Historical Context and Current State of Shipping Emissions
Shipping has been part of the global supply chain since the Industrial Revolution. Despite its importance in the international movement of products, the industry has had a debilitating effect on the environment, especially due to the production of greenhouse gases, which have exacerbated the impact of climate change. Though greenhouse gases have been accumulating in the atmosphere since the Industrial Revolution and before, it was only in 1988 that climatologists and scientists, using evidence from the 1960s and 70s, raised concerns to the international community about the effect of these gases on global warming. After the Intergovernmental Panel on Climate Change (IPCC) declared global warming a real and urgent environmental problem, industries, including the shipping industry, started evaluating their greenhouse gas production. The International Maritime Organization (IMO), formed under the UNFCCC’s Kyoto Protocol, is responsible for reducing the impacts of greenhouse gases from international shipping (IMO, 2015). The first IMO report was published in 2000, and it was estimated that international shipping was responsible for 1.8% of global anthropogenic CO2 emissions. Another report in 2009 showed that the worldwide shipping industry contributed 2.7% of the total CO2 emissions in 2007. 2014, the third report showed that the industry’s contribution was 2.2% in 2012 (Olmer et al., 2017). As of 2023, the global shipping industry contributed about 3% of global carbon dioxide emissions annually (Deng & Mi, 2023).
Owing to its studies, IMO has since 2011 been adopting measures to improve energy efficiency in the industry. In 2011, through the Marine Environment Protection Committee (MEPC), the organization adopted feasible strategies for greenhouse gas emissions and other marine pollutants. The organization 2011 adopted the resolution MEPC.203(62), the first legally binding instrument since the Kyoto Protocol. Under the resolution, IMO set technical and operational requirements such as the Energy Efficiency Design Index (EEDI) for new ships. The package sets the Ship Energy Efficiency Management Plan (SEEMP) for vessels and minimum energy efficiency for new ships. The enforcement of the requirements began in January 2013. In July 2016, MEPC 70 reviewed the EEDI Phase 3, which was supposed to commence in January 2025 and after (IMO, 2015). The agreement required ships to be built in 2025 and 30% more energy efficient afterwards. MEPC 74 of 2019 brought the EEDI Phase 3 requirements from 2025 to 2022 and set the energy efficiency level at 50% from 30% for different types of ships. In 2018, the IMO adopted resolution MEPC.304(72), an initial strategy to reduce greenhouse gas emissions from ships. The committee set out a future vision for the industry regarding greenhouse gas emissions. In the framework, the committee envisions minimizing the emissions from shipping by at least 50% by 2050, using 2008 as the base year (IMO, 2015). At the same time, the committee pursued strategies aimed at phasing the emission out entirely. The initiatives proposed and taken up by the IMO in collaboration with other environmental bodies have seen greenhouse gas emissions reduce over the years.
The environmental and climate change impacts of international shipping cannot be disputed. As mentioned, shipping activities contribute about 3% of global greenhouse gas emissions, with black carbon contributing a fifth (Owen-Burge, 2023). Greenhouse gases are known to be the greatest contributor to global warming and climate change. In addition to global warming, shipping activities are known to pollute seawater, which affects marine life. For example, an estimated 250 million tons of sewage and greywater are discharged by ships (Owen-Burge, 2023). Such wastes contain microplastics, bacteria and other contaminants that adversely affect the lives of marine animals. Shipping activities are thus a major threat to the environment and human health. Since the activities cannot be done away with, they should be regulated to mitigate their adverse environmental effects.
Research on Maritime Fuel Alternatives
Due to the increased concerns about the effects of global warming on the health of people and the environment, stakeholders in the shipping industry have been in the race to implement strategies to reduce the industry’s contribution to greenhouse gas emissions and marine pollution. Among the strategies considered are alternative energy solutions. The solutions that have been considered and tried to replace fossil fuels as ship fuels include first-generation alternatives like liquefied natural gas and liquefied biogas and second-generation alternatives like hydrogen, methanol and ammonia.
