Over 80% of international trade is carried out by the shipping industry, making it an essential component of the global economy. Shipping is an economical way to transfer goods across long distances, both locally and internationally.

Since the 1950s, because of its widespread availability and low price, heavy fuel oil (HFO) has largely replaced other fuels as the preferred option for the maritime sector. However, there are questions about how long the existing practice of utilizing conventional fossil fuels for shipping will continue.

Shipping accounts for around 3% of the world’s total emissions of greenhouse gases (GHGs) [1]. Thus, the industry is expected to undergo significant technical changes as a result of stringent environmental rules governing NOx, SOx, and CO₂ emissions [2].

There are various fuels and/or technologies, including hydrogen, carbon capture and storage (CCS), biofuels, and nuclear power that have the potential to decarbonize the shipping sector. However, each faces substantial challenges regarding cost, resource access, and societal acceptability [2]. Additionally, numerous efficiency upgrades can reduce fuel use (such as hull design, propeller design, etc.). Several issues/problems need to be resolved to decarbonize the maritime sector thoroughly.

The International Maritime Organization (IMO) has established an approach to gradually reduce greenhouse gas (GHG) emissions by the shipping sector, intending to halve them by 2050 in comparison to 2008 levels. That follows the Paris Accord from the 2015 United Nations Climate Change Conference. The IMO’s policy calls for several short, mid, and long-term actions to reduce GHG emissions gradually. Still, the target it set for 2050 can’t meet without the widespread use of substitute carbon-neutral fuels.

The objective of the IMO, an organization under the United Nations (UN), is to “promote safe, secure, ecologically responsible, efficient, and sustainable shipping via collaboration” [3]. The IMO established the Initial Strategy in April 2018 to reduce GHG emissions from shipping by around 50% by 2050 compared to the baseline year of 2008 [4].

The primary goals of this approach are [5]:

• Reduce international shipping’s carbon intensity in half from 2008 levels by 2030.
• By 2050, the decrease should be increased to 70%.
• To eliminate GHG emissions by 2100, or as soon as is practicable within this century.

Since ammonia (NH₃) is a carbon-free specie, its burning in an internal combustion engine does not release CO₂ into the atmosphere. Ammonia turns into a carbon-neutral fuel when it is synthesized using renewable power sources, such as electricity generated by solar and wind power or from fossil fuels used in conjunction with carbon capture and storage (CCS) technology.

In order to comply with environmental limits on sulfur emission, no SOx removal device is needed on the exhaust. Furthermore, using selective catalytic reduction (SCR) technology, any NOx produced by burning ammonia can be eliminated from exhaust emissions.

Ammonia can be a useful long-term carbon neutrality option and can be strategically used during the transition period. The CO₂ emission can gradually reduce at little risk to the shipowner by switching progressively from fossil-fuel ammonia to green ammonia while simultaneously meeting the sulfur emission standards.

Ammonia General Properties and Production

Anhydrous ammonia, often known as ammonia, is traded globally. There are 180 million metric tons of ammonia produced annually worldwide, and around 80% of that amount is utilized to make fertilizers. The minimum water content in the range of 0.2–0.5 wt% is usually necessary with ammonia in order to prevent stress corrosion cracking in the containers. When used as fuel, the final byproducts are the inert gases nitrogen and water vapors.

Table 1: Commercial-grade ammonia

Ammonia	>99.5 wt%
Water	0.2 – 0.5 wt%
Oil	5ppm (max.)
Specific gravity (16°C)	0.62

Conventionally, ammonia is made using natural gas; as a result, a byproduct of ammonia manufacturing is CO₂. Wherever energy is cheaply and readily accessible, ammonia production is certain to continue. New ammonia facilities can be built in locations that are not practical with fossil feedstock due to the energy captured from renewable sources.

Ammonia is a superior medium for storing energy and transporting hydrogen. Depending on the tank capacity, it can be readily compressed and stored as a liquid in either pressurized or atmospheric tanks. Over 10,000 tons of material can be held in tanks with pressure close to the atmosphere and temperature of -33°C. When storing between 100 to 1,000 tons, the tank pressure drops to just a few bars and the temperature stays around 0°C. Ammonia is commonly stored in tanks with capacities under 100 tons at room temperature and up to 20 bar. Ammonia is a carbon-free fuel with a high energy density (12.7 MJ/L), making it a promising candidate for use as a long-term energy storage medium.

