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How Do You Make Greener Fuel? Copy a Leaf

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Scientists are trying to create renewable fuels by copying what plants do. (Lauren Sommer/KQED)

The fuel Californians burn getting around in cars and trucks is a big driver of climate change, accounting for more than a third of the carbon pollution the state puts out.

Researchers in Berkeley are hoping to reverse that trend that by making fuel that doesn’t come from oil or other fossil fuels. Instead, they’re turning to renewable and abundant materials, like sunlight and carbon dioxide.

Sound familiar? Green plants have already cracked the code of how to survive on light, carbon dioxide and water, through the process of photosynthesis.

“Nature has really given us a lot of things to be wowed and amazed by,” says Chris Chang, a professor at the University of California, Berkeley and Lawrence Berkeley National Laboratory. Even the lowly weeds growing outside his chemistry lab are an inspiration for this work.

UC Berkeley scientist Chris Chang demonstrates his "artificial leaf" - living microbes that absorb energy from a solar panel.
U.C. Berkeley scientist Chris Chang demonstrates his “artificial leaf” — living microbes that absorb energy from a solar panel. (Lauren Sommer/KQED)

“What we want to do is take that idea,” he says, “the idea of making something useful from water, carbon dioxide and light — things that are freely abundant, freely sustainable.”


It sounds simple, but scientists have spent decades trying to understand photosynthesis and copy it in the lab, in the hope that “artificial leaves” could one day make fuel for our cars, using carbon dioxide from the atmosphere.

Chang, along with his colleagues Peidong Yang and Michelle Chang, have come up with their own prototype, but it looks nothing like a leaf.

“It’s essentially like a fancy cup,” he says, “and we have a broth, a soup, which has got bacteria or yeast.”

Microbes are good at making complex substances, Chang says. In your kitchen, they help make yogurt or beer. He and his colleagues bioengineered microbes, changing their DNA to make other things — like biodiesel or the chemicals that make up plastics.

“The first thing we ended up making was actually natural gas,” he says.

But the microbes don’t normally run on sunlight, like a plant does. Chang could capture sunlight with a small solar panel, but the bacteria wouldn’t be able to harvest the energy and use it on their own.

So, Chang and his colleagues built something that can transfer the energy to the microbes; they built it using nanotechnology. “Something that’s way too small to see,” he says. “Orders of magnitude thinner than a human hair.”

As small as the bacteria themselves — designed just for them.

“The bacteria are like Easter-egg shaped,” he says, “and then we have nanomaterials that sit like blades of grass, sort of sticking up.”

The bacteria sit within that “nanotech grass” and absorb the energy from the solar panel.

Essentially, Chang and his team electrified life.

“This is sort of our Frankenstein-type of experiment, but if Frankenstein was solar-powered,” he says.

The team’s Frankenstein solution was no simple feat. It took several labs of chemists and biologists, who don’t normally work together, to marry a living system with a man-made one. In early versions of the prototype, the nano-materials killed off the microbes.

Microbes absorb energy from a field of "nanotech grass."
Microbes absorb energy from a field of “nanotech grass.” (Lawrence Berkeley National Lab)

The research is still in the early stages and Chang says they’re working to double the efficiency of the system.

Ultimately, looking decades ahead, the hope is that jugs of these solar-powered microbes could sit in our garages, pumping out biodiesel for our cars.

“Photosynthesis is just an absolute marvel of nature,” says Harry Atwater, director of the Joint Center for Artificial Photosynthesis (JCAP). “So it offers a really powerful template and example for us to follow.”

JCAP is a collaboration of four California institutions, including Lawrence Berkeley National Lab, and was launched five years ago with $120 million from the federal Department of Energy. The goal is to use sunlight to make liquid fuels, which are used by the transportation industry because they’re more easily stored than electricity is.

“It’s very unlikely that anytime soon either you or I are going to take a flight on an electric-powered airplane,” he says.

The center is working on creating “artificial leaves” purely through man-made chemistry, unlike Chang’s system that uses living microbes. What it’ll cost to make the fuel, and what people will pay for it are both unknown. But Atwater hopes to create usable fuels at a large scale within a generation, a pace that would mirror the success of rooftop solar panels.

“I remember when I was a kid, the idea of a photovoltaic industry that would produce significant power seemed like a far-fetched idea,” he says. “So that’s the sort of thing that gives me ultimate and profound optimism.”

And he says, copying green plants and turning carbon dioxide into fuel source, instead of a pollutant, would be a much-needed climate change solution.

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