Carbon Dioxide Removal (CDR)

CDR refers to deliberate interventions to remove CO₂ from the atmosphere and store it durably, with the aim of reducing global greenhouse gas concentrations.

Direct Air Capture (DAC) and Geological Storage

• Machines capture CO₂ from air; compressed CO₂ injected into deep geological formations.(eg)Climeworks (Iceland), storing CO₂ in basalt rock formations.
• From direct point sources of CO₂ such as thermal plants these could be very effective.This could be injected into coal bed methane.Storing captured CO2 in coal beds (CO2-ECBM) can significantly increase the yield of coalbed methane (CBM) by displacing the lighter methane from the coal pores. As the injected CO2 is more strongly adsorbed onto the coal’s surface than methane, it causes methane to desorb and become available for recovery. 

Other important Carbon Dioxide Removal (CDR) pathways,

Biochar

• Biochar is a Charcoal-like substance from biomass (e.g., crop waste) obtained via pyrolysis.
• Biochar can be applied in degraded soils(eg)Biochar application in sub-Saharan Africa.
• It sequesters carbon for hundreds to thousands of years in soil; enhances soil fertility.

Enhanced Rock Weathering

• Spreading crushed silicate rocks on land to chemically bind CO₂.
• Accelerates natural carbon sequestration; improves soil health.(eg)Basalt rock application on croplands.

Ocean-Based Approaches

• Includes ocean alkalinity enhancement, seaweed farming, ocean fertilization.
• Promotes marine carbon uptake via photosynthesis or chemical processes.
• However, Ecological side effects are not fully understood.

Solar Radiation Management (SRM)

SRM involves reflecting a portion of solar radiation back into space to cool the Earth temporarily, without directly reducing greenhouse gases.These include:

• Stratospheric Aerosol Injection 

1. 1. • Injecting sulfate aerosols into the stratosphere to reflect sunlight.
      • The Problem is changes in rainfall patterns, ozone depletion, regional climate disruption.

• Marine Cloud Brightening

1. • Spraying seawater to make clouds more reflective.
   • The idea is to enhance cloud albedo over oceans to reduce warming.
   • However, it is still largely theoretical and experimental.

Main problems in Solar Radiation Management

• Does not reduce CO₂ or ocean acidification.
• Unequal regional effects (e.g., droughts in some areas).

Why in the news?

NITI Aayog, the Council on Energy, Environment and Water (CEEW), and the Centre for Social and Economic Progress (CSEP) co-hosted a high-level workshop on “Indian and Global Perspectives on Geoengineering – Science, Governance and Risks.

The discussions focused on two broad approaches: Carbon Dioxide Removal (CDR) and Solar Radiation Management (SRM)

The sessions examined issues in geoengineering science, economics and governance—including  robust monitoring, reporting, and verification (MRV) to ensure removals are real and durable, storage integrity for geological options, safeguards for vulnerable communities, and frameworks for global governance.