Executive Summary
Green ammonia (NH3) is emerging as one of the most discussed zero-carbon fuels for deep-sea shipping. With no carbon in the molecule, it offers the potential for near-zero CO2 emissions when produced from green hydrogen and low-carbon power. At the same time, its toxicity, NOx and N2O formation risks, and unfamiliarity pose serious safety and regulatory challenges. Engine OEMs have announced ammonia-capable two-stroke designs, and several pilots are planned for the late 2020s. At Energy Solutions, we benchmark green ammonia against methanol and VLSFO on cost, safety, and engine readiness, mapping what ports and shipowners must do to move from trials to scale.
- LHV energy content of ammonia (~18 MJ/kg, ~12.7 MJ/L) is significantly lower than fuel oil, implying 2–3x larger fuel volumes to deliver the same energy at similar engine efficiencies.
- Indicative 2026 green ammonia production costs sit in the 900–1,400 USD/t range for favourable projects, translating to 25–40 USD/GJ, substantially above typical VLSFO levels.
- Engine OEM roadmaps suggest commercial ammonia two-stroke engines in the late 2020s, but full-scale validation of combustion stability, NOx control, and N2O mitigation will take time.
- Ammonia toxicity demands new safety zones, ventilation, and leak detection systems on board and at ports, with crew training and emergency response protocols far more stringent than for conventional fuels.
- In abatement terms, green ammonia could deliver 70–95% lifecycle GHG reductions versus VLSFO, but abatement costs often land in the 200–400 USD/tCO2e range under mid-2020s assumptions.
What You'll Learn
- Ammonia Fuel Basics: Properties, Production, and Engine Concepts
- Benchmarks: Energy Density, Fuel Costs, and Engine Efficiency
- Safety Protocols: Toxicity, Leak Scenarios, and Crew Training
- Engine Readiness: OEM Roadmaps and Pilot Projects
- Economic Analysis: Abatement Costs vs Methanol and VLSFO
- Ports & Bunkering: Infrastructure and Regulatory Requirements
- Outlook to 2030/2035: Role of Ammonia in the Fuel Mix
- FAQ: Green Ammonia Safety, Emissions, and Bankability
Ammonia Fuel Basics: Properties, Production, and Engine Concepts
Ammonia is a colourless gas at ambient conditions, typically stored as a liquid under moderate pressure or refrigeration. It has been traded for decades as a fertiliser feedstock, with established safety standards in the chemical industry. For shipping, green ammonia is produced by combining nitrogen from air separation with green hydrogen from electrolysis via the Haber–Bosch process. Carbon intensity is therefore driven largely by the electricity mix and electrolyser efficiency.
In maritime applications, NH3 can be used in several ways:
- Direct combustion in two-stroke engines: Low-speed engines with modified injection and ignition systems burn ammonia, often with pilot fuel (e.g. diesel or methanol) to stabilise combustion.
- Fuel for solid oxide fuel cells (SOFCs): Ammonia is cracked to hydrogen and nitrogen upstream of the cell stack, enabling high electrical efficiency but at the cost of additional balance-of-plant.
- Hybrid systems: Combining combustion engines and fuel cells for redundancy and part-load efficiency optimisation.
Methodology Note
Energy Solutions benchmarks use public techno-economic assessments, OEM announcements, and internal models. Costs are expressed in 2025–2026 real USD, assuming green ammonia plant capacities of 0.5–1.5 million tonnes per year, renewable power costs of 30–60 USD/MWh, and two-stroke engine efficiencies similar to advanced oil-fuelled engines when fully optimised. Lifecycle emissions estimates include upstream power, H2 production, and potential N2O emissions where data is available.
Key Physical and Operational Properties of Ammonia vs VLSFO
| Property | VLSFO | Ammonia (NH3) |
|---|---|---|
| LHV energy content (MJ/kg) | 40–42 | 18–19 |
| LHV energy content (MJ/L) | 35–37 | 12–13 |
| Storage conditions | Ambient temperature, near-atmospheric pressure | Mild cryogenic or pressurised (~-33 °C at 1 bar or ~10 bar at ambient) |
| Flammability | Flammable hydrocarbon | Narrow flammability range; requires ignition assistance |
| Toxicity | Low acute toxicity | Highly toxic; strong odour; corrosive to eyes and respiratory tract |
Gravimetric and Volumetric Energy Density: VLSFO vs Ammonia
Source: Energy Solutions synthesis of typical VLSFO and NH3 properties.
