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?
Contents17
- AOnly one
- BOnly two
- CAll three
- DNone
Show answer
Answer: (C) All three
All three are methods of carbon capture and sequestration:
Spreading crushed basalt rock on farmland (enhanced rock weathering) helps soil absorb CO₂ — correct.
Adding lime to seawater increases its alkalinity, allowing the ocean to absorb more CO₂ — correct.
Injecting captured CO₂ into deep underground rock formations stores it permanently — correct.
Answer is (c) All three.
Carbon capture and sequestration became a major focus after COP26 and COP27 climate summits, with countries needing specific technologies to meet net-zero commitments by 2070.
UPSC is testing whether students can distinguish between different types of carbon capture methods - natural enhancement, ocean-based, and industrial capture with storage.
The question checks knowledge of emerging geoengineering techniques beyond just tree planting or renewable energy.
Enhanced Rock Weathering
Environment basalt rock farmlands
Enhanced Rock Weathering: Basalt for Carbon Capture
Enhanced rock weathering spreads crushed basalt on farmlands to absorb CO₂ from atmosphere
Basalt is rich in minerals that react with CO₂ and water to form stable carbonates
Process mimics natural weathering but accelerated through fine grinding and spreading
Additional benefit: improves soil fertility and crop yields
What It Is
Enhanced rock weathering is a geoengineering technique that spreads finely crushed basalt rock on agricultural land. When basalt weathers naturally, it absorbs CO₂ from the atmosphere and locks it into stable mineral carbonates in the soil.
How It Works
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`**Mine and crush basalt**
Basalt rock is ground into fine powder to increase surface area`"]
s2["`**Spread on farmlands**
Powdered basalt is distributed across agricultural fields`"]
s3["`**Natural weathering begins**
Rain and soil moisture react with basalt minerals`"]
s4["`**CO₂ absorption**
Atmospheric CO₂ dissolves and forms stable carbonate minerals`"]
s5["`**Permanent storage**
Carbon is locked in soil as mineral carbonates for thousands of years`"]
s1 --> s2
s2 --> s3
s3 --> s4
s4 --> s5Key Advantages
Permanent storage — carbon locked as minerals for geological timescales
Soil improvement — adds nutrients like potassium, magnesium, and calcium
Crop yield increase — studies show 5-15% higher agricultural productivity
Large scale potential — could theoretically capture billions of tons of CO₂ annually
Co-benefits — reduces soil acidity and improves water retention
Trap: Confusing with biochar or organic carbon sequestration — this is mineral weathering, not biological
Trap: Thinking any rock works — specifically basalt and other mafic rocks rich in calcium and magnesium
Trap: Assuming it's theoretical — field trials are already underway in multiple countries
Ocean Alkalinity Enhancement
Environment alkalinity oceans lime
Ocean Alkalinity Enhancement: Adding Lime to Seawater
Ocean alkalinity enhancement adds lime to seawater to increase CO₂ absorption capacity
Higher alkalinity allows oceans to dissolve more atmospheric CO₂ without becoming acidic
Uses lime (calcium hydroxide) or crushed limestone as alkaline materials
Addresses both climate change and ocean acidification simultaneously
Scientific Basis
Oceans naturally absorb about 25% of global CO₂ emissions but become more acidic in the process. Ocean alkalinity enhancement adds alkaline materials like lime to seawater, increasing its pH and buffering capacity — allowing it to absorb much more CO₂ without harmful acidification.
Methods & Materials
Material | Chemical Formula | Source | Application Method |
|---|---|---|---|
Lime (slaked lime) | Ca(OH)₂ | Heated limestone | Direct addition to seawater |
Crushed limestone | CaCO₃ | Quarried limestone | Spreading on ocean surface |
Olivine powder | (Mg,Fe)₂SiO₄ | Mined olivine rock | Coastal or offshore distribution |
Sodium hydroxide | NaOH | Industrial production | Controlled injection systems |
Potential & Challenges
Massive scale needed — requires processing billions of tons of limestone annually
Energy intensive — producing lime requires heating limestone to 900°C
Ecological risks — could disrupt marine ecosystems if not carefully managed
Monitoring complexity — difficult to track effectiveness across vast ocean areas
Natural precedent — rivers naturally carry alkaline minerals to oceans
Trap: Thinking this increases ocean acidity — it actually reduces acidity by raising pH
Trap: Confusing with ocean iron fertilization — this adds alkaline minerals, not nutrients
Trap: Assuming it's purely theoretical — small-scale trials are being conducted
Carbon Capture & Storage (CCS)
Environment carbon dioxide industries subterranean mines carbonated waters
Carbon Capture & Storage: Industrial CO₂ Sequestration
CCS captures CO₂ from industrial sources and stores it permanently underground
CO₂ is compressed and injected as carbonated water into deep rock formations
Target sites include depleted oil/gas fields, saline aquifers, and abandoned mines
Technology is commercially operational at multiple facilities worldwide
Core Process
Carbon Capture and Storage (CCS) is a proven technology that captures CO₂ emissions from large industrial sources — power plants, cement factories, steel mills — and transports it to secure underground storage sites where it remains permanently trapped.
