Clay from kitty litter pulls methane emissions from air

MIT and Yale University researchers have developed a new technology for counteracting methane emissions — and it relies on a cheap, abundant clay found in cat litter.

Why it matters: While carbon dioxide is more abundant and lasts longer in the atmosphere, methane is a far more potent greenhouse gas in the short term — in the first 20 years after it’s released, it causes 80 times as much warming as carbon.

That means reducing methane emissions could have a more immediate positive impact on global temperatures than efforts to stem CO2.

“So many aspects of climate change are happening faster than expected,” Drew Shindell, a professor of Earth science at Duke University, told BBC News in 2021. “We see more fires, more of the strongest hurricanes, more heatwaves, and methane is the best lever we have to reduce the growth in those over the next 30 years.”

The challenge: Most human CO2 emissions are produced by the burning of fossil fuels, so efforts to stem those emissions center on reducing fossil fuel use — replacing gas-powered cars with electric vehicles, for example — or capturing emissions at the factories and power plants that produce them.

There isn’t one dominant source of methane emissions, though — about 18% of emissions come as a byproduct of fracking and drilling operations, and the rest are emitted by everything from cows to landfills.

“A lot of the methane that comes into the atmosphere is from distributed and diffuse sources, so we started to think about how you could take that out of the atmosphere,” study co-author Desiree Plata told MIT News. 

“You could potentially generate enough heat to generate electricity at the power plant scale.”

Desiree Plata

The idea: For their study, the researchers mixed zeolite clays — a common cat litter ingredient — with a small amount of copper. Then they placed the mixture in a tube, heated it to about 300 degrees Celsius, and pumped air containing methane through the tube.

This process converted the methane into… carbon dioxide.

That’s not a perfect solution, but as Plata told Fast Company, converting 50% of the world’s methane emissions would add to the concentration of carbon in the atmosphere only slightly (from 417 parts per million to 418 PPM) while reducing global warming by 16%.

The litter advantage: This isn’t the first example of a technology to remove methane from the air, but past systems have relied on more expensive materials (e.g., platinum), higher temperatures (600+ degrees Celsius), and streams of pure oxygen.

“The 600 degrees where they run these reactors makes it almost dangerous to be around the methane [as well as the pure oxygen],” study co-author Rebecca Brenneis said. “They’re solving the problem by just creating a situation where there’s going to be an explosion.” 

The new tech can also work at lower methane concentrations than existing systems, and it could potentially even produce net energy. If the concentration of methane is greater than 5%, the conversion process creates more heat than is needed to trigger it.

“At coal mines, you could potentially generate enough heat to generate electricity at the power plant scale, which is remarkable because it means that the device could pay for itself,” Plata said. “Most air-capture solutions cost a lot of money and would never be profitable. Our technology may one day be a counterexample.”

In the field: The researchers believe their technology would be best suited for places with high concentrations of methane and existing systems to control the flow of air, such as dairy barns or coal mines.

“The key advantage of mining air is that we move a lot of it,” Plata said. “You have to pull fresh air in to enable miners to breathe, and to reduce explosion risks from enriched methane pockets. So, the volumes of air that are moved in mines are enormous.”

They now plan to use a $2 million grant from the Department of Energy to continue developing their tech — the goal is to demonstrate a proof of concept that converts methane emissions outside the lab within 18 months and have a system ready for use in coal mines within three years.  

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