Chapter 1: Introduction#

1.1 Maritime decarbonisation and the positioning of ammonia fuel#

Transitions in marine propulsion throughout shipping history, such as the shifts from sail to steam and from steam to diesel, took decades or even centuries. The current energy transition differs because it is driven not only by technology and economics, but also by environmental concerns, policy, regulation and social pressure.

LR lists ammonia as one of the main fuels that may support future zero-CO₂-emission ships, for reasons including:

• Ammonia molecules contain no carbon.
• The world already has mature industrial production and shipping experience.
• Ammonia can be used as a hydrogen carrier.
• Compared with liquid hydrogen, it is easier to transport and store on a large scale.
• Engine, fuel supply systems and safety technologies are evolving rapidly.

The report states that global annual ammonia production is approximately 180 million tonnes, most of which is used directly to manufacture fertiliser. Approximately 20 million tonnes is traded by sea each year, so existing terminal, storage and handling experience can underpin a future marine-fuel supply chain.

1.2 Ammonia fundamentals#

Chemical formula#

N₂ + 3H₂ = 2NH₃

Basic properties#

• At normal temperature and pressure, it is a colourless, transparent gas.
• The smell is strong and pungent.
• It is highly soluble in water and is corrosive.
• May cause serious damage to eyes, throat and lungs.
• Ammonia vapour at room temperature is lighter than air; however, when pressurised liquid ammonia leaks and flashes, it may form cold, dense gas clouds that are heavier than air.

Existing uses and emissions#

• About 70% of ammonia is used in the fertiliser industry.
• More than half of existing production is concentrated in China, the United States, India and Russia.
• Existing processes mainly use:
  • Coal gasification: about 26%.
  • Natural gas steam methane reforming (SMR): approximately 73%.
• The report estimates that ammonia production emits approximately 450 million tonnes of CO₂ annually, accounting for approximately 1.3% of anthropogenic CO₂ emissions, and is the largest source of emissions in the chemical industry.

Demand forecast#

The report quotes IRENA forecasts:

• Global ammonia demand may increase from 183 million tonnes in 2020 to 688 million tonnes in 2050.
• Approximately 197 million tonnes may be attributable to marine-fuel demand.
• Approximately 127 million tonnes may be used as a hydrogen carrier in the chemical and industrial sectors.

1.3 Physical and combustion properties#

Differences in original text data: The report lists liquid ammonia density as 680 kg/m³ on page 6 and the energy density comparison table on page 7 lists it as 696 kg/m³. This article retains both and does not unify them on its own.

1.4 Energy density comparison#

Liquid ammonia has a lower gravimetric energy density than LNG and hydrogen, but a higher volumetric energy density than liquid hydrogen and high-pressure gaseous hydrogen. For the same energy content, it requires approximately 2.8–2.94 times the storage volume of MGO.

1.5 Key considerations for using ammonia as marine fuel#

Social acceptance#

• There are opportunities to reduce the environmental impact of the maritime industry.
• Actual emission reduction effects must be confirmed through lifecycle analysis.
• If social acceptance changes, stranded assets may develop.
• The impact of an accident may extend beyond the boundaries of the ship and port.
• Society's urgent need for emission reductions may also increase the pressure on safety decisions.
• Market lobbying can create a conflicting or confusing information environment.

Safe operation and infrastructure#

• Existing industrial and maritime liquid ammonia experience can be leveraged.
• Risks can in principle be reduced through design, control and monitoring.
• Toxic effects on people, waters and the environment must be assessed.
• The current marine bunkering infrastructure is insufficient.
• New training and capabilities are needed for seafarers, port, shipyard and shore personnel.
• The regulatory framework is still developing.

Scalability#

• Ammonia is better suited than liquid hydrogen for use as an energy carrier.
• There is already a basis for large-scale production, but it must shift to low-carbon processes.
• Upstream technology is relatively mature, while downstream marine technology is still developing.
• Ammonia cargo can be transported and used as fuel at the same time.
• There is potential to achieve near-zero GHG fuel supply at scale.
• It must still contend with competition from other industries and constraints on shipyard capacity and technical capability.

