Ammonia as a Marine Fuel: Potential, Practical Use and Outlook Towards 2050
Author: Jeroen Berger • Publication date:
Ammonia (NH3) is increasingly seen as a viable fuel option for climate-neutral shipping. It consists only of nitrogen (N) and hydrogen (H), which means it produces no CO2 when burned. This distinguishes it from fossil fuels and synthetic alternatives such as biogas or e-methanol, which do emit CO2 during use. As a result, ammonia provides a clear advantage in meeting international climate targets for the maritime sector.
Green ammonia is produced through electrolysis using renewable electricity and nitrogen extracted from ambient air. This results in a fully emission-free well-to-wake fuel chain that relies solely on water, air and clean energy. However, onboard use requires specific technical adaptations. Ammonia is toxic and corrosive, and its volumetric energy density is lower than that of LNG or marine diesel. Ships therefore require larger fuel tanks, in combination with modified engine and fuel systems, supported by an integrated safety framework.
Technological development is advancing quickly. Engine manufacturers such as MAN Energy Solutions and Wärtsilä are developing engines suitable for ammonia combustion. At the same time, classification societies including DNV and Lloyd’s Register are finalizing safety guidelines based on risk-based assessments. In ports such as Rotterdam, pilot projects are already testing cryogenic storage and ship-to-ship bunkering for ammonia-powered ships. These initiatives mark the transition from laboratory-scale testing to commercial application. For large-scale adoption, technical standards and regulatory frameworks must evolve in parallel.
Regulatory developments are also moving forward. In July 2023, the International Maritime Organization (IMO) adopted stricter climate targets under MARPOL Annex VI. Ships above 5,000 GT must reduce greenhouse gas emissions by 20 percent by 2030 and by 70 percent by 2040, compared to 2008 levels. From 2030 onward, at least 5 percent of onboard energy must come from fuels with very low or zero emissions. These targets are expected to become legally binding under the IMO Net-Zero Framework starting in 2028. This provides a more predictable investment outlook for ammonia-powered ships and other carbon-free marine fuels.
The European Union is taking a similar approach. Since 2024, maritime emissions have been included in the EU Emissions Trading System (EU ETS). As of 2025, the FuelEU Maritime regulation will require a gradual reduction in the lifecycle emissions of marine fuels. In this context, ammonia-powered ships offer strategic value for shipowners from around 2030: they reduce emissions, lower regulatory costs and support long-term fleet compliance. However, these benefits depend on coordinated progress in technology, infrastructure and policy through to 2050.
This article compares ammonia with other marine fuel alternatives such as methanol, hydrogen and LNG, focusing on safety, energy efficiency and regulatory compliance. Following an overview of its physical properties and legal context, the article examines practical applications in maritime operations. It concludes with strategic recommendations on vessel design, certification and investment planning toward sustainable shipping by 2050.
What Is Ammonia as a Marine Fuel?
Ammonia (NH3) is rapidly emerging as a viable fuel for climate-neutral shipping. The molecule consists solely of nitrogen (N) and hydrogen (H), meaning its combustion produces no CO2. This essential characteristic distinguishes ammonia from fossil fuels and synthetic alternatives such as biogas or e-methanol, which do emit CO2 during use.
When ammonia is produced using renewable electricity via electrolysis and nitrogen extracted from ambient air, it is classified as green ammonia. This enables a fully emission-free well-to-wake fuel chain that relies exclusively on water, air and clean energy. However, using ammonia onboard requires specific technical adaptations. The substance is toxic and corrosive, and its volumetric energy density is lower than that of LNG or marine diesel. As a result, ships need larger fuel tanks, and engine, fuel and safety systems must be modified in line with risk-based design principles.
Technology is progressing toward commercial deployment. Engine manufacturers such as MAN Energy Solutions and Wärtsilä are testing engines designed for ammonia combustion. At the same time, classification societies including DNV and Lloyd’s Register are drafting safety guidelines for the integration of ammonia into shipboard systems. In ports such as Rotterdam, ship-to-ship bunkering trials with cryogenic storage are already underway. These pilots reflect the shift from lab-based research to operational implementation. To enable broader use, technical standards and regulatory frameworks must develop in parallel.
