When discussing climate change, carbon dioxide sucks up a lot of the air, so to speak. Less attention is spent on methane, which accounts for 20 percent of all greenhouse gas emissions but is 80 times more powerful at trapping heat.
You’ve probably already heard that cow farts are a big contributor of atmospheric methane (220 pounds every year!), but rotting organics and natural gas can also expel methane into the air. Slashing emissions involves decreasing our dependence on natural gas, recycling and composting trash, and getting cows to fart less. But a new, unique method may convert methane into a usable energy source with the help of a microscopic friend: bacteria.
On Tuesday, a team of researchers at Radboud University in the Netherlands published a paper in the journal Frontiers in Microbiology where they constructed a battery consisting of methane-munching bacteria that convert the gas into electricity.
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“This could be very useful for the energy sector,” Cornelia Welte, a microbiologist at Radboud University and study co-author, said in a press release.
Using bacteria to generate energy isn’t a new concept. Anaerobic digestion installations (also called biogas installations) capture gases like methane and carbon dioxide produced by bacteria that are digesting organic wastes. This gas is then converted into either heat or electricity—or upgraded into a form of methane that’s can be injected into natural gas pipelines or used as vehicle fuel. Currently, there are around 2,200 operating biogas systems across the U.S. and nearly 50 million micro-scale digesters worldwide (mostly in China and India), according to a 2019 report by the World Biogas Association.
But a problem with these installations is that they aren’t all that energy efficient. “Less than half of the biogas is converted into power, and this is the maximum achievable capacity,” said Welte.
To see if they could improve the energy efficiency, the researchers turned to Candidatus Methanoperedens, a bacteria that can be found in freshwater and consumes methane to survive—a process that peels away electrons. Those free electrons are used to digest another chemical called nitrate, which is made of nitrogen and oxygen.
“We create a kind of battery with two terminals,” Heleen Ouboter, a microbiologist and co-author of the study, said in the press release. At one terminal—designated the biological terminal—the researchers placed the methane-munching bacteria, and at the other terminal—a chemical terminal—they placed a stream of nitrate. This stream is gradually reduced over time, forcing the bacteria to hand over their electron scraps to an electrode leading to a mini-reactor. With this setup, the researchers were able to convert around 31 percent of the methane fed to the bacteria into electricity.
It’s impressive, but the conversion process needs to be hastened to play valuable impact in the real world. And the research team wants to run more tests to see how well this bacteria can perform the reaction in a natural environment (so far, it’s only been in the lab). But the new findings are a promising start as we try to uncover new ways to offset methane emissions and cool our planet.
