The world faces two defining challenges of this century simultaneously: removing vast quantities of carbon dioxide from the atmosphere to limit global warming, and feeding a growing population without further degrading the soils and ecosystems on which agriculture depends. These challenges are usually treated as separate problems, requiring separate solutions. But there is one approach that addresses both at once — a technique rooted in geology, powered by the mining industry, and delivered through the hands of farmers. It is called Enhanced Rock Weathering.
Enhanced Rock Weathering (ERW) is emerging as one of the most promising carbon dioxide removal (CDR) technologies available today. It is scientifically grounded, practically scalable, and uniquely suited to tropical agricultural regions — making sub-Saharan Africa, and Uganda in particular, an ideal testing ground and eventual deployment zone. For a country whose economy is anchored in smallholder farming and whose geological resources are abundant and diverse, ERW represents a convergence of opportunity that few other nations can match.
This article explains what Enhanced Rock Weathering is, how it works, why it matters for climate change, and why Uganda stands at the front of this emerging field. We also discuss ALOM Mining & Geohydro Services' direct involvement in ERW project delivery and what it means for the intersection of mining and climate solutions in East Africa.
What Is Enhanced Rock Weathering?
Rock weathering is a natural process that has regulated Earth's climate for billions of years. When rain falls, it absorbs carbon dioxide from the atmosphere and forms a weak carbonic acid. This acidic rainwater reacts with silicate and carbite minerals in rocks at the Earth's surface, breaking them down in a chemical process called weathering. The carbon dioxide that was dissolved in the rainwater is converted into stable bicarbonate ions, which are carried by rivers to the ocean, where the carbon is locked away in marine sediments for geological timescales — effectively removing it from the atmosphere permanently.
This natural weathering cycle is one of the planet's most powerful long-term carbon sinks. Over millions of years, it has drawn down atmospheric CO2 concentrations from levels many times higher than today's. The problem is that natural weathering operates on geological time — far too slowly to counteract the rapid rise in atmospheric CO2 caused by burning fossil fuels over the past two centuries.
Enhanced Rock Weathering accelerates this natural process by crushing suitable rocks into fine particles and spreading them on agricultural land. The increased surface area of the crushed rock — exposed to warm, moist tropical soils teeming with microbial activity and plant root acids — dramatically speeds up the chemical weathering reactions. Carbon dioxide is drawn from the atmosphere and locked into stable mineral carbonates and dissolved bicarbonates at rates hundreds or thousands of times faster than would occur with unbroken rock on a hillside.
In short, ERW takes a natural geological process that already removes CO2 and supercharges it through the application of mining and agricultural techniques.
The Science: How ERW Removes Carbon Dioxide
The chemistry of Enhanced Rock Weathering can be described in simplified terms through the weathering of basalt, the most commonly used rock type for ERW applications.
Basalt is a dark, fine-grained volcanic rock rich in silicate minerals such as olivine, pyroxene, and plagioclase feldspar. These minerals contain calcium, magnesium, and iron — the key cations that participate in weathering reactions.
When crushed basalt is spread on agricultural soil, the following sequence occurs:
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Dissolution. Rainwater, soil moisture, and organic acids produced by plant roots and soil microbes attack the surface of the rock particles, dissolving the silicate minerals and releasing calcium (Ca2+), magnesium (Mg2+), and other cations into the soil solution.
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Carbon capture. As the minerals dissolve, they consume dissolved CO2 (as carbonic acid, H2CO3) in the reaction. The carbon from the CO2 is converted into dissolved bicarbonate ions (HCO3-), which are chemically stable in water.
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Transport and storage. The bicarbonate-rich soil water percolates through the soil profile and eventually reaches streams and rivers, which carry it to the ocean. In the ocean, the dissolved bicarbonate contributes to the marine carbonate system, where the carbon can remain sequestered for tens of thousands to hundreds of thousands of years. Some carbon may also precipitate as solid carbonate minerals (such as calcite) in the soil itself, providing even longer-term storage.
The net result is that atmospheric CO2 is converted into dissolved or solid carbonates through the accelerated chemical breakdown of rock. The process is thermodynamically favourable — it releases energy rather than consuming it — and the products are environmentally benign.
Scientific studies and field trials conducted across multiple countries have confirmed that ERW can sequester between 1 and 4 tonnes of CO2 per hectare per year in tropical soils, depending on rock type, particle size, application rate, soil conditions, temperature, and rainfall. Tropical regions with warm temperatures, high rainfall, acidic soils, and active soil biology offer the fastest weathering rates — which is precisely why equatorial Africa is so well suited to ERW deployment.
