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Alcohol Fuels 101

Understanding Methanol and Ethanol as Marine Fuels

Methanol and ethanol are liquid alcohol fuels that can help reduce greenhouse gas emissions from shipping. Both are recognised under the IMO’s interim guidelines for methyl and ethyl alcohol fuels and are gaining attention as practical pathways for maritime decarbonisation. The fuels can be used independently or, in some applications, as blends.

Methanol and Ethanol: Shared Characteristics

CH₃OH

METHANOL

One carbon atom

Fossil, Biomass, Synthetic

C₂H₅OH

ETHANOL

Two carbon atoms

Biomass, Synthetic

What  They Share

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Simple alcohols​ 

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Low flashpoint fuels 

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Liquid at ambient conditions​ 

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Almost none sulphur content 

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Fully miscible, any proportion 

One IMO safety framework for both alcohols 

MSC.1/Circ.1621: interim guidelines for the safety of ships using methyl or ethyl alcohol as fuel 

Download the Guidelines

Why Industry is Interested 

Methanol currently leads market adoption at sea: 431 methanol-capable vessels are in service or on order today (108 in the fleet, 323 on order), with the fleet projected to reach approximately 1,200 vessels by 2030, consuming an estimated 24 million tonnes of methanol per year. 

Ethanol is earlier on the same curve (see Deployment & Bunkering Trials below) backed by a global ethanol production base of over 118 billion litres a year, giving it substantial room to scale as marine-grade supply, standards and engines mature. 

1,114 

Methanol / ethanol retrofit-ready vessels 

293 in the fleet (0.3%)
+
821 on order (10.5% of the order book) 

431

Methanol-capable vessels 

108 in the fleet (0.1% of world fleet)
+
323 on order (4.1% of the order book) 

PROJECTION 

~1,200 methanol-capable vessels by 2030 

Consuming an estimated 24 million tonnes/year of methanol at scale 

No vessels are ordered or classed for ethanol yet –

it's already running in trials aboard methanol dual-fuel ships, with the same multi-fuel engines poised to help it follow fast. 

Aspect : Energy density
Methanol: ~19.9 MJ/kg 
Ethanol: ~26.8 MJ/kg 

Aspect : Flash point 
Methanol: ~11°C – low-flashpoint fuel (IGF Code) 
Ethanol: ~13°C – low-flashpoint fuel (IGF Code) 

Aspect : Toxicity (CLP) 

Methanol: ~Toxic – H301 / H311 / H331 

Ethanol: ~Not classified as toxic 

Aspect : Flame visibility 

Methanol: ~Nearly invisible, pale blue flame 

Ethanol: ~Visible orange flame 

Aspect : Hygroscopic nature 

Methanol: ~High  

Ethanol: ~Moderate 

Aspect : Storage corrosiveness 

Methanol: ~Higher risk (aluminium & copper) 

Ethanol: ~Lower, but still present 

Aspect : Standard / engines 

Methanol: ~ISO 6583:2024 published; engines commercial since ~2016 

Ethanol: ~ISO standard in development; multi-fuel methanol/ethanol engines commercially available since 2025 

Comparison Table 

Aspect 
Methanol
Ethanol 

Energy density 

Flash point 

Toxicity (CLP) 

Flame visibility 

Hygroscopic nature 

Storage corrosiveness 

Standard / engines 

~19.9 MJ/kg 

11°C – low-flashpoint fuel (IGF Code) 

Toxic – H301 / H311 / H331 

Nearly invisible, pale blue flame 

High 

Higher risk (aluminium & copper) 

ISO 6583:2024 published; engines commercial since ~2016 

~26.8 MJ/kg 

13°C – low-flashpoint fuel (IGF Code) 

Not classified as toxic 

Visible orange flame 

Moderate 

Lower, but still present 

ISO standard in development; multi-fuel methanol/ethanol engines commercially available since 2025 

Deployment & Bunkering Trials 

Recent ethanol bunkering and vessel trials have taken place in Denmark, Rotterdam, Barcelona and Santos, providing operational experience and helping demonstrate ethanol's potential in marine applications. 

