Case study: Ammonia as shipping fuel & hydrogen carrier — a city or utility pilot and the results so far

Japan's Ministry of Land, Infrastructure, Transport and Tourism (MLIT), in partnership with NYK Line, IHI Corporation, and the Port of Singapore Authority (PSA), launched one of Asia-Pacific's most ambitious ammonia-fueled shipping pilots in 2023: the Green Corridor Ammonia Shipping Initiative (GCASI). As of early 2026, the initiative has completed over 40 ammonia-fueled voyages along the Singapore-to-Yokohama trade route, logged more than 180,000 nautical miles, and demonstrated a 92% reduction in tank-to-wake CO2 emissions compared to conventional heavy fuel oil (HFO) operations on the same route (NYK Line, 2025). The pilot has drawn $740 million in combined public and private funding and positioned the Japan-Singapore corridor as the world's first operational green ammonia bunkering route for deep-sea shipping.

Why It Matters

International shipping accounts for approximately 2.9% of global greenhouse gas emissions, producing roughly 1.06 billion metric tons of CO2 equivalent annually according to the International Maritime Organization's Fourth Greenhouse Gas Study. Unlike road transport, where battery electrification offers a clear decarbonization pathway, deep-sea vessels require energy-dense fuels capable of powering voyages spanning thousands of nautical miles. Ammonia, with an energy density of 12.7 MJ/L and the ability to be produced from renewable electricity via green hydrogen synthesis, has emerged as one of the leading candidates for zero-carbon maritime fuel.

The regulatory pressure is intensifying. The IMO's 2023 revised GHG strategy commits to net-zero emissions from international shipping by or around 2050, with an intermediate target of at least 20% reduction by 2030 using zero or near-zero GHG fuels. The EU's FuelEU Maritime regulation, effective January 2025, imposes a 2% greenhouse gas intensity reduction on ships calling at European ports, escalating to 80% by 2050. Japan's Green Growth Strategy designates ammonia as a strategic fuel and targets 3 million metric tons of annual ammonia consumption by 2030, with 30 million metric tons by 2050. For shipping executives, port authorities, and energy procurement leaders, ammonia is no longer a speculative alternative but an operational imperative with regulatory deadlines attached.

Key Concepts

Understanding the GCASI pilot requires familiarity with several technical and regulatory concepts that shape ammonia fuel deployment in maritime applications.

Green ammonia refers to ammonia (NH3) synthesized using hydrogen produced via water electrolysis powered by renewable electricity, then combined with nitrogen captured from ambient air through the Haber-Bosch process. Unlike conventional "grey" ammonia produced from natural gas, green ammonia carries near-zero lifecycle carbon emissions. Current production costs range from $600 to $900 per metric ton, compared to $250 to $350 per metric ton for grey ammonia (International Renewable Energy Agency, 2025).

Ammonia-ready engines are dual-fuel marine engines designed to combust ammonia alongside a pilot fuel, typically marine diesel oil (MDO) at 5 to 15% of total energy input, to ensure stable ignition. Pure ammonia combustion remains technically challenging due to its low flame speed and high ignition temperature. IHI and MAN Energy Solutions have developed two-stroke engines that achieve 85 to 95% ammonia fuel substitution rates.

Bunkering infrastructure encompasses the fueling stations, storage tanks, and transfer systems required to load ammonia onto vessels at ports. Ammonia bunkering requires pressurized or refrigerated storage at minus 33 degrees Celsius and specialized loading arms with vapor recovery systems due to ammonia's toxicity. The Port of Singapore has invested $180 million in dedicated ammonia bunkering facilities at Jurong Island.

NOx and N2O slip management: Ammonia combustion produces nitrogen oxides (NOx) and can release nitrous oxide (N2O), a greenhouse gas with 273 times the global warming potential of CO2 over a 100-year horizon. Selective catalytic reduction (SCR) systems and combustion tuning are critical to maintaining the emissions advantage of ammonia fuel.

What's Working

The GCASI pilot has delivered measurable results across emissions, operational performance, and infrastructure readiness that are informing ammonia fuel strategies across the Asia-Pacific region.

