Limits of Carbon Storage

Context:

A new Nature study has found that the Earth can only safely hold about 1,460 billion tonnes of CO? underground, far less than earlier estimates.

Concept

Carbon Capture and Storage/Carbon Capture, Utilisation and Storageinvolves capturing CO? from large emission sources (power plants, cement, steel, refineries) and storing it deep underground in geological formations (~2 km depth).
Aim: Prevent release of anthropogenic CO? into the atmosphere, mitigate climate change, and enable low-carbon industrial transitions.

Process Stages

Capture:
- From stationary sources (power stations, hydrogen production, cement, steel, natural gas processing).
- Direct Air Capture and Storage (DACS) under research.

Transport:
- Via pipelines, ships, trucks, or rail, similar to natural gas transport.
Injection & Storage:
- Stored in saline aquifers, depleted oil/gas fields, deep coal seams, or basalts.
- CO? trapped in pore spaces ? dissolves in brine ? reacts to form stable minerals.
Utilisation (CCUS):
- - Enhanced Oil Recovery (EOR): injecting CO? into mature oil fields.
  - Production of fertilisers, fuels, plastics, and food products.
  - Currently, industry mostly uses naturally accumulated CO?, but anthropogenic CO? could replace this.

Geological Carbon Storage (GCS):

Involves capturing CO? from sources like power plants or the atmosphere and injecting it into deep rock formations.
Expected to help achieve Paris Agreement targets of limiting warming below 2°C.

Revised Capacity Estimates:

Previous estimates: ~11,800 billion tonnes of storage.
New safe limit:1,460 billion tonnes (just 10% of earlier figure).
High storage potential in Russia, USA, Saudi Arabia; low in India and Europe.

Implications:

Maximum possible reversal of warming through storage is only 7°C.
Storage alone cannot solve climate change ? emission cuts remain the primary solution.
Raises policy dilemma: whether to use storage to extend fossil fuel use or prioritize carbon removal for future generations.