1. Introduction
With increasingly stringent international regulations aimed at reducing greenhouse gas emissions from the shipping sector, the transition to environmentally friendly fuels has accelerated. In particular, at the 80th session of the Marine Environment Protection Committee (MEPC) of the International Maritime Organization (IMO), the 2023 IMO Strategy on Reduction of GHG Emissions from Ships was adopted, establishing the medium- to long-term direction for decarbonizing international shipping and setting the goal of achieving net-zero emissions from international shipping by 2050 (IMO, 2023; Fig. 1). Subsequently, at its 83rd session, the MEPC approved the IMO Net-Zero Framework, a key mid-term measure for implementing the strategy (IMO, 2025a). Although a subsequent extraordinary session (MEPC ES.2) postponed the final adoption vote by one year, delaying its implementation (IMO, 2025b), regional policies, such as the European Union’s fuel regulations and emissions trading system, continue to become more stringent (European Commission, 2026). These policy developments are compelling the shipping industry to transition toward low- and zero-carbon fuels and accelerating a paradigm shift away from conventional fossil-fuel-based transportation systems.
Amid this decarbonization trend, green shipping corridors have attracted attention as a practical strategy for reducing greenhouse gas emissions from the shipping sector (Global Maritime Forum, n.d.; Ismail et al., 2024). A green shipping corridor is a specific route on which low- or zero-carbon shipping is enabled through the integrated development of environmentally friendly fuel supply systems, vessel operation technologies, and port infrastructure (Global Maritime Forum, n.d.). To establish such corridors, various alternative fuels, including liquefied natural gas (LNG), ammonia, hydrogen, and methanol, are being considered.
Previous studies have primarily analyzed the technical characteristics of environmentally friendly fuels, their production and supply systems, and related policy trends (Xing et al., 2021; Jeong et al., 2022). However, many have focused on individual technologies or policies, and quantitative route-level assessments that account for operating conditions remain relatively limited. In particular, although an increasing number of studies have jointly considered the economic and environmental performance of environmentally friendly fuels, few have quantitatively evaluated the trade-offs associated with fuel switching while accounting for route-specific operating conditions and international regulations (Bouman et al., 2017; Xing et al., 2021). Establishing green shipping corridors requires not only the application of new technologies but also economic feasibility and regulatory compliance; therefore, an integrated analysis is necessary to assess their practical applicability.
International cooperation has become increasingly important for establishing green shipping corridors, and discussions have continued regarding the development of a green shipping corridor between South Korea and the United States. In particular, since the 27th Conference of the Parties to the United Nations Framework Convention on Climate Change (COP27), specific measures for establishing a green shipping corridor centered on the Port of Busan and ports on the U.S. West Coast have been under discussion (Ministry of Oceans and Fisheries, 2022). Accordingly, the Korea–U.S. route provides a relevant case for assessing the feasibility of establishing a green shipping corridor using environmentally friendly fuels. Therefore, this study aims to conduct a preliminary feasibility assessment of alternative fuel use for a green shipping corridor on the Korea–U.S. route. The analysis uses the methanol-fueled container ship Ane Maersk as the case vessel and compares the environmental and economic performance of four fuel scenarios: heavy fuel oil (HFO), LNG, methanol, and biodiesel.
2. Current Status of Alternative Marine Fuels
2.1 Current Status of LNG as a Marine Fuel
LNG is produced by liquefying natural gas at approximately −162 °C and has a higher hydrogen-to-carbon ratio than conventional HFO. The lower heating value (LHV) of LNG is approximately 50 MJ/kg, which is higher than that of HFO. However, because LNG must be stored under cryogenic conditions, fuel tanks require additional insulation and auxiliary systems (Xing et al., 2021). In terms of propulsion systems, LNG dual-fuel engine technologies have already reached the commercialization stage, and both low- and high-pressure fuel supply systems are currently in use. Accordingly, LNG propulsion has been adopted for various vessel types, including container ships, bulk carriers, and tankers, making LNG one of the most widely commercialized alternative marine fuels (Bouman et al., 2017; Xing et al., 2021).