International regulation is supporting this shift. In July 2023, the IMO adopted enhanced climate targets under MARPOL Annex VI. Ships above 5,000 GT must reduce greenhouse gas emissions by 20 percent by 2030 and by 70 percent by 2040, compared to 2008 levels. From 2030 onward, at least 5 percent of onboard energy must be derived from fuels with very low or zero emissions. These requirements are expected to become legally binding under the IMO Net-Zero Framework starting in 2028. This regulatory certainty provides a clearer investment outlook for zero-carbon fuels such as ammonia.
The European Union has also set comparable targets. Since 2024, maritime transport has been included in the EU Emissions Trading System (EU ETS). From 2025 onward, the FuelEU Maritime regulation will require lifecycle emissions reporting for marine fuels. This reinforces the strategic value of ammonia-powered ships by around 2030: lowering emissions, reducing regulatory costs and supporting long-term fleet deployment. However, success depends on coordinated development in technology, infrastructure and policy. This alignment is essential to enable investment planning through to 2050.
Why Is Ammonia a Promising Fuel for Shipping?
Ammonia offers clear climate advantages because it consists solely of nitrogen (N) and hydrogen (H). Its combustion does not release any CO2, setting it apart from fossil fuels and synthetic alternatives such as biogas or e-methanol, which do emit CO2 during use. The nitrogen component returns to the atmosphere as nitrogen gas (N2), aligning ammonia with long-term climate neutrality objectives. However, the combustion process must be carefully managed to limit nitrogen oxide (NOx) emissions. In maritime settings, this is typically achieved using selective catalytic reduction (SCR) systems.
Ammonia’s strategic value is reinforced by regulation. Since 2024, low- and zero-emission operations result in direct cost savings under the European Emissions Trading System (EU ETS). From 2025 onward, FuelEU Maritime will require lifecycle emissions assessments for all marine fuels. Both blue and green ammonia meet these criteria and support long-term regulatory compliance. Under frameworks such as the Energy Efficiency Existing Ship Index (EEXI) and the Carbon Intensity Indicator (CII), the use of ammonia leads to higher performance scores per ton-kilometer. It also supports compliance with the Energy Efficiency Design Index (EEDI) targets.
In operational terms, ammonia offers advantages for onboard storage and vessel range. While its volumetric energy density is slightly lower than that of methanol or LNG, it is significantly higher than hydrogen under comparable conditions. Ammonia remains liquid at minus 33 degrees Celsius or approximately 10 bar, similar to LPG. Hydrogen, by contrast, requires either extremely low temperatures or high-pressure storage. Some ammonia-powered ships are designed to use the fuel as both energy source and cargo in a shared tank system, thereby extending range without needing additional bunkering infrastructure.
From a logistical standpoint, ammonia has a key advantage: much of the necessary infrastructure is already in place. More than 200 ports worldwide are equipped with ammonia transfer systems, primarily due to its existing role in the fertilizer industry. In 2023, global ammonia production reached approximately 180 million tons. Pilot bunkering operations in ports such as Rotterdam and Singapore have demonstrated that storage and ship-to-ship transfer can be carried out safely. In addition, ammonia can act as a hydrogen carrier. Through onboard or port-based cracking, zero-emission hydrogen can be produced locally, adding flexibility to maritime fuel logistics.
Although the current cost of green ammonia is higher than that of conventional marine fuels, prices are expected to decline over time. This trend will be driven by scaled-up production, advances in technology and falling costs for renewable electricity. At the same time, rising CO2 levies on fossil fuels will help narrow the price gap. Strategic bunkering hubs are already emerging in regions with access to low-cost renewable power, including the Middle East, Australia and South America. Shipowners who begin investing in ammonia today will benefit from long-term regulatory alignment, lower emissions and reduced compliance costs. With appropriate technologies and scaling, maritime CO2 emissions could be reduced by up to 90 percent by 2050.
