The world’s largest cruise ship is poised to make its first voyage on Saturday. Still, environmentalists are concerned that the liquefied natural gas-powered vessel, as well as future massive cruise ships to follow, will emit dangerous methane into the sky. Royal Caribbean International’s Icon of the Seas departs from Miami with a capacity for 8,000 people across 20 decks, capitalizing on the growing popularity of cruises.
The ship is built to run on liquefied natural gas (LNG), which burns more cleanly than traditional marine fuel but poses greater risks for methane emissions. Environmental groups say methane leakage from the ship’s engines is an unacceptable risk to the climate because of its short-term harmful effects. “It’s a step in the wrong direction,” said Bryan Comer, director of the Marine Program at the International Council on Clean Transportation (ICCT), an environmental policy think tank.”We would estimate that using LNG as a marine fuel emits over 120% more life-cycle greenhouse gas emissions than marine gas oil,” he said.
Cruise ships such as the Icon of the Seas use low-pressure, dual-fuel engines that leak methane into the atmosphere during combustion
Methane has 80 times the warming impacts of carbon dioxide over 20 years, therefore reducing emissions is critical to slowing global temperature rise. According to industry experts, cruise ships such as the Icon of the Seas use low-pressure, dual-fuel engines that leak methane into the atmosphere during combustion, a process known as “methane slip.” Two other engines used on bulk carriers or container ships produce less methane, but they are too tall to fit in a cruise ship.
According to Royal Caribbean, the new ship is 24% more efficient in terms of carbon emissions than the International Maritime Organization’s (IMO) requirements. According to Steve Esau, Chief Operating Officer of Sea-LNG, an industry advocacy organization, LNG produces fewer greenhouse gases than very low sulfur fuel oil (VLSFO), which fuels the majority of the world’s shipping fleet.
Cruise engines convert natural gas into power in a cylinder, where it is “important to make sure that all the natural gas is converted to energy,” said Juha Kytola, director of R&D and Engineering at Wartsila, which developed the cruise ship’s engines. He said what is not converted can escape during the combustion process into the atmosphere, adding that Wartsila’s natural gas engine technology emits 90% less methane than it did 20 to 30 years ago.
“LNG is one piece of our actual strategy”
Cruise ship engines have an estimated methane slip of 6.4% on average, according to 2024 research funded by the ICCT and other partners. The IMO assumes methane slip at 3.5%.”Methane is coming under more scrutiny,” said Anna Barford, Canada shipping campaigner at Stand Earth, a nonprofit organization, noting that the IMO last summer said its efforts to cut greenhouse gases include addressing methane emissions.
The Cruise Line International Association predicts that 63% of the 54 ships on order between January 2024 and December 2028 will be fueled by LNG. Currently, around 6% of the 300 cruise ships that LNG powers sail. Newer cruise ships are being constructed to run on regular marine gas oil, LNG, or alternatives such as bio-LNG, which make for just a small portion of U.S. fuel use. Nick Rose, Royal Caribbean’s vice president of environmental, social, and governance, stated that the company will use different fuels as the market evolves. “LNG is one piece of our actual strategy,” he told reporters.