Mitsubishi Heavy Industries Technical Review Vol. 59 No. 2 (June 2022)
1"LNG as fuel" to "Ammonia as fuel"(Ship's fuel transition to achieve carbon neutrality)

SHIN UEDA*1

KENJI TSUMURA*2

YUSUKE WATANABE*3

HIROSHI TAMURA*4DAISUKE YAMADA*5

As was the case with the large-scale marine transportation of LNG (Liquified Natural Gas),
the increasing expectations and social demand pressure on the land use of ammonia for electric
power generation as an environmental measure are about to open the era of large-scale marinetransportation of ammonia. The technologies for LNG carriers were applied to ships using LNG as
fuel (hereafter LNG-fueled ships) and LNG fuel supply systems. It is expected that the technologies
for ammonia carriers will be also applied to develop ships using ammonia as fuel (hereafter
ammonia-fueled ships) and ammonia fuel supply systems. To widely promote the use of ammonia
as marine fuel, it is necessary to set up ammonia related rules and training for crews, andammonia-fueled ships and equipment should be developed as the extension of the same technology
from LNG-fueled ships and equipment. In such way, it is desirable for manufacturers who provide
ships and equipment and the potential operators of ammonia-fueled ships to develop in such amanner that common parts are inherited from LNG-fueled ships and equipment.

|1. Introduction
In the initial LNG carriers, steam turbine propulsion plants were adopted as propulsion
machinery so that the risk of vibration impact of the propulsion machinery on LNG tanks was
minimized, and boil-off gas (BOG) from LNG tanks was effectively used as fuel. After that,high-efficiency marine diesel engines which allowed the use of LNG were developed, and theassessment method for vibration impact on LNG tanks and countermeasures were also established.
Then, diesel electric propulsion plants were adopted, and now, most of the current LNG carriers areequipped with plants that allow direct propulsion by LNG-fueled diesel engines. The advent ofmarine LNG-fueled engines paved the way for the utilization of LNG fuel other than LNG carrier.
Many LNG-fueled ships were begun to build and operate, as an environmental measure. It started
in Europe and spreading to other contraries, and the number of LNG-fueled ships has been
increasing along with the growing of environmental awareness. In Japan as well, the number ofcompletions and construction contracts of LNG-fueled ships, which are large merchant ships, isincreasing. Now we have entered the era where we can see the increase of LNG-fueled ships aswell as the improvement of the port infrastructure for LNG supply including LNG bunkering
vessels.
In recent years, however, increasing the sense of crisis over the global environment andclimate change, it has been required at an accelerating pace to take measures for GHG (greenhousegas) reduction and carbon neutrality, and with an eye toward post-LNG fuel, discussions anddevelopment have already been in conducting phase. LNG fuel, which emits CO2 when it burns,
has already been recognized as a bridging solution before carbon neutral fuels, as next-generation
fuels, or ecosystems with CO2 recovery are established. Many concerned parties in maritime affairs*1

Director, Ship & Ocean Engineering Department, Mitsubishi Shipbuilding Co., Ltd.

*2

Director, Strategic Planning & Operation Office, Mitsubishi Shipbuilding Co., Ltd.

*3

Deputy Director. Ship & Ocean Engineering Department, Mitsubishi Shipbuilding Co., Ltd*4Manager, Nagasaki Designing Department, Mitsubishi Shipbuilding Co., Ltd*5

Engineering Manager, Nagasaki Designing Department, Mitsubishi Shipbuilding Co., LtdMitsubishi Heavy Industries Technical Review Vol. 59 No. 2 (June 2022)2

including shipowners, shipping companies, shipyards, marine equipment manufacturers, fuelsuppliers, etc., are interested in the way of the next marine energy supply for ships. The conditions
and backgrounds for energy supply are different by ship type and operation pattern, and it isexpected that ship’s fuels in a variety of segments will coexist in the future. As shown in Table 1,
differently from other candidate fuels, ammonia does not emit CO2 and it has characteristics
suitable for mass transportation and long-term navigation. Therefore, ammonia is recognized as apromising option.
In this report, focusing on the transition from LNG fuel to ammonia fuel, we predict howammonia as fuel will be developed by overlapping the history of the technological conversion from
LNG carriers to LNG-fueled ships and consider the technological continuity from LNG fuel toammonia fuel. And finally, we will look at the way of development of ammonia-fueled ships andammonia fuel supply systems.
Table 1 Characteristics of each ship’s fuelShip’s fuel (CO2emissions per
calorific value)

