Hydrogen is a chemical element that is found in chemical compounds all over the world, for example in water. In its pure form (as an H2 molecule), it does not exist in nature. Pure hydrogen can be produced in several ways, but they are all energy consuming or polluting. Hydrogen is not an energy source, but an energy carrier. In other words, hydrogen is a way to store and transport energy in chemical form.
Currently, almost all hydrogen used is a product of natural gas (called gray hydrogen). Using grey hydrogen as a fuel (heat production) has no environmental advantage over using natural gas directly, because GHG is emitted when extracting H2 from natural gas.
Using electricity, hydrogen can be extracted from water in a process called electrolysis. If the electricity used comes from renewable sources (wind, solar, hydro), it is called green hydrogen.
The efficiency of electrolysis is currently around 70% - 80%.
Hydrogen is not easy to transport. The options are :
Hydrogen can be used in fuel cells, which can produce electrical energy with up to 70% efficiency.
Today, hydrogen is essential in some industrial processes, such as fertilizer production.
To replace grey hydrogen in industrial processes in the future, a large amount of green hydrogen will have to be produced. Possibly, green hydrogen will play a role in the electrification of trucks, heavy machinery, ships, trains or airplanes, which will further increase demand.
Where possible, direct electrification (e.g. in combination with batteries) is much more efficient and cheaper than using hydrogen.