Ammonia has emerged as a promising alternative as the shipping industry looks for more sustainable fuel options. This article explores the many sides of using ammonia as a marine fuel and provides insights on how to do it smart.
To meet the IMO’s target of net-zero greenhouse gas emissions by 2050, the shipping industry needs to move to cleaner fuels. There is no clear frontrunner among the several potential options, but ammonia offers some unique benefits that make it a leading contender.
But is it the right solution for your vessel? Read on to find out, or use these shortcuts to take you directly to the topics you’re keen to read more about:
Ammonia is a colourless gas with a powerful odour. It is commonly used in cleaning products, refrigeration systems and fertilisers. It has emerged as a promising alternative fuel for the maritime industry because it has significant potential to reduce greenhouse gas emissions.
Although ammonia has many benefits, it also has some drawbacks, such as its toxicity and flammability.
Nitrogen and hydrogen gases are combined under high pressure at a high temperature in the presence of a catalyst. This reaction produces ammonia gas.
Ammonia has traditionally been produced using natural gas or even coal as the energy source. Because this process produces significant carbon emissions, the result is called grey ammonia, or sometimes brown ammonia.
When carbon capture is added to the ammonia production process, it reduces the carbon emissions and results in blue ammonia.
Green ammonia is produced using renewable energy sources, such as wind or solar power. Using ammonia as a fuel will only reduce overall greenhouse gas emissions if it is green ammonia. There is growing interest in producing green ammonia fuel.
Ammonia releases no CO2 when combusted, so it has great potential to be a more sustainable fuel choice. But as far as overall well-to-wake emissions are concerned, only green ammonia will bring significant environmental benefits. In fact, green ammonia is completely carbon-free whether the resulting emissions are considered from tank-to-wake or from well-to-wake.
On the other hand, producing grey ammonia generates one third more carbon emissions from well to wake than heavy fuel oil.
In the future engines will be able to run on 100% ammonia and use biodiesel as pilot fuel, enabling a fully sustainable solution.
Ammonia is used in traditional selective catalytic reduction (SCR) systems to capture NOx emissions. Today the reagent is urea because it is safe and easy to handle, but in the future we will see ammonia used as the reagent, though probably initially backed up by urea.
How we handle emissions abatement in the future and the reagents we use in SCR systems will very much depend on the engine combustion concept that emerges as the frontrunner.
Catalysts for eliminating ammonia slip from the reagent in the SCR process are already used in projects in the US where strict emission limits apply. Such projects provide a very good starting point for developing catalyst setups that are optimised for maritime applications.
Ammonia is an attractive alternative to fossil fuels for the shipping industry. It has the potential to significantly reduce greenhouse gas emissions, but there are still challenges to overcome. These include the development of a reliable ammonia fuel bunkering network and the fact that ammonia engines need additional maintenance because of the fuel’s corrosive nature.
Ammonia can be used as a gaseous or liquid fuel. Engines can burn this fuel well with minor adaptations.
Handpicked related content: Want to know more about future fuels in shipping? Find out more about the options available.
When it comes to ammonia fuel efficiency, the bottom line is it has a lower volumetric efficiency and energy density than diesel. Ammonia engines also have a lower efficiency than traditional fossil fuel engines. In short, a ship that uses ammonia needs much higher fuel storage capacity. The volume and weight of the storage infrastructure required also has a significant impact on the vessel’s operating range.
There are three main challenges when using ammonia to fuel ships:
One of ammonia’s biggest advantages is that it doesn’t contain any molecular carbon, so when it’s combusted in an engine it produces no CO2 emissions. Adopting green ammonia as a maritime fuel is a great way to decarbonise shipping, helping to reduce the reliance on fossil fuels and move towards a more sustainable future.
Ammonia is abundant and can be produced using renewable energy sources such as wind and solar power. It is widely manufactured and traded, primarily for use in the production of fertilisers, and has the energy potential to be a viable marine fuel.
Fuel storage and delivery systems don’t need to be overly complex when ammonia is used in its liquid form. This reduces the operating costs.
Ammonia is already being used as fuel in power generation.
Because ammonia is highly toxic and corrosive it requires careful handling and storage. However, the risks can be mitigated with proper crew training and equipment such as protective gear and ventilation systems.
Ammonia doesn’t produce CO2 when combusted as fuel. The NOx emissions it produces can be handled with an abatement solution, and a wet scrubber system might be needed to manage potential ammonia gas releases. More investigation into these solutions, with the cooperation of classification societies, is needed.