1.6 Ammonia-fuel readiness: TRL, IRL and CRL#

The LR Maritime Decarbonisation Hub assesses three readiness dimensions:

• TRL (Technology Readiness Level): technology readiness, levels 1–9.
• IRL (Investment Readiness Level): investment readiness, levels 1–6.
• CRL (Community Readiness Level): community/social readiness, levels 1–6.

The report’s overall judgment on green ammonia and blue ammonia is:

• Production, supply, shipboard storage and combustion technologies are advancing.
• Business conditions for investment are still generally insufficient.
• The level of social acceptance remains low because of ammonia’s toxicity and the potential consequences of accidents.
• Engine TRL should therefore not be assessed in isolation; the supply chain, ports, regulations, business case and public-safety framework must also be evaluated.

Chapter 2: Safety#

2.1 General safety and toxicity#

The study by the LR Maritime Decarbonisation Hub and the Mærsk Mc-Kinney Møller Center for Zero Carbon Shipping makes the following high-priority recommendations:

1. Lower storage temperature, to reduce ammonia fuel safety risks.
2. Separate the fuel preparation room into two or more spaces to separate equipment groups that may leak.
3. Limit, monitor and control who enters the ammonia equipment space and how long they remain there.
4. Arrange the ventilation outlet in a safe location and fully isolate it from areas accessible to crew members.
5. Install multiple ammonia detectors with different principles.

Human Factors Engineering#

Ship design and company safety management systems should incorporate:

• Ergonomics and equipment operability.
• New or revised work procedures.
• Communication and coordination requirements.
• Competencies and training requirements.
• Emergency response arrangements.
• Change management of maintenance and operating procedures.
• Personnel roles, responsibilities, organisation and interfaces with other organisations.

2.2 Health, fire and explosion hazards#

Health hazards#

Ammonia can irritate or burn:

• skin.
• Oral cavity.
• Throat.
• Lungs.
• Eye.

The degree of harm depends on:

• exposure concentration.
• exposure time.

Inhalation of high concentrations may seriously damage the lungs and cause death; skin contact with concentrated aqueous ammonia can cause severe chemical burns, and eye contact may cause irreversible damage.

Anhydrous ammonia#

• Liquefied ammonia that does not contain water can be called anhydrous ammonia.
• Ammonia and water are highly miscible and can form ammonium hydroxide solution.
• Aqueous ammonia may still form a toxic atmosphere and may be flammable under certain conditions.

Release cloud#

• Ammonia vapour at room temperature is lighter than air.
• Compressed liquid ammonia flashes and cools when released.
• The resulting aerosol/cloud may be heavier than air and spread along decks, walkways or low areas.

2.3 Hazardous-area classification#

Using IGF Code concepts, the report identifies:

Because ammonia is both toxic and flammable, the design must include a Toxic Area Plan in addition to the Hazardous Area Plan.

2.4 Material compatibility#

Metals not suitable for direct contact with ammonia#

The report states that the following materials should not be used in storage tanks, piping, valves, fittings and equipment that come into direct contact with ammonia:

• mercury.
• copper.
• copper alloys.
• zinc.

Deposition and clogging risk#

Under certain conditions, contact between ammonia, water and CO₂ may form:

• Ammonium carbonate.
• Ammonium bicarbonate.

These deposits may cause blockage, damage and deterioration of equipment, components and piping.

Stress corrosion cracking (SCC)#

SCC may occur in components that are subjected to both tensile stress and a corrosive medium.

Potentially affected materials include:

• Carbon steel in anhydrous ammonia environment.
• High-nickel steels.
• Copper and some copper alloys in aqueous-ammonia environments.

The design assessment must cover the:

• Bunkering system.
• Fuel containment system.
• Fuel supply system.
• Power generation/propulsion system.

IGC Code 17.12 permits the use of carbon steel provided that a small amount of moisture is maintained in the ammonia to reduce the risk of SCC.

Non-metallic materials#

Plastics, elastomers and sealing materials differ in their compatibility with ammonia. The manufacturer must confirm their suitability for the actual:

• temperature.
• pressure.
• Ammonia purity.
• Moisture content.
• service duration.

2.5 Maritime safety regulations#

The following reflects the regulatory position described in the original 2024 report.