Liquefied natural gas (LNG), a first-generation alternative, is among the most recommended fuel alternatives for ships because of its greenhouse gas emission reduction capabilities. Liquefied natural gas produces virtually no sulfur dioxide. Additionally, the fuel, compared with other conventional energy forms, can reduce greenhouse gas emissions like carbon dioxide by 10% to 20%, nitrogen oxide by 80% to 90% and particulate matter by 98% to 100% (Xu et al., 2015). Studies have been commissioned to evaluate the viability and feasibility of LNG as an alternative fuel for ships. A study in 2011 established that, due to its competitive market price, LNG could become the widely adopted form of ship fuel. Ship owners’ survey study established that ship-source emissions regulating legislation could tremendously encourage the adoption of LNG (Xu et al., 2015). According to the survey, ship owners consider other low-sulfur fuels a short-term solution. At the same time, LNG is regarded as a long-term solution, especially for ships in liner shipping. Det Norske Veritas (DNV) report indicated that between 2018 and 2020, new ships will be propelled by LNG, with large liners being the biggest beneficiaries because of the economies of scale. Its noteworthy that LNG has been in use for large liners for over 40 years, with the greatest aim being the reduction of fuel and voyage costs (Wang & Wright, 2021). In the recent past, however, due to stricter legislation limiting greenhouse gas emissions, LNG adoption has reached other ships. For example, the number of LNG-powered vessels has been increasing since 2010. In 2010, only 18 LNG-powered ships were completed. The number, however, increased over the years to reach 175 in 2021. More than 200 vessels were on order as of 2020.
Despite the environmental sustainability advantages of LHG, some drawbacks limit its adoption as an alternative fuel. Among the leading limitations is cost (Wang & Wright, 2021). The LNG is mainly produced through anaerobic digestion. After production, the biogas contains high amounts of carbon dioxide and needs purification. Due to the utilization of energy and chemicals during the purification process, the purification costs are usually high, raising the price of the LNG.
The other alternative solution is second-generation fuels like hydrogen and methanol. The simplest and lightest element, hydrogen, has unique characteristics that make it a potential future fuel alternative for fishing. One of the greatest advantages of hydrogen is that it by-products harmless water and minute amounts of nitrogen oxide. Another advantage is that hydrogen can be produced from renewable sources such as nuclear power and biomass and non-biodegradable sources such as wind and solar. Thirdly, the energy density of hydrogen ranges between 120 and 142KJ/kg, implying a high energy-to-weight storage ratio (Wang & Wright, 2021). Over 75% of hydrogen is produced through steam methane reforming (SMR), with natural gas being the feedstock. Despite the advantages such as low-cost production and energy efficiency, hydrogen produces high greenhouse gas emissions. While cleaner hydrogen can be made using electrolysis using renewable sources of energy, the production has been low since it only constitutes 3.9% of global hydrogen production (Wang & Wright, 2021). Hydrogen is thus not a good alternative as far as global warming concerns are concerned.
Green Ammonia Production and Technology
In the era of increased anti-greenhouse gas emissions due to climate change resulting primarily from global warming, ammonia, a carbon-free compound, is increasingly becoming a fuel of interest for the shipping industry. Ammonia can easily be transported and stored compared to hydrogen. Compared with other flammable fuel sources, ammonia, with a flammability limit between 0.63 and 1.42, is considered generally nonflammable during transportation (Wang & Wright, 2021). Additionally, due to its strong odour, ammonia can easily be detected in case of leakage when being used as fuel. Haber Bosch process is the commonly used process of producing ammonia where atmospheric hydrogen and nitrogen are combined using iron-based catalysts under high temperature and pressure.
Methods of Ammonia Production
As mentioned earlier, the Haber Bosch process is the commonly used process of combining hydrogen and nitrogen to form ammonia. Unlike traditional methods, which use natural gas as the primary source of hydrogen, the green ammonia process uses electrolyzers to separate hydrogen and oxygen molecules in water. Electrolyzers are modular units that can handle low loads and can be started and stopped when the operator wishes. The electrolyzers are thus operationally highly flexible, making them best suited for the fluctuating output of renewable energy. When salty water is involved, desalinization is involved to purify the water before electrolysis. Electrolysis consists of the passage of water through direct electric current to decompose it into constituent hydrogen and oxygen molecules. Hydrogen so harvested can be stored in compressed or liquefied form. Nitrogen is harvested from the atmospheric air for use in the Haber Bosch process. Though there are several technologies for decomposing atmospheric air into its constituent elements, cryogenic distillation is the most preferred method in industrial nitrogen production. Cryogenic air separation units (ASUs) exploit different boiling point temperatures of nitrogen, oxygen and argon to separate air into the three components. During the Haber Bosch process, three volumes of hydrogen and one volume of nitrogen are passed through compression chambers to reach pressure between 20MPa and 40Mpa. The two compressed volumes are then introduced to a reactor. For increased reaction rate and acceptable yield of ammonia, temperature must be maintained at 450 degrees centigrade. To further increase the rate of reaction, the reactor contains iron-based catalysts.
