Alternative Marine Fuels: LNG, Methanol, Ammonia, H2

How the main alternative marine fuels compare

Four fuels lead the move away from heavy fuel oil and marine gas oil: LNG, methanol, ammonia and hydrogen. Each can be made from fossil gas, from biomass or as an e fuel from renewable hydrogen, and that origin decides most of its climate benefit.

All four carry less energy per cubic metre than marine gas oil (MGO). Lloyd's Register calculates that a ship needs about 1.78 times the tank volume for LNG, 2.44 times for methanol, 2.94 times for ammonia and 4.52 times for liquid hydrogen to carry the same energy as MGO.

Fuel	Energy density (MJ/kg)	Energy density (GJ/m³)	Tank volume vs MGO	Storage	Main challenge	Bunkering readiness
LNG	48	21.6	1.78×	Liquid at minus 162 °C	Methane slip and fossil origin	Available at 222 ports
Methanol	19.9	15.7	2.44×	Liquid at ambient temperature	Low energy density, scarce green supply	Commercial in leading hubs such as Singapore
Ammonia	18.8	13.1	2.94×	Liquid at minus 33 °C	Toxicity and N2O emissions	Pilot transfers only (Singapore, Rotterdam)
Hydrogen (liquid)	119.9	8.5	4.52×	Liquid at minus 253 °C	Very low volumetric density, cryogenics	Single project supply (Norway)

Energy and storage figures come from Lloyd's Register. LNG port numbers come from SEA-LNG's 2026 mid year review.

LNG

Liquefied natural gas is stored at minus 162 °C and burned in dual fuel engines alongside a small pilot of diesel. It is the most mature alternative fuel, with LNG bunkering available at 222 ports and 67 LNG bunker vessels in operation in mid 2026, according to SEA-LNG.

Fossil LNG cuts CO2 at the stack but offers limited savings on a well to wake basis. The reason is methane slip: unburned methane that escapes through the engine and has a warming effect many times that of CO2. FuelEU Maritime sets default slip values of 3.1% of fuel for medium speed Otto cycle dual fuel engines, 1.7% for slow speed Otto engines and 0.2% for slow speed Diesel cycle engines.

Engine choice therefore drives compliance. Operators can replace default values with measured slip, using the procedure in IMO resolution MEPC.402(83) and the Commission's 2025 guidelines.

The same engines and tanks can burn bio LNG and e methane, which deliver deep well to wake cuts. This drop in pathway is the main argument for LNG as a transition fuel.

Methanol

Methanol is liquid at ambient temperature, so it needs no cryogenic tanks and can use adapted conventional fuel systems. Its main drawback is energy density: a ship needs about 2.4 times the tank volume of MGO for the same energy.

Methanol made from natural gas, known as grey methanol, has a higher well to wake footprint than fuel oil. It creates a FuelEU compliance deficit rather than a surplus. The climate case rests on bio methanol and e methanol, which are still in short supply.

Methanol is toxic and has a low flashpoint, so ships follow IMO interim guidelines for methyl and ethyl alcohol as fuel. Singapore completed the first ship to containership methanol bunkering in July 2023.

Ammonia

Ammonia contains no carbon, so it releases no CO2 when burned. It is stored as a liquid at minus 33 °C at atmospheric pressure, or under moderate pressure at ambient temperature.

Two issues dominate. First, ammonia is toxic: exposure can severely damage the lungs and cause death, so venting is not permitted and fuel systems need vapour return lines. Second, combustion can emit nitrous oxide (N2O), a gas with a global warming potential of 265 over 100 years. Dual fuel engines also need a pilot fuel of at least 5% of consumption.

The IMO issued interim safety guidelines for ammonia fuelled ships in MSC.1/Circ.1687. Singapore hosted the first use of ammonia as a marine fuel on the Fortescue Green Pioneer in March 2024. The Port of Rotterdam completed its first ship to ship ammonia transfer of 800 m³ in April 2025.

