UPSC Prelims 2023 Q68: Environment & Ecology – Climate Change & Greenhouse Gases

UPSC Prelims 2023, General Studies Paper I · Environment & Ecology

Consider the following activities : 1. Spreading finely ground basalt rock on farmlands extensively 2. Increasing the alkalinity of oceans by adding lime 3. Capturing carbon dioxide released by various industries and pumping it into abandoned subterranean mines in the form of carbonated waters How many of the above activities are often considered and discussed for carbon capture and sequestration?

(a) Only one
(b) Only two
(c) All three
(d) None

Answer: (c) All three

Explanation

Carbon Capture and Sequestration (CCS) Activities

Activity	CCS Method	Verdict	Mechanism
1. Spreading finely ground basalt on farmlands	Enhanced rock weathering	TRUE	Basalt rock reacts with CO₂ in soil (enhanced weathering): CO₂ + minerals → bicarbonates → stored in ocean/soil. A natural carbon removal approach using silicate rocks.
2. Increasing ocean alkalinity by adding lime	Ocean alkalinity enhancement	TRUE	Adding calcium hydroxide (lime) to oceans raises pH and alkalinity, allowing oceans to absorb more CO₂ from the atmosphere. A proposed large-scale CDR (Carbon Dioxide Removal) method.
3. Capturing CO₂ and pumping into abandoned mines as carbonated water	Carbon mineralisation/geological storage	TRUE	CO₂ dissolved in water forms carbonic acid, which reacts with rock minerals to form stable carbonate minerals — permanent geological storage. Analogous to conventional CCS in depleted oil wells.

All three are genuine carbon capture methods → All three.

Answer: (c) All three.

Why each option is right or wrong

(a) Incorrect. 'Only one' — all three are discussed in scientific and policy literature as carbon capture and sequestration approaches.
(b) Incorrect. 'Only two' — ocean alkalinity enhancement is a well-recognised CDR method under IPCC assessment.
(c) CORRECT. All three activities — enhanced rock weathering (basalt), ocean alkalinity enhancement (lime), and carbonated water injection into mines — are discussed and assessed as CCS/CDR approaches.
(d) Incorrect. 'None' — enhanced rock weathering using basalt is one of the most promising near-term carbon removal strategies.

Key point

All three are legitimate CCS/CDR methods: Basalt weathering (silicate rock + CO₂ → carbonates), ocean lime addition (alkalinity → more CO₂ absorption), carbonated water in mines (geological mineralisation). All three used in IPCC CDR discussions.

Remember

All three activities are carbon capture and sequestration approaches: spreading basalt rock (enhanced weathering), adding lime to oceans (alkalinity enhancement), and injecting CO₂ as carbonated water into abandoned mines (geological mineralisation).

Common mistakes

Dismissing basalt spreading as too simple — enhanced rock weathering is scientifically validated and being tested at scale.
Thinking ocean alkalinity enhancement is untested — it is assessed in IPCC AR6 as a CDR method, though with uncertainties.
Not knowing carbonated water injection is a form of geological CCS — Iceland's CarbFix project uses this exact method.

Exam tip

CCS approaches: Geological (inject underground), Biological (forests, bioenergy), Chemical (direct air capture), Mineralisation (rock weathering, ocean alkalinity). All three in this question = mineralisation-type approaches. UPSC tests CCS awareness as a climate solution.

Sources

IPCC AR6 — Carbon Dioxide Removal Methods
Ministry of Environment — India's Carbon Sequestration Strategies

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