The fertiliser industry is essentially concerned with the provision of three major plant nutrients - nitrogen, phosphorus and potassium - in plant available forms. Most nitrogen fertilisers are derived from ammonia. Only very large sites include production of the whole range of fertilisers. Typically, an integrated site is focused on the production of nitrogen based fertilisers or phosphate fertilisers.

Ammonia (NH3) is synthesized from nitrogen and hydrogen. The most readily available source of nitrogen is atmospheric air. While hydrogen can be produced from various feedstocks, it is currently derived mostly from fossil fuels. Depending on the type of fossil fuel, two primary methods are used to produce hydrogen for ammonia production: steam reforming and partial oxidation (see Chemicals section for more details).

Globally, most ammonia production capacity still relies on the steam reforming process. The majority of ammonia is used as a nitrogen source in fertilizers, while the remaining share is utilized in various industrial applications, such as the manufacture of plastics. Ammonia is also used in environmental protection measures, such as the removal of NOₓ from flue gases.

Ammonia exists in two primary forms: anhydrous ammonia, which is pure ammonia without water content, and aqueous ammonia, also known as ammonium hydroxide, which is a solution of ammonia dissolved in water. Both are covered by the EU CBAM.

The stream of CO2 from the production of ammonia is of high purity and can be separated, captured and transferred elsewhere for other uses such as urea production.

Ammonia production via steam reforming involves converting natural gas (or biogas) into hydrogen (see Chemicals section for more details), which is then combined with nitrogen to synthesize ammonia via the Haber-Bosch process.

Ammonia production via partial oxidation involves converting heavy hydrocarbons, such as coal or heavy fuel oil, into synthesis gas (syngas), which is then processed to produce ammonia.

Nitric acid (HNO₃) is predominantly produced through the Ostwald process, which involves the catalytic oxidation of ammonia. In this process, ammonia is first oxidized in the presence of a platinum-rhodium catalyst to form nitric oxide (NO). The nitric oxide is then further oxidized to nitrogen dioxide (NO₂). Subsequently, nitrogen dioxide is absorbed in water within an absorption tower to yield nitric acid (HNO₃). This series of reactions is exothermic, allowing for the recovery of heat and power during the process.

The majority of the nitric acid produced is utilized in the manufacture of inorganic fertilizers, primarily through neutralization with ammonia to form ammonium nitrate. The production of nitric acid generate nitrous oxide (N₂O) emissions, which is a highly potent greenhouse gas (GHG).

Urea (CH₄N₂O) is synthesized by reacting ammonia (NH₃) with carbon dioxide (CO₂) at high pressure to form ammonium carbamate, which is then dehydrated to produce urea. Typically, the ammonia and CO₂ used in this process are sourced from on-site production facilities, often integrated within the same plant.

The production of nitrogen-containing mixed fertilizers, such as ammonium salts and NP, NK, and NPK formulations, encompasses a variety of operations. These processes include mixing, neutralization, and particle formation methods like granulation or prilling. Depending on the specific fertilizer formulation, these operations may involve solely physical mixing or incorporate chemical reactions to achieve the desired nutrient composition.

In the context of NPK fertilizers, which provide a balanced supply of nitrogen (N), phosphorus (P), and potassium (K), production methods can vary. One common approach is the nitrophosphate process (see graph below), also known as the Odda process, which involves acidifying phosphate rock with nitric acid to produce a mixture of phosphoric acid and calcium nitrate. This mixture is then further processed, often with the addition of ammonia and potassium sources, to produce NPK fertilizers.