How Decarbonisation of Shipping Is Happening, Fuel by Fuel – The Race to Cut Emissions by Sea

Oct 30 2025 By Figen Sekin Economy Ecology 0 Comments

Ships move ~80–90% of world trade and contribute close to 3% of global greenhouse-gas emissions. After years of drift, the International Maritime Organization (IMO) now is going full steam in the decarbonisation of shipping.

It targets net-zero by or around 2050, with interim 2030 and 2040 checkpoints and new efficiency rules already in force (EEXI/CII). The EU has gone further, pulling oceangoing vessels into its Emissions Trading System (EU ETS) from 2024 and imposing a fuel-carbon-intensity law (FuelEU Maritime) from 2025. Together, these policies force operators to cut fuel burn, switch to cleaner energy, and document every tonne.

Below is how companies are actually preparing for decarbonisation of shipping, fuel by fuel, tech by tech, route by route. I will also tell you who is not on board, and why they are not on board.

Decarbonisation of shipping with new fuels

Ships carry ~80–90% of global trade and emit about 3% of CO₂. That scale forces a dual track: cut today’s fuel burn, and swap the fuel itself on order to get decarbonisation of shipping rolling. You now see first-mover fleets running e-methanol on Asia–Europe loops; engine makers delivering ammonia-ready designs; short-sea routes flipping to battery-electric; pilots for hydrogen derivatives; and ports racing to add bunkering and on-shore power.

The choices however are not equal. Methanol is liquid and easier to store, but has lower energy density. Ammonia carries no carbon, but demands strict safety, NOx control, and new crew training. LNG reduces local pollutants while methane slip erodes climate gains. Biofuels bridge gaps where supply is credible. Wind-assist, air-lubrication, just-in-time arrivals, and speed discipline stack extra cuts.

The IMO’s net-zero course plus EU ETS and FuelEU Maritime push owners and charterers toward cleaner molecules, verified well-to-wake accounting, and green shipping corridors. The outcome is a a pragmatic mix of efficiency now, methanol first, ammonia next, with batteries where routes allow. And all this driven by the cost of carbon, port readiness, and contract pressure in the “decarbonisation of shipping” value chain.

Well-to-wake (WtW) is the full life-cycle climate impact of a marine fuel, from extracting or making the energy (“well”) to burning it on the ship (“wake”). It adds upstream emissions to onboard emissions.

Indicative well-to-wake GHG intensities

Fuel / pathway	WtW GHG intensity (kg CO₂e/MJ)	Notes
MGO (conventional)	0.094	Baseline; varies by engine/operation
Ammonia – brown (from natural gas, no CCS)	0.113–0.194	Requires strict NOx control
Ammonia – blue (with CCS)	0.023–0.077	Capture rate and methane leakage drive the range
LNG (LPDF 4-stroke, incl. methane slip)	varies; high with ~6.4% slip	Engine-specific; see methane-slip table
Green e-methanol (renewable H₂ + captured CO₂)	near-zero (with verified renewables)	Depends on electricity source and CO₂ origin

Let’s look closely at each of the fuels.

Green methanol: first to market

The first large methanol-capable container ships are in service, with Maersk’s Ane Maersk running on Asia–Europe loops. Ports and suppliers are rushing to enable bunkering and Singapore issued a dedicated methanol bunkering standard (TR 129) in March 2025 and has begun simultaneous methanol bunkering and cargo operations.

The LA–Long Beach–Shanghai “green corridor” is another project and is targeting 2025–2030 deployments with reduced or zero lifecycle-carbon ships and expanded shore power at all three ports.

There is an important hurdle to take though, because methanol is toxic. So designs follow strict segregation, detection, and emergency standards (including the new ISO 6583:2024). The lifecycle emissions depend on how the methanol is made. Is it green e-methanol from renewable hydrogen? Because captured CO₂ is scarce and costly, while fossil-based methanol offers limited climate benefit.

Ammonia: zero-carbon promise, complex risks

Engine makers are finishing dual-fuel ammonia engines with the retrofits and first commercial deployments beginning mid-decade. The Viking Energy, a Norwegian platform-supply vessel owned by Eidesvik Offshore and chartered by Equinor, is slated to operate on ammonia in 2026. Fortescue from its side completed the world’s first ammonia bunkering trial in Singapore in 2024; the port is now building out 100,000-t/yr bunkering capability.

