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
All 6 articles shown; the 0 that changed from 1 to 30 September 2026 are marked.Show only these
Hydrogen from nuclear heat: the copper chlorine cycle
Copy link to Hydrogen from nuclear heat: the copper chlorine cyclePrelims
The copper chlorine cycle is a thermochemical cycle that splits water using heat rather than electricity.
- It is considered promising because it runs at relatively lower temperatures with higher thermodynamic efficiency.
- Using nuclear process heat avoids the fossil fuel use and emissions of conventional hydrogen production and extends nuclear energy to non electric uses.
- The Fast Breeder Test Reactor at the Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam, is India's only operating fast reactor research facility.
What changed
26 Jun 2026BriefThe Department of Atomic Energy inaugurated at Kalpakkam on 26 June a technology demonstrator of the Bhabha Atomic Research Centre's indigenous copper chlorine process using process heat from the Fast Breeder Test Reactor, described as the world's first such facility. PIB, 26 Jun 2026: DAE Inaugurates World's First Hydrogen Production Facility Based on Copper–Chlorine Thermochemical Cycle Using Nuclear Heat from Fast Breeder Test Reactor (opens in a new tab)
See also: The Prototype Fast Breeder Reactor
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
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)
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)
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)
Compressed biogas
Copy link to Compressed biogasPrelims and Mains
Compressed biogas is the gas of anaerobic digestion, in which bacteria break down wet organic matter without oxygen, stripped of its carbon dioxide and other impurities to leave almost pure methane.
- It is chemically what natural gas is, so it can be blended into the compressed natural gas (CNG) sold to vehicles and into the gas piped to homes.
- The feedstock is non-food material: crop residue, cattle dung, press mud from sugar mills and municipal organic waste.
- Crop residue otherwise burnt in the field becomes a feedstock with a buyer, which is the link to stubble burning.
What changed
13 Jun 2026BriefA Harohalli plant turns Bengaluru wet waste into compressed biogas, and in April its gas entered the GAIL pipeline for the first time. Mains: Biogas needs a sustained price signal, as solar had, to attract investment; India's target of 5,000 plants compares with Germany's 9,000. The Indian Express, 13 Jun 2026: 50 tonnes in, 1 tonne out: Bengaluru startup turns city garbage into green energy amid LPG crisis (opens in a new tab) · The Hindu, 3 Jun 2026: Can kitchen waste replace LPG? This Indian startup thinks so (opens in a new tab)
GOBARdhan
Copy link to GOBARdhanPrelims and Mains
LeadGOBARdhan becomes the National Circular Bioenergy SchemeAugust 2026
Why in news
The Cabinet on 6 August 2026 approved GOBARdhan as the National Circular Bioenergy Scheme, to run to 2035 to 2036. It brings the compressed biogas programmes of four ministries under one, and requires city gas distributors to blend compressed biogas into the gas they sell.
Background
- Biogas forms when organic waste decays without air; it is mostly methane and carbon dioxide.
- Compressed biogas (CBG) is biogas purified to a high methane content and compressed, so that it can be used like natural gas.
- GOBARdhan, Galvanizing Organic Bio Agro Resources Dhan, began in 2018 under the Swachh Bharat Mission (Grameen), to turn cattle dung and farm waste into biogas and manure.
- SATAT, Sustainable Alternative Towards Affordable Transportation, is the 2018 scheme under which oil companies buy CBG from private plants; more than 200 plants run under it.
What the scheme does
- It places all CBG programmes under the Ministry of Petroleum and Natural Gas.
- City gas distributors must blend CBG into compressed natural gas for vehicles and piped gas for homes, starting at 3 per cent and rising to 5 per cent from 2028 to 2029.
- An administered price is fixed for at least ten years, so that a plant is sure of its buyer and its revenue.
- It adds capital subsidies and pipeline support, and aims at an almost tenfold rise in CBG output.