Opportunities/Upsides to Ammonia

Ammonia has the following advantages compared to other fuels:

• Zero Carbon: Ammonia does not release CO₂ during burning since it contains no carbon atoms.
• Energy density: Ammonia has a higher energy density than hydrogen and is comparable to methanol. In comparison to cryogenic liquid hydrogen, it also requires less cooling.
• Lower cost: The Haber-Bosch process is effective and fully scaled for the synthesis of ammonia from zero-carbon hydrogen. Ammonia can be more affordable than either methanol or e-methane due to the lower energy requirements of the Haber-Bosch process.
• Scalability: Ammonia has promise in the long run. The falling cost of renewable energy will support the viability of ammonia as a maritime fuel.
• Unlike renewable carbon-based fuels, the supply of green ammonia feedstocks is limitless.
• No SO_X, CO₂, or particle emissions are produced when ammonia is used in an internal combustion engine. When catalytic (SCR) technology is used, N₂O/NO_X emissions are reduced to extremely low levels, leaving a nitrogen and water exhaust.
• Ammonia does not accumulate since it is digested in the environment.
• It is easily liquefiable by either cooling it to 33°C at air pressure or compressing it to 0.8 MPa at 20°C.
• With an annual global output of 180 million tonnes, there is already a well-established and dependable infrastructure for ammonia production, storage, and transport.
• Since its flammability range is quite small, it can be securely stored onboard.
• Ammonia can be utilized in internal combustion engines with little adjustments. It can be employed directly in fuel cells due to its high-octane rating (120 compared to gasoline, which generally varies from 86 to 93).

In theory, renewable energy sources such as solar and wind power can replace a sizeable portion of the fossil fuels used worldwide. Wind turbines and solar panels can gather these sources. However, these renewable energy sources do not have enough energy production potential.

There are five distinct production routes for green ammonia (Figure 1). The majority of routes begin with the synthesis of renewable hydrogen. The Haber-Bosch synthesis method combines renewable hydrogen generation methods in the first three routes (1 to 3). Pathway 4 integrates a renewable hydrogen generation method with a novel synthesis technique, whereas Pathway 5 does not need a separate hydrogen production phase.

Figure 1: Production routes of green ammonia [6]

Green vs. Conventional Ammonia

Conventional and green ammonia have drastically different carbon dioxide (CO₂) footprints; however, the actual product is the same. From a practical standpoint, ammonia used as a maritime fuel might be conventional, green, or any combination of the two. This fact dramatically reduces any risk associated with purchasing a ship that burns conventional ammonia as fuel since it is a commercial chemical sold in huge volumes. An owner of a ship may begin using regular ammonia. Future economic conditions, laws, regulations, and the necessity or desire to support more environmentally friendly and carbon-neutral transportation can influence how much green ammonia is blended in.

Conventional Ammonia

The most common fossil fuel used to make conventional ammonia is coal, and it can also be natural gas. The efficiency of the facility and the feedstock affect the CO₂ footprint. Modern, extremely efficient ammonia plants can produce as little as 1.6 tons of CO₂ every ton of ammonia, while older facilities normally produce closer to 2 tons, and coal-based plants can produce as much as 3 tons of CO₂ each ton of ammonia.

Blue Ammonia

Blue ammonia is synthesized similarly to conventional ammonia with the exception that the CO₂ is absorbed, liquefied, and transferred to a long-term storage facility, or CCS.

Green Ammonia

Green ammonia, also known as renewable or sustainable ammonia, is generated only using clean, renewable sources of power, air, and water rather than fossil fuels. Initial projections of the life-cycle emissions reductions for green ammonia are >90% for ammonia powered by wind energy and >75% for ammonia powered by photovoltaics. The reduction will grow over time as the life cycle emissions from renewables fall as more renewable energy is used to manufacture photovoltaics and wind turbines.

Hybrid Green Ammonia

Hybrid plants that use fossil fuel and renewable electricity to power their operations synthesize hybrid green ammonia. Such a facility can be a newly constructed hybrid facility or a modernization of any conventional facility. The latter is intriguing since it offers a commercially viable switch to the generation of green ammonia.

