Icon of the Seas: World's Largest Cruise Ship Sets Sail, Sparking Concerns Over Methane Emissions

Set for its maiden voyage on Saturday, the world's largest cruise ship, Royal Caribbean International's Icon of the Seas, will depart from Miami.

Concerns are raised by environmental groups about the potential for harmful methane leakage into the atmosphere from the liquefied natural gas-powered vessel, and similar concerns are anticipated for other upcoming giant cruise liners.

Photo Credit: X/@RoyalCaribbean

World's Largest Cruise Ship Sparks Concern Over Climate

With a capacity for 8,000 passengers across 20 decks, the ship takes advantage of the growing popularity of cruises. Built to run on liquefied natural gas (LNG), which burns more cleanly than traditional marine fuel but poses greater risks for methane emissions, the ship is considered by environmental groups to present an unacceptable risk to the climate due to short-term harmful effects of methane leakage from its engines.

Bryan Comer, the director of the Marine Program at the International Council on Clean Transportation (ICCT), labelled it a step in the wrong direction, estimating that the use of LNG as a marine fuel emits over 120% more life-cycle greenhouse gas emissions than marine gas oil. In terms of warming effects, methane, which is 80 times worse over 20 years than carbon dioxide, is seen as a crucial area for emissions reduction to mitigate global temperature warming.

Low-pressure, dual-fuel engines, which cruise ships like Icon of the Seas utilize, are known to leak methane into the atmosphere during the combustion process, a phenomenon referred to as "methane slip," according to industry experts. Two other engines emitting less methane, designed for bulk carriers or container ships, exist but are deemed too tall for installation in a cruise ship.

The new ship by Royal Caribbean is claimed to be 24% more efficient in terms of carbon emissions than required by the International Maritime Organization (IMO), the global shipping regulator. Additionally, it is noted by Steve Esau, chief operating officer of Sea-LNG, an industry advocacy organization, that LNG emits fewer greenhouse gases than the very low sulfur fuel oil (VLSFO) powering most of the global shipping fleet.

Juha Kytola, director of R&D and Engineering at Wartsila, the entity responsible for developing the cruise ship's engines, emphasized that cruise engines convert natural gas into power within a cylinder, stressing the importance of ensuring the complete conversion of natural gas into energy. He noted that any natural gas not converted can escape into the atmosphere during the combustion process. Kytola added that Wartsila's natural gas engine technology now emits 90% less methane than it did 20 to 30 years ago.

2024 research funded by the ICCT and other partners estimates that cruise ship engines have an average methane slip of 6.4%, with the IMO assuming a methane slip of 3.5%. Anna Barford, Canada shipping campaigner at Stand Earth, a nonprofit organization, highlighted that methane is facing increased scrutiny, particularly after the IMO included addressing methane emissions in its efforts to reduce greenhouse gases.

According to the Cruise Line International Association, 63% of the 54 ships on order from January 2024 to December 2028 are expected to be powered by LNG. Currently, about 6% of the 300 cruise ships in operation are fueled by LNG. Newer cruise ships are being designed to run on traditional marine gas oil, LNG, or alternatives like bio-LNG, which only represent a fraction of U.S. fuel consumption.

Nick Rose, Royal Caribbean's vice president of environmental, social, and governance, stated that the company will utilize different fuels as the market evolves, emphasizing that LNG is one aspect of their overall strategy.