Technological Advancements in Green Ammonia Synthesis
as found in the Haber Bosch process above, the process is energy-intensive, and the ammonia produced is not 100% carbon-free. Given this, technologies have been advanced to make the process more efficient and less energy-intensive while ensuring large-scale production of pure ammonia. The tested technologies aim to produce large quantities of pure ammonia to meet the increasing demand using low-energy processes. Scientists involved in the relevant industries are thus seeking to replace the Haber Bosch process in its entirety because of its inefficiencies. Among the technologies that are currently being tested is electrochemical synthesis of ammonia. The process utilizes renewable electrical energy to convert hydrogen obtained through electrolysis and nitrogen from the atmosphere into ammonia at reasonable temperature and pressure (Smart, 2022). Electrochemical ammonia has the potential to compete with the Haber Bosch process if it can be achieved at high efficiency at low overpotential. The technology is not, however, advanced beyond the laboratory level. The process is challenging from different fronts. First, nitrogen is an inert molecule, and thus, its electrolytic reduction requires significant energy amounts and a strong catalytic site. Due to the challenges associated with the process, it will take until 2050 for the process to compete with the Haber Bosch process.
Another technology is the photochemical ammonia synthesis. The chemical reactions in the process are driven purely by sunlight. All the materials used in the process are renewable as the energy comes from the sun, hydrogen from water and nitrogen from the atmosphere. Since there is no need for electricity, photochemical synthesis of ammonia is seen as the potent potential for decentralized off-grid ammonia synthesis (Smart, 2022). When well developed and matured, the two processes are seen as potential solutions to achieving enough quantities of pure ammonia for fertilizers and fuel.
Economic and scalability aspects of green ammonia production
The economics of green ammonia production lies solely on its primary contributors, which are the electricity used by the compressors, water for general cooling and refrigeration for ammonia separation (Osman et al., 2020). In comparison with blue ammonia (produced using hydrogen from natural gas), green ammonia is cheaper since the process of its prokWh/kg NH3duction uses mainly electricity (Salmon et al., 2023). For blue ammonia, while electricity contribution is non-dominant, increased costs come from refrigeration, cooling water and gas used for heating reactors. Despite the non-dominance of electricity in the blue process, the energy consumed in the blue process is about 70% higher than that consumed in the green process, that is, 2.2kWh/kg NH3 for the green process versus 3.7kWh/kg NH3 for the blue process (Ash & Scarbrough, 2019). Therefore, green ammonia is far cheaper than blue ammonia (Mayer et al.,2023). The cost of green ammonia can be determined by electricity costs in that when the electricity costs are high, the prices of green ammonia are high and vice versa.
When looking to scale green ammonia production, it is important to consider its contributors. From the exploration above, it is clear that electricity is the primary contributor to energy and that the costs of ammonia produced depend solely on electricity prices. For optimal production of green ammonia, the plants should be located in optimal sites characterized by ample land where sufficient renewable energy can be harvested. The unavailability of land constraints plant size, which eats into the economies of scale and can move production to suboptimal and expensive sites.
Green Ammonia in Marine Applications
ammonia as a fuel in shipping
Currently, there are no in-service ships propelled using ammonia as fuel since ammonia-fueled engines are yet to be commercially available, and the existing engines are not equipped for ammonia propulsion. Different options for ammonia energy-generating cells have been studied. De Vries, for example, studied internal combustion engines (ICE), solid oxide fuel cells (SOFC)), steam and gas turbines, and proton exchange membranes (PEMFC). All have been found feasible for use in marine propulsion. SOFC, however, is the most efficient despite the challenges of cost and large amounts of ammonia needed. ICE is the most applicable for marine propulsion because it is less costly, robust, and has acceptable power density and load response.
