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Methanol as marine fuel

Methanol (CH3OH) is a single-carbon alcohol that can be burned in adapted marine diesel engines as either the primary fuel or a blend, stored as a liquid at ambient temperature and pressure, and produced from a range of feedstocks ranging from natural gas to renewable electricity and captured carbon dioxide. Its density is 791 kg/m³ and its lower heating value is 19.9 MJ/kg - roughly half that of heavy fuel oil on a mass basis - which requires approximately twice the bunker volume for equivalent energy. Its principal emission advantages over conventional residual fuels are the complete elimination of sulphur oxides, a reduction of nitrogen oxide emissions by 25 to 30% without exhaust after-treatment at Tier II operating conditions, and a reduction in particulate matter of approximately 90%. When produced as e-methanol from renewable hydrogen and biogenic or directly captured CO2, the well-to-wake greenhouse gas intensity approaches zero, qualifying it as a Renewable Fuel of Non-Biological Origin (RFNBO) under FuelEU Maritime. The commercial fleet burning methanol as its primary fuel expanded rapidly from 2023 as Maersk took delivery of its methanol-capable container ships. ShipCalculators.com provides a dedicated suite of methanol fuel tools; see the ShipCalculators.com calculator catalogue for the full list.

Contents

Background and history

Early industrial use

Methanol has been produced industrially since the 1920s. The first commercial synthesis route used wood distillation, which gave the compound the alternative name wood alcohol. By the 1930s, a more efficient route from synthesis gas - a mixture of carbon monoxide and hydrogen obtained by steam reforming of natural gas or by coal gasification - had displaced wood-derived production for all practical purposes. The reaction of carbon monoxide (CO) with hydrogen (H2) over a copper-zinc-alumina catalyst at pressures of 50 to 100 bar and temperatures of 200 to 300°C yields methanol in high selectivity. This natural gas reforming route, now termed grey methanol, remains the source of roughly 90% of global production; world output was approximately 100 million tonnes per year in 2022.

Methanol’s role as a marine fuel was investigated intermittently from the 1990s in the context of SOx and NOx abatement, but the economics of conventional shipping fuels prevented commercial adoption. The decisive shift came from two converging pressures: the IMO 2020 sulphur cap that entered into force on 1 January 2020 under MARPOL Annex VI, and the growing regulatory pressure on greenhouse gas emissions through the CII system and the EU’s FuelEU Maritime and EU ETS for shipping. Together these created a market for fuels with a fundamentally different emissions profile. Methanol, as a liquid at ambient conditions with mature global logistics, presented a more accessible entry point for many operators than liquefied gases such as LNG or ammonia.

First marine applications

The Swedish ferry Stena Germanica became the world’s first operational methanol-fuelled vessel of significant size when Stena Line carried out a fuel conversion in 2015 at Remontowa Shipyard in Gdansk. The ship operates on the Kiel to Gothenburg route and uses methanol supplied from a storage tank installed on the car deck. The conversion required new fuel storage tanks, a modified injection system, and a methanol supply rail feeding MAN Diesel & Turbo 4-stroke medium-speed engines adapted for low-flashpoint operation.

The Stena Germanica conversion established a practical baseline for regulatory compliance, crew training, and operational procedures. It preceded the MAN Energy Solutions two-stroke ME-LGIM engine platform by one year but demonstrated that methanol combustion in existing four-stroke machinery was feasible at scale with modifications to fuel delivery and safety systems.

The period from 2015 to 2021 saw limited commercial uptake of methanol propulsion beyond Stena Line. Several factors constrained uptake: the absence of an established methanol bunkering network, uncertainty about long-term fuel pricing, and the lack of a newbuild two-stroke engine with a commercial track record. Small methanol-fuelled tankers and inland vessels operated in China and Europe, primarily on routes close to industrial methanol production facilities. Research vessels and ferries with captive routes and accessible methanol storage demonstrated operational readiness, but ocean-going vessels required the assurance of global bunkering before committing to methanol propulsion.

The inflection point came with Maersk’s 2021 announcement that it had ordered the world’s first methanol-fuelled ocean-going container ship and that the company intended methanol to anchor its near-term decarbonisation strategy. This announcement legitimised the technology for the broader shipping industry and triggered a rapid expansion of methanol engine orders, yard capabilities, and port investment.

Physical and chemical properties

Molecular structure and purity

Methanol is the simplest alcohol, consisting of one carbon atom bonded to three hydrogen atoms and one hydroxyl (OH) group. Its molecular formula is CH3OH and its molar mass is 32.04 g/mol. Commercial methanol for industrial use is typically greater than 99.85% pure (AA grade per ASTM D1152 / IMPCA specifications), with principal impurities being water, ethanol, acetone, and traces of formaldehyde. Marine fuel-grade methanol does not yet have a universally adopted quality specification analogous to ISO 8217 for conventional fuels; ISO Technical Committee 28 published ISO 6583-1 as the first bunkering standard for methanol and ethanol as marine fuels in 2023, covering delivery procedures and documentation rather than fuel composition limits. DNV and Bureau Veritas have issued class guidelines that reference fuel quality requirements for methanol in engine manufacturers’ specifications, which generally require water content below 0.1% by mass and methanol content above 99.5%.

Density and volumetric energy considerations

The density of liquid methanol at 15°C is 791 kg/m³. By contrast, heavy fuel oil has a density of approximately 980 kg/m³ and marine gas oil approximately 840 kg/m³. The lower density of methanol means that, for a given tank volume, the mass of fuel stored is approximately 19% less than for MGO and approximately 19% more than for LNG at atmospheric pressure, but LNG requires cryogenic containment. Since methanol is liquid at ambient temperature - its boiling point is 64.7°C - it can be stored in conventional steel tanks without insulation or refrigeration, a major operational advantage.

