As the shipping industry grapples with mounting pressure to reduce its carbon footprint, the search for viable alternative fuels has become increasingly urgent. Maritime transport accounts for nearly 3% of global carbon dioxide emissions, and the International Maritime Organization (IMO) aims to cut these emissions by at least 50% by 2050. Amidst this transition, ammonia-powered ships have emerged as a promising alternative. But are they truly the future of sustainable marine transport? This blog explores the potential, challenges, and outlook for ammonia as a marine fuel.
What Are Ammonia-Powered Ships?
Ammonia-powered ships are vessels designed or retrofitted to operate using ammonia (NH3) as a fuel source. Ammonia can be used in internal combustion engines or fuel cells, offering a carbon-free combustion process if produced from renewable energy sources. Known for its widespread use in fertiliser production, ammonia is now being re-evaluated as a marine fuel due to its zero-carbon potential and compatibility with existing liquefied petroleum gas (LPG)infrastructure.
Green ammonia, produced from renewable energy, green hydrogen, and atmospheric nitrogen, emits no carbon dioxide when combusted, making it a leading candidate among low-carbon fuels.
How Does Ammonia Help Decarbonise Shipping?
Source: World Economic Forum
The appeal of ammonia fuel lies in its ability to significantly reduce carbon emissions from the shipping industry. When derived from green hydrogen, ammonia serves as a zero-carbon fuel. Compared to fossil fuels and heavy fuel oil, ammonia produces no CO2 during combustion.
Moreover, ammonia has 10 times the energy density of lithium-ion batteries and its ammonia storage is easier than that of hydrogen, which requires high-pressure tanks or cryogenic storage. It can be stored in liquid form, making it suitable for long voyages that characterise most ocean-going vessels. As such, ammonia is considered an attractive alternative for marine fuel in long-distance shipping.
Sustainability Impact of Ammonia Fuel
When produced sustainably, green ammonia offers considerable benefits for reducing GHG emissions. It does not emit CO2 during combustion, potentially allowing the maritime sector to meet IMO’s decarbonisation targets.
However, ammonia combustion can produce nitrous oxide (N2O), a greenhouse gas 270 times more potent than CO2. Additionally, NOx emissions are a concern and may necessitate exhaust after-treatment systems such as selective catalytic reduction.
From a supply chain perspective, ammonia’s existing transport and storage infrastructure—used for fertilisers—gives it a head start over newer fuels. Still, the marine industry must invest in new ammonia fuel systems, engines, and safety mechanisms to ensure viable deployment.
Challenges and Safety Concerns
Despite its potential, ammonia presents several key challenges:
- Toxicity: Ammonia is highly toxic and can irritate or harm the skin, lungs, and eyes. Proper handling ammonia procedures and personal protective equipment (PPE) are essential.
- Ammonia Storage: It has a low energy density, requiring larger tanks that may reduce cargo space.
- Ammonia Emissions: The formation of NOx emissions and nitrous oxide during combustion poses new environmental risks.
- Cost: Currently, green ammonia is 2–4 times more expensive than traditional marine fuels, largely due to limited supply and high production costs.
- Maintenance: Ammonia is corrosive and may require more frequent engine maintenance.
- Ammonia Marine Fuel Safety: A pilot study in Singapore revealed over 400 risks related to ammonia bunkering, including leaks during fuel transfer and storage.
These concerns necessitate clear safety procedures, crew training, and updated regulatory landscape to ensure ammonia is a viable alternative.
Projected Marine Fuel Use and Ammonia’s Role
The American Bureau of Shipping and DNV project that ammonia fuel could constitute up to 25–30% of the maritime fuel mix by 2050. In comparison, liquefied natural gas (LNG) and methanol are currently ahead in terms of adoption, with hundreds of vessels already using them.
Despite a slow start—only 25 ammonia dual-fuel ships were on order as of 2024—the potential remains strong. According to the Global Centre for Maritime Decarbonisation, ammonia could play a key role in reaching global emission targets. Its ability to act as a zero-carbon fuel, especially in deep-sea shipping, makes it crucial for long-term planning.
Industry leaders are developing engines and fuel cells compatible with ammonia. Simultaneously, governments are investing in green hydrogen production to create sufficient supplies of only green ammonia for bunkering purposes.
