Ethanol could be used to fuel a growing fleet of methanol-capable ships with limited modifications to existing dual-fuel engines and bunkering infrastructure, offering an alternative as supplies of low-emission methanol remain constrained, according to a new industry study.
The study, published by the Maritime Ethanol & Methanol Alliance (MEMA), a platform of the Global Centre for Green Fuels (GCGF), found that ethanol could support more than 300 methanol-capable vessels currently in service or on order, either independently or blended with methanol.
The United States has approximately 2 billion gallons of spare annual ethanol production capacity, with plants capable of producing 18.5 billion gallons compared with output of 16.4 billion gallons in 2025, the report said.
The country produces just over half of the world's fuel ethanol and exports to around 80 countries, largely through Gulf Coast terminals that also serve as major bunkering hubs.
According to the study's illustrative scenarios, supplying ethanol equivalent to 1% of international shipping's annual fuel consumption by mass would require approximately 1 billion gallons, while a 5% share by the mid-2030s would need around 5 billion gallons.
“Ethanol is moving beyond pilots, and this study shows the United States has the production base and export infrastructure to supply shipping at scale. The next challenge is consistency. As international bunkering grows, shipping needs standardised and fungible marine fuel specifications, together with traceable feedstocks and a robust chain of custody, so that ethanol from different producers and regions can be used with confidence," said Clarence Woo, Managing Director of GCGF.
The report comes as ethanol bunkering begins moving beyond trials. On September 28, Tangier Maersk completed a commercial ship-to-ship bunkering of US corn ethanol in Houston, described as the first publicly announced US ethanol bunkering operation involving a deep-sea container vessel.
The study assessed ethanol at technology readiness level 8–9, indicating technical maturity with commercial deployment emerging.
Compared with heavy fuel oil, ethanol virtually eliminates sulphur oxide emissions and could reduce nitrogen oxide emissions by 40–94% and particulate matter by 90–99%, depending on engine technology, according to the report.
It also estimated ethanol's net production cost, after co-product revenue, at below $1 per gallon, while identifying the need for standardised marine fuel specifications and traceable supply chains to support wider international adoption.
ABS provided the technical analysis as knowledge partner, while US ethanol producer Marquis Energy contributed industry input. The study's views and recommendations are those of MEMA.