Per-fuel well-to-wake intensity: methanol grades

Background: methanol as a marine fuel

Methanol is the simplest alcohol, a single carbon, four hydrogens and one oxygen, with a chemical formula of CH3OH and a molecular weight of 32.04 g/mol. At ambient conditions it is a clear, colourless, water-miscible liquid with a density of approximately 791 kg/m3 at 20 degrees Celsius and a lower heating value of approximately 19.9 MJ/kg. The volumetric energy density of approximately 15.7 GJ/m3 is roughly 45 percent of VLSFO and roughly 30 percent of LNG on the same basis, which sets the bunker-tank size penalty for a methanol-fuelled ship at roughly 2.2 to 2.5 times the equivalent VLSFO tank for the same range. The flash point of approximately 11 degrees Celsius classifies methanol as a low-flashpoint fuel under SOLAS Chapter II-2 and brings it within the scope of the IGF Code Part B and the IMO Interim Guidelines MSC.1/Circ.1621.

The case for methanol as a marine fuel rests on three structural advantages. First, the molecule is liquid at ambient temperature and atmospheric pressure, which removes the cryogenic and pressurised storage burden that drives the capital expenditure for LNG, ammonia and hydrogen fuel systems. Second, the global methanol industry already produces approximately 110 million tonnes per year for chemical, formaldehyde, MTBE and fuel applications, with a deep-water trading infrastructure of roughly 100 large parcel tankers and dozens of bulk import terminals at major bunker hubs. Third, the same molecule can be produced from natural gas, coal, biomass, biomethane, or renewable hydrogen plus captured carbon dioxide, which lets a shipowner stage a transition from fossil to low-carbon supply on a single fuel system.

The case against rests on the WtW intensity question. A methanol-fuelled vessel that bunkers grey methanol from a Trinidad or Saudi Arabian steam-methane reformer is operating at a higher WtW intensity than the same vessel burning VLSFO. The fuel choice only delivers a GHG benefit when the methanol carries a low-carbon production certificate. The four production grades that follow are not interchangeable for compliance, and the price spread between them in 2026 ranges from roughly 350 USD per tonne for grey methanol to roughly 1,400 to 1,800 USD per tonne for certified e-methanol on a methanol-equivalent basis.

The shipboard architecture is unaffected by which grade is bunkered. The pumps, the double-walled fuel-supply piping, the inert-gas blanketing, the leak-detection layout, the engine fuel injectors, the pilot-fuel skid, and the IGF Code safety case are all identical across the four grades, because the molecule is identical. The certificate of analysis, the proof of sustainability, the chain-of-custody document, the FuelEU verifier statement, and the MEPC.391(82) WtT value are different. The compliance value of a tonne of methanol bunker is therefore set by paperwork, not chemistry.

ISO 6583 specifications and ISO 8217:2024 marine methanol grade

The marine industry adopted ISO 6583 as the standalone methanol fuel specification for marine internal combustion engines. The standard, finalised in 2024, defines a quality envelope on purity (minimum 99.85 percent methanol by mass), water content (maximum 0.10 percent by mass), acidity (maximum 0.0030 percent by mass as acetic acid), non-volatile residue (maximum 0.0010 percent by mass), chloride (maximum 0.5 mg/kg as Cl), sulphur (maximum 0.5 mg/kg), and several optical and physical parameters. The specification matches IMPCA methanol reference specification plus marine-specific contaminant caps, which means the methanol that already trades in the global chemical market broadly meets the marine fuel envelope without a separate manufacturing line.

ISO 8217:2024, the umbrella marine fuel specification, was revised to add a methanol grade alongside the conventional residual and distillate categories. The 2024 revision references ISO 6583 for the methanol envelope and adds the bunker delivery note (BDN) requirements, the sampling protocol, and the dispute-resolution chain that the industry already applies to fuel oil. The bunker supplier therefore issues a single document compliant with both ISO 6583 and ISO 8217:2024, and the receiving vessel applies the same fuel-quality verification chain that has been in service since 1987 for residual fuels.

The contaminant envelope matters for engine durability. Chloride at concentrations above the ISO 6583 cap accelerates stress-corrosion cracking in austenitic stainless steel fuel-supply piping, the standard material for low-flashpoint marine fuel systems. Water above the cap promotes microbial growth in storage tanks and corrodes carbon-steel components in upstream supply tanks. Non-volatile residue above the cap fouls injector tips on the dual-fuel engine. The certificate of analysis on every bunker delivery confirms compliance against these caps, and the retained sample is held by the supplier, the receiving vessel, and the verifier for the dispute window.

The specification is grade-agnostic. A grey methanol cargo from Methanex’s Trinidad plant, a blue methanol cargo from a CCS-equipped Norwegian plant, a bio-methanol cargo from Enerkem’s waste-to-methanol plant, and an e-methanol cargo from Orsted’s renewable hydrogen plant all meet the same ISO 6583 envelope at the bunker manifold. The molecule is the same. The lifecycle certificate is what differentiates them.

Grey methanol: natural-gas-reformed pathway

Grey methanol is the conventional production pathway and accounts for approximately 65 percent of global methanol output. The process begins with natural gas, which is steam-reformed at approximately 800 to 1,000 degrees Celsius over a nickel catalyst to produce a synthesis gas of hydrogen, carbon monoxide and carbon dioxide. The synthesis gas is then routed through a methanol synthesis loop, typically a Lurgi or Topsoe reactor design at approximately 250 degrees Celsius and 50 to 100 bar over a copper-zinc-aluminium oxide catalyst, which converts the syngas into raw methanol. Distillation removes water and trace contaminants, delivering chemical-grade or fuel-grade methanol that meets the IMPCA and ISO 6583 envelopes.