Current pilot projects and experimental vessels utilizing ammonia
As mentioned earlier, ammonia-powered ships’ engines are still under development, and no in-service ship currently operates on ammonia. The first clean ammonia-powered ship is expected to be launched in 2026 by Yara International (Yara International, 2023). Yara Eyde will operate between Norway and Germany. Yara Eyde is expected to provide clean marine transportation between Norway and Germany once it is in operation. The project is still underway, and its completion will open the door to more ammonia-powered engines for maritime transportation.
Technical considerations for retrofitting existing ships or designing new ammonia-powered vessels
Existing ship engines are not equipped with ammonia propulsion. Therefore, they cannot be retrofitted for ammonia propulsion. The only to realize ammonia propulsion is by designing new engines for new vessels. In designing an ammonia-powered ship, there is a need to understand the requirements of the ship’s propulsion system. Among the important technical considerations are the ship’s power requirements, the size of the proposed powertrain system, the mass and volume of the power generation system and the typical ship load profile (Di Micco et al., 2024). All the considerations are dependent on each other. The ship’s power requirements determine the volume and mass of the power generation system. The typical ship load determines the size of the powertrain system. Understanding all the technical aspects allows a design to supply the ship with enough power and avoid possible waste.
Environmental Impact Assessment
Potential reductions in GHG emissions and pollutants
The use of ammonia in marine vessel propulsion is seen as the potential panacea for greenhouse gas emissions in marine transportation. If prepared properly, ammonia can potentially reduce carbon dioxide emissions by 99% (Svein, 2023). Studies have shown that using ammonia for propulsion can tremendously mitigate greenhouse gas emissions. Schwarzkopf et al. (2023) showed that using ammonia would reduce carbon dioxide emissions by 47% between 2015 and 2050. The same study projected that ammonia use will reduce nitrous oxide emission by 17% by 2040 and 29% by 2050, using 2015 as the base year. Further, it will reduce nitrogen oxide by 62% by 2040 and 61% by 2050. The study consecutively projected the emission of particulate matter and sulfur oxide to decrease by 73% and 84% by 2040 and 2050,
The Impact On Marine Life
ammonia, especially in low concentrations, is toxic to humans and animals. Ammonia leakages and the production of laughing gas adversely affect air and water quality due to eutrophication and acidification (Prevljak, 2024). Given that marine life depends on water, careless handling of ammonia can adversely affect marine animals. This is especially true for fish which live in less saline and low-temperature zones of marine water.
Economic Considerations
Cost comparisons between green ammonia and other marine fuels
As mentioned earlier, electricity is the greatest contributor to the cost of producing green ammonia. As of 2023, the production cost of a ton of green ammonia was estimated to range between $400 and $1670 (Saygin et al., 2023); the estimates were done with the assumption that the production takes place onsite with dedicated solar or wind energy plants supplying the required energy. The implication is that the energy costs are not part of the estimates. It is important to note that the cost of producing renewable energy depends on the country’s cost of capital. The implication is that countries with favourable capital costs and sustainable wind and solar energy resources can produce green ammonia at $400 per ton. Since the production of green hydrogen contributes about 86% of all green ammonia production costs, a country that offers lower costs of producing green hydrogen is preferred (Saygin et al., 2023). The capital cost of electrolyzers and renewable power technologies contributes 78% of total green ammonia production costs. In countries with favourable capital costs, producing a kilogram of green hydrogen is about $2.
Compared with the production of grey ammonia (produced using natural gas as a feedstock for hydrogen production), the cost of producing green ammonia is 3 to four times higher. The cost of producing grey ammonia is estimated to range between $175 and $810 (Saygin et al., 2023). The costs of producing green ammonia are thus higher than those of producing grey ammonia.
Investment needed for infrastructure development
The production of green ammonia needs a sustainable supply of renewable energy. Since capital costs of electrolyzers and renewable energy contribute 78% of total production costs, production plants should be situated in regions with low capita costs of renewable energy technologies. Another important investment in hydrogen production is electrolyzers, which also contribute to total production costs. The cost of alkaline electrolyzers ranged between $500/Kw to $100/kw in 2023 (Saygin et al., 2023). Renewable energy sources and electrolyzers are, therefore, the primary infrastructural investments.
