Heavy Fuel Oil Persists, but NABU Sees a Path to Climate-Neutral Cruising

Half the world's cruise ships still burn heavy fuel oil—a tar-like residue that must be heated to 100 °C just to flow—the German environment group NABU has found in its latest annual ranking. The report, based on a survey of cruise operators, shows only incremental progress on emissions, placing even the top-rated lines well below half the maximum score.

Yet NABU's shipping expert Sönke Diesener struck an optimistic note at the presentation, saying that the first completely climate-neutral cruise could sail before 2030. Hybrid propulsion—combining wind assistance, batteries where technology is advancing "extremely positively"—and the coming availability of e-methanol (produced with green hydrogen) would make it possible. As an example, Diesener pointed to TUI's Mein Schiff 7, which could be converted to e-methanol at short notice.

The ranking, which NABU has compiled since 2012, now focuses on decarbonisation strategy rather than just local air pollution. The top performers, Norwegian lines Havila and Hurtigruten, scored only 7.5 and 7.25 out of a possible 17 points. TUI's Mein Schiff fleet and AIDA reached 6 points, while Hapag-Lloyd Cruises managed 4.75.

NABU leaders stressed that the industry has both the financial resources and the technical solutions to move faster. "A great deal of money is earned here, so I expect the cruise sector to lead," said Hamburg NABU chairman Malte Siegert. He described heavy fuel oil as "absolute filth" and noted that scrubbers filter pollutants from exhaust but often discharge the captured waste into the sea. The group points out that container shipping has already reduced heavy fuel oil use far more aggressively.

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What the Ranking Reveals About Cruise Operators, Technology, and Regulation

Heavy Fuel Oil: The Will, Not the Technology, Is Missing

NABU's data shows that switching away from heavy fuel oil is feasible today—container lines prove it—yet half of cruise ships still rely on it. The bottleneck is not technology but corporate willingness and the slow roll-out of alternative fuels. While CLIA, the cruise industry body, says its members plan to invest about €70 billion by 2036, much of that for decarbonisation, the immediate picture remains fossil-dependent.

Land Power: Hamburg Pushes Ahead, Mediterranean Lags

Shore power is a bright spot. Hamburg, which handles 220–240 cruise calls a year, has had a shore-power terminal since 2016 and will make its use mandatory from 2027—three years ahead of the EU requirement. In port, a cruise ship's energy appetite is huge, so switching to land-based renewables cuts significant emissions. However, NABU and CLIA both note that only about 4% of global berths offer shore power. "In the Mediterranean or the Atlantic, you still have to search for it," Diesener said, a complaint the cruise industry itself echoes.

Technology Pipeline: The Meyer Werft Vision

Meyer Werft presented a concept at the Miami cruise fair for a 275-metre vessel carrying 1,900 passengers that could be powered entirely by batteries. The limitation: battery capacity would restrict it to itineraries with many short stops. NABU sees projects like this, alongside the e-methanol-capable hull of Mein Schiff 7, as evidence that the technology pathway exists. The question is whether operators will order such ships at scale and whether regulators will close the fuel-availability gap with incentives that reward early movers.

Who Feels the Pressure—and Who Gains

The ranking creates commercial pressure: Havila and Hurtigruten, which score highest, can market their sustainability edge to environmentally conscious travellers. TUI's and AIDA's mid-tier scores reflect some investment but not enough to break away from the pack. Lines still burning heavy fuel oil face growing reputational risk, especially as NABU explicitly aims to guide holidaymakers. The industry's own call for "reliable, ambitious regulation" to unlock investments in clean fuels signals that some operators now want governments to force a faster, more level playing field.

What Travellers and Cruise Lines Should Watch Now

  • For travellers: Use the NABU ranking (top performers: Havila and Hurtigruten, followed by TUI's Mein Schiff and AIDA) as a starting point if sustainability matters. Be aware that even the best score well below the maximum; no mass-market cruise can yet claim climate neutrality.
  • For cruise operators: The gap between container shipping and cruise fleets on heavy fuel oil shows that switching is possible. Lines that move early to e-methanol-capable ships and battery-hybrid designs—illustrated by Mein Schiff 7 and Meyer Werft's concept—could leapfrog the current ranking and capture a premium-segment environmental reputation before competitors follow.
  • For port authorities and regulators: Hamburg's mandatory shore-power rule from 2027 offers a model. With only 4% of global berths equipped, accelerating shore-power investment, especially in Mediterranean and Atlantic ports, is the fastest way to cut in-port emissions. CLIA's own lobbying for investment-incentivising regulation suggests there is industry appetite for a coordinated push.

Risk & Opportunity Assessment

Commercial RiskMediumLines relying on heavy fuel oil face operational risk if fuel taxes or port bans tighten; the €70bn CLIA investment pledge signals that capital markets will scrutinise whether these sums translate into verifiable decarbonisation.
Competitive RiskMediumHavila and Hurtigruten's top ranking, and the public linking of sustainability to purchasing decisions by NABU, create a competitive advantage that mid-tier operators like AIDA and TUI will need to close or risk losing environmentally-minded customers.
Regulatory RiskMediumHamburg's 2027 mandatory shore-power rule and the EU's own timetable are concrete regulatory shifts; ports without infrastructure could lose calls. Broader fuel standards are being demanded by the industry itself, raising the stakes for non-compliance.
Reputation RiskHighNABU's explicit goal of offering sustainability guidance to travellers makes the ranking a public benchmark. Low scores or continued heavy fuel oil use create immediate reputational damage, particularly as the contrast with container shipping is highlighted.
Technology DisruptionMediumThe Meyer Werft battery-electric concept and the near-term e-methanol readiness of ships like Mein Schiff 7 show that a step-change in propulsion is within reach before 2030. If one major line places firm orders, the rest of the fleet could be stranded.
Commercial OpportunityMediumThe first truly climate-neutral cruise could command a premium fare. Lines that convert ships early and secure e-methanol offtake agreements could differentiate strongly, especially as NABU and similar organisations influence consumer choice.