Table 2: Comparison of the expected effectiveness of different ammonia production techniques [6]

Process Type	Expected Efficiency [up to]
Pathway 1 Haber-Bosch and electrolysis synthesis	around 72%
Pathway 2 Solar hydrogen production	9% [up 70%]
Pathway 3 Biogenic hydrogen production	around 57%
Pathway 4 Non-thermal plasma process	12-37% [up to 45%]
Pathway 5 Electrochemical process	14-62% [up to 90%]

Ammonia Transport to End-User

Ammonia is carried in large volumes worldwide using pipelines, ships, trains, and roadways. Anhydrous ammonia is a harmful item that should be carried out following the law. It must be appropriately identified and handled since it is considered a dangerous gas.

Public Roads

People who carry hazardous materials on public highways are required to undergo training and possess a current training certificate. Anhydrous ammonia is not explicitly addressed in most training programs for carrying hazardous materials. However, the business has its own training program for drivers and other transporters of ammonia.

Railways

In Europe, yearly ammonia transportation amounts to 1.5 million tons, or over 30,000 rail tank cars. Over the past 30 years, just a few accidents have happened, and none of them caused any fatalities due to the ammonia discharge [7].

Shipping

Currently, 170 ships can transport ammonia as cargo [8]. Actions against leaks, firefighting techniques, gas freeing, ballasting, cargo transfer protocols, cargo cleaning, the lowest permitted temperature for steel in the cargo tank, emergency protocols, and crew training are only a few of the general safety precautions for liquid gas carriers. Specifically, the ship needs hazardous vapor detection for anhydrous ammonia.

Pipelines

Ammonia is being delivered in large quantities via pipelines worldwide, mainly in the USA and Russia/Ukraine. The majority of these pipes pass through busy streets or densely inhabited regions. Leaks from pipes have caused a few accidents. Most of these were in the United States, which has the most extensive infrastructure for liquid ammonia pipelines. There have been a few cases in the USA, but none have resulted in death [9]. Safety considerations include hazardous goods labelling, adequate vessel maintenance, loading and unloading regulations, protective equipment, and emergency response protocols [7].

Around 80% of the ammonia produced worldwide is used to make fertilizers, primarily urea or various grades of ammonium nitrate. You can also spray fields with liquid ammonia. In the agricultural industry, liquid anhydrous ammonia is transported, stored, and handled in pressurized tanks. Manual tasks such as joining and detaching pressurized vessels and transporting the pressurized tank equipment are part of the equipment handling. The majority of ammonia accidents are brought on by errors like overfilling the tank, opening the valve by accident, rupturing the transfer hose, neglecting to bleed the hose connection before disconnecting, or otherwise disregarding protocol or failing to maintain equipment.

Ammonia vs. Other Marine Fuels

Below is the Table that combines the most crucial characteristics of ammonia with other marine fuels.

Table 3: Ammonia vs. other marine fuels

	Boiling Point	Pressure for storage (20 °C)	Liquid mass density (15°C)	Lower Heating Value	Energy Density	CO2 produced in the combustion
	[°C]	[bar g]	[kg/m3]	[MJ/kg]	[MJ/L]	[kgCO2/GJ]
Hydrogen	– 253	—	71	120	8	0
LNG	– 162	—	450	50	22	56
LPG	– 42	7.5 (min)	550	46	25	60
Ammonia	– 33	7.6 (min)	618	18	12	0
Methanol	65	ATM	780	20	15	70
HFO	>160	ATM	920 – 1010	40	35	80

The standard reference fuel in the maritime sector is heavy fuel oil (HFO). HFO is not in compliance with the worldwide “sulfur limitation” that went into effect in 2020 and calls for even more stringent limits on SOx emissions since it contains 3.5% sulfur. Instead of installing an exhaust gas cleaning system to remove SOx, shipowners have started exploring alternatives to standard HFO in recent decades. SOx emission rules can be met by using low-sulfur fuel oil with no more than 0.5% sulfur. Due to the concurrent advancement of marine diesel engine technology, LPG, methanol, ethane, and LNG have been used as an alternative for maritime propulsion.

In recent years, sulfur-free methanol has become a viable alternative marine fuel to comply with sulfur emission rules. Methanol can be handled and used as fuel in dual-fuel, two-stroke diesel engine ships using well-established technology.