From a safety perspective, LNG requires appropriate measures to manage low-temperature embrittlement and leakage during storage and fuel supply. In addition, vaporized natural gas is flammable, necessitating safety measures to mitigate fire and explosion risks. For these reasons, the IMO has established safety requirements for the storage, supply, and use of low-flashpoint fuels, including LNG, through the International Code of Safety for Ships Using Gases or Other Low-flashpoint Fuels (IGF Code) (IMO, 2016). From an environmental perspective, LNG produces almost no sulfur oxides (SOx) or particulate matter (PM) during combustion and is known to generate lower nitrogen oxide (NOx) emissions compared with conventional fossil fuels. In addition, its mass-based carbon dioxide emission factor is approximately 2.750 gCO2/gfuel, indicating that LNG combustion generates lower direct CO2 emissions during vessel operation (IMO, 2020; Pavlenko et al., 2020). However, methane slip may occur depending on the engine type and operating conditions, contributing to additional greenhouse gas emissions.
2.2 Current Status of Methanol as a Marine Fuel
Methanol has a relatively low energy density, with an LHV of approximately 19.9 MJ/kg, about half that of HFO. Therefore, achieving the same cruising range requires greater fuel storage capacity, potentially imposing design constraints such as reduced cargo capacity or larger fuel tanks (Masum et al., 2025). As a liquid fuel, methanol can be stored and handled at ambient temperature and pressure, providing an operational advantage over fuels that require cryogenic or high-pressure storage (Rao et al., 2025). In terms of propulsion systems, methanol dual-fuel engine technologies have reached the commercialization stage, and existing diesel-engine-based systems can be retrofitted for methanol operation. However, because methanol has a low cetane number, pilot fuel is commonly used to ensure stable ignition (Yao et al., 2008). From a safety perspective, methanol is both toxic and flammable, posing risks to human health and the environment in the event of leakage. In particular, its nearly invisible flame can make fires difficult to detect, necessitating dedicated safety standards and handling procedures (Korean Register, 2023).
From an environmental perspective, methanol is a carbon-containing fuel and therefore emits carbon dioxide during combustion. Nevertheless, it produces almost no SOx and can reduce NOx and PM emissions (Xing et al., 2021; Zincir & Deniz, 2021). Its mass-based CO2 emission factor is approximately 1.375 gCO2/gfuel, approximately half that of conventional HFO at 3.114 gCO2/gfuel (IMO, 2020). Methanol therefore has a substantially lower mass-based CO2 emission factor than HFO, although its lower energy density increases the amount of fuel required to provide the same energy output. Overall, methanol is considered suitable for near-term fuel switching because of its ease of storage and handling, compatibility with existing engine technologies, and relatively low mass-based CO2 emission factor. However, its low energy density and associated safety concerns require additional consideration in vessel operation and design.
2.3 Current Status of Biodiesel as a Marine Fuel
Biodiesel is a bio-based fuel produced from feedstocks such as vegetable oils, waste cooking oil, and animal fats and is recognized as a representative drop-in fuel for the shipping sector. Because biodiesel has physical properties similar to those of conventional diesel fuel, it can be used with existing fuel supply systems and storage facilities without requiring major engine modifications (Cho, 2015). In terms of propulsion systems, biodiesel can be used directly in conventional diesel engines or as a blended fuel. Therefore, unlike LNG and methanol, it generally does not require the installation of new fuel storage facilities or propulsion systems. Owing to these characteristics, shipping companies are increasingly considering and adopting biodiesel as a means of reducing lifecycle greenhouse gas emissions from existing vessels (Kil, 2023).
From an environmental perspective, biodiesel emits carbon dioxide during combustion, and its tank-to-wake (TtW) emission characteristics are similar to those of conventional fossil fuels (Stathatou et al., 2022). However, because biodiesel is produced from biomass feedstocks, its overall environmental performance may vary depending on the feedstock and production pathway (Hsieh & Felby, 2017). Overall, biodiesel is an alternative fuel that can be readily applied to existing vessels and is therefore advantageous for near-term fuel switching. However, the limited availability of sustainable biomass and high fuel costs remain major challenges to its wider commercialization. In addition, because its overall environmental performance can vary considerably depending on the production pathway, further assessment is required before widespread application (Xing et al., 2021; Hsieh & Felby, 2017).