Technological Status and Practice: Ammonia Across Maritime Sectors
By 2025, ammonia represents a significant technological shift in the maritime industry. What was once limited to experimental applications is now emerging as a practical fuel across multiple shipping segments. The first commercial orders and pilot projects confirm this transition. The degree of technological maturity varies by segment, depending on factors such as scalability, safety standards and implementation timelines.
In intercontinental shipping, ammonia is one of the few truly carbon-free fuel options available for vessels with high energy demands, such as container ships, tankers and bulk carriers. These vessels traditionally rely on heavy fuel oil and account for a large share of global CO2 emissions. In response, engine manufacturers such as MAN Energy Solutions and Wärtsilä are developing dual-fuel engines that can operate on ammonia. These engines are expected to become commercially available from 2027, primarily for application in newbuilds. At the same time, manufacturers are designing ammonia-fueled shaft generators to replace conventional auxiliary generators. Lloyd’s Register has granted approval in principle for initial system configurations. As a result, more shipowners are choosing ammonia-ready vessel designs, with deployment anticipated between 2030 and 2040.
Different considerations apply to coastal and short-sea shipping. Limited tank space and proximity to residential and urban infrastructure require enhanced safety measures. Development efforts in this segment focus on hybrid configurations, combining battery systems with biofuels. Demonstration projects in Northwest Europe have shown that small-scale ammonia use is technically viable. However, broader implementation in this segment is not expected before 2030 and will depend on additional investment in infrastructure, certification processes and risk management.
Ammonia is already being used in operational settings within offshore and specialized shipping. One platform supply vessel has been converted to a dual-fuel configuration using both diesel and ammonia, featuring modified fuel systems, bunkering equipment and onboard safety installations. After extensive testing and successful classification, the vessel has entered commercial service. A second example involves a supply vessel equipped with a 2-megawatt solid oxide fuel cell for direct ammonia use. This vessel is scheduled to enter operation in 2026, targeting a reduction in greenhouse gas emissions of at least 70 percent, subject to final design approval.
Technological progress is being accelerated through close collaboration between shipowners, technology suppliers and classification societies. Companies such as Alfa Laval and Wärtsilä Gas Solutions are developing modular supply systems that deliver ammonia to engines under controlled pressure and temperature. Steam boilers have also been adapted to convert ammonia vapor into process steam, particularly for offshore operations.
Classification societies including DNV and ABS are drafting new standards to support risk-based design. These include criteria for leak detection, ventilation, materials selection and engine room layout. The standards are already being applied in dual-fuel newbuilds and ammonia tankers. Lloyd’s Register is contributing to this process through structured risk assessments such as HAZID and HAZOP, with a focus on structural integrity and operational reliability. Together, these developments provide a certifiable framework that offers shipowners clarity for both design decisions and long-term fleet planning.
Training is another critical component. Shipowners, classification societies, maritime academies and technology providers are jointly developing training programs that meet technical and regulatory requirements. This coordinated approach, integrating technology, training and safety standards, provides the foundation for the safe and scalable deployment of ammonia-powered ships from around 2030 onward.
Policy Frameworks and Strategic Support
The shift to ammonia as a marine fuel is underpinned by a strong foundation of international regulation, European legislation and public-private cooperation. Together, these three pillars form the policy framework required for large-scale deployment in the maritime sector.
The International Maritime Organization (IMO) has set emission limits for sulfur oxides (SOx) and nitrogen oxides (NOx) under MARPOL Annex VI. Because ammonia contains no sulfur, it naturally complies with the SOx limit of 0.5 percent. However, ammonia combustion does produce NOx and nitrous oxide (N2O), which means post-treatment systems such as selective catalytic reduction (SCR) are standard. As a result, safety is a structural element of the fuel transition strategy.
The current International Code of Safety for Ships Using Gases or Other Low-Flashpoint Fuels (IGF Code) provides safety criteria for LNG but does not yet cover ammonia. Until formal amendments are adopted, the alternative design procedure applies. This requires flag states and classification societies to prove that a vessel’s design meets safety objectives through structured risk analysis and validation. In this way, technological innovation is directly linked to verifiable operational safety.
