Fuel scenarios

Connecting the shipping sector with the global energy system requires integrating it into an Integrated Assessment Model (IAM), enabling a more comprehensive analysis of its future role in energy transitions. We achieve this by linking the output of the MariTEam model with MESSAGEix, a widely used integrated assessment model that assesses long-term energy supply and demand dynamics under different scenarios. By integrating detailed shipping activity data, fuel consumption, and emissions from MariTEam into MESSAGEix, we can explore how maritime transport fits within broader energy system transformations. This approach allows us to assess potential fuel pathways, considering factors such as resource availability, technology development, policy interventions, and economic feasibility. Additionally, it enables a systemic evaluation of how shifts in the global energy mix influence the viability of different fuels for shipping, such as hydrogen, ammonia, biofuels, or advanced synthetic fuels. By embedding shipping into a larger IAM framework, we provide insights into its potential contribution to global decarbonization efforts, ensuring that maritime transport is aligned with sustainable energy transitions and climate policy targets.

Greenhouse gas emission projections

The Paris Agreement, adopted in 2015, set a global framework for limiting temperature rise to well below 2°C above pre-industrial levels, with efforts to keep it below 1.5°C. As a key sector in global emissions, international shipping has a crucial role in contributing to these climate goals. The International Maritime Organization (IMO), the UN body responsible for regulating global shipping, has committed to achieving net-zero greenhouse gas (GHG) emissions by 2050. This commitment marks a significant step toward aligning maritime transport with the broader decarbonization efforts required under the Paris Agreement.

Emission factors

Depending on the chosen fuel pathway, we adopt different emission factors to account for upstream emissions, ensuring a comprehensive assessment of the total greenhouse gas (GHG) impact of maritime fuels. Upstream emissions include those generated during fuel extraction, production, processing, and transportation before it is used onboard ships. For example, fossil-based fuels like LNG have significant upstream methane emissions, while hydrogen and ammonia can have widely varying footprints depending on whether they are produced from fossil fuels (grey or blue) or renewable sources (green). Biofuels also vary in their emissions based on feedstock type and land-use impacts. By incorporating these upstream emission factors, we can provide a more accurate picture of the true environmental impact of different fuel choices, helping to identify pathways that contribute most effectively to the decarbonization of the maritime sector. This approach ensures that fuel transitions are evaluated holistically, avoiding potential emissions displacement and supporting more sustainable policy and investment decisions.

Table of experiments

The table summarizes a series of experiments exploring various scenarios related to global and shipping sector net-zero emission targets, along with specific emission accounting methods and constraints. These scenarios include a range of budget allocations in gigatonnes of CO₂ (GtCO₂), with targets set for both the world and shipping sector net-zero years, spanning from 2055 to 2075. The emission accounting method used in some scenarios is “Well-to-Wake,” which tracks emissions throughout the lifecycle of fuels. Additionally, some experiments impose specific constraints, such as excluding certain technologies like ammonia, biofuels, biomass, or carbon capture and storage (CCS), or limiting energy efficiency gains. These diverse scenarios provide insights into the impacts of different pathways and constraints on achieving global and shipping sector emissions reductions in line with the 1.5°C and 2°C climate goals.

Fuel mix

In this analysis, we present the projected shipping fuel mix for the scenario in which the maritime sector achieves net-zero emissions by or around 2055. This scenario reflects a rapid transition away from conventional fossil fuels, driven by stringent climate policies, technological advancements, and shifts in global energy markets. As shipping decarbonizes, we see a significant rise in the adoption of low-carbon and zero-carbon fuels, such as green hydrogen, ammonia, biofuels, and synthetic e-fuels, replacing traditional marine fuels like heavy fuel oil (HFO) and marine gas oil (MGO). The pace and composition of this transition depend on factors such as fuel availability, infrastructure development, regulatory frameworks, and economic competitiveness. Additionally, energy efficiency measures and emerging propulsion technologies, such as wind-assisted systems and electrification for short-sea shipping, further contribute to emissions reductions. By illustrating this fuel mix, we provide insights into the pathways that could enable the shipping industry to align with long-term climate goals, highlighting both opportunities and challenges in the transition to a sustainable maritime energy system.

Integrating into the Global Energy System

In this analysis, we present the projected shipping fuel mix for the scenario in which the maritime sector achieves net-zero emissions by or around 2055. This scenario reflects a rapid transition away from conventional fossil fuels, driven by stringent climate policies, technological advancements, and shifts in global energy markets. As shipping decarbonizes, we see a significant rise in the adoption of low-carbon and zero-carbon fuels, such as green hydrogen, ammonia, biofuels, and synthetic e-fuels, replacing traditional marine fuels like heavy fuel oil (HFO) and marine gas oil (MGO). The pace and composition of this transition depend on factors such as fuel availability, infrastructure development, regulatory frameworks, and economic competitiveness. Additionally, energy efficiency measures and emerging propulsion technologies, such as wind-assisted systems and electrification for short-sea shipping, further contribute to emissions reductions. By illustrating this fuel mix, we provide insights into the pathways that could enable the shipping industry to align with long-term climate goals, highlighting both opportunities and challenges in the transition to a sustainable maritime energy system.

If we re-arrange the the primary energy into different major source categories, as shown belown, we can see the differences in scale of change that are required to transition the global and the shipping energy mix to meet the Paris Agreement and the the IMO 2050 net-zero goals. Whereas at a global there is margin for fossil fues to be used (38% of primary energy), the shipping sector would required almost an entire phase-out of fossils towards biomass.

Author: Diogo Kramel
Model: MariTeam model
Repository: GitHub
Data Version: v1.0.0 | 2025-02-13
Latest Update: March 24, 2025
Contact: diogo.kramel@ntnu.no