Production of hydrogen is currently dominated by industrial processes using fossil fuels. These methods produce large quantities of greenhouse gases, currently some 830 million tonnes of CO2 a year, or equivalent to the emissions of the UK and Indonesia combined (IEA).
This form of manufacture of hydrogen from fossil fuels where the produced CO2 is vented to the atmosphere is labelled “Brown Hydrogen”. In the rare current instances where the vented CO2 is captured in some way, it is labelled as “Blue Hydrogen”.
“Green Hydrogen” is also a manufactured product from the electrolysis of water using very large amounts of renewable energy and requires substantial development and scale to be commercially competitive.
Colours of hydrogen
Colours of hydrogen are used as codes for the different types of manufactured hydrogen.
Black or Brown hydrogen is produced by using coal where the CO2 emissions are released to the air.
Grey hydrogen is produced from natural gas where the associated emissions are released to the air, this is the most common industrial process for producing hydrogen.
Blue hydrogen is Grey hydrogen with the emissions captured using carbon capture and utilisation including underground storage (CCUS);
Green hydrogen is produced from electrolysis of water powered by renewable electricity and needs substantial scale to be commercially competitive.
Turquoise hydrogen is produced from natural gas broken down into hydrogen and solid carbon via pyrolysis. This process is at the experimental stage.
Pink hydrogen is generated through electrolysis of water by using electricity from a nuclear power plant.
Natural hydrogen (or Gold, White) is naturally occurring Hydrogen sourced from underground reservoirs.