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'Bionic Leaf' Could One Day Help Reduce CO2 In The Atmosphere04:36

Shannon Nangle and her colleagues at the Silver Lab at Harvard Medical School are working on a project that could one day help reduce a cause of global warming. (Jesse Costa/WBUR)
Shannon Nangle and her colleagues at the Silver Lab at Harvard Medical School are working on a project that could one day help reduce a cause of global warming. (Jesse Costa/WBUR)
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Shannon Nangle, a postdoctoral fellow, works in a lab at Harvard Medical School, but her focus is millions of miles away: Mars.

Mars' atmosphere is composed mainly of carbon dioxide. That's potential food for the bacteria Nangle works with. Those bacteria can turn carbon dioxide into a variety of useful compounds, including a kind of plastic that could be used to build things astronauts would need on Mars.

"[The bacteria] can actually fill up their cells with about 80 percent of this polymer," Nangle says. "It's not an ideal material for industrial processing, so what we want to do is use metabolic engineering techniques to actually modulate the material properties of this polymer such that we can use it for 3D printing, injection molding, other industrial-type machining."

Nangle's ambitions might be focused on Mars, but the work she does at Harvard Medical School could come to the rescue of Earth, as a way to help reduce one cause of global warming. She's part of a team working on a "bionic leaf."

Nangle and her colleagues at the Silver Lab have created a system that uses solar energy to split water molecules into oxygen and hydrogen. They integrated bacteria that consume the hydrogen.

"And the hydrogen that is being produced by the water-splitting electrodes serves as [the bacteria's] sole energy source," Nangle says.

The lab where Nangle works resonates with the sound of magnetic stir bars hitting the sides of glass bottles. The stir bars distribute the gases — oxygen and hydrogen — from the electrodes splitting the water. They also keep bacteria in suspension in the medium.

(Jesse Costa/WBUR)
(Jesse Costa/WBUR)

The bacteria, in turn, take carbon dioxide from air and use it to create molecules within their cells.

"The CO2 can be used much in the way that plants use CO2," Nangle says. "The bacteria are already adapted to extract it from the air in the same way that plants are."

Carbon dioxide, a greenhouse gas, traps heat in the atmosphere. If the bionic leaf project can be scaled up, the bacteria could be used to consume excess carbon dioxide from Earth's atmosphere.

The process is more efficient than photosynthesis. The bionic leaf can scrub 180 grams of carbon dioxide out of 230,000 liters of air for each kilowatt hour of energy it consumes. Put another way: It can take the carbon dioxide out of about 60,000 gallons of air for the amount of power it takes to run a window air conditioner for an hour.

This year the bionic leaf project received funding from Harvard, which for the past few years has supported research on climate change. The medical school researchers hope to build a bigger reactor for the bacteria: 5 liters, slightly more than a gallon.

It's a long way from taking enough carbon dioxide out of the atmosphere to curb global warming, but it's a first step.

This segment aired on July 19, 2017.

Fred Thys Twitter Reporter
Fred Thys reported on politics and higher education for WBUR.