Ammonia is the most important basic chemical for fertiliser production. Modern ammonia plants consist essentially of a hydrogen plant, a nitrogen plant and an ammonia synthesis plant. During ammonia synthesis, ammonia (NH3) is made from hydrogen (H2) and nitrogen (N2) molecules in a ratio of 3:1 at extremely high pressures of 250 to 300 bar and temperatures of 450 °C to 500 °C.
The nitrogen can be taken either from the air, or it is made available in a highly pure form by nitrogen production plants.
For "green ammonia", pure nitrogen and H2 produced from e.g. green electricity are used.