In July 2023, the IMO introduced additional climate targets under MARPOL Annex VI: a 20 percent reduction in emissions by 2030 and 70 percent by 2040, compared to 2008 levels. From 2030 onward, at least 5 percent of onboard energy must come from fuels with a very low or zero emission profile. These targets are expected to become legally binding under the IMO Net-Zero Framework starting in 2028. As a result, investment in carbon-free fuels such as ammonia becomes not only attractive but necessary for regulatory compliance.
The European Union is taking a similar approach. Since 2024, the maritime sector has been included in the EU Emissions Trading System (EU ETS). As of 2025, the FuelEU Maritime regulation will require lifecycle emissions assessments for all marine fuels. This gives ammonia strategic advantages from around 2030: lower emissions, reduced regulatory costs and enhanced fleet readiness. However, these advantages depend on coordinated and timely development of technology, regulation and infrastructure. This alignment is essential for sound investment planning through to 2050.
Support at the national level is also expanding. The Dutch Maritime Strategy 2022–2050 specifically identifies ammonia as a fuel with long-term potential. European programs such as Horizon Europe and the Innovation Fund are backing demonstration and scale-up projects, including AmmoniaDrive, led by the Netherlands Organisation for Scientific Research (NWO). Inland shipping also stands to benefit. From around 2030, inland ports may be designated as zero-emission zones, provided that NOx emissions remain demonstrably low.
Standardization initiatives by international bodies such as ISO and CEN are critical for uniform implementation and certification. These organizations are developing standards for fuel quality, materials and safety systems. Classification societies such as DNV are already applying these standards in issuing ammonia-ready notations for both newbuilds and retrofits. At the same time, mechanisms like the Green Investment Scheme and initiatives such as the Getting to Zero Coalition are accelerating commercial uptake. As a result, new shipping corridors are emerging between the Middle East and Europe, where ammonia-powered ships are expected to enter service around 2030, supported by a stable mix of financing, infrastructure and regulatory certainty.
Infrastructure and Bunkering: Logistical Preconditions
For ammonia-powered vessels, a safe and reliable fuel logistics chain is essential. Due to its toxic and corrosive nature, ammonia requires modified bunkering procedures, specialized port infrastructure and strict safety protocols. Leaks pose risks not typically associated with conventional fuels.
In 2025, a pilot operation was conducted in the Port of Rotterdam. During this trial, 800 cubic meters of liquid ammonia at minus 33 degrees Celsius were transferred ship-to-ship over two and a half hours without incident. The process was carried out under continuous gas monitoring, with water mist systems and evacuation procedures in place. The trial demonstrated that bunkering can be safely executed when additional safeguards are in place, including double hose connections, automated leak detection, appropriate fire suppression systems and properly trained personnel. Following the test, the port of Rotterdam enhanced its operational preparedness. Other ports, including Singapore and Houston, are developing similar procedures in anticipation of commercial use starting in 2026.
Large-scale adoption will require sufficient storage capacity. Existing terminals, originally designed for the fertilizer industry, need technical upgrades. In Rotterdam, a permit has been granted for a new ammonia terminal at Maasvlakte with a 30,000-ton capacity. This facility will feature cryogenic pumps, coated pipelines and customized loading systems. Until purpose-built bunkering vessels are operational, repurposed LPG or ammonia carriers are being used as temporary storage and transfer platforms. This enables a gradual transition toward an LNG-like infrastructure model.
The location of bunkering infrastructure is a key safety factor. Ideally, these facilities are located outside densely populated areas, positioned on the windward side and situated at a safe distance from other cargo operations. This facilitates evacuation and limits the potential impact of incidents. Without coordinated efforts by port authorities, permitting bodies and emergency response services, continuous and safe ammonia bunkering will remain a logistical and regulatory challenge beyond 2030.