The carbon balance is dominated by the natural gas feedstock. Roughly 0.66 to 0.74 tonnes of natural gas (as methane) are consumed per tonne of methanol produced, and the steam-methane reformer vents the remaining carbon as carbon dioxide. Roughly 0.50 to 0.65 tonnes of CO2 are vented from the reformer per tonne of methanol, plus another 0.20 to 0.30 tonnes from the natural gas combusted to provide process heat. The well-to-tank intensity therefore lands in the 27 to 41 gCO2eq/MJ range for the upstream stage. Adding the tank-to-wake CO2 of approximately 69 gCO2eq/MJ from oxidising the methanol carbon at the engine yields a total well-to-wake intensity of 96 to 110 gCO2eq/MJ under MEPC.391(82) Annex 1.

The MEPC.391(82) Annex 1 default for grey methanol from natural gas in non-CCS configuration sits at approximately 102.7 gCO2eq/MJ WtW for the global average, with regional defaults varying based on the natural gas supply chain (US Gulf, Trinidad, Middle East, China) and the reformer thermal efficiency. The FuelEU Annex II default for the same pathway sits at approximately 101.2 gCO2eq/MJ WtW. The two figures differ by sub-2 gCO2eq/MJ because the underlying lifecycle assessments draw on the same reference data with minor methodological differences in upstream methane leakage assumptions.

The compliance implication is direct. A vessel that bunkers grey methanol is not reducing GHG intensity relative to VLSFO. Under FuelEU 2025 with a baseline target of approximately 89.34 gCO2eq/MJ falling to roughly 77.94 gCO2eq/MJ in 2030, grey methanol fails the standard outright and accumulates a compliance deficit on every tonne consumed. The shipowner pays a penalty per the FuelEU schedule, and the methanol fuel switch produces a worse compliance outcome than continuing on conventional residual fuel.

The role of grey methanol in the marine market is therefore transitional. A vessel commissioned in 2026 with a methanol dual-fuel engine can bunker grey methanol while the supply chain for low-carbon grades scales, then progressively shift to bio-methanol and e-methanol as those volumes become available at the relevant ports. The shipowner accepts a near-term compliance penalty in exchange for asset readiness when the certified low-carbon supply arrives. The economic threshold for the transition depends on the spot grey-green spread, the FuelEU penalty schedule, and the volumes contracted under long-term offtake agreements.

Blue methanol: natural gas + CCS pathway

Blue methanol uses the same steam-methane reformer and the same methanol synthesis loop as grey methanol, but routes the carbon dioxide vented from the reformer and the synthesis loop into a carbon-capture unit, compresses it, transports it by pipeline or ship to a geological storage site, and injects it into a depleted gas field or saline aquifer for permanent sequestration. The capture and storage chain typically targets the high-purity CO2 stream from the synthesis-loop purge gas, which can be captured at the lowest cost, and optionally a fraction of the lower-purity stream from the reformer flue gas. Capture rates of 60 to 90 percent of the production-stage CO2 are technically feasible, with 80 percent representing a typical project design point.

The WtT intensity reduction depends on the capture rate, the energy penalty of the capture and compression chain, the storage-site monitoring requirements, and the upstream natural gas methane leakage. A blue methanol plant with 80 percent capture and a low-leakage gas supply (less than 0.5 percent upstream methane loss) reaches a WtT intensity of approximately 8 to 18 gCO2eq/MJ. Adding the TtW CO2 of 69 gCO2eq/MJ yields a WtW intensity in the 77 to 87 gCO2eq/MJ band for high-quality blue methanol, with a typical FuelEU Annex II default in the 80 to 85 gCO2eq/MJ range. Lower-capture-rate or higher-leakage configurations push the WtW intensity above 90 gCO2eq/MJ, at which point the GHG benefit relative to grey methanol erodes.

Several blue methanol projects entered front-end engineering design in the 2024 to 2026 window, including the Northern Lights and Yara joint developments in Norway, the Mitsubishi Gas Chemical and Sumitomo developments in Asia, and several Gulf of Mexico projects tied to the 45Q tax credit and the Clean Hydrogen Production Tax Credit under the US Inflation Reduction Act. The MEPC.391(82) Annex 1 default for natural-gas-with-CCS methanol depends on the project-specific capture rate and is typically certified through a third-party verifier under ISCC or REDcert frameworks, with the certificate naming the capture rate and the storage chain.

The compliance value of blue methanol under FuelEU is intermediate. Better than grey methanol, worse than bio-methanol or e-methanol, and a meaningful but not transformational improvement relative to VLSFO. A blue methanol cargo at 82 gCO2eq/MJ WtW delivers an approximately 11 percent intensity reduction relative to VLSFO, against the FuelEU 2030 trajectory that requires a 14.5 percent reduction. The shipowner therefore needs to blend blue methanol with bio-methanol or e-methanol, or pair it with pooling and balancing credits from a sister vessel, to reach the standard.

The other axis of evaluation is upstream methane leakage. A blue methanol plant that captures 80 percent of production-stage CO2 but draws on a natural gas supply with 2.5 percent upstream methane leakage delivers a worse WtW intensity than a grey methanol plant on a 0.3 percent leakage supply, because the methane leakage term applied at GWP100 of 28 (or GWP20 of 84 in the alternative metric) outweighs the capture benefit. The MEPC.391(82) Annex 1 framework requires the upstream leakage value to be either the certified project-specific figure or a regional default, and the blue methanol marketing claim therefore has to be verified at the certificate level rather than asserted at the project level.

