Comparing the Energy Costs of Hydrogen, Ammonia, and Green Methanol
A practical analysis of alternative maritime fuels: energy density, delivered costs, and operational considerations for shipowners evaluating the transition to zero-emission vessels.
The transition to zero-emission shipping requires careful evaluation of alternative fuels. This analysis compares hydrogen, ammonia, and green methanol based on their energy content, production costs, and delivered energy prices—providing shipowners with actionable data for fleet planning decisions.
Fuel Properties at a Glance
Before diving into costs, understanding the fundamental energy characteristics of each fuel is essential. These properties directly impact storage requirements, range, and operational flexibility.
Hydrogen: The Baseline Energy Carrier
Hydrogen offers the highest gravimetric energy density at 33.3 kWh/kg (120 MJ/kg), making it attractive for weight-sensitive applications. However, storage form significantly impacts both cost and volumetric efficiency.
Cost Analysis by Storage Form
| Storage Form | H₂ Base Price | Effective Price/kg | Cost per kWh | Delivered Cost* |
|---|---|---|---|---|
| Compressed H₂ 350-700 bar |
€8/kg | €8.00 | €0.240 | €0.480 |
| €6/kg | €6.00 | €0.180 | €0.360 | |
| €4/kg | €4.00 | €0.120 | €0.240 | |
| Liquid H₂ -253°C cryogenic |
€8/kg | €10.00 | €0.300 | €0.601 |
| €6/kg | €7.50 | €0.225 | €0.450 | |
| €4/kg | €5.00 | €0.150 | €0.300 |
*Delivered cost accounts for 50% PEM fuel cell efficiency. Liquefaction adds ~25% to base hydrogen cost.
Modern PEM fuel cells achieve 50-60% electrical efficiency in marine applications. We use 50% as a conservative baseline. Combined heat and power systems can reach 80%+ total efficiency when waste heat is utilized.
Ammonia: A Practical Hydrogen Carrier
Ammonia (NH₃), produced via the Haber-Bosch process, offers an energy content of 5.17 kWh/kg (18.6 MJ/kg). Its key advantage: it stores hydrogen at 17.7% by weight in a form that’s liquid at moderate pressure (-33°C at atmospheric pressure, or ambient temperature at ~10 bar).
Production Economics
Each kilogram of ammonia requires approximately 0.177 kg of hydrogen feedstock. The table below shows minimum feedstock costs—actual production costs are 10-15% higher due to the energy-intensive Haber-Bosch process.
| H₂ Input Price | NH₃ Feedstock Cost | Cost per kWh | Delivered Cost* |
|---|---|---|---|
| €8/kg | €1.42/kg | €0.274 | €0.685 |
| €6/kg | €1.06/kg | €0.206 | €0.514 |
| €4/kg | €0.71/kg | €0.137 | €0.343 |
*Delivered cost assumes 40% efficiency for direct ammonia combustion in dual-fuel engines.
Direct combustion in dual-fuel engines achieves ~40% efficiency. Alternatively, ammonia can be “cracked” back to hydrogen and fed to fuel cells (50%+ efficiency), though this adds complexity and capital cost. Several projects, including Viking Vesta, are exploring ammonia-to-hydrogen cracking systems.
Green Methanol: Balancing Cost and Practicality
Green methanol (CH₃OH), synthesized from green hydrogen and captured CO₂, provides 5.53 kWh/kg (19.9 MJ/kg). Its liquid form at ambient conditions makes it the easiest to handle and store of the three fuels.
Production Economics
Methanol production requires 0.125 kg of hydrogen and 1.375 kg of CO₂ per kilogram of methanol. CO₂ costs vary significantly: €50-100/tonne for industrial capture, €200-400/tonne for direct air capture.
| H₂ Input Price | CO₂ Price | Methanol Cost | Cost per kWh | Delivered Cost* |
|---|---|---|---|---|
| €8/kg | €100/t | €1.14/kg | €0.206 | €0.515 |
| €6/kg | €100/t | €0.89/kg | €0.161 | €0.402 |
| €4/kg | €100/t | €0.64/kg | €0.116 | €0.289 |
*Delivered cost assumes 40% efficiency for methanol combustion in dual-fuel engines.
Delivered Energy Cost Comparison
Practical Considerations for Shipowners
Beyond energy costs, several operational factors should inform fuel selection:
| Factor | Hydrogen | Ammonia | Methanol |
|---|---|---|---|
| Volumetric Density | 0.8 MJ/L (CH₂ @ 700bar) 8.5 MJ/L (LH₂) |
12.7 MJ/L (liquid @ -33°C) |
15.8 MJ/L (liquid @ ambient) |
| Storage Complexity | High pressure or cryogenic tanks required | Moderate pressure refrigerated tanks | Standard fuel tanks |
| Safety Profile | Flammable, rapid dispersion if leaked | Toxic, requires ventilation systems | Toxic, flammable, similar to conventional fuels |
| Bunkering Infrastructure | Limited (expanding in Norway, NL, Germany) | Established for fertilizer industry | Growing rapidly (Maersk, others) |
| IMO/Class Approval | IGF Code provisions; projects approved case-by-case | Interim guidelines issued 2024 | IGF Code compliant |
| Engine/FC Availability | Fuel cells commercially available | Dual-fuel engines in development | Dual-fuel engines available (MAN, Wärtsilä) |
Key Takeaways
- Hydrogen offers the highest energy density by mass and best fuel cell efficiency, but storage complexity and infrastructure gaps currently limit applications to shorter routes and specialized vessels.
- Methanol emerges as the most cost-effective delivered energy at €4-6/kg H₂ prices, with practical advantages in storage, handling, and regulatory acceptance—explaining its adoption by major container lines.
- Ammonia provides a middle ground with established global logistics, but toxicity concerns and pending engine technology create near-term barriers.
- Green hydrogen prices are the dominant cost driver across all three fuels. Every €1/kg reduction in H₂ cost translates to 15-20% lower delivered energy costs.
- Total cost of ownership must include capital costs for storage, safety systems, and crew training—not just fuel price per kWh.
Sources & Methodology Notes
- Energy densities: Lower heating values (LHV) per IEA Global Hydrogen Review 2024
- Fuel cell efficiency: Based on PowerCell, Ballard, and Nedstack marine system specifications (50-55% typical)
- Liquefaction cost premium: 25% based on Linde and Air Liquide published data for large-scale plants
- Haber-Bosch hydrogen requirement: 0.177 kg H₂/kg NH₃ stoichiometric; process energy excluded
- Methanol synthesis: 0.125 kg H₂ + 1.375 kg CO₂ per kg CH₃OH (stoichiometric)
- Combustion efficiency: 40% thermal efficiency for modern dual-fuel marine engines per MAN ES and Wärtsilä
- IMO regulatory status: As of IMO MEPC 82 (December 2024)