Safety and Regulatory Issues
Safety concerns specific to ammonia as a marine fuel
Safety concerns of ammonia lie in its characteristics. First, ammonia is very toxic to humans, and personnel should be exposed only to permissible limits (ClassNK, n.d.). In low concentrations, it irritates the eyes, lungs and skin. It is life-threatening in high concentrations. Secondly, although the flammability range is lower than that of hydrogen and other gas fuels, ammonia is still flammable under the right conditions (Buitendijk, 2019). It can react with halogens and interhalogens, causing explosions. Ammonia is corrosive as it reacts with industrial materials such as brass, zinc, and copper.
Existing regulations and guidelines for handling and storage
Due to the safety concerns explained above, there are different regulations and guidelines for handling and storing ammonia to ensure the safety of the personnel. Safety guidelines have been developed concerning the characteristics of ammonia, including toxicity, flammability and corrosiveness (ClassNK, n.d.). On toxicity, the first guideline is the isolation of ammonia, whereby spaces with ammonia should be separated from those without by physical enclosures. The second guideline relates to controlling leakage: the leakage point should be shut after detection, and the leaked ammonia should be removed from the space if unwanted. The third guideline relates to human exposure and states that measures to mitigate harmful effects should be taken for people already exposed to ammonia. The last guideline relates to safe operation and states that ships should be propelled to secure locations for emergency operations like fire extinguishing and evacuation. On flammability, the IGC directs that the provisions of flammable gases in chapter 10 of its guidelines be applied to high concentrations of ammonia (ClassNK, n.d.). On corrosiveness, chapter 17 of the IGC code provides materials that can be used with ammonia to avoid corrosion.
Gaps in current regulations and areas for future policy development
Since ammonia’s use as a marine fuel is still under development, it is hard to evaluate the sufficiency of the existing regulations and guidelines. Rules and policies based on the characteristics of ammonia are sufficient as of now. However, further guidelines need to be directed to the situation of ammonia spillage when the ship is on the move to protect marine life.
Challenges and Barriers to Implementation
Technical challenges in storage, bunkering, and fuel cell technology.
The storage, bunkering and fuel cell technologies of ammonia challenges arise from its corrosive, flammable and toxic nature. Without proper storage and bunkering plans, ammonia leakages can lead to fatalities and injuries. Ammonia can corrode the pipes when transferred using the wrong pipes. Due to these challenges, ammonia-fueled ships need extra design concepts such as associated bunker stations, containment systems, and proper transfer piping. Other necessary aspects include nitrogen-generating pants, vent piping, masts, gas valve units, reliquefaction, and provisions for boil-off gas. Fuel cell technology also faces several challenges. Major challenges of SOFC systems revolve around ammonia safety,open circuit voltage (OCV) stabilization, thermal shocks, nitrous oxides and nitrogen oxide emission, limited power density and sealing issues (Sadashiv et al., 2023). The challenges diminish the efficiency of the cells as a green form of energy and reduce the amount of energy they produce.
Logistical challenges in creating a global supply chain for green ammonia
Logistical challenges associated with green ammonia revolve around the costs, energy conversion rate and environmental credentials. According to Butterworth (2022), the cost of producing a ton of pure green ammonia from renewable energy sources, even in places with plenty of solar and wind, is $900. This cost is high and indicates the underlying costs of renewable energy. The increased expenses discourage private investors from venturing into the industry. Secondly, the energy conversion rate of ammonia is also very low, which leaves questions about production efficiency. Lastly, the production of nitric oxides and nitrous oxides, which pollute the environment, dwarfs its credibility as a green source of energy.
Barriers to entry, such as high initial costs and lack of infrastructure
As mentioned earlier, renewable energy sources are the core of the production of green ammonia. The capital cost of renewable energy and electrolyzers are major contributors to the increased costs of green ammonia. The cost of production of ammonia, therefore, acts as a barrier for countries with high capital costs because the increased capital costs increase the production costs of ammonia. Renewable energy infrastructure is also essential for the production of ammonia. Green can be easily produced in areas with established renewable energy infrastructure because the investor will not have to invest in renewable energy infrastructure. Investors will shy off in areas without such infrastructure because of the increased costs of investing in renewable energy infrastructure.
