A new study from the Mærsk Mc-Kinney Møller Center for Zero Carbon Shipping suggests that ethanol could be a viable alternative fuel for ships, especially those that are already fitted with methanol-capable engines. This research also outlines a possible way for ethanol to be used in traditional diesel-powered vessels.
The report, titled Ethanol as a Marine Fuel: Exploring Its Usability, was released on Thursday. It investigates how ethanol can be used in existing marine engines and what changes would be necessary to make it a commercially viable option.
The findings come as shipowners explore alternatives to methanol and ammonia for lower-emission fuels that can be produced and distributed on a large scale. Ethanol already has established production and distribution systems, especially in the United States and Brazil, which could give it an edge over fuels that require completely new supply chains.
The study, conducted in collaboration with partners like NORDEN, TotalEnergies, and ABS, looks at two main applications: using ethanol in engines designed for methanol and mixing ethanol with marine gas oil for use in traditional diesel engines.
Researchers found that ethanol shows strong compatibility with methanol-capable engines, needing only minor adjustments to be effective.
Ethanol and methanol have similar chemical properties, so engines designed for methanol can usually run on ethanol with some changes to fuel injection timing and engine controls. Additionally, ethanol has a higher energy density, meaning ships would require less fuel storage to achieve the same range compared to methanol.
The challenges mentioned in the report are mostly about engine optimization, validation, and certification, rather than significant technical obstacles.
Maersk has been testing ethanol on its methanol-fueled container ship, Laura Maersk, since 2025. They began with a 10% ethanol blend before increasing to higher concentrations. By June 2026, the company confirmed successful tests using 100% ethanol.
Recently, Maersk completed a commercial ethanol bunkering operation in Houston with the 9,016-TEU Tangier Maersk. This was marked as the first ship-to-ship commercial ethanol bunkering of a deep-sea container vessel in the United States.
Engine manufacturers are also advancing in this area. Companies like Everllence, WinGD, Wärtsilä, and HD Hyundai have been testing ethanol in marine engines, while Caterpillar announced conversion kits in July for certain MaK engines to switch between methanol and ethanol.
However, a bigger question remains whether ethanol could be used in the larger fleet of conventional diesel-powered ships.
To explore this, researchers tested mixtures of ethanol and marine gas oil for fuel stability, combustion properties, and safety requirements.
Their findings highlighted two major issues.
First, even small amounts of ethanol significantly lowered the flashpoint of the fuel blend. A mixture with just 10% ethanol had a flashpoint of around 13.5°C, which is well below the 60°C minimum generally required under SOLAS for conventional marine fuels.
Efforts to improve the flashpoint with biodiesel and other additives did not yield successful results in laboratory tests.
Second, blends of ethanol and diesel tended to separate during storage, especially in cooler temperatures. All three blends tested separated after one week at 10°C, raising concerns about fuel reliability on ships.
Researchers suggested using onboard blending systems as a potential solution. This would allow ethanol and diesel to be mixed right before entering the engine instead of being stored together for long periods.
However, the low flashpoint still means that safety equipment and modifications to onboard fuel systems would be necessary.
Despite these challenges, the study indicated that converting some existing vessels to run on ethanol blends might be economically beneficial.
Taking a Kamsarmax bulk carrier as an example, the researchers estimated that modifying the vessel for ethanol-marine gas oil blends could cost about half as much as fully converting it to methanol dual-fuel capabilities.
This analysis considered a 30% ethanol blend and compared operating costs against traditional marine fuels under emissions-pricing mechanisms based on the draft IMO Net-Zero Framework.
According to the study's baseline assumptions, this conversion wasn't competitive compared to traditional operation on very low-sulfur fuel oil. However, the economics improved significantly for ships operating primarily in sulfur emission control areas, vessels with higher fuel consumption, and those able to obtain ethanol with a low lifecycle carbon intensity.
For example, a large container ship that consumes about 25,000 tonnes of fuel annually could feasibly run on a 30% ethanol blend across a wider range of fuel carbon intensities.
These conclusions depend, in part, on future emissions regulations, fuel prices, and the availability of ethanol produced with low greenhouse gas emissions.
The report doesn't specify how much ethanol could realistically aid in the overall decarbonization of shipping. While ethanol is produced in large volumes, its environmental impact varies greatly depending on feedstocks, farming practices, land use changes, and production methods. The Center indicated that issues of sustainability, lifecycle emissions, and scalability would be addressed in separate reports.
This distinction is crucial because having a technically suitable ethanol does not mean that every source of it is a low-emission marine fuel.
For shipowners, the immediate advantage may be increased fuel flexibility. Vessels designed for methanol could potentially use ethanol when it is more available or cost-effective, reducing reliance on a single alternative fuel source.
For traditional diesel-powered ships, the situation remains more complex, requiring more investment and solutions to stability and safety concerns.
Nonetheless, the Center's findings suggest that ethanol could have a wider role in maritime fuel supply than previously thought, especially as shipping companies seek practical ways to reduce emissions without committing to one specific fuel technology.