CO2 Reductions Are Substantial and Verifiable

The pilot's flagship vessel, the NYK-operated bulk carrier Sakura Leader (retrofitted with an IHI dual-fuel ammonia engine), achieved an average 92% reduction in tank-to-wake CO2 emissions during its 40 completed voyages between Singapore and Yokohama. On a well-to-wake lifecycle basis, using green ammonia sourced from the ACME Group's renewable ammonia facility in Oman, the reduction drops to approximately 78%, reflecting upstream energy inputs for electrolysis and synthesis. Independent verification by Lloyd's Register confirmed these figures through continuous emissions monitoring systems (CEMS) installed on the vessel. The pilot has displaced an estimated 42,000 metric tons of CO2 compared to HFO-fueled equivalent voyages over 24 months of operation (Lloyd's Register, 2025).

Engine Technology Has Proven Operational Viability

IHI's 2-stroke dual-fuel ammonia engine, rated at 12,000 kW, demonstrated sustained operation at 90% ammonia substitution rates during open-ocean transit, with diesel pilot fuel comprising the remaining 10% for ignition stability. Engine availability exceeded 97% across the pilot period, comparable to conventional HFO engines. MAN Energy Solutions' ME-LGIP (Liquid Gas Injection, Ammonia) engine, deployed on a second pilot vessel operated by Mitsui O.S.K. Lines (MOL), achieved similar performance benchmarks. Both engines showed NOx emissions within IMO Tier III limits when paired with SCR aftertreatment systems, and N2O slip was maintained below 0.015 g/kWh through optimized injection timing, a critical threshold identified by DNV as necessary to preserve the climate benefit of ammonia fuel (DNV, 2025).

Bunkering Operations Have Been Standardized

The Port of Singapore completed its first ship-to-ship ammonia bunkering operation in September 2024, transferring 3,200 metric tons of ammonia to the Sakura Leader in 14 hours using a dedicated ammonia bunker barge. PSA and the Maritime and Port Authority of Singapore (MPA) developed safety protocols that include a 500-meter exclusion zone, continuous atmospheric ammonia monitoring with alarm thresholds at 25 ppm, and mandatory crew certification in ammonia handling. As of early 2026, the port has completed 28 ammonia bunkering operations without a reportable safety incident. Yokohama Port has commissioned a shore-based ammonia terminal with 15,000 metric ton storage capacity, enabling the Japan endpoint of the green corridor to offer consistent fuel supply (MPA Singapore, 2025).

Cost Premium Is Narrowing Faster Than Expected

Early projections estimated green ammonia fuel costs at 4 to 5 times the price of HFO on an energy-equivalent basis. Actual procurement costs during the pilot averaged $28 per GJ, compared to $8 per GJ for HFO, representing a 3.5x premium rather than the feared 5x. This narrowing reflects declining electrolyzer costs (down 40% since 2022), competitive offtake agreements with producers in the Middle East and Australia, and Japan's Green Innovation Fund subsidy of up to $15 per GJ for qualifying green ammonia purchases. MLIT projects that further scaling of production and long-term contracts could bring the premium below 2.5x by 2028.

What's Not Working

Despite encouraging results, the pilot has exposed persistent challenges that must be addressed for ammonia to scale as a mainstream shipping fuel.

Toxicity Risks Demand Extensive Safety Protocols

Ammonia is acutely toxic at concentrations above 300 ppm, with an immediately dangerous to life or health (IDLH) threshold of 300 ppm for 30-minute exposure. During the pilot, two minor ammonia vapor release events occurred: one during a valve maintenance procedure at Singapore and one during engine fuel system testing at Yokohama. Both were contained within seconds by automatic shutoff systems and resulted in no injuries, but they triggered mandatory 48-hour operational reviews and temporary suspension of bunkering activities. The extensive safety infrastructure required, including gas detection networks, emergency ventilation systems, and specialized personal protective equipment, adds approximately $2.5 million to $4 million in retrofit costs per vessel beyond the engine conversion itself.

Crew Training and Certification Bottlenecks

The International Convention on Standards of Training, Certification and Watchkeeping for Seafarers (STCW) does not yet include ammonia-specific competency standards. The pilot developed proprietary training curricula in partnership with the Singapore Maritime Academy, requiring 120 hours of classroom and simulator instruction per crew member. As of 2026, only 680 seafarers across the Asia-Pacific region hold ammonia handling certifications recognized by flag state authorities, a fraction of the estimated 15,000 to 20,000 trained personnel needed to support a meaningful fleet transition. The training pipeline is constrained by the limited number of approved simulation facilities: only four exist in the region, located in Singapore, Yokohama, Busan, and Mumbai.

