From NPR News, this is ALL THINGS CONSIDERED. I'm Robert Siegel.


And I'm Audie Cornish.

Yesterday on our program, we heard that coral reefs around the world are in trouble. Carbon dioxide from fossil fuels is dissolving into oceans, making the water corrosive. One obvious solution to this problem is to phase out fossil fuels. Today, we visit some young engineers who are working on a low-carbon alternative to gasoline. They're trying to build an artificial leaf that will use energy from sunlight to produce liquid fuels.

NPR's Richard Harris has that story.

RICHARD HARRIS, BYLINE: We'd all find it much easier to address climate change if it weren't so hard to phase out fossil fuels as an energy source. Miguel Modestino first latched onto that idea when the Venezuelan native was an undergrad at the Massachusetts Institute of Technology.

MIGUEL MODESTINO: When I was a freshman, I was taking a course pretty much meant to guide you towards which career to take. And in this course, we were discussing climate change and all the changes the planet is going through.

HARRIS: Modestino planned to be a chemical engineer. And he realized those skills could be useful in tackling the climate challenge. For graduate work, he left chilly Boston for the more comfortable climes of UC Berkeley.

MODESTINO: And when I arrived here I realized there was a lot of renewable energy, clean energy research, going on in Berkeley. And so I decided to get engage in an exciting project on solar fuels.

HARRIS: Solar fuels. Right now, we use solar panels to make electricity. But solar fuels could come from a device that uses sunlight to make something that could go into our gas tank. He's now part of a team of 120 scientists, engineers and technicians at the Joint Center for Artificial Photosynthesis.

HEINZ FREI: This a Department of Energy innovation hub for fuels from sunlight.

HARRIS: Heinz Frei runs the part of the center that's affiliated with the Lawrence Berkeley National Lab. It's a joint venture with Caltech. And at the moment, the Berkeley labs are spread out in an open room that feels like a squeaky clean warehouse. Frei explains that the concept is to use sunlight as an energy source to take carbon dioxide from the air and turn it into fuel. That's exactly what green plants do.

FREI: It's like an artificial leaf but spread over very large areas.

HARRIS: You'd need a forest's worth to make a meaningful amount of fuel. At the moment, they're trying a comparatively easy task; they're trying to capture energy from the sun to split water molecules, H2O, into oxygen and hydrogen. Burn hydrogen and you can release a lot of energy. Frei says it's not simply a matter of proving the concept of artificial photosynthesis.

FREI: That has been done 10, 12 years ago

HARRIS: The challenge now is to drive down the cost, using cheap materials and increasing the efficiency. Plants are actually not very efficient at making fuel. They convert a fraction of one percent of the sunlight they soak up to make sugars, which is their version of fuels. This lab's goal is to do 10 times better. And they don't want to have hazardous hydrogen gas as their final product.

FREI: The longer-term goal is to make a liquid fuel so that it can be sent through pipes.

HARRIS: Liquid you could put into your fuel tank. One day you might see huge blue solar collectors. But instead of being hooked up to the electrical grid, they'd be dripping out a liquid that would be the starting material for a gasoline replacement.

We walk through the expansive lab, looking at millions of dollars of equipment and clusters of grad students, post-docs and other scientists hunkering down over lab benches.

FREI: Over here you have over here now...

HARRIS: John Stevens and Kenneth Lee are huddled with Venezuelan grad student Miguel Modestino, who is showing them how to use a piece of test equipment in the lab.

UNIDENTIFIED MAN: So is this still a 3-electrode setup or is this a tube?

MODESTINO: Right now, it's setup for...

HARRIS: Modestino explains that this piece of equipment does just part of the work of an artificial leaf.

MODESTINO: So what we have right here is a system that can actually operate continuously, producing hydrogen and oxygen. And it's actually, right now at this point, producing hydrogen and oxygen, electrically driven.

HARRIS: Yes, it's plugged into the wall, hardly what you'd call solar powered. But for now, it's easier to break down the problem into bits, solve each one independently, and then try to piece together a working system.

Assuming they can make their artificial leaves out of cheap material, Heinz Frei says the next challenge will be to scale it up.

FREI: For a one percent efficient system, which is modest, right, you would need for the entire country an area which is equivalent to the area we need for interstate road system.

HARRIS: Imagine the political challenge in covering thousands of square miles of grassy hillsides and the like with arrays of solar collectors. Frei acknowledges there could be some resistance to that.

FREI: Yes, but then the question becomes what's the alternative? If society refuses to accept this mode of making renewable fuel, the alternative is not doing it and going on and using fossil fuel and fowling up the atmosphere with carbon dioxide to a level where the impacts on the living world around us becomes just intolerable.

HARRIS: Graduate student Miguel Modestino thinks about that, too, as he works toward his Ph.D. Yes, he knows that he's in a hot field right now and he will no doubt be eagerly pursued when he sets out to get a job.

MODESTINO: It's just not just a great opportunity for me, for my career, but it's a great opportunity for me to impact the world in a positive manner

HARRIS: Modestino knows that building artificial leaves on a massive scale is a long shot. And even if they could create a system that's affordable and big enough to fuel our cars, trucks and airplanes, it won't be nearly enough to wean the world from fossil fuels.

We still need to build systems to replace the coal and natural gas we burn to generate electricity, and that's an even taller order. But you have to start somewhere, and these young scientists find this to be an exciting frontier.

Richard Harris, NPR News.

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