New research suggests agricultural liming is a significant carbon sink rather than a CO₂ source

Applying lime to farmland soils in the United States could serve as a significant carbon dioxide (CO₂) sink rather than a source of emissions, according to new research presented at the Goldschmidt Conference in Prague. The findings, based on over a century of data from the Mississippi River basin and advanced modeling, suggest that international climate guidelines may be overlooking the climate mitigation potential of liming practices.

Researchers from the Yale Center for Natural Carbon Capture argue that CO₂ emissions from soils are primarily driven by acid additions—resulting from atmospheric pollution and nitrogen fertilizer use—rather than the application of lime itself. The study challenges the Intergovernmental Panel on Climate Change (IPCC) approach, which assumes that all carbon in agricultural lime is released as CO₂ upon application.

“It is the reaction of acidity with carbonate that creates CO₂ emissions, not the addition of the lime itself,” said lead author Dr. Tim Jesper Suhrhoff. “In the absence of strong acids, liming actually removes CO₂ from the atmosphere through the formation of bicarbonate.”

The researchers contend that current greenhouse gas inventories penalize liming while ignoring acid inputs, such as from industrial pollution or fertilizer. Their analysis indicates that this misattribution could underestimate the climate benefit of liming, particularly in acidified soils.

Data from the Mississippi River, collected since 1900, reveals a long-term trend of increasing soil acidity due to fossil fuel emissions and fertilizer use, which has not been fully offset by lime application. However, since the 1930s, expanded use of lime has improved the rate and efficiency of CO₂ removal. According to the study, current removal is estimated at 75% of the theoretical maximum rate.

The researchers call for a reassessment of international and national emissions accounting, with a shift in focus from liming to acid inputs. They also suggest that combining silicate rock application to neutralize acidity before liming may enhance carbon removal while maintaining agronomic benefits such as improved yields and reduced nitrous oxide emissions.

Dr. Suhrhoff concluded, “Liming has long been essential for crop productivity and food security. We now show it also has climate benefits over decadal timescales. Policy frameworks should reflect this dual role.”