With reference to 'Direct Air Capture', an emerging technology, which of the following statements is/are correct? I. It can be used as a way of carbon sequestration. II. It can be a valuable approach for plastic production and in food processing. III. In aviation, it can be a source of carbon for combining with hydrogen to create synthetic low-carbon fuel. Select the correct answer using the code given below.
Contents16
- AI and II only
- BIII only
- CI, II and III
- DNone of the above statements is correct
Show answer
Answer: (C) I, II and III
Direct Air Capture (DAC) is a technology that literally pulls CO₂ directly out of the ambient air using chemical filters or solvents.
Once captured, this CO₂ can be used in several ways:
(I) Carbon sequestration — YES. The captured CO₂ can be permanently stored underground in geological formations (like depleted oil wells or saline aquifers). This is the most straightforward climate benefit — removing CO₂ from the atmosphere and locking it away. ✓
(II) Plastic production and food processing — YES. Captured CO₂ is a carbon source that can be used as a feedstock for making plastics (carbon-based polymers). In food processing, CO₂ is used for carbonation of beverages, as a preservative in food packaging (modified atmosphere packaging), and in processes like decaffeination. ✓
(III) Synthetic aviation fuel — YES. Captured CO₂ can be combined with green hydrogen (produced from renewable energy) to create synthetic kerosene — a low-carbon jet fuel. Aviation is one of the hardest sectors to decarbonize, and synthetic fuels from DAC are seen as a promising solution. Companies like Climeworks and Carbon Engineering are already working on this. ✓
All three statements are correct. Answer is (c).
Direct Air Capture technology can remove CO₂ from the atmosphere and either store it permanently underground or convert it into useful products like plastics, food additives, and synthetic fuels.
Major DAC facilities became operational in recent years, with companies like Climeworks launching commercial plants, making this technology a current topic in climate policy discussions.
UPSC is testing whether students understand DAC as both a carbon removal technology and a source of CO₂ for industrial applications, not just environmental benefits.
Direct Air Capture Technology
Environment Direct Air Capture DAC
Direct Air Capture (DAC): Technology & Applications
DAC technology pulls CO₂ directly from ambient air using chemical filters or solvents
Captured CO₂ can be permanently stored underground or used as feedstock for various products
Key applications: carbon sequestration, plastic production, food processing, and synthetic aviation fuel
Companies like Climeworks and Carbon Engineering are leading commercial development
What is DAC
Direct Air Capture (DAC) is an emerging technology that uses large industrial machines with chemical filters or liquid solvents to extract CO₂ directly from ambient air. Unlike capturing emissions from smokestacks, DAC pulls CO₂ from the open atmosphere where concentrations are much lower (~400 ppm).
How DAC Works
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`**Air Intake**
Giant fans draw ambient air into the DAC facility`"]
s2["`**Chemical Capture**
Chemical solvents or solid filters bind with CO₂ molecules`"]
s3["`**CO₂ Separation**
Heat or pressure releases pure CO₂ from the capture medium`"]
s4["`**Storage or Use**
Pure CO₂ is either stored permanently or used as feedstock`"]
s1 --> s2
s2 --> s3
s3 --> s4DAC Applications
Application | Use Case | Climate Benefit | Commercial Status |
|---|---|---|---|
Carbon Sequestration | Permanent underground storage in geological formations | Direct CO₂ removal | Pilot projects operating |
Plastic Production | CO₂ as carbon feedstock for polymers | Reduces fossil fuel demand | Early commercial |
Food Processing | Beverage carbonation, food packaging, decaffeination | Circular carbon use | Technically ready |
Synthetic Aviation Fuel | CO₂ + green hydrogen → synthetic kerosene | Decarbonizes hard-to-electrify sector | Demonstration phase |
Current Challenges
High energy consumption — DAC requires significant electricity, preferably from renewable sources
Cost barrier — Currently $600-1000 per tonne of CO₂, needs to drop to $100-200 for widespread adoption
Scale challenge — To make climate impact, needs deployment at gigatonne scale globally
Competition for renewable energy — DAC competes with other sectors for clean electricity
Don't confuse DAC with carbon capture at power plants — DAC pulls from ambient air, not smokestacks
All three PYQ statements are correct — DAC has multiple uses beyond just carbon storage
Aviation synthetic fuel is a key emerging application — combines captured CO₂ with green hydrogen
Carbon Sequestration Methods
Environment carbon sequestration
Carbon Sequestration: Natural & Technological Methods
Carbon sequestration means long-term storage of CO₂ to reduce atmospheric concentrations
Methods include natural (forests, soils) and technological (geological storage, DAC)
