DEPARTMENT OF MECHANICS AND MARITIME SCIENCES

CHALMERS UNIVERSITY OF TECHNOLOGY
Gothenburg, Sweden 2023
www.chalmers.se





MASTER’S THESIS IN MARITIME MANAGEMENT

Techno-economic challenges of alternative fuels in port
operations

A literature review connected to storage, transport & distribution, and bunkering in
the maritime sector

Sten Olsson
Richard Yang

Department of Mechanics and Maritime Sciences
Division of Maritime Studies

Maritime Environmental Sciences



CHALMERS UNIVERSITY OF TECHNOLOGY
Göteborg, Sweden 2023



Techno-economic challenges of alternative fuels in port operations:
A literature review connected to storage, transport & distribution, and bunkering in
the maritime sector
Sten Olsson & Richard Yang

© Sten Olsson & Richard Yang, 2023

Master’s Thesis 2023:NN
Department of Mechanics and Maritime Sciences
Division of Maritime Studies
Maritime Environmental Sciences
Chalmers University of Technology
SE-412 96 Göteborg
Sweden
Telephone: + 46 (0)31-772 1000

Department of Mechanics and Maritime Sciences
Göteborg, Sweden 2023



Techno-economic challenges of alternative fuels in port operations:
A literature review connected to storage, transport & distribution, and bunkering in
the maritime sector
Master’s thesis in Master’s programme Maritime Management
STEN OLSSON & RICHARD YANG
Department of Mechanics and Maritime Sciences
Division of Maritime Studies
Maritime Environmental Sciences
Chalmers University of Technology

Abstract
The maritime sector is in need of decarbonization to lower GHG emissions and to
fulfill goals set by IMO. This thesis analyzes hydrogen, methanol, and ammonia as
alternative fuels to traditional fuels. The purpose of this thesis is to analyze the
selected energy carriers' techno-economic challenges in terms of transportation,
distribution, storage, and bunkering. Based on scientific articles published up until
2023, the primary emphasis according to the reviewed research in this thesis is on
hydrogen, followed by ammonia, and finally methanol. Methodically, this thesis
investigates literature published on the scholarly database Scopus and reviews case
studies in order to comparatively assess the challenges and viabilities of the selected
alternative fuels. Common challenges found in the scientific literature reviewed,
includes lower density than conventional fuels, safety hazards, and redevelopment
costs. Of the three alternative fuels investigated, hydrogen requires the largest storage
facilities, the most significant investments for development, and is the most expensive
to transport. Whereas ammonia benefits from pre-existing infrastructure as it is used
within other sectors. However, both ammonia and hydrogen require special storage
units, and suffer from boil-off, leakage, and need investments in bunkering facilities.
Methanol does not have any special individual challenges and notably, the mean
transportation costs via vessel for methanol is 0,77 USD/GJ/10 000 km which is a
fraction in costs compared to hydrogen at 41,89 USD/GJ/10 000 km and ammonia at
5,71USD/GJ/10 000 km. In conclusion, hydrogen faces the most prominent
challenges, despite the fact that more research is being published than ammonia and
methanol. Methanol has the least techno-economic challenges but is on the other hand
notcarbon free. Therefore, methanol is not a viable option to obtain zero carbon
emissions from ships.

Keywords: hydrogen, methanol, ammonia, port infrastructure, fuel storage, fuel
transport, fuel distribution, fuel bunkering,

1



Table of Contents
1 Introduction 1

1.1 Background 2
1.2 Purpose 3
1.3 Research question 4
1.4 Scope 4
1.5 Limitations 4

2 Theory 6
2.1 Hydrogen 6

2.1.1 Emissions 7
2.1.2 Safety 7
2.1.3 Storage and distribution 8

2.2 Methanol 9
2.2.1 Emissions 9
2.2.2 Safety 10
2.2.3 Storage and distribution 10

2.3 Ammonia 11
2.3.1 Emissions 12
2.3.2 Safety 12
2.3.3 Storage and distribution 13

2.4 Alternative Fuel Infrastructure Directive 14
2.5 Ports 15

3 Method 17
3.1 Literature review 17
3.2 Search phrases 17
3.3 Analysis of documents 19

4 Results and analysis 20
4.1 Challenges with hydrogen, methanol, and ammonia 21

4.1.1 Hydrogen 21
4.1.1.1 Storage 27
4.1.1.2 Transportation and distribution 29
4.1.1.3 Bunkering 32

4.1.2 Methanol 34
4.1.2.1 Storage 36
4.1.2.2 Transportation and distribution 36
4.1.2.3 Bunkering 37

4.1.3 Ammonia 38
4.1.3.1 Storage 41
4.1.3.2 Transportation and distribution 42
4.1.3.3 Bunkering 44

4.2 Transport cost comparison 46
5 Discussion 48

5.1 Common Challenges 48

2



5.2 Energy carrier-specific challenges 49
5.2.1 Hydrogen 49
5.2.2 Ammonia 51
5.2.3 Methanol 51

5.4 Methodological discussion 51
6 Conclusions 53
7 Recommendation for future work 54

3



4



Preface

The master thesis challenged us in many ways. Since our prior experience was not
connected to this area of the maritime sector we had the chance to immerse ourselves
in the highly relevant subject of alternative fuels. Which broadened our views and
showed the challenges for the future to adapt alternative fuels from a
techno-economic view.

Special thanks to our supervisor Fayas Malik Kanchiralla for his invaluable guidance
and support during the work on the thesis and to our examiner Selma Brynolf for
providing excellent and constructive feedback.

Göteborg May 2023

Sten Olsson & Richard Yang

5



Abbreviations

AF Alternative Fuel

AFI The Alternative Fuel Infrastructure

BOG Boil-Off Gas

Capex Capital Expenses

CH3OH Methanol

CO2 Carbon Dioxide

EGR Exhaust Gas Recirculation

EU European Union

GHG Greenhouse Gas

H2 Hydrogen

H2O Water

HFO Heavy Fuel Oil

HRS Hydrogen Refueling Station

ICE Internal Combustion Engine

IGC International Code For The Construction And Equipment Of Ships
Carrying Liquefied Gasses In Bulk

IGF International Code Of Safety For Ships Using Gases Or Other Low-Flash
Point Fuels

IMO International Maritime Organization

LHV Lower Heating Value

LNG Liquified Natural Gas

LOHC Liquid Organic Hydrogen Carriers

MGO Marine Gas Oil

N2 Nitrogen Gas

NH3 Ammonia

6



NH4+ Ammonium Ions

NOx Nitrogen Oxides

Opex Operational Expenses

PM Particular Matter

RoRo Roll On Roll Off

SCC Stress Corrosion Cracking

SCR Selective Catalytic Reduction

SECA Sulphur Emission Control Areas

SMR Steam Methane Reforming

SOx Sulfur Oxides

TWC Three-Way Catalysts

7





1 Introduction

The earth is covered by approximately 70% ocean by surface area (Andersson et al.,
2016). In addition, the maritime sector serves as a central pillar of international trade
with modern shipping accounting for over 80% of global trade traveling through ports
(Damman & Steen, 2021; Millefiori et al., 2020). It will be necessary to substitute
fossil fuels with sustainable alternative fuels (AFs) on a wide scale to meet the
International Maritime Organization (IMO) decarbonization and desulfurization goals
and standards (IRENA, 2022; Serra & Fancello, 2020). There are several potential
alternatives to traditional marine fuels making the choice difficult for the shipping
industry (Serra & Fancello, 2020). Among the frequently mentioned alternative fuels
that seem to have the greatest potential are hydrogen, ammonia, and methanol (ben
Brahim et al., 2019; IRENA, 2022; Serra & Fancello, 2020).

Presently, most marine vessels run on fossil fuels such as heavy fuel oil (HFO) and
marine gas oil (MGO), which negatively impact the climate, natural environment, and
human health. Approximately 2,2% of total global carbon dioxide (CO2) emissions
can be traced to the maritime sector (Sadiq et al., 2021). Additionally, 15% of
nitrogen oxides (NOx) and 6% of sulfur oxides (SOx) are emitted by the maritime
sector. The most polluted cities in the world are all located near the coast, which is
made worse by the fact that approximately 70% of ship emissions take place within
400 km of coastal regions (Alzahrani et al., 2021). In 2018, the IMO adopted a
strategy to reduce greenhouse gas (GHG) emissions from ships (IMO, 2021). The
main goals of the strategy are the following: to reduce GHG emissions by at least 40%
by 2030 and by at least 70% in 2050, compared to 2008 levels. Primary measures to
reach this goal are developing and using more efficient ships and implementing the
usage of alternative fuels. Another key milestone was the Paris Agreement which was
signed by 184 countries to show commitment to taking action to decrease the average
global temperature by decreasing emissions and relying more on renewable energy
(Alzahrani et al., 2021). The global CO2 would need to decrease by 30% by 2030 to
restrict the temperature increase to 2℃ as per the Paris Agreement’s goals
(AbouSeada & Hatem, 2022).

In the context of selecting an alternative fuel within the maritime sector, liquified
natural gas (LNG) has been introduced to the shipping industry as a sustainable
alternative to MGO and HFO. The introduction of strict Sulphur Emission Control
Areas (SECA) favored the increased use of LNG (Aronietis et al., 2016). When LNG
is used in an internal combustion engine (ICE) onboard a vessel the CO2 emissions are
less than HFO and MGO emissions. However, research shows that LNGs' reduction in
CO2 emissions is not enough to replace conventional fuels (ben Brahim et al., 2019;
Pavlenko et al., 2020). In addition, methane slips while using LNG resulting in
increased GHG emissions as methane is a stronger GHG than CO2. This has promoted
the interest in using other alternative energy carriers such as hydrogen (H2), methanol
(CH3OH), and ammonia (NH3) within the shipping industry. Reducing GHG
emissions to meet the IMO goals is the primary reason for researching these energy
carriers as they are considered sustainable alternatives to be adopted shortly to reduce
the climate impact from a life cycle perspective (Song et al., 2022).

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 1



1.1 Background
One alternative to traditional energy carriers is hydrogen within shipping. According
to IRENA (2022), hydrogen is a milestone needed to achieve decarbonization.
Hydrogen is one of the most abundant elements in the universe sitting at the top of the
periodic table. It is usually bound up with other elements for example water (H2O)
and needs to be separated through electrolysis (Ocko & Hamburg, 2022). Currently,
approximately 95% of hydrogen is produced from nonrenewable resources (Amirante
et al., 2017). The majority of the world’s supply of hydrogen is produced through a
method called steam methane reforming (SMR) (Amirante et al., 2017; Capurso et al.,
2022; Mazloomi & Gomes, 2012). As the name suggests, it revolves around reacting
natural gas consisting of methane with high-pressure steam to produce hydrogen gas.
However, for one ton of hydrogen produced with natural gas, there are 2,5 tons of
CO2 released, while using coal releases 5 tons of CO2 (Amirante et al., 2017).
Producing hydrogen with fossil fuels with carbon capture and storage is referred to as
blue hydrogen (Amirante et al., 2017). By increasing the efficiency of industrial SMR
plants by managing the excessive heat from the plants combined with currently
existing carbon capture technology would decrease CO2 emissions during hydrogen
production. As per Katebah et al. (2022), the CO2 emissions from an industrial SMR
combustion plant are escaped as flue gas and can be captured at three different
locations of the plant with the maximum estimated carbon captured being around 70%
of the CO2 emissions. The hydrogen production cost is estimated to only increase by
7% excluding the CO2 transport, utilization, and storage costs (Katebah et al., 2022).