The development of IMO regulations for ammonia fuel is divided into two paths:

1. Gas carriers using ammonia cargo as fuel.
2. Non-gas carriers bunkered specifically with ammonia fuel.

Gas carriers use ammonia cargo as fuel#

• At that time, IGC Code 16.9.2 prohibited the use of toxic cargoes as fuel, thus restricting the use of ammonia cargoes as fuel.
• CCC 9 has determined that this language impedes ammonia fuel development.
• The report noted that IMO was developing amendments to allow gas carriers carrying ammonia to use their cargo as fuel where an equivalent level of safety to that for natural gas is achieved.
• One possible difference between gas carriers and non-gas carriers is the extent to which double-wall piping is required:
  • Non-gas carriers may require more comprehensive double piping.
  • Gas carriers may require this only outside the cargo area.

Use of ammonia as fuel on non-gas carriers#

LR published rules for the use of ammonia as fuel on non-gas carriers in July 2023, adopting the alternative-design and risk-based approach permitted by the IGF Code.

Relevant approval frameworks include:

• SOLAS II-1/55.
• IGF Code.
• IMO MSC.1/Circ.1455, Guidelines for the approval of alternatives and equivalents as provided for in various IMO instruments.
• LR Risk-Based Certification (RBC) programme.

RBC can be used for:

• Novel designs.
• Alternative designs.
• Non-traditional fuel systems.
• SOLAS ships and some non-SOLAS projects.

2.6 Ammonia-fuel bunkering#

Ammonia can be delivered in the following forms:

• Fully refrigerated.
• Semi-refrigerated.
• Pressurised.

Key points in bunkering station design#

• The risk assessment must consider the “reasonably foreseeable worst-case release scenario”.
• A Toxic Area Plan must be prepared for the ship.
• An airlock may be required when entering a toxic zone from a non-toxic zone.
• Bunkering stations may be of open, semi-enclosed or enclosed design.
• Gastight separation must be maintained between enclosed or semi-enclosed bunkering stations and adjacent spaces.
• Contents collected in the drip tray must not be discharged directly overboard.
• The automatic shut-off valve must be capable of immediate closure and remote operation.
• The valve closing action must not cause dangerous instantaneous overpressure.

HAZID/QRA study findings#

Research conducted by LR for Yara Clean Ammonia Australia and Pilbara Ports found that ship-to-ship ammonia bunkering at the Dampier and Port Hedland anchorages could achieve acceptable risk levels under specified assumptions.

Recommendations include:

• Add overpressure protection.
• Add gas detectors.
• A compatibility assessment between the bunkering vessel and the receiving vessel.

Uncertainties include:

• Bunkering location.
• Actual design of the receiving vessel.
• New findings in compatibility assessment.
• Gaps in knowledge about ammonia.
• Toxicity dispersion model limits for ammonia leaks to water surfaces.

The report emphasises that the assumptions and risk results of this study apply only to the specific project; other ship types and ports still require case-by-case assessment.

2.7 Fuel quality and specifications#

Available anhydrous ammonia grades#

• Commercial grade: typically around 99.5%.
• Refrigeration grade.
• High-purity grade: up to approximately 99.995%.

The report considers that commercial-grade ammonia may be suitable for ammonia dual-fuel engines, but water, oil, oxygen, nitrogen, sulphur and particulates must still be controlled.

Moisture and SCC#

• Ammonia easily absorbs water and is difficult to remove once it enters.
• A small amount of moisture reduces the risk of SCC.
• The report lists preliminary ranges as 0.1–0.5 mass%.

Post-combustion emissions#

Poor-quality or incomplete combustion can cause:

• Unburned ammonia/ammonia slip (NH₃ slip).
• NOx.
• N₂O.

Preliminary MAN ES fuel specification#

Particulates may originate from:

• Ammonia production catalyst debris.
• Transportation and logistics processes.
• Tank or piping contaminants.

2.8 Example properties of commercial-grade ammonia#

The report quotes CF Industries specifications:

Chapter 3: Drivers for Ammonia Fuel Adoption#

3.1 EU regulations#

Shipping must take account of five principal legislative measures under the EU Fit for 55 package:

1. EU MRV revision.
2. EU ETS revision.
3. FuelEU Maritime.
4. Alternative Fuels Infrastructure Regulation (AFIR).
5. Renewable Energy Directive III (RED III).

EU ETS#

The original report stated that, from 1 January 2024, passenger and cargo ships of 5,000 GT and above calling at EEA ports would be included in the EU ETS.

