As climate urgency grows, Enhanced Rock Weathering (ERW) is gaining global interest for its potential to combine carbon capture with agricultural benefits.

About Enhanced Rock Weathering (ERW)

• Enhanced Rock Weathering (ERW) is a carbon dioxide removal technique that accelerates the natural process of rock weathering to capture and store atmospheric CO₂
• ERW seeks to accelerate this natural weathering process using finely ground silicate rocks such as basalt. 

How Does It Work?

• Rock Application: Finely crushed silicate rocks are spread on land, typically agricultural fields.
• Chemical Reaction: Rainfall and soil moisture facilitate reactions where CO₂ dissolves in water to form carbonic acid, which reacts with minerals like calcium or magnesium in the rocks to form carbonates.
• Carbon Storage: The resulting carbonates are stable and can either remain in the soil or wash into rivers and oceans, where they contribute to long-term carbon storage.
• Co-Benefits: ERW can improve soil fertility by adding nutrients like calcium, magnesium, and potassium, potentially increasing crop yields. It may also reduce soil acidity.

Benefits

• Carbon Removal: ERW offers a scalable method to remove atmospheric CO₂ and lock it away for thousands of years.
  • One US study: Up to 10.5 tonnes CO₂ removed per hectare over 4 years (with 50 tonnes of basalt/year)
• Soil Improvement: Increased alkalinity from basalt can enhance soil fertility, nutrient availability, and crop yields.
• Acid Neutralisation: Even when not directly reacting with CO₂, ERW may prevent soil acids from entering waterways and releasing CO₂ downstream. 
• Cost-Effective Material: Basalt is abundant and often a byproduct of quarrying, making it a low-cost input.

Challenges

• Overestimation Impact : Accurately measuring captured CO₂ is challenging:
  • Current method: Tracks cations released during weathering
  • But cations also result from non-CO₂ acids, leading to possible overestimation
• Occupational Safety: Spreading fine rock dust requires protective equipment for farm workers.
• Toxic Elements: Some silicate rocks may contain heavy metals; proper selection and handling are essential.
• Carbon Credit Integrity: If ERW projects overstate carbon removal and sell credits based on flawed data, it could undermine climate goals (net emissions increase )

Applications of ERW

ERW is being trialled in a variety of agricultural settings, including:

• Tea plantations in Darjeeling, India
• Sugarcane fields in Australia
• Oil palm fields in Malaysia
• Maize and soybean farms in the U.S.
• Brazil: First-ever verified ERW carbon credit project

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