Bio-methanol: biomass gasification + synthesis; biomethane reforming

Bio-methanol is produced through two principal pathways. The first is biomass gasification, which thermochemically converts lignocellulosic biomass (forest residue, agricultural residue, woody biomass, waste wood) into a synthesis gas at 700 to 1,000 degrees Celsius in a controlled-oxygen environment. The synthesis gas is cleaned, conditioned, and routed through the same methanol synthesis loop as grey methanol production. The second is biomethane steam reforming, which takes upgraded biomethane (from anaerobic digestion of organic waste) and processes it through a steam-methane reformer and synthesis loop. Both pathways yield methanol that meets the ISO 6583 envelope and is molecularly indistinguishable from grey methanol.

The WtT intensity is dominated by the feedstock carbon footprint, the conversion efficiency, and the energy inputs to the gasification or reforming chain. Waste-feedstock bio-methanol from biomass gasification typically delivers a WtT intensity of minus 5 to 20 gCO2eq/MJ depending on the feedstock counterfactual (avoided landfill, avoided incineration, avoided field decomposition) and the inclusion of any carbon-capture credits on the synthesis-loop CO2 vent. Manure-based biomethane reformed to bio-methanol can attract a negative WtT value through the same avoided-methane credit recognised for bio-LNG under MEPC.391(82). Adding the TtW CO2 of 69 gCO2eq/MJ (which is biogenic and therefore counts as zero in both MEPC.391(82) and FuelEU Annex II) yields a WtW intensity of 5 to 30 gCO2eq/MJ for the typical waste pathway.

Several bio-methanol projects reached commercial operation by 2026. Enerkem operates a waste-to-methanol plant in Edmonton, Canada. BioMCN operates a biomethane-to-methanol plant in Delfzijl, Netherlands. Sodra and Liquid Wind have advanced developments in Sweden. CRI (Carbon Recycling International) operates a CO2-to-methanol plant in Iceland that uses geothermal hydrogen and captured geothermal CO2, which sits at the boundary between bio-methanol and e-methanol depending on the certification framework. The combined certified bio-methanol production reached approximately 350,000 tonnes per year by mid-2026, against a global methanol market of approximately 110 million tonnes, which means bio-methanol represents roughly 0.3 percent of the methanol pool by volume and competes for premium offtake in the marine, road and chemical-feedstock markets.

The MEPC.391(82) Annex 1 default for bio-methanol depends on the feedstock category. Waste-based bio-methanol carries a default WtW intensity of approximately 15 to 25 gCO2eq/MJ, energy-crop bio-methanol carries a default of approximately 45 to 60 gCO2eq/MJ (subject to the RED III food and feed crop cap), and manure-based pathways can fall below 5 gCO2eq/MJ once the avoided-methane credit is applied. The FuelEU Annex II values track the MEPC.391(82) figures with minor methodological differences.

The compliance value of bio-methanol under FuelEU is high. A waste-feedstock bio-methanol at 20 gCO2eq/MJ WtW delivers an approximately 78 percent intensity reduction relative to VLSFO, which more than meets the 2030 FuelEU target and contributes a substantial compliance surplus that can be banked, pooled, or transferred to sister vessels. The premium pricing reflects this value, with bio-methanol typically trading at a 200 to 400 percent premium to grey methanol on a tonne basis in 2026.

Bio-methanol does not qualify for the FuelEU RFNBO 2x multiplier, because the multiplier is reserved for renewable fuels of non-biological origin. The biological feedstock places bio-methanol in the advanced biofuel category instead, where it is treated at face-value WtW intensity without the multiplier uplift. The distinction is meaningful for compliance arithmetic and is detailed at /wiki/fueleu-rfnbo-multiplier.

E-methanol: renewable H2 + captured CO2 (RFNBO)

E-methanol is the renewable-fuel grade produced from green hydrogen (manufactured by electrolysis of water using renewable electricity) and captured carbon dioxide (from biogenic sources or direct air capture). The two feedstocks are combined in a methanol synthesis loop similar to the conventional pathway, with the difference that both the hydrogen and the carbon atoms originate outside the fossil chain. The product methanol meets the ISO 6583 envelope and is molecularly indistinguishable from grey methanol.

The WtT intensity is driven by three terms: the renewable electricity intensity supplied to the electrolyser, the energy and emissions of the CO2 capture chain, and the additional energy inputs of the synthesis loop. A well-designed e-methanol plant with grid-balanced renewable electricity at less than 18 gCO2eq/kWh, biogenic CO2 from a fermentation or pulp plant, and a modern Lurgi or Topsoe synthesis loop achieves a WtT intensity of approximately 5 to 12 gCO2eq/MJ. Adding the TtW CO2 of 69 gCO2eq/MJ (zero on the FuelEU and MEPC.391(82) basis because the CO2 originated as biogenic or atmospheric carbon, which is treated as a closed loop) yields a WtW intensity of 5 to 12 gCO2eq/MJ for the high-quality biogenic-CO2 pathway. Direct-air-capture CO2 with the same renewable electricity supply lands at approximately 15 to 25 gCO2eq/MJ because of the higher energy penalty of DAC.

The RED III delegated act on RFNBOs sets the conditions for the renewable-electricity input. The electricity must be additional (sourced from a renewable plant commissioned no earlier than 36 months before the electrolyser), temporally correlated (matched on an hourly basis from 2030, monthly until then), and geographically correlated (in the same bidding zone or a neighbouring zone with no congestion). The delegated act also mandates a minimum 70 percent GHG saving versus a fossil comparator of 94 gCO2eq/MJ, which means the certified e-methanol cannot exceed approximately 28.2 gCO2eq/MJ WtW. The MEPC.391(82) Annex 1 framework adopts a similar threshold structure for RFNBO eligibility, although the temporal and additionality criteria are less prescriptive than RED III.

The MEPC.391(82) Annex 1 default for e-methanol depends on the certified electricity intensity and the CO2 source. Biogenic-CO2 e-methanol on certified renewable electricity carries a default WtW intensity of approximately 10 gCO2eq/MJ, and DAC-CO2 e-methanol carries a default of approximately 18 to 22 gCO2eq/MJ. The FuelEU Annex II values track these figures.

