Future Fuel or Not, Hydrogen will Power the Clean Energy Shift

The marine industry is faced with the enormous challenge of reaching net-zero greenhouse gas emissions by midcentury to meet ambitious targets set by the International Maritime Organization (IMO). Globally, the marine sector contributes to approximately 3% of total greenhouse gas emissions, and in the US, commercial and recreational vessels accounted for nearly 3% of the country's greenhouse gas emissions in 2021. In the near term, the revised IMO GHG Strategy adopted at MEPC 80 aims to increase the uptake of zero- or near-zero-emission energy sources to 5–10% of energy from international shipping by 2030.

This cannot be achieved with technology alone.

The marine industry has evolved around the use of fossil fuels; ship designs, shipping routes, ports, fuel supply, skilled labor, and commercial business models are all keyed to the cost and energy density of diesel. Achieving our near- and long-term maritime decarbonization goals will not only require improvements in the efficiency of technologies like fuel cells, batteries, and clean combustion, but the industry will also need to make a major shift towards low- or zero-carbon fuels that are both clean to produce and consume.

It's not at all clear what the fuel or fuels of the future will be. Green methanol, green ammonia, green hydrogen, and even some biofuels all show promise, but the ability of these fuels to scale successfully will dictate whether or not they are adopted. Today’s fossil fuels are extracted from wells and then refined and transported to markets, but fuels of the future will need to be manufactured. This will take process energy and feedstock materials, collectively known as a fuel pathway, which can have an enormous impact on the carbon intensity of a fuel. Not only will the energy to produce the fuels or feedstocks need to come from zero-carbon sources, such as wind, solar, or nuclear—they will also need to economically viable.

Most hydrogen today is made from steam methane reformation (SMR), sometimes called “grey hydrogen.” This is currently the lowest-cost means of producing hydrogen, but it also generates a significant amount of carbon dioxide. For additional cost, it is possible to add carbon capture and storage (CCS) downstream of the SMR process. Hydrogen made from SMR combined with CCS is known as “blue hydrogen.” Electrolysis powered by renewable electricity, such as solar or wind, can be used to separate oxygen and hydrogen from water. The hydrogen produced by this process is called “green hydrogen.” The industry uses these colors because differentiating the various production pathways is essential to understanding the carbon intensity of hydrogen as a fuel or a feedstock. It is clear that a lot of green hydrogen will be needed for the energy transition, but today the cost is many times higher than grey hydrogen. This is a challenge that the US Government is attempting to address.

The Inflation Reduction Act (IRA) is the largest investment in reducing carbon pollution in US history and is expected to reduce US carbon emissions 40% by 2030. The Energy Earthshots^™ initiatives were launched in 2021 by the DOE to accelerate breakthroughs in clean energy within a decade. Two of these, the Hydrogen Shot and the Clean Fuels & Products Shot are significant for the maritime industry’s need for greener fuels. The former seeks to lower the cost of clean hydrogen by 80% in ten years, to one dollar per kilogram. The latter’s goal is to decarbonize the fuel and chemical industries and advance cost-effective technologies with a minimum of 85% lower GHG emissions by 2035.

The Bipartisan Infrastructure Law (BIL) has funded seven regional clean hydrogen hubs (H2Hubs), managed by the DOE’s office of clean energy demonstrations. The H2Hubs will invest in both blue and green hydrogen as part of the US plan to jump-start the clean hydrogen industry. These are a key piece of the national clean hydrogen strategy and are aligned with the Hydrogen Interagency Task Force which is coordinating the government’s holistic approach to developing green hydrogen.

As a fuel, hydrogen produces neither carbon nor local emissions. It can be combusted in an engine to produce mechanical power or chemically reacted with oxygen in fuel cells to produce electricity. Fuel cells can be used to power electric ships, but some efficiency losses must be accounted for in the electrical conversion. Like many emerging technologies, fuel cells present challenges associated with cost, scale, and regulatory maturity, but are quieter and more efficient than a combustion engine.

Hydrogen has low energy density compared to other fuels, but is an attractive option for the right application. Hydrogen can be stored as a compressed gas or as a liquid; liquid hydrogen is a cryogenic fuel and more energy dense than compressed hydrogen, but it is harder to make, more challenging to handle, and requires special equipment to store and vaporize before use. Compressed hydrogen is less energy dense but easier to produce and simpler to store and use. For short-range applications where battery-electric is not feasible, hydrogen may be an excellent fuel choice. Battery-electric has become an increasingly popular method of converting ferries and other harbor craft to zero emissions, but requires access to shore power for charging. For many marine electrification projects, it can be expensive and time-consuming to get the necessary charging infrastructure permitted and built. The power required for rapid shoreside charging puts a strain on the grid and batteries are often a necessary addition to charging infrastructure to minimize peak loads. Harbor vessels and ferries operating in areas that cannot support shoreside charging could benefit from hydrogen fuel as an alternative to electrification.

The marine industry is not alone in the need for clean fuels or green hydrogen. Other industries considered hard to abate, such as aviation, steel production, and agriculture, could become large consumers of green hydrogen as both a fuel and a feedstock for various low-carbon fuels or chemicals. The aggregate demand for green hydrogen will help to drive the costs down as well as the required infrastructure needed for production and distribution. Production will require massive amounts of carbon-free electricity such as wind, solar, geothermal, and nuclear power, as well as new facilities for fuel production. New infrastructure will be needed for transport and storage, which could benefit the marine industry. For example, specialized tankers will be needed to transport the fuels from where they are produced to where they will be consumed, and ports will need ways to store and transfer clean fuels so ships can be bunkered for long voyages.

Moving the needle for marine decarbonization and the production of green fuels will require domestic and global action. COP 28 saw landmark agreements to scale up renewable energy, phase out fossil fuel subsidies, ramp up clean hydrogen production, and increase energy efficiency. The Green Shipping Challenge, co-led by the US and Norway, spurred COP 28 announcements around actions to increase use of low- and zero-carbon fuels. The process of shifting industry away from a reliance on fossil fuels is well underway. Already we are seeing initiatives to prepare the supply chain for clean fuel and the development of new and existing technologies required to achieve decarbonization targets. Regardless of whether hydrogen emerges as the fuel of the future, all low- or zero-carbon fuels depend on its abundance and availability. The chemical energy in all potential marine fuels—whether diesel, methanol, methane, ammonia, or even pure hydrogen—comes from the rearrangement of hydrogen atoms during chemical reactions in combustion engines or fuel cells. New technologies will be required to reach our lofty decarbonization targets, but the energy transition will only be possible through a massive scaling up of production and green fuels, renewable and clean energy, and a lot of hydrogen.