Ship-source emissions of air contaminants and of greenhouse gases from the combustion of marine fuels is driving the adoption of cleaner fuel alternatives.

Maritime transportation is crucial to world trade. Approximately 90% of all goods traded are carried by marine vessels at some point in their supply chains. Of the more than 50,000 vessels registered worldwide, most are designed for either deep-sea shipping (transporting cargo) or short-sea shipping (moving people and freight in coastal locales).

Nearly all are powered by fossil fuel oils, which are burned in combustion engines. These vessels generate 15% of global nitrogen oxide emissions, 13% of sulfur oxide emissions, and 2.2% of carbon dioxide emissions. The International Maritime Organization (IMO), which regulates ship-source pollution, has established progressive targets to manage overall emissions downward over time, achieving at least 50% reduction in greenhouse gases by 2050, en route to a phase-out that is consistent with the Paris Agreement’s temperature goals.

A transition to alternative fuels in the marine sector is considered critical to achieving the IMO’s decarbonization goals. Candidate alternatives must be less carbon intense than their supply chains today and have a pathway for ongoing decarbonization over the long term as well. In this report, an initial set of nine fuel types were considered, which were pared down to the following five priority systems:

• liquefied natural gas;
• biofuels;
• methanol;
• hydrogen; and
• battery-electric.

For each system, a fuel-by-fuel assessment was conducted with insights on marine applications, decarbonization pathways, business case factors, fuelling technology and supply chain readiness, and regulatory drivers and status.

Each can leverage existing infrastructure and technology, and each can be made progressively less carbon-intense over time if synthesized from renewable, low-carbon, and carbon-neutral sources. Industry trials and commercial deployments of alternatives fuels are at a nascent stage, with only a handful of pilot projects from which to draw insight, and there is a need to move this work further ahead to ensure a successful transition to alternative fuels.

This research report resulted in the following findings that are critical to this transition to alternative fuels:

1. There is no distinct regulatory framework currently in place for alternative marine fuels, despite the significant number of guidance documents that exist, to guide the operators of ports, ships, and fuel providers in the adoption of alternative fuel bunkering systems
2. Currently, alternative fuel projects are considered and treated as exceptions. Regardless of whether that process follows the “normal” process or if a new process specific to that fuel type is developed, it needs to ensure that all the technical and safety requirements are met.
3. Standardized equipment and codified procedures are difficult to achieve in the early days of alternative fuel development. A standardized approach for design, deployment, and use of alternative fuels in the marine sector should be developed.

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