One of the biggest unknowns with ammonia is how to handle potential N2O emissions. Catalysts are being developed for N2O – a potent greenhouse gas – to minimise N2O emissions and make ammonia a sustainable solution. For example, the Wärtsilä 25 ammonia solution with its optimised combustion and integrated aftertreatment has been designed to minimise all greenhouse gas emissions.
Handpicked related content:Ammonia is a promising alternative as the shipping industry looks for more sustainable fuel options to support its decarbonisation efforts. What’s more, modern multi-fuel engine technology makes it relatively straightforward to start using ammonia as fuel. When you want to learn more, download this white paper: Excited about ammonia as a marine fuel? 6 things you need to know”.
If you prefer a quick overview, you can download a handy one-page guide on ammonia as marine fuel: Ammonia – Alternative fuels quick guide
Ammonia has several safety issues related to toxicity, explosion risk and odours. Regulations are currently being developed to ensure ammonia can be used safely as a maritime fuel.
Three considerations are important to remember when it comes to ammonia fuel safety:
How to deal safely with ammonia on board ships? Get the insights now and be prepared for the future: download this safety essentials eGuide packed with expert advice. From crew protection and leak detection to tank conversion and fire suppression, this guide covers what you need to know about using ammonia as marine fuel.
If you can smell ammonia, it means there is a leak. Depending on the concentration, it can also mean there is a health risk.
At low levels, ammonia can cause eye, nose and throat irritation. At high levels, it can cause more serious health problems. It is important to evacuate the area immediately if there is a leak and seek medical attention if you experience any symptoms.
Ammonia presents an explosion risk when its concentration in air reaches 15–28 vol.%.
The risk of ammonia toxicity has been defined according to acute exposure guideline levels (AEGLs).
The following table shows the ammonia AEGLs for five exposure periods.
Guideline* | 10 min | 30 min | 1 hour | 4 hours | 8 hours |
AEGL-1 | 30 ppm | 30 ppm | 30 ppm | 30 ppm | 30 ppm |
AEGL-2 | 220 ppm | 220 ppm | 160 ppm | 110 ppm | 110 ppm |
AEGL-3 | 2,700 ppm | 1,600 ppm | 1,100 ppm | 550 ppm | 390 ppm |
Regulatory frameworks for the development of ammonia as a marine fuel are still being developed. Collaboration with ship owners and operators is critical to give them confidence in the solutions being developed.
There isn’t yet much ammonia available for shipping as there is strong competition for ammonia as a fuel. The shipping industry is competing with the fertiliser and energy industries, and ramping up production takes time. Building and commissioning an ammonia plant can take anywhere from four to six years. However, more than 200 low-carbon ammonia facilities are currently being planned globally.
Currently, ammonia is not widely available for marine fuel use. The shipping industry is competing with fertiliser and energy sectors for supply, and scaling up production takes time. Building and commissioning an ammonia plant can take anywhere from four to six years, but momentum is growing: more than 200 low-carbon ammonia facilities are being planned globally.
How does ammonia fit into the broader fuel transition? What actions are needed to make sustainable shipping a reality by 2050?
Wärtsilä’s report Sustainable fuels for shipping by 2050 – the 3 key elements of success offers essential insights. It outlines what policymakers, industry players, and individual operators can do today to accelerate progress. Download the report to explore the roadmap to future fuels and the practical steps needed to navigate the transition with confidence.
As the industry explores cleaner alternatives, ammonia is becoming a practical reality. In a significant step forward, Wärtsilä introduced the marine sector’s first commercially available 4-stroke engine-based solution for ammonia fuel in November 2023. It is now available as part of the Wärtsilä 25 engine platform.
In addition to the Wärtsilä 25 engine platform, Wärtsilä’s solution for ammonia fuel includes the:
The solution also includes:
The Wärtsilä solution for ammonia fuel has been designed to ensure smooth and safe adoption of ammonia as a new fuel.
Working with a single manufacturer to design, integrate and supply the necessary components and systems makes for a safer solution and more efficient process.
 | Learn more about the Wärtsilä ammonia solution and how significant and immediate the reduction of emissions can be when running on sustainable ammonia. Access Wärtsilä Ammonia Lounge |
To move to ammonia-based operations your vessel needs to be designed to use ammonia. It might also be possible to retrofit an existing vessel, but there may be challenges to find space for equipment such as ammonia tanks. The fuel gas supply system needs to be designed for ammonia, and this includes a lot of different components.