Coverage:

• Intra-EEA voyages: 100% emissions.
• EEA in-port emissions: 100%.
• Voyages between EEA and third countries: 50%.

Covered greenhouse gases:

• CO₂ from 2024.
• CH₄ from 2026.
• N₂O from 2026.

Allowance-surrender phase-in:

FuelEU Maritime#

FuelEU Maritime requires a gradual reduction in the GHG intensity of energy used on board ships from 2025 onwards.

In addition, from 2030, container ships and passenger ships will face requirements relating to the use of on-shore power supply or zero-emission technologies at berth.

Ships must establish a separate FuelEU Monitoring Plan to record:

• Energy usage.
• Fuel type.
• Emission factors.
• Monitoring and calculation methods.

Pooling#

Pooling allows multiple ships to share compliance surpluses and deficits, potentially covering:

• Same fleet.
• Same company.
• Ship pools between different companies.

The aim is to encourage new construction of low-emission ships, rather than only small efficiency improvements to existing ships. As an example, the report notes that a ship using low-GHG fuel may reduce the risk of FuelEU penalties for the entire pool.

FuelEU ammonia emission factor#

The report states that FuelEU Maritime assigns e-ammonia an emission factor of 0.0186, but does not specify the units or conditions of application in that paragraph.

3.2 IMO GHG strategy and lifecycle analysis#

The original report quotes the 2023 IMO GHG Strategy:

• Achieve net-zero GHG emissions by or around 2050.
• Reduce total annual GHG emissions by at least 20%, striving for 30%, by 2030, compared with 2008.
• Reduce total annual GHG emissions by at least 70%, striving for 80%, by 2040, compared with 2008.
• Reduce the carbon intensity of international shipping by at least 40% by 2030, compared with 2008.

IMO has established guidelines for fuel lifecycle analysis to calculate:

• Well-to-Tank (WtT): Production and supply stage.
• Tank-to-Wake (TtW): Onboard use stage.
• Well-to-Wake (WtW): Full lifecycle.

3.3 Differences in the lifecycles of grey ammonia, blue ammonia and green ammonia#

Grey ammonia#

• Produce hydrogen from natural gas or coal.
• No effective carbon capture is taking place.
• CO₂ emissions are high during the production phase.
• The report considers it unsuitable as a low-carbon maritime fuel.

Blue ammonia#

• Hydrogen is usually produced from natural gas.
• CCS/CCUS is applied to emissions from hydrogen production and the Haber–Bosch process.
• Actual benefits depend on capture rates, upstream methane emissions, energy sources and regulatory default factors.
• The report considers that, under the IMO and FuelEU default factors applicable at the time, blue ammonia may not offer a significant WtW advantage.

Green ammonia/e-ammonia#

• Producing hydrogen through water electrolysis using renewable electricity.
• Nitrogen is obtained through air separation.
• Powering the Haber–Bosch process using renewable energy.
• Shipowners still need to obtain a verifiable and traceable supply of green ammonia.

Shipboard emissions still need to be considered#

Even if combustion does not directly produce CO₂, the following must still be accounted for:

• Pilot-fuel share.
• Emissions from pilot-fuel combustion.
• NH₃ slip.
• NOx.
• N₂O.

The report cites expert estimates that pilot fuel may account for at least approximately 5% and may increase to 15% at low engine loads.

3.4 Shipowner demand and market interest#

The growth of ammonia in the maritime market can be divided into:

1. Increased demand for maritime transport of ammonia as an energy carrier.
2. The demand for ammonia directly as a ship fuel increases.

Ammonia is more suitable for transoceanic transportation than hydrogen, so ammonia transport ships may also become candidate ship types that use cargo as fuel in the future.

3.5 Ammonia transport demand#

Market assumptions cited in the report include:

• Japan plans to use 30 million tonnes of fuel ammonia in 2050.
• The Netherlands and Germany have proposed large-scale ammonia cracking facilities to supply imported hydrogen needs.
• Research by the University of Manchester’s Tyndall Centre for Climate Change Research suggests that around 20 large ammonia carriers may need to be built each year by 2030.
• LR estimates that Japan may need about 130 VLACs in 2030 based on co-firing demand.

