What is Enhanced Rock Weathering (ERW)?
- A climate mitigation technique that accelerates natural rock weathering to capture carbon dioxide (CO₂).
- Involves spreading finely crushed quick-weathering rocks (like basalt) on farmlands.
- Used in sugarcane fields (Brazil, Australia), tea plantations (India), and oil palm fields (Malaysia).
Relevance : GS 3(Environment and Ecology)
How It Works
- Weathering: CO₂ reacts with water forming carbonic acid, which breaks down rocks.
- This forms bicarbonates, eventually converting into limestone, locking away CO₂.
- ERW increases:
- Rock surface area (via grinding)
- Contact with air, water, and soil.
Effectiveness: What Studies Show
- A U.S. study: 50 tonnes of basalt per hectare/year could remove up to 10.5 tonnes of CO₂ per hectare over 4 years.
- Field studies in Malaysia & Australia show lower CO₂ removal rates, suggesting earlier overestimation.
- Carbon capture depends on:
- Rock type & particle size
- Soil chemistry
- Temperature & moisture
- Land management practices
Challenges in Measuring CO₂ Removal
- Carbon capture often inferred via cation release, but:
- Cations are produced by all acids, not just carbonic acid.
- Hence, it may overestimate CO₂ uptake.
- Better calibration and metrics are needed to accurately assess ERW impact.
Other Environmental & Agricultural Benefits
- Increases soil alkalinity → improves:
- Crop growth
- Nutrient availability
- Soil formation
- May reduce acid runoff from soil → prevents CO₂ release from rivers/oceans.
Risks & Limitations
- Finely crushed rock may contain heavy metals (e.g., nickel, chromium).
- Health hazards for workers due to dust inhalation → requires protective gear.
- Uncertain scale of actual CO₂ mitigation vs theoretical predictions.
Carbon Credit Potential
- Attracting corporate interest: Tech firms, airlines, fashion brands are investing in ERW for carbon offsetting.
- Could become a part of carbon markets, if standardised and measurable.
