Ammonia-air mixtures are flammable in a narrow zone of concentrations between 16% and 25%. The products of combustion from burning ammonia are predominately nitrogen and water. No CO2 or CO are produced as ammonia does not contain any carbon. Ammonia is a carrier of hydrogen however it is far easier to store, distribute and use than hydrogen.
Ammonia can be used as a fuel in most applications where hydrocarbons are currently used. These applications include internal combustion engines, gas turbines and boilers. Most piston engines will run very well on ammonia-air mixtures with some modifications to the fuel and ignition systems. Engines running on ammonia may produce NOx however in quantities , certainly no greater than those produced by an equivalent hydrocarbon fuelled engine. An engine running on ammonia can therefore be classified as producing zero carbon emissions.
Ammonia has been successfully used as a ground transport fuel dating as far back as the 1940’s where it was used to fuel public motor buses in Belgium. One of the more recent applications has been the conversion of a 2013 model popular sports car, to a dual fuel vehicle which runs on ammonia at low speeds.
The technology and means are rapidly being established to store, distribute and use ammonia as a zero emissions fuel for transport and energy systems. The challenge now is to develop processes to cost effectively manufacture ammonia using renewable energy. That is, to discontinue using hydrocarbons to obtain hydrogen for the ammonia manufacturing process, and develop other zero carbon emission systems to efficiently produce ammonia. When this is achieved, it will “close the loop” on the ammonia carbon free fuel cycle and pave the way for a clean energy future.
A concerted global research effort is required to develop ways of “closing the loop” on the ammonia carbon free fuel cycle.
Ammonia has been least exploited as a fuel however this is where it has the most potential in attaining humanity’s dream of a carbon free energy future.
The next instalment will discuss ammonia manufacture.