3. Methodology for Route-Based Assessment of CO2 Emissions and Economic Performance of Marine Fuels
This section presents the methodology used to quantitatively assess the environmental and economic impacts of marine fuel switching. The analysis considered a Korea–U.S. shipping route, with fuel-specific scenarios defined under identical route and operating conditions to enable consistent comparisons among the fuels. Environmental performance was evaluated using TtW CO2 emissions, a TtW CO2-based estimate of greenhouse gas fuel intensity (GFI) under the IMO Net-Zero Framework, and the carbon intensity indicator (CII). Economic performance was assessed on the basis of fuel costs and estimated compliance costs under the IMO Net-Zero Framework. These environmental and economic indicators formed an integrated analytical framework for comparing the selected fuels.
3.1 Analysis of the Selected Route
To analyze the environmental and economic impacts of marine fuel switching, this study selected the Busan–Los Angeles route, a major trans-Pacific container shipping route connecting Asia and North America. The route represents a long-distance shipping corridor characterized by large cargo volumes and a long sailing distance, resulting in substantial fuel consumption and greenhouse gas emissions. These characteristics make the route suitable for analyzing differences in environmental and economic performance among fuel scenarios.
The great-circle distance from Busan, South Korea, to Los Angeles, United States, is approximately 5,000 nautical miles (NM). To better reflect the actual sailing route, the analysis used a route distance of 5,287 NM obtained using a maritime route calculation tool (SeaRoutes, n.d.; Fig. 2). This distance served as the basis for estimating fuel consumption and emissions and quantitatively comparing the environmental and economic effects of fuel switching.
3.2 Case Vessel and Scenario Definition
To compare the selected fuels, this study used Ane Maersk, an existing methanol-fueled container ship, as the case vessel. Maersk introduced Laura Maersk, the world’s first methanol-fueled container ship, in 2023. Laura Maersk is a relatively small feeder container ship that primarily operates on short-haul routes in Northern Europe (Maersk, 2023). In contrast, Ane Maersk is a large methanol dual-fuel container ship delivered in 2024 and designed for long-distance operations. The vessel is 350 m long and 53.5 m wide, has a service speed of 21 kn, and has a capacity of 16,592 TEU (Fig. 3). Ane Maersk is equipped with a MAN B&W 8G95ME-C10-LGIM low-speed, two-stroke dual-fuel main engine manufactured by MAN Energy Solutions. The engine can use methanol as its primary fuel while also operating on conventional marine fuels. In addition, the vessel has a methanol fuel storage capacity of 16,000 m3 and a reported maximum cruising range of 23,000 NM on methanol, making it suitable for long-distance routes (Maersk, 2024).
Based on the engine specifications of the case vessel, analytical scenarios were developed to compare the effects of different fuel types under the same vessel geometry and operating conditions. Across the scenarios, the vessel geometry and operating conditions remained unchanged, while the main engine and fuel type varied. The fuel scenarios included major alternative marine fuels identified by DNV (2025), together with fuels currently used in the shipping sector. The fuel-specific scenarios are summarized in Table 1.
HFO was selected as the reference fuel representing conventional marine operations because it remains a primary fuel used in international shipping. LNG was included because it has reached the commercialization stage and has been widely adopted among alternative marine fuels. Methanol was also selected because its use has recently expanded in orders for environmentally friendly vessels and in the development of green shipping corridors. In addition, biodiesel was included to assess its applicability during the fuel transition because it is widely recognized as a representative drop-in fuel that can be used in conventional diesel engines without major modifications. Considering the target application year of 2028, hydrogen was excluded because further technological development and commercial-scale validation are still required for propulsion systems, fuel storage and supply facilities, and bunkering infrastructure for large commercial vessels.
