World’s biggest cruise ship Icon of the Seas: Ever-growing ships add to climate concerns

At over 250,000 Gross tonnage, Icon of the Seas is the world's largest cruise ship. Photo / Supplied, Royal Caribbean

The world’s new largest cruise ship the Icon of the Seas is due to depart on her maiden voyage this Saturday. At a cool quarter million gross tonnes she has space to swallow five RMS Titanics and still have space for more. The Icon is the latest evolution in a trend for larger, flashier cruise ships. It is also a ship that appears to pull in the opposite direction to operator Royal Caribbean’s pledge to produce net carbon neutral ships in the next decade.

But do larger cruise ships equal a larger carbon footprint?

When the forebears of Icon, the Oasis-Class vessels, were first launched in 2016, critics were concerned that the industry’s appetite for ever larger cruise vessels also meant growing emissions.

The Guardian claimed that the emissions of the 6780-passenger Harmony of the Seas was equivalent to five million cars. Pollutants from burning marine diesel, such as sulphur dioxide, was even worse. While the cruise operator disputed figures, Royal Caribbean has since said its ships had turned a corner on climate. Although it has not slowed the growth of ships being built.

RCL’s Wonder of the Seas was launched in 2022, the largest of five Oasis-class ships, and world’s largest by gross tonnage until now. The arrival of the Icon class ships continues steaming along this trend for ever larger vessels.

When it sails out of Florida this Saturday, the Icon will be 6 per cent larger than Wonder, 10 per cent larger than Harmony was eight years ago.

It’s not only Royal Caribbean that has been following the trend.

The average large cruise liner has grown by 10,000 gross tonnes every decade. But the Icon is way ahead of the cruise curve.

Built in the Meyer Turku shipyards in Finland and first floated in December 2022, Royal Caribbean’s largest ship has been pushing the boundaries of what is possible.

For the $2 billion price tag the Finnish shipwrights delivered many world-firsts on Icon, including the largest waterpark at sea, and biggest indoor waterfall.

The 17m waterfall cascades down the Icon’s AquaDome, which sits like a cruise ship-sized glass Tiara at the prow of the ship. The head-turning centrepiece is reportedly the largest glass and steel structure to be floated at sea.

However, Royal Caribbean says its newest ship is not only pushing the envelope in terms of size, but also in efficiency.

The cruise line claims the largest ship in the world will also be its “most sustainable ship to date” when it sets sail this week.

Icon of the Seas. Photo / Supplied

World’s largest cruise ship Icon of the Seas in numbers:

• 7 swimming pools and the first ‘category 6′ waterpark at sea
• 20 decks containing 2805 cabins
• 40 bars, restaurants and cafes
• 50m diameter glass dome
• 7,600 passengers at max capacity. 5,610 passengers at double occupancy
• The largest suite a 3-storey townhouse costs $80,000 a week
• 248,663 gross tonnage (Sister ship Star of the Seas, which is expected in 2025, will be 250,800 gross tonnes)

Growing per-passenger efficiencies not the same as shrinking emissions

A combination of technologies, including reducing drag at sea by running bubbles under the hull and being able to switch the six engines to run on LNG fuel, has led Royal Caribbean to claim that it has cut CO2 emissions by almost a third from the last generation of ships - and removed sulphur emissions completely.

Despite its size, the Icon outperforms the Oasis-class ships and might be the most efficient ship per-passenger in the fleet. This progress is laudable, however the addition of larger ships is still adding to the growing number of passengers at sea.

Seventy per cent of one million cars is still one hundred times less efficient than every passenger driving a comparable journey.

The lifespan of a cruise ship is around three decades, so even with cruise lines like Royal Caribbean setting targets for zero emissions by 2050, it’s likely many of these hydro-carbon burning behemoths will still be bobbing around then.

