Carbon sequestration through rock weathering (also called enhanced weathering) is a natural and engineered process that accelerates the breakdown of silicate and carbonate minerals to capture atmospheric CO₂. This method not only helps mitigate climate change but also improves soil fertility, promoting better plant growth and CO₂ uptake.
How Rock Weathering Sequesters CO₂
1. Natural Weathering Process
When silicate or carbonate rocks (e.g., basalt, olivine, limestone) are exposed to water and CO₂, they undergo chemical reactions that dissolve minerals and trap carbon. The general reaction for silicate weathering is:
CaSiO₃ (wollastonite) + 2CO₂ + H₂O → Ca²⁺ + 2HCO₃⁻ + SiO₂
The resulting bicarbonate ions (HCO₃⁻) are washed into oceans, where they store carbon for thousands of years.
2. Enhanced Weathering (Human-Accelerated Process)
To speed up natural weathering, scientists and farmers crush rocks into fine powder and spread them on agricultural fields. This increases the surface area, allowing faster CO₂ absorption.
Key Factors Influencing Weathering Rate:
- Rock type (basalt and olivine are highly reactive).
- Particle size (finer grains weather faster).
- Climate conditions (warm, wet environments enhance reactions).
- Soil microbes (bacteria and fungi accelerate mineral breakdown).
Application of Rock Weathering in Soil for Better CO₂ Uptake by Plants
1. Improving Soil Fertility & Plant Growth
When silicate rocks (like basalt) weather, they release essential nutrients such as:
- Calcium (Ca), Magnesium (Mg), Potassium (K), and Phosphorus (P)—critical for plant health.
- Silica (Si)—strengthens plant cell walls, improving resistance to pests and drought.
These nutrients enhance photosynthesis, leading to higher biomass production and increased CO₂ absorption by crops.
2. Balancing Soil pH
Many agricultural soils suffer from acidification due to excessive fertilizer use. Weathering of alkaline rocks (e.g., limestone) neutralizes acidic soils, creating a better environment for microbial activity and root growth.
3. Strengthening the Soil Carbon Pump
- Plants absorb more CO₂ due to improved nutrient availability.
- Organic matter from plant residues increases soil organic carbon (SOC).
- Microbial activity is boosted, further stabilizing carbon in the soil.
Real-World Applications & Benefits
1. Agricultural Use (Farming & Forestry)
- Basalt dust application in croplands (e.g., wheat, corn, soybeans) enhances yields while sequestering CO₂.
- Reforestation projects use rock powders to accelerate tree growth and carbon storage.
2. Large-Scale Carbon Removal Projects
- Companies like Project Vesta test coastal enhanced weathering by spreading olivine sand on beaches to capture CO₂ via wave action.
- Biochar-rock dust mixtures are being tested for long-term carbon storage in soils.
3. Economic & Environmental Benefits
- Low-cost compared to high-tech carbon capture methods.
- Reduces dependency on synthetic fertilizers, cutting greenhouse gas emissions from agriculture.
- Improves water retention in soils, making farms more resilient to climate change.
India, with its vast agricultural lands and growing climate challenges, can benefit from enhanced rock weathering (ERW)—a natural process accelerated to capture CO₂. By grinding silicate rocks like basalt and applying them to soil, ERW not only sequesters carbon but also enhances soil fertility, boosting crop yields. This method aligns with India’s climate goals and sustainable farming practices. However, challenges like energy-intensive grinding and large-scale implementation need addressing for effective adoption.
