Enhanced rock weathering: can crushed stone become a climate solution?
Published on 29 September 2026 at 04:29 GMT
By Editorial Team SDG13
Spreading crushed stone across farmland is becoming an experiment in climate mitigation as well as soil management. Enhanced rock weathering accelerates chemical reactions that can transfer carbon dioxide from the atmosphere into dissolved forms. Field trials have recorded agricultural benefits, while modelling suggests substantial removal potential. The unresolved question is how much carbon reaches durable storage, how quickly, and at what environmental cost.
Accelerating a geological process
Silicate minerals naturally react with water and carbon dioxide as they weather. Crushing rocks such as basalt exposes more surface area; spreading the particles through agricultural soils brings them into contact with moisture, roots and microbes. Carbon dioxide dissolved in water forms carbonic acid, which helps dissolve minerals and can produce bicarbonate, a dissolved form of inorganic carbon.
Water can carry these reaction products through soils and rivers towards the ocean. The proposed storage pathway therefore extends far beyond the field where a spreader deposits the powder. Long-lived ocean storage is possible, but counting carbon at the point of mineral dissolution does not establish how much eventually remains stored.
Temperature, rainfall, mineral composition and soil conditions influence reaction rates. A treatment successful on one farm cannot automatically be assigned the same carbon-removal rate elsewhere. Nor does all the rock react during the season in which it is spread: dissolution and transport unfold over different timescales.
What the field evidence shows
A four-year maize–soybean experiment in Illinois, conducted from 2016 to 2020 and published in 2024, provides evidence beyond laboratory tests. David Beerling of the University of Sheffield and colleagues studied annual basalt applications of 50 tonnes per hectare. They reported yield increases relative to untreated controls of 12% for maize in 2020 and 16% for soybean in 2019, alongside improved fertility and reduced soil acidification.
From losses of calcium and magnesium in the rock, the team estimated cumulative carbon dioxide removal potential of 10.5 ± 3.8 tonnes per hectare over four years. This was potential inferred from weathering, rather than a direct measurement of an identical quantity permanently stored in the ocean. It followed repeated applications totalling 200 tonnes of rock per hectare.
The experiment found no significant increase in trace metals in harvested grain or the measured exchangeable soil pools relative to controls. These findings describe the material and conditions tested, not a guarantee covering every quarry, crop or repeated application programme.
Soil benefits and environmental exposure
Rock amendments can supply nutrients and counter soil acidity, potentially giving farmers a reason to use them beyond carbon income. Basalt is not a uniform product, however. Its chemistry varies, and soil responses also depend on existing fertility and management.
A 2024 environmental assessment by Charlotte R. Levy and colleagues describes risks including potentially harmful trace elements, airborne dust and changes to soil and water systems. Some ultramafic rocks contain higher concentrations of nickel and chromium than basalt. The amount present, its chemical form and its availability to organisms all affect exposure.
Fine particles can move into waterways or become airborne during handling. Changes in soil pH and nutrient availability can affect biological processes as well as crops. Levy and colleagues identify feedstock composition and local environmental conditions as factors in assessing these effects.
The material scale behind the models
A 2025 US modelling study led by Beerling estimated potential net removal of 160–300 million tonnes of carbon dioxide annually by 2050. Its scenarios increased basalt extraction towards one or two billion tonnes per year by 2070. These are conditional projections, not measured national removals or an announced delivery programme.
The study accounted for emissions from quarrying, grinding, transport and spreading. Each operation consumes energy, and the distance between rock supplies and cropland affects both costs and the carbon balance. Finer grinding exposes reactive surfaces but adds processing demand. Expanding deployment therefore involves an industrial supply chain alongside agricultural equipment.
Existing residues could supply some material, but their suitability depends on their composition. In a February 2026 perspective, Marcus Schiedung and colleagues concluded that dedicated mining appeared unavoidable for large-scale deployment. Their assessment also identified unresolved financing and risk-allocation questions.
Measuring removal beyond the field
A 2024 measurement review by Matthew O. Clarkson and colleagues explains the limitations of different ways to quantify carbon removal. Soil sampling can show mineral depletion; water sampling can reveal dissolved products. Both encounter spatial variation, background weathering and uncertainty about water movement.
Acids other than carbonic acid can also dissolve rock, so mineral loss alone does not translate directly into atmospheric carbon removal. Some weathering products remain in soils or enter plants. Downstream reactions, including carbonate formation and carbon dioxide release, can reduce eventual storage. Establishing additional removal also involves comparison with what would have happened without treatment.
The 2026 perspective similarly describes the fate of weathering products in rivers as poorly constrained. This leaves a gap between estimating reactions on farmland and verifying their eventual climate effect. Assessing durable removal involves tracing the products of weathering and accounting for losses along the route to storage.
The connection to SDG 13 (Climate Action) lies in the possibility of withdrawing atmospheric carbon. Crop responses and durable carbon removal are distinct outcomes. The studies identify uncertainties in how results vary across soils, supply chains and river systems, limiting estimates of enhanced weathering’s eventual climate contribution.
Written by a human author, edited with AI assistance.
Further information:
• Beerling et al., 2024, Proceedings of the National Academy of Sciences: the field experiment supports the application rates, crop responses and estimated removal potential.
• Levy et al., 2024, Environmental Science & Technology: this assessment examines feedstock chemistry and potential environmental effects.
• Beerling et al., 2025, Nature: the US modelling study supports the projected removal range and industrial supply requirements.
• Clarkson et al., 2024, Frontiers in Climate: this review explains measurement methods and complications in translating weathering into removal.
• Schiedung et al., 2026, Nature Reviews Earth & Environment: this perspective evaluates uncertainties in feedstocks, environmental responses and durable removal.
