A groundbreaking study led by researchers from Yale University has revealed that the application of crushed calcium carbonate, commonly known as limestone, to agricultural fields presents a promising natural carbon removal strategy that can simultaneously enhance crop productivity. Published in the prestigious journal Nature Water, this research outlines how limestone amendments to soils not only improve agricultural output but also have the capacity to remove vast quantities of atmospheric carbon dioxide, offering an innovative avenue toward mitigating the accelerating climate crisis.
In 2024, atmospheric carbon dioxide levels surged to unprecedented heights, exceeding 420 parts per million, according to recent climate data. This alarming increase underscores the urgency for effective carbon sequestration methods to complement emission reductions. The United Nations Intergovernmental Panel on Climate Change (IPCC) has stressed that to limit global warming to 1.5 degrees Celsius above pre-industrial levels, approximately 15 billion tons of carbon need to be removed from the atmosphere annually—a monumental task demanding scalable and efficient carbon capture solutions.
Peter Raymond, Oastler Professor of Biogeochemistry at the Yale School of the Environment and co-director of the Yale Center for Natural Carbon Capture (YCNCC), emphasizes that halting greenhouse gas emissions alone will not suffice. Instead, active removal of carbon dioxide is essential to achieve climate goals. Alongside his team, Raymond advocates for enhancing soil liming practices as a dual-benefit strategy, which aligns agricultural productivity with long-term carbon storage in soil and aquatic systems.
Calcium carbonate naturally originates from limestone formed through the fossilization of marine organisms over millions of years. Traditionally, farmers apply limestone to agricultural soils to combat acidification caused by nitrogen fertilizers, which reduce soil pH and hamper plant growth. This soil amendment neutralizes excess acidity, thereby improving nutrient availability and crop yields. However, the Yale-led study finds that beyond these agronomic benefits, the interaction of calcium carbonate with soil chemistry holds significant promise for capturing and storing carbon dioxide on a global scale.
The mechanism at play involves the chemical transformation of calcium carbonate in soils, which produces bicarbonate ions that, upon washing into rivers and oceans, contribute to long-term carbon storage. These bicarbonate ions exhibit a remarkable residence time in aquatic systems, potentially locking away carbon for millennia. This pathway effectively shifts carbon from the atmosphere to stable reservoirs in the hydrosphere, presenting a form of carbon sequestration that addresses both terrestrial and marine carbon cycles.
Coauthor Noah Planavsky, an associate professor of earth and planetary science at Yale and a member of the YCNCC leadership, explains that applying multiple tons of finely crushed limestone per acre could scale to billions of tons of carbon dioxide removal by the century’s end. This scale of deployment could significantly complement other soil-based carbon removal strategies, such as the incorporation of silicate minerals and organic amendments, turning farmlands from net carbon emitters into vital carbon sinks.
Agriculture, long identified as a major greenhouse gas source, has complex interactions with soil carbon dynamics. While lime itself has traditionally been considered a net source of CO2 due to chemical reactions with nitrogen fertilizers, the researchers clarify that the true culprit is the acidity generated by fertilizers, not the liming process itself. When limestone is applied sufficiently to neutralize this acidity, it can lead to a net removal of carbon dioxide from the atmosphere over time, overturning misconceptions about the climate impacts of liming.
Beyond carbon capture, agricultural liming carries ancillary environmental benefits, including effects on ocean chemistry. The bicarbonate ions produced and transported to the oceans through runoff can help buffer ocean acidification, a pressing issue caused by elevated atmospheric CO2 levels. Ocean acidification threatens marine ecosystems, especially calcifying organisms such as shellfish and corals. By raising ocean pH, liming indirectly supports the health and resilience of these vital ecosystems.
Raymond stresses the significance of addressing ocean acidification alongside atmospheric carbon levels, emphasizing that carbon removal strategies should consider the coupled earth system. Unlike some carbon capture methods that focus narrowly on atmospheric CO2, liming integrates terrestrial and marine systems, thereby delivering a more holistic environmental benefit. This multifaceted impact makes modifying liming practices not only a climate imperative but also an ecological necessity.
The scalability and cost-effectiveness of limestone amendments are additional strengths that support their adoption. Limestone is abundant, widely accessible, and has been used safely in agriculture for centuries, providing a foundation for rapid and large-scale deployment. Implementing enhanced liming practices can therefore leverage existing agricultural infrastructure, minimizing barriers to entry and accelerating the transition toward climate-positive practices in farming communities worldwide.
However, the precision of liming applications must be refined to balance agronomic needs with carbon removal goals. Too little limestone will fail to neutralize soil acidity and inhibit carbon sequestration, while excessive application may have unintended consequences. Ongoing research is essential to optimize dosages and methodologies, integrate liming with complementary soil amendments, and monitor long-term impacts on soil health, crop productivity, and carbon persistence.
As the global demand for sustainable agricultural systems and robust climate solutions intensifies, this discovery positions liming as a powerful tool in the carbon removal toolkit. By reframing a common agronomic practice as a large-scale carbon sequestration strategy, the Yale-led study opens pathways for synergistic benefits: improving food security, enhancing farm resilience, and mitigating the climate crisis in tandem.
In conclusion, the increasing concentration of atmospheric CO2 demands transformative approaches to carbon removal. Utilizing crushed calcium carbonate in agriculture not only sustains and boosts farm productivity but also actively captures and stores carbon dioxide through natural geochemical processes. This innovative strategy, supported by rigorous scientific investigation, holds the potential to contribute significantly to global carbon removal targets, influencing climate policy and agricultural practices alike. The integration of liming into carbon management frameworks could mark a pivotal step toward a sustainable and climate-resilient future.
Subject of Research: Not applicable
Article Title: Using carbonates for carbon removal
News Publication Date: 6-Aug-2025
Web References: https://www.nature.com/articles/s44221-025-00473-0
References: IPCC reports, Yale Center for Natural Carbon Capture publications
Image Credits: Not specified
Keywords: Earth systems science