For anyone longing for the halcyon days of wind-powered ships sailing passengers, emission-free around the Med, cutting emissions is not as simple as sticking up a sail. Electric fuel cells, hydrogen power and biofuels have all been floated as low or zero emission alternatives - though the number of ships deploying these technologies are very small, and none are able to rely on completely on electric power or sail for an entire itinerary. Especially true of ships over the 3000 passenger size.

The cruise industry relies on the logistics of dependable powered ships to ferry holidaymakers and floating hotels from port to port. They can’t afford to be becalmed or blown off course for three days during the peak summer season.

Much of the cruise industry also relies on a business model of growth and ever larger attractions at sea.

The cruise lines are locked into this trend of ever growing ships, for cost efficiencies as much as environmental efficiencies. While efficiencies can be found per-passenger by building larger ships, it still involves creating ever larger ships and a growing emissions debt.

The Icon of the Seas first floated Meyer Turku Shipyard in Finland, earlier this year. Photo / Supplied, Royal Caribbean

Cruise Lines International Association managing director for Australasia Joel Katz says that though it is true the largest ships are getting larger, efficiencies are catching up to make a real difference.

“The newest ships being deployed on our oceans are among the most sustainable to have ever sailed – each new ship is much more efficient and environmentally advanced than those it supersedes.”

While the largest classes of cruise ship are growing, there are far more “small” to mid-scale vessels being made

Of the 12 ships being launched by CLIA members in 2024, nine are smaller than 3000-passengers. While that might not sound like a small ship, it’s this scale of ship that is pushing the boundaries and developing many of the new technologies and efficiencies through their builds- such as hybrid electric and hydrogen fuel cells.

Although cruise vessels represent around 1 / 100th of the world’s shipping it is the pressure that CLIA says will help decarbonise other areas of shipping.

“These initiatives will help create a future generation of vessels capable of running on renewable marine fuels once fuel providers are able to make them available at scale.”

In 2022, CLIA members pledged to decarbonise their operations completely in the next 25 years. Having held decarbonisation summits with the European Chapter of the Cruise Line Association and International Maritime Organisation, CLIA has begun sailing toward the dauntingly large task.

Although organisations like Friends of the Earth have pointed at the cruise industry’s past history of environmental violations as reason to be sceptical of these ambitions. They have asked if the industry can make the transformation credibly and quickly enough.

Big ships are big targets for initiatives like the Friends of the Earth “Cruise Ship Report Card”, which pulls up cruise lines over environmental markers and transparency.

2050: Cruise industry draws line in the sand for decarbonising

The IMO regulations have already said that new ships must be 30 per cent more efficient than those built 10 years ago.

It’s not just the output of the enormous engines, but the impact of shuttling large numbers of tourists around delicate marine environments. There are only so many ports that will be able to cope with a call from the Icon and its two planned sister ships.

Given the fact that most of the 7000+ passengers will have taken at least one flight to embark on their cruise holiday, the secondary emissions are equally enormous.

Growing the ships also means increasing other impacts by a factor. The Icon has had to find impressive new solutions and protocols for shore power while in port, minimising waste and avoiding non-native species being transported on the underside of the ship.

Biofouling operations on a 366-metre-long hull is no small order.

However, the German environment association NABU says that more needs to be done by the cruise industry, more quickly to reduce the outsized impact of these ships.

The group, which also publishes an annual Cruise Sustainability Ship Ranking, has called for cruise lines to completely decarbonise operations in the next 15 years.

“The decisive factor for this is the switch to climate-neutral drive technologies by 2040 at the latest.”

Currently Royal Caribbean’s trajectory for this goal is 10 years too late.

RCL, MSC Cruises and Norwegian Cruise Line Holdings all pledge to reach net zero emissions by 2050.

Decarbonising cruise is possibly the biggest sustainability challenge facing the travel sector, with even the most efficient cruise ships emit more carbon dioxide per passenger kilometre than a passenger jet according to the International Council on Clean Transport, (ICCT).

It’s a big ask, and like the cruise ships themselves, is only growing.