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In the context of mitigating the impending global warming due to anthropogenic emissions of carbon dioxide, which of the following can be the 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 :
Explanation
The correct answer is option D because all three sites mentioned are potential locations for carbon sequestration.
Abandoned and uneconomic coal seams can be used for carbon injection, and such injection may sometimes result in the displacement of methane, which could be used as a fuel.[1] Depleted oil reserves are explicitly mentioned as artificial sinks for carbon sequestration.[2] The oil and gas industries have used carbon capture for decades as a way to enhance oil and gas recovery.[2]
Regarding subterranean deep saline formations, CO² can be effectively stored in the earth's subsurface by geodynamic trapping and solubility trapping.[3] Additionally, carbon dioxide can react with the minerals, fluids, and organic matter to form stable compounds or minerals through mineral carbonation.[3] Deep saline aquifers represent suitable geological formations where these trapping mechanisms can operate effectively.
Since all three options—uneconomic coal seams, depleted oil and gas reservoirs, and subterranean deep saline formations—are validated as potential carbon sequestration sites, option D (1, 2 and 3) is correct.
Sources- [1] https://www.ipcc.ch/site/assets/uploads/2018/03/srccs_wholereport-1.pdf
- [2] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 21: Mitigation Strategies > zr.r.r. Sinks > p. 281
- [3] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 21: Mitigation Strategies > Geologic Sequestration Trapping Mechanisms > p. 282
PROVENANCE & STUDY PATTERN
Guest previewThis is a classic 'Applied Environment' question. It moves beyond the definition of CCS to its implementation. While 'Depleted Oil Reserves' is a direct book fact (Shankar), the others require knowing the 'Big Three' geological storage types often cited in climate reports (IPCC).
This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.
Web source
Presence: 5/5
"(Koide et al., 1992) or into unminable coal seams (Gunter et al., 1997); in the latter case, such injection may sometimes result in the displacement of methane, which could be used as a fuel."
Why this source?
- Explicitly identifies injection of CO2 into unminable (uneconomic) coal seams as a storage option.
- Notes that CO2 injection into such seams can displace methane, indicating a practical trapping/interaction mechanism and a potential co-benefit.
Web source
Presence: 4/5
"out (retained) by the coal reservoir, because it has higher sorption selectivity than N2 and CH4."
Why this source?
- States that coal reservoirs can retain (adsorb) CO2 because of higher sorption selectivity relative to N2 and CH4.
- Supports the mechanism by which coal seams can act as CO2 storage sites (sorption trapping).
- Explicitly identifies injection of CO2 into unminable (uneconomic) coal seams as a storage option.
- Notes that CO2 injection into such seams can displace methane, indicating a practical trapping/interaction mechanism and a potential co-benefit.
- States that coal reservoirs can retain (adsorb) CO2 because of higher sorption selectivity relative to N2 and CH4.
- Supports the mechanism by which coal seams can act as CO2 storage sites (sorption trapping).
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 21: Mitigation Strategies > 21.1. CARBON SEQUESTRATTON: > p. 281
Strength: 5/5
“• Carbon capture and storage, also known as CCS or carbon sequestration, describes the technologies designed to tackle global warming by capturing CO₂ at power stations, industrial sites or even directly from the air and permanently storing it underground. • Carbon sequestration describes long-term storage of carbon dioxide or other forms of carbon to either mitigate or defer global warming.”
Why relevant
Defines carbon capture and storage (CCS) as capturing CO2 and permanently storing it underground, establishing that underground storage is an accepted mitigation approach.
How to extend
A student can combine this with facts about coal seams being underground reservoirs to ask whether specific seam geology could serve as CCS sites.
Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 1: Geological Structure and formation of India > The Damuda Series > p. 17
Strength: 4/5
“The Damuda series belongs to the Middle Gondwana Period which contains enormous deposits of coal seams.The coal seams are thicker and more elongated in the eastern coal fields than in the west. The important coal bearing areas of this period are Raniganj, Jharaia, Karanpura, and Bokaro of the Damodar basin, Singrauli, Korba, and Pench valley in Chhattigarh and Madhya Pradesh, Talcher in Mahanadi Basin in Odisha, and Singareni of Satpura Basin in Madhya Pradesh. The Jhingurda Coal Seam with a thickness of about 131 m is the thickest coal seam in India. The Gondwana rocks are also found in Himalayas from Kashmir to Arunachal Pradesh and”
Why relevant
Describes coal seams as enormous, thick and geographically distributed underground deposits (Damuda series), indicating the physical existence of substantial underground coal strata.