Carbon-free,carbon-neutral
fuel that allows
diversion of
infrastructure

Heavy oil (1.0)

Biodiesel

LNG (0.74)
Methanol (0.90)

Carbon recycled
methane,biomethane
Carbon recycled
methanol,biomethanol

Ammonia (0)Greenammonia, blue
ammonia

Hydrogen (0)Greenhydrogen, bluehydrogenFuelliquefaction
conditions
Atmosphericpressure, room
temperature
Atmosphericpressure,-162℃
Atmosphericpressure, room
temperature
Atmosphericpressure, -33℃
or 1.8 MPaA,
room
temperature
Atmosphericpressure,-253℃

Fuel volume percalorific value

Suitability for
masstransportation,
long-termnavigation

Base

Suitable

x 1.7

Suitable

x 2.4

Suitable

x 2.7

Suitable

x 4.5

Possible|2. Social trends toward carbon neutrality and its impact on themaritime industry
2.1

Roles of LNG and ammonia in achieving carbon neutrality

Most of countries have set GHG emissions reduction targets for 2030 and ambitious goals forachieving carbon neutrality by around 2050. The world is moving toward the realization of carbon
neutrality. In various fields, solutions for proliferation of renewable energy, CO2 reduction and CO2
capture has been promoted.
Even in the era of fossil fuel energy as the mainstream, there is the demand for transportation
because oil-producing areas and energy demand areas are located apart, and these demands havebeen satisfied by pipelines and/or ships. As shown in Figure 1, suitable areas of renewable energy
resource and the areas of energy demand are also located apart. Although the supply chain haschanged in the carbon neutral energy, there is still substantial demand for transportation of carbon
neutral energy. Especially for long-distance routes, transportation by ship is advantageouscompared to developing pipelines or power grids. In the transition period from fossil energy tocarbon neutral energy, it is necessary to cope with changes in destination and transportation volume
and a new balance between both energy segments. In this transition period toward the realization ofa carbon neutral society, these changes in fuels as energy transport media and energy transportation
demand will continuously occur. Therefore, ships - that can provide mass transportation andlong-distance transportation of energy and can give flexibility in transportation routes - play animportant role in this transition period.
Major carbon-neutral energy transport media include hydrogen, ammonia, synthetic methaneand synthetic methanol. Hydrogen-based energy transport requires infrastructure and technologies
at every stages from production through utilization, and it takes time for the system to spread.

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Among the fuels for stepwise realization of carbon neutrality, ammonia is garnering considerable
attention as a promising energy transport medium because it does not contain carbon and can beproduced only from nitrogen and hydrogen existing in the atmosphere, and the synthesis
technology for ammonia has already been established.
Another possible measure is CO2 capture-based energy transportation using synthetichydrocarbon together with CO2 capture after combustion. Synthetic methane and synthetic
methanol using captured CO2 become carbon-neutral energy transport media. From the viewpointof effective utilization of the existing infrastructure, a transition from LNG to synthetic methane isalso considered to be a superior option.

Figure 1

2.2

Locations of renewable energy resources and energy demand areas

Trend of regulations and effects on ship operation

The International Maritime Organization (IMO) adopted a strategy on the reduction of GHG
emissions in April 2018 and set a medium-term target of reducing the total GHG emissions frominternational shipping by 50% by no later than 2050 compared to 2008 levels and a long-termtarget of achieving net zero emissions as early as possible in this century. At the IMO Marine
Environment Protection Committee (MEPC) held in June 2021, the Energy Efficiency Existing
Ship Index (EEXI) regulation for verification by the design parameters of ship fuel efficiency andthe Carbon Intensity Indicator rating (CII rating) for post check of actual fuel efficiency wereadopted and will come into force in 2023. Concerning the CII rating, it has been decided that the
rating thresholds for GHG reduction will become more stringent every year so that the reduction
rate will be increased by 1 to 2% per year until 2026, and from 2027, it will be further increased
although no specific numerical value has been decided. Each ship will be rated on a five-tiered
scale (from A to E). If a ship receives a rating of D, which is the fourth level, for three consecutive
years or receives a rating of E, which is the lowest level, an improvement plan must be developed
and there will be no choice but to take measures such as fuel conversion or slow steaming. This
regulation will require ships that have poor environmental performance to be modified or to reduce
the transportation capacity, and it will have a great influence on market. Viewing from the opposite
side, this rating indicating environmental performance may be regarded as providing us an
opportunity. It is possible to promote positive development of ships adapting to next-generation
fuels and show them to environmentally conscious shipper companies and consumers. There is apossibility that the CII rating will be utilized as an indicator of environmental performance of the
fleet.
LNG fuel can reduce CO2 by about 25% compared to heavy oil and even now it is anavailable fuel. Therefore, the use of LNG fuel is effective solution in improving the rating quickly.
Ammonia fuel is expected to contribute to a substantial improvement in CO2 reduction as acarbon-free fuel and it can be used as an effective means for further reducing GHG. Therefore, thefuel conversion from LNG fuel to ammonia fuel has been also studied.