Other than hydrogen gas, CO2 is also created as a byproduct in the process. Currently,
the SMR method relies on fossil natural gas to produce hydrogen (Capurso et al.,
2022; El-Shafie et al., 2019). Hydrogen produced from fossil fuels is also known as
gray hydrogen. Moreover, it would not meet future demands. The increase needed is
approximately five times the present production, i.e., 614 megatonnes per year, which
is only 12% of the energy demand in 2050 (IRENA, 2022). The usage of fossil fuels
such as natural gas in production results in the same emission as the combined CO2
emissions of the United Kingdom and Indonesia combined, i.e., 830 metric tons of
carbon dioxide per year. Substituting fossil fuels with only hydrogen is highly
unlikely, as hydrogen has a low density which results in several challenges associated
with transportation and storage. Therefore, other alternative fuels such as ammonia
and methanol are likely to assist with decarbonizing the maritime industry (IRENA,
2022). Hydrogen is also needed to produce energy carriers such as ammonia and
methanol. The current hydrogen production methods need further development to
increase the feasibility of hydrogen, ammonia, and methanol as sustainable
alternatives (IRENA, 2022).

A more sustainable method for hydrogen production is where water electrolysis is
powered by renewable energy sources such as biomass, wind, solar, or a mix of these
(Amirante et al., 2017; IEA, 2019). Using water creates oxygen and hydrogen and
therefore no CO2 emissions. Hydrogen produced from this method is known as green
hydrogen. Currently, green hydrogen is more expensive than gray hydrogen. Gray
hydrogen and methanol are mainly produced by natural gas, but also by coal. The
production of these alternative fuels is more expensive than using natural gas, as
water electrolysis requires energy and expensive materials (Amirante et al., 2017;
DNV GL, 2018). Hence, with current technology, the higher production costs of gray

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 2



hydrogen compared to natural gas are existing economic barriers. The economic
barriers to green hydrogen including ammonia and methanol produced from green
hydrogen are even bigger. However, the development of green hydrogen is not likely
to happen if blue hydrogen is not explored before (Tvedten & Bauer, 2022). Due to
the cost and scalability advantages of fossil fuel. To develop the hydrogen supply
chain IRENA (2022) mentions that 4 trillion USD is needed to be invested to trade
36% of the global volume into green hydrogen. The cost of hydrogen is expected to
decline in the future due to the increased production of green hydrogen (Latapí et al.,
2023). The EU has a goal of increasing green hydrogen production by up to 1 million
tons in 2024 and up to 10 million tons by 2030.

Another alternative energy carrier is ammonia consisting of hydrogen and nitrogen
and is most commonly used for fertilization (McKinlay, 2021). Ammonia does not
contain carbon and therefore it will not result in carbon emissions when combusted
and is not flammable in the air. However, there are other disadvantages to the energy
carrier. Such as forming NOx when used in an internal combustion engine, high
toxicity for humans, and corrosiveness. Similar to blue hydrogen, ammonia produced
from natural gas with carbon capture is referred to as blue ammonia (Laursen et al.,
2022). Furthermore, ammonia can be produced sustainably by using hydrogen from
water electrolysis and nitrogen from air separation (Wang et al., 2022). The process
can also be powered by a renewable source, e.g., wind power, this is then called green
ammonia when only using renewable sources to produce the compound. Since
ammonia is commonly used as a commodity there are already established storage and
distribution infrastructures. However, presently most of the ammonia is produced
from fossil fuels (Pawar et al., 2021).

Methanol is a type of alcohol with high energy density, negligible SOx emissions, and
60% lower NOx emissions than HFO and notably lower than ammonia (McKinlay,
2021). Using methanol directly as an energy carrier would emit CO2 in a comparative
amount to LNG combustion (McKinlay, 2021). It can be used as fuel in either a
combustion dual-fuel engine or in a fuel cell. A more sustainable alternative would be
to use methanol produced from green hydrogen (green methanol) or using
bio-methanol or liquefied biogas will be required to cut total GHG emissions
(IRENA, 2022; Christodoulou & Cullinane, 2021). However, using methanol as a fuel
might be easier as it can be much more conveniently stored and distributed due to it
being a liquid at ambient temperatures (DNV GL, 2018). Overall, methanol is an
alternative fuel that resembles traditional fossil fuels. Meaning, that the existing
bunkering infrastructure can be used for methanol with minor modifications
(Evergren et al., 2017).

1.2 Purpose
Using energy carriers such as hydrogen, ammonia, and methanol has the potential to
reduce GHG emissions from shipping, however, more knowledge is required on the
supply chain of these energy carriers from fuel production to the fuel to be used for
propelling the ship. This master thesis focuses on the storage, transportation &
distribution, and bunkering of three alternative energy carriers: hydrogen, methanol,
and ammonia. The purpose is to analyze and assess the technical and economic
challenges associated with the usage of these energy carriers connected to port
infrastructure using a literature study. The study will include a comprehensive report

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 3



that should provide challenges of implementing infrastructure for the analyzed energy
carriers.

The main objective is to identify how the supply chains and facilities of these
alternative fuels can be established for distribution, storage, and bunkering, with a
focus on port infrastructure and the bunkering of vessels. Moreover, a cost analysis of
the infrastructure for the above-mentioned alternative energy carriers will also be
conducted. This should provide a better understanding of the economic feasibility of
adopting newer energy sources and their impacts on the port and the maritime
industry.

1.3 Research question
The following research question is being answered in the report:

What are the techno-economic challenges associated with the storage, transportation,
distribution, and bunkering phases of hydrogen, methanol, and ammonia for use in
shipping within their respective supply chains?

1.4 Scope
Figure 1 shows a simplified supply chain of energy carriers from production to actual
usage in ships. The scope of the thesis is to review the current state and future of
hydrogen, methanol, and ammonia in port infrastructure connected to transportation
and distribution, storage, and bunkering.

Figure 1.
Scope of the thesis

1.5 Limitations
Due to the broad subject, there is a need to limit the subject. Limitations were chosen
to clarify what will be included and excluded from the research. The scope and
boundaries of the study are made more feasible and the objectives more achievable.
The following limitations were chosen:

1. Technical limitations: The type of energy carriers included in this study are
hydrogen, methanol, and ammonia.

2. System boundary: This study will also focus on the techno-economic impact
of the implementation of alternative fuels in port and to its stakeholders,
within the specified areas.

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 4



3. Geographical scope: the study will not focus on a specific geographic region,
but on a broader global scale as the research on this subject is not bound by
geographic location.

4. Type of ships: The study will not focus on a specific vessel type as the
research revolves around the port facilities and their compatibility with the
above-mentioned alternative fuels. Container-, RoRo-, ferries, bulk- and
tanker- vessels are, however, the most commonly researched and cited ships
relevant to this study.

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 5



2 Theory
2.1 Hydrogen

Hydrogen is the simplest and most abundant element in the universe. On Earth, it is
primarily found bound together with other elements such as carbon in hydrocarbons
and oxygen in water (Mazloomi & Gomes, 2012). Table 1 summarizes a few of the
properties of hydrogen.

Table 1.
Properties of hydrogen

Properties Value

Name, Molecular formula Hydrogen, H2

Phase Gas (Room temperature)

Melting point −259.14℃

Boiling point −252.9℃

Flash point −252.9℃ (Gas form)

Auto-ignition 585℃

Chemical safety Explosion and fire hazards

Compressed hydrogen density 39 kg/m3

Liquid hydrogen density 70,8 kg/m3

Compressed hydrogen volumetric
energy density

4,5 MJ/l

Liquid hydrogen
volumetric energy density

8,49 MJ/l

Compressed hydrogen gravimetric
energy density

120 MJ/kg

Liquid hydrogen gravimetric
energy density

120 MJ/kg

Note. Density, volumetric energy density, and gravimetric energy density are for both
compressed and liquid hydrogen as they differ (Aziz & Nandiyanto, 2020).

The concept of a CO2 free hydrogen chain as mentioned by Kawasaki (2022) contains
three steps: 1. Produce, 2. Transport/storage and 3. Use. The first step is to produce
hydrogen from renewable energy or use fossil fuels in combination with carbon
capture and storage. The second step is transportation and storage. Transportation of
hydrogen may be performed by liquified hydrogen carriers or liquefied hydrogen
trailers or pipelines (Kawasaki, 2022; IEA, 2019). Moreover, the storage occurs in
CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 6



liquid or gaseous hydrogen storage tanks. Geographical locations can also be used for
long-term storage. The final point to consider is that hydrogen could be used through
either ICEs or as fuel cells. However, usage in ICEs leads to a 20% to 25%
effectiveness considering the supply chain (Ravi & Aziz, 2022). That is lower than the
effectiveness of oil or diesel which corresponds to 30% to 35% in combination with
an ICE.

2.1.1 Emissions
Hydrogen can be used as fuel or energy carrier for ships, cars, trains, and planes. In
addition, the only byproduct of hydrogen is water, meaning it has no carbon content
and therefore zero CO2 emissions when used as a fuel. These properties have made
hydrogen one of the promising renewable energy carriers as it holds the potential to
be fully emission-free when combusted (Hoang et al., 2022; Mazloomi & Gomes,
2012). Furthermore, hydrogen has the highest amount of energy when comparing
fossil-free fuels that are combusted with air (Sifakis et al., 2022). When using
hydrogen in an ICE there are NOx emissions (Ravi & Aziz, 2022). Hydrogen can be
used in combination with fuel cells (Genovese & Fragiacomo, 2023). The fuel cells
can either be used for shore operation in port or on board a vessel (Vicenzutti &
Sulligoi, 2021). However, current hydrogen technology, including the whole supply
chain, needs to be developed in order to accomplish the goal of zero carbon emissions
(IRENA, 2022; Genovese & Fragiacomo, 2023).

2.1.2 Safety
There are several safety concerns regarding hydrogen that need to be addressed before
it can be widely accepted as an energy carrier (Mazloomi & Gomes, 2012; Panić et
al., 2022; Osman et al., 2021). The main concern is that hydrogen is easily flammable,
even a mere concentration of 4% hydrogen gas in the air can be ignited, creating an
explosive environment. This can be avoided by properly maintaining the
concentration of hydrogen in the air or by converting it to liquid form (Mazloomi &
Gomes, 2012). Moreover, the flames are nearly invisible making them difficult to
detect. Smoke asphyxiation by fires is considered to be one of the common hazards
and has the largest damage share of fire (Panić et al., 2022; Osman et al., 2021).
However, unlike conventional fuels with more complex molecule structures, the
smoke of hydrogen is completely harmless when inhaled. Furthermore, other several
safety concerns are odorless and tasteless (Panić et al., 2022; Osman et al., 2021).

Another related aspect to hydrogen being easily flammable is its low
electro-conductivity, which is a safety concern during handling and storing hydrogen,
as electrostatic charges can be generated resulting in sparks that ignite the hydrogen
(Mazloomi & Gomes, 2012). On the other hand, a safety characteristic of hydrogen is
that its auto-ignition temperature is high at 585℃, as seen in Table 1, i.e., hydrogen is
easily ignited from external ignition sources but has a high auto-ignition temperature.