CCS Process Chain
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`**CO₂ Capture**
Extract CO₂ from industrial flue gases using chemical solvents`"]
s2["`**Compression**
Compress captured CO₂ into liquid form for transport`"]
s3["`**Transport**
Move compressed CO₂ via pipelines or ships to storage sites`"]
s4["`**Injection**
Pump CO₂ deep underground into porous rock formations`"]
s5["`**Storage**
CO₂ trapped permanently in rock pores, often as carbonated water`"]
s1 --> s2
s2 --> s3
s3 --> s4
s4 --> s5Storage Site Types
Storage Type | Depth | Capacity | Examples |
|---|---|---|---|
Depleted oil/gas fields | 1-4 km | High | North Sea fields, Texas oil wells |
Deep saline aquifers | 800m-3km | Very high | Sleipner project (Norway) |
Abandoned coal mines | 200m-1km | Medium | Former mining regions |
Basalt formations | 400m-2km | High | CarbFix project (Iceland) |
India's CCS Initiatives
ONGC pilot project — testing CO₂ injection in depleted oil fields for enhanced recovery
Thermal power focus — coal plants identified as priority targets for CCS retrofitting
NTPC collaboration — working with international partners on CCS demonstration projects
Geological surveys — mapping potential storage sites in sedimentary basins
Policy framework — developing regulations for CO₂ transport and storage
Trap: Confusing CCS with carbon offsetting through trees — this is direct industrial capture
Trap: Thinking CO₂ storage is temporary — properly stored CO₂ remains trapped for thousands of years
Trap: Missing carbonated water detail — CO₂ often dissolves in groundwater for safer storage
Geoengineering & Carbon Removal
Environment carbon capture sequestration
Geoengineering: Large-Scale Climate Intervention Methods
Geoengineering includes both carbon removal and solar radiation management techniques
Carbon Dioxide Removal (CDR) actively extracts CO₂ from atmosphere for permanent storage
Most methods are experimental with unknown long-term ecological impacts
Solar Radiation Management (SRM) reflects sunlight to cool Earth without removing CO₂
Geoengineering Categories
# Geoengineering Methods
## Carbon Dioxide Removal (CDR)
- Enhanced rock weathering
- Ocean alkalinity enhancement
- Direct air capture
- Afforestation
- Biochar
- Blue carbon
## Solar Radiation Management (SRM)
- Stratospheric aerosol injection
- Marine cloud brightening
- Space-based reflectors
- Surface albedo modification
## Industrial CCS
- Point-source capture
- Geological storage
- Enhanced oil recovery
- MineralizationCDR vs SRM Comparison
Aspect | Carbon Dioxide Removal (CDR) | Solar Radiation Management (SRM) |
|---|---|---|
Primary goal | Remove CO₂ from atmosphere | Reflect sunlight to reduce heating |
Speed of effect | Slow (decades to centuries) | Fast (months to years) |
Permanence | Addresses root cause | Temporary — stops when discontinued |
Ocean acidification | Reduces acidification | No effect on acidification |
Risk level | Generally lower risk | Higher risk of unintended consequences |
Current status | Some methods operational | Mostly theoretical/experimental |
Global Governance Issues
No international treaty specifically governs geoengineering research or deployment
Unilateral deployment risk — single countries could affect global climate
IPCC recognition — included in climate mitigation pathways since AR5 report
Research vs deployment — scientific research proceeding, large-scale deployment remains controversial
Moral hazard concern — might reduce motivation for emissions reduction
Trap: Treating all geoengineering as futuristic — some CDR methods like CCS are already operational
Trap: Confusing mitigation with geoengineering — reducing emissions vs actively removing CO₂
Trap: Assuming geoengineering replaces emission cuts — IPCC treats it as complement, not substitute