Question 75 from UPSC CSE 2017 - Environment

Question

In the context of mitigating the impending global warming due to anthropogenic emissions of carbon dioxide, which of the following can be potential sites for carbon sequestration?
1. Abandoned and uneconomic coal seams
2. Depleted oil and gas reservoirs
3. Subterranean deep saline formations
Select the correct answer using the code given below:

IASCODEX · Accepted Answer

Correct Option: D. 1, 2, and 3

Strategy: Identify the known geological carbon sequestration sites from the provided options.

Key Info: ### Carbon Sequestration
Carbon sequestration refers to the long-term storage of carbon dioxide (CO2) or other forms of carbon to mitigate or defer global warming. It involves capturing atmospheric carbon dioxide and storing it in various geological, terrestrial, or oceanic reservoirs. This process is a key component of Carbon Capture, Utilization, and Storage (CCUS) technologies aimed at reducing anthropogenic greenhouse gas emissions.

### Potential Sites for Geological Carbon Sequestration
Geological sequestration involves injecting CO2, usually in supercritical fluid form, into deep underground rock formations. The primary types of geological formations considered suitable for CO2 storage include:

- **1. Abandoned and uneconomic coal seams**: Coal has a high affinity for CO2 and can adsorb it more readily than methane. Injecting CO2 into unmineable coal seams can sequester carbon while also enhancing coal bed methane (ECBM) recovery, as the CO2 displaces the adsorbed methane, making it an economically attractive option.
- **2. Depleted oil and gas reservoirs**: These formations are ideal because they have historically trapped fluids (oil and gas) for millions of years, demonstrating their sealing capability. The geological characteristics are well understood from past exploration and production activities. CO2 injection can also be used for Enhanced Oil Recovery (EOR) or Enhanced Gas Recovery (EGR), where the injected CO2 helps to extract additional hydrocarbons.
- **3. Subterranean deep saline formations (or deep saline aquifers)**: These are deep underground rock formations saturated with saline water (brine) that are unsuitable for drinking water or agriculture. They are considered to have the largest storage capacity globally for CO2 sequestration. The CO2 is injected deep below the surface, where it dissolves in the brine, becomes trapped as a separate phase beneath impermeable caprocks, or mineralizes over long periods.

IASCODEX · Answer

Option A: 1 and 2 only

IASCODEX · Answer

Option B: 3 only

IASCODEX · Answer

Option C: 1 and 3 only