The engine scenarios were defined to account for differences in combustion characteristics and fuel supply systems among the selected fuels. Applying the same engine to all fuel types would not be technically appropriate. Accordingly, a suitable engine from the MAN B&W 8G95ME series was assigned to each fuel scenario (MAN Energy Solutions, 2024). In addition, the analysis excluded methane slip and fuel leakage emissions because sufficient publicly available data were unavailable. The analysis used the 5,287-nautical-mile route from Busan to Los Angeles defined in Section 3.1 and set the vessel speed to its service speed of 21 kn. Because actual engine load data under vessel operating conditions were unavailable from public sources, the analysis assumed an engine load of 85% of the maximum continuous rating (MCR). This assumption reflects the general operation of marine engines under partial-load conditions at service speed. Fuel consumption was then estimated for all scenarios using the same route and service-speed conditions and an engine load of 85% of the MCR.
3.3 Indicators for CO2 Emissions and Economic Assessment
3.3.1 Method for Estimating CO2 Emissions
This study selected CO2 emissions as the primary indicator for evaluating the environmental performance of each fuel. CO2 is the principal greenhouse gas emitted by the shipping sector and accounts for the majority of its greenhouse gas emissions. International policies and regulations therefore treat CO2 reduction as a key regulatory objective. In particular, because reducing CO2 emissions represents a major objective of the IMO greenhouse gas reduction strategy, this study used CO2 emissions as the representative indicator for assessing the environmental impacts of fuel switching (IMO, 2023).
Greenhouse gas emissions from the shipping sector are generally assessed on either a well-to-wake (WtW) or TtW basis. The WtW approach includes both upstream emissions generated during fuel production, transportation, and storage and direct emissions generated during onboard fuel use. By contrast, the TtW approach considers emissions generated during onboard fuel use. In this study, the TtW assessment was restricted to direct CO2 emissions from fuel combustion to apply a consistent assessment boundary across the fuel scenarios.
CO2 emissions from ships can be determined using methods ranging from direct measurement to relatively simple emission-factor-based estimation. Considering practical applicability and data availability, this study adopted an estimation method based on fuel consumption and emission factors. The analysis used the fuel-specific CO2 emission factors provided by the IMO (Table 2). These emission factors have been reported to provide estimates comparable to CO2 emissions measured during actual vessel operations (Jang et al., 2025). Total CO2 emissions were calculated by multiplying the amount of each fuel consumed by its corresponding emission factor. Because no separate biodiesel emission factor was available, this study assumed the same emission factor as that of marine diesel oil (MDO), on the basis of previous findings that their TtW emission characteristics are similar (Stathatou et al., 2022). Fuel consumption for each fuel type was estimated using the engine-load-dependent fuel consumption characteristics provided by the engine manufacturer (Fig. 4). For dual-fuel engines, MDO was assumed to be used as the pilot fuel to ensure stable ignition and combustion.
3.3.2 Method for CII Calculation
The CII was introduced by the IMO to assess the operational carbon intensity of ships and represents the amount of CO2 emitted per unit of transport work. The CII serves as a key indicator of the operational carbon performance of ships. The IMO assigns ratings from A to E by comparing each vessel’s attained CII with its required CII.
This study calculated the CII to further compare the environmental performance of the fuel scenarios. The analysis aimed to compare the relative performance of different fuels along the same route rather than determine an official IMO CII rating on the basis of the annual operational data of a specific vessel. Accordingly, the study calculated a voyage-based CII using the IMO CII formulation, as expressed in Eq. (1):
Here, MCO2 is the amount of CO2 emitted during the voyage (g), capacity is the vessel’s carrying capacity expressed as deadweight tonnage (DWT), and Distance is the sailing distance (NM).
3.3.3 Method for Estimating Fuel and Emission Compliance Costs
This study divided the assessed operating costs into fuel costs and costs associated with compliance with emission regulations. The analysis estimated emission compliance costs by applying the GFI-related economic measures under the IMO Net-Zero Framework according to the calculated fuel-specific emission intensities.
