Liming can help enhance carbon capture in agricultural fields

Adding crushed calcium carbonate — limestone — to agricultural fields can remove tons of carbon dioxide from the atmosphere each year while improving crop yields, a Yale-led study published in Nature Water found.

Greenhouse gases in the atmosphere hit a record high in 2024 reaching over 420 parts per million. The U.N. Intergovernmental Panel on Climate Change (IPCC) has identified carbon removal as one key tool in limiting warming to 1.5 C above pre-industrial levels to help mitigate climate change. To reach that target, 15 billion tons of carbon would have to be removed from the atmosphere each year.

“There is growing scientific consensus that removing carbon from the atmosphere is necessary to hit carbon goals. At this point, halting emissions won’t be enough,” Peter Raymond, the Oastler Professor of Biogeochemistry at the Yale School of the Environment and co-director of the Yale Center for Natural Carbon Capture (YCNCC), said.

Raymond worked with a team of scientists on a perspective of applying crushed calcium carbonate to farmlands, a natural carbon removal process. They found that limestone can support farm productivity while increasing carbon capture.

Calcium carbonate is commonly sourced from limestone formed by the fossilized remains of marine life. While it is often applied to farmland to feed growing plants and balance the effects of nitrogen fertilizers that lower soil pH, its potential for storing carbon also makes it a valuable tool in fighting climate change, Raymond said.

When bicarbonate formed from limestone's interaction with soils washes from fields into rivers and oceans, it has the potential to store carbon for millennia, he said.

Study coauthor Noah Planavsky, associate professor of earth and planetary science at Yale, and member of the scientific leadership team of YCNCC, said applying multiple tons of limestone per acre could potentially remove billions of tons of carbon dioxide before the end of the century. He added that limestone amendments could be used in conjunction with other soil amendments, including silicate rocks and organic amendments, to turn farmlands from being a major carbon source into being a carbon sink.

Agriculture is one of the largest greenhouse gas emitting sectors. Lime, which can react with nitrogen fertilizer and release carbon, has been listed as a carbon source by the IPCC. However, the researchers said that the acid from nitrogen fertilizer is the actual problem and, in most cases, adding enough limestone to improve soil levels will lead to CO2 removal over time.

Liming has additional benefits as well, the authors noted. Bicarbonate from agricultural liming that washes into oceans can raise ocean pH and support shell building.

“To me, ocean acidification is just as important of a problem as atmospheric CO₂ levels,” said Raymond. “Other carbon dioxide removal mechanisms don’t always address oceans, but liming does. But first and foremost, modifying liming practices is a way to drive carbon removals that helps farmers. It should be a priority.”