E-methanol qualifies for the FuelEU RFNBO 2x multiplier, which doubles the GHG-intensity benefit of an RFNBO bunker for the period 2025 to 2033 inclusive. A vessel that bunkers e-methanol at 10 gCO2eq/MJ WtW receives a compliance credit equivalent to consuming a fuel at approximately minus 70 gCO2eq/MJ relative to the FuelEU baseline, which is an extraordinarily strong compliance lever. The mechanism is detailed at /wiki/fueleu-rfnbo-multiplier and worked through arithmetically at /calculators/fueleu-rfnbo-multiplier.

E-methanol production reached approximately 80,000 tonnes per year of certified output by mid-2026, against the global methanol market of 110 million tonnes. The leading operating projects include Orsted FlagshipONE in Sweden (cancelled 2024), CRI George Olah in Iceland, HIF Haru Oni in Chile, Liquid Wind FlagshipONE in Sweden (relocated post-Orsted exit), and several smaller Power-to-X projects at European wind sites. The price spread to grey methanol stands at roughly 4 to 6 times on a tonne basis in 2026, reflecting the renewable-electricity cost, the small production base, and the policy-driven demand from FuelEU and the IMO net-zero framework.

MEPC.391(82) Annex 1 defaults per grade

The IMO 2023 Guidelines on Lifecycle GHG Intensity of Marine Fuels, adopted as resolution MEPC.391(82) at the 82nd session of the Marine Environment Protection Committee, codify the per-fuel default emission factors that feed the marine GHG fuel standard under the IMO net-zero framework. Annex 1 of the Guidelines provides default WtT, TtW and WtW values for each fuel and pathway, with the methanol grades treated as four distinct lines.

The tabular summary for methanol pathways in Annex 1, reduced to indicative values, is as follows:

The TtW value is reported as 0 for biogenic and atmospheric carbon sources because the carbon released at combustion is treated as a closed loop with the upstream carbon capture (from biomass photosynthesis or from direct atmospheric capture). The methodology is consistent with IPCC inventory rules for biogenic carbon and with the FuelEU Annex II treatment.

The Annex 1 defaults apply when the bunker supplier does not provide a project-specific certified value. A supplier with a third-party certified WtT figure under ISCC, REDcert, or an equivalent scheme can substitute the certified value for the default, and the verifier under the FuelEU and IMO compliance frameworks accepts the certified value subject to mass-balance and chain-of-custody verification.

The methanol-specific Annex 1 entries also include slip and unburned methanol terms. Methanol dual-fuel engines exhibit very low slip (typically less than 0.2 percent of fuel input on the latest MAN ME-LGIM and Wartsila MethanolPac designs), which contributes a marginal addition of approximately 0.3 to 1 gCO2eq/MJ to the WtW total. The slip term is materially smaller than the methane slip on LNG dual-fuel engines covered at /wiki/per-fuel-wtw-lng-otto-diesel, where high-pressure dual-fuel engines incur 0.2 to 0.5 percent slip and low-pressure dual-fuel engines incur 1.5 to 3.5 percent slip.

FuelEU Annex II treatment

The FuelEU Maritime regulation, Regulation (EU) 2023/1805, takes effect for ships above 5,000 GT calling at EU and EEA ports from 1 January 2025. The regulation imposes a declining limit on the fleet-average WtW GHG intensity of energy used on board, starting at approximately 89.34 gCO2eq/MJ in 2025 (a 2 percent reduction relative to the 2020 baseline of 91.16 gCO2eq/MJ) and tightening to 77.94 gCO2eq/MJ in 2030, 62.9 gCO2eq/MJ in 2035, 39.0 gCO2eq/MJ in 2040, 26.6 gCO2eq/MJ in 2045, and 18.2 gCO2eq/MJ in 2050.

Annex II of the regulation provides default WtW emission factors for each fuel and production pathway. The methanol entries in Annex II mirror the MEPC.391(82) Annex 1 structure with minor numerical differences:

The Annex II defaults are adjusted by the company through a verifier-approved certificate where a project-specific WtT value is documented. The certificate must be issued by a recognised voluntary scheme (ISCC EU, REDcert, 2BSvs, or equivalent), must trace the feedstock through the supply chain on a mass-balance basis, and must conform to RED III sustainability criteria for bio-methanol or RED III RFNBO criteria for e-methanol.

The compliance arithmetic combines Annex II defaults across the bunker mix, applies the RFNBO multiplier where eligible, and produces the fleet-attained GHG intensity that is compared to the year’s limit. A surplus is banked, pooled, or transferred. A deficit triggers the FuelEU penalty per /wiki/fueleu-penalties-pooling-multipliers, set at 2,400 EUR per tonne of VLSFO-equivalent energy required to close the gap, increased by 10 percent per consecutive year of non-compliance. The penalty is structurally larger than the spot premium of bio-methanol or e-methanol once the multiplier is applied, which explains the policy-driven demand for low-carbon methanol grades from 2025 onwards.

RED III sustainability criteria for bio/e-methanol

The Renewable Energy Directive Recast III (Directive (EU) 2023/2413, RED III), adopted in October 2023, sets the sustainability and GHG-saving criteria that determine whether a bio-methanol or e-methanol cargo qualifies for FuelEU Annex II treatment as a renewable fuel.

