Injecting carbon dioxide into underground rock deposits could some day permanently sequester vast quantities of the greenhouse gas, Drawdown reports. The summary lists the technique, known as enhanced weathering of minerals, among its Coming Attractions—climate solutions that were not ready for wide-scale use at the time of publication, but could have an impact by mid-century.
Late in 2016, two groups of researchers independently confirmed that carbon dioxide that had been dissolved in liquid and injected into underground volcanic rock deposits had rapidly become carbonate—part of the rock itself. The transformation from liquid to rock took just two years, a faster version of the natural process of weathering.
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“Natural rock weathering removes approximately one billion tons of atmospheric carbon dioxide annually,” Drawdown explains. “Various types of silicate rock on the surface of the Earth are weathered by carbon dioxide and dissolved in rainwater, which transforms the carbon dioxide into inorganic carbonates. These carbonates find their way into streams, rivers, and oceans, eventually becoming calcium carbonate. Enhanced weathering of minerals refers to technologies that hasten this process sustainably.”
Drawdown describes the potential impacts of advanced weathering of olivine, a green-hued silicate which could be mined, milled to a fine powder, and distributed over land and water to speed up the weathering reaction.
“Agricultural land in the tropics, where soils are warmer and wetter and have fewer minerals that would inhibit dissolution, are ideal,” the summary says. “If applied to one-third of tropical land, olivine could lower atmospheric carbon dioxide by 30 to 300 parts per million by 2100.”
Researchers told The Washington Post that, having successfully weathered smaller amounts of basalt rock, they planned to replicate the process on a scale that would come closer to sequestering industrial volumes of carbon dioxide.
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