Editor's Note: Solidia Technologies is one of seven private companies Inc. identified that are driving development within seven key pathways to net zero--eliminating one ton of greenhouse gases for every ton emitted.

CONCRETE IS EVERYWHERE--in our roads, bridges, the very foundations of our homes--and each step of making it generates enormous volumes of CO2. Firing cement manufacturing kilns to 1,500 degrees Celsius, the industry standard, burns massive quantities of fossil fuels. And the calcium carbonate of limestone, cement's principal ingredient, releases even more carbon dioxide as it bakes. Manufacturing one ton of concrete releases about one ton of CO2.

That untenable equation is about to change, thanks in part to ideas that Richard Riman started working on years ago. Riman, a professor of mate­rials science and engineering at Rutgers University, was watching the snow fall one day in the winter of 2005. Musing at how fluffy flakes turn into gritty material, even hard ice, he recalled chemical processes he'd developed that could turn carbon dioxide into hard carbonate substances. It struck him that using CO2 to make ­cement and concrete could be a commercially viable way to reduce emissions. In 2008, Riman and Vahit Atakan, then a Rutgers research associate, founded Solidia Technologies to develop their ideas in the field. (Atakan is now the company's chief science officer.)

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Together they reimagined three key aspects of manufacturing. First, they used less limestone, cutting CO2 emissions from the formula. Second, they turned the kiln down to about 1,200 degrees Celsius, reducing the amount of fuel needed to burn. Finally--here's their breakthrough--Solidia developed a process to cure its concrete by pumping CO2 rather than H2O into its material structure. Water is still used to mix the cement and gravel, but it's the CO2 that reacts chemically with the slurry, drying it into a hard solid. During manufacturing, a batch of Solidia concrete absorbs CO2 so voraciously that if you listen to the gas entering the curing chamber, you'll hear a hissing noise. "The mix literally inhales carbon dioxide, like a human would inhale air," says Riman.

It's the sound of decarbonization.

Add up the savings at each step, and Solidia's recipe reduces concrete's carbon footprint by up to 60 percent.

After Solidia successfully tested its process at a working cement plant in 2011, Riman stepped back. The company moved to make its CO2-injecting technology easier to install, and also began licensing its recipe; today you can buy three types of Solidia pre-cast concrete, including pavers and blocks. And it's tested its manufacturing process at 40 more plants in 10 countries.

Still, it's not easy finding manufacturing partners willing to convert their curing chambers in a trillion-dollar sector with huge capital costs that's notoriously slow to innovate. "No one ever accused the construction materials industry of being big risk-takers," says Russell Hill, who became CEO last year. "Although, in fairness, it has a lot of risks to manage."

With major cement and concrete makers adopting environmental, social, and governance programs and sustainability targets, Solidia sees an inflection point coming. The company raised $78 million in VC funding in 2021, preparing to scale up operations to meet new demand. It expects to have plants adopting Solidia technology within three years. Says Hill: "It takes a lot to steer this ship a little differently."