Benchmarks: Energy Density, Fuel Costs, and Engine Efficiency
Ammonia’s energy density penalty means fuel volume and tank space requirements roughly double or triple compared with VLSFO for the same energy delivered. However, future ammonia engines are targeting thermal efficiencies comparable to, or slightly higher than, current oil-fuelled engines, partly offsetting the volumetric disadvantage.
Indicative Fuel Cost and Efficiency Benchmarks (Mid-2020s)
| Fuel | Midpoint Fuel Cost (USD/t) | Cost per Unit Energy (USD/GJ) | Relative Engine Efficiency | Lifecycle GHG Reduction vs VLSFO |
|---|---|---|---|---|
| VLSFO | 650 | ~18 | 1.0× | 0% |
| Green methanol (bio/e- mix) | 1,400 | ~35 | 0.98–1.02× | 60–90% |
| Green ammonia | 1,100 | ~30 | 0.95–1.05× (targeted) | 70–95% |
Stylised Fuel Cost per GJ: VLSFO, Methanol, and Ammonia
Source: Energy Solutions modelling; excludes carbon pricing and compliance costs.
Safety Protocols: Toxicity, Leak Scenarios, and Crew Training
Ammonia’s acute toxicity is the dominant concern for ship crews, port workers, and nearby communities. Even small leaks can create dangerous concentrations in confined spaces. Safety protocols therefore extend well beyond conventional bunker fuel handling.
- Leak detection and ventilation: Continuous gas detection, automatic shutdown systems, and forced ventilation in enclosed spaces carrying ammonia lines or equipment.
- Personal protective equipment (PPE): Full-face respirators, chemical-resistant clothing, and emergency eyewash and shower stations near potential exposure points.
- Escape and refuge: Clearly marked escape routes, safe refuge rooms with independent air supplies, and rehearsed evacuation drills.
- Training and drills: Regular crew and port staff training in ammonia properties, first aid, and incident response scenarios, including simulated leaks and spills.
Engine Readiness: OEM Roadmaps and Pilot Projects
Multiple engine manufacturers have announced ammonia-capable low-speed two-stroke designs, with test engines under development. Early deployments are expected in the second half of the 2020s, often paired with green corridor initiatives.
Stylised OEM Roadmap and Pilot Project Types (Indicative)
| Timeframe | Technology Milestone | Typical Vessel Types | Key Uncertainties |
|---|---|---|---|
| 2025–2027 | Test engines, retrofit pilots, small-scale fuel supply at select ports. | Tugs, offshore support vessels, small tankers and bulkers. | Combustion stability, pilot fuel ratios, NOx and N2O control. |
| 2028–2030 | First commercial ammonia-fuelled deep-sea vessels, limited green corridors. | Medium-sized bulkers, tankers, PCTCs. | Fuel availability, crew experience, insurance and classification requirements. |
| 2030–2035 | Wider adoption if early projects succeed and regulations stabilise. | Broader range of bulk, tanker, and possibly container segments. | Relative competitiveness vs methanol, e-fuels, and advanced biofuels. |
Indicative Timeline for Ammonia Engine Deployment
Source: Energy Solutions synthesis of OEM announcements and pilot project timelines.
Economic Analysis: Abatement Costs vs Methanol and VLSFO
When comparing ammonia to methanol and VLSFO, shipowners look at fuel cost per tonne of CO2e avoided, alongside capex and operational complexity.
Illustrative Abatement Cost Comparison (Deep-Sea Shipping, Mid-2020s)
| Fuel Option | Fuel Cost Premium vs VLSFO (USD/t fuel) | Lifecycle GHG Reduction vs VLSFO | Abatement Cost (USD/tCO2e) |
|---|---|---|---|
| Green methanol | 700–1,000 | 60–90% | ~120–250 |
| Green ammonia | 800–1,200 | 70–95% | ~150–320 |
Abatement Cost vs GHG Reduction: Methanol vs Ammonia
Source: Energy Solutions abatement cost modelling for representative bunker spreads.
