US startup works to pull carbon from the air
TRACY, Calif. — In an open-air warehouse in California’s Central Valley, 40foot-tall racks hold hundreds of trays filled with a white powder that turns crusty as it absorbs carbon dioxide from the sky.
The startup 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, which opened 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 chief executive Shashank Samala. “That means copying and pasting this basic design over and over.”
The idea of using technology to suck carbon dioxide from the sky has gone from science fiction to big business. Hundreds of startups have emerged. The Biden administration in August awarded $1.2 billion to help several companies, including Heirloom, build larger direct air capture plants in Texas and Louisiana. Companies such as Air
bus and JPMorgan Chase are spending millions to buy carbon removal credits in order to fulfill corporate climate pledges.
Critics point out that many artificial methods of removing carbon dioxide from the air are wildly expensive, in the range of $600 per ton or higher, and some fear they could distract from efforts to reduce emissions. Environmentalists are wary of oil companies investing in the technology, fearing it could be used to prolong the use of fossil fuels.
Others say it’s essential to try. Nations have delayed cutting greenhouse gas emissions for so long, scientists say, that it is almost impossible to keep global warming at relatively tolerable levels unless countries both cut emissions sharply and also remove billions of tons of carbon dioxide from the atmosphere by midcentury, far more than can be achieved by simply planting trees.
“The science is clear: Cutting back carbon emissions through renewable energy alone won’t stop the damage from climate change,” said Energy Secretary Jennifer Granholm, who planned to attend the opening of Heirloom’s facility. “Direct air capture technology is a gamechanging tool that gives us a shot at removing the carbon pollution that has been building in the atmosphere since the Industrial Revolution.”
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,” said Samala, who cofounded Heirloom in 2020. The hard part, he added, was years of tweaking variables like particle size, tray spacing, and moisture to speed up absorption.
The carbon dioxide still needs to be dealt with. In California, Heirloom works with CarbonCure, a company that mixes the gas into concrete, where it mineralizes and can no longer escape into the air. In future projects, Heirloom also plans to pump carbon dioxide into underground storage wells, burying it.
Heirloom won’t disclose its exact costs, but experts estimate that direct air capture currently costs around $600 to $1,000 per ton of carbon dioxide, making it by far the most expensive way to curb emissions, even after new federal tax credits worth up to $180 per ton.
Heirloom has set a long-term target of $100 per ton and aims to get there, in part, through economies of scale and massproduced components. For its next plant, planned in Louisiana, Heirloom will use a more efficient kiln and a denser layout to save on land costs.
‘Direct air capture technology is a game-changing tool that gives us a shot at removing the carbon pollution.’
JENNIFER GRANHOLM
US Energy secretary
Even if direct air capture remains expensive, some customers are willing to pay.
Microsoft, which is Heirloom’s biggest customer, has set a goal of going carbon negative by 2030. That means first doing everything it can to cut emissions, such as powering data centers with renewable electricity. But the company also wants to offset emissions from activities that aren’t easy to clean up, such as the production of the cement it uses, and plans to compensate for its historical emissions.
Microsoft won’t buy traditional offsets, such as paying people to protect forests, because they are difficult to verify and may not be permanent. Pulling carbon dioxide from the air and burying it seemed more durable and easier to measure.
“Carbon removal is getting a lot attention, but there aren’t yet enough buyers out there to get to the scale we need,” said Noah Deich, deputy assistant secretary for the Energy Department’s Office of Carbon Management. “We’re trying to change that.”