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What is Hydrogen?

A colourless, odourless, highly flammable gas, the chemical element of atomic number 1.

Hydrogen is the simplest element, and the most abundant substance in the universe. When it is used in a fuel cell, it creates energy and the only by-product is water. If hydrogen is burnt, it generates energy in the form of heat, and water (and nitrous oxide if burnt in air). Creating hydrogen requires energy.

There are different colours of hydrogen:

• White hydrogen – Naturally occurring molecular hydrogen.
• Green hydrogen – Produced through water electrolysis powered by renewable energy sources such as hydro, wind, solar, etc. In this process, no carbon dioxide (CO2) and other GHGs (greenhouse gases) are released.
• Grey hydrogen – Produced from fossil fuels (except coal) through steam methane reforming (SMR). In this process, carbon dioxide (CO2) and other GHG are emitted.
• Blue hydrogen – Produced though the SMR process with the use of carbon capture and storage (CCS) technology to capture GHGs and store them underground.
• Cyan hydrogen – Produced by steam methanation of renewable natural gas with CCS.
• Turquoise hydrogen – Produced by methane pyrolysis (thermal splitting). In this process, the removed carbon is in the form of a solid.
• Black/Brown hydrogen – Produced by coal gasification. In this process, bituminous (black) or lignite (brown) coals are used. This method releases large amount of CO2, carbon monoxide (CO) and other GHGs.
• Purple hydrogen – Produced using nuclear power plants. In this chemo-thermal electrolysis process, nuclear power and heat are used to split water.
• Pink hydrogen – Produced through water electrolysis powered by nuclear energy.
• Yellow hydrogen – Produced through water electrolysis from the energy grid. The carbon emissions vary greatly depending upon the sources powering the grid.
• Red hydrogen – Produced through nuclear power thermal energy to power high-temperature catalytic water splitting.