The lower heating value (LHV) of methanol is 19.9 MJ/kg, compared to approximately 40.2 MJ/kg for HFO and approximately 50.0 MJ/kg for LNG. The volumetric energy density of methanol is therefore approximately 15.7 GJ/m³, compared to approximately 35.5 GJ/m³ for HFO and approximately 22.4 GJ/m³ for LNG at cryogenic conditions. A vessel designed to carry 3,000 tonnes of HFO for a given voyage range would require approximately 6,200 tonnes of methanol for the same energy, requiring approximately 7.8 times the volume compared to the equivalent HFO mass - because the lower calorific value reduces mass-based energy content by half, and the lower density reduces the volumetric packing further. Tank space requirements are therefore a critical constraint in newbuild methanol vessel design and a significant cost driver for retrofit projects. The net calorific value calculator for methanol and the methanol fuel summary calculator provide rapid conversions between energy and mass or volume.

Flash point and fire hazard classification

The flash point of methanol is 11°C. The IGF Code (International Code of Safety for Ships Using Gases or Other Low-flashpoint Fuels, adopted by IMO resolution MSC.391(95) in 2015) applies to fuels with a flash point below 60°C. Methanol is therefore classified as a low-flashpoint fuel under the IGF Code and as a flammable liquid under IMDG. This has substantial implications for tank location, secondary barriers, gas detection systems, ventilation, and crew training requirements aboard methanol-fuelled ships. By contrast, HFO has a flash point above 60°C and is handled under conventional MARPOL Convention Annex VI provisions without the additional IGF Code overlay. The IMO IGF Code calculator assists in applying the code requirements.

Methanol vapour forms a flammable mixture with air in a concentration range of 6 to 36.5% by volume (flammable range), which is somewhat narrower than that of hydrogen but broader than that of many hydrocarbons. Its relatively low vapour density (1.11 relative to air) means vapour does not pool heavily at deck level but can accumulate in enclosed spaces. Safe fuel handling procedures require continuous ventilation monitoring and gas detection in fuel spaces. Methanol is also toxic: the oral lethal dose for humans is approximately 1 mL/kg, and inhalation or dermal absorption presents significant health hazards to crew. These factors inform the spill response procedures required by classification societies and outlined in IMO MSC.1/Circ.1621 (2020), the Interim Guidelines for the safety of ships using methyl/ethyl alcohol as fuel.

Miscibility, corrosivity, and material compatibility

Methanol is fully miscible with water in all proportions. Fire suppression with water therefore dilutes spilled methanol rather than displacing it, which affects the selection of firefighting agents. Alcohol-resistant aqueous film-forming foam (AR-AFFF) or dry powder systems are required for methanol fires rather than standard AFFF. The IBC Code categorises methanol as a Type II cargo requiring stainless steel or epoxy-coated steel tanks for bulk chemical transport. The IBC data sheet is accessible via the IBC methanol calculator.

Methanol attacks certain elastomers, including nitrile rubber and natural rubber, and is incompatible with zinc and aluminium alloys without passivation. Fuel system components - seals, gaskets, hose linings, and pump materials - must be selected from methanol-compatible materials: typically stainless steel, Viton (fluorocarbon rubber), polytetrafluoroethylene (PTFE), and selected nylons. Engine manufacturers publish approved material lists for fuel circuit wetted parts.

Viscosity and pump characteristics

Methanol has a kinematic viscosity of approximately 0.6 cSt at 20°C. This is substantially lower than that of HFO (typically 10 to 15 cSt at injection temperature, reduced from several hundred cSt at ambient) and somewhat lower than that of MGO (approximately 2 to 4 cSt). The low viscosity of methanol means that conventional positive displacement pumps designed for HFO will exhibit increased internal bypass leakage, reducing volumetric efficiency. Methanol fuel pumps in the ME-LGIM supply circuit must therefore be specifically designed or selected to maintain tight clearances compatible with low-viscosity service. The low viscosity also means that methanol provides substantially less lubrication to sliding surfaces in injection pumps and valves than conventional fuel oils; anti-wear additives approved by the engine manufacturer are sometimes specified for the pilot fuel circuit.

Unlike HFO, methanol does not require preheating before pumping. The absence of a heating system for the main fuel supply simplifies machinery space arrangements and reduces heat load on the fuel conditioning module, though the double-wall piping requirement for safety purposes adds weight and complexity to offset this.

Auto-ignition temperature and cold start

Methanol’s auto-ignition temperature is approximately 470°C in air at atmospheric pressure. This is higher than that of diesel fuel (approximately 250°C) and HFO (approximately 300°C), which means methanol will not ignite spontaneously in the cylinder under standard marine diesel compression ratios without a pilot fuel or external ignition source. This property underpins the mandatory pilot fuel requirement in all current compression-ignition methanol engines: the pilot fuel ignites under compression and creates a propagating flame that triggers methanol combustion. At low ambient temperatures, cold-starting procedures require particular attention to ensure adequate pilot fuel delivery before transitioning to methanol mode; engine manufacturers specify minimum coolant and lube oil temperatures for methanol fuel mode entry.

Production pathways

Grey methanol from natural gas reforming

Grey methanol is produced by steam methane reforming (SMR) of natural gas. Natural gas reacts with steam over a nickel catalyst at approximately 850°C to produce synthesis gas (syngas: H2 and CO), which is then converted to methanol over a copper-zinc oxide catalyst. The overall well-to-tank CO2 equivalent intensity of grey methanol is approximately 1.1 to 1.5 tonnes of CO2 equivalent per tonne of methanol produced, depending on energy efficiency, methane leakage rate, and the carbon intensity of any process heat. China produces methanol from coal gasification rather than natural gas; coal-to-methanol has a significantly higher carbon footprint, with WTT intensities of approximately 2.0 to 2.5 t CO2-eq/t methanol, roughly double the natural gas route. China’s coal-based methanol represents a large fraction of global production capacity but is largely decoupled from the marine bunker market at present. The methanol lifecycle CO2 LCA calculator and the methanol well-to-wake calculator quantify these pathways.

Blue methanol with carbon capture and storage

Blue methanol applies carbon capture and storage (CCS) to the SMR process, capturing the CO2 produced during reforming and sequestering it in geological storage. CCS can reduce the WTT carbon intensity of methanol to approximately 0.2 to 0.5 t CO2-eq/t methanol depending on the capture rate achieved and any residual methane leakage from upstream gas production. Blue methanol has attracted commercial interest as a near-term decarbonisation step because it uses established SMR technology and existing methanol production infrastructure. Projects in Norway and the Netherlands aim to integrate large-scale geological CO2 storage with methanol production plants adjacent to natural gas reserves.

