What fuels are being considered to decarbonize shipping?

Shipping is weighing several alternative fuels, chiefly LNG, methanol, ammonia, and hydrogen, alongside battery-electric and solar-electric systems like the one Voltic has patented for retrofitting existing cargo ships. No single fuel has become the industry standard, and each option trades off differently on emissions, cost, and how much of the ship needs to change.

LNG is the most established of the alternatives and already has fueling infrastructure at many ports, according to SEA-LNG. It cuts some emissions compared to heavy fuel oil, but it is still a fossil fuel and leaks methane, a potent greenhouse gas.

Methanol has become the leading alternative fuel by new vessel orders, according to Ethanol Producer Magazine, with major carriers including Maersk and CMA CGM among the buyers. It can be produced from renewable sources, but green methanol supply remains limited relative to global fuel demand.

Ammonia and hydrogen offer zero or near-zero emissions at the point of combustion, per a ScienceDirect review of alternative marine fuels, but both require new engine designs, new fuel storage, and new bunkering infrastructure that barely exists today. Ammonia is also toxic, which adds handling and safety requirements.

Electric propulsion, Voltic's focus, avoids combustion fuel entirely. Voltic's patented system retrofits existing cargo ships with solar collection area well beyond what the deck can hold, without replacing legacy infrastructure, positioning electrification as a retrofit path rather than a new-fuel-and-new-engine path.

The Global Maritime Forum has noted there is no single fuel that will decarbonize shipping on its own. The fleet is likely to run on a mix of these options, split by ship type, route, and how much retrofit versus new-build capacity is available.