“In an open-air warehouse in California’s Central Valley, 40-foot-tall racks hold hundreds of trays filled with a white powder that turns crusty as it absorbs carbon dioxide from the sky,” reports the New York Times.

“The start-up that built the facility, Heirloom Carbon Technologies, calls it the first commercial plant in the United States to use direct air capture, which involves vacuuming greenhouse gases from the atmosphere.”

Another plant is operating in Iceland, and some scientists say the technique could be crucial for fighting climate change. Heirloom will take the carbon dioxide it pulls from the air and have the gas sealed permanently in concrete, where it can’t heat the planet. To earn revenue, the company is selling carbon removal credits to companies paying a premium to offset their own emissions. Microsoft has already signed a deal with Heirloom to remove 315,000 tons of carbon dioxide from the atmosphere.

The company’s first facility in Tracy, California, which opens Thursday, is fairly small. The plant can absorb a maximum of 1,000 tons of carbon dioxide per year, equal to the exhaust from about 200 cars. But Heirloom hopes to expand quickly. “We want to get to millions of tons per year,” said Shashank Samala, the company’s chief executive. “That means copying and pasting this basic design over and over.”

Heirloom’s technology hinges on a simple bit of chemistry: Limestone, one of the most abundant rocks on the planet, forms when calcium oxide binds with carbon dioxide. In nature, that process takes years. Heirloom speeds it up. At the California plant, workers heat limestone to 1,650 degrees Fahrenheit in a kiln powered by renewable electricity. Carbon dioxide is released from the limestone and pumped into a storage tank. The leftover calcium oxide, which looks like flour, is then doused with water and spread onto large trays, which are carried by robots onto tower-high racks and exposed to open air. Over three days, the white powder absorbs carbon dioxide and turns into limestone again. Then it’s back to the kiln and the cycle repeats. “That’s the beauty of this, it’s just rocks on trays,” Mr. Samala, who co-founded Heirloom in 2020, said.

The hard part, he added, was years of tweaking variables like particle size, tray spacing and moisture to speed up absorption… In future projects, Heirloom also plans to pump carbon dioxide into underground storage wells, burying it.
The company received funding from Microsoft’s Climate Innovation Fund and Bill Gates’ Breakthrough Energy Ventures, according to Bloomberg, which adds that Heirloom’s technology will later “be deployed at a major hub in Louisiana the government expects will remove 1 million tons of CO2 a year by the end of the decade.”

The New York Times notes there was also federal funding, something that’s been fueling the ambitions of hundreds of carbon-capture startups. “The science is clear,” says America’s Energy Secretary. “Cutting back carbon emissions through renewable energy alone won’t stop the damage from climate change. Direct air capture technology is a game-changing tool that gives us a shot at removing the carbon pollution that has been building in the atmosphere since the Industrial Revolution.”