Ports & Bunkering: Infrastructure and Regulatory Requirements
Adding ammonia bunkering capabilities to ports requires more than additive storage; it implies hazardous chemical handling zones with strict exclusion areas, ventilation, and separation from public areas.
Indicative Port Infrastructure Elements for Ammonia Bunkering
| Element | Requirements vs Conventional Fuel | Key Safety Considerations |
|---|---|---|
| Storage tanks | Cryogenic or pressurised ammonia tanks with double containment. | Corrosion, overpressure, leak detection, controlled venting. |
| Transfer systems | Dedicated pipelines and loading arms with emergency release couplings. | Potential jet releases, splash, and vapour clouds. |
| Safety and detection | Gas detection, water curtains, and deluge systems. | Protecting nearby workers and critical infrastructure. |
| Regulatory framework | Alignment with emerging IGF Code amendments and local chemical safety rules. | Multi-agency coordination between port, environmental, and emergency services. |
Stylised Port Ammonia Bunkering Investment Breakdown
Source: Energy Solutions estimates for a medium-sized port adding green ammonia bunkering capability.
Outlook to 2030/2035: Role of Ammonia in the Fuel Mix
Long-term shipping decarbonisation scenarios often assign ammonia a major share of zero-carbon fuel supply, particularly for bulk and tanker segments where volumetric penalties are manageable. However, real-world uptake will hinge on safety acceptance, fuel costs, and progress in methanol and e-fuels.
Stylised Fuel Mix Scenarios: Ammonia’s Share of Global Shipping Energy
| Scenario (2035) | VLSFO & Other Fossil (%) | Methanol (bio + e-) (%) | Ammonia (%) | Other Low-Carbon Fuels (%) |
|---|---|---|---|---|
| Conservative | 70–75 | 8–12 | 3–6 | 10–15 |
| Base case | 55–65 | 15–25 | 8–15 | 5–15 |
| Aggressive ammonia | 45–55 | 10–20 | 20–30 | 5–15 |
Indicative Ammonia Share in Global Bunker Demand to 2035
Source: Energy Solutions maritime decarbonisation scenarios; shares expressed in energy terms.
FAQ: Green Ammonia Safety, Emissions, and Bankability
How dangerous is ammonia compared with conventional marine fuels?
Ammonia is much more acutely toxic than fuel oil or marine diesel. Short-term exposure to high concentrations can be life threatening, and even smaller leaks can cause serious irritation and long-term health issues. However, its strong odour and existing industrial safety experience provide a basis for robust risk management if handled correctly.
Does burning ammonia create new climate risks from N2O?
If combustion and aftertreatment are poorly controlled, ammonia engines can emit nitrous oxide (N2O), a potent greenhouse gas. Engine developers are therefore focusing on combustion optimisation and catalyst systems to minimise N2O alongside NOx. Demonstrating reliably low N2O emissions is critical to achieving the advertised climate benefits.
How does green ammonia compare with green methanol in terms of infrastructure needs?
Green ammonia typically requires more specialised storage and transfer infrastructure than methanol, including pressurised or refrigerated tanks, stringent gas detection, and larger safety zones. Methanol can leverage existing liquid fuel and chemical handling experience more directly, which may make it easier for some ports to adopt in the near term.
Will ammonia become the dominant fuel for zero-carbon shipping?
Many long-term scenarios assign ammonia a large share of zero-carbon bunker demand, especially for bulkers and tankers. In practice, its role will depend on relative fuel costs, advances in engine and safety technology, and competition from methanol and e-fuels. A diversified fuel mix is more likely than a single dominant solution.
What do investors look for in green ammonia maritime projects?
Investors typically seek secure long-term offtake contracts, co-location with industrial ammonia or hydrogen demand, strong sponsors, and clear regulatory support. Projects that combine shipping demand with fertiliser or power markets can improve utilisation and reduce revenue risk.