Blue hydrogen
Hydrogen produced from natural gas by reforming, with most of the resulting CO2 captured and permanently stored.
Blue hydrogen uses the same chemistry as grey hydrogen but adds carbon capture and storage. Two process routes are used:
- Steam methane reforming (SMR) with capture: capturing only the concentrated process CO2 from the shift reactor gives roughly 55–60% capture; adding flue-gas capture from the reformer furnace raises it to about 85–90% at higher cost.
- Autothermal reforming (ATR): uses oxygen, so nearly all CO2 ends up in one high-pressure stream, enabling 93–97% capture; preferred for new large projects such as those planned in the UK, Norway and the US Gulf Coast.
Without capture, reforming emits about 9–10 kg CO2 per kg H2. With high capture, direct emissions fall to 0.5–1.5 kg, but upstream methane leakage is decisive: at 1.5% leakage and GWP100 it adds roughly 1–2 kg CO2e per kg, and at 3%+ blue hydrogen can approach grey on a 20-year basis (Howarth and Jacobson 2021 versus subsequent rebuttals assuming best-practice gas supply). Costs are typically USD 1.5–3/kg, depending on gas price and capture rate. Existing examples include Shell Quest in Canada and Air Products Port Arthur in Texas.
Related terms
All terms →- Grey hydrogen
Hydrogen made from natural gas by steam methane reforming without carbon capture; the dominant and cheapest production route today.
- Green hydrogen
Hydrogen produced by splitting water in an electrolyser powered by renewable electricity, with near-zero direct CO2 emissions.
- Carbon capture and storage (CCS)
Technologies that separate CO2 from flue gas or process streams, compress it, and inject it into deep geological formations for permanent storage.
- Methane leakage
Unintended release of methane from oil, gas and coal supply chains through leaks, venting and incomplete flaring, often expressed as a percentage of gas produced.
- Natural gas
A fossil fuel composed mainly of methane, used for power generation, industrial and residential heat, and as a chemical feedstock for hydrogen and ammonia.