BPSC 70th CCE Re-exam Prelims General Studies · Question 141 of 142

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.

• (a)Green Hydrogen — 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 — 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)None of the above — 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.

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.

The colour taxonomy is a small table and it is worth writing out once, because state and national papers now test it every year and always by naming a process rather than a colour. Learn it as feedstock plus treatment: renewable electricity into water gives green; nuclear electricity into water gives pink; natural gas reformed and vented gives grey; natural gas reformed with capture gives blue; brown coal gasified gives brown, and black coal gasified gives black; methane pyrolysed to solid carbon gives turquoise. Then read any question of this type in two steps. Step one: is the feedstock fossil or water? Step two, only if fossil: is the carbon captured or released? Here the feedstock is methane and no capture is mentioned, so both steps land on grey. The commonest error is to see 'methane' and reach for brown, because brown sounds like the dirty option — but brown is specifically lignite, and the distinction between reforming a gas and gasifying a coal is exactly what these questions are built to test.

• Steam methane reforming: CH4 + H2O gives CO + 3H2, strongly endothermic at about 206 kJ/mol, run at roughly 800–900 °C and 20–30 bar over a nickel-alumina catalyst
• The water-gas shift reaction, CO + H2O giving CO2 + H2, follows and is mildly exothermic; the overall reaction is CH4 + 2H2O giving CO2 + 4H2
• Hydrogen from steam reforming is termed grey when the waste carbon dioxide is released to the atmosphere and blue when that carbon dioxide is captured and stored geologically
• Green hydrogen is electrolysis of water using renewable electricity; brown hydrogen is from gasified lignite and black hydrogen from bituminous coal; turquoise hydrogen is methane pyrolysis leaving solid carbon
• India's National Green Hydrogen Mission was approved on 4 January 2023 with an initial outlay of Rs 19,744 crore, including Rs 17,490 crore for the SIGHT programme
• Mission targets for 2030: at least 5 MMT a year of green hydrogen capacity, about 125 GW of added renewable capacity, over Rs 8 lakh crore of investment and nearly 50 MMT a year of avoided emissions

• Choosing brown because the process burns fossil fuel — brown hydrogen specifically means gasified lignite, not reformed natural gas
• Forgetting the blue category: reforming with carbon capture is blue, and only reforming without capture is grey
• Assuming most hydrogen today is green; the overwhelming majority is made from fossil fuels and used as industrial feedstock, not as a fuel

BPSC names the process and asks for the colour, a one-step recall that is only safe if the whole table has been learnt rather than the two colours that make the news. UPSC does not ask the taxonomy at all; it asks what green hydrogen can be used for and which industries it can decarbonise, so the same syllabus item is tested as application rather than as terminology.

• practice — not a real PYQ

  Hydrogen produced by steam methane reforming with the carbon dioxide captured and stored geologically is called

  • (a)Green hydrogen
  • (b)Blue hydrogen
  • (c)Grey hydrogen
  • (d)Turquoise hydrogen

  Answer(b) Blue hydrogen — the same reforming process as grey, distinguished only by carbon capture and storage; turquoise refers to methane pyrolysis, which leaves solid carbon.

• practice — not a real PYQ

  The National Green Hydrogen Mission targets a green hydrogen production capacity by 2030 of at least

  • (a)1 MMT per annum
  • (b)5 MMT per annum
  • (c)10 MMT per annum
  • (d)25 MMT per annum

  Answer(b) 5 MMT per annum — with an associated renewable capacity addition of about 125 GW, under a Mission approved on 4 January 2023 with an initial outlay of Rs 19,744 crore.