Science and Technology › Energy technology
हिन्दी — Read in HindiHydrogen and bioenergy
Fuel cells, ethanol blending and its feedstock, biogas, and aviation fuel made from biomass. Prelims has asked about the raw materials allowed under the National Policy on Biofuels and how green hydrogen is produced.
Foundation note: The colours of hydrogen
UPSC has asked
- Prelims 2025: battery electric and fuel cell vehicles as alternative powertrains
- Prelims 2023: uses of green hydrogen as fuel and in fuel cells
- Prelims 2020: raw materials allowed under the National Policy on Biofuels
Showing 2 of 6 articles, those that changed from 1 to 31 July 2026.Show all
Biofuels
Prelims and Mains
E20 is petrol blended with 20 per cent anhydrous ethanol by volume, and since 1 April 2026 it is the only petrol sold in India, at a minimum Research Octane Number of 95.
The case for
- About ₹2 lakh crore saved in foreign exchange, the government says
- Carbon monoxide and unburnt hydrocarbon emissions fall
- Cane ethanol cuts life-cycle greenhouse gases by about 50 to 70 per cent against petrol
- Mileage falls about 6 to 7 per cent, not the 30 per cent claimed online
The case against
- One litre of cane ethanol can embody 2,000 to 3,500 litres of water
- Grain ethanol cuts greenhouse gases by only about 20 to 50 per cent
- Maize competes with oilseeds for land, and Food Corporation of India rice goes to fuel while sugar prices rise
How the ethanol is made
- Ethanol is made by fermenting sugars, from sugarcane juice or molasses, or from the starch of maize and rice.
- A first generation biofuel of that kind competes for land, water and the plate, while second generation ethanol from crop stubble or bagasse does not.
- A blending mandate fixes the share the seller must blend, which creates demand a costlier fuel could not win on price.
- Blending began as a pilot in 2001, reached 10 per cent in 2021 to 2022 and 20 per cent in 2025 to 2026.
E20 in older engines
- Ethanol has a lower calorific value than petrol, so mileage falls by a few per cent.
- Ethanol carries its own oxygen into the cylinder, which leans out the mixture the engine was tuned for.
- A modern engine senses that and adjusts; a carburettor engine has nothing to sense it with, so it runs lean and hot and its rubber seals degrade.
- Vehicles built from April 2023 are E20 compatible; older two wheelers with carburettors are the exception, which is why an E10 option at the pump has been urged.
What changed
10 Jul 2026
- The government accepted that E20 can cut mileage by 3 to 5 per cent in some vehicles, because ethanol has a lower calorific value than petrol.
- It ruled out selling E10 or pure petrol alongside it, on grounds of logistics.
The Indian Express, 10 Jul 2026: Government defends E20 against a public backlash, and rules out going back to pure petrol or E10 (opens in a new tab) · The Indian Express, 9 Jul 2026: Government defends E20 against a public backlash, and rules out going back to pure petrol or E10 (opens in a new tab)
Show history (1 other update)
18 Aug 2026
- Maize is now the largest source of blending ethanol, ahead of Food Corporation rice and sugarcane juice.
- Government estimates put E20 above petrol in cost while crude is below about $70 a barrel.
- The Chief Economic Adviser would hold at E20 until the food against fuel trade off has been costed.
The Hindu, 18 Aug 2026: The E20 fuel debate (opens in a new tab)
UPSC has asked
- Prelims 2013: by-products of the sugar industry, bagasse and molasses
Further reading: Roadmap for ethanol blending in India 2020-25 (NITI Aayog)
Green hydrogen
Hydrogen fuel cell train
Copy link to Hydrogen fuel cell trainMains
India's first hydrogen train runs between Jind and Sonipat in Haryana on proton exchange membrane fuel cells.
- A proton exchange membrane fuel cell combines hydrogen with oxygen from the air to make electricity, and leaves only water vapour and heat.
What changed
19 Jul 2026BriefIndia's first hydrogen train began service between Jind and Sonipat in Haryana on 17 July. Hydrogen is made at Jind by electrolysis. The Hindu, 19 Jul 2026: How does India's newly launched train powered by hydrogen work? The Hindu ePaper, 19 July 2026 (opens in a new tab)