Globally, bunkering hubs are emerging in regions with access to low-cost renewable electricity, such as the Middle East, Australia and South America. These hubs serve as links between ammonia production sites and major shipping corridors. The fuel is delivered using specialized gas carriers or converted LPG vessels. Some of these vessels function as temporary floating bunkering units, using part of the cargo for self-propulsion while supplying the remainder to passing ships. This setup improves operational flexibility and lowers market entry barriers.
Additional infrastructure is required for regional distribution, particularly pipelines connecting industrial production zones with ports. Alternatives such as road transport or inland shipping face longer permitting timelines. Pipelines allow for on-site processing, reduce the need for large-scale urban storage and enhance both safety and efficiency.
Material selection is critical. Ammonia is incompatible with materials such as copper, zinc and certain plastics. Therefore, tanks and piping must be made from stainless steel or coated carbon steel. All ammonia systems must include gas detection, mechanical ventilation and thermal insulation. Regular inspections and maintenance are essential to prevent corrosion and leakage.
Crew members play a vital role. They must be trained to handle ammonia safely, using gas-tight protective clothing, breathing apparatus and emergency shower systems. Although the current STCW Code does not yet include modules specific to toxic fuels, some shipowners have already initiated in-house training programs.
Shore-based personnel also need targeted instruction. Firefighters, dockworkers and emergency teams are participating in joint exercises focused on bunkering and emergency response scenarios. A multidisciplinary approach that connects infrastructure, technology, training and regulation is essential to enable the safe and scalable use of ammonia as a marine fuel from 2030 onward.
Ammonia Versus Other Alternative Fuels
Ammonia is not the only fuel option in the transition to sustainable shipping, but it stands out in terms of energy density, safety and logistical feasibility. These characteristics are essential for making strategic decisions toward 2050.
Both ammonia and hydrogen emit no CO2 during combustion and are therefore aligned with international climate targets. However, their storage requirements differ significantly. Hydrogen must be stored at extremely low temperatures of minus 253 degrees Celsius or at pressures up to 700 bar. Ammonia, by contrast, remains liquid at minus 33 degrees Celsius or around 10 bar, which simplifies system installation. From a safety perspective, hydrogen is highly explosive, while ammonia is toxic but generally more stable under controlled conditions. The use of selective catalytic reduction (SCR) systems to treat NOx and N2O emissions is now standard in maritime ammonia applications.
Methanol is appealing due to its ease of storage at ambient temperatures and its compatibility with dual-fuel engines. However, it contains carbon and therefore produces CO2 during use. This limits its alignment with FuelEU Maritime and results in lower performance scores under frameworks such as the Carbon Intensity Indicator (CII). Ammonia, by contrast, enables near-complete CO2 reduction. Methanol does offer approximately 30 percent higher volumetric energy density, which may be relevant where tank space is constrained.
Liquefied natural gas (LNG) is currently widely available and emits about 20 percent less CO2 than conventional marine fuels. It benefits from an established global infrastructure, which facilitates implementation. However, LNG is not carbon-free, and methane slip throughout the value chain offsets much of its climate benefit. Ammonia largely avoids this drawback. Regarding safety, LNG requires fire protection systems, while ammonia requires gas detection, enhanced ventilation and clearly defined evacuation protocols.
Biofuels such as hydrotreated vegetable oil (HVO) and biodiesel can be used without engine modifications and reduce biogenic CO2 emissions. However, their availability is limited, and they often compete with agricultural production. Moreover, their long-term role under evolving policy frameworks remains uncertain. Ammonia offers greater scalability, particularly when produced using renewable electricity and nitrogen extracted from air.
Fully electric propulsion is well suited to short-distance routes. It delivers zero-emission performance and reduces onboard noise. However, for long-distance shipping, battery systems are less practical due to limitations in weight and volume. In this context, ammonia is a more feasible solution. While its energy density is somewhat lower than methanol’s, its fuel system can be integrated into existing logistics networks and supports intercontinental operations.
Synthetic fuels such as e-diesel and dimethyl ether (DME) can be used in conventional engines and infrastructure, but they always contain carbon. As a result, CO2 emissions remain, leading to continued compliance costs under regulations such as FuelEU Maritime. Ammonia avoids these costs, provided it is produced without emissions. While e-fuels may serve niche markets, only carbon-free energy carriers like ammonia and hydrogen offer a resilient long-term pathway to climate neutrality in the maritime sector by 2050.
