Scientists are exploring ways to use mineral waste from mines to pull huge amounts of carbon dioxide out of the air.
On a scorching day this August, Caleb Woodall wielded his shovel like a spear, stabbing it into the hardened crust of an asbestos-filled pit near Coalinga, California.
Woodall, a graduate student at Worcester Polytechnic Institute in Massachusetts, was digging out samples from an asbestos mine that’s been shuttered since 1980, a Superfund site on the highest peak in the state’s Diablo Range. He extracted pounds of the material from several locations across San Benito Mountain, shoveled them into Ziploc bags, and shipped them to a pair of labs for analysis.
He and his colleagues are trying to determine the makeup and structure of the materials pulled from the pits, and to answer two critical questions: How much carbon dioxide do they contain—and how much more could they store?
The vast surface area of certain types of fibrous asbestos, a class of carcinogenic compounds once heavily used in heat-resistant building materials, makes them particularly good at grabbing hold of the carbon dioxide molecules dissolved in rainwater or floating through the air.
That includes the most common form of asbestos, chrysotile, a serpentine mineral laced throughout the mountain (serpentine is California’s state rock). The reaction with carbon dioxide mainly produces magnesium carbonate minerals like magnesite, a stable material that could lock away the greenhouse gas for millennia.