Existing fleet limitations#

• Most existing vessels are small or medium-sized combined LPG/ammonia carriers.
• If ammonia is not considered in the original design of a large VLGC, it may not be fully loaded with ammonia due to steel yield strength and structural design limitations.
• It may only be partially loaded, or the cargo handling system may need to be modified and the structure strengthened.
• Some terminals require details of the vessel’s last three cargoes (L3C). If ammonia has been carried recently, a terminal may decline the vessel for subsequent LPG loading because ammonia residues can remain in the steel structure for an extended period.

3.6 Marine fuel demand and Ammonia Ready#

As of the time of the original report, no commercial ships have officially entered service using ammonia fuel, but early orders have emerged, including:

• Two LPG/ammonia carriers from Exmar LPG.
• Newcastlemax bulk carrier range.
• Small container feeder ship.

IRENA predicts that by 2050 the maritime sector may consume 197 million tonnes of ammonia fuel.

Original reported statistics: Ammonia Ready vessels#

• In operation: approximately 60 vessels.
• Orders: approximately 213 vessels.
• Some 102 vessels are on order with three fuel options.
• The 24 Ammonia Ready container ships can also run on diesel or methanol.

Distribution according to ship type#

Newbuilding Ammonia Ready Design Portfolio#

3.7 Technical and economic factors#

Two main challenges:

1. How to allocate limited green energy to shipping.
2. How to build a verifiable green ammonia supply chain.

Green ammonia costs include:

• Green hydrogen production costs.
• Renewable electricity costs.
• Energy consumed by the Haber–Bosch process.
• Storage, terminals and logistics infrastructure.
• Certification and traceability costs.

The report cites a 2022 EMSA study estimating that the total cost of retrofitting a ship fitted with a 10–16 MW two-stroke engine for ammonia fuel is approximately US$10–13 million, although the actual cost depends on:

• Ship type and size.
• Original engine type.
• Number and scope of modifications.

3.8 Annual fuel-cost forecast#

Model assumptions:

• Low ammonia price: US$655/tonne.
• High ammonia price: US$1,200/tonne.
• Low carbon tax: US$100/tonne CO₂.
• High carbon tax: US$350/tonne CO₂.
• The model does not include the minimum 5% pilot-fuel consumption of dual-fuel engines.

Ways to reduce the cost gap#

• Bunker in regions offering favourable subsidies, such as under the U.S. IRA policy environment.
• Initially use blue ammonia, and then gradually switch to green ammonia.
• Contracts for Difference.
• Carbon offsets.
• FuelEU Pooling.
• Charterers share part of the cost of green fuel.

Chapter 4: Ammonia Production and Supply#

4.1 Conditions of supply#

Whether ammonia can be used as a marine fuel depends on:

• Whether sufficient near-zero- or net-zero-emission ammonia is available.
• Whether it can be obtained along major shipping routes and at major ports.
• Whether its unit energy cost is competitive.
• Whether sufficient renewable electricity and green hydrogen are available.

Existing ammonia used in fertiliser and chemical industries is mostly produced from natural gas and does not capture carbon, making it unsuitable as a low-carbon fuel from a lifecycle perspective.

Original reported production capacity data#

• Global existing ammonia production capacity: approximately 230 million tonnes/year.
• Low-carbon ammonia actually in operation at that time: about 6.5 million tonnes/year.
• Announced and operational low-carbon ammonia projects tracked by AEA: more than 245 million tonnes/year.
• Expected to come online in 2025: more than 24 million tonnes/year.
• Estimated in 2030: close to 100 million tonnes/year.
• Renewable ammonia accounts for more than 80% of projects tracked by AEA.

New production capacity is mostly distributed in:

• Australia.
• Middle East.
• Africa.
• North America.

4.2 Demand and production capacity forecast#

MPP and AEA scenarios:

• There could be 40–140 renewable-ammonia plants in 2030.
• Renewable ammonia production may reach 20 million tonnes/year in 2030.
• There could be about 1,000 plants in 2050.
• Renewable ammonia production may reach 830 million tonnes/year in 2050.