Agricultural Benefits: More Than Just Carbon Removal
One of the most compelling aspects of Enhanced Rock Weathering is that it delivers tangible agricultural benefits alongside carbon removal. For farmers, ERW is not an abstract climate intervention — it is a practical soil amendment that can improve crop yields and soil health.
Soil pH Correction
Many tropical soils, including those across Uganda, are naturally acidic due to intense weathering and leaching of base cations over geological time. Soil acidity limits the availability of essential plant nutrients, inhibits root growth, and creates toxic concentrations of aluminium. The weathering of basalt releases alkaline cations (calcium, magnesium, potassium) that raise soil pH, correcting acidity in a manner analogous to agricultural liming — but with the added benefit of carbon removal.
Nutrient Supply
Basalt contains a range of micronutrients — including phosphorus, potassium, calcium, magnesium, iron, manganese, and zinc — that are released slowly as the rock weathers. This slow-release nutrient supply complements conventional fertiliser application and can reduce the quantity of synthetic fertiliser required.
Improved Soil Structure
The calcium and magnesium released during weathering promote the formation of stable soil aggregates, improving soil structure, water retention, and root penetration. Over time, this can enhance the physical condition of degraded soils.
Reduced Aluminium Toxicity
By raising soil pH, ERW reduces the solubility of aluminium — a major constraint on crop growth in acidic tropical soils. Even a modest pH increase from 4.5 to 5.5 can dramatically reduce aluminium toxicity and improve nutrient uptake.
Potential Yield Increases
Field trials in tropical regions have reported crop yield improvements of 10 to 30 per cent when basalt dust is applied to acidic soils, though results vary depending on soil conditions, crop type, and application rates. For smallholder farmers in Uganda — who typically farm on degraded, nutrient-depleted soils with limited access to fertiliser — even modest yield improvements represent meaningful gains in food security and income.
The Opportunity for Uganda
Uganda is exceptionally well positioned to become a global leader in Enhanced Rock Weathering deployment. Several factors converge to create this opportunity.
Ideal Climate and Soils
Uganda's equatorial climate provides the warm temperatures, high rainfall, and active soil biology that maximise weathering rates. The country's predominantly acidic tropical soils — particularly the ferralsols and acrisols that cover large areas of central, eastern, and western Uganda — are precisely the soil types that benefit most from ERW application.
Abundant Rock Resources
Uganda has extensive deposits of basalt, particularly in the eastern and western rift zones and across the Karamoja sub-region. Other suitable rock types — including wollastonite-bearing marbles and ultramafic rocks — also occur in various parts of the country. The availability of suitable rock close to agricultural land reduces the cost of transport and makes ERW economically viable. For a comprehensive overview of Uganda's geological resources, see our guide to minerals found in Uganda.
Smallholder Agriculture Base
Over 70 per cent of Uganda's population depends on agriculture, and the vast majority of farms are smallholder operations of 2 hectares or less. These farmers cultivate some of the most degraded and nutrient-depleted soils in East Africa. ERW offers these farmers a dual benefit: improved soil fertility and crop yields in the short term, combined with carbon credit income that can provide a new revenue stream.
Carbon Market Access
The global voluntary carbon market is growing rapidly, driven by corporate net-zero commitments and increasing demand for high-quality carbon removal credits. ERW-generated carbon credits command premium prices because they represent genuine, measurable carbon removal (as opposed to emissions avoidance). Companies operating ERW programmes can generate and sell these credits, passing a portion of the revenue to participating farmers.
Mining Sector Synergy
The mining industry already possesses the core competencies required for ERW: rock extraction, crushing, grinding, transport, and distribution. For mining companies like ALOM, ERW represents an opportunity to apply existing skills and equipment to a new, climate-positive market. Waste rock from mining operations can in some cases be repurposed as ERW feedstock, converting a disposal liability into a climate solution.
ALOM's Role: Mining Meets Climate Action
ALOM Mining & Geohydro Services is actively engaged in the Enhanced Rock Weathering space through our work with Stack Carbon Limited, a company dedicated to deploying ERW projects in East Africa. This collaboration positions ALOM at the intersection of mining and climate solutions — a space we believe will become increasingly important as the world seeks scalable carbon dioxide removal technologies.
Our contribution to ERW projects draws on the full range of ALOM's mining services capabilities:
- Rock sourcing and characterisation. We identify and assess suitable rock deposits, conducting geological and geochemical analysis to determine their weathering potential and nutrient content.
