Question map
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
Full viewThis 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.
- Statement 1: Can abandoned and uneconomic coal seams be used as potential sites for carbon dioxide sequestration to mitigate global warming from anthropogenic CO2 emissions?
- Statement 2: Can depleted oil and gas reservoirs be used as potential sites for carbon dioxide sequestration to mitigate global warming from anthropogenic CO2 emissions?
- Statement 3: Can subterranean deep saline formations be used as potential sites for carbon dioxide sequestration to mitigate global warming from anthropogenic CO2 emissions?
- 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).
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.
- Explicitly lists depleted oil reserves as an example of artificial carbon sinks.
- Notes that oil and gas industries have long used carbon capture (e.g., for enhanced oil/gas recovery), linking depleted reservoirs to CO2 injection practices.
- Describes geologic sequestration mechanisms (mineral carbonation, solubility and geodynamic trapping) that enable effective subsurface CO2 storage.
- Implies that subsurface formations (such as reservoirs) can store CO2 through established trapping processes.
- Identifies Carbon Capture and Sequestration (CCS) as a recognized strategy to reduce CO2 emissions, situating reservoir storage within mitigation policy options.
- Positions CCS alongside other mitigation measures, supporting the relevance of geological sinks as a mitigation tool.
- Defines Carbon Capture and Storage (CCS) as capturing CO2 and permanently storing it underground to tackle global warming.
- Establishes the general concept that CO2 can be stored in subsurface formations as a mitigation strategy.
- Describes geologic sequestration mechanisms (mineral carbonation, solubility trapping) that enable long-term CO2 storage in the Earth's subsurface.
- Specifies that combinations of trapping mechanisms make subsurface storage effective, supporting the feasibility of deep formation storage.
- Documents the existence of extensive aquifers and notes coastal regions with saline aquifers, indicating deep subsurface saline units in groundwater systems.
- Provides contextual evidence that deep saline groundwater formations are present and could be considered as subsurface reservoirs.
- [THE VERDICT]: Sitter. Directly solvable from Shankar IAS Environment (Chapter on Mitigation Strategies) combined with basic scientific awareness.
- [THE CONCEPTUAL TRIGGER]: Climate Change Mitigation > Technological Solutions > Carbon Capture & Storage (CCS).
- [THE HORIZONTAL EXPANSION]: Memorize the 3 primary geological traps: 1) Depleted Oil/Gas fields (proven, EOR benefit), 2) Deep Saline Aquifers (largest potential capacity), 3) Unminable Coal Seams (adsorption trapping). Also add 'Basalt Formations' (Mineral Carbonation) to your notes.
- [THE STRATEGIC METACOGNITION]: When a technology (like CCS) is in the news, prepare its 'Dimensions': Process (Capture), Location (Storage), and Risks. Don't stop at the definition; ask 'Where does the carbon go?'
CCS is the general technology of capturing CO2 and storing it underground, which is the class of solutions the statement asks about.
High-yield for GS environment and climate-change questions: explains a primary mitigation technology, links to energy policy and international commitments, and frames questions on technical and socio‑economic feasibility. Knowing CCS helps answer policy, technological and ethical dimensions of mitigation.
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 21: Mitigation Strategies > 21.1. CARBON SEQUESTRATTON: > p. 281
Shows that fossil fuels (including coal) store carbon that is released as CO2 when burned—motivating the need for sequestration.
Core concept for climate-change questions: links causes (fossil fuel combustion) to impacts (atmospheric CO2) and to mitigation options (like CCS). Useful across environment, energy and disaster/impact assessments in UPSC papers.
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 2: Functions of an Ecosystem > L) The Carbon Cycle > p. 19
Details on coal seams (thickness, distribution and quality) are relevant background when evaluating whether particular seams (abandoned/uneconomic) might be physically suitable for underground storage.
Important for questions linking resource geography and environmental policy: helps assess site feasibility, regional mitigation options, and trade-offs between mining and environmental uses. Useful for case-based questions on energy geography and land-use decisions.
- Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 1: Geological Structure and formation of India > The Damuda Series > p. 17
- Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 8: Energy Resources > Source: Provisional Coal Statistics 2016–17, Coal Controller's Organization, Kolkata. > p. 4
CCS is named as a mitigation strategy in the references and directly relates to storing CO2 in engineered or geological sinks.
High-yield for UPSC because CCS appears in policy and environment questions on mitigation. It links climate policy, technology, and energy sectors and enables answers on mitigation options, trade-offs, and implementation challenges.
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 17: Climate Change > Reducing Carbon Dioxide Emissions > p. 256
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 21: Mitigation Strategies > zr.r.r. Sinks > p. 281
References describe mineral carbonation and subsurface trapping (solubility/geodynamic) as ways CO2 is stored underground.
Important for explaining technical feasibility and permanence of subsurface storage in essays and mains answers; connects geology, environmental science, and mitigation policy; useful for questions on site suitability and risks.
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 21: Mitigation Strategies > Geologic Sequestration Trapping Mechanisms > p. 282
Depleted oil/gas reservoirs are explicitly listed as artificial sinks and industry practice of CO2 use for enhanced recovery is mentioned.
Valuable for case-based answers: shows practical precedent (EOR) and helps evaluate pros/cons of repurposing hydrocarbon infrastructure for climate goals; bridges energy security and climate mitigation topics.
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 21: Mitigation Strategies > zr.r.r. Sinks > p. 281
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 21: Mitigation Strategies > Geologic Sequestration Trapping Mechanisms > p. 282
CCS is the central mitigation technology referenced for capturing CO2 and storing it underground to reduce anthropogenic emissions.
High-yield for UPSC: CCS appears in climate-mitigation questions and links to energy policy, industrial emissions control, and geopolitics of fossil fuels. Understanding CCS allows candidates to evaluate mitigation options, policy trade-offs, and technological challenges; useful in essay and mains answers.
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 21: Mitigation Strategies > 21.1. CARBON SEQUESTRATTON: > p. 281
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 17: Climate Change > Reducing Carbon Dioxide Emissions > p. 256
Mineral Carbonation in Basalt Rocks. Unlike saline aquifers where CO2 stays as a fluid, in Basalt (rich in Calcium/Magnesium), CO2 chemically reacts to form solid rock (calcite/magnesite) within years. Look up the 'CarbFix' project in Iceland.
The 'Science of Possibility' Rule. The question asks what 'can be' a potential site. In geology, almost any porous, stable underground structure is a candidate. Unless an option is scientifically absurd (e.g., 'Active Volcanic Vent'), broad geological categories are usually all correct. In 'potential application' questions, 'All of the above' has a >80% hit rate.
Connect CCS to Energy Security (Mains GS3). 'Enhanced Oil Recovery' (EOR) uses captured CO2 to pressurize and extract residual oil. This creates a Mains debate: Is CCS a climate solution or a lifeline for the fossil fuel industry?