Strategic Implications for Shipowners, Investors and Certification
Shipowners considering the use of ammonia as a marine fuel should make strategic decisions early in the vessel design process. Given the long operational lifespan of ships, future-proofing is essential. Selecting an ammonia-ready design that can be converted later without major structural changes helps avoid high retrofit costs and technical constraints.
Initial investment costs are generally higher than those for conventional propulsion systems. However, these are offset by long-term advantages: reduced regulatory costs, improved access to sustainable finance and a more favorable risk profile. Financial institutions are increasingly prioritizing emission reduction and compliance with environmental regulations in their funding criteria. In addition, subsidies, tax incentives and participation in demonstration programs help lower the threshold for early adoption.
Onboard systems must incorporate additional safety and monitoring features. These include gas detection, digital control systems and clearly defined safety protocols. Crew members must be trained in the safe handling of toxic fuels, including the correct use of protective clothing, breathing apparatus and emergency procedures. Certification requirements also demand full transparency on fuel origin: only ammonia that is verifiably produced through sustainable methods qualifies for fiscal incentives or recognition under schemes such as the Environmental Ship Index (ESI) or the Carbon Intensity Indicator (CII).
Shipowners who invest early in technical preparedness, targeted crew training and integrated supply chain strategies are positioning themselves strongly in a maritime sector that is rapidly transitioning toward zero-emission operations. This proactive approach provides not only a competitive advantage, but also safeguards operational continuity under a regulatory environment that will become significantly more stringent by 2030.
Logistical Planning and Fuel Strategy
Ammonia bunkering requires a fundamentally different approach compared to conventional marine fuels. Shipowners must identify at an early stage which ports will offer ammonia and how long-term supply security can be maintained. Collaboration with producers, logistics providers and port authorities is not optional but a strategic requirement.
Some shipowners opt to invest directly in ammonia production or storage capacity. This level of control is especially important during the early adoption phase, when green ammonia prices may fluctuate due to variable electricity costs and evolving CO2 levies. Scenario analyses that account for price developments and supply availability over the vessel’s operational lifespan are essential for managing financial and operational risks.
Other stakeholders pursue a fully integrated supply chain strategy. They invest not only in bunkering infrastructure, but also in upstream renewable energy generation. This vertical integration enhances supply security and cost predictability, though it requires long-term capital investment and substantial financial capacity. At the same time, it provides operational expertise in a developing zero-emission shipping market, strengthening long-term competitiveness.
Conclusion and Recommendations Toward 2050
Ammonia is a technically feasible and scalable fuel option for decarbonizing maritime transport. Because it contains no carbon and offers relatively high energy density, it fits within existing logistics structures. Demonstration projects and increasing acceptance by classification societies confirm its technical suitability. However, further development in safety systems, regulatory frameworks and infrastructure is required to enable large-scale deployment from around 2030.
Accelerated implementation will depend on close cooperation between shipowners, port authorities, technology providers, governments and engine manufacturers. Public authorities play a critical role: regulations must be clear and predictable, funding instruments must be targeted effectively and international coordination is essential to prevent market fragmentation. Shipowners can prepare by investing in ammonia-ready vessels, training crews according to regulatory standards and participating in validation programs. These steps make the transition more manageable and accelerate access to zero-emission shipping markets.
Technological priorities include further emission reduction and improved safety systems. These require implementation of SCR units, advanced gas detection, redundant ventilation and robust bunkering systems with certified storage and transfer infrastructure. Port facilities must be adapted in time to support safe and continuous ammonia bunkering from around 2030 onward.
Flexibility remains essential. Ships with modular architecture or multi-fuel capability are better able to adapt to evolving technologies and market conditions. In this context, ammonia is no longer a distant prospect but an immediately actionable element of the maritime energy transition. Shipowners who now invest in technical readiness and integrated supply chains are securing a strong strategic position in a rapidly developing zero-emission shipping sector.