For the IGF code (International Code of Safety for Ships Using Gases or Other
Low-flash Point Fuels) hydrogen is not directly regulated (DNV, 2021). Low flash
point fuels such as hydrogen (-252.9℃) are allowed if the systems can prove to be as
safe as new oil vessels. If hydrogen is used with the fuel cell technology it is not
decided if the areas where fuel cells are located will be classified as a hazardous zone.
A hazardous zone is the result of a research project. However, this has not been
CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 7



conducted for hydrogen fuel ships. Furthermore, liquid hydrogen could lead to cold
burns. Wang et al. (2023) mention that the instability and explosive nature of
hydrogen requires high technological, transport, and storage investments. However,
this can lead the port to develop and use these methods to increase its ability to
compete with other ports.

2.1.3 Storage and distribution
Regular hydrogen production, handling, and distribution as a business have been
around for decades, mainly used in space applications. There are several ways to store
hydrogen, e.g., in tanks. In comparison to storing hydrogen as compressed gas, storing
liquid hydrogen in cryogenic tanks has a higher energy content. As liquid hydrogen
has a high density at low-pressure levels, which allows for more efficient distribution
options due to using less volume than compressed hydrogen (Capurso et al., 2022;
Mazloomi & Gomes, 2012). However, the temperature required to liquify hydrogen is
below −252,9℃ and adds 30% to power demand. Moreover, using gas liquefiers and
maintaining a low temperature further complicates the production system. As a result,
the cost of liquid hydrogen is estimated by Mazloomi and Gomes (2012) to be 4-5
times higher compared to compressed hydrogen gas. In addition, hydrogen contains
the lowest volumetric density when comparing hydrogen, methanol, and ammonia
(Aziz & Nandiyanto, 2020). Furthermore, when storing and transporting liquefied
gasses, such as liquified hydrogen at low temperatures, a portion of the liquified gas
will constantly warm up and evaporate back into its gaseous state. This effect is called
boil-off gas (BOG) (Al-Breiki & Bicer, 2020). As a result, a portion of the loaded
liquified gas will inevitably be lost. This can be avoided to a degree by using
high-quality insulation materials.

A preferred choice for several vehicle manufacturers is to store hydrogen gas in
high-pressure cylinders that can be mounted on vessels for transport (Mazloomi &
Gomes, 2012). The advantages of this method are the efficiency, low cost, and being
environmentally friendly compared to the other methods. The primary disadvantage of
this approach is the storage limitations, due to the low storage density. Which
arguably can increase GHG emissions, since less hydrogen is being distributed and
requiring additional trips. Hence, many experts predict that high-pressure cylinder
storage for hydrogen will not be a popular method in the future (Mazloomi & Gomes,
2012).

Hydrogen can also be stored in metal hydrides through a process called absorption.
The hydrogen molecules are absorbed into metal lattices, which form a chemical bond
between the hydrogen and certain types of metals. Reduced temperatures absorb the
hydrogen gas into the metal hydrides while applying heat to separate the hydrogen gas
from the metal (Mazloomi & Gomes, 2012). The hydrogen can essentially be
absorbed or released at normal pressure levels. This method has a high storage
capacity compared to other storage methods such as compressed gas or liquid
hydrogen (Rangel et al., 2022). Storing hydrogen through metal hydrides is also safer
and more reliable, as the risk of leaks and explosions due to the absence of
high-pressure hydrogen is reduced. However, there are also disadvantages to this
storage method. Metallic hydrides have low energy densities per unit mass. The metal
adds extra weight that would increase the weight requirements for distribution and
transportation with this method (Rangel et al., 2022). In other words, from a technical

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 8



perspective, storing hydrogen in metal hydrides is a secure and reliable option. But
from an economic perspective, the technology is still not yet mature enough.

2.2 Methanol
The simplest alcohol, methanol (CH3OH) is one alternative fuel used in the shipping
industry (DNV GL, 2018). Methanol is a chemical that traditionally is a commodity
and is produced on a large scale. Methanol had an annual production capacity of
around 110 million tons per year in 2018 (Kajaste-Rudnitskaja et al., 2018). Methanol
can be created from natural gas, coal, black liquor (from pulp and paper mills),
forests, or agricultural waste (DNV GL, 2018). Another method is capturing CO2
from power plants. Methanol is created using natural gas by mixing steam reforming
and partial oxidation. This leads to an energy efficiency of approximately 70%,
measured in energy in the methanol in comparison to the energy in natural gas. On the
other hand, using coal is cheaper, but the GHG emissions are double compared to
natural gas. Table 2 summarizes some of the properties of methanol.

Table 2.
Properties of methanol

Properties Value

Name, Molecular formula Methanol, CH3OH

Phase Liquid (Room temperature)

Melting point −97,6℃

Boiling point 64,7℃

Flash point 11 to 12℃

Auto-ignition 358℃

Chemical safety Acute toxic, flammable, health hazardous

Density 792 kg/m3

Volumetric energy density 15,8 MJ/L

Gravimetric energy density 20,1 MJ/kg

2.2.1 Emissions
The methanol molecule includes a carbon molecule which makes it inevitable that
combustion of methanol would result in carbon emissions (DNV GL, 2018). Although
the carbon emissions are significantly less than other traditional fuels it is not a
zero-emission fuel. If the energy carrier was produced using biomass, the life cycle
emissions would be lower compared to natural gas. There are two different
alternatives to traditional engines, two-stroke diesel engines or four-stroke Otto
engines. Furthermore, the reduction of CO2 results in approximately 10% lower than
oil-based fuels. SOx emissions are almost zero and NOx emissions depend on the
engine or technique used. A two-stroke engine results in about 30% lower NOx

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 9



emissions, while a two-stroke Otto engine results in a decrease of approximately 60%
lower NOx compared to oil. However, to comply with Tier III limits there is a need to
combine the usage of methanol with either an EGR (exhaust gas recirculation) or SCR
(selective catalytic reduction) to further reduce the emissions (DNV GL, 2018).

2.2.2 Safety
Methanol is already a common commodity with large-scale production and a
well-established global market. With an annual production capacity of around 110
million tons per year (Kajaste-Rudnitskaja et al., 2018). The safety characteristics and
handling of methanol have also been well researched as a result of the extensive
experience in transporting and handling methanol as a commodity. There is already
existing governance and regulating bodies for the handling of methanol. The main
guideline for shipping is the IGF code. The Methanol Safe Handling manual first
published in 2013 by the Methanol Institute is another measure to provide an
overview of critical methanol safety and handling information of the liquid (Kamaljit,
2016).

Methanol is an easily flammable, clear, and colorless fluid. By IGF standards, it is a
fuel that requires special safety measures when handling due to its rather low flash
point, i.e., capable of igniting at lower temperatures (Kamaljit, 2016). This can be a
safety concern when storing larger quantities of methanol (Svanberg et al., 2018; Paris
MoU, 2022). It also has a low boiling point of 64,7°C, allowing it to evaporate
quickly when exposed to heat (Kamaljit, 2016). If set ablaze, the flames are difficult
to extinguish, and hydrogen fires are difficult to spot in daylight. Methanol flames
emit poisonous chemicals, such as formaldehyde. Other safety characteristics of
methanol include its being acutely toxic. It can cause serious health issues when in
contact with the skin or when inhaled or ingested. Proper equipment and safety
measures are therefore important during handling, storage, and transportation to
prevent accidents in connection to methanol leaks (Kamaljit, 2016). A positive safety
aspect is that methanol is quick to dissolve and biodegrade in water. This means any
potential leaks would mean less severe environmental effects (Evergren et al., 2017).

2.2.3 Storage and distribution
In recent years, only a few methanol-based types of ships have emerged. The shipping
company, Stena Line modernized one of their ships and introduced the first
dual-engine methanol-powered ships in the world: Stena Germanica (Christodoulou &
Cullinane, 2021; Kamaljit, 2016). Functioning as a roll-on, roll-off-passenger ship
(Ro-pax) and operating between Gothenburg and Kiel. The Port of Gothenburg has a
dedicated area for bunkering of methanol that is utilized by Stena Germanica.
Methanol is relatively easy to transport, as it is liquid under ambient conditions.
Methanol fuel can conveniently be distributed by trucks or bunker vessels to
methanol-fueled vessels (DNV GL, 2018). Additionally, methanol shares similar
characteristics to oil-based fuels. Meaning, that the existing bunkering infrastructure
will require minor modifications (ben Brahim et al., 2019; Evergren et al., 2017).

When used as fuels in an engine, both ammonia and methanol are combusted
similarly to the diesel process. However, usage of solely ammonia or methanol is not
possible in an ICE, as they have poor ignition capabilities. A dual-fuel engine in
combination with an engine igniting pilot fuel is needed to start the combustion
CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 10



(Hansson et al., 2020). Diesel in small amounts, approximately 5% of the total energy
is needed for propelling the ship. In order to reach a 100% decarbonization rate on the
fuel combustion part biomass fuel could replace diesel fuel.

2.3 Ammonia
The inorganic compound Ammonia (NH3) consists of hydrogen and nitrogen. Similar
to methanol, ammonia is traditionally a commodity and is produced on a large scale.
Ammonia had a global annual production of around 183 million tons in 2020 and is
mostly used within the agriculture sector as a fertilizer (McKinlay et al., 2021; Pawar
et al., 2021). 85% of the total ammonia output is being utilized as fertilizer. Aside
from its current use as a fertilizer, ammonia is viewed as a potential alternative fuel
due to its ability to be stored and transferred effectively and affordably, in comparison
with pure hydrogen (Pawar et al., 2021). In shipping, ammonia can be used as fuel in
either a combustion dual-fuel engine or in fuel cells (Prause et al., 2022). Ammonia
has the potential to replace conventional fuels due to it being carbon-free and
capability of being handled in existing infrastructure with refurbishment. The energy
density is higher than hydrogen’s but lower than methanol (Hoang et al., 2022; Reiter
& Kong, 2011; Song et al., 2022). A disadvantage of ammonia compared to other
fuels is its high auto-ignition temperature as seen in Table 3. Out of all the listed fuels,
ammonia has the highest auto-ignition temperature at 651 °C. Unless used in fuel
cells, a dual-fuel engine with a pilot fuel is necessary (Hoang et al., 2022; Reiter &
Kong, 2011).

Table 3.
Properties of Ammonia

Properties Value

Name, Molecular formula Ammonia, NH3

Phase Gas (Room temperature)

Melting point −77,73℃

Boiling point −33,34℃

Flash point -

Auto-ignition 651℃

Chemical safety corrosive and toxic

Liquid ammonia density 600 kg/m3

Liquid ammonia volumetric
energy density

12,7 MJ/L

Liquid ammonia gravimetric
energy density

18,6 MJ/kg

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 11



2.3.1 Emissions
The majority of ammonia is manufactured from fossil fuels such as natural gas, which
generates a significant quantity of carbon dioxide. Therefore, it has been preferable to
use natural gas directly as a fuel in a vehicle rather than producing ammonia from the
natural gas. Similar to producing hydrogen, a renewable production method for
ammonia is electrolysis. By remaking a dual-fuel diesel engine’s fuel intake system
the engine could successfully run on 95% ammonia and the remaining 5% with diesel
as a pilot fuel (Reiter & Kong, 2011). The emissions from combustion of ammonia
were noted to be carbon-free but emissions of other air pollutants such as NOx and
particulate matter were present (Reiter & Kong, 2011). Various studies show that NOx
emissions are the major pollutant of ammonia. NOx emissions can however be
mitigated by using three-way catalysts (TWC), EGR or SCR technology (Hansson et
al., 2020). Furthermore, the possibility to use ammonia with fuel cells exists, as it
only emits water and nitrogen gas (N2) emissions (Nowicki et al., 2022).

