The Fuel That Contains No Carbon and the Ship That Burns It
Maritime shipping's decarbonisation challenge is the most technically difficult in the transport sector because the energy density requirements of deep-sea voyages whose duration and distance create the fuel volume that must be carried on board, combined with the economic imperative to maximise cargo space rather than fuel tankage, make the weight and volumetric energy density of the fuel the primary constraint on decarbonisation pathway selection. Green hydrogen, the electrolytic hydrogen produced from renewable electricity whose zero-carbon combustion or fuel cell conversion creates no greenhouse gas emissions, has the highest mass energy density of any fuel but the lowest volumetric energy density of any practical fuel when stored in the cryogenic liquid or high-pressure compressed forms that shipboard storage requires, making the fuel tankage volume that liquid hydrogen shipboard storage requires commercially prohibitive for large vessels whose cargo volume displacement by fuel tankage reduces revenue earning capacity. Green ammonia, the ammonia produced from green hydrogen and atmospheric nitrogen through the Haber-Bosch synthesis process, has a volumetric energy density approximately fifty-five percent higher than liquid hydrogen and can be stored at minus thirty-three degrees Celsius, substantially warmer than liquid hydrogen's minus 253 degrees Celsius, making its storage technology similar to the liquefied petroleum gas storage that the maritime industry already operates, whose handling knowledge and infrastructure create the technology familiarity that liquid hydrogen storage for ships cannot claim.
The International Maritime Organisation's 2023 revised greenhouse gas strategy, which targets net-zero shipping emissions by 2050 and fifty percent carbon intensity reduction by 2030 relative to 2008 levels, has created the regulatory certainty that shipping companies need to commit capital to alternative fuel vessel procurement and fuel supply infrastructure development. The IMO strategy's trajectory to 2050 zero emissions effectively requires that the vessels ordered in the mid-2020s, whose design life of twenty-five to thirty years extends to 2050 and beyond, be capable of operating on zero-carbon fuels whose commercial availability at the volumes that global shipping requires is still years away but whose investment timelines require decisions now. Ammonia has emerged as the alternative marine fuel that the largest shipping companies and engine manufacturers are betting on for the twenty-year horizon because its combination of carbon-free combustion, manageable storage temperature, existing industrial supply infrastructure, and the accelerating development of green ammonia production from renewable electricity creates the most credible commercial pathway to zero-carbon shipping at scale.
MAN Energy Solutions and the Two-Stroke Ammonia Engine
MAN Energy Solutions is the Danish marine engine company whose two-stroke marine engine design dominates the global large deep-sea vessel engine market, providing the propulsion for over half of the world's ocean-going vessels. Its development of the ME-LGIP two-stroke ammonia-fuelled engine, which adapts the proven ME-GI dual-fuel engine platform to handle ammonia's different combustion characteristics including its higher ignition temperature, lower flame speed, and toxicity management requirements that differ from LNG and conventional marine fuel oil, is the most commercially consequential engine development in the ammonia marine fuel market because MAN ES's market position means that its ammonia engine's commercial availability effectively determines when the majority of large newbuild vessels can be specified with ammonia propulsion. The ME-LGIP ammonia engine received type approval from several classification societies in 2024 and is being specified in newbuild orders for large bulk carriers, tankers, and container ships whose owners are making the ammonia-ready or dual-fuel ammonia design choice in new vessel orders placed in anticipation of green ammonia's commercial availability at the bunker ports that their trade routes call at.
Wärtsilä, the Finnish marine and energy technology company whose four-stroke medium-speed engines serve the cruise, ferry, and smaller vessel segments that MAN ES's two-stroke engines do not address, completed a two-year research and development programme for its Wärtsilä 25 and Wärtsilä 31 engine series ammonia combustion versions and announced commercial availability in 2025. Its ammonia-capable engines in the four-stroke segment and its LNG and methanol engine experience create the engine technology range that spans the full spectrum of commercial vessel types from large cruise ships and ferries to smaller cargo vessels and offshore support vessels. The Viking Energy ammonia-powered offshore vessel, a supply ship converted to run on liquid ammonia in partnership with Eidesvik Offshore and MAN ES, represents the operational demonstration whose sea trial results in Norwegian waters in 2023 and 2024 have provided the first at-sea operational data for ammonia-fuelled marine engine operation in a commercial vessel context.
