The 9-Month Cruise Is Great for TikTok, Bad for the Environment

Royal Caribbean’s nine-month cruise has garnered plenty of headlines (including at this publication) for the novel nature of such a long voyage, and all of the inevitable oddities that come with such an epic journey. But that journey, as captivating as it is, is still a commercial cruise. And commercial cruises aren’t known for being particularly great for the environment.

Much shorter cruises can produce serious carbon emissions—so much so that the cruise industry has faced pressures to make major changes. So far, those changes have been slow to come, even as the industry continues to expand in the rapid post-pandemic travel recovery era.

According to an International Council for Clean Transportation report from 2022, commercial cruising is actually worse for the planet than flying. Thrillist reached out to Bryan Comer, the author of that report and the director of the Marine Program at the ICCT, to help us determine the environmental impact of the Ultimate World Cruise as it traverses the world via Royal Caribbean’s Serenade of the Seas mega-ship, making stops in 60 countries at 150 ports of call.

Comer told Thrillist he can “understand the appeal of an around-the-world adventure onboard a cruise ship” but said that the ships are more harmful to the planet than flying, “not to mention the food waste, sewage, and other pollution that these ships generate.”

But just how harmful is harmful? Comer’s calculation for determining the environmental impact of any cruise relies on three numbers: the number of passengers aboard the ship, the distance the cruise is traveling, and the average carbon emissions for the ship per passenger per nautical mile.

Sounds easy, right? Well, Comer explained, that’s not exactly the case—for the nine-month cruise or any cruise.

“There’s a lot of variability in annual CO2 intensity for cruise ships because their itinerary affects how much fuel they consume,” Comer explained. “We wouldn’t be super confident in the exact amount of CO2 this cruise would emit but you could use this information to ballpark an order of magnitude.”

Still, breaking this down for the Ultimate World Cruise, the ship has a passenger capacity of 2,476 people, and the most recent reported data for the Serenade of the Seas reveals its average carbon emissions to be 540 grams of CO2 per passenger, per nautical mile.

Further complicating matters is the fact that the Ultimate World Cruise poses some unique challenges when it comes to solving this equation. First, we are relying on a self-reported carbon emissions per passenger number from Royal Caribbean which dates back to 2019, and may not be the most accurate representation of the cruise line’s current practices.

Secondly, for such a varied itinerary between stops at ports and sailing, and at varying speeds, getting an exact figure for how far the Serenade of the Seas will be traveling is extremely tricky. Already, the route has changed significantly since its launch in December 2023, due to geopolitical issues.

Royal Caribbean declined to provide the mileage of the cruise’s journey, so determining the distance required a bit of hypothesizing. The ship is sailing around the whole globe, a distance which is 21,600 nautical miles. But the route also involves traveling both north and south, like when the ship traveled down to the waters near Antarctica. To determine a rough distance, I used a nautical mile calculator and imputed 25 of the major stops (of 150) around the world to determine sailing distances. This gave me a rough estimate of 40,526 nautical miles.

Going back to Comer’s formula, 540 grams of CO2 multiplied by the ship’s passenger capacity of 2,476 people multiplied by total mileage traveled—which was hypothesized—of 40,526 nautical miles equals 54,185 metric tons of CO2.

Over 54,185 metric tons of CO2 is equal to about 12,000 gasoline-powered passenger vehicles driven for one year, according to the Environmental Protection Agency. And the Serenade of the Seas is not outfitted with technology that will offset this pollution in a truly substantial way. Royal Caribbean’s newest ship, Icon of Seas, is also more technologically advanced. It is been powered liquified natural gas (LNG) as opposed to traditional fuel, and also features tons of energy-saving measures on board such as smart heating and ventilation, and a more advanced wastewater treatment system. Serenade of the Seas is significantly older than its sister, Icon.

“This ship is 20 years old and it’s fitted with an exhaust scrubber,” Comer explained. “That sounds great, but scrubbers convert air pollution into water pollution. Scrubbers work by spraying seawater into the exhaust to help reduce sulfur emissions, but the collected water, which is acidic and contains carcinogens like polycyclic aromatic hydrocarbons and heavy metals like mercury and lead, is usually discharged overboard.”

Put simply: Poisonous gunk is still going into the ocean, even if it’s not going into the air. So this older ship, on this nine-month journey, is emitting the same amount of CO2 as some 12,000 cars on the road for the entire year. Is it responsible for a company to offer customers a travel experience with such an extreme environmental impact, given the current rate of climate change and the call for reduced carbon emissions to address the problem?

“It would be one thing if the ship was the most modern, ecologically friendly ship ever to sail, but it’s not,” Comer said. “With some passengers paying over $100,000 for this world cruise, you would think there would be a market for building a new ship that runs on green hydrogen and fuel cells rather than fossil heavy fuel oil.”