New research led by Yale University challenges long-held assumptions about agricultural emissions, suggesting that adding lime to soil may actually remove carbon dioxide (CO2) from the atmosphere rather than release it.
The findings, presented at the Goldschmidt Conference in Prague, draw on over a century of data from the Mississippi River basin and advanced modeling techniques.
Contrary to international guidelines, which treat all lime-related carbon as an emission, the study found that soil acidity from fertilizers and pollution — not lime — is the primary driver of CO2 release.
“It is the reaction of acidity with the carbonate that creates CO2 emissions, not the addition of the lime itself,” lead author Dr. Tim Jesper Suhrhoff from Yale’s Centre for Natural Carbon Capture was quoted as saying.
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When lime is applied to agricultural soil, it reacts with carbonic acid to form bicarbonate, which can stabilize carbon in the environment.
However, if strong acids like nitric or sulfuric acid are present — commonly introduced through fertilizers and air pollution — these can trigger reactions that release CO2.
Since the 1930s, increased liming has improved soil quality and crop yields while also aiding in CO2 removal. Researchers estimate current removal rates are at about 75% of the theoretical maximum.
The study calls for policy changes to reflect these insights and underscores the potential for revised agricultural practices to play a larger role in carbon capture.
“By penalizing liming, rather than the addition of acids, we are targeting the wrong driver and potentially losing the other benefits that liming can bring,” Suhrhoff noted, arguing for a shift in emissions policy to better support both climate and food security.
The researchers recommend addressing soil acidity with silicate rock before liming to maximize carbon benefits and minimize emissions.
The abstract of the paper, titled “Acidity addition in the Mississippi watershed drives agricultural CO2 emissions” is available here.
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