The shipping industry accounts for about 3% of global greenhouse gas emissions, and the regulatory bar is rising. The International Maritime Organization's (IMO) 2023 climate strategy aims for net-zero emissions "by around 2050" and calls for reducing the carbon intensity of international shipping by at least 40% by 2030.
Because electrifying ocean-going ships is limited by range and energy density, the sector has accelerated the search for liquid alternatives. This is where e-fuels come in—fuels produced from green hydrogen combined with a source of carbon (methanol) or nitrogen (ammonia).
The competition between green methanol and green ammonia is often framed as “carbon in the molecule versus zero carbon.” For operators, however, the map looks different: operational risk, deployment time, and total cost of ownership.
What the decision-maker is really buying when choosing a fuel
The choice of fuel is, in practice, a system-level decision. Four factors dominate:
- Technological maturity (engines, maintenance, retrofit)
- Safety (crew, ports, licensing)
- Bunkering infrastructure (corridors, hubs, standardization)
- Regulatory economics (carbon cost and compliance)
In summary, methanol reduces deployment risk now; ammonia promises to reduce carbon risk in the theoretical limit.
That is why green methanol leads today: it delivers more of these four factors in the present, with fewer “implicit bets.”
Green methanol and the advantage that turned into adoption
Methanol is liquid under ambient conditions, which reduces tank complexity and brings refueling closer to what ports already do with liquid fuels. This does not eliminate risk (it is flammable), but the risk is familiar and manageable with already established protocols.
The second differentiator is engine maturity. MAN reports operational experience with its methanol dual-fuel engines since 2016. Wärtsilä includes methanol engines as part of its “fuel flexibility” strategy.
On the commercial front, Maersk brought the issue into the spotlight in 2023 by launching the “Laura Mærsk,” a methanol-enabled container ship, and moved forward with orders for larger vessels along the same transition path.
An important technical note: methanol requires more onboard volume than fossil fuels, but its volumetric energy density (typically cited around 15.6–15.8 MJ/L) is competitive among liquid e-fuels.
Green ammonia and the package of risks that still limits scale
Green ammonia is attractive because it contains no carbon and can eliminate CO₂ emissions during combustion. The obstacle lies in its operation.
The NIOSH (CDC) classifies 300 ppm as an immediately dangerous to life or health level (IDLH). In bunkering operations, this raises the bar for engineering and licensing, especially in urban areas.
Logistics also play a role. Ammonia liquefies under refrigeration or pressure (with a boiling point close to -33 °C), requiring more complex tank and handling systems.
There is also an indirect climate risk that executives cannot ignore: N₂O emissions and ammonia slip can drastically reduce the climate benefit if not properly controlled. N₂O has a GWP of 273 (100 years) relative to CO₂.
The technology is evolving, but it is still in the “ramp-up” phase. MAN has begun full-scale testing of a marine ammonia engine, an important milestone, though different from global commercial maturity.
Why the EU ETS and FuelEU Maritime accelerate methanol first
The cost of remaining on fossil fuels is increasing by design. The EU has included maritime transport in the EU ETS, with a progressive phase-in of obligations on reported emissions since 2024. In 2025, FuelEU Maritime began requiring reductions in the GHG intensity of the energy used by ships operating in the region.
In practice, policies like these tend to favor the fuel that can be implemented with the least operational friction. Today, that fuel is methanol.
Brazil and the window of opportunity
Brazil can move from a “potential supplier” to a “host of a green corridor.” A report by the ICCT identified six ports with potential for renewable bunkering hubs: Santos, Rio Grande, Itaqui, Pecém, Navegantes, and Porto do Açu.
Additionally, the availability of biomass and biogenic CO₂ associated with value chains such as ethanol creates leverage for e-methanol pathways with improved climate performance. Maersk has even tested blends with Brazilian ethanol in maritime decarbonization efforts, signaling the relevance of this topic for the national bioeconomy.
Conclusion
Green methanol is outperforming ammonia in the short and medium term due to pragmatism: more mature engines, simpler logistics, more manageable risks, and faster deployment.
Ammonia remains a long-term candidate, but it will need to prove that it can operate safely and control indirect emissions with the same level of predictability the sector requires for 25–30 year assets.