Mitsubishi Heavy Industries Technical Review Vol. 59 No. 2 (June 2022)
4|3. LNG fuel3.1

Dawn of the era for land use and the large-scale marine transportation of LNG

Natural gas contains less pollutants such as sulfur and its calorific value is high. Therefore, it
got an attention as a source for city gas. By pipeline transportation, the large-scale use of natural
gas started in the United States before World War II and in Europe and Russia after the war. In
these early days, LNG, which is produced by liquefaction of natural gas, was not suited to marinetransportation because of the difficulty in handling, but in the 1970s, the transportation of LNG byship became possible, which allowed long-distance transport of LNG, and Japan could thus start
the large-scale use of LNG in land.
Japan industrialized after the war, using coal and then petroleum as energy sources. But it
was accompanied by environmental problems due to serious air and water pollution by them. As acountermeasure, the use of natural gas, which is a clean energy resource, was studied, and Tokyo
Electric Power Company and Tokyo Gas Co., Ltd imported LNG from Alaska, which became thestarting point of the import of LNG by Japan. Then, large scale marine transportation of LNG
began and became worldwide. The oil shocks gave a boost to the use of LNG, resulting in a
substantial increase in transportation volume.

3.2

LNG carriers

After that, LNG carriers have achieved significant technological innovation. For example,
membrane-type LNG containment systems and subsequently moss-type LNG containment systems
appeared, which has created a competitive situation for multiple technologies in LNG carriers. Bothcontainment systems have achieved a high level of success in technological and safety aspects.
Then, various marine LNG technologies such as on-board re-liquefaction systems were developed,
and the hull size was increased. Thus, technological innovations including manufacturing
technologies have been greatly developed up to the present date. Now that the increase in hull size
has reached a certain point and hull forms standardized, then now LNG carriers are considered tohave reached a level of technological maturity.
Propulsion machinery for LNG carriers has developing history of unique technologicalevolution. In LNG carriers, it is necessary to deal with boil-off gas generating from cryogenic LNG
during transportation, and gas treatment is required to control an increase in LNG vapor pressure.
Therefore, for the purpose of economically utilizing boil-off gas, LNG is mainly used as propulsion
fuel. In the early stage LNG carriers, steam turbines were used for propulsion plants, andsubsequently, reheat steam turbines, electric propulsion by medium-speed gas-fueled generator
engines, low-speed gas-fueled diesel engines, etc., were adopted. With the improvement of fuelefficiency, many technological changes have been made. LNG carriers require cryogenic
technologies specific to their LNG containment system types as well as technologies different fromthose for other ships from the aspect of fuel use, and also require shipbuilder’s engineers and ship
operator’s crew that have gas handling skills from the aspects of ship building and ship operation.

3.3

LNG-fueled ships

Now that marine LNG-fueled engines become widely available, the technologies for special
turbine propulsion plants are not required in ship design and construction and not only for LNG
carriers but it has become easier to construct LNG-fueled ships than before. In addition, the marinetransportation of LNG has spread and the infrastructural support for use of LNG fuel is being
established at many ports throughout the world. Therefore, the application of LNG-fueled ships isincreasing. LNG bunkering vessels for supplying LNG as fuel to commercial ships are being
completed one after another at various ports throughout the world, including in Japan. Concerns about
LNG supply to ships are being dispelled and the conditions for introducing LNG fuel to commercial
ships become better. In order to supply LNG fuel to an engine, a system for preparing LNG to thetemperature, pressure and flow rate specified by the engine is required and the system also needs tohave a function of maintaining LNG in fuel tanks in a correct state. Such a complex fuel supply
system (LNG-FGSS: LNG-Fuel Gas Supply System) will be required for LNG-fueled ships. Each
manufacturer has already developed such a system based on the technologies for LNG carriers andestablished the system for supplying related devices as one package. The environment has been
established in which shipowners and shipyards do not need to design or procure individual devices

