Ammonia is produced by the reaction of hydrogen and nitrogen, dubbed the "Haber-Bosch process".

Ammonia is produced by the reaction of hydrogen and nitrogen, dubbed the "Haber-Bosch process". Depending on the feedstock that is being used, the two main hydrogen production processes used in ammonia production are:

• Steam/air reforming process. Feedstocks include natural gas or other light carbon fuels such as natural gas liquids, liquefied petroleum gas and naphtha.
• Partial oxidation process. Feedstocks include heavy oils and coal. 

The type of feedstock used to produce ammonia plays a significant role in the amount of energy used and CO₂ produced. The production of ammonia from natural gas is the least energy intensive, and production with coal, which is predominantly used in China, generally has the highest energy consumption and CO₂ emissions.  Globally about 72 percent of ammonia is produced from natural gas using the steam reforming process.⁴ Coal as feedstock for hydrogen production in ammonia plants is predominantly used in China and is generally characterized by high energy consumption and CO₂ emissions.³ Switching from coal or oil-based ammonia production to natural gas-based production will result in major energy and greenhouse gas emission savings. Other feedstocks for hydrogen production in ammonia plants include heavy fuel oil, naphtha, coke oven gas and refinery gas. On average, about one-third of the greenhouse gas emissions produced in natural gas-based production comes from fuel combustion and two-thirds from the use of natural gas used as feedstock. In coal-based ammonia plants, 25 percent of greenhouse gas emissions come from fuel burning and 75 percent from the use of coal as feedstock.³