Exploring Alternative Fuels in the Maritime Industry

No single alternative fuel is going to replace marine diesel across the whole fleet. Each option trades off energy density, storage complexity, safety requirements, and fuel availability differently, which is why the industry is moving toward a mixed picture rather than one universal answer.

The main candidates

• LNG — the most mature alternative in commercial service, with an established bunkering network. Cuts SOx and particulate emissions significantly but only offers a modest CO2 benefit once methane slip is accounted for, and needs cryogenic tanks at around -162°C, which costs hull volume conventional fuel doesn't.
• Methanol — liquid at ambient temperature, which makes storage and handling far closer to conventional fuel than the alternatives. Lower energy density means larger tanks for the same range, and green methanol supply is still limited.
• Ammonia — no carbon at the point of combustion, but toxic, corrosive, and flammable within a specific concentration range in air, requiring dedicated containment, detection, and crew safety systems that are still being standardised across class societies.
• Hydrogen — highest potential for zero-emission propulsion, particularly via fuel cells, but very low volumetric energy density even when liquefied, which currently limits it to auxiliary power and shorter-range applications.
• Biofuels — usable in existing engines with little or no modification, which makes them the fastest practical decarbonisation lever for an existing fleet, constrained mainly by feedstock supply and cost.

What actually limits adoption

The technical case for most of these fuels is well understood; what's missing is infrastructure. Bunkering availability, crew training, classification society rules, and port safety procedures all lag behind engine technology. A vessel converted to run on ammonia or hydrogen today may have very few ports where it can actually refuel, which makes fuel choice as much a route-planning and infrastructure decision as an engineering one.

How to think about it for your vessel

For most owners and operators, the near-term decision isn't "which alternative fuel" but "how much flexibility does my next engine or refit give me." Dual-fuel capability, methanol-ready fuel systems, or simply specifying equipment that doesn't foreclose a future retrofit tends to be the more realistic strategy than committing fully to a single alternative fuel today.

Southern Ocean Marine advises owners and managers on fuel-system specification during new-build and refit planning, and provides independent condition surveys and due diligence when evaluating a vessel's existing propulsion and fuel infrastructure against future compliance requirements.