DENMARK 

LAURA MAERSK 

First ethanol trials on a methanol dual fuel feeder vessel: 10% ethanol with 90% e-methanol, then a 50/50 blend, then operation on 100% ethanol.​ 

DENMARK 

LAURA MAERSK 

First ethanol trials on a methanol dual fuel feeder vessel: 10% ethanol with 90% e-methanol, then a 50/50 blend, then operation on 100% ethanol.​ 

DENMARK 

LAURA MAERSK 

First ethanol trials on a methanol dual fuel feeder vessel: 10% ethanol with 90% e-methanol, then a 50/50 blend, then operation on 100% ethanol.​ 

DENMARK 

LAURA MAERSK 

First ethanol trials on a methanol dual fuel feeder vessel: 10% ethanol with 90% e-methanol, then a 50/50 blend, then operation on 100% ethanol.​ 

Reports & White Papers 

DUT Testing on Methanol and Ethanol Marine Fuel Applications 

GCGF commissioned Dalian University of Technology (DUT) to evaluate methanol, ethanol, and blended alcohol fuels in a diesel-ignited two-stroke marine engine. Testing confirmed that both fuels can be used safely and effectively, with no abnormal combustion behaviour. The study also found that methanol and ethanol are fully compatible as blended fuels and deliver comparable thermal efficiency. Results were consistent with published Wärtsilä engine studies, providing independent validation from both Eastern and Western research sources 

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Bureau Veritas & GCGF Market Study: Ethanol as a Marine Fuel 

An independent market study assessing ethanol's viability as a marine fuel – covering global production and supply (118.2 billion litres produced globally in 2024), safety and environmental characteristics, compatibility with existing methanol infrastructure and engine technology, and regulatory compliance under the IMO IGF Code, MSC.1/Circ.1621, and Bureau Veritas's new NR670 classification rules for methanol- and ethanol-fuelled ships.

GCGF & Roland Berger Study: Sustainable Bioethanol in the US

The US is the world's largest corn producer, driving over 52% of global bioethanol output, with more than 190 biorefineries providing over 17 billion gallons of installed annual capacity. Supply potential is projected to reach 18.3–23.6 billion gallons by 2035, and surplus capacity opens frontiers beyond road transport - including export growth and ethanol-to-jet SAF and marine fuel pathways. 

Download the whitepaper Full
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GCGF & Roland Berger Study: Sustainable Bioethanol in Brazil  

Brazil is the world's largest sugarcane ethanol producer (677 million tonnes, 2024/25 season) and the third-largest corn producer globally, with 332 ethanol plants and ~47.8 billion litres/year of capacity. Supply potential is projected to reach 54.5–68.6 billion litres by 2035 as second-crop (safrinha) corn expands. 

Download the whitepaper Full

FAQ

  • Ethanol is gaining attention as a marine fuel due to its potential to reduce greenhouse gas emissions, its production from renewable sources, and its compatibility with existing engine technologies. It can be produced renewably from biomass, industrial waste, or captured carbon dioxide, contributing to the decarbonization goals set by the International Maritime Organization (IMO). Unlike LNG, ethanol doesn’t result in methane slip and has lower sulfur content, making it an environmentally sound alternative.​ 

     

    References: 

    DNV, "Alternative fuels: the options", https://www.dnv.com/expert-story/maritime-impact/alternative-fuels/ 

    IEA, "Renewables 2023", https://www.iea.org/reports/renewables-2023 

  • Ethanol is a renewable fuel made from biomass or sugars. It offers lower lifecycle CO₂ emissions, especially with sustainable feedstocks. Its high octane improves combustion and engine efficiency. Ethanol is compatible with existing fuel infrastructure (with modifications) and has a higher flash point than methanol, improving safety. It also produces very low SOx and particulates, aiding ECA compliance.. 

