Maritime transport accounts for 80% of the total volume of global trade (IEA 2023a). International Shipping which drives the global trade, accounts for approximately 2% of global energy-related carbon dioxide (CO₂) emissions (IEA 2023b). Moreover, to achieve the net-zero greenhouse gas (GHG) emissions target for international shipping by 2050, as established by the International Maritime Organization, the implementation of multiple decarbonization measures is necessary (IMO 2024). Hydrogen-based fuel supply chains shall significantly influence the course of this transition. Other relevant aspects in the transition are fleet readiness, fuel availabilty and adoption of IMO guidelines for alternative maritime fuels. According to Clarkson’s Green Technology Tracker (Gordon 2024), the proportion of alternative-fuel capable vessels has been folowing an increasing trend, with 41% of the tonnage ordered in the first quarter of 2024 being alternative fuel capable. Orders were placed for a total of 310 alternative dual-fuel ships, including 109 LNG dual-fuel ships, 49 for methanol, 42 for LPG, 15 for ammonia, and four for hydrogen. In the scenario of deployment of hydrogen and its derivatives, ammonia and methanol are the two proposed alternative maritime fuels based on environmental and economic life cycle considerations. Hydrogen, on the other hand, could be a promising fuel for small, medium-size, and short-range ships (Kanchiralla et al., 2024; Raucci et al., 2023).

Germany has set an ambitious target of up to 10 GW electrolysis capacity by 2030; however, domestic production alone will not be sufficient to meet its hydrogen demand, meaning substantial amounts will need to be imported (Dertinger et al., 2022). Following this, the total future demand of hydrogen derivatives, including ammonia and methanol, in Germany in 2030 and 2050, will also exhibit import requirements. Many studies have addressed the techno-economic aspects of global supply chains of these fuels. Song et al. (2022) presented comparative study of energy efficiency of the maritime supply chains for hydrogen, ammonia, methanol, and natural gas with energy efficiency of 62.31% for ammonia, 65.67% for methanol and 47.78% for hydrogen. Ammonia and methanol showed potential to replace LNG due to lower energy losses and efficient long-distance transport. Hydrogen requires efficient BOG handling systems to increase competitiveness. They concluded that these energy carriers could transport renewable energy across seas, but further analyses are needed. Although, the efficiency presented in this paper was for a majorly natural gas-based production pathway without CCS.

Noh et al. (2023) analyzed the environmental impact through LCA for compressed gaseous hydrogen, liquid hydrogen, LOHC and Ammonia, specifically focusing on ship-based transportation. Notably, all the above-mentioned derivatives are converted back to compressed gaseous hydrogen, forming the boundary condition of the methodology. They reported energy efficiency of supply chain for a shipping distance of 100 km ranges to be between 41%–57%. However, as the transport distance increases to 10,000 km efficiency decreases to 18%–22%.

Previous investigations of the energy efficiency of hydrogen and derivatives transport, reported value ranging from 42%–65% (including green, blue, grey pathways of hydrogen production) (Al-Breiki and Bicer 2020b; Ishimoto et al., 2020; Noh et al., 2023; Song et al., 2022; Staudt et al., 2024). However, there remains a gap in the literature concerning the maritime transport and utilization of these fuels, particularly in understanding the direct use of ammonia and methanol as maritime fuels, as well as the associated bunkering operations and infrastructure. This study leverages the existing pipeline infrastructure between Norway and Germany to demonstrate a near-future 2030 scenario, and also a 2050 scenario, where the construction of new pipeline may be considered. Staudt et al. (2024) lays focus on import, contrasting with other studies that primary focus on transport without considering the specific demand of importing countries or supply ambitions of exporting countries. The study covers synthetic ammonia and methanol however, their analysis is limited to the supply chain processes after hydrogen production. Sens et al. (2024), Rahmat et al. (2023) focused on use of ammonia or methanol as transport vectors of hydrogen and their land based utilization. This paper demonstrates a potential for directly utilizing ammonia and methanol as alternative maritime fuel, thereby bridging the aforementioned gaps. It also accounts for bunkering operations for the specific port of Wilhelmshaven.