While methanol is toxic, ammonia is highly toxic. It’s no coincidence that regulators are still updating safety codes. Combustion of ammonia can generate NOx and nitrous oxide (a potent GHG), and ammonia slip must be avoided at all cost. Multiple studies and EU agencies have already flagged air-quality and health risks without tight controls.

LNG: widespread now, but methane slip is a climate brake

LNG cuts SOx and some CO₂, but real-world methane slip from common engines is higher than assumed, around 6.4% in plume measurements. This erodes all climate gains. The EU and IMO debates now focus on well-to-wake accounting and higher default slip values. The industry from her side argues mitigation is improving, but regulators are tightening.

Biofuels and hybrids: drop-in bridges

Sustainably sourced biofuels are being blended today because they use existing tanks and engines, but true volumes are rather limited and sustainability rules are tightening. Batteries and full electrification work on short sea: Norway’s Ampere electric ferry for instance kicked off a fleetwide shift, proving CO₂ and NOx cuts on fixed routes.

Decarbonisation of shipping by cutting energy use

Ships burn less when they sail smarter, cleaner, and slower. It is kind of a no-brainer. A 10% cut in speed for instance trims roughly 20% in fuel. By stack routing and “just-in-time arrivals” you also kill idle anchorage burn. Add weather routing that rides currents and avoids headwinds and you have all what it takes to save on fuel.

Really? No, because there is quite a lot more than can be done for the decarbonisation of shipping.

A retrofit of the hull with air-lubrication carpets and you lower friction and save 5–10% on many routes. Silverstream’s microbubble “carpet” reduces hull friction and delivers ~5–10% fuel savings; orders now span >100 vessels across segments. Pair that with low-drag propellers, wake equalizers, and high-frequency hull cleanings and you will keep gains real. Fit wind-assisted Flettner rotors or wing sails deliver 5–15% average savings, and more on windy lanes. Verified tests show around 3 tonnes of fuel saved per day on a bulker fitted with BAR Tech WindWings, with typical savings in the single-digit to low-teens percent depending on route and wind.

And then there’s – I kid you not – kite towing. Airseas’ Seawing completed traction-flight milestones on Airbus’ Ville de Bordeaux. The system targets a roughly 20% fuel cut by flying a large automated kite at altitude.

And finally you should cut port emissions too and plug into shore power where available. Cutting off the engine at berth slashes NOx, SOx, PM, and CO₂, and operational discipline in charter parties should be enforced so efficiency pays the party who invests.

Operational & tech measures: typical fuel / CO₂ savings

Measure	Typical fuel savings (%)	Primary notes
Wind-assist (rigid wings / Flettner)	5–15 (route-dependent); peaks higher	Trials report ~3 t/day on a large bulker; verification underway
Air lubrication (microbubble)	5–10	Multi-class deployments; higher modelled in ideal conditions
Weather routing & voyage optimisation	3–10	Gains depend on integration and crew adherence
Just-in-Time (JIT) arrival / port-call opt.	7–25	Strongest where congestion and idle anchorage time exist
Speed management / slow steaming	~−20% fuel for −10% speed	Cubic relationship between speed and power
Shore power at berth (OPS)	Engine-off at berth; net CO₂ −38% to −55%	Grid mix determines net CO₂; big cuts for NOx/SOx/PM near ports

Decarbonisation of shipping by rerouting

Slow steaming and direct routing cut fuel use dramatically. But geopolitics and drought have pushed emissions the other way. The Red Sea crisis sent ships around the Cape of Good Hope, adding 10–14 days per voyage. Extra vessels were used to keep schedules, and double-digit emissions spikes on Asia–Europe trades were observed. Estimates suggest that tens of millions of tonnes of CO₂ was added in 2024 alone.

The Panama Canal drought in 2023–24 forced draft and transit limits, pushing detours and queues. Scientists attributed the disruption mainly to El Niño with longer-term climate sensitivity still under study. The reroutes applied lengthened passages and increased fuel burn.

Route optimisation and speed discipline are core tools for decarbonisation of shipping, but external shocks can rapidly erase gains of course. Below is an example of a reroute and the total days the voyages took.