You will also need an ammonia fuel engine, either one specifically developed for ammonia use or a retrofitted engine that can run on ammonia. A fuel-flexible and easily upgradable engine like the Wärtsilä 25 will be beneficial if you are considering running on ammonia in the future.
Your vessel’s aftertreatment system needs to be adapted according to the fuel it is using. Depending on whether your engines will be running on liquid or gaseous ammonia, you may also require some additional equipment such as a high-pressure room for the pumps if a high-pressure system is used to inject the ammonia fuel into the engine.
As the shipping industry moves toward decarbonisation, ammonia is emerging as a promising alternative fuel. But adopting it is not just a technical shift: it requires a holistic approach to ensure safe and compliant operations.
Your engine must be designed or adapted to run on ammonia, and specific materials must be used for components exposed to the fuel. Using ammonia as marine fuel also requires significant changes in the engine room and the fuel-handling system.
When building a new vessel, it is critical to consider in the design phase what is needed to use ammonia as fuel. From a retrofit perspective, some of the existing vessel structures must be changed to be able to safely bunker, handle and burn ammonia onboard. New structures will need to be designed, assembled and built to create the necessary space to store ammonia onboard and transfer it to the converted engines.
Auxiliary systems will need to be arranged to guarantee safety levels required by applicable rules and regulations. New auxiliary systems may also be needed, for example a drain system, bilge system, nitrogen system and ventilation system.
Equally important is preparing your people. Switching to a new marine fuel like ammonia is more than a technical upgrade: it is a people process too. From safety protocols to operational know-how, onboarding your crew and onshore staff is critical for a smooth and safe transition. Explore the top five challenges of onboarding for new fuels and how to overcome them.
Because ammonia has the potential to be carbon free from production to combustion, it has a lot of promise as a future fuel, especially for newbuild vessels. However, the additional space required to store and handle ammonia may mean that it is not a viable retrofit option for smaller vessels like tugs and fishing vessels.
Ammonia has already been trialled in fuel-cell solutions and in four-stroke ammonia engines. Whether ammonia becomes the dominant fuel of the future will depend on numerous factors, including technological advances, regulatory support and fuel supply investments. Zero-carbon fuels such as green ammonia will play a big role in making maritime transportation more sustainable.
The availability of ammonia as marine fuel, especially green ammonia, will be essential for reaching the marine industry’s decarbonisation targets. We are starting to see more discussions and investment decisions about an ammonia fuel bunkering network. This will scale up as the market starts to adopt ammonia.
Today, the demand for ammonia is mainly driven by fertiliser consumption, but the demand from the marine industry will start to increase as more vessels run on ammonia. DNV predicts ammonia use in shipping will be 170 PJ (1% of the shipping fuel mix) in 2030, 1,900 PJ (13% of the fuel mix) in 2040, and 5,000 PJ (36% of the fuel mix) in 2050.
The ammonia bunkering system can be fixed or mobile. Fixed bunkering involves stationary infrastructure at ports or fuelling stations, while mobile systems use transportable tanks. Ammonia can be stored as a liquid or a gas depending on the temperature or pressure.
Safety measures and environmental considerations play a critical role in the deployment of bunkering systems.
Curious about how to get started with ammonia as marine fuel? Download our white paper to uncover the six most important things you need to know. From why ammonia is gaining momentum to practical steps for adoption, this guide is packed with insights to help you make informed decisions about this promising alternative fuel. Start your journey toward cleaner shipping today.
Ammonia is a promising alternative fuel that can help the shipping industry meet decarbonisation targets. Only green ammonia, when produced using renewable energy offers well-to-wake carbon neutrality.
Ammonia does come with challenges, including toxicity, lower energy density, and the need for specialised handling and safety systems.
Regulations and infrastructure are evolving, but global momentum is building, with hundreds of ammonia projects in development.
Adopting ammonia as marine fuel may not be simple, but with the right knowledge, preparation, and safety measures, the transition can be made smoother.
Sources:
Wärtsilä Technical Journal, Vol. 2, 2021
International Maritime Organization (IMO) guidelines on the use of ammonia as marine fuel
This article answering frequently asked questions about ammonia as marine fuel first appeared as a Wärtsilä Insights article.
Most of this article has been written by humans, though parts of it have been created with the help of AI.
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