Brown H₂
Coal
Natural gas
CCS
Renewables
Grid electricity
20 – 25
Hydrogen colours: carbon intensity (kgCO₂eq/kgH₂)
Coal gasification
Grey H₂
9.8 – 13
Reforming(SMR/ATR)
0.5 – 8.8
0 – 0.5
Electrolysis
0 – 50
Blue H₂
SMR: Steam methane reforming ATR: Autothermal reforming CCS: Carbon capture and storage
Green H₂