The bio-methanol criteria require:

• GHG saving of at least 65 percent versus the fossil comparator of 94 gCO2eq/MJ for installations operating from 1 January 2021 onwards. This caps certified bio-methanol WtW intensity at approximately 32.9 gCO2eq/MJ.
• No-go area exclusion, prohibiting feedstock from primary forest, peatland, wetland or land with high biodiversity value as defined in the directive.
• Land-use change accounting, applying the indirect land-use change (ILUC) factor for crops grown on agricultural land that displaces other agricultural production.
• Annex IX feedstock list for the most favourable advanced-biofuel treatment. Annex IX-A includes wastes, residues and lignocellulosic feedstocks; Annex IX-B includes used cooking oil and animal fats. Annex IX-A bio-methanol contributes to the advanced-biofuel sub-target without volume cap.
• Food and feed crop cap of 7 percent of the renewable transport target by member state, limiting energy-crop bio-methanol contribution.

The e-methanol (RFNBO) criteria, set by the RED III delegated act on renewable hydrogen (Commission Delegated Regulation (EU) 2023/1184), require:

• 70 percent GHG saving versus the fossil comparator of 94 gCO2eq/MJ. This caps certified e-methanol WtW intensity at approximately 28.2 gCO2eq/MJ.
• Additionality of the renewable electricity supply, sourced from a renewable plant that came into operation no earlier than 36 months before the electrolyser. A grandfathering window applies until 2028 for plants in operation before 2028.
• Temporal correlation, matching electrolyser hourly consumption to renewable plant hourly production from 1 January 2030. A monthly correlation rule applies in the transition period.
• Geographical correlation, sourcing the electricity from the same bidding zone or a neighbouring zone without grid congestion.
• Captured CO2 source restrictions: biogenic CO2 from sustainable biomass, atmospheric CO2 from direct air capture, and (until 2036, with phase-out) industrial CO2 from sectors covered by the EU Emissions Trading System.

The certification chain runs from the electricity supplier or biomass supplier through the methanol producer, the bunker supplier, and the verifier. Each step carries a Proof of Sustainability (PoS) or Proof of Compliance (PoC) document under one of the recognised voluntary schemes (ISCC EU, REDcert EU, 2BSvs, or equivalent). The mass-balance accounting allows the renewable molecules to be commingled with conventional methanol in storage and transport infrastructure provided the certified volumes are tracked by document rather than by physical segregation.

RFNBO 2x multiplier eligibility (brief, cross-link)

E-methanol that satisfies the RED III RFNBO criteria qualifies for the FuelEU Maritime 2x multiplier under Article 5(7) of Regulation (EU) 2023/1805. The multiplier doubles the contribution of the RFNBO bunker to the GHG-intensity calculation for the period from 1 January 2025 through 31 December 2033 inclusive. The mechanism is designed to accelerate RFNBO uptake during the supply-ramp phase by amplifying the compliance value of an early-mover bunker.

Bio-methanol does not qualify for the multiplier. The multiplier is reserved for renewable fuels of non-biological origin, which excludes biological feedstocks. A bio-methanol bunker is treated at face-value WtW intensity in the FuelEU calculation and contributes its full lifecycle benefit but without the 2x amplification.

The arithmetic, the eligibility rules, the temporal and geographical correlation requirements, and the worked examples are at /wiki/fueleu-rfnbo-multiplier. The calculator at /calculators/fueleu-rfnbo-multiplier sizes the multiplier impact for a representative bunker mix, and /calculators/fueleu-rfnbo-double-count handles the double-counting interaction with the RED III road-transport target.

Dual-fuel engine landscape: MAN ME-LGIM, Wartsila MethanolPac, Caterpillar

The methanol-fuelled fleet in 2026 runs on three principal engine families, all of which accept the same ISO 6583 methanol regardless of grade and all of which require a small pilot-fuel injection to initiate compression ignition.

MAN Energy Solutions ME-LGIM is the dominant two-stroke methanol dual-fuel engine. The ME-LGIM is a Diesel-cycle engine derived from the ME-C two-stroke base platform with a high-pressure liquid methanol injection system replacing the heavy fuel-oil injectors. Methanol is injected at approximately 600 to 800 bar at the appropriate point in the compression stroke, atomises into the cylinder, and is ignited by a co-injected pilot fuel (typically 5 to 10 percent of total fuel energy on a marine gas oil basis). The Diesel cycle preserves combustion phasing similar to fuel-oil operation, and the methanol slip is very low (typically less than 0.2 percent of fuel input). The ME-LGIM platform powers the Maersk methanol-fuelled container ship series (Laura Maersk and the 16 follow-on vessels), as well as a growing fleet of methanol-fuelled bulkers, tankers and car carriers commissioned from 2024 onwards. The engine size range covers 4S50ME-LGIM (small-bore) through 7S95ME-LGIM (very-large-bore for ULCS class).

Wartsila MethanolPac is the four-stroke methanol dual-fuel engine family for medium-speed propulsion and auxiliary applications. The MethanolPac is based on the Wartsila 32M and 46M four-stroke platforms with a methanol fuel-supply skid, low-pressure methanol injection, and a pilot-fuel injection system. The four-stroke architecture suits ferries, ro-ro vessels, supply vessels, and auxiliary generators. Methanol slip is similarly low to the ME-LGIM, with the four-stroke platform offering the operational flexibility of fuel-mode switching between methanol and conventional distillate within seconds. Stena Germanica was the prototype installation in 2015, and the platform expanded to a multi-vessel commercial fleet by 2026.

Caterpillar 3500 series entered the methanol dual-fuel market with the 3500E platform, targeted at medium-speed marine and stationary applications. The Caterpillar offering uses a port-injection methanol system with diesel pilot injection, suiting tugs, OSVs, and smaller commercial vessels. The platform reached commercial release in 2025.

Other entrants include the WinGD X-DF-M two-stroke methanol engine (commercial release 2024), the Hyundai Heavy Industries HiMSEN methanol four-stroke, and the J-ENG UE-LSGiM two-stroke methanol engine. The dual-fuel landscape is detailed at /wiki/methanol-marine-engines-overview.

