The safety of alternative fuels on board

The drive for energy independence and decarbonisation means interest in alternative fuels is at an all-time high. But what are the safety concerns for vessel...

The drive for energy independence and decarbonisation means interest in alternative fuels is at an all-time high. But what are the safety concerns for vessels powered by or transporting alternative fuels?  

With the global energy transition underway, many eyes are on the early adopters to see how safely fossil fuels can be substituted on board, and where the challenges and risks exist with transporting and storing fuels such as hydrogen and methanol.  


Hydrogen is a promising fuel, due to its high energy content per unit of mass. It is however highly flammable, and easy to ignite where there is air. Due to its relatively low heating value and density, it requires a special engine design, potentially with larger engine dimensions and high pressure. Careful risk analysis should be carried out on all onboard storage, handling and refueling systems.  

The economic potential of hydrogen is high. Take the Susio Frontier, the world’s first liquefied hydrogen carrier, that was developed to transport liquefied hydrogen at 1/800 of its original gas-state volume, cooled to –253°C. The ship is part of the Hydrogen Energy Supply Chain (HESC) project partnered by nine heavyweights including Kawasaki Heavy Industries and Shell. The maiden voyage from Japan to Australia was plain sailing although a fire incident reported on 25 January when it was moored in Hastings on the Mornington Peninsula is being investigated by the Australian Transport Safety Bureau. On 25 February, the Suiso Frontier returned to Kobe in Japan thereby delivering the world’s first cargo of liquefied hydrogen to the country. 

TechnoVeritas has also focused on hydrogen and has designed an alkaline electrolyser to produce hydrogen, as well as solutions for the storage and transportation of hydrogen and the conversion of most existing diesel engines to dual fuel, making use of hydrogen with pilot diesel. 


Ammonia’s main safety concern is that it is toxic and can be deadly when exposed. To prevent leakage, shipyards need to rework the design of fuel storage, distribution, and bunkering systems. Ammonia has a much lower density than other fuels, causing a design and engineering challenge since shipyards need to reconfigure ships to carry enough ammonia fuel on board safely.  

Maersk is working with maritime industry leaders to investigate ammonia’s potential in Singapore, exploring the design of ammonia bunkering vessels, as agencies in Singapore help standardise operations and regulations, while also looking at dual fuel ammonia engines.  


As a fuel, methanol is toxic, explosive and flammable, and must be stored and handled with care. Shipowners with methanol onboard should undertake comprehensive hazard testing. Ships that use methanol as fuel must be specifically designed to protect crews and operations. 

Maersk has also committed to methanol and has signed up to be one of six partners in an e-methanol plant in Asia. The company is also partnering with several energy and fuel companies to source at least 730,000 metric tons of green methanol by the end of 2025. In addition, the company has eight methanol-powered 18,000 TEU container vessels on order from Hyundai Heavy Industries (HHI), which will be on the water by 2025. 

CW 2 Maersk new generation engine

One of eight methanol-powered 18,000 TEU contained vessels ordered by Maersk (Credit: Maersk) 

The root of the challenge 

The main obstacle to transitioning lies in the lack of a pre-existing infrastructure designed for these new fuels. Bunkers and vessels have been designed for natural gas, so adaption will be needed, with new technologies brought in, and relevant safety measures in place. 

Dr Tristan Smith is Associate Professor at UCL Energy Institute and is also member of the IMarEST’s Marine Fuels and Emissions Special Interest Group. “Much is written about danger as if it is a physical property of a fuel,” says Smith. “It is not, it is the consequence of the physical properties of a fuel in combination with how physical systems that use it are designed, how human and operational processes are specified and how people are trained.” 

Smith reminds the marine industry that it is not an insurmountable challenge to store and transport these new fuels in vessels. “Hydrogen, ammonia and methanol are all in widespread use, they have different hazards arising from their characteristics and we have decades of experience of safely storing and handling them in multiple different land and sea systems.”  

To adapt safely, technologies and skills and progress should be shared. Care and appropriate safety measures will need to be outlined. A safe transition requires standardised safety specifications, minimising costs from design to production, with appropriate training and re-training programs available. Achieving these milestones will set the standard for the use of alternative fuels in shipping, to decarbonise the global industry.

Join the IMarEST’s Marine Fuels and Emissions Special Interest Group by logging into your My IMarEST account, click on My Special Interest Groups and then tick the boxes of the SIGs you’d like to join. You can then also join the groups on Nexus, our networking platform.

Clarissa Wright

Clarissa Wright is a freelance journalist