Future Outlook and Potential Developments
Projections for the growth of green ammonia as a marine fuel
Due to increased emphasis on clean energy and growing knowledge and expertise on ammonia, the use of ammonia as a marine is projected to increase shortly (Ghosh, n.d.). Most projections take 2015 as the base year and 2050 as the target year. The majority of shipping companies considered in different recent studies think that ammonia has great potential to become the leading marine fuel of the future. According to the most recent projections, between 200 and 700 metric tons are expected to be used annually by 2050 (RTI, 2023). About 11 to 39% of this amount will be used as marine fuel.
The potential of new technologies
Different options for ammonia energy-generating cells have been studied. De Vries, for example, studied internal combustion engines (ICE), solid oxide fuel cells (SOFC)), steam and gas turbines, and proton exchange membranes (PEMFC). All have been found feasible for use in marine propulsion. SOFC, however, is the most efficient despite the challenges of cost and large amounts of ammonia needed. ICE is the most applicable for marine propulsion because it is less costly, robust, and has acceptable power density and load response. More technologies are still being researched to efficiently and cost-effectively produce green ammonia.
Role of international cooperation in facilitating a transition to green fuels
Climate change challenge is a global problem affecting all countries and regions. For several reasons, international cooperation is needed when fighting a common enemy. Collaboration in the form of a ‘club model’ allows like-minded countries to come together and develop non-binding agreements on ways to encourage the production and use of green energy (Harro et al., 2024).). This allows countries to independently make institutional arrangements to establish green energy initiatives to encourage their countries’ production and use of green energy. In the form of treaty models, international cooperation allows countries to be bound by legal international agreements to develop and implement green energy initiatives. This would not be the case if a country, especially those that depend on fossil fuels for national income, were to move alone. Moreover, the success of an international agreement in regard to green energy encourages unwilling countries to join in the fight against fossil fuels.
Bibliography
Ash, N. & Scarbrough, T. (2019). Sailing on solar: Could green ammonia decarbonize international shipping? Environmental Defense Fund, London.
Buitendijk, M. (2019). Using Ammonia as a Marine Fuel Requires Specific Safety Measures | SWZ|Maritime. [online] Available at: https://swzmaritime.nl/news/2019/07/25/using-ammonia-as-a-marine-fuel-requires-specific-safety-measures/ [Accessed 11 Mar. 2024].
Butterworth, P. (2022). Green ammonia fuel faces three big challenges. [online] Crugroup.com. Available at: https://sustainability.crugroup.com/article/green-ammonia-fuel-faces-three-big-challenges.
ClassNK (n.d.). Part C ‘Guidelines for the Safety of Ships Using Ammonia as Fuel’ of Guidelines for Ships Using Alternative Fuels Part C ‘Guidelines for the Safety of Ships Using Ammonia as Fuel’ of Guidelines for Ships Using Alternative Fuels. [online] Available at: https://www.classnk.or.jp/hp/pdf/research/rd/2022/05_e07.pdf.
Deng, S. and Mi, Z. (2023). A review on carbon emissions of global shipping. Marine Development, 1(1). doi:https://doi.org/10.1007/s44312-023-00001-2.
Di Micco, S, Cigolotti, V., Mastropasqua, L., Brouwer, J. and Minutillo, M. (2024). Ammonia-powered ships: concept design and feasibility assessment of powertrain systems for a sustainable approach in the maritime industry. Energy Conversion and Management: X, pp.100539–100539. doi:https://doi.org/10.1016/j.ecmx.2024.100539.
Ghosh, A. (n.d.). Ammonia as a Ship’s Fuel | UK P&I Club. [online] www.ukpandi.com. Available at: https://www.ukpandi.com/news-and-resources/articles/2023/ammonia-as-a-ship-s-fuel/#:~:text=Addressing%20Technical%20Challenges%20and%20Ensuring [Accessed 11 Mar. 2024].
Harro van Asselt, Panagiotis Fragkos, Peterson, L. and Kostas Fragkiadakis (2024). The environmental and economic effects of international cooperation on restricting fossil fuel supply. International Environmental Agreements: Politics, Law and Economics. Doi:https://doi.org/10.1007/s10784-023-09623-9.
International Maritime Organization (IMO) (2015). Historic Background. [online] Imo.org. Available at: https://www.imo.org/en/OurWork/Environment/Pages/Historic%20Background%20GHG.aspx#:~:text=In%202000%2C%20the%20First%20IMO [Accessed 9 Mar. 2024].
