The Icon of the Seas cruise ship is designed to run on liquefied natural gas
New York:
The world's largest cruise ship is set to embark on its maiden voyage on Saturday, but environmental groups fear the liquefied natural gas-powered ship – and other giant cruise ships that will follow – will leak harmful methane into the atmosphere.
Royal Caribbean International's Icon of the Seas sets sail from Miami and offers space for 8,000 passengers on 20 decks. It benefits from the increasing popularity of cruises.
The ship is built to run on liquefied natural gas (LNG), which burns cleaner than conventional marine fuel but poses a higher risk of methane emissions. Environmental groups say methane leaks from ship engines pose an unacceptable risk to the climate because of their 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 the use of LNG as a marine fuel produces over 120% more lifecycle greenhouse gas emissions than marine gasoil,” he said.
In terms of warming effects, methane is 80 times worse than carbon dioxide over a 20-year period, so reducing these emissions is crucial to curb global temperature warming.
Cruise ships like the Icon of the Seas use low-pressure dual-fuel engines that release methane into the atmosphere during the combustion process, known as “methane slip,” according to industry experts. There are two other engines used on bulk carriers or container ships that emit less methane but are too large to fit on a cruise ship.
Royal Caribbean says its new ship is 24% more efficient in terms of carbon emissions than required by global shipping regulator the International Maritime Organization (IMO).
LNG emits fewer greenhouse gases than very low sulfur fuel oil (VLSFO), which powers most of the world's shipping fleet, said Steve Esau, chief operating officer of Sea-LNG, an industry organization.
Cruise engines convert natural gas into electricity in a cylinder, although “it is important to ensure that all natural gas is converted into energy,” said Juha Kytola, director of research, development and engineering at Wartsila, which developed the cruise ship's engines.
What is not converted can escape into the atmosphere during the combustion process, he said, adding that Wartsila's natural gas engine technology emits 90% less methane than it did 20 to 30 years ago.
According to a 2024 study funded by the ICCT and other partners, cruise ship engines have an estimated methane slip of 6.4% on average. The IMO assumes a methane slip of 3.5%.
“Methane is coming under more scrutiny,” said Anna Barford, Canadian shipping activist at Stand Earth, a nonprofit, noting that the IMO said last summer that its efforts to reduce greenhouse gases included combating them Methane emissions.
According to the Cruise Line International Association, of the 54 ships ordered between January 2024 and December 2028, 63% are expected to run on LNG. Currently, around 6% of the 300 cruise ships are powered by LNG.
Newer cruise ships are being designed to run on traditional marine gas oil, LNG or alternatives such as bio-LNG, which account for only a fraction of U.S. fuel consumption.
Royal Caribbean will use different fuels depending on market developments, said Nick Rose, the company's vice president of environmental, social and governance.
“LNG is part of our actual strategy,” he said.
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