The quantity of CO₂ produced by burning methanol is comparable to that of other hydrocarbon-based fuels. Methanol is a viable carbon-neutral alternative that can be produced using renewable energy and bio-based carbon, but it is a scarce resource with a consequently anticipated rise in market price.

Another alternative fuel for shipping that got attention recently is LNG, primarily because of the IMO 2020 sulfur restriction. The energy density of LNG is greater than that of ammonia. Ammonia can be kept at atmospheric pressure and a chilled temperature of -33°C, while LNG still needs cryogenic storage conditions (-162°C). Hydrogen is a fuel that can be generated sustainably and is free of sulfur and carbon. However, as compared to ammonia, hydrogen has several drawbacks when used specifically in the maritime sector.

LPG and ammonia can be kept under comparable temperature and pressure settings. Ammonia has a lower vapor pressure than 10 bar g at 20°C, similar to LPG. Ammonia and LPG can be maintained onboard in type-C tanks to retain their liquid state at higher ambient temperatures. Similar to LPG, ammonia can be kept chilled and at a pressure close to atmospheric conditions. In this scenario, the key benefit over hydrogen and LNG is that ammonia refrigerated storage temperature (-33°C) is significantly higher than LNG and hydrogen cryogenic temperatures (-162 to – 253°C).

Toxicity and Safety Aspects of Ammonia

When contemplating the potential use of ammonia as a maritime fuel, several problems can surface. Ammonia safety and toxicity issues are the main problems. Ammonia is a gas with a potent distinctive smell, corrosive and barely combustible. Ammonia has an odor threshold of 5 to 50 parts per million (ppm) of air. The human body does not experience any long-term repercussions from repeated exposure to ammonia. However, it can irritate the eyes, throat, and breathing passages even at low air concentrations.

Today, it is prohibited to fuel a ship with commodities classified as harmful goods. The International Code of Safety for Ships Using Gases or Other Low-flashpoint Fuels (IGF Code) section has to be partially amended. The possibility of a significant discharge of ammonia into the environment in heavily populated port regions must also be re-considered for ammonia transporters.

Table 4. CO₂ and air pollutants from ammonia and other marine fossil fuels [6]

Pollutant	HFO, Marine gas oil (MGO)	LNG	Ammonia (combusted in engines)
SO2 and metallic content	Present	Not present	Not present
Carbon monoxide and hydrocarbons	Present	Present	Not present
VOCs and PAHs	Present	Low	Not present
NOx	Needs SCR for Emission Control Area (ECA)	Otto engines meet ECA without SCR	Needs SCR for ECA
Direct particulate matter	Present	Low	Low
Ammonia (NH3)	Low	Not present	Unknown
N2O	Present	Present	Present/High
CH4	Low	Present at Otto engines	Not present
CO2	Present	Present	Not present

Ammonia as a Fuel

Since the shipping industry has never utilized ammonia as a fuel, new systems will be needed onboard, each with its own unique requirements and dangers. The technology, materials, and methods are already in place and simply need to be modified and enhanced for this particular use. Considering the industry’s experience with other alternative fuels, such as LNG and methanol, will be beneficial.

Ammonia appears to be more appropriate for large and professional users than for smaller ones, like trucks and private vehicles, under a general case of diverse businesses striving to ensure the supply of carbon-neutral or carbon-free fuels. The storing and bunkering of ammonia on board, how this fuel affects the engine room and engine function, and some safety considerations will all be taken into account as we evaluate the use of ammonia as a fuel for ships.

Bunkering and Storage of Ammonia Onboard

The most simple example is a ship delivering ammonia as cargo. Our prior experience with methanol, LNG, and LPG tells us that these vessels will be the first to use it as fuel. The ship’s adaption will likely be confined to the necessary engine upgrades and installing a specialized NH₃ fuel supply system. In this situation, extra care should be taken to prevent any potential cargo contamination brought on by engine pollution.

The procedures to bunker the product and the availability of ammonia for engine fuelling do not affect these vessels.  The experience with methanol or LNG, whose handling is more comparable to that of ammonia (no cryogenic technology, no boil-off to dispose of and use as fuel), demonstrates that the ship can be run for almost 100% of the time with the alternative energy source and reduces expenses.

The infrastructure for loading and storing ammonia onboard must be implemented even if a ship is not transporting it as cargo. The IGF code is anticipated to control their construction and safety as well as provide instructions for the secure loading, storing, and operating of the entire onboard ammonia system.