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but can use a reliable system as a package. Mitsubishi Shipbuilding Co., Ltd. started early thedevelopment and commercialization of the LNG-FGSS and provides a lineup of products. Largecommercial ships using LNG as fuel are increasing because they are economically feasible, andmedium-sized ships using LNG as fuel are expected to progressively increase. It is also expected thatwith the increase in LNG-fueled ships, LNG bunkering vessels will come into wide use and the fuelsupply systems will be enhanced in the future. The problem to be noted is that the global warming
potential of methane is 28 times greater than that of CO2. It is important to continuously study
reduction of unburned gas emissions from LNG-fueled engines and take measures to prevent release
into the atmosphere in the processes of production, transportation and bunkering.

|4. Expectations for ammonia fuelAmmonia can be synthesized mainly from hydrogen produced by the electrolysis of waterusing renewable energy (green hydrogen) or hydrogen produced by the decomposition ofhydrocarbon (blue hydrogen) and nitrogen existing in the air via a catalytic reaction at hightemperature and high pressure (Haber-Bosch process). Since no special material for fuel is used forits production, ammonia can be produced easily in energy supply areas. At present, the global
ammonia production capacity is not sufficient relative to the expected energy demand, but it isconsidered that there are no major problems regarding the raw material supply chain for fuel.
Ammonia can be decomposed to extract hydrogen and it can also be directly combusted. In
addition, ammonia is a zero-carbon fuel which does not emit CO2 when burned. Therefore, it iseffective at reducing CO2 emissions from thermal power generation, industrial furnaces, ships, etc.,
and in Japan, like LNG, ammonia is considered as energy source in these infrastructuraldevelopments. In thermal power generation, there are high expectations for the effect ofsignificantly reducing CO2 emissions by using only ammonia as a fuel. Ammonia is also suitable
for mixed combustion with coal, and it is expected that early realization of such mixed combustion
will contribute to the stepwise reduction of CO2.
The liquefaction temperature of ammonia is relatively high compared to that of LNG.
Ammonia liquefies when pressurized at room temperature and it has characteristics closer to LPG(liquefied petroleum gas) than LNG. However, from the viewpoint of corrosiveness and irritation,ammonia is more difficult to handle than LPG. Considering the irritation of high concentrateammonia, differently from LNG and LPG, it is unlikely that ammonia will be used for city gas. But
ammonia has the great advantage of being carbon free and ammonia fuel has sufficient potential
and there are high expectations for use in power generation.
Recently, global environmental awareness has called for actions to be taken on a global
scale, which made a huge impact on the market. It is expected that with growing environmental
awareness, use of ammonia as a fuel for power generation will increase and develop along withimprovement of the infrastructure at ports as was the case with LNG in the past. Probably it willlead to the dawn of large-scale marine transportation for ammonia in the same way as for LNG. For
example, JERA Co., Inc., which is a large-scale Japanese power company, has announced in its“JERA Zero CO2 Emissions 2050 Roadmap for its Business in Japan” that it will start large scale
operation of mixed combustion with ammonia by 2030, achieve 20% of the ratio of mixed
combustion with ammonia in all coal-fired power plants they own in the first half of the 2030s,
subsequently increase the ratio of mixed combustion along with replacement of power plants, andstart single fuel combustion using only ammonia in the 2040s. In addition to coal-fired power
generation, for example, in gas combined cycle power generation, an idea to extract hydrogen fromammonia and co-fire it with natural gas is being considered. (In addition to the use of ammonia, theuse of liquid hydrogen and methylcyclohexane as hydrogen transport media has also been studied.)
To popularize the mixed combustion with ammonia and stably supply ammonia forcoal-fired power generation, the Public-Private Fuel Ammonia Promotion Council under the
Ministry of Economy, Trade and Industry has set the target of achieving the annual ammonia
transportation volume to Japan of about 3 million tons (which is about 126 voyages of MGC (Multi
Gas Carrier)-class vessels having a capacity of 35,000m3) by 2030 and about 30 million tons
(which is about 510 voyages of VLGC (Very Large Gas Carrier)-class vessels having a capacity of
87,000m3) by 2050.

