Decarbonization involves alternative fuels and operations with new safety-related risks (DNV GL, 2020a). Through our white paper on safety published earlier this year (DNV, 2021a), we argued that with all eyes focused on transformations in digitalization and decarbonization, we as an industry need to commit ourselves as much to safety as to transformation. After all, the safe and timely transition towards a digitally smart and carbon-neutral future may be compromised if the safety-related risks that these transitions bring about are not accounted for.

A successful uptake of alternative fuels depends on the development of efficient safety regulations and the ability to implement a safety culture where all stakeholders take the responsibility to handle the new challenges introduced with the new fuels. 

The gradual introduction of LNG as a fuel, examples set by first movers, and the experience of decades of carriage and consumption of boil-off on gas carriers have been important for the wider uptake for deep-sea shipping we see indications of today. The entry into force of the IGF Code 17 years after the launch of a Norwegian LNG-fuelled ferry, Glutra, provided an international regulatory framework to handle gases and other lowflashpoint fuels, and is a result of 20 years of learnings and experiences of designers, shipowners, manufacturers, yards, flag states and classification societies in how to safely integrate onboard LNG fuel systems. Based on these experiences and the carriage on board gas carriers, DNV has also developed rules for the other relevant hydrocarbon gas, LPG, applying the same safety principles. 

To a lesser degree, similar experiences have been gained for methanol through carriage and use as fuel on chemical carriers and as a common cargo on offshore supply vessels. An IMO interim guideline for methyl/ethyl alcohols as fuel is in place, providing guidance and support for the integration of the onboard fuel system. 

For ammonia the picture is different. The maritime industry has experience with carriage of ammonia in gas carriers and as a refrigerant in refrigeration plants, but not as a fuel. Due to its toxicity, the introduction of ammonia as fuel creates new challenges related to safe bunkering, storage, supply and consumption. Available energy converters could be 3-4 years away, and regulatory developments in IMO are not yet initiated. Considering the urgency to decarbonize shipping, major deployment of ammonia as fuel may happen faster than for LNG, LPG, and methanol, which means additional 36 focus should be on the installation and safe operational practices. DNV published the first class rules for ammonia as fuel in July 2021 to accommodate owners, shipyards, and designers considering ammonia as fuel. 

Hydrogen is not transported as a marine cargo, and the experiences as a marine fuel are currently limited to small-scale R&D projects. The safety implications of storing and distributing hydrogen on board ships are not clear. The general understanding of hazards and risk associated with hydrogen, and particularly liquefied hydrogen (LH2), is limited. Consequently, no class rules or prescriptive international regulations have yet been developed. Several R&D initiatives are currently ongoing to improve the understanding of LH2 and associated hazards. For hydrogen the potential explosion risk related to the low ignition energy and the wide flammability range requires special attention. The very low boiling temperature for hydrogen makes it more challenging to store in its liquefied form. 

It is sometimes argued that experience from land-based installations proves that a technology can be safely used on board ships. There are however principal differences to be considered. It is a well-established principle in the IMO and class rules that the level of safety requirements is increased when land-based technology is applied to ships. This relates to a variety of conditions: 

• A ship operating out in the open seas is self-reliant and can in most instances not rely on help from outside. 
• Crew and passengers cannot escape to safety in the same way as from a car or within a building on shore. 
• Due to space constraint, the safety distances are much smaller on ship than a comparable installation on shore. 
• The environmental conditions are challenging on board ships with humidity, sea spray, vibrations and inclinations. 
• The power demand for a ship is in a different order of magnitude compared to other applications (for instance automotive) considering similar fuel technology. 
• Low temperature materials are a necessity for many fuels. As opposed to supporting structures for onshore facilities, ship steel is not resistant to low temperatures. 

For the above reasons, land-based solutions are not directly transferable to ships. The qualification of land-based technologies for maritime use adds time and cost.

(SOURCE: DNV'S Maritime Forecast to 2050, Edition 2021, pages 36/37)