Hydrogen: Production route
Grey, blue or green: how the colours really differ
What this tab covers How it is made: the main production routes or, for product families, the main product types and technologies, compared on share of supply, inputs per tonne, plant scale, yield, co-products and unit cost.Hydrogen is made by breaking apart a hydrocarbon or water. Steam methane reforming of natural gas is the cheapest route almost everywhere gas is available. China relies on coal gasification. Refineries also get hydrogen as a by-product of naphtha reforming, and chlor-alkali plants vent or sell by-product hydrogen. Low-emissions routes either capture the CO2 from reforming (blue) or split water with renewable power (green). Electrolysis needs about 50-55 kWh per kg, so its cost is set by power price and electrolyser use.
Routes compared
| Route | Share of supply | Inputs per tonne | Typical scale | Yield | Co-products | Unit cost |
|---|---|---|---|---|---|---|
| Steam methane reforming (SMR) and autothermal reforming (ATR) | about two-thirds of world hydrogen (indicative, basis: IEA GHR 2025, 290 bcm of gas used) | about 0.15-0.17 MMBtu of gas per kg H2 including fuel (indicative) | refinery and ammonia SMRs typically 50-500 t H2 a day (indicative) | about 70-75% energy efficiency on LHV basis (indicative) | about 9-10 kg CO2 per kg H2, half of it as a concentrated stream that can be captured | about $1.0/kg at US gas of $3.3/MMBtu and about $2.1/kg in India on LNG (JMK Research 2025) |
| Coal gasification | about one-fifth of world hydrogen (indicative, basis: IEA GHR 2025, 90 Mtce of coal) | about 7-8 kg coal per kg H2 (indicative) | Chinese coal-chemical complexes of several hundred kt H2 a year (indicative) | about 55-60% energy efficiency (indicative) | about 20-25 kg CO2 per kg H2, slag, sulphur | about $1-2/kg with cheap domestic coal (indicative) |
| By-product hydrogen (naphtha reforming, chlor-alkali, steam cracking) | most of the remaining sixth (indicative) | not applicable: co-product | set by the host unit | not applicable | this is the by-product | near zero marginal cost; valued at fuel or SMR replacement value |
| Water electrolysis (alkaline, PEM, solid oxide) | under 1% (2 GW installed in 2024) | about 50-55 MWh electricity and 9-15 t water per t H2 (indicative) | largest projects 100 MW-2 GW; IOCL Panipat contract 10 kt a year | about 60-70% LHV efficiency (indicative) | 8 t oxygen per t H2 | India tenders $4.4-4.6/kg (2025); electrolyser installed cost $2,000-2,600/kW outside China, $600-1,200/kW in China (IEA 2024) |
| Reforming with carbon capture (blue hydrogen) | under 1% | as SMR plus power for capture and compression | world-scale ATR projects about 1 Mt ammonia a year, e.g. CF/JERA/Mitsui Blue Point | slightly lower than unabated SMR | captured CO2 for storage or EOR | about $0.5-1/kg above grey (indicative) |
How each route works
Steam methane reforming (SMR) and autothermal reforming (ATR)Methane and steam react over a nickel catalyst at about 850 C to give syngas, then a shift reactor converts CO to CO2 and more hydrogen. Pressure swing adsorption purifies it. Fuel gas heats the reformer, so about a third of the gas is burned rather than converted.
Cheapest and proven; high CO2 and exposed to gas price swings.
IEA GHR 2025; JMK Research (May 2025); efficiency and gas use indicative Coal gasificationCoal is gasified with oxygen and steam to syngas, cleaned of sulphur and shifted to hydrogen. Used mainly in China for ammonia, methanol and coal-to-chemicals. Needs a large air separation unit for oxygen.
Energy security for coal-rich countries; roughly double the CO2 of gas.
IEA GHR 2025 (coal use); intensity and cost indicative By-product hydrogen (naphtha reforming, chlor-alkali, steam cracking)Catalytic reformers that make high-octane petrol release hydrogen, which the refinery reuses in its hydrotreaters. Chlor-alkali cells make about 0.03 t of hydrogen per tonne of chlorine.
Cheap but cannot be scaled on its own.
IEA GHR (indicative) Water electrolysis (alkaline, PEM, solid oxide)Electricity splits water into hydrogen and oxygen. Alkaline cells are cheapest; PEM responds faster to variable solar and wind. Output cost depends on power price and hours of use.
Near-zero emissions with clean power; two to four times the cost of grey hydrogen.
IEA GHR 2025; JMK Research (May 2025); PTI via The Week (Sep 2025) Reforming with carbon capture (blue hydrogen)ATR or SMR plants capture the concentrated CO2 from the shift step and, with ATR, from flue gas too. Capture rates of 90%+ are claimed for new ATR designs.
Cheapest low-carbon route where gas and CO2 storage exist; upstream methane leaks remain.
CF Industries 2025 results; cost indicative Unit economics are indicative ranges from the sources named; costs move with feedstock and energy prices, plant size and region.