Green methanol and e-methanol

Green methanol encompasses two overlapping categories: bio-methanol from biomass, and e-methanol (electro-methanol or power-to-X methanol) from renewable electricity.

Bio-methanol is produced by gasification of biomass - municipal solid waste, agricultural residues, woody biomass, or black liquor from pulp mills - to produce syngas, followed by the same methanol synthesis step as in grey methanol production. The carbon in the product methanol originates from atmospheric CO2 absorbed by the biomass during growth; if the biomass feedstock is sustainably managed, the WTT GHG intensity can be close to zero or even negative when combined with biochar co-production that sequesters residual carbon.

E-methanol is produced by reacting green hydrogen with CO2. Green hydrogen is produced by electrolysis of water using renewable electricity; the electricity requirement is approximately 55 to 60 kWh per kilogram of hydrogen at current electrolyser efficiencies. The CO2 feedstock can come from biogenic point sources (biogas upgrading, fermentation, pulp mills), direct air capture (DAC), or industrial point sources (cement, steel). The overall energy efficiency of the e-methanol chain - from renewable electricity to ship propulsion - is approximately 14 to 18%, accounting for electrolyser efficiency, methanol synthesis efficiency, and engine thermal efficiency.

Carbon Recycling International (CRI) in Svartsengi, Iceland, has operated the world’s first commercial scale renewable methanol plant since 2011, expanded in 2012 and 2021 to a capacity of approximately 4,000 tonnes per year of methanol branded George Olah Renewable Methanol. The process uses CO2 captured from the exhaust of the adjacent Svartsengi geothermal power plant and hydrogen produced by electrolysis powered by geothermal electricity. The specific geographic conditions - cheap renewable electricity and a concentrated CO2 source from a near-zero-carbon energy system - make Iceland’s e-methanol among the lowest carbon intensity in commercial production.

At larger scale, HIF Global is developing the Haru Oni pilot plant in Punta Arenas, Chile, using wind electricity from Patagonia to produce green hydrogen and e-methanol. The project aims to reach 550 million litres of e-fuel per year by 2026 at full build-out. A.P. Moller - Maersk has partnered with Orsted and European Energy to develop e-methanol supply chains supporting its container ship fleet.

The e-methanol fuel summary calculator provides GHG intensity estimates across the e-methanol production chain. The bio-methanol summary calculator covers the biomass gasification route.

Engine technology

MAN Energy Solutions ME-LGIM

The MAN Energy Solutions ME-LGIM (Low pressure Gas Injection Methanol) is the first large two-stroke diesel engine designed for methanol as the primary fuel in ocean-going vessels. The engine is a variant of the ME-C long stroke slow-speed diesel family, adapted with a methanol high-pressure fuel injection system and a pilot fuel system that delivers a small quantity of marine gas oil or very low sulphur fuel oil as an ignition pilot. The ME-LGIM operates on the diesel cycle (compression ignition) rather than spark ignition; pilot fuel quantities are typically two to five per cent of total fuel energy at full load, rising to a somewhat higher fraction at low loads where methanol ignition characteristics are less favourable.

The engine uses direct injection of methanol in liquid phase at pressures of approximately 600 bar, similar to the injection pressures for conventional marine diesel. This distinguishes the low-pressure designation from the high-pressure dual-fuel gas injection systems used in LNG engines; in the ME-LGIM context, “low pressure” refers to the methanol supply pressure to the fuel pump inlet, as methanol is liquid at ambient conditions, rather than to injection pressure. The methanol is pressurised from the supply rail to injection pressure by engine-driven high-pressure pumps - the same mechanical arrangement as for HFO in the standard ME-C engine.

MAN announced the ME-LGIM design commercially in 2016, one year after the Stena Germanica conversion demonstrated four-stroke methanol combustion. The first commercial newbuilds to specify the ME-LGIM were container ships ordered by Maersk; the first vessel of the Laura Maersk class, a 2,100 TEU feeder, entered service in August 2023 powered by a MAN 6S60ME-LGIM engine. Subsequent deliveries from Hyundai Mipo Dockyard and other yards followed for the larger 16,000 TEU class methanol vessels. The engine is available in bore sizes from 50 cm to 90 cm, corresponding to power outputs covering feeder through very large container ship applications. Engine performance data are available in the MAN ES S60ME-LGIM engine calculator.

WinGD X-DF-M

WinGD (Winterthur Gas and Diesel) is developing the X-DF-M (X-type Dual-Fuel Methanol) two-stroke engine as a competitor to the ME-LGIM. The X-DF-M is designed as a port-injection system in which methanol is injected into the scavenge air port rather than directly into the cylinder. This low-pressure port-injection approach differs fundamentally from the ME-LGIM high-pressure direct injection and is more similar to the lean-burn premixed combustion concept used in some four-stroke gas engines. WinGD had not yet entered full commercial production with the X-DF-M as of early 2026; the engine was in design validation and bench testing phases. Port injection reduces the complexity and cost of the high-pressure methanol pump and injector system but requires careful attention to fuel-air mixture homogeneity to avoid local rich zones that produce formaldehyde and unburned methanol emissions.

Four-stroke medium-speed engines

Wartsila, Caterpillar (MaK), and Bergen Engines have investigated four-stroke methanol combustion for medium-speed engines used in ferries, smaller cargo ships, and offshore vessels. The Stena Germanica retrofit used Wartsila-modified MAN 4-stroke machinery. Four-stroke methanol engine development has continued through the 2020s with test bed programmes targeting Tier III NOx compliance with methanol at lower SCR penalty than with HFO.

Wartsila has developed the 32 methanol engine as a medium-speed genset engine for ferries and offshore support vessels, using a pilot-ignited methanol injection system with a dedicated low-flashpoint fuel module. For vessels where the propulsion load is provided by diesel-electric or hybrid-electric propulsion trains, the flexibility of engine room layout is greater than for direct-drive two-stroke configurations, and multiple medium-speed engines can be arranged with independent fuel supply systems, improving redundancy.