2.3.2 Safety
Ammonia is a colorless gas with a strong odor that can be detected at very low
concentrations, indicating a leak or spill. There are major safety concerns with
ammonia due to its toxicity in human and maritime environments (Prause et al.,
2022). Ammonia is corrosive and can severely burn soft tissues, eyes, and respiratory
systems. The corrosiveness of the gas also means that the storage material used needs
to be considered to prevent degradation, leaks, and spills (McKinlay et al., 2021).
Ammonia levels of 2 700 PPM are lethal for humans if exposed for 10 minutes (de
Vries, 2019). Ammonia when released into the water is biodegradable and not harmful
to humans or plants. The formation of ammonium ions (NH4+) is, however, in the
long term harmful for life in the water. There are existing regulations for carrying and
handling ammonia as a commodity, such as the IGC Code 2014 abbrived from
International Code for the Construction and Equipment of Ships Carrying Liquefied
Gasses in Bulk (Ash & Scarbrough, 2019). The IGC code (2014) Chapter 17 provides
guidelines for the safe sea transportation of liquefied gasses in bulk. The IGC code
does not consider ammonia’s flammability and explosivity a significant hazard (IGC
code, 2014). The major hazard traits of ammonia are deemed to be its toxicity and
corrosiveness. To prevent spills or leakages of the ammonia, the IGC code has
minimum requirements for vessels carrying anhydrous ammonia as can be seen in
Table 4. However, there is a clear distinction between carrying ammonia as a
commodity and using it as the primary fuel for a vessel. Clearer safety regulations that
consider the risk of leakage, spills, and other safety concerns during bunkering and
operation of the vessel are required to be clarified in the future in case of large-scale
implementation (Hansson et al., 2020).

Table 4.
Minimum requirements for anhydrous ammonia (IGC code, 2014).

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 12



Minimum
requirements

IGC
Code
(2014)
Chapter

Description

Personal protection 14.4 Individuals on board must have access to
appropriate eye protection and respiratory
gear in the event of an emergency
evacuation.

Materials of
construction

17.2.1 Cargo tanks must be designed and built with
proper materials of construction and have a
corrosion-resistant covering.

Special requirements 17.12.2 Cargo tanks minimum yield strength not
exceeding 355 N/mm2 & actual yield
strength not exceeding 440 N/mm2.

Special requirements
for stress corrosion
cracking (SCC)

17.12.8 Advised to keep dissolved oxygen levels
below 2.5 ppm

2.3.3 Storage and distribution
Ammonia is capable of inflicting severe corrosion, mostly in the form of stress
corrosion cracking (SCC) (IGC code, 2014). SCC is especially dangerous since cracks
can lead to leakage or spills (Elishav et al., 2021; Trivyza et al., 2021). Considering
the toxic nature of ammonia it could have disastrous consequences. Tensile stress
combined with a corrosive environment (exposure to high humidity) are usually the
culprits for SCC and can result in the protective metal oxide layer of the tank
breaking. SCC typically consists of three stages:

1. initiation
2. propagation
3. failure.

In the initiation stage, it starts as a minor defect or cracks at the surface of the metal.
The crack quickly spreads throughout the surface in the second stage propagation as a
result of further tensile stress and corrosion. Finally in the third step, failure, the
cracks are of critical sizes and the material is failing (Rao et al., 2016). SCC can occur
in all ammonia storage and distribution systems, such as tanks, pipes, and valves. For
instance, SCC might occur in the welds of ammonia pipes due to the significant
tension placed on the welds during the welding process. SCC can also happen in the
metal's heat-affected zone, where the welding process has changed the metal's
mechanical characteristics. Copper and copper alloys have been demonstrated to be
especially vulnerable to SCC (Rao et al., 2016). Other metals and metal alloys
commonly used such as aluminum and brass risk developing SCC (Ash &
Scarbrough, 2019; Elishav et al., 2021). It not only affects metal and its alloys but also
other materials such as plastics and ceramics (Elishav et al., 2021).

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 13



There are two primary storage options for ammonia, low-temperature or pressurized
storage (Pawar et al., 2021; Reiter & Kong, 2011). Ammonia is a liquid at room
temperature at around 9 bar. However, ammonia is frequently pressurized up to 17 bar
to keep the chemical in the liquid phase if the temperature were to rise above room
temperature. The advantage of pressurized storage is that no energy is required and
frequently used to store lower quantities as approximately 1 ton of steel is required to
store 2,8 tons of ammonia (Reiter & Kong, 2011). Low-temperature storage, on the
other hand, is typically used when storing larger quantities of ammonia. Keeping the
ammonia in liquid form and avoiding boiling off is energy intensive but is
significantly lighter to store (Pawar et al., 2021; Reiter & Kong, 2011). Furthermore, 1
ton of steel can store approximately 41–45 tons of ammonia. Contrary to liquefied
hydrogen, there is no need for cryogenic storage when employing ammonia, meaning
less energy is required to store and transport ammonia (Hansson et al., 2020).

Ammonia is commonly transported through pipelines (IEA, 2019). The best way to
distribute ammonia to the end users depends on the distance, volume, and usage
purpose. Moreover, trucks are another option. Either in pressurized or in refrigerated
tanks. Furthermore, LNG is used frequently as a transition fuel; there is a possibility
to convert current LNG storage tanks to ammonia storage tanks without any larger
adjustments (Prause et al., 2022). Similar to hydrogen, ammonia can also be stored in
solid form by binding the ammonia to metal amine complexes (Aziz & Nandiyanto,
2020). This lowers the toxicity to comparable levels to gasoline and methanol and
removes the safety issues of transporting liquid ammonia. This technology is however
not economically justifiable, similar to how it is for storing hydrogen in metal
hydrides.

2.4 Alternative Fuel Infrastructure Directive
The Alternative Fuel Infrastructure (AFI) directive was established by the European
Union (EU) to accelerate the installation of infrastructure for alternative fuels. The
goal is to aid the goals set by the Paris Agreement in 2015 to combat the global
climate crisis (Ertug, 2018). The Paris Agreement stipulated goals of bringing the
global temperature below 2℃ and the ideal being 1.5℃. According to the AFI
regulation, the transport sector must escalate the reduction of carbon emissions to
reach net zero emissions by 2050.

According to the European Parliament's Committee on Transport and Tourism
rapporteur, Ertug (2018) switching to AF may help achieve the Paris Agreement’s
goals but acknowledges the fact that conventional fuels will be needed for some time.
The development of AF has to reach the point where it can fulfill the demand.
Shipping accounts for over 3% of GHG emissions and is responsible for air pollution
close to coastal areas and ports. The steady adoption of AF would significantly
improve the environment (Ertug, 2018). To enable a more seamless transition, the AFI
regulations optimize the logistics for sustainable AF such as hydrogen, ammonia,
hydrogen, and batteries. Switching to AF is however yet a challenge as several factors
have to be taken into consideration. The researchers, Benamara et al. (2019) have
identified several restrictions, measures, and solutions to adopting AF in ports, as can
be seen in Table 5.

Table 5.
Alternative fuel adoption strategies for ports (Benamara et al, 2019)
CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 14



Restrictions Solutions for the adoption of
alternative fuels in ports

Capital requirements - to identify the
key requirements for infrastructure

Government funding and budget
allocation

Persistence of using fossil fuels to
generate and produce alternative fuels

Utilization of renewable energy sources
for alternative fuel production

Environmental issues with AF 1. Conducting life cycle analysis of the
alternative fuels’ emissions
2. Evaluating the cost-to-benefit ratio

Security issues with AF 1. Training
2. Certification and standards
3. Risk analysis

Promote harmonized standards Encourages the creation of consistent
standards for setting up AF
infrastructure. Harmonized standards
can help ensure that the infrastructure is
interoperable and used by ships across
different member states.

2.5 Ports
The definition of a port is a geographical area where vessels discharge and load cargo
(Stopford, 2008). The structure of ports can either be public bodies, government
organizations, or private companies. The port authority is a service provider within
the port environment, e.g., providing vessels berth space. Furthermore, terminals are
located in the geographical port area and there can be several terminals in one port.
There are different terminal types devoted to various cargo handling categories, such
as container-, bulk- and RoRo (roll on roll off)- terminals. Similar to the port
governance the terminals can be operated by different actors, such as shipping
companies (Damman & Steen, 2021; Stopford, 2008).

The main function of the port is to provide berthing for vessels. There are also other
secondary functions, such as investing in facilities and infrastructure (Nisiforou et al.,
2022; Stopford, 2009). As well as dredging for vessels with increased draught, and
providing different types of cargo handling and storage for export and import cargo.
Moreover, integrate roads, inland waterways, and railways to improve connections for
the transport of cargo using various modes of transport (Stopford, 2009). Ports are
also major stakeholders in the shipping industry. There needs to be coordination
between the stakeholders. For instance, if there is no agreement between the shipping
industry and ports on what type and quantity of AF will be required. It will prevent
investments in new AF technology for both ships and ports (Nisiforou et al., 2022). 

There is also the concept of smart and green ports (Nguyen et al., 2022). These port
ideas have the same goal, to achieve technical innovation by developing sustainable
infrastructure and operations. The purpose of green ports is to use alternative energy
sources, and alternative fuels, develop waste management and ecology, and use the
CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 15



Internet of Things, to consume less energy, less waste, and fewer pollutants. For
example, use alternative fuels to power port vehicles and equipment or provide
alternative fuels for bunkering of vessels. However, there is still a lack of research on
some renewable fuels to be integrated into ports, e.g., hydrogen (Sifakis et al., 2022).

Globally ports struggle with problems such as air quality issues, particular matter
(PM), dust, and pollution of NOx and SOx (Gibbs et al., 2014). However, ports also
have an impact on the climate with emissions of GHG that contribute to global
warming. According to Gibbs et al. (2014) data from 2007 and 2008 shows that
emission from vessels at berth is ten times greater than emissions from the ports’
operation (1,8mt CO2 versus 174kt CO2). 

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 16



3 Method
3.1 Literature review
The main data collection method for the report was a literature review. Data were
collected through comprehensive searches of academic databases such as Scopus to
identify relevant studies. The search keywords consisted of a combination of
keywords relevant to the subject of this literature review. Before searching and
reviewing studies for the literature review, delimitations were identified to help
narrow down the boundaries of the research process. An inclusion criteria for the
studies was concluded to determine the relevancy of the studies. The inclusion
criteria for the studies are the following:

1. Published in a peer-reviewed journal or scholarly database such as Scopus.
2. Written in English or Swedish.
3. Studies relevant to the literature review determined from keywords, title,

abstract, and potential conclusions.

