Introduction to Ammonia As A Potential Marine Fuel

Ammonia (NH3) is emerging as a potential marine fuel due to its zero carbon dioxide emissions when combusted.
“Green Ammonia”, the environmentally friendly version, which is produced using renewable energy sources, is the sustainable alternative to conventional ammonia. This provides ship owners with a fuel option that could have no well-to-wake CO2 emissions, which will assist in meeting IMO’s 2050 emissions reduction targets.

Ammonia as a Maritime Fuel

Traditionally known for its use in agriculture and industrial sectors, Ammonia has emerged as a promising alternative marine fuel due to its potential to reduce greenhouse gas emissions and promote sustainability in shipping.

Advances in ammonia combustion technology and fuel cells are being developed to address issues of toxicity and low energy density, aiming to improve safety and efficiency. As the shipping industry seeks greener solutions, ammonia’s role as a sustainable fuel is increasingly being recognized.

Properties

Technical Specification/Details

Boiling point: With a boiling point of -33 °C, it is a gas at room temperature and requires to be compressed and cryogenically stored.

Density: It has a density as a liquid fuel of approximately 0.68 g/cm³ at -33 °C. In its gaseous form at standard temperature and pressure, it is 0.77 Kg/m³

Solubility: Ammonia is highly miscible meaning it will readily dissolve in seawater in case of a spill. However, it is harmful to aquatic life and its effects vary depending on its concentration, the water temperature, and the pH levels.

Flammability: It is not inherently flammable but its flammability range in air is 15% to 28% by volume, meaning it can form explosive mixtures with air within this range.

Toxicity: It is highly toxic and Corrosive in nature and requires specialized handling.

Energy Density: Ammonia has a lower energy density (approx. 3.5 kWh/kg) compared to Heavy fuel oil (HFO) (approx. 12.6 kWh/kg). This means we need to burn almost three times as much quantity of Ammonia compared to HFO to achieve the same energy output.

Energy/Performance Efficiency: While energy density is lower, Ammonia offers near-complete combustion, leading to potentially improved engine efficiency compared to HFO. Factors such as Storage and Fuel economy will be key as ammonia-fueled ships will require more frequent bunkering depending on voyage lengths.

Types of Ammonia

The several types of Ammonia based on its production methods and use cases are:

Conventional Ammonia: Produced through the Haber-Bosch process, which combines nitrogen and hydrogen derived primarily from natural gas. This type of ammonia is typically used in fertilizers and industrial applications and can be adapted for use as a marine fuel.

Green Ammonia: Produced using renewable energy sources. The process involves generating hydrogen through the electrolysis of water using renewable electricity and then synthesizing ammonia from this hydrogen and atmospheric nitrogen. Green ammonia aims to minimize the carbon footprint associated with its production and is considered a more sustainable option.

Blue Ammonia: Produced from natural gas, like conventional ammonia but with carbon capture and storage (CCS) technologies employed to reduce CO₂ emissions during production. Blue ammonia represents a transitional approach, aiming to lower the carbon intensity of ammonia production while transitioning to greener alternatives.

Grey Ammonia: Refers to ammonia produced from fossil fuels without carbon capture, leading to higher CO₂ emissions. It’s the traditional form of ammonia and is less environmentally friendly compared to green and blue ammonia.

Emission Profile

Conventional Ammonia is produced from Natural gas, resulting in significant CO2 emissions during the extraction and processing. With Green Ammonia the emissions can be exceptionally low if the entire production process is powered by renewable energy.

The GHG intensity of Conventional ammonia is about 1.8-2.2 Kg CO2/Ton of Ammonia produced. That value drops to 0.6-1.0 for Blue Ammonia and can be near Zero for Green Ammonia.

The emissions can vary depending on the Production process, Carbon capture and Utilization and consider the Life Cycle Assessment (Extraction, Production, Transportation, Storage, and combustion) of the fuel.

Technology Readiness for Fuel and Engine Conversions

While there are currently no ships in service using Ammonia as a fuel since ammonia-fueled engines are not yet commercially viable, there are 2-stroke and 4-stroke Engines under development.

Existing marine engines and fuel systems need significant modifications or replacements to handle ammonia’s unique properties. While ammonia doesn’t produce CO₂, it can create nitrogen oxides (NOₓ) during combustion. Advanced technologies or after-treatment systems, such as selective catalytic reduction (SCR), are required to manage NOₓ emissions effectively.

The Fortescue Green Pioneer started its journey towards becoming the world’s first ocean-going ammonia-powered vessel in 2022 when Fortescue successfully converted a four-stroke engine to run on ammonia, in combination with diesel, at its land-based testing facility in Perth, Western Australia.

