Technology group Wärtsilä Corporation on Thursday (24 August) published an insight article explaining ammonia as a bunker fuel including operational considerations for ammonia.

The following are excerpts from the article:

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. 

• It doesn’t produce CO2, sulphur or particulate emissions when combusted.
• A supply chain and infrastructure already exist for other applications.
• It can be produced using renewable energy sources.
• It is relatively easy to store and handle onboard ships.

But is it the right solution for your vessel? Read on to find out.

Ammonia as a marine fuel 

Is ammonia a viable fuel? Can ammonia be used as fuel?

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.

What is ammonia’s fuel efficiency?

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.

What are the main challenges when using ammonia to fuel ships?

There are three main challenges when using ammonia to fuel ships:

• Ammonia is toxic, so the safety of the whole vessel must be considered, including the ventilation systems. 
• When using ammonia, ships will need larger fuel storage capacity compared to diesel or LNG because ammonia has a lower volumetric energy density than both of these fuels.
• Because ammonia is a new fuel, the regulatory landscape is still under development.

What are the advantages of ammonia as a marine fuel?

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. 

What are the disadvantages of ammonia as a marine fuel?

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. 

For a quick overview of the advantages and disadvantages of ammonia as a marine fuel, you can download a handy one-page cheat sheet: Future fuel 101 – Ammonia 

Ammonia marine fuel safety 

How can ammonia be used safely as a marine fuel?

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:

• Ammonia is highly toxic and can be dangerous if not handled properly.
• Ammonia requires specialised storage and handling equipment.
• Ammonia fuel systems must be designed with safety in mind.

Wärtsilä is collaborating closely with classification societies to identify protocols and technologies to ensure ammonia is safe to use as a maritime fuel.

What do I need to consider when adopting ammonia as marine fuel? 

As the shipping industry moves towards decarbonisation, ammonia is emerging as a promising alternative fuel. To transition, your engine needs to be designed to use ammonia and specific materials need to be used for the components that will be 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 what is needed to use ammonia as a fuel during the design phase. From a retrofit perspective, in order to safely bunker, handle and burn ammonia onboard, some of the existing vessel structures will have to be changed. 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 safely 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.

What will the ammonia fuel bunkering network look like?

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. 

Note: Wärtsilä’s full insight on ammonia as a marine fuel can be read here.

Photo credit: Wärtsilä
Published: 20 November, 2023