Challenges of Infrastructure and Scalability
A key hurdle in adopting ammonia as a marine fuel is the lack of global infrastructure. Unlike liquefied natural gas (LNG), which now benefits from a widespread bunkering network, ammonia fuel systems are in their infancy. There are very few ammonia bunkering terminals worldwide, and existing port infrastructure is not equipped to handle the unique storage and safety demands of ammonia fuel. Handling ammonia requires specialised pipelines, double-walled tanks, and ventilated storage environments due to its high toxicity and low energy density. Building these systems from scratch demands significant capital and coordination between port authorities, regulators, and private industry.
Moreover, the supply chain for green ammonia, produced using renewable energy, remains highly underdeveloped. Most ammonia today is brown ammonia, derived from natural gas, which defeats the purpose of using it as a zero-carbon fuel. Scaling up the production of green hydrogen, an essential feedstock for green ammonia, is both energy- and land-intensive. Until renewable-powered electrolysers reach commercial viability and scale, the industry risks facing a fuel bottleneck. Thus, without concerted efforts in policy, investment, and technology alignment, the widespread rollout of ammonia-powered ships remains a long-term vision rather than an immediate reality.
Regulatory Gaps and the Role of Policy
While momentum around ammonia as a marine fuel is building, the regulatory landscape is still catching up. Current safety procedures and existing regulations under the International Maritime Organization (IMO) are not fully equipped to address the ammonia marine fuel safety concerns related to toxicity, emissions, and emergency handling. For example, while the IGC Code provides rules for transporting ammonia as cargo, comprehensive global guidelines for using it as fuel are still under development. This uncertainty slows the adopting of ammonia and makes shipowners hesitant to invest in ammonia fuel systems or retrofit vessels.
Establishing robust classification societies and internationally agreed-upon design and operation standards is essential for the growth of ammonia-powered ships. Regulatory incentives—like carbon pricing, fuel subsidies, or emissions-based port fees—could make green ammonia more competitive against conventional fuels and heavy fuel oil. Furthermore, policies encouraging fuel cells, carbon capture, and wind-assisted propulsion could work in tandem with ammonia adoption to reduce greenhouse gas emissions.
Clear regulatory frameworks will also protect seafarers, port workers, and the environment. Without a coherent and globally enforced maritime fuel strategy, the transition to low carbon fuels risks being fragmented, inefficient, and dangerous.
The Future of Ammonia in Maritime Transport
Several pilot projects signal the direction the maritime industry is heading:
- Viking Energy: This Norwegian vessel is being retrofitted with a 2MW ammonia fuel cell.
- NYK Line: Japan’s leading shipowner is developing the first medium-sized ammonia-fuelled gas carrier.
- Singapore’s Port Authority: Is drafting bunkering standards for ammonia and evaluating its use in power generation.
Further, classification societies like Bureau Veritas have issued tentative rules (NR 671) and notations such as AMMONIAFUEL-PREPARED to support ammonia as a marine fuel. Nonetheless, significant investments in bunkering infrastructure, crew training, and existing regulations are necessary. The next decade will likely be decisive in determining whether ammonia becomes a dominant ship fuel.
Conclusion
Ammonia-powered ships offer a tangible path toward a more sustainable future in maritime transport. While technological, regulatory, and economic barriers exist, the benefits of ammonia fuel, particularly in reducing carbon emissions, are too significant to ignore. As global initiatives align to scale green ammonia production and support adoption, ammonia may soon move from experimental to essential in the shipping industry’s clean energy transition.
FAQs
Q1: What is green ammonia?
Green ammonia is produced using renewable energy sources to generate hydrogen via electrolysis, which is then combined with nitrogen from the air.
Q2: Is ammonia a zero-carbon fuel?
Yes, if made using green hydrogen, ammonia is a carbon-free fuel that does not emit CO2 upon combustion.
Q3: What are the risks of ammonia as a fuel?
Its high toxicity, potential for leaks, and formation of NOx emissions are key safety concerns.
Q4: Are there ammonia-powered ships in service?
Only a few small vessels, like tugs, are in operation. Larger ships are expected to enter service by 2026.
Q5: Why isn’t ammonia already widely used?
High operating costs, lack of infrastructure, and unresolved safety challenges have delayed wider adoption.
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