The unified characteristic across all engine families is that methanol is a compression-ignition fuel with a pilot requirement rather than a spark-ignition fuel like LNG in an Otto-cycle dual-fuel engine. The pilot fuel is conventionally marine gas oil at 5 to 10 percent of fuel energy, which means a methanol-fuelled vessel always carries a residual MGO bunker and incurs the WtW intensity of that pilot stream against the total fuel mix. The pilot contribution to the total WtW intensity is reduced as bio-MGO or HVO renewable diesel becomes available as a low-carbon pilot, which is an active area of development for the 2027 to 2030 horizon.

Bunkering supply chain

The methanol bunkering supply chain in 2026 covers a small number of established hubs with reliable supply and a growing network of pilot and demonstration sites. The supply chain depends on the grade.

Grey methanol bunkering operates at chemical-import terminals worldwide. Methanex Corporation, the largest single producer with capacity of approximately 9 million tonnes per year across plants in Trinidad, Chile, New Zealand, Egypt and the United States, supplies the marine market through the Waterfront Shipping subsidiary, which operates a fleet of approximately 30 chemical tankers and offers methanol bunker delivery in major ports. Proman (formerly OCI Methanol Group), the second-largest producer with capacity of approximately 7 million tonnes per year, supplies the European and Caribbean markets through dedicated bunker barges. The bunker price for grey methanol in Singapore, Rotterdam and Houston in 2026 ranged from approximately 350 to 450 USD per tonne on a methanol basis, equivalent to approximately 700 to 900 USD per tonne on a VLSFO-energy-equivalent basis.

Blue and bio-methanol bunkering is concentrated at specific supply nodes. BioMCN and OCI Methanol supply bio-methanol at Rotterdam through certificates of origin under ISCC EU. Methanex supplies bio-methanol at the US Gulf Coast through certified offtake agreements with biomethane suppliers. CRI delivers low-carbon methanol from Iceland to European ports.

E-methanol bunkering is currently limited to a handful of sites. HIF Haru Oni in Chile supplies certified e-methanol to South American and Pacific routes. Liquid Wind delivers e-methanol from Swedish sites to Northern European bunker barges. CRI George Olah in Iceland delivers low-carbon methanol that can carry an RFNBO certificate depending on the electricity origin attribution.

Stena operates one of the most established marine methanol bunkering operations through Gothenburg, originally serving Stena Germanica from 2015 and expanding to third-party bunker delivery for visiting methanol-fuelled vessels. Yangtze River bunkering is a growing East Asian hub, with Singapore, Shanghai and Ningbo having delivered methanol bunkers to commercial vessels from 2024. The Singapore Maritime and Port Authority issued the technical reference for ship-to-ship methanol bunkering in 2023, and the first commercial STS methanol bunker took place in 2023 with Maersk and Hong Lam Marine.

The supply chain bottleneck is the certified low-carbon methanol volume. Total certified bio-methanol and e-methanol production reached approximately 430,000 tonnes in 2026 against a marine methanol demand of approximately 1.2 million tonnes (driven by the 30+ Maersk vessels and the growing methanol-fuelled fleet). The shortage is filled by grey methanol, with shipowners accepting near-term FuelEU penalties and progressively converting volumes to certified bio-methanol or e-methanol as supply expands.

Pilot fuel requirements

The compression-ignition combustion of methanol in a marine dual-fuel engine requires a small fraction of pilot fuel to initiate ignition, because methanol’s auto-ignition temperature of approximately 470 degrees Celsius is too high to ignite reliably from compression alone in a marine-bore cylinder. The pilot fuel is conventionally marine gas oil (DMA grade), injected through a separate pilot-fuel injector at top dead centre, atomising and igniting before the main methanol injection. The pilot fraction ranges from approximately 3 percent of fuel energy on the latest MAN ME-LGIM designs to approximately 10 percent on older or smaller-bore engines, with 5 percent representing a typical operating point.

The pilot contribution to the total WtW intensity is calculated by energy-weighted averaging of the methanol stream and the pilot stream. For a typical operating point with 95 percent methanol energy and 5 percent MGO pilot energy, where the methanol is e-methanol at 10 gCO2eq/MJ and the MGO pilot is conventional at 91.2 gCO2eq/MJ, the blended WtW intensity is approximately:

The pilot adds approximately 4 gCO2eq/MJ to the e-methanol baseline, which is meaningful for a fuel that targets sub-15 gCO2eq/MJ overall. The same arithmetic applied to grey methanol with MGO pilot yields approximately 102 gCO2eq/MJ for the mix, where the pilot contribution is negligible because both streams are fossil.

The pilot fuel supply is subject to the same certification requirements as the main fuel. A vessel claiming an e-methanol RFNBO compliance benefit must document the pilot-fuel WtW intensity against the FuelEU Annex II default for the pilot stream, which is the conventional MGO default unless the vessel bunkers certified bio-MGO or HVO renewable diesel as the pilot. The substitution of conventional MGO pilot with HVO or bio-MGO pilot is an active development area for the 2027 to 2030 horizon and offers a 4 to 5 gCO2eq/MJ improvement on the blended intensity for a typical pilot fraction.

The pilot injection system is a separate subsystem on the engine, with its own injector pump, supply line, and fuel-quality envelope. The pilot quantity is controlled by the engine management system and adjusts dynamically with load to maintain combustion stability across the operating envelope.

Toxicity and safety: IGF Code Part B / MSC.1/Circ.1621

Methanol is a toxic, low-flashpoint, water-miscible liquid. Acute oral exposure of 25 to 100 mL is potentially lethal for an adult human, with the toxicity mediated by hepatic metabolism to formaldehyde and formic acid. Chronic inhalation exposure causes optic nerve damage and central nervous system effects. Skin absorption is rapid. The toxicity profile is materially worse than conventional fuel oil and requires a stronger crew protection envelope than the IGF Code provisions for LNG.

