We are talking about NH3, also known as the chemical formula for ammonia, composed of one nitrogen and three hydrogen atoms.
While it is known to be used as a fertiliser and in other industrial applications, its potential as a fuel to decarbonise heavy and maritime transport is now being explored, along with methanol and hydrogen. This transition will require significant investments to modernise fleets and create the necessary infrastructure for the production and distribution of these new fuels.
If these challenges are overcome, we may be able to see first-hand the first ammonia-powered trucks, tractors and ships. Universities, companies and research institutions are currently working on the development of this technology, and some prototypes have already been produced.
Although still at an early stage, ammonia is arousing great curiosity because of its potential as a sustainable fuel. Its composition is carbon-free, which means that it does not emit CO2 during combustion, which is one of the main greenhouse gases.
However, the use of ammonia as a fuel in ships and trucks faces several hurdles that need to be overcome, according to a report by the classification society DNV. Firstly, the availability of ammonia needs to be ensured, given that 80 per cent of the world’s production is currently used as fertiliser. In addition, it is expected that production will need to double or even triple to meet the demand of heavy transport and the world fleet.
It is also important to note that ammonia has a low energy density compared to other fuels, which means that more NH3 needs to be transported to maintain a vessel’s range. This poses a challenge on ships, where it is crucial to carefully balance space, weight and volume to ensure the proper and safe operation of the vessel. One solution being considered is to blend it with other fuels obtained from sustainable processes.
Another major challenge lies in its manufacture. Currently, ammonia is produced from fossil fuels, but a way is being sought to generate green ammonia from renewable sources in a way that is truly sustainable and carbon-free. To do this, renewable energy will be used to provide the electricity needed to generate hydrogen by electrolysis of water and nitrogen from the atmosphere.
Green ammonia is emerging as a promising solution for the transition to more sustainable and carbon-free energy, and the race for its large-scale production is intensifying globally. Leading companies in the chemical industry, such as Yara, will build a sustainable ammonia production plant in Norway, which will have a capacity of 500,000 tonnes per year.
On the other hand, in Spain, measures are also being taken to promote the manufacture of this compound from renewable sources, which is planned to be carried out in different cities such as Ciudad Real, Huelva, Seville, etc.
Even if enough green ammonia can be produced in the near future, its use as a fuel will face other obstacles.
Its toxicity is its main disadvantage, according to a member of the Energy Transition Commission of the Spanish Association of Naval and Ocean Engineers (AINE). “Ammonia is currently used in the manufacture of fertilisers and as a refrigerant gas in some ships, which requires highly trained and experienced personnel. If its use is extended to ships and trucks, it would increase the number of people working with ammonia, increasing the likelihood of problems. Despite this, the disadvantage of toxicity is mitigated by the characteristic odour of ammonia, which makes it possible to detect leaks from a considerable distance”.
The biggest obstacle is regulation
Because ammonia toxicity can occur not only during engine operation, but also during fuel storage, refuelling and maintenance. Special detectors and protective equipment will be necessary.
In addition to this, it is a corrosive component, it cannot be in contact with copper, bronze, or other materials used in pipe joints…. This will mean changing these materials.
The International Maritime Organisation (IMO) is already working on a new regulation on its safe use by ships.
Ammonia burns at a much higher temperature than other fuels, reaching 630ºC compared to 210ºC for diesel, making it a slower burning fuel. Therefore, the most suitable transport will be sea transport, especially in large cargo ships, as ship engines turn at a much slower speed than lorries, which gives ammonia enough time to burn properly.
Another important point being studied is emissions control – ammonia combustion can generate emissions of nitrogen oxides, especially nitrous oxide, which is a greenhouse gas 300 times more potent than CO2.
“We think it should be possible to burn ammonia under the right conditions and with the right combustion chamber configuration, so that the nitrogen oxides can be reduced by the ammonia itself,” says Alzueta. The team is also investigating the use of small amounts of additives to lower the ignition temperature of ammonia to that of diesel.
First tests are underway
At the Vaasa laboratory, Wärtsilä is testing a newly built engine (W25) that will go on sale later this year. “One of the factors of ammonia is its flammability, which is quite slow. So it needs to be mixed with another fuel. In this case diesel. Ammonia itself has no carbon, but the mixture does. In the tests we are carrying out, we are trying to minimise the carbon content while maintaining the energetic power and optimising emissions and consumption,” explains Jesús Puelles.
They are also working on adapting engines already in operation on the ships, the first of which will be the W31, W32 and W34. “Our way of managing the new engines is that they are capable of using different fuels. In such a way that 95% of the parts are always the same and only the remaining 5% are changed depending on the type of fuel used,” says Puelles.
Man Energy Solution also plans to launch a two-stroke ammonia engine for container ships, and by 2025 to be able to offer an upgrade so that existing ships can run on ammonia.
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