Carbon Sequestration Sites

Engineers do not have to invent new holes for carbon dioxide. Three kinds already sit underground, ready-made by nature and industry.

A diagram of terrestrial and geological carbon sequestration routes for CO₂ from a coal-fired power plant. Original by LeJean Hardin and Jamie Payne, SVG version by Jarl Arntzen, via Wikimedia Commons. Licensed CC BY-SA 3.0.

📑 Contents

1Must Know
2Good to Know
3Test Yourself
4Great to Know
5Previous Year Questions

Three Places to Hide Carbon Underground

EnvEco0126

Coal Seams

Unmineable seams adsorb CO₂ onto coal itself

Oil & Gas Reservoirs

Depleted traps already proved they can hold fluids for millions of years

Saline Formations

Deep salty aquifers hold by far the largest storage capacity

The pattern: all three sites are genuine, currently-used carbon sequestration options, not a list with a trap option mixed in.

🏛️ Must Know

Three Recognized Carbon Sequestration Sites

Coal Seams Abandoned and uneconomic coal seams can store injected CO₂. Coal surfaces naturally adsorb the gas.
Oil and Gas Reservoirs Depleted oil and gas reservoirs are strong storage candidates. Their rock has already trapped hydrocarbons for millions of years.
Saline Formations Deep saline formations are porous rock layers filled with salty water. They offer the largest total storage capacity of the three.
All Three Count All three are genuine, currently studied or used carbon sequestration sites. None of them is a distractor option.

Good to Know

📘 Good to Know

How the Storage Actually Works

Supercritical Injection CO₂ is compressed into a dense, supercritical liquid state before injection deep underground.
A Sealing Cap Rock A safe storage site needs a porous reservoir rock to hold the CO₂. It also needs an impermeable cap rock on top, to stop the gas rising back up.
Saline Formations Dominate Capacity Because deep saline aquifers underlie huge areas, most commercial-scale CO₂ storage is expected to happen there rather than in coal seams.

📝 Previous Year Questions

UPSC CSP 2017 — Potential Sites for Carbon Sequestration

UPSC 2017 Abandoned coal seams, depleted oil and gas reservoirs, and subterranean saline formations are all potential carbon sequestration sites. See UPSC CSP 2017 GS Paper I, Q25. View this question.

Test Yourself

Great to Know

🌟 Great to Know

Why This Matters for Climate Policy

Part of CCS These sites are the storage step of Carbon Capture and Storage, a technology aimed at cutting emissions from coal and gas power plants.
Not Yet at Scale Even though the geology works, few commercial CO₂ injection projects in coal beds exist today, because coal seams hold less capacity than oil, gas, or saline sites.
Connects to Other PYQ Facts Geological sequestration is one strategy in the same broader climate toolkit as geoengineering approaches like stratospheric aerosol injection.

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