There are several methods to produce hydrogen, categorized by color codes based on feedstock and technology used. Green hydrogen uses electrolysis of water with green power to produce oxygen and hydrogen. Grey hydrogen involves natural gas steam reforming to produce syngas, while brown uses coal gasification and black uses fossil oil gasification. Blue hydrogen applies carbon capture to the production of syngas from fossil fuels. White hydrogen gasifies end-of-life plastics or biomass.

1. 05/04/2021
How Hydrogen is Produced?
Color
Code
Feedstock Core
Technology
Primary
products
H2-
separation
Green Pure water + green
power
Electrolysis O2 + H2 Membrane
Grey Natural Gas + steam NG-Steam
Reform
Syngas (H2 +
CO)
PSA
Brown Coal + oxidant Gasification Syngas (H2 +
CO)
PSA
Black Fossil Oil + oxidant Gasification Syngas (H2 +
CO)
PSA
Blue Grey, Brown or Black Gasification Syngas (H2 +
CO)
PSA +
Carbon
Capture
White EoL Plastics or
Biomass
Gasification Syngas (H2 +
CO)
PSA