In July 2024, Brooklyn-based Amogy and Osaka-based Yanmar announced a collaboration aimed at helping to decarbonize maritime fuel technology. They plan to develop power plants for ships that use Amogy’s advanced technology for cracking ammonia to produce hydrogen fuel for Yanmar’s hydrogen internal combustion engines.

Operational Considerations

Storage and Handling

Ammonia is stored in specialized pressurized tanks at a temperature lower than its boiling point of -33 °C. A double-walled, insulated tank design is required to maintain the required temperatures and prevent leaks.

Adequate ventilation and Gas absorption systems are crucial to disperse any accidental releases of ammonia gas, preventing the accumulation of toxic vapours.

Ammonia gas detectors and alarms should be installed onboard to provide early warning of leaks and to monitor air quality continuously.

General safety

Ammonia is a colourless gas with a characteristically pungent smell. It poses health risks if inhaled, ingested, or absorbed through the skin.

It is highly toxic, and exposure can cause severe respiratory issues, skin irritation and burns. Handling requires personal protective equipment (PPE) to protect workers from ammonia exposure, including gloves, goggles, and gas masks. The use of high-efficiency respirators with ammonia-specific filters protects against inhalation of ammonia vapours.

Regular drills should be conducted to prepare for potential ammonia leaks or spills, ensuring that staff are familiar with containment, neutralization (Acid is used to neutralize spills), and cleaning and evacuation procedures. Emergency response will include First aid in the form of eyewash and body showers.

Bunkering Infrastructure

As with LNG bunkering ships, the IGC Code would be applicable to anhydrous ammonia bunkering ships which are subject to the SOLAS convention.

Classification societies, Flag administrations, Port states, and Societies for Gas as a Marine Fuel have all been instrumental in providing guidelines, recommendations, technical expertise and processes associated with Ammonia operations.

Truck to Ship, Ship to Ship, and Terminal to Ship are the three bunkering options with the former offering better flexibility and the latter offering higher bunkering rates and volumes.

Special considerations at bunker stations include Segregation from other areas of the ship, Forced ventilation, Emergency shut down systems, Emergency release/Breakaway coupling, Quick connect coupling, Leakage detection, safeties for leakage, Grounding/Isolation flanges, Inerting and purging systems etc.

Availability and Costing

The global production of ammonia was 170 million tonnes in 2018, up from 126 million tonnes in 2000. Global production capacity has increased by 6% in 2023.

97% of the planned capacity increase is based on natural gas as the feedstock, and mainly in countries with cheap natural gas. 31% of global ammonia was produced in China, 10% in Russia, 8.9% in the US and 7.9% in India.

For comparison, the fuel consumption of all ships was estimated to be 200 million tonnes in 2020, which corresponds to roughly 500 million tonnes of ammonia on an energy basis. Since shipping fuel demand is also expected to increase further, the current production of ammonia can only cover a moderate fraction of the demand for marine fuels.

The production cost of renewable ammonia will largely depend on these major parameters :

• The price of renewable electricity (Solar/wind/hydro etc.).
• Infrastructure and capital expenditure.
• Electrolyzer technology for electrolysis and synthesis of Ammonia.

As per general estimates, the production cost of green ammonia is generally estimated to be between $500-$1,200 per ton. Technological advances and renewable energy affordability are set to decrease Ammonia prices to the $300-$700 range along with supportive government regulations and incentives.

Conclusion

As the maritime industry seeks greener solutions, Ammonia offers a promising path to cleaner marine fuels. Its success will rely on ongoing innovation and overcoming current limitations.

Embracing Ammonia as a marine fuel aligns with Azolla’s commitment to a sustainable future. By adopting greener innovative fuels, we not only ensure compliance with regulations but also contribute to preserving marine ecosystems for generations to come.

You might also like to read-

• Role of Seafarers in Maritime Decarbonization
• Why and How to Decarbonize the Marine Industry?
• Green Fuels For Ships and Their Challenges
• Introduction to Methanol as a Sustainable Fuel for Ships
• Simplifying the Energy Efficiency Existing Ship Index (EEXI)

About Author

Azolla is a leading provider of sustainable solutions that drive decarbonization in the maritime industry. With a firm conviction that maritime professionals are key agents of change, Azolla endeavours to educate and empower individuals to embrace sustainable practices and lead the industry towards a carbon-neutral future. The writing team comprises of:

Kiran Shet, Head of Azolla
Aditya Srivatsava, Manager – Energy Efficiency & Decarbonization
Manav Chidambaran – Decarbonisation Specialist
Jothieswaran – Senior Naval Architect