Hydrogen – is the universe's most abundant element. It contains almost three times as much energy as natural gas and can produce heat and power through fuel cells without emissions. Hydrogen is produced by separating it from other elements in water and fossil fuels. It has no carbon footprint if produced by electrolysis with renewable electricity, by steam-methane reforming, or if the carbon emissions are captured. It could significantly help on the journey to net zero as we reduce our reliance on fossil fuels.

Green, blue, grey, brown and black, yellow, pink, turquoise, yellow and white are colours assigned to this invisible gas depending on how it has been produced.

Green hydrogen
Is made via massive quantities of renewable electricity electrolysing water into its components of hydrogen and oxygen, No carbon dioxide is emitted in the process. Although an expensive production method, green hydrogen is expected to drop in price as it becomes more common.

Blue hydrogen
Is created from natural gas and a steam reforming process, This ‘low-carbon hydrogen’ produces some CO₂ emissions as a by-product, so carbon capture is utilised.

Grey hydrogen
Is the most common type of natural gas-based hydrogen, fundamentally the same as blue hydrogen but without the emissions capture.

Black and brown hydrogen
Uses fossil fuels (black or brown coal) to make hydrogen and is thus the most damaging to the environment.

Pink (purple, or red) hydrogen
Is generated through electrolysis powered by nuclear energy.

Turquoise hydrogen
Is a new, low-scale method hydrogen made using methane pyrolysis to produce hydrogen and solid carbon.

Yellow hydrogen
Is a new type of hydrogen made through electrolysis from solar power.

White hydrogen
Is a naturally occurring, geological hydrogen found in underground deposits and extracted through fracking. It is currently unexploited.

Sources
The hydrogen colour spectrum, Energy explained, National Grid
Hydrogen and the energy transition: one molecule to rule them all? Axa Investment Managers
Could hydrogen investment get us to net zero? RBC BlueBay Asset Management

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