The IMO regulatory framework for methanol-fuelled ships is provided by the IGF Code (International Code of Safety for Ships using Gases or other Low-flashpoint Fuels) Part B, supplemented by the Interim Guidelines on the safety of ships using methyl/ethyl alcohol as fuel issued as MSC.1/Circ.1621 in 2020. The Interim Guidelines apply pending the formal incorporation of methanol-specific provisions into the IGF Code, which is on the IMO Maritime Safety Committee work programme.

The principal safety provisions are:

• Double-walled fuel piping with leak detection and inert-gas blanketing in the annular space, identical in concept to the LNG IGF Code provisions.
• Hazardous-area classification consistent with IEC 60079 standards for flammable liquid handling, with electrical equipment certified for the relevant zone.
• Inert-gas system for the bunker tank, fuel-supply piping and engine fuel-room, typically nitrogen, to prevent flammable atmospheres in the headspace.
• Tank vent treatment with thermal oxidation, scrubbing or remote venting to a safe location, because methanol vapour at the saturated concentration in the tank headspace is within the flammable range.
• Crew personal protective equipment including dedicated chemical-resistant gloves, eye protection, and respiratory protection during bunker operations and tank entry.
• Bunker delivery procedures with closed-loop vapour return, closed-loop sampling, and emergency shutdown circuits at both the supplier and receiver sides.
• Fire-fighting based on alcohol-resistant aqueous-film-forming foam (AR-AFFF) rather than the conventional protein or fluoroprotein foam used for hydrocarbon fires, because methanol’s water-miscibility breaks down conventional foam blankets.

The methanol flame is invisible in daylight, which is a significant operational consideration. A methanol pool fire produces a pale-blue flame with very low radiant heat, and a crew member can walk into the flame envelope without visual warning. Fire-detection systems on methanol-fuelled vessels rely on infrared and ultraviolet detectors with broadband response, complemented by gas-detection arrays in the bunker manifold area, the engine fuel-room, and the cargo control station.

The bunker delivery operation is similar in workflow to a conventional fuel-oil bunker but uses dedicated methanol-rated piping, vapour-return connections, and inert-gas blanketing. The delivering bunker barge or shore terminal must be equipped for methanol service, which currently restricts methanol bunkering to specific approved locations in each major port. The Singapore MPA, the Rotterdam Port Authority, the US Coast Guard, and the IACS classification societies have issued port-specific or class-specific procedural guidance that supplements the IMO framework.

Formula, assumptions, and limits

Formula

The well-to-wake intensity of a methanol grade in MEPC.391(82) and FuelEU Annex II accounting takes the form:

where g indexes the production grade (grey, blue, bio, e-methanol), EF_WtT,g is the well-to-tank intensity for that grade as certified or as the Annex 1/Annex II default, EF_TtW,CO2 is the tank-to-wake CO2 from oxidising the methanol carbon (69 gCO2eq/MJ for fossil grades, 0 for biogenic and atmospheric-loop grades), and the slip terms cover unburned methanol, formaldehyde and CO emissions at the engine exhaust (typically below 1 gCO2eq/MJ for modern dual-fuel engines).

For a blend of grey and certified-green methanol, the blended WtW intensity is:

where x_green is the energy fraction of certified green-grade methanol (bio-methanol or e-methanol) in the bunker mix.

The pilot-fuel adjustment for the engine-side energy mix is:

where p is the pilot energy fraction (typically 0.03 to 0.10).

Derivation

The WtT term aggregates upstream emissions from feedstock extraction or sourcing, feedstock transport, methanol synthesis (reformer or electrolyser plus synthesis loop), product transport to the bunker terminal, and bunker delivery. Each step is quantified in gCO2eq per MJ of methanol delivered to the ship’s manifold, and the values are summed.

The TtW term for fossil methanol is derived from the carbon stoichiometry. Methanol (CH3OH, molecular weight 32.04) contains 12.01 g of carbon per 32.04 g of fuel, oxidising to 44.01 g of CO2 per mol, or 1.374 g of CO2 per g of methanol. With a lower heating value of 19.9 MJ/kg, the TtW CO2 emission factor is 1.374 / 19.9 x 1000 = 69.05 gCO2eq/MJ.

The TtW term for biogenic and atmospheric-loop methanol is set to zero because the carbon released at the engine was captured upstream from biomass photosynthesis or direct air capture, and the lifecycle accounting closes the loop at the photosynthesis or atmospheric-capture step.

The slip term covers the small fraction of methanol that passes through the engine unburned, plus partial-oxidation products (formaldehyde, CO) that contribute a non-CO2 GWP. Modern MAN ME-LGIM and Wartsila MethanolPac engines exhibit slip below 0.2 percent of fuel input, which yields a slip emission factor below 1 gCO2eq/MJ on a GWP100 basis.

Assumptions

The framework assumes:

• The bunker certificate accurately documents the production pathway and the WtT intensity.
• The mass-balance accounting under ISCC EU, REDcert or equivalent is implemented with full chain-of-custody traceability.
• The engine slip behaviour conforms to the type-test certified value, which is verified in service through periodic emission-monitoring requirements.
• The pilot-fuel stream is documented separately and contributes its own WtW intensity to the energy-weighted average.
• The biogenic carbon balance is closed at the photosynthesis or atmospheric-capture step, consistent with IPCC inventory rules and FuelEU Annex II treatment.

