Ground-Level Research on Carbon Removal

7 February 2024
By Jane Turpin Moore ’87 | Artwork by Clare Walker Leslie ’68

Six acres of farmland a stone’s throw northeast of the Hill of Three Oaks are proving fertile ground for consequential geoscience research.

Dan Maxbauer, assistant professor of geology, is in the midst of a three-year field trial that’s testing carbon removal efficiency and exploring the potential benefits to crops and soils resulting from applications of crushed silicate minerals.

The project, which investigates a promising carbon dioxide removal technology known as enhanced weathering, has involved more than a dozen Carleton students to date.

“I love the idea of local work, and COVID helped spur this,” says Maxbauer, a Carleton faculty member since 2017. “Everything travel-related was canceled during the summer of 2020, giving me an excuse to jump into this with 100 percent effort.”

With the availability of agricultural land essentially on campus, Maxbauer was well positioned to use the National Science Foundation grant he’d secured. In partnership with two local farmers, alternating annual crops of corn and soybeans are infused with crushed basalt (10 tons per acre) or steel slag (two tons per acre) rather than crushed limestone, a material used for centuries by producers seeking to balance soil acidity.

“Enhanced rock weathering tries to target the ideal rocks and minerals for pulverizing and spreading in areas to neutralize acids or CO2 and increase the amount of inorganic carbon that’s dissolved into surface waters,” Maxbauer explains.

Although using crushed volcanic rocks for agricultural purposes didn’t originate with Maxbauer, the idea of distributing them on a large scale for carbon dioxide removal and reduction is newer.

“We’ve measured many things, including crop yields, and while some outcomes have been inconclusive, there are exciting indications the steel slag is acting to remove carbon at the point of initial reaction in the soil,” Maxbauer reports. “And that’s great.”

“The potential exists to do this on a large scale,” Maxbauer adds. “If we find this is removing carbon within time periods that matter for humans, it needs to happen quickly. The fundamental focus of our research is trying to determine how easily and accurately this can be done to have a fairly large impact.”

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