Fuel system architecture aboard ship

The methanol fuel system on a large ocean-going vessel typically comprises a storage tank section, a day tank or settling tank section, a fuel conditioning module (FCM), and a high-pressure injection circuit. Storage tanks are double-hull construction with inert gas padding and continuous gas detection in the annular space. The FCM includes filters, temperature control (methanol’s viscosity is low and largely insensitive to temperature, but temperature monitoring is required for safety), flowmeters for consumption metering, and the interface to the bunker delivery system. The high-pressure injection pumps are co-located with or closely coupled to the engine. Separate dedicated pilot fuel systems for MGO or VLSFO are retained alongside the methanol circuit, each with its own day tank, filters, and metering.

Vapour management is a significant design challenge because methanol vapour is heavier than LNG vapour but lighter than HFO vapour. The double-wall piping requires a ventilated annular space maintained at a slight negative pressure to capture any methanol vapour leaking from the inner pipe; this vapour is directed to a mast vent or a vapour combustion unit rather than being released to atmosphere. The vapour detection systems must cover not only the fuel preparation room and engine room but also any enclosed spaces adjacent to methanol piping routes, including pump rooms, cofferdams, and ventilation trunking.

Pilot fuel requirement and dual-fuel operation

All current methanol marine engines retain the ability to switch to a backup liquid fuel - marine gas oil or VLSFO - providing fuel flexibility unavailable in single-fuel designs. This dual-fuel capability is operationally significant because methanol bunkering infrastructure remains sparse relative to conventional distillate bunker ports. A vessel can enter a port without methanol supply and bunker MGO instead, resuming methanol combustion once it reaches a port with methanol availability. The flexibility also provides a safety margin during early-stage methanol supply chain development. Because the engine does not require natural gas high-pressure storage systems, the methanol ship avoids the cryogenic infrastructure costs associated with LNG vessels. The dual-fuel formaldehyde and hydrocarbon emissions calculator estimates unburned methanol and formaldehyde slip rates at various load fractions.

Emission profile

Sulphur oxides and particulate matter

Methanol contains no sulphur. Combustion of pure methanol therefore produces zero sulphur dioxide (SO2) and zero sulphate particulate, irrespective of the proportion of methanol burned. Where pilot fuel is used, sulphur emissions from the pilot fraction are negligible given its two to five per cent energy share. Methanol-fuelled vessels therefore comply with MARPOL Annex VI global sulphur caps and ECAs by design, without requiring exhaust gas cleaning systems (scrubbers) or the use of distillate fuels in emission control areas.

Particulate matter emissions from methanol combustion are reduced by approximately 90% compared to HFO combustion on an energy-equivalent basis. HFO-derived particulates include black carbon soot, organic carbon, metals from vanadium and nickel in the oil, and secondary sulphate aerosol. Methanol combustion produces minimal soot because the oxygen in the fuel molecule interrupts the soot-forming radical pathways; the black carbon emissions calculator illustrates the difference in formation mechanisms between residual and alcohol fuels.

Nitrogen oxides

Methanol combustion at equivalent thermal load produces approximately 25 to 30% less NOx than HFO combustion in a comparable engine operating at Tier II conditions. The mechanism is primarily thermal: methanol’s high latent heat of vaporisation (about 1,100 kJ/kg, compared to approximately 250 kJ/kg for HFO) cools the cylinder charge and reduces peak combustion temperatures, which are the main driver of Zeldovich thermal NOx formation. The flame temperature of methanol is also slightly lower than that of hydrocarbons of equivalent calorific value.

However, 25 to 30% NOx reduction does not reach IMO Tier III compliance in NOx Emission Control Areas (NECAs); Tier III requires approximately an 80% reduction relative to Tier II, which cannot be achieved by fuel switching alone. Methanol vessels operating in NECAs therefore still require selective catalytic reduction (SCR) systems. SCR on a methanol vessel imposes an additional capital and operating cost comparable to SCR on an HFO vessel, but the methanol vessel’s lower baseline NOx means the SCR system operates at a lower urea (AdBlue) consumption rate and with a lower catalyst loading duty.

Carbon dioxide - tank-to-wake

The tank-to-wake CO2 emission factor for methanol combustion is approximately 1.375 t CO2 per tonne of methanol burned, derived from the carbon content of the molecule. Given that the carbon fraction by mass is 12.01 / 32.04 = 37.5%, and each carbon atom produces one CO2 molecule (molar mass 44.01 g/mol), the factor becomes 0.375 × (44.01 / 12.01) = 1.375 t CO2/t methanol. The equivalent factor for HFO is approximately 3.114 t CO2/t fuel, reflecting HFO’s much higher carbon content per unit mass.

On an energy basis, however, the comparison changes. The CO2 per unit of energy for methanol is 1.375 / 19.9 MJ/kg = 69.1 g CO2/MJ. The equivalent for HFO is 3.114 / 40.2 = 77.5 g CO2/MJ. Methanol therefore emits approximately 11% less CO2 per unit of energy released in combustion compared to HFO, reflecting methanol’s higher hydrogen-to-carbon ratio. This energy-basis comparison is the quantity that governs CII, EEDI, and EEXI calculations. The CO2 from fuel combustion calculator handles methanol alongside conventional fuels. The CII attained calculator incorporates methanol’s emission factor in CII computations.

Unburned methanol and formaldehyde

A persistent concern with methanol combustion is the emission of unburned methanol and formaldehyde (HCHO), a partial oxidation product formed in the lower-temperature regions of the combustion zone. Published engine test data for the ME-LGIM indicate unburned methanol slip of approximately 1 to 2 g/kWh and formaldehyde emissions of approximately 0.1 to 0.4 g/kWh at representative loads. These quantities, while small in mass terms, are toxicologically significant. Formaldehyde is a Group 1 human carcinogen (IARC classification) at chronic low-level exposure and an acute irritant at higher concentrations. Current MARPOL Annex VI regulations do not impose limits on methanol or formaldehyde emissions from ship exhausts, though the IMO is developing guidelines for non-methane hydrocarbon and aldehyde emissions from alternative fuels through the Sub-Committee on Pollution Prevention and Response.

