Hydrogen is the lightest and most abundant element in the universe, making up about 75% of its elemental mass.
Hydrogen is also reactive and can combine with many other elements, such as oxygen, to form compounds. One of the most common compounds of hydrogen is water (H2O), which is formed when hydrogen reacts with oxygen.
Hydrogen can be generated from a range of chemical species including hydrocarbons, ammonia, water and biomass and a number of processes are available for its production including:
- thermo-chemical processes such as steam reforming of hydrocarbons, biomass gasification, biomass-derived liquid reforming or solar thermochemical reforming.
- electro-chemical processes using electrolysis (as proposed for the HyBont Bridgend green hydrogen production facility).
- direct solar water splitting.
- biological processes using bacteria and microalgae to produce hydrogen via either photosynthetic or fermentative processes.
Green hydrogen refers to hydrogen produced from renewable sources rather than fossil fuels. The definition provided within the EU Hydrogen Strategy for green hydrogen is:
“Hydrogen produced through the electrolysis of water (in an electrolyser, powered by electricity), and with the electricity stemming from renewable sources. The full life-cycle greenhouse gas emissions of the production of renewable hydrogen are close to zero. Renewable hydrogen may also be produced through the reforming of biogas (instead of natural gas) or biochemical conversion of biomass, if in compliance with sustainability requirements.”
In the energy sector, hydrogen is often used as a fuel. It can be burned in internal combustion engines or fuel cells to generate electricity, and it can also be used as a fuel for transportation, heating, and industrial processes. When used as a fuel, hydrogen combines with oxygen to produce heat, water and electricity.
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