Crushed Basalt on China’s Farmland Could Lock Away Billions of Tonnes of CO2

Spreading crushed volcanic rock across the world’s largest stretch of farmland could become one of China’s most practical weapons against climate change, according to a new spatially explicit assessment published in Communications Earth & Environment. The study, led by Zeyu Wang of Tsinghua University’s Institute of Energy, Environment and Economy, together with Fei Teng of Tsinghua and David M. Reiner of the University of Cambridge, provides the first national-scale, grid-by-grid estimate of how much carbon dioxide enhanced rock weathering could remove from the atmosphere in China, and what it would cost to do so. The answer is striking: a single year of basalt application on the country’s croplands could, under the study’s range of assumptions, remove between 0.44 and 0.79 billion tonnes of CO2 by the year 2100, at a net life-cycle-adjusted cost of 127 to 226 US dollars per tonne of CO2 removed.

Enhanced rock weathering is not a new idea in principle; it is an acceleration of one of Earth’s oldest climate-regulating processes. Over geological time, rain and soil moisture react with silicate rocks in a chain of chemical reactions that pulls carbon dioxide out of the air and converts it into dissolved inorganic carbon, ultimately carried by rivers to the oceans and stored there. The natural process is far too slow to matter on human timescales, but grinding rock into fine powder dramatically increases the reactive surface area exposed to water and air. When that powder is scattered on agricultural fields, soil moisture, plant roots and soil acids attack the mineral grains, releasing cations such as calcium and magnesium that combine with dissolved CO2 to form bicarbonates. In effect, the field becomes a vast, passive chemical scrubber, and the farmer’s existing machinery and irrigation infrastructure do much of the work.

What has been missing, the authors argue, is a credible national-scale quantification for China, the country whose carbon-neutrality pledge by 2060 arguably depends more than any other on finding affordable negative-emissions options at enormous scale. Most carbon dioxide removal technologies face well-known constraints: direct air capture remains expensive and energy-intensive, afforestation competes for land and stores carbon in vulnerable biomass, and bioenergy with carbon capture requires both large biomass supplies and reliable geological storage. Enhanced rock weathering sidesteps some of these bottlenecks because it piggybacks on agriculture, uses abundant silicate rocks such as basalt, and in many cases delivers co-benefits to soils, including the release of plant nutrients and the potential to ameliorate soil acidity.

The Tsinghua-Cambridge team addressed the gap with a spatially explicit analysis across China’s croplands, meaning that rather than averaging the country into a single number, they resolved the relevant variables location by location. That matters because the effectiveness of enhanced rock weathering is exquisitely sensitive to geography. Weathering rates depend on climate, with warm, wet conditions accelerating the dissolution of silicate minerals, and on soil chemistry, which controls how quickly acids in the soil can attack the rock. They also depend on logistics: basalt must be crushed, transported and spread, and the energy and emissions embedded in that supply chain eat directly into the net climate benefit. A field in humid South China served by a nearby quarry is a very different proposition from a dry northern plain hundreds of kilometres from suitable rock.

By accounting for these factors across the national cropland base, the study arrives at its headline range of 0.44 to 0.79 billion tonnes of CO2 removed by 2100 from a single year of application. To put that in perspective, the upper end of the range is comparable to a substantial fraction of China’s annual emissions from a single year of rock, spread once and continuing to weather for decades as the grains dissolve. The cost estimate of 127 to 226 dollars per tonne of CO2 removed is a net, life-cycle-adjusted figure, meaning the authors subtracted the emissions and costs of grinding, transporting and spreading the rock before tallying the balance. That places enhanced rock weathering in a competitive band relative to many other carbon removal pathways, though still well above the levels needed for mass deployment without policy support.

One of the study’s most consequential technical findings concerns particle size. The researchers found that particles finer than those typically used commercially provide the most favorable balance between removal potential and cost. The logic follows directly from reaction kinetics: the rate at which a mineral grain dissolves scales with its exposed surface area, and grinding rock finer multiplies that area. Finer milling costs more energy up front, but the additional carbon removed over the decades that follow more than compensates in the study’s accounting. This is a practical insight for anyone hoping to design a real deployment program, because it suggests the industry should invest in finer grinding than current agricultural lime or rock-dust practice would suggest, and it gives quarry operators and equipment manufacturers a concrete engineering target.

The analysis also looked beyond a one-off application. Under multi-year application, repeated spreading across successive seasons, the authors estimate that enhanced rock weathering could contribute 5 to 30 percent of China’s negative emissions needs by 2060. That range is wide, reflecting genuine uncertainties in weathering kinetics, application rates and future costs, but even the low end represents a meaningful slice of the enormous carbon-removal burden implied by carbon neutrality. The study identifies priority areas in Northeast, Central-South and East China, regions where the combination of climate, soils, cropland extent and proximity to basalt resources makes the approach most favorable. Such spatial prioritization is exactly what policymakers need to move from a promising concept to a targeted pilot program.

The authors are careful to frame their work as an initial spatially resolved assessment rather than a final verdict, and they are explicit about what must happen next. They call for field trials and coupled soil-river geochemical modeling to constrain three critical unknowns: the actual rate of weathering under real field conditions, the fraction of the dissolved carbon that is retained as it travels downstream rather than being re-released, and the magnitude of losses along the pathway from field to ocean. These are not minor caveats. The carbon captured on a farm exists as dissolved bicarbonate in soil water, and its ultimate fate depends on hydrology and river chemistry at scales far beyond any single plot. Without that downstream accounting, removal estimates could be systematically optimistic or pessimistic.

For China’s climate planners, the study supports considering enhanced rock weathering in the national carbon-management portfolio, a conclusion with global resonance. The same modeling framework could be applied to other major agricultural economies, from India and Brazil to the United States, where basaltic rocks and extensive croplands coexist. The work was supported by the National Key R&D Program of China, and its open-access publication means the underlying assessment is available to researchers and policymakers worldwide. If field trials bear out the model’s assumptions, the vision that emerges is quietly revolutionary: a carbon removal technology that requires no exotic chemistry, no vast new industrial infrastructure, and no land taken out of food production, only rock, crushers, spreaders and the patient chemistry of water meeting stone. In a world desperately searching for affordable ways to draw carbon down, the answer may lie in the oldest scrubber of all, the weathering of rock, accelerated by human ingenuity and deployed across the fields that already feed a fifth of humanity.

Subject of Research: National-scale assessment of enhanced rock weathering as a carbon dioxide removal strategy on China's croplands

Article Title: Assessing the potential and cost of enhanced rock weathering in China

Article References: Assessing the potential and cost of enhanced rock weathering in China. (n.d.). https://doi.org/10.1038/s43247-026-04136-0

Image Credits: AI Generated

DOI: 10.1038/s43247-026-04136-0

Keywords: enhanced rock weathering, carbon dioxide removal, China, basalt, croplands, carbon neutrality, negative emissions, soil chemistry, climate mitigation, carbon costs, geochemical modeling, Tsinghua University