     

    References: 

    IEA, "Transport Biofuels – Renewables 2023," https://www.iea.org/reports/renewables-2023/transport-biofuels 

    Argonne National Laboratory, "Summary of Expansions and Updates in GREET® 2023," https://greet.anl.gov/files/greet-2023-summary 

    European Commission, "Biofuels – Energy," https://energy.ec.europa.eu/topics/renewable-energy/bioenergy/biofuels_en 

  • Ethanol poses several technical hurdles for marine applications: 

    • Lower Energy Density (~15.6 MJ/L) requires larger fuel storage for equivalent range. 

    • Material Compatibility issues – ethanol can corrode certain metals and degrade rubber/plastic components. 

    • Water Affinity – being hygroscopic, it absorbs moisture, risking phase separation and corrosion. 

    • Flammability – though safer than methanol, ethanol still needs strict fire safety protocols. 

     

    These issues require proper tank design, material selection, and enhanced fuel handling systems. 

     

    References: 

    Bell Performance, "Ethanol Fuel Problems," https://www.bellperformance.com/ethanol-problems​Bell Performance 

    Galati Yacht Sales, "Why You Should Avoid Ethanol Fuel in Boats," https://www.galatiyachts.com/yachting-news/disadvantages-of-ethanol-fuel-and-additives/​Galati Yachts 

    Oak Ridge National Laboratory, "Technical Issues Associated with the Use of Intermediate Ethanol Blends," https://info.ornl.gov/sites/publications/files/Pub7767.pdf​ORNL Info 

  • Ethanol and methanol are both viable marine fuels, but differ in several ways: 

    • Energy Density: Ethanol (~26.8 MJ/kg) is higher than methanol (~19.9 MJ/kg), offering better range or less storage need. 

    • Flash Point: Ethanol (~13°C) is slightly safer than methanol (~11°C) under normal conditions. 

    • Material Compatibility: Ethanol tends to be less corrosive and more compatible with fuel system materials. 

    • Toxicity: Ethanol is less toxic, reducing health risks for crew. 

     

    However, methanol is more commercially mature, with established use, regulations, and more vessels already running on it. Ethanol can benefit from this existing framework to accelerate adoption. 

     

    References: 

    DNV, "Alternative fuels: the options", https://www.dnv.com/expert-story/maritime-impact/alternative-fuels/ 

    Methanol Institute, "Methanol as a Marine Fuel", https://www.methanol.org/wp-content/uploads/2020/01/Methanol-as-a-marine-fuel-january-2020.pdf 

    IEA, "Technology Roadmap: Biofuels for Transport", https://www.iea.org/reports/technology-roadmap-biofuels-for-transport 

  • Using ethanol as marine fuel requires strict safety protocols to manage its flammability, water absorption, and corrosive tendencies: 

    • Closed Bunkering Systems to prevent vapor release. 

    • Vapor Management Systems to control flammable ethanol-air mixtures. 

    • ATEX-Certified Equipment for use in potentially explosive vapor zones. 

    • Corrosion-Resistant Materials like stainless steel for tanks and piping. 

    • Specialized Firefighting Systems effective for alcohol-based fires. 

     

    While practices from methanol bunkering apply, ethanol’s properties demand tailored risk assessments and compliance with international safety standards.  

     

    References: 

    International Maritime Organization (IMO), "Interim Guidelines for the Safety of Ships Using Methyl/Ethyl Alcohol as Fuel (MSC.1/Circ.1621)", https://www.register-iri.com/wp-content/uploads/MSC.1-Circ.1621.pdf 

    American Bureau of Shipping (ABS), "Guide for Methanol and Ethanol Fueled Vessels", https://maritimecyprus.com/wp-content/uploads/2022/02/methanol-ethanol-fueled-vessel-guide-jan22.pdf 

    European Maritime Safety Agency (EMSA), "Guidance for Safe Bunkering of Biofuels", https://www.emsa.europa.eu/publications/download/8028/5119/23.html 

  • Converting marine engines to run on ethanol requires several key modifications: 

    • Fuel Injection Recalibration to adjust for ethanol’s lower viscosity and different combustion profile. 

