Wherever market analysts gather in dark corners to discuss the future of transportation, the conversation invariably turns to the choice of powertrain or fuel. Hybrid? Biofuel? Battery? Hydrogen? In the future it may be necessary to add ammonia to the list.
Ammonia – a colourless but distinctly pungent gas made of molecules that combine one atom of nitrogen with three of hydrogen – is, as those who remember school chemistry, commonly associated with fertiliser production. In fact, it’s one of the most commonly made industrial chemicals with a huge global production footprint and well-established supply chain and transportation network. In addition to fertiliser, ammonia is used to produce plastics, pharmaceuticals and many other products.
History And Use As A Fuel
Ammonia has a long history as a fuel. In the 19th century it was used to drive streetcars in New Orleans (amongst other locations). In these machines, liquid ammonia was allowed to evaporate at ambient temperature and drive an engine in an equivalent manner to a steam engine. Whilst actively deployed the technology was rapidly overtaken by both the first internal combustion engines and the electrification of streetcars.
More recently, it has been used as a fuel in internal combustion engines. During the second world war a shortage of fuel in Belgium lead to public buses being converted to run on ammonia and coal gas. It has also been trialed in passenger cars in the 1980s and in the early 2000s.
Roll-on to the current day, and there’s now momentum to expand the use of ammonia as a fuel in both marine and terrestrial applications and as an energy vector for renewable energy storage. The Ammonia Energy Association is an industry organization with a large number of major companies from energy production, renewables and transportation who are actively supporting and promoting the case for greater use of ammonia. To stress this point:
In early 2020, Wärtsilä Corporation announced that with Knutsen OAS Shipping AS and Repsol it will commence long term testing of ammonia as a fuel in a marine four stroke engine.
MAN Energy Solutions will, after a successful trial, bring a 2 stroke ammonia engine to market in 2024 for marine applications.
In 2019, Hydrofuel and TFX International converted two heavy duty diesel trucks to run on diesel.
How Does It Work?
There are a variety of approaches, but the basic principle is that ammonia (NH3) is combusted in a conventional internal combustion engine. There isn’t scope to review the full technical details of the technology here (a good description can be found here and here), but in essence minimal modification of existing internal combustion engines means that ammonia can be combusted with hydrogen (produced from the ammonia as a part of the engine) with the byproducts being nitrogen, water and NOx/NH3 as pollutants. Although the NOx and NH3 don’t contribute to global warming, their presence can contribute to poor air quality. There is, however, a technical route to minimizing the presence of these pollutants using selective catalytic reduction.
With regard to safety, we’ve already seen that the production, transportation and use of ammonia is well-established globally and there is a long history of it being used safely. With regard to its use as a fuel, there are papers that show its use is comparable to gasoline and that risk is, for example, transferred from flammability to toxicity.
Ammonia requires a large amount of energy to produce and, typically, natural gas or LPG as a feedstock. When considered as an alternative fuel to reduce vehicle emissions this production process is clearly problematic. However, there is a solution to this problem as well. Air Products, ACWA Power and NEOM have signed an agreement to fund the construction of a ‘green’ ammonia production facility in Saudi Arabia powered by renewable energy. This type of facility, if scaled globally, could produce both ammonia and hydrogen for transportation renewably.
Will ammonia gain major traction as a zero-emission fuel? Realistically, across all potential applications, it will probably be used in a small percentage of vehicles. Battery electric and/or hydrogen fuel cell technologies are better suited from a cost/efficiency perspective for light and medium-duty applications. For heavy-duty/intensive applications there will likely be a mix of fuels/powertrains, but there is much focus on hydrogen across multiple industries and we would see this being the most viable option – particularly for on and off-highway applications.
Marine is one area where we would expect to see reasonable traction for ammonia as a fuel. Not only are major marine suppliers trialing and investing in the technology, the high-power requirements and push to reduce emissions from long range vessels position it as an attractive solution. The cost and packaging required to implement ammonia, including the storage on the vessel, is more attractive than hydrogen or a battery electric solution. Marine vessels also have better access to ammonia than other vehicle types since they can easily relocate, globally, to make use of resources.
There will be other specific applications/countries where the use of ammonia could make sense – either because access is easier/cheaper than other fuel sources or because the location enhances the use of ammonia compared to other fuels (for example, a remote location where it may difficult to transport hydrogen or a port facility where ammonia is already being used for vessels).
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