Ammonia can be used as a fuel:

1. Combustion: Ammonia can be burned directly to produce heat or in an engine or a combustion turbine to produce energy directly. These need to be designed to allow for a much slower flame propagation velocity compared with other fuels. However the combustion of ammonia can produce nitrogen oxides (NOx), which are air pollutants.
2. Direct ammonia fuel cells: Ammonia can be directly fed into fuel cells to produce electricity. In this process, ammonia is oxidized at the anode of the fuel cell, generating electricity, water, and nitrogen as by-products.
3. Ammonia as a hydrogen carrier: Ammonia can also be used as a means of transporting hydrogen. Since ammonia has a higher energy density compared to liquid hydrogen, it can be more practical for storage and transportation. Ammonia can be synthesized using renewable energy sources, and then the hydrogen can be extracted when needed.

It can be stored and transported by pipe as a liquid at about 10 bar, but the infrastructure for handling, storing, and distributing ammonia as a fuel needs to be developed. It is toxic at higher concentrations but would not be a long term contaminant.