Greenhouse gas - well-to-wake

The well-to-wake (WTW) greenhouse gas intensity of methanol depends critically on the production pathway. For grey methanol from natural gas reforming, the WTW intensity is approximately 94 to 105 g CO2-eq/MJ, which is broadly similar to or slightly worse than that of HFO (approximately 93 g CO2-eq/MJ WTW per the IMO Fourth GHG Study 2020). Blue methanol with high-efficiency CCS can reach approximately 15 to 35 g CO2-eq/MJ. Bio-methanol from sustainably sourced agricultural residues achieves approximately 5 to 20 g CO2-eq/MJ. E-methanol from renewable electricity and biogenic or direct air-captured CO2 can achieve below 5 g CO2-eq/MJ WTW, qualifying as an RFNBO under FuelEU Maritime with a full 2× multiplier credit on the GHG intensity calculation. The FuelEU GHG intensity calculator and the RFNBO multiplier calculator implement the FuelEU Maritime methodology for e-methanol cargoes.

The N2O and CH4 emissions from methanol combustion are currently treated as negligible in IMO accounting; unlike LNG, methanol does not present a significant methane slip risk. However, if the methanol supply chain involves natural gas feedstock, upstream methane leakage during gas production and transmission contributes to WTW emissions and must be included in lifecycle assessments. The N2O emissions calculator and the voyage fuel CO2 calculator support complete GHG accounting on a per-voyage basis.

Regulatory framework

IMO Interim Guidelines MSC.1/Circ.1621

IMO Maritime Safety Committee Circular MSC.1/Circ.1621, issued in 2020, provides Interim Guidelines for ships using methyl/ethyl alcohol as fuel. These interim guidelines preceded the development of a dedicated chapter within the IGF Code specifically addressing methanol. The circular covers risk-based design for methanol fuel systems, fire protection, ventilation of fuel spaces, gas detection requirements, emergency shutdown systems, and personnel safety. It sets out the documentation that flag states and classification societies should review before approving methanol fuel systems.

The IGF Code itself, as adopted in 2015 through IMO resolution MSC.391(95), contains a general section covering alternative fuels of flash point below 60°C and an LNG-specific chapter. A methanol-specific chapter (Part E) was developed through IMO correspondence groups and adopted through subsequent MSC amendments. Ships already operating under MSC.1/Circ.1621 have generally been accepted by flag states and classification societies as meeting the intent of the emerging Part E requirements.

MARPOL Annex VI - emission compliance

Methanol-fuelled vessels comply with MARPOL Annex VI Regulation 14 (SOx and PM) automatically because methanol contains no sulphur and produces minimal particulate matter. They satisfy Regulation 13 (NOx Tier II) without SCR at sea or in NOx Tier I areas, but require SCR in IMO Tier III NECAs established in the North American ECA, the US Caribbean ECA, the North Sea/Baltic ECA, and any future ECAs. The MARPOL NOx Tier 2 calculator and NOx Tier 3 calculator support compliance verification.

Under MARPOL Annex VI Regulation 22A (CII rating scheme, effective from 2023), the fuel’s CO2 emission factor is used to compute the attained annual CII. Methanol’s energy-basis CO2 intensity (approximately 69 g CO2/MJ) gives a lower attained CII contribution per unit of energy than HFO (approximately 77.5 g CO2/MJ), provided the vessel is burning pure methanol. However, the doubled fuel volume requirement increases the risk of CII deterioration through increased voyage time if bunkering stops become more frequent.

FuelEU Maritime

Under Regulation (EU) 2023/1805 (FuelEU Maritime), the GHG intensity of ship fuel is assessed on a well-to-wake basis. E-methanol qualifies as an RFNBO if produced from renewable non-biological sources of hydrogen and non-biological CO2, receiving a 2× multiplier credit when demonstrating compliance with the FuelEU intensity target. The GHG intensity default value for e-methanol under FuelEU Maritime is expected to be below 25% of the 2020 fossil fuel comparator value of 91.16 g CO2-eq/MJ, enabling significant balance credits. Vessels operating in EU ports are subject to FuelEU from 1 January 2025. Methanol ships earning RFNBO credits may participate in FuelEU pooling arrangements with non-compliant vessels, generating commercial value for the surplus. The FuelEU pooling calculator and FuelEU penalty calculator quantify these mechanics. EU ETS certificates are required for methanol CO2 at the tank-to-wake factor; e-methanol with near-zero tank-to-wake intensity receives a corresponding near-zero ETS liability.

Classification society notations

The main classification societies have developed formal notations for methanol fuel readiness and methanol-capable designs. ABS offers the Methanol Fuel Ready notation for vessels designed to be converted to methanol but not yet operating on it. DNV has a Fuel Ready(Methanol) notation. Lloyd’s Register offers a Methanol class notation. These notations require verification that structural, safety system, and firefighting provisions meet the IGF Code and MSC.1/Circ.1621 requirements, and that equipment in fuel spaces is rated for methanol service. Bureau Veritas and ClassNK have comparable provisions. Classification society notations are commercially significant because they affect insurance conditions, charterer preferences, and the vessel’s attractiveness to future operators wishing to switch to methanol operation.

Bunkering infrastructure and supply chain

Current port coverage

Methanol bunkering infrastructure was sparse as of early 2026 but growing more rapidly than for ammonia as marine fuel. The first ship-to-ship methanol bunkering for a commercial ocean-going container vessel took place in Rotterdam in September 2023 when Maersk’s Laura Maersk received a methanol bunker delivery. Subsequent bunkering occurred in Singapore, Shanghai, New York, and Ulsan (South Korea). Rotterdam has the most developed methanol bunkering chain, benefiting from existing methanol terminal infrastructure at the Maasvlakte and the proximity of OCI Global’s methanol storage and distribution assets.

Methanol is already transported globally as a bulk chemical cargo on dedicated chemical tankers subject to the IBC Code, and large methanol storage terminals exist in Houston, Rotterdam, Singapore, and several Chinese ports. This pre-existing logistics infrastructure - distinct from LNG, which required entirely new cryogenic port terminals - gives methanol a relative advantage in bunkering infrastructure development. The conversion of existing product tanker berths to methanol bunkering service is technically straightforward, requiring primarily safety upgrades and the installation of methanol-compatible hoses and connection flanges. The methanol bunkering calculator covers delivery rate, loading time, and vapour return flow calculations.