Geological sequestration stores CO₂ in underground formations for hundreds of years
Sequestration Methods
Method | Storage Location | Duration | Capacity | UPSC Relevance |
|---|---|---|---|---|
Forest Carbon | Trees, soil organic matter | 20-100 years | Limited by land area | REDD+, afforestation policies |
Soil Carbon | Agricultural soils | 10-50 years | High potential | Climate-smart agriculture |
Ocean Sequestration | Deep ocean, marine ecosystems | 100-1000 years | Very high | Blue carbon, ocean acidification |
Geological Storage | Depleted oil fields, saline aquifers | 100-1000 years | Very high | CCS technology, storage potential |
Direct Air Capture | Underground via captured CO₂ | Permanent | Scalable | Geoengineering, climate tech |
India's Carbon Sequestration
Forest cover target — India aims to increase forest cover to 33% of land area
Soil organic carbon — Degraded agricultural soils offer significant sequestration potential
Mangrove restoration — Blue carbon projects in coastal states like Gujarat, Odisha
CCS demonstration — NTPC and other PSUs exploring carbon capture and storage technologies
Sequestration vs absorption — sequestration implies long-term storage, not just temporary uptake
Natural vs technological — UPSC tests both biological and engineering approaches
Permanence matters — geological storage is more permanent than forest carbon
Synthetic Aviation Fuels
Environment synthetic low-carbon fuel aviation hydrogen
Synthetic Aviation Fuels: Technology & Climate Impact
Synthetic aviation fuel combines captured CO₂ with green hydrogen to create jet fuel
Aviation is a hard-to-electrify sector — synthetic fuels are key to decarbonization
Process called Power-to-Liquid (PtL) — converts renewable electricity into liquid fuel
Synthetic Fuel Production
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`**Green Hydrogen Production**
Renewable electricity splits water into H₂ and O₂`"]
s2["`**CO₂ Capture**
DAC or industrial capture provides CO₂ feedstock`"]
s3["`**Fischer-Tropsch Synthesis**
H₂ and CO₂ react to form hydrocarbon chains`"]
s4["`**Fuel Refining**
Raw hydrocarbons refined into jet fuel specifications`"]
s1 --> s2
s2 --> s3
s3 --> s4Why Aviation Needs This
Aviation accounts for 2-3% of global CO₂ emissions but is extremely difficult to decarbonize. Electric aircraft work only for short flights, and hydrogen requires completely new aircraft designs. Synthetic fuels can use existing aircraft and infrastructure while being carbon-neutral — the CO₂ released during combustion equals the CO₂ captured during production.
Current Challenges
Cost — Synthetic jet fuel costs 3-8 times more than conventional fuel
Energy intensity — Requires large amounts of renewable electricity for hydrogen production
Scale — Current production is tiny compared to aviation fuel demand
Policy support — Needs mandates and subsidies to compete with fossil fuels
Carbon-neutral, not carbon-free — synthetic fuels still emit CO₂ when burned, but it's recycled carbon
Green hydrogen essential — only works for climate if hydrogen comes from renewable energy
DAC connection — this PYQ tests understanding that captured CO₂ becomes fuel feedstock
Geoengineering Technologies
Environment
Geoengineering: Types, Technologies & Controversies
Geoengineering means deliberate large-scale intervention in Earth's climate system
Two main types: Solar Radiation Management (SRM) and Carbon Dioxide Removal (CDR)
DAC is a CDR technology — removes CO₂ from atmosphere
Highly controversial due to risks, governance, and moral hazard concerns
Geoengineering Classification
# Geoengineering Technologies
## Solar Radiation Management (SRM)
- Stratospheric Aerosol Injection
- Marine Cloud Brightening
- Space-based Reflectors
- Surface Albedo Modification
## Carbon Dioxide Removal (CDR)
- Direct Air Capture
- Bioenergy with CCS
- Ocean Alkalinization
- Enhanced Rock Weathering
## Hybrid Approaches
- Afforestation/Reforestation
- Soil Carbon Enhancement
- Blue Carbon ProjectsSRM vs CDR Comparison
Aspect | Solar Radiation Management | Carbon Dioxide Removal |
|---|---|---|
Mechanism | Reflects sunlight away from Earth | Removes CO₂ from atmosphere |
Speed | Fast effect (months to years) | Slow effect (decades) |
Cost | Relatively cheap | Currently expensive |
Reversibility | Effects stop quickly if halted | Permanent CO₂ removal |
Risks | High governance risks, side effects | Lower risks, proven concepts |
Examples | Stratospheric aerosols, cloud brightening | DAC, enhanced weathering, BECCS |
Controversies & Concerns
Moral hazard — might reduce pressure to cut emissions if technological fix seems available
Governance — who decides to deploy planetary-scale interventions?
Uneven effects — could benefit some regions while harming others
Termination problem — stopping SRM could cause rapid warming
DAC is CDR, not SRM — removes CO₂ rather than blocking sunlight
Not science fiction — DAC plants already operating commercially
Supplement, not replacement — geoengineering complements emission cuts, doesn't replace them