Green Ammonia Supply and the Infrastructure Investment
The commercial deployment of ammonia-fuelled ships depends ultimately on the availability of green ammonia at the bunker ports where ships fuel, at prices that allow ammonia-fuelled shipping to compete economically with conventional marine fuel oil at the carbon prices and regulatory costs that IMO decarbonisation requirements create. The green ammonia supply chain, from the renewable electricity that powers the electrolysers to the ammonia synthesis plant to the shipping and storage infrastructure that delivers green ammonia to bunker ports, is being developed by industrial gas companies, energy companies, and dedicated green ammonia producers whose project announcements in Norway, Chile, Australia, the Middle East, and Namibia reflect the geographic distribution of renewable electricity resources and the shipping route proximity that bunker port location requires. The scale of green ammonia required to fuel a meaningful fraction of global shipping significantly exceeds current green ammonia production capacity, creating the chicken-and-egg investment problem that the regulatory certainty of IMO 2050 targets is intended to resolve by providing the market signal that green ammonia production investment requires.
Top 10 Companies in Ammonia-Fuelled Marine Technology Globally
- MAN Energy Solutions: Danish marine engine company with ME-LGIP two-stroke ammonia engine in commercial specification; its dominant position in large deep-sea vessel engines and its ammonia engine type approval create the company whose ammonia engine availability effectively determines the pace of ammonia propulsion adoption in the large vessel market that represents the majority of maritime carbon emissions.
- Wärtsilä: Finnish marine and energy company with four-stroke medium-speed ammonia engine series commercially available from 2025; its cruise, ferry, and smaller vessel engine market and its Viking Energy ammonia demonstration participation create the four-stroke engine company's ammonia propulsion commercial position in the medium vessel segment.
- NYK Line: Japanese shipping company with ammonia-fuelled large vessel orders and ammonia fuel supply chain investment; its Green Ammonia project participation and its ammonia-fuelled vessel newbuilding programme create the Japanese major shipping company's leadership in ammonia vessel deployment whose regulatory and financial commitment demonstrates shipping company confidence in the ammonia pathway.
- Yara International: Norwegian fertiliser and ammonia company with green ammonia production and Yara Birkeland autonomous ammonia-powered container vessel; its industrial ammonia production expertise and its bunkering infrastructure development create the ammonia producer whose supply chain position in ammonia shipping extends from production through vessel operation.
- Eidesvik Offshore (Viking Energy): Norwegian offshore vessel company with the Viking Energy ammonia-fuelled offshore supply vessel; its sea trial operational data and its MAN ES and Equinor partnership create the offshore vessel company whose ammonia propulsion demonstration provides the first commercial vessel ammonia operation data that engine developers and classification societies use for regulatory framework development.
- DNV: Norwegian classification society with ammonia-ready and ammonia-fuelled vessel class notation development; its alternative fuel classification rules and its ammonia ship safety framework create the regulatory infrastructure that ammonia vessel design, construction, and operation compliance with maritime safety standards requires.
- Samsung Heavy Industries: South Korean shipbuilder with ammonia-fuelled vessel designs and newbuilding capability; its very large ammonia carrier design and its dual-fuel vessel construction for major shipping companies create the shipbuilder whose ammonia vessel construction capability serves the Korean and international shipping company orders for ammonia-capable vessels.
- Siemens Energy: German energy technology company with green ammonia production electrolyser and process equipment; its electrolyser technology for green hydrogen and its synthesis equipment create the technology supplier whose components are required in every green ammonia production plant that the shipping fuel supply chain depends on.
- Topsoe: Danish catalysis and energy technology company with ammonia synthesis and solid oxide electrolyser technology for green ammonia production; its SOEC electrolysis and Haber-Bosch process expertise create the technology company whose integrated green ammonia production process design positions it as the engineering partner for green ammonia production plant development.
- TotalEnergies: French energy company with green ammonia production investment and shipping fuel supply development; its renewable energy capacity for green ammonia electrolysis and its global bunker fuel supply infrastructure create the energy major's position in the green ammonia shipping fuel supply chain whose commercial development requires the capital and distribution capability of major energy companies.