ISO 6583-1 bunkering standard

ISO 6583-1, published in 2023, establishes requirements for the documentation, metering, sampling, and safety protocols governing methanol and ethanol bunkering operations at marine facilities. It defines the content of a methanol bunker delivery note (BDN), minimum sampling requirements, and procedures for emergency disconnection and spill response. The standard draws heavily on ISO 13984 (LNG bunkering) and ISGOTT (International Safety Guide for Oil Tankers and Terminals) adapted for the specific hazard profile of methanol. Alignment between ISO 6583-1 and IMO MSC.1/Circ.1621 has been maintained through joint working group liaison.

Supply chains and production scale

Global methanol production capacity of approximately 130 million tonnes per year (2023) is dominated by Asia, with China accounting for roughly 40%. The fraction directed to marine fuel applications in 2024 was a few hundred thousand tonnes, small relative to total production but growing. Maersk’s fleet of 18+ methanol container ships nominally consumes approximately 1 to 1.5 million tonnes of methanol per year at full operation, a quantity representing a few per cent of global production. Cosco’s 12+ methanol vessel orderbook and CMA CGM’s methanol-ready vessels add further demand. The growth trajectory suggests methanol demand from shipping could reach four to ten million tonnes per year by 2030, requiring dedicated production investment beyond reallocation from existing industrial supply.

The price of grey methanol was in the range US$350 to US$500 per tonne in 2024, reflecting natural gas feedstock costs. E-methanol production costs were US$1,200 to US$1,800 per tonne in 2024, driven by the high cost of renewable hydrogen and the capital intensity of electrolysers and methanol synthesis plant. The price gap between grey and e-methanol is expected to narrow through the 2030s as electrolyser costs decline and CO2 pricing mechanisms increase the effective cost of grey methanol. The lifecycle total cost of ownership fuel calculator compares the full-voyage fuel cost of methanol and conventional alternatives.

Fleet development and orderbook

Maersk methanol programme

A.P. Moller - Maersk committed to methanol propulsion as the primary newbuild fuel strategy in 2021, ordering twelve large methanol-capable container ships from Hyundai Heavy Industries and Hyundai Mipo Dockyard. The order grew to at least 18 vessels across two size categories: a 2,100 TEU feeder class (Laura Maersk and sisters) and a 16,000 TEU class (the Ane Maersk and sisters). All vessels use MAN ME-LGIM engines and are capable of operating on either green methanol or MGO. The Laura Maersk was the first to deliver, in August 2023, followed by the Ane Maersk in February 2024. Maersk secured e-methanol supply agreements with Orsted, European Energy, and WasteFuel Global to progressively increase the share of green methanol in its bunker supply. Maersk has been explicit in public statements that methanol is a bridging fuel to ammonia or hydrogen in the long term, but that methanol’s liquid ambient state and existing logistics make it deployable within the 2023 to 2030 window while green ammonia infrastructure is established.

Cosco and CMA CGM

China Ocean Shipping Company (Cosco) ordered at least 12 dual-fuel methanol container ships from Chinese yards including Jiangnan Shipyard and Shanghai Waigaoqiao Shipbuilding as part of a fleet renewal programme driven partly by Chinese coastal emission control area requirements and partly by FuelEU exposure on European routes. CMA CGM ordered at least six methanol-ready vessels with option rights, defining “methanol-ready” as having the structural and safety provisions to install methanol fuel systems without dry-dock structural modification if market conditions warrant. MSC has also explored methanol ordering as part of its alternative fuel strategy.

Wallenius Wilhelmsen and ro-ro vessels

Wallenius Wilhelmsen has studied methanol propulsion for its ro-ro vessel fleet under the Orcelle Wind concept, which combines wind-assisted propulsion with zero-carbon fuel. The ro-ro sector is considered a strong candidate for methanol adoption because ro-ro vessels operate on regular routes between fixed ports, making dedicated methanol bunkering terminals feasible at a small number of call points.

Ferry and short-sea shipping

Beyond the deep-sea container sector, methanol adoption is progressing in the ferry and short-sea shipping segments. The Stena Germanica established the precedent. Several ferry operators in Northern Europe and Scandinavia have methanol conversion studies or newbuild designs under development, facilitated by proximity to Nordic bio-methanol production from forestry residues. Short voyage profiles mean that the increased bunker volume requirement is less constraining than on deep-sea routes.

Bulk carrier sector

The bulk carrier sector has been slower to adopt methanol than container shipping, primarily because bulk carrier earnings are more cyclical and the capital investment in methanol propulsion is harder to justify against volatile freight rates. However, major bulk carrier operators including Norden (formerly D/S Norden) have conducted methanol feasibility studies, and some long-term chartered vessels have incorporated methanol-readiness provisions as a condition of charter. The bulk carrier’s large ballast water capacity and ability to allocate cargo hold space on selective basis provide design flexibility for methanol tank integration that does not exist in tankers with fixed cargo tank arrangements.

General cargo and multi-purpose vessels

Multi-purpose general cargo ships on regional European routes face the most immediate FuelEU and EU ETS compliance pressure, because their trading patterns concentrate EU port calls. Several European short-sea operators have explored methanol as the preferred compliance fuel because the bio-methanol supply chain from Scandinavian forestry co-products is more accessible and the port infrastructure more developed than for other alternative fuels in northern European ports.

Comparison with LNG, ammonia, and conventional fuels

Comparison with LNG

LNG as marine fuel offers a higher energy density (approximately 22.4 GJ/m³ at cryogenic conditions versus approximately 15.7 GJ/m³ for methanol at ambient) and a well-developed bunkering network at major ports. LNG’s tank-to-wake CO2 factor is approximately 2.75 t CO2/t LNG, and its energy-basis CO2 factor is approximately 55 g CO2/MJ - lower than methanol’s 69 g CO2/MJ on a tank-to-wake basis. However, LNG carries methane slip risk: unburned methane in the exhaust has a 100-year global warming potential of approximately 28 to 34 times that of CO2, and even a small slip fraction degrades the well-to-wake GHG performance significantly. High-pressure direct injection LNG engines (MAN ME-GI) achieve methane slip below 0.1 g/kWh, while low-pressure premix engines can reach 1 to 3 g/kWh at part load. Methanol has no equivalent methane slip risk.

