UPSC Prelims 2025 Q36: Direct Air Capture and Its Uses — Explained
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.
- I and II only
- III only
- I, II and III
- None of the above statements is correct
Answer: (c) I, II and III
Statement-wise explanation
- I: correct — Direct Air Capture (DAC) uses chemical sorbents or solvents to pull CO2 straight out of the ambient air. If that CO2 is then stored permanently, the process removes carbon from the atmosphere; this is called DACCS (direct air capture with carbon storage). Climeworks' Orca plant in Iceland (about 4,000 tonnes of CO2 a year) and its Mammoth plant (designed for up to 36,000 tonnes a year, running since May 2024) both send their CO2 to Carbfix. Carbfix dissolves the CO2 in water and injects it into basalt, where it turns into carbonate rock.
- II: correct — CO2 captured from the air is a carbon feedstock, and industry already buys CO2 for food and beverages: carbonating drinks, dry ice, chilling and modified-atmosphere packaging. According to the IEA, the few DAC plants running today sell their CO2 mainly to the food and beverage industry. CO2 can also be built into polymers such as polycarbonates and polyurethanes. NITI Aayog's 2022 CCUS report lists polymers, chemicals, and food and beverage applications among the uses of captured CO2.
- III: correct — Synthetic aviation fuel (e-kerosene, or power-to-liquid fuel) is made by combining CO2 with hydrogen, ideally green hydrogen from renewable electricity. The two are turned into syngas and then into liquid hydrocarbons, usually by Fischer–Tropsch synthesis. When the carbon comes from the air, burning the fuel only returns CO2 that was taken out earlier, so the fuel is low-carbon, though not carbon-negative. In the IEA's Net Zero by 2050 pathway, about 35% of air-captured CO2 goes into synthetic fuels, mostly for aviation.
How to eliminate
Statement I is close to the definition of DAC. A technology that pulls CO2 out of the air is a carbon-removal tool if the CO2 is stored. Any option that leaves out Statement I is therefore very unlikely. That removes the 'III only' and 'None' options and leaves 'I and II only' against 'I, II and III'. Next, use one general principle: captured CO2 is the same molecule whatever its source, so it can go to any use that existing CO2 supply already serves (drinks, food, chemicals, fuels). That supports Statement II, and Statement III too, if you know that synthetic fuels are made from CO2 plus hydrogen. The fact to remember is that e-fuels and synthetic sustainable aviation fuel need a carbon source, and DAC is one of the main candidates. Note also the wording: every statement says 'can be'. That makes them claims about what is possible, which are seldom false for an emerging technology. There are no absolute words here to catch.
Know more
Direct Air Capture (DAC) takes CO2 out of ordinary air (about 0.04% CO2), not out of a chimney. Because air is so dilute, DAC needs more energy and costs more per tonne than capturing CO2 at a factory.
Two main designs
- Solid DAC: fans push air over filters coated with sorbents such as amines. Heating the filters to about 80–100 °C releases pure CO2. Climeworks uses this design.
- Liquid DAC: air passes through an alkaline (hydroxide) solution. The CO2 is released again at very high temperatures, around 900 °C. Carbon Engineering uses this design.
Where the captured CO2 goes
- Storage (DACCS): carbon removal that can be permanent, for example by mineralising it in basalt.
- Utilisation (DAC-U): drinks, greenhouses, polymers, building materials, and synthetic fuels made with hydrogen. Uses like fuels lock the carbon away only for a short time.
| Approach | Source of CO2 | Net effect |
|---|---|---|
| Point-source CCS/CCUS | Flue gas from power plants, cement, steel | Cuts new emissions |
| DAC + storage | Ambient air | Removes CO2 (negative emissions) |
| BECCS | Burning biomass, then capturing the CO2 | Removes CO2 |
| Enhanced weathering | Crushed silicate rock reacting with air and water | Removes CO2 |
| DAC + synthetic fuel | Ambient air | Roughly carbon-neutral cycle |
Why it matters: the IPCC treats carbon dioxide removal as necessary for net zero, to balance emissions that are hard to cut, such as those from aviation and agriculture. DAC still works at tiny scale: today's largest plants capture tens of thousands of tonnes a year, while the world emits tens of billions. It also needs a lot of low-carbon energy.
India link: the Union Budget 2026-27 set aside ₹20,000 crore for CCUS, and the first R&D roadmap for CCUS came out in December 2025.
In the news
In May 2024 Climeworks started Mammoth in Iceland, then the world's largest DAC plant. Interest in sustainable aviation fuel was also growing, and with it CO2-plus-hydrogen e-fuels. Together these kept DAC and its uses in the news before the 2025 Prelims.
NCERT Concepts to Revise
- Carbon capture, utilisation and storage: The capture-utilise-store framework is how to sort the question's three statements: storage versus industrial and fuel uses of captured CO2.
- Carbon capture and storage: Shows how capturing CO2 at a factory chimney differs from capturing it from open air, and what storing it involves.
- Green hydrogen: Synthetic aviation fuel needs hydrogen as well as carbon; the hydrogen's source decides whether the fuel is really low-carbon.