A type C pressurized tank appears to be the most economical option for storing ammonia on ships with limiting routes and installed power. This tank does not need a reliquefication system because it can hold the product at room temperature. The type C tank is also an adaptable installation on the deck and is simple to include in the overall design of a commercial ship. The type C tank’s anticipated upper limit of applicability is 2000m³.

There are already ammonia import and export facilities at 120 ports across the world. To increase ammonia availability fast, ship-to-ship bunkering—in which the ammonia is supplied by another ship or barge parked alongside the receiving vessel—and enhanced bunker hose handling will be necessary. This approach can also be used for LNG because it requires less capital outlay for infrastructure and offers variable fuel delivery.

Theoretically, ammonia bunkering might take place concurrently with cargo loading and unloading operations. But this must be permitted by the port authorities. If not, the ship will raise costs from the extra time spent at the port.

Scaling up Ammonia Production for Shipping

In the future, a total of 330 million tons of ammonia will be needed to supply 30% of the present marine fuel use. This is an increase from the current output of 180 million tons. In 30 years, an additional 150 million tons should be produced. Renovating both new and old facilities might add this extra capacity.

Renovating existing ammonia facilities with modern compressor and reactor technology will easily provide 25% more ammonia synthesis capacity. This would add 25% to the existing 180 million tons of capacity, giving the world a total capacity of 225 million tons. Then, extra 105 million tons of ammonia would need to be produced by new facilities in order to reach the number of 330 million tons needed to fulfill current world demand plus the marine fuel business.

Most of the extra capacity provided by updated and new facilities is anticipated to be based on environmentally friendly hydrogen production using electrolyzers and renewable energy sources. With very slight adjustments, plants can progressively transform into hybrids, starting at a small percentage and gradually growing to about 10%. If we want to go over 10% green, we will need to change the ammonia plant’s heat integration, which costs more capital.

Hybrid ammonia plants can be built in the future with capacities greater than twice as large as current plants. Another option for new plants is 100% green ammonia. Some of the ammonia plants chosen for hybrid refurbishment can be ones situated in regions with a high penetration of renewable energy production. The plant might synthesize green ammonia under high solar and wind output with low conventional power demand in power networks since those are the times when the cost of electricity is lowest.

The manufacturing capacity for electrolyzers, which is now at a relatively low level since the demand is similarly low, has been identified as the bottleneck. As a result, it makes sense to start producing green ammonia by converting current ammonia plants into hybrid plants by adding one electrolyzer and then progressively adding more. Thus, the need for electrolyzers ought to increase. Since the most often mentioned technology has been well-tested over decades and does not require any rare materials, there is no reason to think that the manufacturing capacity for electrolyzers cannot be increased. In reality, this scale-up is already in progress as providers of electrolyzers make significant investments to boost capacity.

Figure 2: Maritime energy demand and fuel mix projections to 2050 [10]

Ammonia as a Marine Fuel

Ammonia Fuel Land-based Challenges

The carbon emissions produced by the ship’s engine and auxiliary systems are frequently the subject of discussion. However, significant pollution is produced along the fuel supply chain, from extracting energy sources through gasoline production to transporting and storing fuel at the port. The shipping sector needs to consider the full supply chain to prevent just passing the responsible upstream.

According to research conducted in 2020 by University Maritime Advisory Services (UMAS) and the Energy Transitions Commission, the IMO’s goal of reducing carbon emissions by 50% by 2050 will cost between $1 and $1.4 trillion [11]. The report also revealed that over 87% of the needed investment is for land-based infrastructure and manufacturing plants for low-carbon fuels. Since these massive infrastructure expenditures can have far-reaching effects on people and the environment, the upstream difficulties are sometimes more challenging to address.

There is currently a system for transporting ammonia throughout the world, but fuel must be stored and delivered to the appropriate areas in sufficient quantities. Current ammonia transport infrastructure links industrial market production and storage facilities but does not reach ports in a form that facilitates ship bunkering.

Ammonia Fuel Safety

Ammonia is not a highly combustible fuel but extremely harmful to humans at even trace doses (0.25%). The hazards posed by modern distillate and residual fuel oils and even natural gas are far smaller than ammonia. Ship crews, port workers, and fuel suppliers all depend on properly planned, produced, managed, and maintained fuel systems.