LNG requires cryogenic storage at −162°C, demanding vacuum-insulated Type C pressure vessels or membrane tanks with thermal management systems. The capital cost of LNG tank systems is substantially higher than for ambient-temperature methanol tanks of equivalent volume. LNG fuel system safety involves cryogenic burn risk, while methanol presents toxic and flammability hazards. Both are regulated under the IGF Code. LNG bunkering infrastructure is considerably more developed, with approximately 200 LNG bunkering locations globally in 2024, compared to approximately 10 to 15 for methanol.

From a CII and EEDI perspective, methanol is slightly disadvantaged relative to LNG on a tank-to-wake energy basis, but the well-to-wake picture reverses when bio- or e-methanol is used versus fossil LNG. The FuelEU GHG intensity calculator and CII attained calculator allow direct comparison of the two fuels on a per-voyage basis.

Comparison with ammonia

Ammonia as marine fuel offers a carbon-free combustion product - the only combustion product of ammonia is nitrogen and water - making its tank-to-wake CO2 emission zero. This is structurally superior to methanol for deep decarbonisation. However, green ammonia production efficiency is lower than e-methanol because the additional Haber-Bosch step consumes approximately 0.6 to 0.8 kWh/kg NH3 of additional energy. Ammonia is highly toxic (IDLH 300 ppm in air, TLV-TWA 25 ppm), requires careful safety management aboard ship, and its combustion produces NOx slip at levels requiring SCR treatment. Ammonia is not yet deployed in commercial deep-sea propulsion (as of early 2026); engine development is at prototype and order stage. Methanol therefore has a three to five year commercialisation lead over ammonia in the marine sector.

Comparison with HFO and VLSFO

On a unit energy cost basis, grey methanol was approximately twice the cost of HFO in 2024 at US$350 to US$500/t for methanol versus approximately US$450 to US$500/t for VLSFO (which has approximately double the energy content per tonne). E-methanol at US$1,200 to US$1,800/t was approximately six to eight times the energy-equivalent cost of VLSFO. Carbon pricing through EU ETS narrows the gap: at EU ETS prices of approximately €60 to €70/t CO2 in 2024, the effective cost increment on HFO from the ETS was approximately €185 to €215/t HFO (for a 3.11 t CO2/t fuel factor), modestly widening the economic case for methanol. As ETS prices rise over the 2030s, the carbon cost differential becomes more material. The voyage fuel CO2 calculator and FuelEU compliance balance calculator quantify the combined regulatory fuel cost picture for mixed-fuel fleets.

Comparison with biofuels

Biofuels in shipping, particularly FAME (fatty acid methyl esters) and HVO (hydrotreated vegetable oil), offer a direct drop-in or near-drop-in option for existing HFO- or MGO-burning vessels without engine modification. Bio-methanol competes with FAME and HVO as a biogenic fuel pathway, but requires engine modification or a methanol-capable newbuild. FAME blends are limited by cold flow properties, oxidation stability, and microbial contamination at concentrations above 7% by volume in HFO blends. Methanol does not blend with HFO; it is always a dedicated fuel system. For newbuilds where the operator commits to alternative fuel propulsion, methanol and biofuels serve different market segments rather than competing directly.

Safety and crew training

IGF Code requirements in practice

The practical safety requirements for a methanol-fuelled vessel under the IGF Code and MSC.1/Circ.1621 include: double-wall or equivalent secondary barrier around methanol fuel piping in accommodation-adjacent spaces; continuous gas detection in fuel spaces with alarms linked to engine room and bridge; manual and automatic emergency fuel shutoff valves with remote actuation; anti-static earthing provisions for methanol transfer (methanol has electrical conductivity that is low compared to most chemical cargoes but higher than hydrocarbons, reducing static accumulation risk); inert gas or nitrogen blanket in fuel storage tanks to prevent vapour-air mixtures reaching the flammable range; and fire suppression systems compatible with alcohol fires (CO2 fixed systems or alcohol-resistant foam).

Officers responsible for methanol fuel operations must hold an advanced training certificate for low-flashpoint fuel operations in accordance with STCW 2010 Manila Amendments and associated STCW Code section B-V/1-1 and V/1-2. Classification society approved familiarisation courses for methanol are offered by training institutions including WMU Malmo, MTI (Maersk Training), and DMET Denmark. The STCW Convention background and the ISM Code requirements for safety management system documentation of non-standard fuel operations both apply.

Spill response and environmental considerations

A methanol spill to sea is substantially different in environmental consequence from an HFO spill. Methanol is fully water-soluble and biodegrades rapidly by aerobic and anaerobic bacteria; its environmental persistence is measured in days rather than months. This contrasts sharply with HFO, which forms tarry surface slicks and persists in the environment for years. The Bunker Convention (IOPC Fund / CLC 1992 framework as extended) covers methanol-fuelled vessels as bunkered ships; third-party liability for methanol spills is covered under standard P&I arrangements, with spill response requiring containment and dilution rather than skimming.

However, methanol’s high toxicity to marine organisms at acute exposure levels (LC50 for fish is in the range 10 to 100 mg/L depending on species) means that a large spill could cause localised marine mortality before dilution and biodegradation occur. The environmental impact profile is therefore fundamentally different from HFO: shorter-lived but acutely toxic to aquatic organisms in the near-field zone.

Current developments

Scale-up of green methanol production

The central constraint on methanol decarbonisation is the availability of green or e-methanol at competitive cost and scale. The International Renewable Energy Agency (IRENA) has projected that green hydrogen costs could fall from approximately US$4 to US$7/kg in 2024 to US$1 to US$2/kg by 2030 with scale-up of electrolysis manufacturing. At US$1.50/kg H2, the feedstock cost of e-methanol would correspond to approximately US$380 to US$420/t of methanol (hydrogen accounts for approximately 0.2 kg per kg of methanol by mass), before adding CO2 capture, synthesis plant capital, and operating costs. This would bring e-methanol within approximately 50 to 70% premium over grey methanol, a level at which carbon pricing and FuelEU multiplier credits could close the gap for compliant vessels.