The snowballing technique was also used, where initial findings lead to the
identification of new and relevant sources, which opened up additional sources. In this
report, the snowballing technique was relevant to identify additional sources by
looking at the reference section of documents already read and documents provided
by the supervisor. Broadening the pool of relevant studies and literature on top of the
initial findings. The goal of using the snowball technique was to build a profound
understanding of the qualitative research topics that this study mainly focused on.
While reading articles and reports the reference section contains publications that
could be used throughout this thesis.

3.2 Search phrases
Several topics within the scope of this literature review were investigated regarding
hydrogen, methanol, and ammonia. To collect data keywords and search phrases were
used. Different search phrases were used depending on the information needed. In this
study the primary search engine for scientific material was Scopus. A single search
term was created in Scopus to gather data. Investigations of storage and distribution
processes, refueling processes, risk assessments, safety-related analysis, and
technical-economic analysis. The keywords and search phrases are filtered by article
title, abstract, and keywords.

Search terms used in Scopus:
(Hydrogen OR methanol OR ammonia OR electrofuel OR efuel OR
electro-fuel OR power-to-fuel ) AND infrastructure AND port AND fuel AND
( maritime OR shipping OR marine OR ocean AND transport ) AND
(LIMIT-TO (DOCTYPE, "ar" ) OR LIMIT-TO (DOCTYPE , "re"))
resulted in 332 documents (May, 2023) ranging from 1978-2023

The 332 articles in the list were compiled in a spreadsheet and selected based on title
and abstract. Moreover, the selected articles were used as sources throughout the
thesis, in either the theory, introduction, or result chapter. In the initial review, the
abstract was analyzed for inclusion in the fuel supply chain for assessed fuels. The
process of analyzing began with reading the title and thereafter the abstract. If the title
CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 17



was relevant to the selected energy carriers and if the abstract contained information
such as fuel transportation & distribution, fuel storage, fuel bunkering, or properties of
the energy carriers, it was included in the initial review. In total, 82 articles were
found relevant to the thesis scope and included in the first review phase.

In the second review, each study that had passed the first review, i.e., marked as
“relevant” was thoroughly analyzed and evaluated if fit for this literature study. All
the contents of the documents were taken into consideration. The documents had to
include information about transportation & distribution, storage, bunkering,
infrastructure, or properties related to the alternative fuels and the thesis. The
documents were then divided into category areas based on the information
requirement and energy carrier. The categories consisted of hydrogen, methanol,
ammonia, storage, transport & distribution, bunkering, and infrastructure. The
categories and amount of documents for each are shown in Figure 2. For example,
storage could be mentioned in the abstract. However, when the information was
analyzed, it was not relevant to the research question or the thesis. Occasionally,
information was connected to phases outside the scope, e.g., production of fuels or
energy production. Ultimately, the result of chosen documents from the Scopus search
string was 43 of 332 documents. In total 97 sources were used as references
throughout the report, whereas 54 were acquired through the snowball method. Any
literature that were not an article in the scopus search term were classified as part of
the snowball referenced literature. Figure 2 includes the articles collected from
snowballing with the Scopus combined search string as the primary data collection
method.
Figure 2.
Total articles from the combined Scopus search and snowballing data collection
method

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 18



3.3 Analysis of documents
The analysis was to categorize the energy carriers relevant to the port operation’s part
of the supply chain. The following categorization areas were investigated: storage,
transportation & distribution, and bunkering. This categorization was essential in
order to have a deeper understanding of the different roles alternative fuels have in the
context of port operations. The information and data gathered relevant to each
categorization area from studies were compiled and written down in this report.

By gathering data on the different categorization areas, insights into each alternative
fuel could be gained and used for comparison. For example, it was found that the
economic and cost aspects were of great importance when choosing an alternative fuel
for shipping. Articles connected to cost and economic analysis were thereafter
organized according to the categorization. E.g., if a document mentioned transport
cost, it was written in the transport section of the corresponding energy carrier. The
cost used in the comparison Figures 5, 6, and 7 were based on articles using transport
cost that was able to be converted into USD/GJ. If there was no given distance in the
data, it was not used in the comparison. There were other documents that mentioned
the transport cost of alternative fuels. However, due to the diversity of available cost
metrics and data limitations, the decision was to only use data such as USD/GJ,
EUR/kgH2, and USD/kgH2. These metrics were most consistently used in literature
and allowed for convenient direct price comparisons between other alternative fuels.
An additional factor that had to be considered and included in the transportation cost
formula was transportation distance due to the various available transportation modes
that can be utilized for fuel transportation. In the end, out of the extensive literature
review conducted, only a limited number of documents met the mentioned criteria for
the comparison of transport costs. These documents provided valuable data on the
different cost aspects of the alternative fuels as well as the showing the economic
implications of transporting these alternative fuels

The metric used for comparing transportation was USD/GJ/10 000 km. Using 10 000
km instead of 1 km eliminates decimals, which improves the readability of Figures.
Furthermore, if the original currency was in EUR it was changed to USD. It was done
by dividing the original value by the EUR to USD conversion rate (0,92). The rate
used was retrieved on 16/05 - 2023 from Google Finance (2023). Moreover, kg H2
was converted to GJ using the LHV (Lower heating value) for one kg of hydrogen
(0,12 GJ), i.e., kg h2 = 0,12 GJ. Thereafter it was divided with USD/kg H2 resulting in
USD/GJ. When the cost was calculated, it was then sorted into transport mode and
energy carrier.

To compile information a summary of the main challenges was created. The
challenges are listed in Tables 8, 9, 10, and 11. The information was taken from the
reviewed documents and was listed if relevant to challenges.

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 19



4 Results and analysis
The thesis was based on a literature review method. Therefore, the data consisted of
documents such as reports and articles. To gather documents for the thesis a search
string was used in the citation database Scopus. After the reviews of the publications,
43 documents were used in the thesis that originated from the Scopus search string.
As seen in Figure 3, the documents were classified according to the type of energy
carrier and after that, storage, bunkering, transport & distribution, infrastructure, and
others. The” Other” are regarded as topics indirectly relevant to the research question,
not concerning the port infrastructure, transport and distribution, and bunkering of
hydrogen, methanol, and ammonia. E.g. It could include sources focusing on
conventional fuels used as a comparison to alternative fuels in this study. The
documents were categorized after relevant energy carriers, which resulted in 48
hydrogen-, 20 methanol-, 35 ammonia-, and 20 other documents. 

Figure 3. 
The Number of Scopus publications is segregated into Storage, Bunkering, Transport
& Distribution, and Infrastructure.

Note. The total of publications for each fuel was: 48 for hydrogen, 20 for methanol,
35 for ammonia, and 20 others.

The literature from the Scopus database search term combined with the literature from
snowballing consisted of publications from different years. Figure 4 illustrates the
focus of this literature review, as well as the insights into the total literature
distribution across the energy carriers: Hydrogen, Methanol, and Ammonia, as well as
Other topics. As seen in Figure 4, the majority is hydrogen-related literature, followed
by ammonia and lastly methanol. This data imbalance shows that more hydrogen and
ammonia publications were gathered from both the Scopus search term as well as
snowballing. Another note is that most literature used in this study was published in
recent years.

Figure 4.
CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 20



Literature publications per year

Note. The x-axis shows the years from 2009 to 2023, while the y-axis shows the
number of publications. 

4.1 Challenges with hydrogen, methanol, and ammonia
4.1.1 Hydrogen
The main technical challenges associated with the fuel supply chain of hydrogen is
due to its low density and explosive nature. This makes storage, distribution, and
bunkering difficult compared to other fuels. Hydrogen storage is required at the
production facility and also at the ports before bunkering. Hydrogen can be stored in
tanks, either as liquid or compressed. Furthermore, liquid hydrogen has a density of
70,8 kg/m3, while compressed hydrogen has a lower density of 39 kg/m (Aziz &
Nandiyanto, 2020).

Furthermore, compressing hydrogen leads to energy losses of 10% - 20% (Panić et al.,
2022). On the other hand, liquefying hydrogen could result in up to 35% energy losses
(Panić et al., 2022; Santos, 2022). Liquid hydrogen is 10 times more expensive than
compressed hydrogen when considering storage (Deveci, 2018). Furthermore,
according to IRENA (2022) liquid hydrogen value chain needs 2,5 higher investments
than the ammonia value chain.

Several studies emphasize the need for larger storage facilities at port for the shift to a
hydrogen economy, which includes storage methods other than conventional tanks
(Aziz & Nandiyanto, 2020; Amirante et al., 2017; Davis et al., 2018; Nazir et al.,
2020; Osman et al., 2021). Studies have explored different options for the storage of
hydrogen, such as salt caverns, tanks, oil & gas reservoirs, water aquifers, liquid
organic hydrogen carriers (LOHC), depleted hydrocarbon reservoirs, metal hydrides,
and natural clay with pores, but these need testing (Deveci, 2018; AbouSeada &
Hatem, 2022; Osman et al., 2021; Aakko-Saksa et al., 2023; Santos, 2022; Panić et

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 21



al., 2022; Rangel et al., 2022; Amirante et al., 2017; IEA, 2019). For long-term
storage and large volumes, caverns are economically beneficial compared to tanks. 

For distribution, the main challenge is related to the lesser volumetric energy density
that hydrogen delivers less energy per liter compared to other fuels (Aziz &
Nandiyanto, 2020). Like other fuels, transportation of hydrogen tankers (trucks, trains,
and vessels) and pipelines can be used (Genovese & Fragiacomo, 2023; Freer et al.,
2021; Buchenberg et al., 2023; Collis & Schomäcker, 2022). Moreover, for
long-distance and larger volumes pipelines and shipping are the most efficient
options. However, pipelines are capital expenses (Capex) intensive. One option is
using existing natural gas pipelines that could be repurposed for hydrogen usage to
decrease Capex (IRENA, 2022; Saeedmanesh et al., 2018; Ravi & Aziz, 2022). 

There are no bunkering-specific regulations for hydrogen (Halim et al., 2018; Ustolin
et al., 2022; Tvedten & Bauer, 2022; Latapí et al., 2023). Currently, there are four
main types of bunkering methods for hydrogen (Ustolin et al., 2022). Truck to ship,
ship to ship, bunker stations, and swappable containers. Hydrogen can be used in both
liquid, compressed, metal hydrates and LOHC for bunkering (Ustolin et al., 2022;
Hyde & Ellis, 2019). Furthermore, according to Ustolin et al. (2022) only two liquid
hydrogen bunkering facilities exist. The summarized main challenges for hydrogen
can be seen in Table 6 and 7 below.