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Ammonia as ship’s fuel is a gaseous fuel having special characteristics, like LNG, and forbuilding and operating of ammonia-fueled ships, high-level technologies and high-level safety are
required. An issue to be noted is that NOx and N2O are generated when ammonia is burned. The
global warming potential of N2O is 265 times higher than that of CO2. Therefore, the developmentof measures to reduce such emissions by engine combustion control and decomposition catalysts
will be promoted. Furthermore, in the case of ammonia is produced using hydrocarbon, CO2 isemitted during production. Therefore, an appropriate treatment such as CO2 capture and storage
will be needed.

4.1

Ammonia carriers

Ammonia carriers have been constructed in the context of LPG carriers because LPG has
similar physical characteristics to ammonia. MHI constructed eighty-eight VLGCs and MGCs fromthe 1960s to the 2020s. Among them, six carriers are MGCs (with a capacity of 20,000m3 to
40,000m3) capable of carrying ammonia (Figure 2). They were constructed in the period from1995 to 2005. At that time, heavy oil was used as the fuel for propulsion, but those carriers were
designed so that ammonia could be transported as cargo. With consideration given to thecharacteristics of ammonia, the carriers are equipped with various monitoring and safety devices in
addition to the cargo equipment suitable for all kinds of ammonia handling operations, such as
preparatory operations for loading of ammonia (i.e., tank inerting, gassing up and cooling down),
loading/unloading of ammonia and preparatory operations for dry-docking (i.e., ammonia tankwarming up, inerting and aeration).

Figure 2

MGC ammonia carrier with capacity of 20,000m3 to 40,000m3

On the other hand, recently, in view of future demand for ammonia transportation, it isrequired that larger VLGCs (corresponding to MHI’s 87,000m3-class) should have specifications
that allow transportation of ammonia. In the project where Namura Shipbuilding Co., Ltd. isconstructing a ship for Mitsui O.S.K. Lines Group (Figure 3), Mitsubishi Shipbuilding Co., Ltd.
provides the design and will conduct procurement of some equipment as well as construction
support. In this project, Mitsubishi Shipbuilding Co., Ltd. has used the knowledge and experienceobtained through the construction of VLGCs and MGCs to increase the economic efficiency by
upsizing cargo tanks and also increase the fuel efficiency by improving the hull form. In addition,using the gas handling technology cultivated so far, we have introduced a system that allows LPG,
which is a cargo, to be used as fuel for the propulsion of the ship. By holding LPG as fuel in the
cargo tanks, flexibility during cargo handling at LPG terminals has been ensured. It has now thelargest-scale specification for an ammonia-loadable ship. Furthermore, in another project,
Mitsubishi Shipbuilding Co., Ltd. has started the development of a large ammonia carrier using
ammonia as fuel in cooperation with Mitsui O.S.K. Lines, Ltd. and Namura Shipbuilding Co., Ltd.
(Figure 4), and takes charge of the study and preliminary design of optimal cargo tanks,development of deck tanks, study of engine and related machinery systems, installation design offuel supply systems, design of special equipment and cargo handling equipment and design ofsafety systems onboard.
As described above, technological preparations for marine transportation of ammonia arenearly completed. From now on, total optimization including upsizing of ships will be promoted
according to growing demand. As was the case with LNG carriers in the past, it is expected that thelarge-scale use of ammonia as ship’s fuel will start with ammonia carriers. Ammonia carriers haveMitsubishi Heavy Industries Technical Review Vol. 59 No. 2 (June 2022)
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facilities and safety equipment for holding and maintaining ammonia as cargo, and they do not
require any infrastructure for the fuel gas receiving such as bunkering vessels. Also, the skill ofcrews has been ensured for ammonia operation. Therefore, it is expected that the use of ammonia
as ship’s fuel will start with ammonia carriers.

