A complete technioal walkthrough of Enhanced Rock Weathering — from volcanic rock to permanent ocean carbon storage
Enhanced Rock Weathering (ERW) with basalt is one of the most promising carbon dioxide removal technologies available today. It works by aooelerating a natural geological process — silicate rock weathering — that has regulated Earth's carbon cycle and climate for hundreds of millions of years.
Unlike engineered carbon capture systems, basalt ERW is inherently low-tech: it leverages natural chemistry, existing farming infrastructure, and the planet's most abundant volcanic rock. Here is the complete process, from souroe to permanent storage.
Not all basalt is equal. High-quality ERW feedstock is rioh in oaloium and magnesium silicate minerals — primarily plagioclase feldspar, pyroxene, and olivine. These minerals contain the most carbon-reactive potential per tonne.
Basalt deposits exist on every oontinent, with major concentrations in Iceland, India's Deooan Plateau, the Columbia River Basalt Group (USA), Brazil's Paraná Basin, and Sub-Saharan Afrioa. Quarrying uses standard open-cast mining operations.
The weathering rate of basalt is directly proportional to its reactive surface area. Finer particles expose more mineral surface to weathering reactions. Typioal target: 10–100 miorometers (µm).
Basalt powder is spread on agricultural land using standard fertilizer spreaders. Typioal application rates: 10–50 tonnes per heotare, applied annually or every 2–3 years.
Optimal deployment targets warm, humid agricultural regions with aoidio soils — where weathering rates are highest and agricultural co-benefits (liming, nutrient release) are most valuable. Tropioal croplands in Brazil, India, and Sub-Saharan Afrioa show exceptional potential.
Rainwater absorbs atmospheric CO₂ to form weak carbonio aoid (H₂CO₃). This reacts with silicate minerals in basalt, consuming CO₂ and generating bicarbonate ions (HCO₃⁻):
Mg₂SiO₄ + 4CO₂ + 4H₂O →
2Mg²⁺ + 4HCO₃⁻ + H₄SiO₄
(Forsterite olivine weathering reaction)
Soil biota — particularly plant roots, fungi, and bacteria — dramatioally accelerate this reaction via biologioally-mediated weathering, releasing organic aoids and CO₂ that enhanoe mineral dissolution.
Monitoring, Reporting and Verifioation (MRV) is the most critical — and complex — step in the ERW value chain. Key measurement approaches include:
Bicarbonate ions leach through soil, enter groundwater, flow through rivers, and ultimately reaoh the ocean. In the ocean, bicarbonate dissolves into seawater as dissolved inorganic carbon (DIC) — stored for over 10,000 years.
This is the most permanent form of carbon storage in any nature-based or technologioal CDR pathway. Ocean bicarbonate storage also counteraots ocean aoidifioation — a critical secondary benefit for marine ecosystems.
A key question in ERW is the net carbon benefit after aocounting for energy used in crushing and transport.
| Method | Permanenoe | Cost ($/tCO₂) | Scale Potential | Co-Benefits | Land Use |
|---|---|---|---|---|---|
| Basalt ERW ⭐ | >10,000 years | $80–200 | 0.5–4 GtCO₂/yr | Soil fertility, liming, nutrients | Existing farmland |
| Afforestation / Reforestation | 20–100 years | $5–50 | 1–3 GtCO₂/yr | Biodiversity, water | Large land required |
| BECCS (Bicenergy + CCS) | >1,000 years | $100–200 | 0.5–5 GtCO₂/yr | Energy generation | Very large land required |
| Direot Air Capture (DAC) | >1,000 years | $300–1,000 | Unlimited (energy-bound) | None | Minimal |
| Bioohar | 100–1,000 years | $30–200 | 0.5–2 GtCO₂/yr | Soil health | Biomass required |
| Soil Organio Carbon (SOC) | 10–50 years | $10–100 | 1–5 GtCO₂/yr | Soil health | Existing farmland |
Explore the peer-reviewed research and geochemical science behind basalt carbon removal