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  5. Rethinking carbon capture for the built environment

Rethinking carbon capture for the built environment

Matt Ginder-Vogel (left) and PhD student Noah Stern with the solid and powder forms of cement they've created with carbonate minerals. Photo by Scott Gordon.

When carbon dioxide is “captured” in industry, it’s often literally buried—“sequestered” deep underground so that it can’t enter the atmosphere and exacerbate global warming, or injected into oil and gas reserves to help extract those resources. But Matt Ginder-Vogel hopes to use his skills as an environmental engineer and chemist to elevate another paradigm—one that says CO2 doesn’t have to be just a waste product.

Before joining UW-Madison as an assistant professor of civil and environmental engineering in 2012, Ginder-Vogel spent two and a half years working for a California start-up, Calera, that captured CO2 from the flues of power plants and tried to figure out how to turn it into building materials like concrete and drywall. 

“You can make a lot of building materials out of carbon dioxide,” Ginder-Vogel says. “Very rarely do you see something where the level of carbon-dioxide emissions lines up with the potential scale of what we could make out of it.”

Now that he’s back in an academic setting, he wants to delve more deeply into the science behind the process of precipitating carbonate minerals from waste CO2, and create an economically viable way to do it.

“In industry, once you get something to work, there isn’t a whole lot of exploring why it works,” Ginder-Vogel says. “Once I started here, I wanted to investigate the fundamental chemistry behind what I had worked on in industry.”

The fundamentals of Calera’s process involved using CO2 and water to precipitate carbonate minerals, which then serve as raw materials for cement or drywall. In nature, carbonate minerals help to form coral and the shells of sea creatures. But the natural precipitation process that Ginder-Vogel and Calera sought to emulate produces them in rather low concentrations. In short, the natural conditions aren’t adequate to create enough material to supply a viable source for products. “Almost nothing is known about carbonate minerals in high-concentration solutions,” Ginder-Vogel says.

With funding from the UW-Madison Graduate School, Ginder-Vogel and PhD student Noah Stern are using an in-situ reactor to monitor the variables of the precipitation reactions, including pH levels and calcium concentration. 

“In particular Noah’s working on quantifying how fast these minerals precipitate in very concentrated solutions,” Ginder-Vogel says. “We’re trying to figure out how little water we can get away with using and still get a useful carbonate mineral.”

The possibilities go beyond the human built environment and connect back to Ginder-Vogel’s interest in natural ecosystems. He thinks there’s a far-off possibility that carbonate minerals derived from CO2 waste could one day aid in the restoration of damaged coral reefs. 

The water part of the equation, Ginder-Vogel says, was the biggest eye-opener from his time working in industry. While much of his academic career is motivated by concerns about water contamination in the natural environment, his work at Calera taught him how much water is used in industrial processes, and how expensive it is.

“I’d always been a bench chemist before—a few hundred milliliters of something, make a half-gram of solid,” he says. “On a typical day at Calera’s pilot facility, I started with 10,000 gallons of seawater with calcium chloride, another 10,000 gallons of base, and we ended up with 1,000 kilograms of product at the end of the day.”

That sheer scale is one stumbling block to making Ginder-Vogel’s and Calera’s ideas economically viable. When he gave a talk recently for the Nelson Institute for Environmental StudiesWeston Roundtable Lecture Series, audience members asked him how large a facility would have to be to capture the CO2 from a power plant and process it into raw material. “The answer is, it’s going to be almost as big as the power plant itself,” he says.

But by monitoring the chemistry and building computational models of the precipitation reactions they observe, Ginder-Vogel and Stern hope to arrive at processes that use less water and space. In turn, they just might make it easier to create useful materials from CO2 that would either be released into the atmosphere or sealed underground. 

Scott Gordon