Fuel costs were estimated on the basis of fuel consumption over the selected route and the unit price of each fuel. Fuel consumption was calculated using the route distance defined above (Fig. 2) and the engine-load-dependent fuel consumption characteristics provided by the engine manufacturer (Fig. 4). Fuel prices were obtained from projections presented in a DNV analysis report based on documents submitted to the IMO (DNV, 2024). Regression analysis was performed using the fuel price data for 2023, 2030, 2040, and 2050 provided by DNV, and the resulting regression models were used to estimate fuel prices for 2026. The estimated prices were 11.415 USD/GJ for HFO, 13.506 USD/GJ for LNG, 14.362 USD/GJ for fossil methanol, 11.264 USD/GJ for MDO, and 29.339 USD/GJ for bio-MGO. Total fuel costs were calculated using Eqs. (2)–(4), and the LHVs of the primary and pilot fuels used in each case were obtained from the literature (Table 3).
Here, Fuelmass is the total fuel consumption (kg), SFOC is the specific fuel oil consumption (g/kWh), P is the engine power output (kW), t is the sailing time (h), Total fuel energy is the total energy content of the fuel consumed (GJ), LHV is the lower heating value of the fuel (MJ/kg), Total fuel cost is the total fuel cost (USD), and Fuel price is the unit fuel price (USD/GJ).
Next, compliance costs were estimated on the basis of the GFI-related economic measures under the IMO Net-Zero Framework. Under the IMO Net-Zero Framework, GFI represents the energy-based greenhouse gas intensity of fuels used by ships of 5,000 GT or more, expressed in gCO2eq/MJ, and applies economic measures according to performance relative to the applicable targets. The framework establishes a Base Target and a Direct Compliance Target on the basis of the required reduction from the reference value. When a ship’s attained GFI exceeds the applicable target, remedial units are required in proportion to the excess emissions. This study adopted 2028 as the assessment year and applied the corresponding target values.
Because the present analysis considers only TtW CO2 emissions rather than the full WtW CO2-equivalent basis used under the IMO Net-Zero Framework, a simplified TtW-CO2-based attained GFI value was calculated using Eq. (5). The value represents the energy-weighted average CO2 intensity of the fuels consumed. The calculated attained GFI was then compared with the 2028 target values used in the analysis. Fig. 5 shows the relationship among the applicable GFI targets and compliance categories. When attained GFI exceeds the Direct Compliance Target but does not exceed the Base Target, Tier 1 remedial units are required for the relevant excess emissions at a rate of USD 100 per ton of CO2. When attained GFI also exceeds the Base Target, additional Tier 2 remedial units are required for the emissions exceeding that target at a rate of USD 380 per ton of CO2. Conversely, fuel scenarios that meet the Direct Compliance Target may generate surplus units corresponding to performance beyond the target. These surplus units may be transferred or sold in accordance with the applicable framework. Excess emissions and the corresponding compliance cost were calculated using Eqs. (6) and (7), respectively.
Here, EIj is the TtW CO2 intensity of fuel j based on its emission factor and LHV (g/CO2MJ), Energyj is the energy consumption associated with fuel j (MJ), and Energytotal is the total energy consumption from all fuels (MJ). In Eq. (6), Excessemission is expressed in tons of CO2 and Carbon price in Eq. (7) is expressed in USD/tCO2.
Finally, the total operating cost defined in this study was calculated as the sum of the fuel cost and the net regulatory cost estimated under the IMO Net-Zero Framework, as expressed in Eq. (8):
4. Comparative Analysis of CO2 Emissions and Economic Performance by Fuel Type on the Korea–U.S. Route
4.1. Environmental Performance Analysis by Fuel Type
4.1.1 Analysis of Fuel Consumption and CO2 Emissions
The TtW CO2 emissions of the selected fuel scenarios were comparatively analyzed for the route from Busan to Los Angeles. Fuel consumption was estimated on the basis of the operating conditions defined above and the engine load specified for each fuel scenario. Fuel consumption was calculated using the engine-specific fuel consumption characteristics, expressed as specific fuel oil consumption (SFOC). The results showed that fuel consumption varied among the scenarios under the specified operating conditions, as shown in Fig. 6.
The HFO scenario consumed approximately 1,905,332 kg of fuel. The LNG scenario consumed approximately 1,584,631 kg of LNG and 31,716 kg of MDO as pilot fuel, resulting in a total fuel consumption of approximately 1,616,347 kg, the lowest among the scenarios. By contrast, the methanol scenario consumed approximately 3,847,124 kg of methanol and 105,852 kg of pilot MDO, resulting in the highest total fuel consumption. The greater methanol consumption resulted primarily from its low LHV, which requires a greater mass of fuel to provide the required energy. Accordingly, the CO2 emissions of the LNG and methanol scenarios were calculated on the basis of the combined consumption of the primary and pilot fuels.