Standard layouts for modern ships often place the ship’s engines and fuel systems below decks, where space is at a premium. Ammonia has unique needs, which might force ship designers to make adjustments or perhaps inspire new concepts.

Ammonia ships will need new expertise and safety techniques for handling ammonia. Learning what can go wrong in the event of a leak or accident and what can be done to prevent harm to people, water, and land is essential. The adoption of ammonia will thus necessitate the development of a new safety pathway.

Ammonia Fuel Suitability

Ammonia has been transported as bulk cargo for 100 years, and the dangers associated with this cargo are well-known and addressed. The fuel is widely available, easy to produce, and inexpensive, making it a popular choice for fishing vessels. It was also one of the first refrigerants used onboard.

However, because of safety concerns, a rigorous approach to risk analysis of fuel propulsion systems and handling would be required, and shipping has no experience in using ammonia as fuel. Strict safety regulations need to be imposed all along the supply chain.

Ammonia Fuel Sustainability

In order to minimize adverse effects on the environment, society, and socioeconomic issues upstream in production processes, ammonia manufacturing requires a sustainability system comprised of certification based on rigorous sustainability criteria.

Overall, it appears that ammonia is a promising alternative fuel that has the potential to aid in the decarbonization of marine transportation considerably. Sector stakeholders must now collaborate to develop and validate the viability of workable solutions.

Ammonia Combustion in Engine

Ammonia is a good carbon-neutral or carbon-free fuel alternative. However, there are just a few studies of its combustion in a reciprocating engine. According to the literature, ammonia has a slow flame, a high auto-ignition temperature and a narrow flammability range.

It needs a very high temperature and compression rate to self-ignite, resulting in a large NOx generation. This can be overcome by combining a second fuel with better igniting characteristics (like hydrogen). Alternatively, utilizing a pilot flame to initiate and control the combustion in the cylinder. The latter option appears to be the most simple way to take total control of the procedure. In the maritime industry, dual-fuel engines with a pilot flame have a strong track record. They have several benefits, including dependability, fuel flexibility, and a rapid switch to the primary fuel in the event of secondary fuel problems.

Furthermore, the manufacturers provide the flexibility of upgrading existing engines to this technology, making ammonia conversion viable for ships that are currently in operation.

Ammonia and Engine Ancillaries

The engine room will undergo considerable alterations due to the usage of ammonia as fuel. Some conventional infrastructure, such as the whole HFO treatment (heaters, high-speed separators, settling tank, booster) and the SOx scrubber system for ships utilizing high-sulfur HFO, will no longer be required. On the other hand, dealing with this new fuel requires new systems and a specialized engine, directly affecting capital and operational costs. Here is a list of the primary options:

• Ventilation system for the liquid fuel supply system (LFSS)
• Post-treatment SCR
• Upgrades to a particular engine

Liquid Fuel Supply System (LFSS)

The system that supplies ammonia to the engine under necessary conditions is known as the LFSS. The LFSS can be put on the deck and linked to the engine using a double-walled pipe to reduce the possibility of an ammonia spill in the engine room. It is also feasible to install in the engine room, but only after taking safety steps, such as installing an airlock system to stop any ammonia diffusion in the engine room. The LFSS architecture can vary significantly based on engine technology. It can resemble low-pressure LNG delivery systems for engines receiving secondary fuel in the form of a gas. The solution utilized for LPG on LGIP engines can be employed for engines gaining the secondary fuel at high pressure in the liquid phase with relatively few adjustments.

This LFSS system performs the following tasks:

• Irrespective of the storage conditions, it delivers fuel to the engine at the necessary temperature and pressure
• It separates the fuel from the payload, protecting the latter from potential engine pollution
• When necessary, it can perform the cleansing
• Under safe circumstances, it can recover the product from purging and reducing the atmospheric release.

Summary

Several factors are working in green ammonia’s favor, making it a good option for marine fuel to decarbonize the shipping sector. It has the potential to significantly cut emissions from both the standpoint of air emissions and GHFs because it is inherently carbon-free. Ammonia is known to be a cargo in the shipping sector, offering a solid foundation for further research. The whole supply chain may acquire insight from other industries (fertilizers), as ammonia has been used and delivered onshore for decades, leading to pertinent knowledge on safe handling and transportation works. The methods for producing ammonia are advanced sufficiently to sustain its synthesis. However, the generation of green hydrogen, which is essential for making green ammonia, still has to be scaled up.

