Their technology could help draw enough carbon dioxide out of the air to slow down climate change.

After decades of dithering on climate change, nations now need to radically cut greenhouse gas emissions and find ways to suck down vast amounts of carbon dioxide already in the atmosphere.

In fact, studies show that the world may need to remove and safely store billions of tons of it per year by midcentury to keep global warming in check -- or pull the planet back to a safer state.

Noah McQueen, 28, cofounded Heirloom Carbon Technologies in 2020 in a bid to drive down the costs and scale up the facilities needed to do that.

As an undergraduate at the Colorado School of Mines, McQueen had been searching for ways to use their love of math and science to achieve "an impact that's bigger than myself." When they began working with Jennifer Wilcox, a chemical engineering professor who had done pioneering work on capturing carbon dioxide from industrial plants or plucking it out of the air, McQueen finally saw a way to do so.

In the years that followed, McQueen helped develop an approach to carbon removal they believe will prove effective and affordable, inspired by the natural rock weathering process that already draws down at least half a billion tons of carbon dioxide a year.

The trick is to do that far faster than nature. Heirloom heats crushed limestone to release carbon dioxide, then adds water to what's left to form calcium hydroxide, which is basically a carbon dioxide sponge. The company stacks thin layers of the material in trays exposed to the air, which react with the greenhouse gas within days, forming limestone once again. And then the process begins anew.

Heirloom intends to inject most of the resulting stream of carbon dioxide into deep wells, where it should remain permanently sequestered. But some will go into products, like concrete, that should keep the gas out of the atmosphere for decades.

The company, which has raised tens of millions of dollars in venture capital, is operating a plant in California that removes 1,000 tons of carbon dioxide per year. It's also building two plants in Louisiana that will be capable of removing and storing 320,000 tons annually. Heirloom secured funds under the Department of Energy's direct-air-capture hubs program for the larger one.

The company has distinguished itself from some of its peers by refusing to use the removed carbon dioxide for enhanced oil recovery, which helps free up additional fossil fuels from wells, or to accept money from the oil and the gas sector.

Heirloom plans to continue developing facilities and hopes to remove and sequester a billion tons of carbon dioxide from the air by 2035. As the process improves along the way, McQueen believes their approach could prove to be one of the most cost effective ways of doing so.