Crushed Stone Being Spread Across Farms to Capture Carbon

Context: 

• A novel climate mitigation technique called Enhanced Rock Weathering (ERW) is gaining traction globally, including in Indian farms, by using crushed rocks to capture and store atmospheric carbon dioxide through accelerated natural processes.

Key Highlights: 

• Enhanced Rock Weathering (ERW) is a technique to accelerate natural geological weathering for carbon capture.
• Involves spreading finely ground quick-weathering rocks like basalt on farmlands.
• Weathering of rock by carbonic acid captures CO₂ and stores it as bicarbonate, eventually becoming limestone.
• Gaining global interest from carbon credit buyers – tech firms, airlines, and fast fashion companies.
• Carbon removal estimates vary widely; results depend on climate, rock type, and soil management.
• Also improves soil alkalinity, nutrient levels, and crop productivity.
• Scientists caution that carbon capture must be accurately measured, and risks like heavy metal contamination exist in some rocks.

Detailed Insights: 

• Naturally, rocks weather through reaction with carbonic acid, capturing CO₂ and converting it to stable forms.
• ERW speeds this up by using ground basalt, increasing surface area for reaction.
• A US study suggested that applying 50 tonnes of basalt per hectare annually could sequester up to 10.5 tonnes of CO₂ per hectare over four years.
• However, field trials in Malaysia and Australia have shown much lower sequestration rates, revealing previous overestimates.
• Factors influencing capture rates include temperature, rainfall, soil type, and granule size.
• Measuring success is complex; cation analysis (ions released during weathering) does not always correlate directly with CO₂ removal.
• Even when rocks react with stronger soil acids, they may prevent CO₂ release from acidification downstream in rivers and oceans.
• Besides climate mitigation, ERW enhances soil health, potentially boosting crop yields and soil formation.
• ERW is considered safe as it mimics natural processes, but caution is advised as some rocks may contain heavy metals.

Scientific/Technical Concepts Involved

• Weathering: Breakdown of rocks by natural agents; in ERW, driven by carbonic acid.
• Enhanced Rock Weathering (ERW): Artificially accelerating this process using finely crushed rocks.
• Basalt: A volcanic rock rich in magnesium and calcium, ideal for ERW due to its quick-weathering properties.
• Carbon Sequestration: The long-term storage of carbon to reduce its presence in the atmosphere.
• Soil Cation Measurement: A method to estimate carbon capture, though not always accurate.