When considering economic feasibility, studies have assessed the cost of hydrogen transportation and utilization in sectors such as heavy duty transport, aviation and steel manufacturing (Ishimoto et al., 2020; Ratnakar et al., 2021; Sens et al., 2024). It has been found that supply chains of compressed gaseous hydrogen exhibit the lowest overall supply costs, particularly when transported via pipelines directly to filling stations. Liquid hydrogen supply chains are less cost-effective due to substantial capital expenditures and energy demands for liquefaction, although LH₂ storage could benefit from well-stablished LNG technologies. Meanwhile, liquid organic hydrogen carriers have the highest supply costs due to the high energy demands for dehydrogenation and their limited hydrogen carrying capacity (Sens et al., 2024). However, in the context of maritime transport, dehydrogenation is not utmost necessary, as fuels such as ammonia and methanol can be utilized directly. Schorn et al. (2021), estimate levelized costs for importing methanol from Saudi Arabia to Germany or importing hydrogen to Germany and producing methanol locally. It was reported that for both options imports costs were 25–30 €/GJ in 2030. However, they do not look into the energy efficiency of the processes involved in the supply chain, nor consider different hydrogen production pathways.

Green hydrogen production costs are expected to decrease from a reference 5.3 € per kg in 2020 to 4.4 € per kg by 2030 and further to 2.7 € per kg by 2050 (Frieden and Leker 2024). Despite anticipated cost reductions, Europe is still projected to incur the highest hydrogen production costs. This underscores the necessity of exploring import options, although in most instances, the development of new infrastructure will be required. Dinh et al. (2024) have demonstrated that for newly built infrastructure of hydrogen and ammonia transport, pipelines are most economical for short distances up to 500 km, whereas LH₂ tankers are more economical for distances exceeding 2,000 km and with a generation capacity of 2,500 MW. However, a technical assessment of using existing pipeline infrastructure, as well as demand-supply based shipping routes with a clear focus on maritime fuels is missing from existing literature. Consequently, this paper seeks to address this gap from a 2030 and 2050 time horizon perspective.

Chen et al. (2025) analyzed the levelized cost approach to evaluate the H₂ shipping costs on eight potential international routes. Analysis considered transport of LH₂, methanol, liquid ammonia, DBT and MCH and concluded that methanol has the lowest hydrogen shipping cost, followed by ammonia, LH₂, DBT, and MCH. Moreover, the results also show H₂ shipping costs on the Australia-East/Southeast Asia and West Africa-Europe routes are comparatively competitive than those on the Australia-Europe, South America-Europe, Middle East-East Asia, and Middle East-Europe routes. Furthermore, it is reported by Schuler et al. (2024) that the potential shipping costs of ammonia and Fischer-Tropsch fuels are to be the least expensive option when compared to liquid hydrogen. While shipping costs constitute a rather small part of the overall energy supply cost in the importing country, studies are needed to identify the most efficient energy carrier derived from renewables. Consequently, a scenario-based approach is essential to recommend import from a particular geographical region.

Therefore, different import scenarios, with three potential production locations, namely Norway, Namibia and Algeria, are studied in this paper. In light of this background, the objective of the work presented here is to investigate the supply chain efficiency of maritime fuels i.e. gaseous hydrogen, ammonia and methanol, considering the production, storage, transport and bunkering stages of the fuel supply chain. Ammonia and methanol constitute established globally traded chemicals, available for transport on a large scale via shipping fleets and harbor infrastructure. Compressed gaseous hydrogen, on the other hand, can be transported via pipelines, which are typically constructed for large capacities. Existing natural gas pipelines could also be repurposed after implementing rigorous inspection protocols to mitigate safety and material embrittlement risks (DENA & Gassco AS 2023; Dertinger et al., 2022).

In this analysis, hydrogen is produced either via electrolysis powered with renewable energy, referred to as green hydrogen, or via Steaming Methane Reforming (SMR) coupled with Carbon Capture and Storage (CCS), referred to as blue hydrogen (Ustolin et al., 2022). This hydrogen is subsequently transported in gaseous form via pipelines from Norway, whereas from Namibia and Algeria, hydrogen derivatives, namely ammonia and methanol, are produced in these countries and then transported to Germany via ship. Both ammonia and methanol can be utilized as maritime fuels without reconversion to hydrogen. Simultaneously, the extensive pipeline infrastructure currently operational in Norway and Germany has been proposed as a potential means for transporting compressed gaseous H₂.

