Predictions for 2025: The challenge of future fuels

Question: With the rise of alternative fuels like ammonia, methanol, and hydrogen, what challenges and opportunities do these fuels present for propulsion system designs and retrofits?

John Bergman, CEO of Auramarine: ”The main challenges with the adoption of these future fuels are related to their high toxicity and the need for special fuel storage and handling requirements. Safe infrastructure, naturally, requires significant investment as well, which is another hurdle for shipowners.

“But at the same time, these alternative fuels also hold significant potential to reduce emissions, improve sustainability and meet industry decarbonisation targets; both through retrofitting existing vessels, as well as within newbuilds. In a multi-fuel future, whichever fuel ship owners opt for, the emphasis must be on delivering highly innovative and reliable fuel supply systems to ensure safety and operational efficiency.”

Roger Holm, president of Wärtsilä Marine and excutive vice president of Wärtsilä Coroporation: “Firstly, when talking about sustainable fuels in maritime, it is important to talk about the space needed onboard a ship for the needed endurance. Space on a ship is always optimised for maximum cargo or passengers. For methanol, the space needed is close to two times more compared to existing fuels, and for ammonia it is almost four times. This is still an acceptable compromise to decarbonise shipping. For hydrogen, however, the space needed is close to 20 times for compressed hydrogen. Along with challenges around storage and fuel supply, currently the market outlook for hydrogen in land-based applications seem stronger than marine-based applications.

More generally, whilst alternative fuels offer promising pathways to reduce emissions, their widespread adoption hinges on scaling up infrastructure and supply chains. During this transitional period, it will be essential to prioritise fuel flexibility and readiness for sustainable fuels. This approach will help establish the necessary foundation for the final push toward achieving net-zero emissions.

The good news is that many newbuilds and retrofits are already incorporating engines which can run on alternative when the fuel availability is there. These engines – such as dual-fuel engines – offer shipowners the flexibility to adapt to shifting market demands and emerging technologies without the need to make major modifications in the future. In the meantime, these engines allow operators to minimise emissions and ensure the most efficient energy utilisation during operations.

By preparing for multiple options, operators can lower the risk of stranded assets and make headway on the industry’s decarbonisation targets today. 

Jonathan Strachan, CTO of Houlder: “The challenges of alternative fuels are different in each case, but one common theme is the lower energy density by volume and mass (Hydrogen by volume only). This requires larger bunkers to carry the same amount of energy, and larger bunkers mean either larger ships or small cargo capacities. There is an opportunity for ship operators to look at the current bunkering patterns and reappraise what they need to do going forward, rather than operating as they have always done.

The challenges that specific alternative fuels present to designers are likely to lead to different uptakes of certain alternative fuels if different shipping sectors, for example we might see low uptake of ammonia in the passenger ship sector due to its toxicity.”

Stergios Stamopoulos, director of global sustainability at ABS: ”The rise of alternative fuels such as ammonia, methanol, and hydrogen, presents complex challenges and transformative opportunities for propulsion system designs and retrofits. A significant challenge lies in the physical and chemical properties of these fuels, which differ considerably from traditional marine fuels.

For instance, ammonia’s toxicity and corrosive nature demand robust safety measures and specialized materials for storage, handling, and bunkering, while hydrogen’s low energy density requires advanced solutions for onboard storage in either compressed or liquefied forms.

Methanol, though easier to handle, requires specialized fire detection and fighting systems due to the low visibility of its flame. For some of the alternative fuel options, their lower energy density means more frequent bunkering and less space for cargo.

These challenges increase the complexity and cost of retrofitting existing ships, as many legacy systems were not designed with such fuels in mind.

On the opportunity side, these fuels hold immense potential to decarbonise maritime propulsion, helping the industry achieve long-term regulatory compliance and sustainability goals. For new vessel designs, propulsion systems optimised for alternative fuels enable shipowners to prepare their fleets to align with zero-carbon shipping aspirations. Retrofitting older vessels to accommodate these fuels provides a pathway for operators to extend asset lifespans while meeting evolving environmental standards. Additionally, integrating these fuels with hybrid or renewable energy solutions, such as fuel cells or batteries, offers further opportunities to enhance efficiency and operational flexibility.

The adoption of alternative fuels will likely create a ripple effect across the value chain, driving advancements in fuel infrastructure, safety protocols, and crew training, thereby reshaping the maritime propulsion landscape.”