Ammonia demand range in 2050#

4.3 Representative low-carbon ammonia projects#

• Yara: Established a clean-ammonia business and is working with Azane Fuel Solutions on ammonia bunkering vessels and supply solutions.
• Mitsui＋CF Industries: Use existing capacity to produce blue and green ammonia and are planning blue-ammonia facilities on the U.S. Gulf Coast.
• Casale＋Clariant: Developing catalysts to improve blue-ammonia process efficiency.
• Saudi Aramco/SABIC: Establishing a blue ammonia export hub with Jafurah gas field and CCS.
• Woodside (Australia): Plan to use renewable hydrogen to produce ammonia for export.
• Grannus (USA): Developing a blue ammonia production process combining syngas and CCS.
• Meridian/Woodside/Mitsui (New Zealand): Southern Green Hydrogen Project, with a target annual production of 500,000 tonnes of green ammonia.
• Unigel (Brazil): Planned annual production of 10,000 tonnes of hydrogen and 60,000 tonnes of green ammonia.

4.4 Milestones for renewable ammonia#

Chapter 5: Technology Readiness#

5.1 Technology approvals and projects#

LR's involvement includes:

• Ship concept design.
• Ammonia-fuelled engine AiP.
• Fuel supply system AiP.
• Novel Technology Evaluation.
• HAZID, HAZOP and QRA.
• Risk-Based Certification.

Exmar 46,000 m³ MGC#

In September 2023, LR issued an AiP for Exmar’s 46,000 m³ ammonia-fuelled medium gas carrier:

• Ship design: HD Hyundai Mipo.
• Main engine: WinGD ammonia dual-fuel two-stroke engine.
• Ammonia fuel supply system: Wärtsilä Gas Solutions.

Amogy ammonia cracking power generation system#

In February 2024, LR issued a feasibility statement for the component testing plan of the Amogy ammonia-to-power system. The system cracks liquid ammonia into hydrogen, which is then used in fuel cells.

5.2 LR ammonia project list (2019–2023)#

5.3 Marine engines and modifications#

The main technical difficulties in ammonia combustion are:

• Poor ignition properties.
• Burns slowly.
• Stable combustion is difficult.
• Pilot fuel is required.
• A tendency to produce NOx, N₂O and NH₃ slip.

If conventional diesel or fuel oil is used as pilot fuel, the overall emissions-reduction benefit will be reduced; sustainable pilot fuel may therefore be required in the long term.

Two-stroke engines#

WinGD X-DF-A#

• The original report expected delivery in 2025.
• Orders secured for Exmar ammonia carriers and Bocimar 210,000 DWT bulk carriers.
• LR has issued an AiP for the concept.
• Uses ammonia injection with pilot fuel.
• The engine can meet IMO NOx Tier II.
• SCR is required to reach Tier III.

MAN Energy Solutions#

• Dedicated single-cylinder testing in Copenhagen.
• The original report suggested that the first model might be a 60 cm-bore engine.
• The modular design also supports existing engines to be converted to ammonia/diesel dual fuel.
• The test site is close to an urban area, and the safety of ammonia delivery by road tanker and the bunkering operation itself has affected the test schedule.

Four-stroke engines#

Wärtsilä 25#

• The report states that an ammonia version is commercially available.
• Based on the existing Wärtsilä 25 platform.
• Viridis Bulk Carriers has signed a letter of intent.
• Wärtsilä has also demonstrated an engine concept with about 70% ammonia co-firing.

5.4 Ammonia fuel storage and supply system#

A complete system usually includes:

1. Bunkering stations and fuel storage tanks.
2. Ammonia fuel supply system (FSS).
3. Fuel Valve Unit (FVU)/fuel valve train.
4. Ammonia piping system.
5. Vent system.
6. Ventilation system.
7. Nitrogen supply system.
8. Ammonia release mitigation system.

A critical element is the ammonia release mitigation system, which treats ammonia releases to a safe concentration rather than venting them directly to the atmosphere.

5.5 Storage tank type and configuration#

Ammonia is usually stored as a liquid at about -33°C.

Available geometries#

Design focus#

• Prevent mechanical damage caused by navigation and collision.
• Evaluate shock and sloshing loads at various liquid levels.
• Choose materials that are less susceptible to SCC.
• Independent tanks and membrane tanks other than Type C generally require a secondary barrier.
• All tank connections, flanges, valves and fittings should be located in the Tank Connection Space (TCS).
• Ammonia fuel lines require secondary containment or double-wall piping.
• Piping should be routed away from the ship’s side.
• Because ammonia is toxic, it must not be discharged directly to the atmosphere; vapour-return or treatment piping is required.