    • Combustion Chamber Tuning to optimize burn efficiency and reduce unburnt fuel. 

    • Ignition Timing Adjustments due to ethanol’s higher autoignition temperature—especially important in cold conditions. 

    • Upgraded Seals and Gaskets using ethanol-resistant materials like Viton or fluorosilicone. 

     

    Engaging the engine’s OEM is essential to ensure safe and effective integration, maintain performance, and meet emissions standards. 

     

    References: 

    MAN Energy Solutions – "Future Fuel Engines", https://www.man-es.com/our-focus/future-technologies/future-fuels-engines. 

    Wärtsilä – "Future Fuels in Shipping", https://www.wartsila.com/marine/decarbonisation/future-fuels-development 
    American Bureau of Shipping (ABS) – "ABS Advisory on Gas and Other Low Flashpoint Fuels", https://ww2.eagle.org/content/dam/eagle/advisories-and-debriefs/gas-and-low-flashpoint-fuels-advisory.pdf 

  • Technically yes, but it comes with challenges: 

    • Complex Calibration: The engine must adapt to the different combustion traits of methanol and ethanol – requiring advanced fuel injection and timing controls. 

    • Variable Energy Content: Ethanol has a higher energy density than methanol, so blended fuels have inconsistent heating values. Adaptive systems are needed to maintain stable performance. 

    • Lack of Standards: ISO 6583 only covers methanol, with no official spec for methanol-ethanol blends. Using blends requires OEM collaboration and custom testing to ensure safety and compliance. 

     

    While possible in advanced, variable-fuel engines, such use demands further R&D and regulatory development. 

     

    References: 

    ISO, "ISO 6583:2023 – Methanol as a fuel for marine applications", https://www.iso.org/standard/82085.html 

    IEA, "Biofuels – Low Emissions Fuel Pathways", https://www.iea.org/energy-system/low-emission-fuels/biofuels 

    ICCT, "Compatibility of methanol fuel blends with gasoline vehicles and engines," https://theicct.org/wp-content/uploads/2021/12/Methanol-Indonesia-ENG-dec21.pdf 

  • Ethanol offers several environmental benefits over conventional marine fuels: 

    • Up to 90% CO₂ Reduction, depending on feedstock and production process. 

    • Zero SOx Emissions, aiding ECA compliance. 

    • Minimal Particulate Matter, promoting cleaner air. 

    • No Methane Slip, unlike LNG, improving lifecycle climate performance. 

     

    These advantages support compliance with MARPOL Annex VI and align with the IMO’s 2023 Strategy, which targets net-zero GHG emissions by 2050 and increased adoption of low- and zero-emission fuels by 2030. 

     

    References: 

    IMO, "MARPOL Annex VI: Prevention of Air Pollution from Ships" 

    ICCT, "Well-to-Wake Greenhouse Gas Emissions of Marine Fuels", https://theicct.org/publication/ghg-marine-fuels-sept22/ 

    UNCTAD, "Review of Maritime Transport 2023", https://unctad.org/webfly 

  • Yes, although still limited compared to methanol, ethanol pilot projects and planning efforts are emerging: 

    • Research Collaborations between OEMs, fuel producers, and institutions are exploring ethanol's viability through engine tests and emissions studies. 

    • Port Initiatives in hubs like Rotterdam and Singapore are assessing ethanol’s integration into multi-fuel bunker strategies. 

    • National Demonstrations in Brazil and the U.S. are leveraging existing ethanol supply chains to trial marine applications and bunkering processes. 

     

    Scaling ethanol use will depend on broader industry engagement, data sharing, and regulatory support. 

