Steam methane reforming technique is used to obtain

Question

UnlockIAS · Accepted Answer

Correct — C, Grey Hydrogen. Steam methane reforming is the process by which most of the world's hydrogen is actually made. Methane from natural gas is reacted with steam over a nickel-alumina catalyst at around 800 to 900 degrees Celsius and 20 to 30 bar: CH4 + H2O gives CO + 3H2, a strongly endothermic reaction taking about 206 kilojoules per mole. The carbon monoxide is then put through the water-gas shift reaction with more steam, CO + H2O giving CO2 + H2, which is mildly exothermic and squeezes out extra hydrogen, so that overall one molecule of methane and two of water yield one of carbon dioxide and four of hydrogen. That carbon dioxide is the whole point of the colour label. Hydrogen made this way is called grey when the waste carbon dioxide is simply released to the atmosphere, and blue when the same carbon dioxide is captured and stored geologically. The stem names the technique and nothing else — no capture, no renewable input — so the product is grey hydrogen. The colour system is a taxonomy of production routes, not of the gas, which is chemically identical in every case: green means electrolysis of water driven by renewable electricity; grey means reforming natural gas and venting the carbon; blue means the same reforming with carbon capture and storage; brown means gasifying lignite, or brown coal, and black means the same from bituminous coal; turquoise means methane pyrolysis, which leaves the carbon behind as a solid; pink means electrolysis powered by nuclear electricity. Because blue is not offered here, the question is really a two-step test — recognise that steam methane reforming is a fossil-gas route, and then recognise that the absence of any carbon-capture clause makes it grey rather than blue. Option (d) fails for the simplest reason available: option (c) is right, so nothing is left for a None-of-the-above to catch.

Why the other options are wrong — (a) Green hydrogen is made by splitting water in an electrolyser using electricity from renewable sources, so its only by-product is oxygen and no fossil carbon is involved at any stage. Steam methane reforming starts from natural gas and ends by venting carbon dioxide — the opposite of the green route. The option is there because 'green hydrogen' is the phrase most candidates have met in the news.  (b) Brown hydrogen also comes from a fossil fuel, so it is the closest wrong answer, but from the wrong one. Brown hydrogen is produced by gasifying lignite — brown coal — and the same process using bituminous coal gives black hydrogen. The feedstock here is methane, a gas, not coal, and the process named is reforming, not gasification.  (d) Would be correct only if the product of steam methane reforming had no name among the three offered. It does: grey hydrogen is the standard term for reformed natural gas whose carbon dioxide is not captured. A None-of-the-above option earns the mark only when all three of the others can be shown to fail, and here one of them is exactly right.

Concept: Hydrogen carries no carbon in itself, so whether it helps the climate depends entirely on how it was made — which is why an industry that deals in a colourless gas has adopted a vocabulary of colours. The vast majority of hydrogen produced today is made from fossil fuels, chiefly by steam reforming natural gas, and it is used not as a fuel but as an industrial feedstock: to make ammonia for fertiliser, to make methanol, and in oil refineries for desulphurisation and hydrocracking. Decarbonising those existing uses is the first job for low-carbon hydrogen, before any question of hydrogen cars arises. India's policy vehicle is the National Green Hydrogen Mission, approved by the Union Cabinet on 4 January 2023 with an initial outlay of Rs 19,744 crore — of which Rs 17,490 crore is for the SIGHT programme covering electrolyser manufacturing and green hydrogen production incentives, Rs 1,466 crore for pilot projects and Rs 400 crore for research. Its 2030 targets are at least 5 million metric tonnes of green hydrogen production capacity a year, about 125 GW of associated renewable capacity, over Rs 8 lakh crore of investment, more than 6 lakh jobs and roughly 50 million tonnes of avoided greenhouse gas emissions a year.

State PCS 2025 Q141 — Science & Technology PYQ with Answer

State PCS 2025 Q141 — Science & Technology PYQ with Answer