5.6 Onboard fuel supply system#

Typical equipment includes:

• Low-pressure pump.
• Flow meter.
• Heat exchanger.
• High-pressure pump.
• Duplex filter.
• Manual valve.
• Master Fuel Valve.
• Double Block and Bleed (DBB) valve.
• Two-way valve.
• Pressure-maintaining and purging valves.
• Remote control valve.
• Catch Tank.
• Purge Tank.
• Nitrogen supply.
• Ammonia vapour treatment system.

The typical high-pressure supply pressure reported is approximately 85 bar, although the actual value is determined by the engine manufacturer’s specifications.

FVU functions#

The FVU is usually arranged outside the engine room, and its main functions are to:

• Safely isolate ammonia supply.
• Execute block and bleed.
• Route return flow to the ammonia/nitrogen separation or treatment system.
• Initiate an emergency shutdown.

The shut-off valve must:

• Be capable of remote operation.
• Be capable of automatic operation.
• Be accessible or operable from outside the equipment space.

5.7 Nitrogen supply and purging#

Because ammonia cannot be discharged directly to the atmosphere, the fuel system must be equipped with a nitrogen system.

Before start-up#

• Perform a system tightness test.
• Confirm that there are no leaks in piping and equipment.

After shutdown or emergency#

• Purge the ammonia line with nitrogen.
• Direct ammonia and nitrogen into the purge tank or treatment system.
• Untreated ammonia must not be discharged directly into the engine room or atmosphere.

5.8 Exhaust emissions and after-treatment#

NOx#

Ammonia contains fuel-bound nitrogen, and its combustion may increase NOx emissions. Some ammonia engines may require SCR even for Tier II compliance; Tier III will generally require SCR.

Ammonia slip#

SCR systems use ammonia or urea as the reducing agent; therefore:

• Using ammonia fuel may reduce additional urea requirements.
• SCR can also assist in the disposal of some unburned ammonia.

N₂O#

• Atmospheric lifetime: approximately 114 years.
• 100-year global warming potential: 265.
• Emissions are related to engine type and combustion technology.
• If engine controls cannot reduce emissions to an acceptable level, a dedicated catalyst must be added.

5.9 Ammonia cracker and fuel cell#

Ammonia can be used as a hydrogen carrier and is cracked to produce hydrogen, which can then be used in fuel cells.

The report lists:

• ShipFC: Evaluating high-temperature ammonia fuel cells.
• Alma Clean Power: Fuel cell supplier.
• Fraunhofer IMM: Development of catalysts for the removal of pollutants and unburned ammonia.
• H2Site, Amogy: Advancing ammonia cracking and commercialisation.

5.10 LR Rules and class notations#

Appendix LR2 to LR’s Rules and Regulations for the Classification of Ships using Gases or other Low-flashpoint Fuels contains:

• Requirements for Ships Using Ammonia as Fuel.
• The Ammonia Ready notation.
• Ship design and configuration requirements.
• Bunkering requirements.
• Safety system.
• Control and monitoring systems.

Edition cited in the original report:

• Rules and Regulations for the Classification of Ships using Gases or other Low-flashpoint Fuels, July 2023.

Chapter 6: Summary#

LR’s overall conclusion on ammonia fuel can be summarized as:

1. Engine and ship technologies are progressing from concept development towards commercial orders and installation on ships.
2. The low-carbon ammonia supply chain is developing simultaneously, but supply volumes and prices remain uncertain.
3. The cost of low-carbon ammonia depends on renewable electricity, green hydrogen and CCS.
4. Lifecycle analysis will directly determine compliance value and investment feasibility.
5. Safety challenges are significant, particularly toxicity, leakage dispersion, material compatibility and human factors engineering.
6. HAZID, HAZOP, QRA, AiP and risk-based certification are indispensable tools for early-stage projects.
7. Ammonia could become an important carbon-free molecular fuel for deep-sea shipping, but successful adoption must address technology, investment, regulations, supply and social acceptance.

Chapter 7: Appendix#

7.1 Technology Readiness Level (TRL)#

7.2 Investment Readiness Level (IRL)#

7.3 Community Readiness Level (CRL)#

7.4 Colour classification of ammonia#