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 22



Table 6.
Techno-economic challenges with compressed hydrogen

Challenges with compressed hydrogen

Area Technical Economical

Storage ● Low density 39 kg/m3 requires large storage
facilities (Aziz & Nandiyanto, 2020; Davis et
al., 2018; Nazir et al., 2020; Osman et al.,
2021)

● Compression leads to 10% - 20% losses of
energy (Panić et al., 2022)

● Compression differences depending on the
end users (Panić et al., 2022)

● Increasing demand lead to increased need for
material (Aakko-Saksa et al., 2018)

● Leakage of hydrogen (Osman et al., 2021)
● Storage options as oil & gas reservoirs, water

aquifers, depleted hydrocarbon reservoirs,
metal hydrides and natural clay with pores
need testing (Osman et al., 2021; Santos,
2022; Panić et al., 2022; Rangel et al., 2022;
Amirante et al., 2017; IEA, 2019)

● Large scale storage options as salt caverns,
oil & gas reservoir and water aquifers
requires additional costs (Deveci, 2018;
AbouSeada & Hatem, 2022; IEA, 2019)

● Geographical locations storage are
economically beneficial compared to tanks
when large volume is needed to be stored
(Deveci, 2018; IEA, 2019)

● Up to 20% energy losses at compression
(Panić et al., 2022)

Transport & distribution ● Safety concerns as risk of explosion, risk of
fire, tasteless, odorless, colorless and
hydrogen embrittlement (Panić et al., 2022;
Osman et al., 2021; Wang et al., 2023;
Mazloomi & Gomes, 2012; Saeedmanesh et
al., 2018; IRENA, 2022)

● Demand needs to increase in collaboration
with supply (Latapí et al., 2023)

● Usage of pipeline when transporting large
volumes is cost efficient, however more
Capex intensive compare to other alternatives
(Buchenberg et al., 2023; Collis &

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 23



● Natural gas pipelines could be used for
hydrogen but there could be energy losses as
the distance of compression stations are not
optimized (IRENA, 2022; Saeedmanesh et
al., 2018; Ravi & Aziz, 2022)

● Usage of liquid organic hydrogen carriers
(IEA, 2019; Aakko-Saksa et al., 2023;
Santos, 2022)

● Leakage and compression issues due to
light-weight (Capurso et al., 2022; Osman et
al., 2021)

Schomäcker, 2022; Genovese & Fragiacomo,
2023)

● Pipelines efficient at 100 km than shipping,
however for distances over 2500 km shipping
cost less (d’Amore-Domenech et al., 2023)

● Repurposing natural gas pipelines lowers the
Capex compared to constructing new
infrastructure (IRENA, 2022)

● Using existing natural gas pipelines requires
additional compression stations or losses of
energy occurs (Saeedmanesh et al., 2018;
IRENA, 2022)

Bunkering ● No bunkering regulations and limited
bunkering capabilities (Halim et al., 2018;
Ustolin et al., 2022; Tvedten & Bauer, 2022;
Latapí et al., 2023)

● Demand need to rise or else there is no
incentive for hydrogen bunkering facilities
(Steen et al., 2022)

● Lack of bunkering facilities increases costs
(Ustolin et al., 2022; Latapí et al., 2023)

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 24



Table 7.
Techno-economic challenges with liquid hydrogen

Challenges with liquid hydrogen

Area Technical Economical

Storage ● Low density 70,8 kg/m3 requires large
storage facilities (Aziz & Nandiyanto, 2020;
Amirante et al., 2017; Davis et al., 2018;
Nazir et al., 2020; Osman et al., 2021)

● Cryogenic tanks for storage and need to
withstand ice formation as liquid hydrogen
requires -252,9 Celcius to be liquified (Panić
et al., 2022; Deveci, 2018; Ustolin et al.,
2022; Santos, 2022; Genovese &
Fragiacomo, 2023; Mazloomi & Gomes,
2012)

● Energy losses up to 35% at conversion to
liquid hydrogen (Panić et al., 2022; Santos,
2022)

● Increasing demand lead to increased need for
material (Aakko-Saksa et al., 2018)

● Highest energy loss cost from BOG when
stored in liquid state (Al-Breiki & Bicer,
2020)

● Cost up to 10 times more than compressed
hydrogen to store (Deveci, 2018)

● Large scale liquefaction units to be beneficial
(Buchenberg et al., 2023)

● Up to 35% energy losses at liquefaction
(Panić et al., 2022; Santos, 2022)

● Storage capacities for liquid hydrogen needs
to expand as the demand rises (Aakko-Saksa
et al., 2018)

Transport & distribution ● Usage of liquid organic hydrogen carriers
(IEA, 2019; Aakko-Saksa et al., 2023;
Santos, 2022)

● Due to the cryogenic nature, transportation
storage is limited (Genovese & Fragiacomo,
2023; Mazloomi & Gomes, 2012)

● Suffers from boil-off and evaporation
(Aakko-Saksa et al., 2018; Hinkley, 2021)

● Demand needs to increase in collaboration
with supply (Latapí et al., 2023)

● Highest transportation cost among compared
AF at 3,24 USD/GJ (Al-Breiki & Bicer,
2020). 

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 25



Bunkering ● No bunkering regulations and limited
bunkering capabilities (Halim et al., 2018;
Ustolin et al., 2022; Tvedten & Bauer, 2022;
Latapí et al., 2023)

● Demand needs to rise or else there is no
incentive for hydrogen bunkering facilities
(Steen et al., 2022)

● Lack of bunkering facilities increases costs
(Ustolin et al., 2022; Latapí et al., 2023)

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 26



 4.1.1.1 Storage
Hydrogen requires large tanks for storage due to its low density (Davis et al., 2018;
Nazir et al., 2020; Osman et al., 2021). Tanks located on land are required to be
placed in an area with ventilation and where it is not exposed to temperatures over
500℃ (Panić et al., 2022). The discharge rates are high for tanks and their efficiency
is around 99% (IEA, 2019). Storage tanks are commonly used for smaller scales
within hydrogen.

For compressed hydrogen, the normal pressure for storage is between 200 bar to 1000
bar, depending on safety requirements and end users (Panić et al., 2022). Furthermore,
compressing hydrogen leads to energy losses of about 10% to 20%. According to
Panić et al. (2022) within the automotive industry, the pressure of compressed
hydrogen is 700 bar due to storage limitations. Whereas, on short-sea, the pressure of
hydrogen is lower than in the automotive industry due to safety concerns and hazards
(explosions, risk of fire, and storage systems for highly compressed hydrogen).
Compared to LNG, liquified hydrogen requires 2,8 times the volume to store. The
normal pressure for the storage of liquid hydrogen is 6 bar. Furthermore, it requires a
temperature of -252,9℃ and cryogenic tanks (Panić et al., 2022; Genovese &
Fragiacomo, 2023; Mazloomi & Gomes, 2012). The cryogenic tanks are
double-walled containers composed of steel to withstand the temperature of liquid
hydrogen (Deveci, 2018; Ustolin et al., 2022). When the conversion of hydrogen to
liquid hydrogen occurs density increases but it results in energy losses (Panić et al.,
2022). Up to 35% of the total energy of the liquified hydrogen can disappear (Panić et
al., 2022; Santos, 2022). Furthermore, IRENA (2022) estimates the development of a
liquid hydrogen value chain needs investments up to 2,5 times higher than the whole
ammonia value chain is needed.

Challenges with liquid hydrogen storage are that the storage unit needs to withstand
low temperatures and ice formation leading to the rupture of the unit and equipment
(Panić et al., 2022; Santos, 2022). Moreover, liquid hydrogen evaporates leading to
higher pressure in the tank. Therefore, the need for releasing excessive hydrogen into
the air and thus losing energy. Comparing liquid and compressed hydrogen in
application in a vehicle, liquid hydrogen performs better due to the higher energy
content in the same volume. However, as it requires cryogenic storage tanks the usage
would not be feasible depending on transportation devices, e.g., road vehicles (Ravi &
Aziz, 2022). Moreover, Deveci (2018) mentions that the cost of liquid hydrogen
storage is about ten times the cost of compressed hydrogen storage. A technical
challenge that would occur if the hydrogen demand increases is that storage capacities
also need to expand (Aakko-Saksa et al., 2018). If the demand was to increase to 410
Mt hydrogen annually the material needed for storage capacity would be equal to 7
500 Mt of material. Most of the materials needed are common in the Earth’s crust, but
the rarest would be gold, rhodium, and tellurium. 

A large-scale and long-term storage option for hydrogen is salt caverns (Deveci, 2018;
AbouSeada & Hatem, 2022; IEA, 2019). Currently, natural gas is stored in salt
caverns, but they are applicable for the storage of hydrogen. As most caverns are
large, they provide economies of scale, low land cost, and low operational expenses
(Opex). Therefore, it can be the cheapest long-term storage option for hydrogen.
Moreover, the advantages of salt caverns are low risks of contaminating hydrogen,

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 27



sealing the hydrogen well, and offering high efficiency. Another storage alternative is
depleted oil and gas reservoirs. Comparing reservoirs and salt caverns. the reservoir
has the possibility of storing larger volumes of hydrogen. However, the reservoirs
would need cleaning and removing previous content, before storage of hydrogen.
Water aquifers can also be used for the natural storage of hydrogen, but exploration
and development costs would most likely occur. Both oil and gas reservoirs and water
aquifers store the gas deep underground. Risks are contamination and loss of
hydrogen, due to hydrogen reacting with fluids, rocks, and microorganisms. For both
last-mentioned storage mediums, the cost and feasibility are unknown. The
geographical location also matters due to salt caverns, water aquifers, and oil and gas
reservoirs are geographical findings (AbouSeada & Hatem, 2022).

Osman et al. (2021) mention the option of using depleted hydrocarbon reservoirs,
which have advantages such as large storage capacity, proven seal, and existing
infrastructure (natural gas pipelines). On the other hand, there are also disadvantages,
such as the possibility of hydrogen reacting with microorganisms and chemicals,
resulting in contamination. Furthermore, as H2 has a low density, it is also lightweight.
Therefore, there is a risk of leakage, due to the buoyancy forces. Transferring
hydrogen into ammonia is also a viable option for storage and distribution due to it
being easier to handle. However, the conversion leads to a loss of energy and may not
be economical for large volumes (AbouSeada & Hatem, 2022; Pawar et al., 2021;
Ravi & Aziz, 2022).

The choice of storage method depends on the volume needed to be stored, the
required speed of discharge, duration, and geographical location (IEA, 2019).
Geographical locations such as caverns, oil and gas reservoirs, and water aquifers are
better suited for long-term storage, while tanks are better for short-term storage.
Considering if a higher volume is needed to store, geographical locations are more
economically beneficial (Deveci, 2018). However, compared to natural gas, hydrogen
is expensive to store, due to the volumetric energy density being almost a third of
natural gas. 

Another option for storing hydrogen is using LOHC (Aakko-Saksa et al., 2023;
Santos, 2022; IEA, 2019). The concept is not widely proven (exists in Germany and
Japan) but has potential due to it safely storing hydrogen without losses (Aakko-Saksa
et al., 2018; Santos, 2022). LOHC are solids or liquids that can be reversibly
hydrogenated and de-hydrogenerated with elevated pressure and temperature to
release or absorb hydrogen, e.g., methanol. Meaning that standard liquid storage tanks
can be used and storage of hydrogen for extended periods without energy losses can
be achieved (Santos, 2022; IEA, 2019). However, there are some challenges, such as
using ammonia borane as a LOHC to replace 10% of the global energy supply
requires more boron than its global reserve (730 Mt needed while the global reserve is
at 110 Mt). Another challenge is that the technology is new and there is limited
experience. There are also losses of hydrogen ranging between 35% to 40% when
converting to a LOHC (IEA, 2019). Furthermore, the carrier's molecules remain when
extracting the hydrogen and they are needed to be transported again.