The CO2 emissions for each fuel scenario were subsequently calculated by applying the fuel-specific emission factors provided by the IMO (Table 2) to the estimated fuel consumption. The pilot fuel used in the dual-fuel engines was also included in the total CO2 emissions using the same calculation method. The results are shown in Fig. 7.
The results showed that the HFO scenario emitted approximately 5,933 t of CO2, whereas the LNG scenario produced the lowest emissions, at approximately 4,459 t. This result can be attributed to LNG’s relatively low mass-based CO2 emission factor and lower fuel consumption. The methanol scenario emitted approximately 5,629 t of CO2, representing only a minor reduction relative to HFO. Although methanol has a relatively low mass-based CO2 emission factor, its low LHV results in greater fuel consumption under the assumed operating conditions, limiting the resulting reduction in total CO2 emissions. The biodiesel scenario exhibited the highest CO2 emissions, at approximately 6,108 t, because its fuel consumption was assumed to be identical to that of HFO, whereas its emission factor was assumed to be the same as that of MDO.
4.1.2 Voyage-Based CII Analysis
The voyage-based CII results for each fuel scenario are presented in Fig. 8. The CII represents the amount of CO2 emitted per unit of transport work, with a lower value indicating higher carbon intensity performance.
The results showed that LNG had the lowest voyage-based CII, at 4.44 g CO2/t NM, demonstrating the highest carbon intensity performance among the evaluated scenarios. Methanol had a CII of 5.60 g CO2/t NM, representing an approximately 5.1% reduction relative to that of HFO at 5.91 g CO2/t NM, whereas biodiesel exhibited the highest value at 6.08 g CO2/t NM. LNG achieved a voyage-based CII approximately 25% lower than that of HFO. Methanol also showed improved performance relative to HFO, indicating its potential to reduce operational carbon intensity. Overall, within this voyage-based CII comparison, LNG and methanol provided lower carbon intensity than the conventional HFO reference scenario.
4.2 Economic Analysis by Fuel Type
This section evaluated the economic performance of each fuel scenario by analyzing fuel costs and net regulatory costs estimated under the IMO Net-Zero Framework. First, the total fuel cost was calculated on the basis of fuel consumption and fuel prices. The regulatory cost was then estimated by applying the target values used in the GFI analysis. As described above, fuel prices were obtained from DNV analysis data based on documents submitted to the IMO, and the price per unit of energy (USD/GJ) was applied to each fuel. Table 4 summarizes the fuel consumption and resulting fuel costs for each scenario.
The results revealed clear differences in total fuel costs among the scenarios. HFO had the lowest fuel cost because of its low unit price, whereas LNG had the second-lowest total fuel cost because its relatively low fuel consumption partially offset its higher unit price. The primary-fuel cost of methanol was marginally higher than that of LNG, at approximately USD 1.100 million and USD 1.070 million, respectively. When pilot fuel was included, the total fuel cost of the methanol scenario increased to approximately USD 1.151 million, compared with approximately USD 1.085 million for the LNG scenario. The methanol scenario consumed more than three times as much MDO pilot fuel as the LNG scenario, further increasing the difference in total fuel cost. Biodiesel had the highest unit fuel price and was assumed to have the same fuel consumption as HFO; consequently, it exhibited the highest fuel cost among the evaluated scenarios. This result reflects the relatively high cost associated with the production and supply of biofuels.
Next, regulatory costs were estimated on the basis of the GFI targets and economic measures under the IMO Net-Zero Framework. The IMO Net-Zero Framework uses 93.3 gCO2eq/MJ, representing the average greenhouse gas intensity of international shipping in 2008, as the reference value and defines the Base Target and Direct Compliance Target according to the required reduction rates. This study applied the target values specified for 2028. Although the actual framework evaluates greenhouse gas emissions on a CO2-equivalent basis, the present analysis considered only TtW CO2 emissions to enable direct comparison among the selected fuel scenarios. The results are shown in Fig. 9.