Green Ammonia Supply Remains Constrained

Global green ammonia production capacity stands at approximately 800,000 metric tons per year as of early 2026, a small fraction of the 185 million metric tons of total global ammonia production. The GCASI pilot secured a dedicated supply contract with ACME Group's 1.2 GW electrolyzer facility in Oman, but this single-source dependency creates supply chain vulnerability. Several planned green ammonia projects in Australia, Chile, and Saudi Arabia have experienced 12 to 24 month delays due to electrolyzer delivery timelines and renewable energy permitting bottlenecks. The pilot consumed approximately 18,000 metric tons of green ammonia over 24 months, representing roughly 2% of current global green ammonia output, illustrating the scale mismatch between available supply and projected maritime demand.

Port Infrastructure Investment Gaps Persist

While Singapore and Yokohama have made substantial bunkering investments, the broader Asia-Pacific port network lacks ammonia fueling capability. Of the 50 largest container ports in the region, only 4 have committed capital to ammonia bunkering facilities. Without a network of fueling points, ammonia-powered vessels are confined to specific routes, limiting the commercial flexibility that shipowners require to justify fleet-wide conversion investments. Industry estimates suggest $30 to $50 billion in cumulative port infrastructure investment is needed across Asia-Pacific by 2035 to support widespread ammonia bunkering.

Key Players

Established Companies

• NYK Line: Japan's largest shipping company by fleet size, operating the pilot's flagship ammonia-fueled bulk carrier and committing to 30 ammonia-ready newbuilds by 2030.
• IHI Corporation: Developed the 2-stroke dual-fuel ammonia engine deployed in the pilot, with 12,000 kW output and 90% ammonia substitution capability.
• MAN Energy Solutions: Supplies the ME-LGIP ammonia engine platform, with commercial delivery commitments to over 20 shipowners globally.
• Mitsui O.S.K. Lines (MOL): Operates the second pilot vessel on the Singapore-Yokohama route and leads ammonia fuel research through its MOL Group Environmental Vision 2.2.
• Port of Singapore Authority (PSA): Invested $180 million in Jurong Island ammonia bunkering infrastructure and developed operational safety protocols now referenced by ports worldwide.

Startups

• ACME Group: Indian-headquartered green hydrogen and ammonia producer operating a 1.2 GW electrolyzer facility in Oman, supplying the pilot's green ammonia at contracted volumes.
• Amogy: US-based startup developing ammonia-to-power cracking technology that converts ammonia back to hydrogen onboard, enabling fuel cell propulsion as an alternative to direct combustion.
• C-Zero: Developing methane pyrolysis technology for turquoise hydrogen production, offering a lower-cost pathway to low-carbon ammonia synthesis for maritime applications.

Investors and Funders

• Japan's Green Innovation Fund: Allocated $1.5 billion for ammonia fuel development, including direct subsidies for green ammonia procurement in the GCASI pilot.
• Maritime and Port Authority of Singapore (MPA): Committed $300 million through its Maritime Singapore Green Initiative to support ammonia bunkering infrastructure and vessel retrofits.
• Asian Development Bank (ADB): Provided $120 million in concessional financing for green ammonia supply chain development across the pilot corridor.

KPI Summary

KPI	Baseline (2023)	Current (2026)	Target (2030)
Ammonia-fueled voyages completed	0	40	500
Nautical miles logged on ammonia	0	180,000	2,000,000
Tank-to-wake CO2 reduction vs HFO	0%	92%	95%
Ammonia bunkering operations (Singapore)	0	28	200
Safety incidents (reportable)	N/A	0	0
Green ammonia cost premium vs HFO	N/A	3.5x	2.0x
Certified ammonia-handling seafarers (APAC)	0	680	15,000

Action Checklist

• Commission a fleet-wide fuel transition feasibility study covering vessel age profiles, trade route patterns, and ammonia engine retrofit or newbuild economics
• Engage ammonia fuel suppliers at least 36 months ahead of planned deployment to secure long-term offtake agreements at predictable pricing
• Assess port infrastructure readiness along primary trade routes and identify bunkering availability gaps that constrain route planning
• Develop ammonia safety management systems aligned with the IMO's Interim Guidelines for Ships Using Ammonia as Fuel (MSC.1/Circ.1621)
• Invest in crew training programs covering ammonia handling, emergency response, and engine operation, budgeting 120 hours per crew member
• Evaluate ammonia cracking and fuel cell alternatives to direct combustion for vessel classes where N2O slip management is technically challenging
• Monitor regulatory developments including IMO mid-term measures, EU FuelEU Maritime compliance pathways, and national ammonia fuel subsidy programs