Hydrogen can also be stored in metal hydrides (Panić et al., 2022; Rangel et al., 2022;
Amirante et al., 2017). A drawback of using this technique is the cost of material and
the hydrogen content per weight (12,5 kg metal stores 1 kg hydrogen). The benefits
include lower service costs, compact storage (200% higher density), and making
CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 28



storage of hydrogen safer. Furthermore, natural clay with pores can be used as
hydrogen storage. As the nanomaterial is cheap, durable, biocompatible, and most
importantly has a high hydrogen storage capability. Pristine nanotubes made from
clay can store up to 0,22% of hydrogen weight, but if the nanoparticles are up to 5%
the stored hydrogen can be equal to 2,88% of the hydrogen weight. 

4.1.1.2 Transportation and distribution
Presently, there are a few logistical challenges connected to hydrogen, such as
transportation and distribution. An approach to hydrogen distribution to land-based
vessels is a hydrogen refueling station (HRS). The hydrogen stored can either be
liquid or gaseous and the supply can be produced on-, off-site, or a combination of
both. In 2020 there were 553 HRS for road vehicles in the world (Wang et al.,
2022b). 

An off-site use, e.g., pipelines or tankers (road, rail, or ship) to distribute the hydrogen
in either gas or liquid form (Freer et al., 2021). Liquid hydrogen is today not
transported through pipelines as it needs to be stored in a cryogenic environment
(Genovese & Fragiacomo, 2023; Mazloomi & Gomes, 2012). Furthermore, liquid
hydrogen requires large-scale liquefaction units to be economically beneficial
(Buchenberg et al., 2023). Trucks often carry hydrogen in pressurized tubes which
could lower emissions due to less energy required to keep hydrogen in gas form
(Genovese & Fragiacomo, 2023). On the other hand, transporting hydrogen through
pipelines is an economically beneficial approach when large quantities are distributed.
The initial investment however is more Capex intensive due to establishing new
infrastructure with pipelines, compared with the Capex of road transport (Buchenberg
et al., 2023; Collis & Schomäcker, 2022; Genovese & Fragiacomo, 2023). Thus, the
pipelines offer a lower emission alternative eventually depending on the scale of
volume transported. Furthermore, one challenge is that pipelines are only efficient
when the demand and supply are coordinated (IRENA, 2022). The cheapest cost for a
large pipeline requires almost the same hydrogen demand as the pure hydrogen
demand of Northwest Europe. 

However, repurposing existing natural gas pipelines into hydrogen pipelines could
decrease investment costs and expedite the shift to hydrogen (Ravi & Aziz, 2022;
IRENA, 2022). According to IEA (2019), there were approximately 3 million km of
natural gas pipelines established in 2019, whereas there were around 5 000 km of
hydrogen pipelines. One challenge with repurposing natural gas pipelines is the ideal
distance of gas compressors (IRENA, 2022). Resulting in a trade-off between
investments in optimizing the distance for compression stations or higher energy
losses due to not ideal compression (Saeedmanesh et al., 2018; IRENA, 2022).
Another challenge is hydrogen embrittlement occurring in pipelines, which happens at
high compression of hydrogen (Panić et al., 2022; Osman et al., 2021; Saeedmanesh
et al., 2018; IRENA, 2022). Additionally, if the natural gas pipelines are used the
demand for natural gas needs to decrease at the same time as hydrogen demand
increases. Furthermore, the same volume of natural gas contains three times the
energy of hydrogen, resulting in a need for larger flows of hydrogen (IEA, 2019).
Lastly, an individual assessment is required for each pipeline network, as conditions
vary from place to place, such as age, operating point, material, and maintenance
(IRENA, 2022).

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 29



The authors d’Amore-Domenech et al. (2023) calculated the cost of transporting
hydrogen (including loading and unloading). For short distances (100 km) the pipeline
offers the most economically beneficial mode of transport. For medium distances
(2500 km) compressed hydrogen shipping was the best alternative at flow rates of 100
kt/year, while for 1 Mt/year it is equal between liquid- and compressed hydrogen
shipping and for 10 Mt/year liquid hydrogen is better (d’Amore-Domenech et al.,
2023). When it comes to distances of 5 000 km the best solution is to ship liquid
hydrogen for 1 Mt/year and 10 Mt/year, while the cost is similar between shipping
liquid and compressed hydrogen at 100 kt/year.

Furthermore, Collis and Schomäcker (2022) estimated that pipelines could be worth
the high investment costs when big volumes (1 mt/year) are transported within local
or regional distances approximately (pipeline length up to 1120 km). In addition,
Monte Carlo simulations show that pipelines (1080 - 1120 km) tend to be more
economically viable when big volumes are transported within local or regional
distances (Collis & Schomäcker, 2022). There are currently 4500 km of hydrogen
pipelines in operation worldwide with operating pressures between 10 - 20 bars and
diameters between 25 - 30 cm (Capurso et al., 2022). The average construction cost
for these hydrogen pipelines was estimated to be 854 000 USD/km, which is up to
20% more expensive than natural gas pipelines (Capurso et al., 2022). The higher cost
is due to the larger diameters required for the pipelines, leaks, and
compression-related issues due to the hydrogen’s low molecular weight (Capurso et
al., 2022). Furthermore, according to Ravi & Aziz (2022), the developing hydrogen
market's estimated to cost 210 to 550 billion USD for HSR and pipelines by 2050.
This investment is expected to meet 24% of the global energy demand with
hydrogen. 

Another challenge with liquid and compressed hydrogen is that it suffers from BOG
and evaporation during transportation and storage (Aakko-Saksa et al., 2018; Hinkley,
2021). It is estimated that around 1% to 5% is lost daily during truck transport and
0,3% in a tanker that contains about 4 tons of hydrogen. In various cases, the losses
can be minimized with the usage of vaporized hydrogen at the same time, but as
mentioned by Aakko-Saksa et al. (2018), this requires an ongoing operation.
Therefore, LOHC would be a better option to use when transporting hydrogen. As it
does not lose hydrogen in transport. LOHC can be transported using conventional oil
product tankers for longer distances (IEA, 2019). However, the challenge is that it
needs to react before releasing hydrogen (Aakko-Saksa et al., 2018). Furthermore, the
cost of transporting LOHC 50 km was calculated to cost 0,414 Euro/kg hydrogen,
which includes hydrogenation and hydrogen release (Aakko-Saksa et al., 2018).

Shipping hydrogen is most efficient for large volumes of liquid hydrogen transported
over long distances (Collis & Schomäcker, 2022). Al-Breiki and Bicer (2020)
compared the transportation costs of LNG, liquid ammonia, methanol, and liquid
hydrogen via an ocean tanker from Qatar to Japan (12 000 km). The cost of
transporting each energy carrier was estimated by summing the Capex of a tanker, the
Opex of the voyage, and the energy loss costs from boil-off. The ocean tanker was
assumed to run on HFO and fuel costs were based on 2020 HFO market prices. As
shown in Table 8 hydrogen and respectively LNG has the highest Capex due to the
need for more expensive insulating materials. Costs from BOG were also significantly
higher for hydrogen. Transportation Opex for hydrogen is however the lowest of all
CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 30



the AFs compared, due to less mass of hydrogen able to be loaded. The hydrogen
transportation cost from Qatar to Japan is estimated to be the highest at 3,24
USD/GJ. Hydrogen has the ability to be transformed into hydrogen carriers, such as
methanol and ammonia (Cui & Aziz, 2023). As hydrogen has a lower density than
both methanol and ammonia and therefore it is beneficial to transport hydrogen by
using a hydrogen carrier.

Table 8.
Transportation cost (USD/GJ/12000 km) for maritime transportation of LNG,
ammonia, methanol, and hydrogen from Qatar to Japan (Adapted and modified from
Al-Breiki & Bicer, 2020)

Unit LNG Ammonia Methanol Hydrogen
Ship capacity m3 160 000 160 000 160 000 160 000

Capacity
Metric
ton 67 696 109 248 128 800 11 376

Voyage distance km 12000 12000 12000 12000
Vessel capital costs MM$ 192 162 120 216
Operational costs

Required fuel (HFO)
Metric
ton 7327,54 11825,21 13941,55 12737,9

Fuel cost (HFO) MM$ 4,2 6,8 8,0 0,7
Maintenance (4%
Capex) MM$ 7,68 6,48 4,8 8,64
Insurance (15%
Opex) MM$ 1,782 1,992 1,92 1,401
Misc costs (10%
Opex) MM$ 1,188 1,328 1,28 0,934
Total Opex MM$ 14,85 16,6 16,0 11,675
BOG during
transportation

Metric
ton 25491,0 8570,3 202,1 37838,9

Cost of BOG MM$ 7,3 4,5 0,67 54
Transport cost $/GJ 0,74 1,09 0,68 3,24

Note. BOG costs are based on energy lost to BOG during transportation and market
prices of the energy carriers of various sources. All fuels are in a liquid state. 

Furthermore, IEA (2019) compares the cost of transporting hydrogen by using ships,
pipelines, and trucks. The comparison contains hydrogen (liquid in vessels and
compressed in pipelines), LOHC, and ammonia. The costs include storage,
transportation, liquefaction, and conversion when it is applicable for the different
hydrogen carriers. At a distance of 1500 km, hydrogen costs less to transport with
pipelines and LOHC costs less when using a vessel. However, IEA (2019) mentions
that the cost of transporting hydrogen through pipelines is expensive for long
distances due to more compression stations needed compared to ammonia. The least

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 31



expensive alternative was LOHC to transport hydrogen at 1500 km by ocean vessel.
The data from IEA (2019) was compiled in Table 9 below.

Table 9.
Transport cost for hydrogen, ammonia and LOHC (IEA, 2019)
1500 km Hydrogen Ammonia LOHC
Pipeline (USD/ kgH2 ) 1 1,58 -
Ship (USD/ kgH2 ) 2 1,2 0,6

Another report estimates the levelized shipping cost for transportation of hydrogen,
LOHC and ammonia in EUR/kg H2/10 000 km (Wang et al., 2021). The levelized cost
of transportation of the hydrogen carriers is approximately 0,78 to 1,31 EUR/kg H2/10
000 km for liquid hydrogen, 0,83 EUR/kg H2/10 000 km for ammonia, and 0,76
EUR/kg H2/10 000 km for LOHC (Wang et al., 2021).

An additional cost is using compressing or liquefaction to store hydrogen, which can
cost 0,1 USD to 4 USD/kg hydrogen (Aakko-Saksa et al., 2018). The cost fluctuates
depending on the transport mode (tanker or pipeline) and if hydrogen is compressed
or liquid. While only considering transport, the cost of transporting hydrogen in tubes
on a truck is estimated to be 1,5 USD to 3 USD/kg hydrogen for around 250 - 750kg
hydrogen per day in a distance of 100 to 300 miles (Aakko-Saksa et al., 2018).

4.1.1.3 Bunkering
Currently there are no specific regulations or designs and limited bunkering
capabilities for hydrogen vessels (Halim et al., 2018; Ustolin et al., 2022; Tvedten &
Bauer, 2022; Latapí et al., 2023). Resulting in innovation, as the technology is needed
to be tested before usage. Otherwise, regulation can become a barrier that hinders the
technological development of new innovations. Furthermore, the process of bunkering
with conventional fuels is simple, while hydrogen bunkering is a new process,
requiring other safety measurements. Moreover, a demand for hydrogen as a fuel is
needed or else there will only be a stored supply of the energy carrier, but no users
(Latapí et al., 2023). Since the infrastructure to deliver hydrogen is not currently
broadly available in most ports, the costs are high. To lower the price and attract users
the prices need to decrease and the availability and volume of hydrogen need to
increase. 