This chapter describes the expected demand for 2030 and 2050 of hydrogen and hydrogen-based fuels-ammonia and methanol-in Germany, and presents the three possible supply options considered, namely from Norway, Namibia and Algeria.

This research examines a system designed to supply alternative maritime fuels, specifically methanol and ammonia, to Germany, evaluating their supply chain efficiency. The analysis establishes the system’s boundary conditions and defines the scope of the selected import pathway. While various import pathway combinations are currently under consideration and may be subject to future feasibility analyses, this investigation focuses on three probable supply chain options. These options are based on Germany’s projected demand, the exporting country’s hydrogen strategies, renewable energy generation capabilities, and transportation modes, including pipeline and ship. The analysis incorporates blue and green hydrogen based on the country of export. In the case of Norway and Algeria, a higher proportion of blue hydrogen in 2030 is considered, as there is a natural gas reliance in these economies. The ratios of blue to green hydrogen are derived from existing literature (Alvik et al., 2023; BMWK 2023) and can be found in Table 2. Assuming that geopolitical conditions are prone to change, which is further described in Section 5.5, a sensitivity analysis is conducted in the results section. The ammonia and methanol supply routes examined are as below:

Import of hydrogen via pipeline from Norway to produce ammonia and methanol in Germany

Table 3 describes the boundary conditions relevant for transport and the country specific conditions. The hydrogen imported from Norway via pipeline could fulfill the total demand for gaseous hydrogen in Germany, which is estimated to be 1.5–3.3 Mt per year in 2030 and 10.5–17.4 Mt per year in 2050. It is then assumed that one-third of this demand will be met by imports from Norway (Alvik et al., 2023). The pipeline specifications are enumerated later in Table 7. The demand for ammonia presented in.

Table 1 is utilized to calculate the hydrogen redirected through the distribution pipelines from Schillig (point of arrival) to Wilhelmshaven (final destination). Considering the projected growth in ammonia and methanol demand within the maritime industry, this hydrogen is subsequently converted to ammonia in Wilhelmshaven (EE Energy Engineers & TÜV NORD EnSysGmbH, 2023).

As for Namibia and Algeria, both countries have above-average solar and onshore wind resources. This can be observed, for example, when comparing the capacity factors that can be obtained in both countries with world averages. For instance, the mean capacity factor expected to be obtained in solar PV plants in Namibia is 32% (Ministry of Mines and Energy Namibia 2022), while in Algeria it is 27% (Wolf et al., 2024). For reference, the world average for new solar PV projects in 2018, according to the IEA, was 18% (Cozzi et al., 2019). Similarly, for onshore wind plants, the mean capacity factor expected in Namibia is 40% (Ministry of Mines and Energy Namibia 2022), while in Algeria it is 44% (Wolf et al., 2024). In contrast, the worldwide average for new projects in 2018 was 30% (Cozzi et al., 2019). Figure 1 graphically shows the lower bound, mean, and higher bound values of these capacity factors.

For the case of imports from Algeria, hydrogen transport to Germany via pipeline is another alternative that could be contemplated, with it being mentioned in the country´s national hydrogen strategy (Ministère de L'Energie et des Mines - Algérie, 2023). The Global Gas Report 2020 (BloombergNEF 2020) outlines a potentially cost-competitive import route via the Transmed pipeline, going from Algeria through the Mediterranean sea to Italy and reaching south Germany after a transport distance of 2,800 km. However, the additional transport requirement from south Germany to Wilhelmshaven would result in a low economic appeal of the import route. In this sense, IRENA suggests that pipeline transport is the most cost-efficient option for distances of up to 3,000 km, which would be exceeded in this case (IRENA 2022). This takeaway is also supported by analysis performed for the TransHyDE Project (Ausfelder et al., 2024), where it was stated that hydrogen imports from non-EU countries are less competitive compared to large-scale domestic production within Europe, especially when those imports are intended to be carried out via pipeline. Moreover, hydrogen exports in the form of methanol and ammonia via shipping are also outlined in Algeria´s national hydrogen strategy (Ministère de L'Energie et des Mines - Algérie, 2023). Therefore, the approach of considering their direct import shows potential, since these fuels could be deployed in alternative maritime transport.