Figure 3

87,000m3-type LPG-fueled large LPG/ammonia carrier

Figure 4

Image of large ammonia carrier

4.2

Ammonia-fueled ships

Plans for marine transportation of ammonia are underway. Meanwhile, several engine
manufacturers have already started the development of ammonia-fueled marine engines; the firstammonia-fueled marine engine is expected to make its debut around 2024. In some cases,
ammonia-fueled engines are developed based on the technology for LNG-fueled engines, and theirdevelopment speed is faster than that of LNG-fueled engines. Therefore, ammonia-fueled engines are
expected to be introduced into ammonia-fueled ships at a relatively fast pace. For the supply ofammonia fuel to engines, an ammonia fuel supply system is required which prepare the temperature,pressure and flow volume of ammonia while operating and maintaining fuel tanks, and furthermore,ammonia-fueled ships need to have facilities and safety equipment for holding and maintaining
ammonia like those of ammonia carriers. That is, as with ammonia carriers, ammonia-fueled ships
require preparatory operations for loading of ammonia, loading of ammonia/supply of fuel andpreparatory operations for dry-docking. It is desirable that these operations should be developed using
the technologies for ammonia carriers and fuel supply systems and be provided as a reliable package
as happened with LNG-fueled ships. Mitsubishi Shipbuilding Co., Ltd. considers it desirable toprovide such a package as an ammonia fuel supply system to shipyards and shipowners (Table 2). To
widely promote the large-scale use of ammonia as marine fuel, it is also necessary to set up ammonia
related rules and training for crews, and ammonia-fueled ships and equipment should be developed as
the extension of the same technologies from LNG-fueled ships and equipment and potential operatorsof ammonia-fueled ships to develop in such a manner that common parts are inherited from
LNG-fueled ship and equipment.
Since ammonia fuel is stored at a low temperature or high pressure, it must be handled in the same
way as gas fuel, as is seen with LNG fuel. In addition, it must be noted that ammonia fuel has
corrosiveness and irritation, and ammonia abatement technology in addition to LNG-FGSS technology
will be required. For example, treatment of a small amount of ammonia that is emitted at the interval ofan engine stopping and fuel switching, or treatment of the ammonia that is emitted from fuel tank at thetime of gas freeing prior to docking also needs to be considered. Facilities and equipment that allow safe
operation for such purpose are also required for an ammonia fuel supply system.

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Table 2Ammonia fuel supply system packages

Example of ammonia fuel supply system package
Ammonia fuel tank
Ammonia boil-off gas treatment
device/re-liquefaction device
Instrumentation equipment for ammonia fuel tank
Emergency shutoff device for ammonia fueltank/bunkering
Ammonia fuel supply equipment
Ammonia fuel pump
Instrumentation equipment for ammonia fuel supply
Ammonia abatement device

Example of LNG fuel supply system package
LNG fuel tank
LNG boil-off gas compressor
Instrumentation equipment for LNG fuel tank
Emergency shutoff device for LNG fueltank/bunkering
LNG fuel supply equipment
LNG fuel pump
Instrumentation equipment for LNG fuel supply-

Example of requirements for ammonia abatement equipment
Treatment of boil-off gas from ammonia tank
Treatment of purge gas in fuel piping
Treatment of leaked ammonia gas
Treatment of gas in ammonia fuel tank at the time of regular inspection|5. Transition from LNG-fueled ships to ammonia-fueled ships
There is an already developed marine transportation network for LNG and its convenience will
increase along with completion of LNG bunkering vessels. Since it takes time to establish supply andmarine transportation systems for other alternative fuels, the relative superiority of LNG fuel is
expected to continue longer. LNG is expected to support worldwide development as an effectiveenergy medium option, such as a fuel, a material for synthetic fuels and a hydrogen carrier. It is also
considered that ships involved in the transportation of LNG will continue to use LNG fuel.
On the other hand, for conservation of the global environment, we need to continuously
pursue the reduction of GHG emissions. In connection with the previously described CII rating, atsome point in the future, each ship will be required to reduce emissions beyond the use of LNG,
which is a kind of fossil fuel. Depending on the future reduction target in CII rating, we will needto incorporate measures, such as use of synthetic methane, carbon offset charge or conversion into
ammonia-fueled ships, into planning before the end of the service life of ships. Whether
ammonia-fueled ships will be introduced or not depends somehow on the infrastructuredevelopment progress including the ammonia fuel supply capacity and the shipbuilding capability
for ammonia fuel. Also, it may take time to see the real effects on market of ammonia-fueled ships
depending on the timing when the ammonia fuel becomes widely used. One of the factors that will
promote use of ammonia as fuel for ships is the wide use of ammonia as fuel for power generationon land, and it is considered that large-scale utilization of ammonia as fuel will probably start withammonia carriers. This is like the way of LNG, which became widely used as ship’s fuel.
Now, one of our prime concerns is when the use of carbon neutral fuels will get in largescale stage. It is difficult to forecast the time because there are various elements to be consideredsuch as fuel supply capacity and cost, availability, supply of engines, supply of other equipment,
availability of skilled shipyards and training support of crew. Therefore, to secure flexibility in ship
operation, ammonia-fuel-ready LNG-fueled ships have emerged as a new option.
Ammonia-fuel-ready LNG-fueled ships are LNG-fueled ships that have designs and equipment touse ammonia as fuel partially incorporated when they are newly constructed, aiming at switching
the main fuel from LNG to ammonia during ship lifetime. Before the main fuel is switched from
LNG to ammonia, retrofit modification is required, but as it is originally planned, the modification
cost can be reduced. Also, the modification timing can be decided after the ship is in service.
Therefore, a decision will be able to make based on the comparison of the market of LNG fuel andammonia fuel in the future. The points on planning of ammonia-fuel-ready LNG-fueled ships are asshown in Table 3.
To operate ammonia-fueled ships, it is also important to secure capable crews. As previously
described, ammonia-fueled ships require preparatory operations for loading of ammonia,
loading/supply of ammonia and preparatory operations for dry-docking. If crew’s familiarity with

