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Crosscurrents

Can copying plants curb climate change?

PHOTO.ArtificialPhotosynthesis.jpeg
Nano Letters 2015 15 (5
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Schematic of the artificial photosynthesis system devised by UC Berkeley scientists

Imagine that cars that are no longer dependent on fossil fuels. Instead of gasoline, they’d run on a new fuel—called butanol—that’s made, with the help of bacteria, from three simple ingredients: sunlight, air and water.

 

Most importantly of all, this new fuel doesn’t harm the atmosphere.

 

It may sound far-fetched, but a group of UC Berkeley scientists say it’s entirely possible. To understand how, you have to take a trip to a cluster of three concrete buildings on the campus.  The architecture is not the prettiest, but named for a few of Berkeley’s greats, including Wendell Latimer, Gilbert Lewis and Joel Hildebrand—they carry a legacy.

 

These men were some of modern chemistry’s founding fathers. And today, within these walls, the chemists who are following in their footsteps are focused on the future. They’re asking: can chemistry save us from global warming?

 

Peidong Yang is a professor in high demand, jet-setting around the world as he collaborates with other scientists and promotes his research. He’s a material chemist. That means he works with silicon semi-conductors, kind of like what you find in electronics.

 

“We’re making new materials and trying to apply them to the big problems that this society is facing,” Yang says.

 

Yang has a pragmatic view of climate change. For him, it’s a calculation. Of carbon, or more specifically, carbon dioxide, where it comes from and where it goes.

 

Here’s the problem: It starts with fossil fuels. We burn them to create energy to drive our cars. The problem with that is it dumps excess carbon dioxide into the air. And that messes with the atmosphere. That’s not good.

 

But here’s where Yang found hope. Plants—you probably already know this, but I’ll tell you anyway—can carry out this almost magical process called photosynthesis. With just sunlight, CO2 and water they can make useful things—like amino acids, carbohydrates and lipids that help them grow.

 

Yang figured maybe he could devise a system that would mimic plants. The idea would be to use the same simple ingredients—sunlight, water and carbon dioxide—to make a fossil fuel substitute. A big goal. But if successful, huge.

 

Remember, Yang's a material chemist guy. In his vision of artificial photosynthesis, everything would happen on a chip. But then a few years ago, a few colleagues approached. They had an idea. They told him, maybe the chip didn’t have to do everything. Maybe bacteria could help.

 

Step two: bacteria

 

Open the door to Chris Chang’s laboratory and you’ll see rows of black lab benches, bottles filled with clear aqueous solutions, computers and other fancy machines. Overhead are large pipes filled with water, compressed air and nitrogen. Combined with the somberness of the building, it feels other-worldly, like a trip to some made-up fantasy, science fiction land.

 

Chris Chang is also a chemistry professor. An electrochemist. He leads me to a ventilated fume hood. On the other side of protective plexiglass is a small glass beaker with liquid inside. Hooked up to the beaker are clamps and wires. At its bottom is a white magnet that spins. This definitely looks like an experiment.

 

“What we have is essentially a sealed flask or sealed glass cup,” Yang says. “And then what we do is we put in these electrodes, which are hooked up to an open solar panel.”

 

He tells me that this solar chip made in Yang’s lab and about the size of a half dollar coin, captures light and converts it into electrons. Bacteria clinging to the chip’s surface then take advantage of these electrons to do chemistry.

 

“Just like you would ferment beer or bake bread,” Chang says, “What you get is these types of bacteria, or yeast in certain cases. They don’t make food, but they make chemical products that we’re interested in.”

 

The difference is these bacteria are special. They’re called acetogens. And usually, they live in sediment, below deep bodies of water. There, they take carbon dioxide, and turn it into acetate—a molecule similar to vinegar. Why do we care about acetate? Remember, the whole purpose of all this chemistry is to make fuel.

 

Carbon dioxide has one carbon, but acetate has two. That makes acetate a great building block for making complex molecules with even more carbons such as fuel.

 

But before we can get to fuel, just like a factory assembly line, there’s one more step. The researchers must feed the acetate to another kind of bacteria. This happens in yet another laboratory. Compared to Chang’s lab, it’s a relatively lively place where The Clash play loudly on a boom box stereo.

 

Step three: E. Coli

 

Joe Gallagher is a molecular biology Ph.D. student. He shows me a shaking device where bacteria grow in open flasks with a bit of liquid food inside.

“Bacteria grow really quickly and need lots of oxygen to grow,” Gallagher says. “So there are these heated boxes that shake them around and help them to grow.”

 

The bacteria inside these shaking flasks are called E. Coli, and they’re genetically modified. They’re like GMOs, except we’ll probably never eat them. Instead, as the E. Coli grow, they take the acetate made by the first bacteria, and then, depending on how they’re modified, VOILA! They make stuff!— like bio-degradable plastics, pharmaceuticals, and perhaps most importantly of all butanol, a four-carbon molecule and potential fuel.

 

“In the system that we’ve built, you would just use sunlight and carbon dioxide as your starting materials,” Gallagher says. “And then the product that you get out, you would burn it in your car.”

 

He points out just like fossil fuels, burning butanol would release carbon dioxide.

“But it’s different than petroleum-based fuels because it’s not like you’re liberating new carbon dioxide,” he says. “This is carbon dioxide that’s been recaptured.”

 

In other words, you’re not adding any more carbon dioxide to the air. It’s a new fuel with no extra CO2.

 

The three scientists admit the technology has a long way to go. They’re testing new, more efficient iterations. Then it has to be scaled up, tested and adopted.

Peidong Yang wants to go the distance, but after more than a decade of work, he says it’s gratifying they’ve made it this far. It’s a system that could help us move on from fossil fuels. Perhaps toward a better future for us all.