Mayer, P., Ramirez, A., Pezzella, G., Winter, B., Sarathy, S. M., Gascon, J., & Bardow, A. (2023). Blue and green ammonia production: A techno-economic and life cycle assessment perspective. iScience, 26(8), 107389. https://doi.org/10.1016/j.isci.2023.107389
Olmer, N., Comer, B., Roy, B., Mao, X. and Rutherford, D. (2017). Greenhouse Gas Emissions from Global Shipping, 2013-2015. [online] Available at: https://theicct.org/sites/default/files/publications/Global-shipping-GHG-emissions-2013-2015_ICCT-Report_17102017_vF.pdf.
Osman, O., Sgouridis, S. and Sleptchenko, A. (2020). Scaling the production of renewable ammonia: A techno-economic optimization applied in regions with high insolation. Journal of Cleaner Production, 271, p.121627. doi:https://doi.org/10.1016/j.jclepro.2020.121627
Owen-Burge, C. (2023). Opinion: Shipping can tackle climate change, biodiversity loss, and pollution head-on. [online] Climate Champions. Available at: https://climatechampions.unfccc.int/heres-how-shipping-can-tackle-climate-change-biodiversity-loss-and-pollution-head-on/#:~:text=Shipping%20accounts%20for%20nearly%203 [Accessed 10 Mar. 2024].
Prevljak, N.H. (2024). Switching to ammonia as marine fuel may create more problems than it solves. [online] Offshore Energy. Available at: https://www.offshore-energy.biz/switching-to-ammonia-as-marine-fuel-may-create-more-problems-than-it-solves/ [Accessed 11 Mar. 2024].
RTI (2023). Green Ammonia as a Sustainable Maritime Fuel | RTI. [online] www.rti.org. Available at: https://www.rti.org/impact/green-ammonia-as-sustainable-maritime-fuel#:~:text=Surveyed%20shipping%20companies%20believe%20ammonia [Accessed 11 Mar. 2024].
Sadashiv Dhawale, D., Biswas, S., Kaur, G. and Giddey, S. (2023). Challenges and advancement in direct ammonia solid oxide fuel cells: A Review. Inorganic Chemistry Frontiers. [online] doi https://doi.org/10.1039/D3QI01557B.
Salmon, N., Bañares-Alcántara, R. and Nayak-Luke, R., 2021. Optimization of green ammonia distribution systems for intercontinental energy transport. Iscience, 24(8).
Saygin, D., Blanco, H., Boshell, F., Cordonnier, J., Rouwenhorst, K., Lathwal, P. and Gielen, D. (2023). Ammonia Production from Clean Hydrogen and the Implications for Global Natural Gas Demand. Sustainability, [online] 15(2), p.1623. doi:https://doi.org/10.3390/su15021623.
Schwarzkopf, D., Petrik, R., Hahn, J., Leónidas Ntziachristos, Matthias, V. and Quante, M. (2023). Future Ship Emission Scenarios with a Focus on Ammonia Fuel. Atmosphere, 14(5), pp.879–879. doi:https://doi.org/10.3390/atmos14050879.
Smart, K., (2022). Review of Recent Progress in Green Ammonia Synthesis: Decarbonisation of fertilizer and fuels via green synthesis. Johnson Matthey Technology Review, 66(3), pp.230-244.
Svein Tore Holsether (2023). Why clean ammonia is key to cutting maritime emissions. [online] World Economic Forum. Available at: https://www.weforum.org/agenda/2023/12/clean-ammonia-key-cutting-maritime-emissions/#:~:text=If%20produced%20correctly%2C%20green%20ammonia [Accessed 11 Mar. 2024].
Wang, Y. and Wright, L.A. (2021). A Comparative Review of Alternative Fuels for the Maritime Sector: Economic, Technology, and Policy Challenges for Clean Energy Implementation. World, 2(4), pp.456–481. doi:https://doi.org/10.3390/world2040029.
Xu, J., Testa, D. and Mukherjee, P.K. (2015). The Use of LNG as a Marine Fuel: The International Regulatory Framework. Ocean Development & International Law, [online] 46(3), pp.225–240. doi https://doi.org/10.1080/00908320.2015.1054744.
Yara International (2023). The world’s first clean ammonia-powered container ship | Yara International. [online] Yara None. Available at: https://www.yara.com/corporate-releases/the-worlds-first-clean-ammonia-powered-container-ship/.
write