In News:

Enhanced Rock Weathering (ERW) is emerging as a novel nature-based carbon removal strategy, gaining global traction from Brazil’s sugar plantations to tea estates in India. It is being explored as a scalable solution to climate change through natural carbon capture mechanisms.

What is Enhanced Rock Weathering (ERW)?

• Definition: ERW is a geoengineering technique that accelerates the natural chemical process of rock weathering to capture and store atmospheric carbon dioxide (CO?).
• Scientific Basis:
  • Natural weathering involves the breakdown of silicate rocks through carbonic acid, formed when CO? dissolves in water, eventually locking the carbon in stable forms like bicarbonate or limestone.
  • ERW accelerates this process using fast-weathering rocks like basalt, ground into fine particles to maximize surface area and reactivity.

Effectiveness and Challenges

• Potential Carbon Removal:
  • A US-based study found that 50 tonnes of basalt/hectare/year could potentially remove up to 10.5 tonnes of CO?/hectare over four years.
  • However, field trials in Malaysia (oil palm) and Australia (sugarcane) have shown lower than expected carbon capture rates.
• Key Variables Affecting Effectiveness:
  • Rock type and mineralogy
  • Soil characteristics
  • Temperature and rainfall patterns
  • Land management practices
• Measurement Difficulties:
  • Current techniques often overestimate CO? capture due to detection of cations that form even in the absence of carbonic acid reactions.
  • Risk: This can lead to inaccurate carbon credit claims, undermining offset integrity.

Co-Benefits of ERW

• Soil Health Improvement:
  • Increases soil alkalinity → Improves nutrient availability and crop productivity.
  • Contributes to soil formation and resilience.
• Resource Efficiency:Basalt is abundant and often a quarrying by-product, lowering costs and emissions associated with mining.
• Ocean Acidification Mitigation:Even if CO? isn't sequestered directly, rock in the soil can neutralize acidic runoff, preventing CO? release from aquatic systems downstream.

Risks and Concerns

• Health & Safety:
  • Finely crushed rock may contain toxic heavy metals (depending on composition).
  • Protective equipment is necessary during application.
• Carbon Credit Integrity:Overestimated CO? removal may allow companies to offset emissions inaccurately, leading to net increase in atmospheric carbon.

Global Adoption and Projects

• Countries Involved:Brazil, India, USA, Europe, and Latin America are trialing or implementing ERW.
• India Focus:Trials underway in Darjeeling tea plantations and other agricultural regions through startups like Mati Carbon.
• Global Milestones:
  • First verified ERW carbon removal credits issued from a Brazilian project.
  • Google signed the largest ERW deal for 200,000 tonnes of CO? removal credits (to be delivered by early 2030s).
  • Terradot, an ERW company, sold 90,000 tonnes of carbon credits for $27 million, backed by firms like H&M.

Investor Interest and Innovation Push

• Private Sector Engagement:ERW has attracted big tech, fast fashion, and aviation sectors seeking nature-based offset solutions.
• Prize Recognition:Mati Carbon won the $50 million X Prize for carbon removal, recognizing the potential scalability and innovation of ERW.