However, there are still numerous obstacles and difficulties to be conquered. The first problem still has to do with making green ammonia. Most of the green ammonia production is expected to be utilized for the fertilizer industry. Therefore, it is required to significantly enhance the renewable energy capacity to enable its adoption of ammonia as a maritime fuel. The availability of green energy is viewed as a significant obstacle to the appropriate uptake of green ammonia production since all sectors will be seeking its extended volume. Even if ammonia is made widely available, shipping will still face competition from other industry sectors, such as those that use ammonia often (such as the fertilizer industry) or others that view it as a hydrogen transporter.

Another obstacle is the absence of laws governing the use of ammonia as fuel. Ammonia is a dangerous and caustic gas when used as a fuel, and thus even while this is a valid premise, regulations should still take safety and dependability considerations into account. In contrast to other alternative fuels being considered by the industry, present rules do not lend themselves easily to ammonia as a fuel.

Further research, examinations, and advancements are necessary to understand better and address the safety issues related to using ammonia as a fuel before these laws can be implemented. All interested contributors—class societies, owners, legislators, engine manufacturers, equipment suppliers, port authorities, operators, etc.—should be informed and encouraged to share their experiences.

The study shows that ammonia as a maritime fuel is feasible but that collaboration between businesses and the government in the followings is required to remove the obstacles mentioned above:

• Oversee and increase the usage of renewable energy sources.
• Encourage the development and adoption of decarbonization policies.
• Establishing innovative technologies to increase production effectiveness.
• In IMO, establish a framework for international regulations on the use of ammonia as fuel.
• Promote inter-stakeholder cooperation to address technological and safety challenges.
• Conduct more research to learn about the dangers and difficulties related to safety while utilizing ammonia as a fuel for the shipping sector and how to address them.

References

[1]        Commission, E. T. (2020). The First Wave. A Blueprint for Commercial-Scale Zero-Emission Shipping Pilots. A Special Report by the Energy Transitions Commission for the Getting to Zero Coalition. Energy Transitions Commission: London, UK.

[2]        Balcombe, P., Brierley, J., Lewis, C., Skatvedt, L., Speirs, J., Hawkes, A., and Staffell, I. (2019). How to decarbonise international shipping: Options for fuels, technologies and policies. Energy conversion and management, 182, 72-88.

[3]        Brief History of IMO. (n.d). Retrieved Jan 25, 2023 from https://www.imo.org/en/About/HistoryOfIMO/Pages/Default.aspx

[4]        UN body adopts climate change strategy for shipping. (2018). https://www.imo.org/en/MediaCentre/PressBriefings/Pages/06GHGinitialstrategy.aspx

[5]        Decarbonisation and shipping: International Maritime Organization ambitions and measures. Retrieved November 4, 2020 from https://www.hilldickinson.com/insights/articles/decarbonisation-and-shipping-international-maritime-organization-ambitions-and

[6]        Potential of Ammonia as Fuel in Shipping. EMSA. Retrieved October 18, 2022 from https://www.emsa.europa.eu/newsroom/latest-news/item/4833-potential-of-ammonia-as-fuel-in-shipping.html

[7]        Guidance for transporting ammonia by rail. (2014). F. Europe. https://www.fertilizerseurope.com/wp-content/uploads/2019/08/Guidance_for_transporting_ammonia_in_rail_4.pdf

[8]        Brown, T. MAN Energy Solutions: an ammonia engine for the maritime sector – Ammonia Energy Association. Retrieved January 25, 2019 from https://www.ammoniaenergy.org/articles/man-energy-solutions-an-ammonia-engine-for-the-maritime-sector

[9]        Guidance for inspection of and leak detection in liquid ammonia pipelines. (2019). Fertilizers Europe. https://www.fertilizerseurope.com/wp-content/uploads/2019/08/Guidance_for_inspection_of_and_leak_detection_in_liquid_ammonia_pipelines_FINAL_01.pdf

[10]      Dnv, G. (2020). Energy transition outlook 2020: maritime forecast to 2050. Available here: https://eto.dnvgl.com/2020/index.

[11]      Saraogi, V. (2020). Decarbonising the maritime industry will cost $1tn, study says. https://www.ship-technology.com/news/decarbonisation-in-shipping