- Quarrying and crushing. We extract and process rock to the particle size specifications required for ERW application — typically less than 100 micrometres for optimal weathering rates.
- Logistics and distribution. We manage the transport and delivery of crushed rock to farming communities, leveraging our operational presence across Uganda.
- Technical advisory. We provide geological expertise to support measurement, reporting, and verification (MRV) processes, helping to quantify the carbon removed and generate credible carbon credits.
This work represents a natural extension of ALOM's mining expertise into a new domain with significant social, environmental, and economic value. We see ERW not as a departure from our core business but as an evolution of it — applying the knowledge of rocks, minerals, and earth processes that defines our profession to one of the most pressing challenges of our time.
Challenges and Considerations
While the potential of ERW is substantial, several challenges must be addressed for successful large-scale deployment.
Measurement, Reporting, and Verification (MRV)
Quantifying the amount of CO2 removed by ERW in the field is more complex than in a laboratory. The weathering rate depends on soil conditions, rainfall, temperature, microbial activity, and the mineralogy and particle size of the applied rock. Robust MRV protocols — involving soil sampling, water chemistry analysis, isotopic tracing, and geochemical modelling — are essential for generating credible carbon credits. This remains an active area of scientific research and methodological development.
Logistics and Cost
Crushing rock to the fine particle sizes required for rapid weathering is energy-intensive. Transporting heavy rock material to dispersed smallholder farms over poor rural roads adds to the cost. The economics of ERW depend on carbon credit prices being sufficient to cover rock processing, transport, application, and MRV costs while leaving a margin for the farmer, the project developer, and the service providers.
Farmer Engagement
Successful ERW deployment requires the willing participation of thousands of smallholder farmers. Building trust, communicating the benefits, providing training on application methods, and ensuring fair revenue sharing from carbon credits are all essential for programme sustainability.
Environmental Safeguards
While ERW is generally considered environmentally benign, the application of large volumes of crushed rock to agricultural land warrants careful monitoring of potential impacts on soil biology, water quality, and local ecosystems. Responsible deployment includes baseline studies and ongoing environmental monitoring to ensure that the intervention does not create unintended harm. For more on environmental management in mining and related activities, see our article on environmental impact assessment in mining.
Scalability
Achieving climate-significant carbon removal through ERW will require deployment across millions of hectares — a massive logistical undertaking. Scaling from pilot projects to continental-level deployment will require investment in crushing and distribution infrastructure, farmer networks, and MRV systems at a level that has not yet been achieved.
The Bigger Picture: Mining's Role in Climate Solutions
Enhanced Rock Weathering challenges the common perception that the mining industry is solely a contributor to environmental problems. In reality, the mining sector possesses unique capabilities — geological knowledge, rock processing expertise, heavy logistics management, and large-scale operational capacity — that are essential for delivering several leading carbon dioxide removal technologies.
Beyond ERW, the mining industry is central to supplying the critical minerals required for the energy transition: lithium and cobalt for batteries, copper for electrification, rare earth elements for wind turbines and electric motors, and graphite for battery anodes. Mining is not the enemy of the climate agenda — it is an indispensable enabler of it.
For Uganda, a country endowed with both the geological resources for ERW and the critical minerals demanded by the global energy transition, the alignment of mining with climate action represents a double opportunity: one that can generate revenue, create employment, improve agricultural productivity, and contribute to global carbon dioxide removal simultaneously.
Conclusion
Enhanced Rock Weathering is a carbon dioxide removal technology that is rooted in natural geological processes, scientifically validated, agriculturally beneficial, and ideally suited to tropical nations like Uganda. It offers a rare convergence of climate, agricultural, and economic benefits — removing CO2 from the atmosphere while improving soil fertility, boosting crop yields, and generating carbon credit revenue for smallholder farmers.
For the mining industry, ERW opens a new and meaningful avenue of contribution to the global climate response. The skills, knowledge, and operational capacity that define mining — understanding rocks, processing minerals, managing logistics at scale — are precisely what ERW deployment requires.
ALOM Mining & Geohydro Services is proud to be actively involved in this emerging field, bringing our geological and mining expertise to bear on one of the defining challenges of our generation. As ERW scales from pilot projects to widespread deployment across East Africa, we are committed to playing a leading role in delivering this technology responsibly, effectively, and at the scale the climate crisis demands.
If you are interested in ERW project development, carbon credit generation, or the intersection of mining and climate solutions in East Africa, contact ALOM Mining & Geohydro Services to learn more about our work and capabilities.