Several announced projects aim to produce green methanol at scales relevant to shipping: European Energy and others in Denmark; DG Fuels in Louisiana using agricultural waste; and OCI Global with methanol production assets adjacent to renewable energy projects. The development of a certified supply chain with independently verified GHG intensity certification (using the ISCC PLUS or RED II framework for the EU market) is proceeding in parallel with production scale-up.

IMO GHG strategy alignment

The IMO 2023 revised GHG Strategy targets a net-zero (or near zero) emission shipping sector by approximately 2050, with a 20 to 30% reduction in total GHG emissions from international shipping by 2030 relative to 2008 levels, and a 70 to 80% reduction by 2040. The strategy identifies zero or near-zero GHG fuels as the primary lever from the 2030s. E-methanol sits within the category of alternative zero or near-zero GHG fuels alongside green ammonia, green hydrogen, and advanced biofuels. The IMO’s development of lifecycle GHG guidelines for alternative fuels (through MEPC working groups) directly affects how e-methanol’s WTW intensity is computed for MARPOL compliance purposes.

Methanol fuel systems for LNG carriers and tankers

Chemical tankers are considered natural candidates for early methanol adoption because their crews already handle methanol as a cargo under the IBC Code, and the chemical tanker hull form typically provides adequate cargo hold volume to accommodate the larger methanol bunker tanks. Several chemical tanker operators have ordered methanol dual-fuel vessels or conducted feasibility studies for retrofitting existing stainless steel or epoxy-lined tanks to methanol fuel service.

Oil tankers face a more complex conversion path because their cargo tanks are not suitable for methanol fuel storage without lining, and dedicated fuel tank spaces must be identified within the double bottom or wing tank structure. The container ship sector, where Maersk’s programme has been pioneering, benefits from the relative freedom to allocate hold bays to methanol tank inserts without major revenue loss compared to a cargo tank conversion.

Port state control considerations

Methanol-fuelled ships are subject to port state control (PSC) inspections covering both the conventional safety domains (fire safety, lifesaving appliances, structural condition) and the specific requirements for low-flashpoint fuel systems under the IGF Code and MSC.1/Circ.1621. PSC officers from Paris MOU and Tokyo MOU member states are being trained to inspect methanol fuel documentation, gas detection system records, emergency shutdown test logs, and the International Certificate of Fitness for the Carriage of Liquefied Gases in Bulk (if the vessel also carries methanol as cargo). A deficiency in the methanol fuel safety documentation or in maintenance records for gas detection systems is a detainable deficiency under the relevant PSC inspection regime. The port state control framework applies to these inspections in the same way as for LNG and other regulated fuel systems.

EEDI and EEXI implications

Methanol’s lower CO2 emission factor per unit of energy (69.1 g CO2/MJ compared to 77.5 g CO2/MJ for HFO) reduces the attained EEDI and EEXI values for methanol-fuelled newbuilds and existing ships respectively, relative to equivalent HFO-burning vessels of the same hull and engine configuration. For a newbuild container ship at the EEDI Phase 3 requirement level, the reduction in the attained EEDI from switching the reference fuel from HFO to grey methanol is approximately 11%, which in some cases can shift a borderline vessel from non-compliant to compliant without requiring other efficiency measures. For e-methanol, the MARPOL EEDI and EEXI rules as currently written still compute attained values based on tank-to-wake CO2 factors; the lower WTW benefit of e-methanol over grey methanol does not affect EEDI or EEXI directly. The full WTW benefit is captured in CII, FuelEU, and EU ETS accounting.

See also

References

  1. MAN Energy Solutions. ME-LGIM - Methanol Injection, Project Guide. MAN Energy Solutions, Copenhagen, 2022 edition.
  2. IMO. Interim Guidelines for the safety of ships using methyl/ethyl alcohol as fuel. MSC.1/Circ.1621, International Maritime Organization, London, 2020.
  3. IMO. International Code of Safety for Ships Using Gases or Other Low-flashpoint Fuels (IGF Code). Resolution MSC.391(95), International Maritime Organization, London, 2015.
  4. IMO. Fourth IMO GHG Study 2020. MEPC 75/7/15, International Maritime Organization, London, 2020.
  5. ISO. ISO 6583-1:2023 Petroleum and related products - Methanol and ethanol as marine fuels - Part 1: Requirements for bunkering. International Organization for Standardization, Geneva, 2023.
  6. IRENA. Innovation Outlook: Renewable Methanol. International Renewable Energy Agency, Abu Dhabi, 2021.
  7. Carbon Recycling International. George Olah Renewable Methanol Plant operational data, CRI, Iceland, 2021.
  8. IMO. 2023 IMO Strategy on Reduction of GHG Emissions from Ships. Resolution MEPC.377(80), International Maritime Organization, London, 2023.
  9. EU. Regulation (EU) 2023/1805 of the European Parliament and of the Council on the use of renewable and low-carbon fuels in maritime transport (FuelEU Maritime). Official Journal of the European Union, 2023.
  10. IACS. Classification society unified requirements and guidelines for methanol fuel systems, as published by ABS, DNV, and Lloyd’s Register, 2022-2024.
  11. Stena Line / MAN Diesel & Turbo. Stena Germanica methanol conversion project, technical report, 2015.

Further reading

  • Bromberg, L. and W.K. Cheng. Methanol as an alternative transportation fuel in the US: Options for sustainable and/or energy-secure transportation. PSFC/RR-10-12, MIT Plasma Science and Fusion Center, 2010.
  • Methanol Institute. Methanol Use in Shipping. Methanol Institute, Washington DC, updated annually.
  • DNV. Alternative Fuels Insight platform - methanol data and fleet tracking. DNV AS, Hovik, updated quarterly.
  • SEA-LNG. Multi-Criteria Analysis: LNG versus Methanol versus Ammonia in Shipping, comparative pathway study, 2022.
  • Bilgili, L. “A systematic review on the acceptance of alternative marine fuels.” Renewable and Sustainable Energy Reviews, vol. 182, 2023.