In this analysis, a ship transport of hydrogen-derived fuels for maritime applications is considered, with the final destination of interest being the port of Wilhelmshaven. In 2019, a total of 29.29 million tons of cargo were handled at the port of Wilhelmshaven. This consisted of oil and its by-products carriers, chemical carriers, steel and by-products carriers, LPG, wood, and car carriers. Therefore, this port has been selected due to international carrier’s bunkering requirements (Niedersachsen Ports 2020).

The storage of methanol and ammonia is assumed both at the import and export terminals. Furthermore, for both of these fuels, a 30 days storage capacity was assumed at the import terminal. Additionally, the maritime demand of ammonia in Germany is used to estimate the hydrogen needed via the inland distribution pipeline. Losses due to boil-off for ammonia, which is reliquefied, are considered for energy consumption calculations during its transport, loading and unloading and bunkering. Both ammonia and methanol are assumed to be transported in liquid state.

In both 2030 and 2050 scenarios, the percentage distribution for import is based on each importing country’s availability of fuel data. For 2050, the demand has been split equally between countries in order to avoid biases in calculations. However, for 2030 this could not be considered because of the current strategies of the respective countries. The aforementioned assumptions were also formulated under the premise that the German government wants to guarantee a diversified supply of the country´s hydrogen and hydrogen derivatives imports, as outlined in the national import strategy adopted in July 2024 (BMWK, 2024). Additionally, in the case of the African countries, a comparison of their hydrogen production and export goals for 2030 was considered in order to define the shares of imports for the case of methanol (Ministère de L'Energie et des Mines - Algérie, 2023; Ministry of Mines and Energy Namibia 2022). This led to the observation that Namibia has a hydrogen production goal of 1 Mt of H₂ per year for 2030, while Algeria has a goal of 0.3 Mt of H₂ per year for the same time horizon. Therefore, it was assumed that, for 2030, 53.3% of Germany’s methanol demand would be supplied by Namibia, while 13.3% would be supplied by Algeria, and the remaining 33.3% by Norway, as shown in Table 4.

In case of ammonia, the german maritime demand for both 2030 and 2050 is assumed to be equally distributed between 1) hydrogen imports from Norway for the domestic production of ammonia, and 2) direct imports of ammonia from Algeria and Namibia.

A scenario-based approach is employed as the research methodology in this work. It entails the provision of optimized suggestions in the form of an output, relying on input variables that could be a function of time frame, demand and supply ambitions (for example, low and high demand values), and capacity to produce, transport, and store the traded item. This approach yields suggestions of a suitable supply chain route for the import of fuel considering low and high demand brackets, supply possibilities in the view of production capacities of hydrogen (blue, green), transport via pipeline and ship, storage at port, and bunkering vessels for the years 2030 and 2050 as time frames. The initial step involves identifying the specific fuel routes based on the exporting country’s hydrogen strategy. Following this, the input and output parameters of the selected fuel transport routes are modeled, linking them with the end usage specifications (bunkering) to evaluate the efficiency of the overall supply chain. Furthermore, the uncertainties of the future, which might lead to a different share of blue and green hydrogen supply, are covered by performing a sensitivity analysis.

The following sub-chapter provides a detailed description of the compressed hydrogen, ammonia and methanol supply chains considered in this paper, along with their energy requirements and system boundaries.

The results are presented as per the methodology, considering low and high demand scenarios for both ammonia and methanol. These scenarios have been derived from.

Tables 1, 2 for the years 2030 and 2050. The summation of energy use of the different components of the supply chain constitutes the total energy input. The supply chain efficiency is defined as the ratio of the energy content of delivered fuel (LHV) in the form of ammonia and methanol to the total energy consumption covering all the considered stages of supply chain: production, conditioning, transport, storage and bunkering. It is important to note that because of the losses associated with electrolysis and SMR with carbon capture and storage, the energy consumption for the hydrogen production stage has a significantly high share in all three import options. In particular, it accounts from 75% to 82% of the total energy consumption of the supply chain.

