Farmers in US heartland store carbon with limestone
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Farmers in the Mississippi River Basin, which covers 41% of the lower 48 United States, are storing more carbon dioxide in their soil than they release when they apply limestone to their fields.
For generations, these farmers have used liming to raise soil pH, reduce acidity, and improve crop yields. A new Yale-led study examined over a century of data and determined that this practice results in a net removal of carbon dioxide from the atmosphere.
Researchers accounted for the carbon dioxide released through natural soil processes and found that liming still removes carbon when compared to those conditions. The process works by reacting crushed limestone with carbon dioxide in the soil, forming stable bicarbonate ions that eventually reach the ocean and remain stored for extended periods. This is similar to “enhanced weathering,” a climate change mitigation strategy that has focused more on silicate rocks.
The study challenges current greenhouse gas accounting practices, including those used by the Intergovernmental Panel on Climate Change (IPCC), which currently counts the carbon in applied lime as an emission. Scientists suggest recognizing liming as a carbon removal method could better support both farmers and climate goals. They also note that the effectiveness of liming varies depending on local conditions like soil acidity and hydrology, and that many farmers currently cannot afford optimal soil pH management.
