: Plants right now are grown to produce biofuels, like ethanol from corn. But green plants typically convert far less than 1 percent of sunlight into fuel.

Dr. TOONE: So the name of the game is to say, well, you know, can we do better than that?

HARRIS: To find out, his agency has pumped research dollars into more than a dozen universities and small companies across the country. Most projects are just getting under way, and Toone says it's clearly too early to start picking winners and losers. But he is full of optimism.

Dr. TOONE: This is absolutely a solvable problem. Realistic time frames? I suspect we're 10 or 15 years away from actual, you know, fuels that you can buy at a pump and put into your vehicle. But I do very, very, very strongly believe that this is going to happen.

HARRIS: Caltech Professor Sossina Haile says she's not saying her approach is the best, but it is an example of something that could pan out.

Dr. HAILE: I personally viewed that the challenges that remained are very surmountable.

HARRIS: The crux here, like in all technologies, is someone needs to invest the considerable time and money to find out what's really going to work.

Dr. HAILE: This is something that a company would need to be interested to take it forward.

HARRIS: Intriguing ideas, like hers, are just the starting point for innovation.

Richard Harris, NPR News.

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