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handling of gas fuel are secured in advance, those operators can be quickly dealt with. In thisregard, it is also considered important to plan with a view to transition from LNG fuel to ammonia
fuel. From the standpoint of shipyards, consideration should be given so that the ammonia fuelsupply system is designed to have continuity with the LNG fuel supply system; in other words, theammonia fuel supply system/ammonia-fueled ship is designed in such a manner that common parts
are inherited from the LNG fuel supply system/LNG-fueled ship. With such consideration, we
would like to help shipowners and operators securing crews.
Table 3

Points on planning of ammonia-fuel-ready LNG-fueled ships

Points on planning of ammonia-fuel-ready LNG-fueled ships
Fuel tank
Use of materials suitable for both LNG fuel and ammonia fuelSuitability of materials, difference in combustibility/calorific value,
Main engine, auxiliary engine
availability of partial modification, post treatment of exhaust gas
Differences between LNG fuel and ammonia fuel, know-how about
Fuel supply system
handling of gaseous fuelArrangement of tanks, engines and a fuel supply system, fireCompartments/arrangement
protection structure, consideration of flammability/toxicity hazardous
areas
Selection of materials in consideration of corrosiveness of ammonia
Corrosivenessand stress corrosion cracking
Abatement device
Planning on installation of an ammonia abatement device|6. Conclusion
The increase in the demand for LNG for power generation and for city gas due to the rise inawareness of environmental issues brought about the era of large-scale marine transportation of
LNG. In the same way, an increase in the use of ammonia for power generation as anenvironmental measure may open the era of large-scale marine transportation of ammonia. The
wide use of LNG as fuel by commercial ships started from the use of LNG as fuel by LNG carriers.
In the same way, it is expected that the large-scale use of ammonia as fuel, first by carriers and thenby other commercial ships, will expand. The technologies of LNG carriers were applied to
LNG-fueled ships and they were packaged as the LNG fuel supply system. In the same way, it isdesirable that the technologies of ammonia carriers will be applied to ammonia-fueled ships andthey will be packaged as the fuel supply system of ammonia. To cope with environmental
performance targets which are gradually becoming higher, ammonia-fuel-ready LNG-fueled ships
which have an advantage in their operational flexibility are also being planned. For wide use ofammonia as fuel, not only equipment but also capable crews that can deal with ammonia fuel are
required. It is important to prepare for the transition from LNG fuel to ammonia fuel including
personnel training.
Accordingly, Mitsubishi Shipbuilding Co., Ltd. considers that LNG-fueled ships/LNG fuelsupply systems and ammonia-fueled ships/ammonia fuel supply systems are continuous
technologies and that it is desirable to develop them in consideration of continuity in usability. In
the collaborative project (Project MaTIS: Marine Technology, Integration & Solutions) with
Mitsubishi Heavy Industries Marine Machinery & Equipment Co., Ltd., Mitsubishi Shipbuilding
Co., Ltd. is now gathering information from both companies and studying transition from LNG fuelto ammonia fuel.

References
(1)
(2)

(3)

(4)

Hiroshi Morishima, All of the natural gas -The Latest Knowledge of Leading Energy in The 21stCentury-, Oil and Natural Gas Review, January 2004, p.114～169
Agency for Natural Resources and Energy, Ministry of Economy, Trade and Industry, Materials of the 4th
meeting of The Public-Private Fuel Ammonia Promotion Council, (2021)
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