Enhanced Rock Weathering (ERW)

ERW means turning farmlands into carbon sinks. It is a carbon dioxide removal process that accelerates a natural geological mechanism. Finely crushed silicate rock (primarily basalt) is applied to agricultural soils. Carbon dioxide dissolved in rainwater reacts with the rock dust to form bicarbonate ions (HCO₃⁻). These ions are then transported through soils, aquifers, and rivers to the ocean, where the carbon is stored in stable forms for thousands of years (typically 10,000+ years).

In the process, farmlands are turned into effective carbon sinks while also improving soil mineral content and crop resilience, particularly in tropical smallholder farming systems.

Step-by-Step Process of ERW

1. Quarrying and Preparation

  • Suitable basalt (a calcium–magnesium silicate rock) is quarried from qualified sources.
  • The rock is finely crushed and graded to maximize surface area (critical for speeding up the chemical reaction).
  • The prepared rock dust is loaded onto trucks and transported to partner farms that meet compatibility criteria (soil type, climate, etc.).

2. Spreading on Farmland

  • The basalt dust is evenly spread across agricultural fields.
  • When rain falls, atmospheric CO₂ dissolves in the rainwater, forming a weak carbonic acid.
  • This acidic water reacts with the fine basalt particles in the soil, dissolving the rock and converting CO₂ into dissolved bicarbonate ions (HCO₃⁻).

Scientific reaction (simplified): Silicate minerals in basalt + CO₂ + H₂O → dissolved calcium/magnesium ions + bicarbonate (HCO₃⁻)

3. Transport and Long-Term Storage

  • The newly formed bicarbonate ions move downward through the soil profile into groundwater aquifers and rivers.
  • They are eventually carried to the ocean.
  • In the ocean, the carbon remains stored in dissolved form for millennia. Over geological timescales, a portion can precipitate into solid carbonate minerals or become incorporated into marine shells and coral reefs, locking it away even more permanently.

Key Supporting Points from the Process

  • Natural acceleration: Rock weathering has removed CO₂ from the atmosphere for billions of years. Crushing the rock dramatically increases the reactive surface area, speeding up the process from geological timescales to human-relevant ones.
  • Co-benefits: In tropical soils, the basalt releases essential nutrients (calcium, magnesium, etc.), improves soil chemistry, and enhances crop resilience and productivity.
  • Durability: Carbon is stored for 10,000+ years in oceans and aquifers — far longer than many other carbon removal methods.
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