How to extend
One could use a geological map to locate thick/abandoned seams and then evaluate their depth, extent and structural setting for potential CO2 storage.
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 2: Functions of an Ecosystem > L) The Carbon Cycle > p. 19
Strength: 4/5
“In deep oceans such carbon can remained buried for millions of years till geological movement may lift these rocks above sea level. These rocks may be exposed to erosion, releasing their carbon dioxide, carbonates and bicarbonates into streams and rivers. Fossil fuels such as coals, oil and natural gas etc. are organic compounds that were buried before they could be decomposed and were subsequently. transformed by time and geological processes into fossil fuels. When they are burned the carbon stored in them is released back into the atmosphere as carbon-dioxide.”
Why relevant
Notes that fossil fuels were buried and can remain buried for millions of years until geological movements expose them—showing that buried carbon reservoirs can be long-term underground stores.
How to extend
A student might infer that if buried carbon can remain sequestered naturally, engineered injection into stable buried formations (like seams) could likewise be long-term, subject to geological stability checks.
Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 8: Energy Resources > COAL DEPOSITS OF THE TERTIARY PERIOD > p. 6
Strength: 3/5
“The Tertiary coal deposits came into existence during the Eocene, the Oligocene, and Miocene periods. Coal of this period is found in Arunachal Pradesh, Assam, Meghalaya, Nagaland, Rajasthan, Gujarat, Tamil Nadu, Kerala, West Bengal, and Jammu and Kashmir states. It is also known as brown coal. Containing more moisture, it has less carbon content. The total tertiary reserves of coal are 1588 million tonnes. Tamil Nadu: The state of Tamil Nadu has the largest deposits of lignite at Neyveli in the South Arcot district. The seams are 10 to 12 m in thickness. Its carbon and moisture contents are 30– 40% and 20%, respectively, while the volatile matter varies between 40 to 45%.”
Why relevant
Gives an example of tertiary coal deposits (e.g., Neyveli lignite) with seam thickness (10–12 m), showing that some seams are sufficiently thick to consider as discrete underground units.
How to extend
Using seam thickness and location data, a student could estimate storage volume potential and assess whether abandoned seams might hold meaningful CO2 volumes.
Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 27: Fuel and Power > Types of coal > p. 265
Strength: 3/5
“The bituminous coal, occurring in seams that have been highly compressed, is black, very hard and burns readily with great heat. As it is relatively smokeless, like anthracite, it is extensively used as 'bunker coal' in steamships, and in locomotives and engines where soot accumulation is undesirable. (b) Coking coal. This is a very useful type of coal which is burnt in closed ovens to drive off the volatile matter and increase its carbon content. This particular class of coal softens and fuses while burning and produces coke, a hard, grey porous material, which is used in blast furnaces to extract iron from its ores.”
Why relevant
Describes physical characteristics of bituminous/coking coal occurring in compressed seams, implying varied seam properties (density, compression) that could affect fluid flow and storage behavior.
How to extend
A student could extend this by checking whether seam permeability and compaction (not given here) would permit CO2 injection and retention in specific coal types.
Defines carbon capture and storage (CCS) as capturing CO2 and permanently storing it underground, establishing that underground storage is an accepted mitigation approach.
A student can combine this with facts about coal seams being underground reservoirs to ask whether specific seam geology could serve as CCS sites.
Describes coal seams as enormous, thick and geographically distributed underground deposits (Damuda series), indicating the physical existence of substantial underground coal strata.
One could use a geological map to locate thick/abandoned seams and then evaluate their depth, extent and structural setting for potential CO2 storage.
Notes that fossil fuels were buried and can remain buried for millions of years until geological movements expose them—showing that buried carbon reservoirs can be long-term underground stores.
A student might infer that if buried carbon can remain sequestered naturally, engineered injection into stable buried formations (like seams) could likewise be long-term, subject to geological stability checks.
Gives an example of tertiary coal deposits (e.g., Neyveli lignite) with seam thickness (10–12 m), showing that some seams are sufficiently thick to consider as discrete underground units.
Using seam thickness and location data, a student could estimate storage volume potential and assess whether abandoned seams might hold meaningful CO2 volumes.
Describes physical characteristics of bituminous/coking coal occurring in compressed seams, implying varied seam properties (density, compression) that could affect fluid flow and storage behavior.
A student could extend this by checking whether seam permeability and compaction (not given here) would permit CO2 injection and retention in specific coal types.
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