Origin–Destination	Distance (nm)	Transit in days
Shenzhen–Rotterdam via Suez	10,000	31
Shenzhen–Rotterdam via Cape of Good Hope	13,000	41
Shanghai–New York via Suez	12,370	32
Shanghai–New York via Cape of Good Hope	14,468	38

Who is not joining the decarbonisation of shipping and why

The Clydebank Declaration (COP26) commits countries to develop zero-emission “green shipping corridors.” Signatories include the US, EU states, Japan, Norway, and others. However, major maritime and exporting nations – such as China, India, Russia, Brazil, Saudi Arabia – did not sign, which immediately limits the corridor coverage in key trades.

Pacific Island states (Marshall Islands, Solomon Islands, Seychelles) champion a global carbon levy to fund fuel transition and climate adaptation. China, Brazil, and Saudi Arabia have opposed a levy, citing trade costs for developing economies. The April 2025 compromise veered toward a weaker market mechanism, drawing complaints from vulnerable states. A recent analysis also flagged US opposition to elements of the IMO’s emergent framework.

The EU moved first with ETS and FuelEU Maritime, creating carbon costs and fuel standards on voyages touching Europe and this even for non-EU flags. Some non-EU states view this as extraterritorial, however this pressure is now a major driver of real-world investment.

Why some countries resist a levy”

Concern	How it is framed
Export competitiveness	Levy could raise transport costs for bulk commodities (agri, ores), eroding price advantage.
Food & inflation sensitivity	Pass-through to food prices on import-dependent economies.
Equity design	Preference for technology funds/credits rather than a flat global levy.
Geopolitics	US/others object to perceived “extraterritorial” or EU-led frameworks; push delays.

Problems companies face with decarbonisation of shipping

Decarbonising of shipping, in this case deep-sea freight, is a stack of hard constraints that collide in the engine room, at the bunker hose, and in charter contracts. Six elements play a major role.

1. Fuel availability and price. Green methanol and ammonia supply is small and uneven – ports like Singapore are building standards and pilots, but global volumes lag orders. Price spreads versus oil are wide and volatile.
2. Safety, training, and liability. Methanol is flammable and toxic; ammonia is highly toxic and can form NOx/N₂O if not managed. New ISO rules, class guidelines, and emergency protocols exist, but scaling requires crew retraining, new bunkering procedures, and insurance clarity.
3. Methane slip and lifecycle rules. LNG fleets face higher-than-assumed methane slip. As regulators shift to well-to-wake accounting, some LNG pathways struggle to comply without costly abatement.
4. Infrastructure gaps. Shore power mandates hit a slow-build wall with only a fraction of required EU port connections contracted today. Green-fuel bunkering needs tanks, safety zones, and measurement systems.
5. Split incentives. Owners pay for retrofits; charterers buy fuel. Without carbon prices, performance clauses, or CII-linked charter rates, efficiency investments can stall. The EU ETS/FuelEU now begin to rewire incentives on EU-linked trades.
6. Route disruption risk. Suez closures or Panama droughts can erase efficiency gains overnight and inflate emissions. Companies now scenario-plan routes and fuel buffers into decarbonisation of shipping roadmaps.

Hurdles for globalising decarbonisation of shipping

Decarbonisation of shipping includes cleaner fuels, wind-assist, air lubrication, digital operations, shore power, and smarter routing.

Where governments move, capital is or will be following. Where politics stall, the transition slows and costs rise. Companies that stack today’s efficiency gains with targeted new-fuel bets on well-served corridors will cut exposure to carbon costs and emissions the fastest.

But there is more that poses a hurdle than just the aforementioned:

1. Trade cost and competitiveness: Exporters of bulk goods (ores, grain, fertilizers) argue a carbon price raises freight rates on long routes and eats thin margins. Import-dependent states warn about food-price pass-through.
2. Equity and development: Large emerging economies say a flat global levy shifts costs onto poorer consumers while rich importers outsource responsibility. They demand revenue recycling to the Global South and preferential finance.
3. Technology lock-in and greenwashing risk: Critics point to LNG’s methane slip and biofuel supply constraints. They warn against locking fleets into pathways that fail under Well-to-Wake accounting or rely on weak sustainability claims.
4. Infrastructure gap: Shore power and green-fuel bunkering require big port capex. Small and developing ports risk falling behind, which can reroute trade patterns.
5. Split incentives in contracts: Owners pay for retrofits; charterers pay for fuel. Without clauses tying rates to measured efficiency and carbon exposure, upgrades will stall.
6. Route disruption volatility: Suez closures or Panama droughts can wipe out efficiency gains overnight by forcing longer, dirtier detours.

In short, there is still a lot of work to be done.