     

    References: 

    Port of Rotterdam, "Alternative Fuels Strategy", https://www.portofrotterdam.com/en/news-and-press-releases/port-of-rotterdam-supports-alternative-fuels 

    Maritime and Port Authority of Singapore (MPA), "Green Port Initiatives", https://www.mpa.gov.sg/web/portal/home/maritime-singapore/green-port 

    U.S. Department of Energy, "Bioenergy Technologies Office (BETO) Projects", https://www.energy.gov/eere/bioenergy/bioenergy-technologies-office 

  • Not yet fully commercialized, but major progress is underway: 

    • MAN Energy Solutions is adapting its ME-LGIM methanol engine platform to support ethanol, focusing on fuel injection, combustion control, and material compatibility. 

    • Wärtsilä is testing ethanol in lab settings through partnerships (e.g., with Raízen), with its modular engines designed for future ethanol integration. 

    • IEA-AMF supports global R&D into ethanol as a marine fuel, aiding emissions data harmonization and engine adaptation efforts. 

     

    Ethanol is not yet ready for fleet-wide engine deployment, but its compatibility with methanol-ready platforms and ongoing OEM research point to strong near-future potential. 

     

    References: 

    MAN Energy Solutions, "Future Fuel Engines", https://www.man-es.com/our-focus/future-technologies/future-fuels-engines 

    Wärtsilä, "Ethanol as a Marine Fuel – Quick Guide", https://www.wartsila.com/marine/decarbonisation/future-fuels-development/alternative-fuels-quick-guide-ethanol 

    IEA-AMF, "Advanced Motor Fuels", https://www.iea-amf.org/ 

  • Generally yes—with some modifications. 

    • Storage Tanks: Stainless steel and coatings used for methanol are usually suitable for ethanol, though ethanol’s hygroscopic nature and elastomer compatibility must be verified. 

    • Pumping & Transfer Systems: Due to ethanol’s different viscosity and conductivity, pumps, seals, flow meters, and grounding systems may require adjustment or recalibration. 

    • Regulatory Alignment: Ports must revise risk assessments and implement ethanol-specific emergency protocols for fire, spill, and vapor exposure. 

     

    Methanol-ready ports are well-positioned to handle ethanol, but tailored safety and handling strategies are essential due to the fuel’s distinct properties. 

     

    References: 

    Methanol Institute, "Marine Methanol: Safe, Proven, Available", https://www.methanol.org/wp-content/uploads/2023/05/Marine_Methanol_Report_Methanol_Institute_May_2023.pdf 

    EMSA, "Alcohols as Marine Fuels – Guidance for Safe Handling and Bunkering", https://www.emsa.europa.eu/publications/download/8028/5119/23.html 

    IAPH, "IAPH supports methanol bunkering at ports with safety checklists", https://sustainableworldports.org/iaph-supports-methanol-bunkering-at-ports-with-safety-checklists/ 

  • To support ethanol bunkering, ports must address key infrastructure and safety needs: 

    • Tank Infrastructure: Use stainless steel or epoxy-coated tanks to prevent corrosion and preserve fuel quality. 

    • Vapor Management: Install vapor recovery or inerting systems due to ethanol’s flammability. 

    • Emergency Response: Ensure firefighting systems (e.g., alcohol-resistant foam) and spill response protocols are ethanol-compatible. 

    • Regulatory Approval: Port authorities must review risk assessments, safety procedures, and crew training plans before approving ethanol operations. 

     

    Ports already handling methanol are well-positioned for ethanol, but adjustments are necessary to reflect ethanol’s specific properties. 

     

    References: 

    EMSA, "Alcohols as Marine Fuels – Safety and Bunkering Guidelines", https://www.emsa.europa.eu/publications/download/8028/5119/23.html 

    DNV, "Port Readiness for Alternative Fuels", https://www.dnv.com/maritime/publications/port-readiness-for-alternative-fuels.html 

    OCIMF, "Guidelines for the Planning and Design of Alcohol Bunkering Facilities", https://www.ocimf.org/publications/information-papers/guidelines-for-the-planning-and-design-of-alcohol-bunkering-facilities 

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