Why it matters
- Energy security: every unit of CBG blended is natural gas that India does not import.
- Waste: the feedstocks are crop residue, cattle dung, press mud from sugar mills and municipal organic waste.
- Air: crop residue sold to a plant is residue that is not burnt in the field.
- Soil: the slurry left after digestion is an organic manure.
The hard part
- A gas made from waste is worth making only if somebody must buy it at a price that covers the plant; the blending mandate and the administered price answer that.
- The next constraint is feedstock: residue is available in a short window after harvest, and must be collected, stored and carried to the plant.
The way forward
- Build feedstock supply chains with farmer groups, with storage near the plants.
- Develop a market for the manure, which decides whether a plant earns enough.
- Link plants to city gas pipelines, so that the gas does not have to travel by road.
Prelims facts
- GOBARdhan began in 2018 under the Swachh Bharat Mission (Grameen).
- The scheme is now run by the Ministry of Petroleum and Natural Gas.
- The blending duty falls on city gas distributors, 3 per cent rising to 5 per cent.
- SATAT concerns compressed biogas, not ethanol.
GOBARdhan, Galvanizing Organic Bio Agro Resources Dhan, began in 2018 under the Swachh Bharat Mission (Grameen) as a programme for turning cattle dung and farm waste into biogas and manure, and supply was first sought through SATAT, Sustainable Alternative Towards Affordable Transportation, the 2018 scheme under which oil companies buy compressed biogas from private plants, which left more than 200 plants running. A gas made from waste is only worth making if somebody is obliged to buy it at a price that covers the plant, and the 2026 scheme arranges both: a blending mandate on city gas distributors and an administered price for at least ten years, under one ministry. Every unit blended is natural gas India does not import, which is the energy security argument.
What changed
7 Aug 2026LeadGOBARdhan becomes the National Circular Bioenergy Scheme
Green hydrogen
National Green Hydrogen Mission
Copy link to National Green Hydrogen MissionPrelims and Mains
The National Green Hydrogen Mission is the money and the architecture India has put behind making hydrogen from water instead of fossil gas.
- Green hydrogen matters because hydrogen is already an industrial raw material, made today from fossil gas.
- The Mission, approved in 2023 and run by the Ministry of New and Renewable Energy (MNRE), targets 5 million tonnes of green hydrogen a year by 2030.
- Electrolysis passes electricity through water to separate hydrogen from oxygen, and is the route the Mission's money is built around.
- SIGHT, Strategic Interventions for Green Hydrogen Transition, is the Mission's incentive arm, and pays separately for making electrolysers and for making hydrogen.
- Hydrogen production is awarded in modes, and Mode-2B is the route under which refineries are allotted capacity.
- Twelve pilot projects in road transport try both fuel cells and hydrogen internal combustion engines.
The Mission's value chain
Renewable power
Dedicated renewable capacity supplies the electricity
Electrolysers
Domestically made electrolysers split water, with incentives for manufacturing
Green hydrogen
Production capacity supported under the SIGHT incentives
Certification: The Green Hydrogen Certification Scheme certifies the hydrogen as green across the chain, through its portal launched in June 2026
Uses
Refineries, fertiliser through green ammonia, steel and mobility
What changed
17 Jun 2026
- The Ministry of New and Renewable Energy launched the Green Hydrogen Certification Portal of India on 17 June for certification and compliance under the Green Hydrogen Certification Scheme.
- Standards for green ammonia and green methanol are finalised, and 6.7 lakh tonnes a year of green ammonia is contracted for fertiliser plants.
Background reading: PIB, 29 Jul 2026: Centre Launches 12 Pilot Projects Under National Green Hydrogen Mission for Deployment of 70 Hydrogen-Powered Vehicles Across 21 Routes (opens in a new tab)
UPSC has asked
- Prelims 2026: how green hydrogen is produced and the Mission's 2030 target
Further reading: National Green Hydrogen Mission (MNRE)
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)