Blending Natural Gas and H₂

R. LAURSEN, ABS, Copenhagen, Denmark

Sea-going vessels that deliver goods, cargo and materials around the globe are often taken for granted by consumers—we rarely consider the continuous innovations above and below a vessel’s waterline. The focus on hydrogen (H₂) production and carbon capture onboard marine vessels has led to one of the newest innovations in fuel delivery systems. The system converts natural gas into H₂ and solid carbon with a liquid catalyst and molten salt, a process that will be described later in this article. The gas produced can then be used for fuel cells and/or a blend-in fuel for combustion engines or gas-fired boilers.

Using H₂ as a blend-in fuel shows promise to significantly reduce the methane slip from combustion engines and particulate matter emissions by capturing carbon in solid form before combustion. 

Collaborative mindsets reduce risks and deliver low-carbon results. The author’s company alongside Rotoboost AS and its partners uses a thermo-catalytic decomposition process (TCD) approach in which methane is broken down into H₂ gas and solid carbon using heat energy and catalysts to lower the temperature, making it more energy efficient.  

The combustion of vaporized liquefied natural gas (LNG) is used during startup and as the primary method to produce process heat. Process heat can also be produced with renewable energies such as solar, wind energy or H₂ gas combustion. 

The technology is proposed for use on various marine vessel types. A hazard identification (HAZID) risk analysis was applied to three vessel types—a product carrier, ferry and a very large crude carrier (VLCC)—to assess the technology's risk level. A HAZID analysis is used in industry for the early identification of hazards and threats and can be applied at the conceptual or detailed system design stage, process or infrastructure. Early identification and assessment of hazards such as environmental, geographical, process, fire and explosion, and health provide designers and operators essential information at the concept development phase, which has a minimal cost impact to implement necessary changes.  

Building in the technology. The TCD technology is installed using a natural gas-to-H₂ system on a side stream of a natural gas fuel feed. A part of the fuel feed is treated in the natural gas-to-H₂ system to remove carbon, producing a H₂-rich natural gas stream called decomposition gas. This is returned to the vessel’s fuel gas supply system (FGSS) and mixed with vaporized natural gas directly from the LNG fuel storage tank.  

Installation onboard smaller ships is easier because the system is prefabricated, then transported and packaged in standard high-cube International Organization for Standardization (ISO) containers. The high conversion efficiency of the TCD process ensures a compact size compared to traditional steam methane reforming (SMR) systems or electrolyzer plants. However, the process may require modifications for bigger ships to find a suitable location.  

Another benefit is that the required electrical power is significantly lower than the most advanced carbon capture, utilization and storage (CCUS), and the required storage space for solid carbon is six times less than for liquid carbon dioxide (CO₂). This means volume efficiencies are improved, providing more onboard space for cargo. The system is especially well suited for LNG carriers and other LNG-fueled ships, as they normally have existing systems that can deal with LNG containing high amounts of nitrogen. However, some of the older steam turbine ships may face challenges meeting the coming carbon intensity indicator regulation due to the fuel delivery systems to the external combustion engine. 

Succeeding with emissions challenges. Producing H₂ through TCD on carbon catalysts yields a valuable and environmentally friendly fuel in the form of H₂ and a wide range of carbon materials that can be used in several industries.

According to the 2019 Intergovernmental Panel on Climate Change results, methane produces greenhouse gases (GHGs) that are 25 times more potent than CO₂. Using H₂ as a blend-in fuel is expected to help reduce methane slip from combustion engines and reduce particulate matter emissions by capturing carbon in solid form before combustion. Blending H₂ with fuel should increase the heat released, which results in better combustion, especially for dual-fuel Otto cycle engines. These factors dramatically reduce overall carbon emissions from the vessel. 

Tests have shown that by treating approximately 20% of the fuel stream in a natural gas-to-H₂ system, an LNG carrier steam turbine vessel can reduce its CO₂ emissions below the level required by the International Maritime Organization’s 2030 target date while using conventional LNG fuel. With this new system, a vessel can continue to bunker regular LNG fuel and still dramatically reduce CO₂ emissions, leading to a better environmental index value with lower well-to-wake emissions. Depending on the heating method, this process can eliminate overall carbon emissions. 

Decomposing methane into H₂ and solid carbon is a smart way to implement a carbon capture and storage (CCS) solution onboard gas-fueled ships because it reduces storage space. The solid carbon can then be used to produce fuel cells and batteries, which can be recycled. Solid carbon is a precious raw material that can be an additional circular revenue stream for ship operators and owners.

Next steps. Low-cost, highly efficient and proven technologies can radically improve the shipping industry’s carbon footprint. This technology is a potential solution for the shipping industry that can accelerate its energy transition to meet global decarbonization goals. Focusing primarily on the TCD of natural gas or biogas into H₂ and specialty carbon can achieve a low-to-negative carbon footprint. 

Over the long term, the U.S. Department of Energy expects that H₂ production from natural gas will be augmented with production from renewable, nuclear and other low-carbon energy resources. 

With the emissions from exhaust gases, CO₂ can be incorporated into the marine transportation of fuel in the future, with the potential for this technology to be used in land-based applications as well. This is an exciting vision because the technology enables the use of fossil fuels and green fuels to impel a much faster progression toward carbon neutrality goals and wider benefits for ship operators and the international community.

About the author

RENÉ LAURSEN is a Director of Sustainability for ABS, leading the ABS Copenhagen Sustainability Center. Laursen supports shipowners in selecting the best technologies and fuel mixes for their fleets.