FAQ

Q: How does ammonia compare to methanol and LNG as alternative shipping fuels? A: Ammonia offers the highest decarbonization potential among commercially available alternative fuels when produced from renewable sources. Green ammonia delivers 90 to 95% tank-to-wake CO2 reduction versus HFO, compared to 65 to 75% for green methanol and 20 to 25% for LNG (due to methane slip). However, ammonia's toxicity introduces safety requirements that methanol and LNG do not carry, and its lower energy density (12.7 MJ/L versus 15.8 MJ/L for methanol and 22.2 MJ/L for LNG) requires approximately 50% more fuel storage volume than HFO for equivalent range. The choice between fuels depends on route length, regulatory requirements, and port infrastructure availability along specific trade lanes.

Q: What does it cost to retrofit an existing vessel for ammonia fuel capability? A: Full retrofit costs for a medium-sized bulk carrier or container vessel range from $15 million to $25 million, covering engine conversion to dual-fuel ammonia capability, fuel storage tank installation (typically double-walled, refrigerated tanks on deck), safety systems including gas detection and ventilation, and crew training. For newbuild vessels, the ammonia-ready premium is lower at approximately $8 million to $12 million, because fuel systems are integrated during construction. The GCASI pilot's Sakura Leader retrofit cost $22 million, partially offset by $9 million in Green Innovation Fund subsidies. At current fuel cost premiums, the payback period for retrofit investment exceeds 15 years without carbon pricing or regulatory penalties, but drops to 7 to 9 years under a $100 per ton CO2 price scenario.

Q: Is green ammonia supply sufficient to support a meaningful fleet transition? A: Not yet. Current global green ammonia production of approximately 800,000 metric tons per year could fuel fewer than 200 large vessels on typical Asia-Europe trade routes. However, the announced project pipeline is substantial: IRENA tracks over 70 green ammonia projects globally with a combined planned capacity exceeding 15 million metric tons per year by 2030. The challenge is execution. Electrolyzer manufacturing capacity, renewable energy project timelines, and ammonia synthesis plant construction all face bottlenecks. The GCASI pilot demonstrates that operational demand can be met at corridor scale, but fleet-wide transition will require a 20 to 30x increase in green ammonia supply within the next decade.

Q: What are the primary safety concerns with ammonia as a marine fuel? A: Ammonia's acute toxicity is the dominant safety concern. Exposure to concentrations above 300 ppm for 30 minutes is immediately dangerous to life. In enclosed engine room spaces, even minor leaks can rapidly reach hazardous levels. The GCASI pilot addressed this through redundant gas detection systems with automatic engine shutdown at 25 ppm, forced ventilation capable of 30 air changes per hour in machinery spaces, double-walled fuel piping with interspace monitoring, and comprehensive crew training with quarterly emergency drills. The pilot's zero-reportable-incident record over 28 bunkering operations and 40 voyages provides early evidence that these safety measures are effective, but the maritime industry acknowledges that scaling to thousands of vessels will require standardized international safety frameworks that are still under development at the IMO.

Sources

• NYK Line. (2025). Green Corridor Ammonia Shipping Initiative: Operational Performance Report 2023-2025. Tokyo, Japan: Nippon Yusen Kabushiki Kaisha.
• Lloyd's Register. (2025). Independent Verification of Ammonia-Fueled Vessel Emissions: GCASI Pilot Program. London, UK: Lloyd's Register Group.
• DNV. (2025). Maritime Ammonia Fuel Safety and Emissions Assessment: Technical Review of Asia-Pacific Pilot Operations. Oslo, Norway: DNV AS.
• Maritime and Port Authority of Singapore. (2025). Ammonia Bunkering Operations: Safety Protocols and Performance Data. Singapore: MPA.
• International Renewable Energy Agency. (2025). Green Ammonia: Cost and Production Outlook for Maritime Applications. Abu Dhabi, UAE: IRENA.
• International Maritime Organization. (2023). 2023 IMO Strategy on Reduction of GHG Emissions from Ships. London, UK: IMO.
• Japan Ministry of Land, Infrastructure, Transport and Tourism. (2025). Green Innovation Fund: Ammonia Fuel Development Program Progress Report. Tokyo, Japan: MLIT.
• Asian Development Bank. (2025). Financing Green Ammonia Supply Chains in the Asia-Pacific Region. Manila, Philippines: ADB.