Ammonia or NH3 (one nitrogen atom (N) and three hydrogen atoms (H) bonded together) is a colourless gas with a pungent, irritating odour found naturally in the environment, in soil, in water, and in the atmosphere. 

Ammonia has been used as an industrial chemical for over 100 years for refrigeration, in metal production and as fertiliser. It has an excellent safety record. 

While it is classed as a toxic gas, with the correct procedures in place, handling can be carried out safely making it ideal for an industrial setting.

Ammonia as a fuel has been somewhat overlooked due to its high auto-ignition temperature. The auto-ignition temperature of ammonia is 651°C; whereas the auto-ignition temperature of diesel fuel is generally around 210°C.

This said, ammonia has some distinct advantages over other carbon-free fuels, particularly hydrogen. Hydrogen is highly flammable, and explosion risk is high, whereas ammonia is very difficult to ignite making the risk of explosions or fire very low. 

Hydrogen is difficult to store; it either must be compressed to high pressure 700 bar or cooled to -253°C - both of which make hydrogen expensive.

Ammonia is much easier to store when liquid at -33°C (very similar properties to LPG) and can be stored at room temperature 25°C at 10 bar, so storage and transportation in thin wall steel cylinders is the norm. It can also be stored in large atmospheric bunkering by keeping it cool. 

The ease at which ammonia can be stored makes it affordable and is now widely being recognised as one of the best energy carriers.

Ammonia is produced in vast quantities using the Haber Bosch process, which involves using a catalyst, typically iron, under high pressure and moderate temperature. As this process is used for creating synthetic fertilisers, large scale green ammonia plants are already in production and more are being built or in the planning phase. 

By 2030, the predicted production levels are expected to be 40 million metric tons. 

To use ammonia to power an engine, it must use a high compression ratio and a direct injection. 

While ammonia engines rely on some fossil fuel acting as an ignition source for ammonia and run as a dual-fuel engine, it is possible to employ an ammonia disassociation or “cracker” to produce a hydrogen/nitrogen gas which is injected to the cylinders to form part of the fuel mix. This then acts as an accelerant to aid the burn of ammonia. 

A high efficiency propriety cracker design combined with high compression ratios can make the thermal engine very efficient. 

As this technology is fully scalable from 40 kW to 5 MW, it can easily replace most diesel engines.

While most ammonia engines use a fossil fuel to ignite the ammonia, running a dual-fuel engine that still produces CO2, it is possible to develop an engine that is powered by ammonia with truly “zero CO2”.