Ammonia only delivers real cuts when produced from renewable hydrogen or with carbon capture. Grey ammonia from unabated natural gas creates a FuelEU compliance deficit.

Hydrogen

Hydrogen has the highest energy per kilogram of any fuel, at about 120 MJ/kg, but the lowest energy per cubic metre. Liquid hydrogen must be held at minus 253 °C, and compressed hydrogen at 350 or 700 bar takes even more space.

These limits confine hydrogen to short routes for now. Norled's MF Hydra, operating in Norway's Ryfylke archipelago, began running on liquid hydrogen in 2023 with an 80 m³ tank and 400 kW of fuel cells.

Hydrogen matters most as the feedstock for e methanol, e ammonia and e methane. Its climate value depends entirely on producing it from renewable or other low carbon electricity.

Orderbook trends

DNV's Alternative Fuels Insight platform recorded 137 alternative fuelled vessel orders in the first half of 2026, down from 155 a year earlier. LNG led with 73 orders, followed by LPG and ethane with 55.

Orders for carbon free and low carbon liquids were small in that period: 4 ammonia, 2 methanol and 1 hydrogen vessel. Deliveries continued from earlier orders, with 61 LNG and 38 methanol fuelled ships entering service in the same six months.

The pattern shows owners choosing LNG dual fuel as a flexible option while green methanol and ammonia supply chains develop. Orders shift quickly with fuel prices and regulation, so this page is reviewed against the latest DNV figures.

How EU rules treat each fuel

FuelEU Maritime limits the well to wake greenhouse gas intensity of energy used by ships of 5,000 GT and above. The limit tightens from 2% below the 91.16 gCO2e/MJ reference in 2025 to 6% in 2030, 14.5% in 2035, 31% in 2040, 62% in 2045 and 80% in 2050.

FuelEU counts CO2, methane and N2O across the whole fuel life cycle. LNG burned in slow speed Diesel cycle engines can earn a surplus, while high slip engines gain little. Grey methanol and grey ammonia start in deficit. Renewable fuels of non biological origin (RFNBOs) count double until 2033, and a 2% RFNBO subtarget applies from 2034 if their share is below 1% in 2031.

The EU ETS prices emissions from the exhaust. Ships surrender allowances for 40% of 2024 emissions, 70% of 2025 emissions and 100% from 2026, when methane and N2O also enter the system. Methane slip from LNG and N2O from ammonia therefore carry a direct carbon cost.

The Alternative Fuels Infrastructure Regulation (AFIR) requires an appropriate number of LNG refuelling points at TEN-T core maritime ports, subject to demand. It also requires national policy frameworks to cover hydrogen and ammonia supply in maritime ports.

FAQ

Questions, answered

Which alternative marine fuel is most widely available?+

LNG. SEA-LNG reports LNG bunkering at 222 ports and 67 LNG bunker vessels in operation in mid 2026.

What is methane slip?+

Methane slip is unburned methane that escapes from gas engines into the exhaust. FuelEU Maritime sets default slip values from 0.2% to 3.1% of fuel depending on engine type.

Is LNG a low carbon fuel?+

Fossil LNG gives modest well to wake savings that depend on engine methane slip. Bio LNG and e methane used in the same engines deliver much deeper cuts.

Why is ammonia considered a zero carbon fuel?+

Ammonia contains no carbon, so burning it emits no CO2. Its climate benefit depends on green production and on controlling N2O emissions, which have a warming potential of 265.

How much more tank space do alternative fuels need?+

Compared with MGO, Lloyd's Register calculates about 1.78 times the volume for LNG, 2.44 for methanol, 2.94 for ammonia and 4.52 for liquid hydrogen.

Which alternative fuel had the most new ship orders in 2026?+

LNG, with 73 of the 137 alternative fuelled vessel orders recorded by DNV in the first half of 2026.

How does FuelEU Maritime reward green fuels?+

It sets well to wake intensity limits that tighten to 80% below the reference by 2050. RFNBOs such as e methanol and e ammonia count double until 2033.

Sources