The results showed that LNG had the lowest calculated CO2 intensity because of its low mass-based CO2 emission factor and relatively high LHV. By contrast, biodiesel exhibited the highest calculated intensity because of the combined effects of its high CO2 emission factor and relatively low LHV. HFO showed a higher calculated intensity than LNG and methanol and was therefore relatively disadvantageous under the simplified GFI assessment. Methanol exhibited a lower calculated intensity than HFO although the reduction was smaller than that achieved by LNG. Although MDO had a higher mass-based CO2 emission factor than HFO, its attained GFI on a unit-energy basis was lower because of its relatively high LHV.
Next, the regulatory costs associated with the GFI-based economic measures under the IMO Net-Zero Framework were estimated for each scenario on the basis of the fuel-specific intensities calculated above. When the calculated GFI exceeds the Direct Compliance Target, Tier 1 remedial units are required for the corresponding excess emissions. When the GFI also exceeds the Base Target, additional Tier 2 remedial units are required. By contrast, scenarios that meet the Direct Compliance Target may generate surplus units corresponding to the amount by which their performance exceeds the target. The market value of these surplus units remains uncertain. Because no definitive reference price was available, this study assumed a value of USD 380/tCO2, corresponding to the price applied to Tier 2 remedial units under the framework. Table 5 presents the results (IMO, 2025a).
None of the scenarios fell into Tier 2 on the basis of the 2028 target values adopted for the analysis. Cases 2 and 3 generated surplus units because they met the Direct Compliance Target. This study defined the estimated economic value of these surplus units, calculated on the basis of the additional reduction relative to the Direct Compliance Target, as the surplus unit value. Case 2, which used LNG, exhibited the lowest attained GFI and consequently generated the highest surplus unit value. Case 3, which used methanol, also generated surplus units, although their estimated value was lower than that of Case 2. The relatively low LHV of methanol contributed to its higher attained GFI compared with LNG. By contrast, Cases 1 and 4 incurred costs for purchasing Tier 1 remedial units because of their higher calculated intensities. Case 4, which used biodiesel, exhibited the highest attained GFI because its relatively low LHV resulted in a high CO2 intensity on a unit-energy basis. As the target values become more stringent in the future, the LNG- and methanol-based scenarios that meet the Direct Compliance Target under the target values considered here could also incur additional regulatory costs.
Finally, the total operating cost was calculated by combining the fuel cost with the net regulatory cost under the IMO Net-Zero Framework (Table 6). Case 1, which used HFO, had the lowest fuel cost but incurred an additional Tier 1 regulatory cost, resulting in a total operating cost of approximately USD 874,506. Under the assumed valuation of surplus units, Case 2, which used LNG, generated the highest surplus unit value and therefore had the lowest total operating cost, at approximately USD 408,492. Case 3, which used methanol, also generated surplus units, but its relatively high fuel and pilot-fuel costs limited its economic advantage compared with LNG, resulting in a total operating cost of approximately USD 903,465. Case 4, which used biodiesel, had the highest total operating cost, at approximately USD 2,133,245, because of its high fuel cost and additional Tier 1 regulatory cost. Under the assumptions adopted in this study, LNG therefore exhibited the most favorable combination of environmental and economic performance among the evaluated fuel scenarios.
4.3 Trade-Off Analysis of Environmental and Economic Performance by Fuel Type
This study compared the environmental and economic performance of each fuel scenario on the basis of the CO2 emissions and total operating costs calculated for a single voyage from Busan to Los Angeles. Fig. 10 shows the relationship between voyage-based CO2 emissions and total operating costs for each scenario.
Fig. 10 shows that scenarios positioned closer to the lower-left corner achieve both lower CO2 emissions and lower total operating costs, whereas those positioned closer to the upper-right corner are less favorable in terms of both environmental and economic performance. Case 2 exhibited the lowest CO2 emissions, at approximately 4,459 t, and the lowest total operating cost, at approximately USD 0.408 million, demonstrating the highest overall environmental and economic performance among the evaluated scenarios. Case 1, which used HFO, emitted approximately 5,933 t of CO2 and had a total operating cost of approximately USD 0.875 million. Although HFO had the lowest fuel cost, its high attained GFI resulted in an additional Tier 1 regulatory cost, limiting its economic advantage. As the GFI targets become more stringent, HFO may become increasingly disadvantageous over the long term.
