Enhanced Rock Weathering (ERW)

GS3 – Environment

Context:

ERW is emerging as a viable method for carbon sequestration by spreading crushed rock over agricultural lands to accelerate natural weathering.

Mechanism of ERW:

• Carbon Capture Process:
  • CO₂ from air or soil dissolves in rainwater, forming carbonic acid.
  • This reacts with rocks, breaking down minerals and storing carbon as bicarbonate, which may convert to limestone.
• Method:
  • Finely ground, fast-weathering rocks like basalt are spread over farmland to increase the surface area for chemical reactions, enhancing CO₂ absorption.

Advantages:

• Soil Fertility Enhancement:
  • Increases alkalinity and nutrient availability, boosting crop productivity.
• Cost Efficiency:
  • Basalt is abundant and often a byproduct of quarrying, making the process economical.
• Environmental Benefits:
  • Can neutralise acidic runoff, preventing ocean acidification and indirect CO₂ emissions.

Challenges and Risks:

• Heavy Metal Contamination:
  • Some rocks may contain toxic elements like nickel or chromium.
• Health Hazards:
  • Inhalation of fine rock dust poses respiratory risks without adequate safety gear.
• Carbon Accounting Concerns:
  • Overestimating CO₂ capture could result in misleading emission offsets.

Global Developments:

• Brazil: Issued the first verified ERW carbon removal credits in the world.
• India: Mati Carbon, an Indian ERW startup, won the $50 million XPRIZE Carbon Removal award.