Worked example

A vessel bunkers 1,000 tonnes of certified e-methanol at a WtW intensity of 10 gCO2eq/MJ, with a 5 percent MGO pilot at the conventional MGO Annex II default of 91.2 gCO2eq/MJ. The blended engine-side WtW intensity is:

The vessel’s compliance value under FuelEU 2026 with a target of approximately 88.0 gCO2eq/MJ is 88.0 minus 14.06 = 73.94 gCO2eq/MJ of surplus per MJ of fuel consumed. With the RFNBO 2x multiplier applied to the e-methanol fraction, the effective surplus rises further for the methanol portion of the bunker. The arithmetic is detailed at /calculators/fueleu-rfnbo-multiplier.

A grey-methanol counterfactual at 102 gCO2eq/MJ with the same 5 percent MGO pilot yields a blended intensity of approximately 102.5 gCO2eq/MJ, which is in deficit by approximately 14.5 gCO2eq/MJ versus the 2026 target. The deficit triggers the FuelEU penalty mechanism per /wiki/fueleu-penalties-pooling-multipliers.

Edge cases and limits

• Negative-WtT bio-methanol from manure feedstock can produce a WtW intensity below zero in the FuelEU calculation, which is mathematically permitted and contributes a strong compliance surplus. The certificate must explicitly document the avoided-methane credit, and the verifier must accept the credit under the recognised voluntary scheme.
• DAC e-methanol carries a higher WtT intensity than biogenic-CO2 e-methanol because of the energy penalty of direct air capture. The 70 percent GHG-saving threshold under RED III applies independently of the CO2 source, and DAC e-methanol must still meet the cap.
• Industrial-CO2 e-methanol uses CO2 captured from industrial point sources covered by the EU ETS. The grandfathering rule under RED III allows industrial CO2 to qualify until 2036, after which only biogenic and DAC sources are eligible. The phase-out is staged through delegated acts.
• Pilot fuel stream: a vessel that bunkers e-methanol but uses conventional MGO as pilot retains the fossil pilot intensity on the energy-weighted average. The transition to bio-MGO or HVO pilot fuel is the next decarbonisation step beyond the main fuel switch.
• Mass-balance versus book-and-claim: bio-methanol and e-methanol certification under RED III follows mass-balance, which requires physical chain of custody through commingled storage and transport. Book-and-claim allocation, where a renewable molecule is bunkered remotely and the claim is transferred via certificate to a different physical bunker, is not currently accepted under FuelEU Annex II. The treatment may evolve in subsequent regulatory revisions.

Regulatory basis

• IMO MEPC.391(82), 2023 Guidelines on Lifecycle GHG Intensity of Marine Fuels (LCA Guidelines), Annex 1 default emission factors per fuel and pathway.
• Regulation (EU) 2023/1805 (FuelEU Maritime), Annex II default WtW emission factors and Article 5(7) RFNBO multiplier.
• Directive (EU) 2023/2413 (RED III), sustainability and GHG-saving criteria for advanced biofuels and RFNBOs.
• Commission Delegated Regulation (EU) 2023/1184 (RFNBO additionality, temporal and geographical correlation rules).
• Commission Delegated Regulation (EU) 2023/1185 (RFNBO GHG calculation methodology).
• ISO 6583 (methanol fuel specification for marine internal combustion engines).
• ISO 8217:2024 (marine fuels specification, methanol grade).
• IMO IGF Code Part B and MSC.1/Circ.1621 (interim safety guidelines for methanol-fuelled ships).

Common errors

• Treating all methanol as a single fuel category. The four grades have WtW intensities ranging across more than two orders of magnitude, and the FuelEU compliance outcome differs accordingly.
• Applying the RFNBO 2x multiplier to bio-methanol. Bio-methanol does not qualify; only e-methanol with full RED III RFNBO certification does.
• Omitting the pilot-fuel contribution from the WtW calculation. The 5 to 10 percent MGO pilot adds 4 to 9 gCO2eq/MJ to the engine-side blended intensity.
• Counting biogenic CO2 from combustion as a positive emission. Both MEPC.391(82) and FuelEU Annex II treat biogenic combustion CO2 as zero on the lifecycle ledger.
• Conflating the IMPCA chemical methanol specification with ISO 6583 marine methanol. The ISO 6583 envelope is tighter on chloride, water and contaminant caps to protect marine fuel-system materials.
• Assuming book-and-claim allocation is accepted under FuelEU Annex II. The current rule requires mass-balance with physical chain of custody.
• Using the GWP20 methane factor of 84 instead of GWP100 of 28 for upstream methane leakage in the WtT calculation. Both MEPC.391(82) and FuelEU Annex II use GWP100.

See also

• /wiki/methanol-as-marine-fuel
• /wiki/methanol-marine-engines-overview
• /wiki/fueleu-intensity-formula-breakdown
• /wiki/fueleu-rfnbo-multiplier
• /wiki/marine-gfs-methodology
• /wiki/imo-net-zero-framework
• /wiki/per-fuel-wtw-vlsfo-mgo
• /wiki/per-fuel-wtw-lng-otto-diesel
• /wiki/per-fuel-wtw-bio-lng
• /calculators/fuel-wtw-methanol
• /calculators/fuel-wtw-blend
• /calculators/fueleu-rfnbo-multiplier
• /calculators/fueleu-rfnbo-double-count
• /calculators/fueleu-ghg-intensity
• /calculators/gfi-attained

Related calculators

• e-Diesel / FT e-Fuel - Well-to-Wake
• VLSFO - Well-to-Wake
• LPG - Well-to-Wake
• LNG - Well-to-Wake by engine pathway
• HFO - Well-to-Wake
• MGO / MDO - Well-to-Wake
• Hydrogen - Well-to-Wake by pathway
• HVO / Renewable Diesel - Well-to-Wake

Related formulas

• fuel wtw methanol
• fuel wtw vlsfo
• fuel wtw nuclear
• fuel wtw mgo
• fuel wtw lpg
• fuel wtw lng
• fuel wtw hydrogen
• fuel wtw hvo