The power-to-fuel efficiencies obtained in this study for 2030 range between 44.51% in Namibia and 44.88% in Algeria, while in 2050 they increase to 47.56% for both countries, primarily due to the anticipated improvement of electrolyzer efficiency. This is lower compared to the 52.4% and 54.7% figures found by (Rahmat et al., 2023) when considering a VDB kinetic model and a GRF model respectively. On the other hand, the energy consumption calculated for the Haber- Bosch process and Air separation unit (ASU) is 2.05 MJ/kg NH₃. This value is slightly lower than the one reported in Staudt et al. (2024) (2.5 MJ/kg NH₃) owing to the differences in process conditions. Namely, that hydrogen is delivered in a compressed state. This difference in energy consumption is taken in to account in the conditioning stage of the supply chain.

This analysis aims to evaluate import routes based on technical efficiency for establishing future trade relations. Additionally, it shall provide insights for shipping companies considering the trade routes presented in this research. Based on the results, it is concluded that the supply chain relying on pipeline-based transport of hydrogen demonstrated a lower energy consumption per kilogram of fuel (ammonia or methanol) compared to the ship-based transport. The overall supply chain efficiency of producing ammonia and methanol from Norway-imported hydrogen via pipelines is higher when compared with transport via ship from both Namibia and Algeria, indicating the potential attractiveness of inland production. Consequently, continuous, large-scale transport of hydrogen from Norway to Germany could provide new opportunities for the domestic production of future maritime fuels.

As observed from the results, the technical efficiency of import varies from 42.17% to 50.02% between the analyzed countries. Hence, it is concluded that it is not a constraining factor to import the considered fuels via pipeline and ship. Although an economic analysis could provide further insights towards the implementation of the presented supply chain options.

It is noteworthy that in 2030, the disparity in supply chain efficiency is attributed to the hydrogen production methods, specifically between the green and blue pathways. A higher proportion of blue hydrogen originates from Norway and Algeria compared to Namibia. Consequently, this results in a reduced supply chain efficiency for maritime fuels produced in Namibia. For 2030, it is advisable to consider import options from Norway and Algeria, as their average supply chain efficiencies are highly comparable, where the average ammonia supply chain efficiency of Norway is 47.77% and Algeria 46.89%. And for methanol, the average supply chain efficiency of Norway is 44.40% and Algeria 43.90%.

By 2050, especially in high demand scenarios, import of ammonia and methanol from Algeria is competitive to production of those fuels in Germany. However, the extended maritime transportation route from Namibia results in a comparatively low overall supply chain efficiency. Import recommendations derived from this analysis indicate that green ammonia and methanol demonstrated comparable energy efficiency for transport from Namibia in 2050.

Furthermore, this analysis paves way for assessment of international fuel trade strategies by highlighting that the current seaports can be converted to future renewable fuel hubs thereby inland waterways could also benefit. Hence, a broader sectoral relevance can be envisaged upon economic assessment of such a pathway. Additionally, the intermittent nature of solar and wind energy demands large-scale storage, while transportation infrastructure for these types of fuels is also indispensable to fulfill worldwide energy needs. The demand and transport capacities of these fuels, along with energy security, also play a role in determining the need for storage capacities. Therefore, storage infrastructure is decisive for trading these fuels between demand and supply locations. Through this paper, we addressed the port storage requirements and its impact on bunkering operations.

Joint declaration of interest and project development among countries for alternative maritime fuels can also distribute the financial risks and capability of governments to intervene in market mechanisms to ensure sustainable, economically stable and equitable supply chains.

In the future, it is expected that ammonia and methanol would gain share as global alternative maritime fuels and/or alternative energy carriers, to transport renewable energy by sea from countries with high renewable energy generation potential to countries with high energy demand. Therefore, a comprehensive economic analysis is needed to extensively analyze the viability of the maritime supply chain for these energy carriers, which will be further explored in future studies.