It's one of the latest technologies for sequestering carbon: Crush silicate rocks, add to crop soil, and let the rock dust naturally react with carbon dioxide. The reactions bind carbon into stable mineral forms that can persist for millennia, while also enriching the soil with nutrients, boosting crop yields and increasing farmer profits.
But this process, called enhanced rock weathering, needs to be widely adopted to move the needle on global warming and deliver real benefits to farmers.
In a new study, published Feb. 16 in Communications Sustainability, researchers model various trajectories for the global adoption of enhanced rock weathering, finding that the method could remove up to about a gigaton of carbon from the atmosphere annually by 2100, roughly equivalent to the yearly emissions of a major industrial economy. But to reach that mark, access and adoption by the Global South, where warmer and wetter conditions facilitate rock weathering, will be essential.
"If this were to be scaled, the Global South would eventually contribute more, and tech transfer and global carbon markets could accelerate adoption in these regions while also making adoption more equitable," said senior author Chuan Liao, assistant professor in the Ashley School of Global Development and the Environment, part of the College of Agriculture and Life Sciences (CALS). "Previous research assumed a uniform adoption across regions. Our major contribution in this study is to model these trajectories in a more realistic way."
Unlike earlier studies, the new model captures staggered adoption, regional lags and social tipping points that might speed adoption of mitigation technologies.
While still an emerging technology, enhanced rock weathering has attracted interest from researchers and the private sector; Microsoft and Stripe, for example, have invested millions to include the practice in their portfolios for carbon removal. The method is particularly tantalizing because of its potential co-benefits for farmers. The process adds calcium, magnesium and iron to soils, which could reduce the need for synthetic fertilizers and make soils less acidic.
"We need to sharpen scientific predictions of enhanced rock weathering, because it has amazing potential to drive carbon profits directly into farmers' pocketbooks," said Benjamin Z. Houlton, the Ronald P. Lynch Dean of CALS and a co-author, who has conducted extensive field studies and farmer outreach around the practice.
In designing the models, the researchers, including co-first authors and postdoctoral researchers Ying Tu and Radine Rafols, used historical trends in the adoption of other agricultural technologies, like the use of fertilizers and irrigation, across different countries and regions. The resulting models reflect a staggered trajectory, with early and late adopters, and project estimates for both modest and aggressive adoption.
Depending on the approach, the process could remove 0.35 to 0.76 gigatons of carbon by 2050 and 0.7 to 1.1 gigatons by 2100. The researchers found that high-income countries will initially lead in uptake, but countries in the Global South, such as India and Brazil, will overtake them by 2050.
Liao said that expanding access to the Global South would not only improve the potential for carbon removal but also promote an equitable distribution of benefits.
"It means carbon credits could be directed to those countries, to small-farm owners, which could help raise their income and support crop yields," Liao said.
The researchers also modeled a scenario in which global warming reaches a tipping point - which then motivates countries to speed up climate mitigation measures.
"Faster global warming is likely to increase pressure on policymakers and farmers to adopt this technology in a more aggressive way," Liao said. "Enhanced rock weathering provides one solution in a whole portfolio of carbon mitigation strategies that will need to be adopted to achieve our goals."
Liao said that understanding the path forward requires rigorous empirical research acknowledging the social dynamics that impact adoption. "Climate change is not just an environmental problem, it's also a social science problem," he said. "This paper is an example of social scientists and natural scientists working together to produce something hopefully impactful."
Co-authors of the study include Veerabhadran Ramanathan, professor at the University of California, San Diego and adjunct professor of global development in CALS; doctoral student Natalia Butler; former research associate and senior lecturer Linah Ababneh; and former postdoctoral researcher Feng Tao.
Funding for the study came from the Cornell Center for Social Sciences.