Ustolin et al. (2022) mention that there are four main types of bunkering for
hydrogen: 

1. Truck to ship, where a truck with tanks (liquid) or tubes (gaseous) connects to
the vessel to bunker the vessel. The advantages are that it is flexible and less
initial investments than a bunkering station as there is no need for fixed
storage units. 

2. Ship to ship, where a ship refuels another ship. Advantages are flexibility, that
operation is not bound to happen when it is docked, the operation can occur at
sea or at longer distances, and infrastructure needed to fill the vessels are only
required. However, the need to invest in a bunker vessel is needed. 

3. Bunker station, a fixed structure at a port. This option has a fixed structure and
infrastructure and contains large amounts of hydrogen. 

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 32



4. Swappable containers, a flexible option but not optional when larger volumes
of fuel are needed. However, this option should not be used within liquid
hydrogen bunkering due to the risk of raising up the containers and their
contents. 

Furthermore, as of 2022, there were only two existing liquid hydrogen bunkering
facilities (Ustolin et al., 2022). In Australia, the Port of Hastings, and in Japan, the
Port of Kobe. These are used for the same project. The lack and future uncertainty of
hydrogen availability and supply can be attributed to the shipowner’s lack of
investment in hydrogen-fuelled vessels (Steen et al., 2022). For example, the first
hydrogen-powered ferry to be launched in Norway will rely on liquefied hydrogen
transported from Germany, as it is simply meaningless to produce hydrogen locally
before a market exists. Increasing hydrogen distribution and storage infrastructure
may encourage shipping companies to invest in hydrogen-powered ships, which in
turn may encourage more investments in bunkering infrastructure (Steen et al., 2022).
This is also applicable for terminals within ports, if the supply of hydrogen is lacking
and bunkering facilities, there is no need to buy hydrogen-powered equipment
(Densberger & Bachkar, 2022). 

According to Hyde & Ellis (2019) the bunkering options depend on the storage
methods, such as gas, liquid, metal, and LOHC. For hydrogen in gas form, the flow
rate is needed to be monitored to avert adiabatic heating. Either pressure balancing or
compressing gas onto the ship are two alternatives for gas hydrogen to be bunkered
onto the vessel. For the first gas alternative, if the gas stored at the port is at a higher
pressure than the vessel a valve should be opened allowing the fuel to flow from port
to vessel by its own pressure. This technique requires a large storage capacity at the
port, as when the pressure drops under the vessel's pressure area the bunkering
method is unable to fill up the rest of the vessel's storage. Therefore, using the cascade
method, where several smaller tanks or storages with higher pressure are used for
bunkering solves this problem. Furthermore, the benefit of using the pressure
balancing approach is that it does not require any compressors. 

The second method for hydrogen is compressing the gas into the vessel. In this
approach, a throughput compressor is used for moving the fuel from the port to the
vessel tank (Hyde & Ellis, 2019). As a compressor is used the hydrogen at port is not
required to be pressurized at the same amount as the method before, only to a lower
degree. This method allows the hydrogen flow to be controlled and monitored
carefully. The downside is that it requires expensive equipment to work. 

Since, liquid hydrogen requires regulations of the temperature, cryogenic pumps are
used when transferring to a vessel (Ustolin et al., 2022; Hyde & Ellis, 2019). The
same technique is used when bunkering LNG, therefore the approach is relatively
understood. For metal hydrides, the approach would be to store compressed hydrogen
at the port and transfer it to the vessel using one of the mentioned methods for
gaseous hydrogen. Thereafter, heat extraction is required from the place of storage.
This is to allow the hydrogen to enter the metal matrix. The last method that Hyde &
Ellis (2019) mentions is the usage of LOHC. Storage happens in port, happens on the
docks, and is transferred through pumps. Furthermore, de-hydrogenated oil from the
vessel is stored at the port after removal.

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 33



4.1.2 Methanol
Methanol is a well-established alternative fuel, as it has a widespread distribution and
storage capability and existing port infrastructure supporting methanol-powered
vessels (Kajaste-Rudnitskaja et al., 2018). For example, Stena Line’s vessel Stena
Germanica, the first commercialized dual-fuel methanol and diesel-powered ferry in
operation (Christodoulou & Cullinane, 2021; Kamaljit, 2016).  There are no major
technical challenges with producing and distributing methanol (Svanberg et al., 2018).
Thus, making it a viable AF for the maritime sector. Additionally, there are no
substantial issues within the supply chain to supply methanol as fuel for shipping. A
major techno-economic benefit is that methanol is liquid at room temperature with a
higher density than other analyzed AF. Resulting in easier handling and storage as
well as cheaper transportation costs than liquid hydrogen and ammonia and LNG
(Brynolf et al., 2014; Al-Breiki & Bicer, 2020). 

The current infrastructure used for traditional fuels can easily be modified to be
compatible with methanol (IRENA & Methanol Institute, 2021; Svanberg et al.,
2018). Most techno-economic challenges are attributed to its chemical properties,
such as the low flash point, its toxicity to humans, fire and explosion hazards (IRENA
& Methanol Institute, 2021; Svanberg et al., 2018; Paris MoU, 2022). Other
challenges can be connected to methanol’s lower energy density compared to fossil
fuels (diesel, gasoline, and LNG) as well as its lower boiling point (Brynolf et al,
2014; IRENA & Methanol Institute, 2021; Svanberg et al., 2018 ). This means
specialized storage methods are still required for methanol (Svanberg et al., 2018).
The identified main challenges with methanol are summarized in the Table below.

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 34



Table 10.
Techno-economic challenges with methanol

Challenges with methanol

Categorisation area Technical Economical

Storage ● Low flash point and toxic (IRENA &
Methanol Institute, 2021; Svanberg et al.,
2018)

● Tanks require extra “dead” space for thermal
expansion as methanol has the ability to
absorb moisture from the atmosphere
(IRENA & Methanol Institute, 2021)

● Fire & explosion hazards. Explosion-proof,
EX-classed equipment required (Paris MoU,
2022)

● Liquid storage preferred due to cost reasons
(IRENA & Methanol Institute, 2021)

Transport & distribution ● No major technical challenges with
distribution and production (Svanberg et al.,
2018)

● Cost of transporting methanol is
0,68USD/GJ, which is cheaper than
liquefied- hydrogen, ammonia and LNG
(Al-Breiki & Bicer, 2020)

Bunkering ● Lower energy density compared to diesel,
gasoline and LNG (IRENA & Methanol
Institute, 2021; Svanberg et al., 2018;
Brynolf et al., 2014)

● Less revamp needed to be compatible with
existing port infrastructure compared to the
other two AF (IRENA & Methanol Institute,
2021; Svanberg et al., 2018)

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 35



4.1.2.1 Storage
Despite being easier and more economically feasible to store and distribute than
hydrogen and ammonia, methanol still has techno-economic challenges regarding
storage, such as specialized storage methods (Svanberg et al., 2018; Paris MoU,
2022). Minimum requirements for storing methanol have been identified by Paris
MoU (2022) referencing the IGF code. For example, with fire safety in consideration,
explosion-proof, EX-classed equipment must be used. Additionally, methanol vapor
detection as well as liquid leak detection must be used in case of leaks as it can cause
asphyxiation in cramped areas. In addition, methanol is highly toxic, resulting in
exposure via inhalation, skin, and eye contact, or ingestion can be fatal and cause
blindness (IRENA & Methanol Institute, 2021). 

Methanol has a lower volumetric energy density in comparison to other traditional
liquid fuels (Brynolf et al., 2014). For example, it has about half the volumetric
energy density of diesel and gasoline. It also has a lower energy density than LNG.
This means more methanol must be stored and delivered to provide the same amount
of energy (IRENA & Methanol Institute, 2021; Svanberg et al., 2018). When
compared to ammonia and hydrogen, methanol has a moderate amount of energy
density as seen in Table 2. This means methanol shares the same energy density
disadvantages as the other two AFs. Furthermore, the tanks carrying methanol need to
be 2,5 times larger than oil tanks due to density and lower heating value when
comparing the same energy value (DNV GL, 2018). This combined with the special
requirements in accordance with the IGF code indicates storing and distributing
methanol have higher Capex and Opex costs than traditional fuels (Svanberg et al.,
2018). Moreover, methanol should be kept in sealed tanks with extra room for thermal
expansion as methanol has the ability to absorb moisture from the atmosphere
(IRENA & Methanol Institute, 2021).

Considering storage, methanol is less complicated and costly compared to LNG,
ammonia, and hydrogen, due to methanol being liquid at room temperature (Panić et
al., 2022). According to IRENA & Methanol Institute (2021), liquid storage is
preferred over gaseous as this would make the transition from liquid fossil-based fuels
easier and less costly. Due to being liquid at atmospheric pressure methanol can be
stored in a similar way to traditional bunker fuel, therefore it can be stored in all sizes
of storage units (Aakko-Saksa et al., 2018). Furthermore, existing port infrastructure
for traditional fuels, such as gasoline tanks, requires only slight modifications to be
compatible with methanol (IRENA & Methanol Institute, 2021; Svanberg et al.,
2018). A gasoline tank can be converted to be compatible with methanol by adding an
internal coating to the existing tank. Tank connections will also need to be updated,
and the tank will also need a nitrogen inertization system and new tank ventilation
(Ellis & Bomansson, 2018). Transitioning existing infrastructure to be fit for methanol
storage and distribution is therefore a significantly lesser economic and technical
barrier compared to the other two AFs and LNG. For example, the capital costs of
LNG tankers are estimated to be 40% higher than methanol (Al-Breiki & Bicer,
2020). 

4.1.2.2 Transportation and distribution
There are currently 12 vessels operating on methanol internationally. The shipping
company, Maersk, is also planning to have 8 container ships running on methanol

CHALMERS, Mechanics and Maritime Sciences, Master’s Thesis 2023:06 36



(Gore et al., 2022). Major ports such as Rotterdam and Antwerp already have
well-established infrastructure for the storage and distribution of methanol as a
chemical (Svanberg et al., 2018). Furthermore, methanol is easily made compatible
with existing distribution and storage infrastructure and can be blended with
traditional fuels leading to lower capital costs (IRENA & Methanol Institute, 2021).
In total, over 100 ports have methanol available for distribution. Due to its similar
characteristics to traditional fuels, methanol is rather uncomplicated to transport and
distribute via maritime vessels, trucks, and rails. Just like oil and its byproducts,
methanol may also be distributed through pipelines. The methanol transportation cost
from Qatar to Japan by ocean vessel was estimated to be the lowest when compared to
LNG, ammonia, and liquified hydrogen at 0,68 USD/GJ/12 000 km, as seen in Table
8 (Al-Breiki & Bicer, 2020). The highest value transportation costs of methanol via
ocean vessels inquired from the literature were based on estimations of Cui & Aziz
(2023). And were approximately 0,94 USD/GJ/10 000 km, significantly cheaper than
both ammonia and hydrogen. A complete comparison of the transport costs of the
various transport modes can be seen in Figures 5, 6 & 7.

The major technical and economic benefits of methanol can be attributed to its high
volumetric density, which means more methanol can be stored in the same size tanker
for transportation, compared to the other analyzed fuels (Aziz & Nandiyanto, 2020).
Finally, the low BOG costs due to met