Case 3 emitted approximately 5,629 t of CO2 and had a total operating cost of approximately USD 0.903 million. Methanol demonstrated higher environmental performance than HFO and generated surplus units by meeting the Direct Compliance Target. However, its relatively low LHV resulted in greater fuel consumption under the assumed operating conditions, and its pilot fuel consumption was higher than that of LNG. Consequently, Case 3 exhibited a higher attained GFI and total operating cost than the LNG scenario, making it less favorable overall than LNG under the assumptions adopted in this study.
Finally, Case 4, which used biodiesel, exhibited the highest CO2 emissions, at approximately 6,108 t, and the highest total operating cost, at approximately USD 2.133 million. This result was attributable to its high attained GFI, resulting from its relatively low LHV and assumed CO2 emission factor, combined with its high fuel price and additional Tier 1 regulatory cost. Nevertheless, biodiesel offers the advantage of being a drop-in fuel that can be used directly in existing diesel engines. Therefore, its future applicability may improve if production costs decline and the availability of sustainable, low-carbon feedstocks increases.
5. Conclusions and Discussion
This study comparatively analyzed the environmental and economic performance of fuel scenarios involving HFO, LNG, methanol, and biodiesel while considering the economic measures associated with the GFI-related economic measures under the IMO Net-Zero Framework. The analysis focused on the Busan–Los Angeles route and assessed fuel and regulatory costs by accounting for engine characteristics, fuel consumption, the LHV of each fuel, and the GFI target values adopted for the analysis.
The CO2 emissions analysis showed that Case 2, which used LNG, produced the lowest CO2 emissions, whereas methanol reduced CO2 emissions relative to HFO. By contrast, biodiesel produced the highest TtW CO2 emissions based on the emission factor assumed in this study. The voyage-based CII analysis also showed that LNG had the lowest carbon intensity, while methanol performed better than HFO. These differences primarily reflected the fuel-specific CO2 emissions calculated under the assumed vessel, route, and operating conditions.
The economic analysis showed that Case 2, which used LNG, had the lowest attained GFI and generated the highest estimated surplus unit value under the simplified GFI assessment adopted in this study. LNG also had the lowest estimated total operating cost and therefore exhibited the most favorable combination of environmental and economic performance under the study assumptions. By contrast, HFO and biodiesel incurred Tier 1 regulatory costs because of their relatively high attained GFI values. In particular, biodiesel exhibited the highest total operating cost because of its high fuel price and additional regulatory cost. Case 3, which used methanol, had a lower attained GFI than HFO and met the Direct Compliance Target under the target values applied in the analysis. However, methanol’s relatively low LHV resulted in greater fuel consumption under the assumed operating conditions, and its pilot fuel consumption was higher than that of LNG. Accordingly, although methanol demonstrated higher environmental performance than HFO, its estimated economic performance was less favorable than that of LNG.
The results demonstrate that regulatory treatment can substantially influence the relative environmental and economic attractiveness of marine fuels. Accordingly, fuel selection should not be based solely on voyage-level CO2 emissions but should also account for fuel energy content, fuel consumption characteristics, pilot fuel consumption, fuel prices, and regulatory costs. However, this study considered only TtW CO2 emissions, whereas the IMO Net-Zero Framework evaluates GFI on a WtW CO2-equivalent basis and accounts for relevant greenhouse gases. In addition, the analysis applied the 2028 target values adopted for this study; assessments based on progressively more stringent future targets may yield different economic outcomes. Future research should therefore incorporate WtW greenhouse gas emissions, methane slip, upstream fuel-production pathways, and actual vessel operating data to provide a more comprehensive assessment of alternative marine fuels for green shipping corridors.
PDF Links
PubReader
ePub Link
Full text via DOI
Download Citation
Print
