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Artificial Photosynthesis: Liquid Fuel Created from Sunlight by “Bionic Leaf”

Researchers at Harvard have developed a system of artificial photosynthesis – creating liquid fuel from sunlight, carbon dioxide, and water. Described in a new paper published in Science, the process could be a big step in reducing our dependence on fossil fuels.

Daniel Nocera, a professor of energy science at Harvard, and his colleague, Pamela Silver, have achieved the process at an efficiency of 10 percent using pure carbon dioxide – meaning that one-tenth of the energy in sunlight is captured and turned into fuel. Natural photosynthesis is far less efficient, only converting about 1 percent of solar energy into the carbohydrates used by plants.

“Bill Gates has said that to solve our energy problems, someday we need to do what photosynthesis does and that someday we might be able to do it even more efficiently than plants,” Nocera said. “That someday has arrived.”

Using sunlight, plants are able to create carbohydrates from carbon dioxide and water. The process of artificial photosynthesis is based around the same inputs – using solar energy, water, and carbon dioxide to generate energy-dense liquid fuels. The system designed by Nocera and Silver first splits water into oxygen and hydrogen before feeding the hydrogen and carbon dioxide to bacteria, a microorganism that has been bioengineered to effectively convert the carbon dioxide and hydrogen into liquid fuels.

Previous systems introduced by companies like Joule Unlimited and LanzaTech have produced biofuels using bacteria that consume carbon monoxide or carbon dioxide rather than hydrogen. According to Nocera, this new system can operate at a higher efficiency, with lower temperatures and lower costs.

“The high performance of this system is unparalleled,” said Piedong Yang of the University of California, Berkeley, who has also been working on systems to produce liquid fuels. He said Nocera’s work is “really quite amazing.”

The system can either use pure carbon dioxide in gas form, or carbon dioxide drawn from the air – indicating that the system could be carbon-neutral, therefore introducing zero additional greenhouse gases into the atmosphere. The efficiency of 10 per cent, Nocera said, is using pure carbon dioxide, but even allowing the bacteria to pull carbon dioxide from the air results in a 3 to 4 percent efficiency – still significantly higher than the natural process of photosynthesis.

“That’s the power of biology,” Nocera said. “These bioorganisms have natural carbon dioxide concentration mechanisms.”

Other artificial photosynthesis work has focused on using inorganic catalysts, rather than bacteria, to create biofuels. However, according to Dick Co, head of the Solar Fuels Institute at Northwestern University, the system designed by Nocera and Silver is unique in that it combines two normally separate fields – inorganic chemistry, to split water, and biology, to convert hydrogen and carbon dioxide into liquid fuel.

“What’s really exciting is the hybrid approach,” he said. “It’s exciting to see chemist pairing with biologists to advance the field.”

Still, the process of commercializing this new technology will take years – but with this innovative system, we’re one step closer to achieving artificial photosynthesis, turning sunlight into liquid fuel.

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