‘Cruisezilla’ is a greener holiday than you’d think

Cruise ships are a relatively small contributor to the world’s climate footprint. Shipping as a whole accounts for about 3% of global emissions, but cruise vessels are likely to be less than 0.2%.

By David Fickling

For many people, cruise ships sound like one of the blander circles of hell: Enormous floating holiday parks laden with lukewarm buffet food, bored families, and gastroenteritis. To that list you can add a fresh torment: environmental damage.

The ballooning size of the vessels means we're now in the age of “cruisezillas,” according to Transport & Environment, a climate lobby group. The Icon of the Seas, which became the world’s largest cruiser when it was launched earlier this year, is roughly five times the size of the RMS Titanic. With room for 5,600 passengers and 2,350 crew, it can accommodate as many people as one of Las Vegas’s bigger hotels. Standing in the bow, you’re roughly as far from the stern as the top floor of the Empire State Building is from the ground. The Icon’s sister ship, currently under construction in Finland ahead of a launch next year, will be even bigger.

“These floating cities emit more greenhouse gases and pollutants than ever before,” Transport & Environment wrote. “Between 2019 and 2022, CO2 emissions from cruise ships in Europe grew by 17 per cent despite the Covid-19 pandemic, and methane emissions surged by 500 per cent.”

Credit: Bloomberg

And yet the immediate impact of cruisezillas is something climate advocates should welcome. Compared to the smaller vessels that came before, they’re far more efficient. They’re also a cleaner way of taking a holiday than a long-haul flight. The real problem isn’t that they’re the most carbon-intensive type of travel. Instead, it’s that their increasing efficiency is making a mode of exotic vacation available to larger and larger numbers of people.

The rise of the modern cruise industry closely tracks that of container lines. For a naval architect, both vessels have distinct similarities. Unlike slow-moving tankers and the bulk carriers that move coal, iron ore and wheat across the seas, container and cruise ships have to travel relatively fast. The best way to save fuel (and, by extension, carbon emissions) is to make them enormous.

The savings are significant. Compared to an older ship carrying 1,000 container boxes, a modern one with 10,000 or more might be emitting only 20 per cent or so of the emissions per metric ton, per nautical mile, according to data in a 2021 Polish study. The arrival of giant container vessels like the Ever Given meant that by 2018, the fleet as a whole was consuming about a third less carbon per ton-mile than it had been a decade earlier, according to the International Maritime Organization.

Credit: Bloomberg

That means its carbon footprint will soon start shrinking. Consumption of maritime crude is already peaking as liquefied natural gas displaces fuel oil, and hydrocarbons as a whole will go into decline in the early 2030s as efficiency improvements outpace growth in cargo volumes, Wood Mackenzie, an energy consultancy, wrote in a report earlier this year.

Cruise ships are following the same path. About three-quarters of the tonnage on order this decade uses alternative fuels instead of traditional crude-derived marine fuel oil. The bulk of those will have mixed-use engines that in the short term will primarily burn LNG. These almost eliminate sulfur and nitrogen emissions that damage human health, and potentially reduce carbon pollution by about 15 per cent — though the latter depends a lot on how much methane escapes without being burned.

Cruise ships, furthermore, are a relatively small contributor to the world’s climate footprint. Shipping as a whole accounts for about 3 per cent of global emissions, but cruise vessels are likely to be less than 0.2 per cent. For all their visibility when their serried balconies tower over the cities where they dock, they emit far less than container vessels, tankers, bulk carriers, and even ferries and vehicle carriers.

Credit: Bloomberg

The biggest risk from cruising, in fact, is not the humongous scale of a modern ship’s smokestack pollution, but its relative leanness. Without zero-carbon propulsion — still a distant prospect, at this point — the emissions from marine engines are in more or less direct proportion to the amount of fuel they burn. More efficient ships reduce that amount per passenger, per kilometer — but less fuel means lower costs, and that falling price opens up the prospect of demand that didn’t exist when shipping was more expensive and dirtier.

That’s in a nutshell the story of the modern shipping industry as a whole. Its technological improvements have reduced the cost of fuel, and by extension the price of carbon. As a result, that one-third reduction in CO2 per ton-kilometer has gone hand in hand with a one-third increase in absolute pollution — because, encouraged by falling prices, the world has switched to shifting far more tons, far farther, than it ever did before.

The aviation industry had more or less driven cruise travel into extinction a couple of generations ago. It’s now booming — not just because of a shift in our culture, but also because the shipping industry’s efficiency gains have made it cheaper and introduced it to a new market that didn’t exist before. That’s a far more insidious problem.