The world’s largest cruise ship, the Icon of the Seas embarked on its inaugural journey this Saturday. However, not everyone is convinced with this vessel’s performance, saying that in terms of ecology, it is a step back.
Icon of the Seas on its first sea trial outside Turku, Finland. This is the largest cruise ship as of 2024. Image credit: Chakie2 via Wikimedia, CC BY-SA 4.0
The new ship was developed by Royal Caribbean International. It is powered by liquefied natural gas (LNG). However, environmental organizations express concerns about potential methane emissions from this massive vessel and others of its kind in the future.
Capable of accommodating 8,000 passengers across 20 decks, the Icon of the Seas departed from Miami, tapping into the increasing allure of cruise travel.
The vessel is specifically designed to operate on liquefied natural gas (LNG), which, compared to traditional marine fuel, burns more cleanly. However, this cleaner fuel option raises concerns about heightened risks associated with methane emissions.
Environmental groups emphasize that methane leakage from the ship’s engines poses an unacceptable risk to the climate due to its short-term adverse effects. Some experts say that using LNG as a marine fuel results in emitting over 120% more life-cycle greenhouse gas emissions than marine gas oil.
In terms of climate-warming effects, methane is 80 times more potent than carbon dioxide. Reduction of these emissions is critically important for mitigating global temperature increases.
Cruise ships like the Icon of the Seas employ low-pressure, dual-fuel engines that release methane into the atmosphere during the combustion process, a phenomenon known as “methane slip”. Although there are alternative engines used in bulk carriers or container ships emitting less methane, their height makes them incompatible with cruise ship design.
According to Royal Caribbean, its new ship surpasses the carbon emissions efficiency standards set by the International Maritime Organization (IMO), the global shipping regulator, by 24%. Burning LNG also emits fewer greenhouse gases compared to very low sulfur fuel oil (VLSFO), which powers the majority of the global shipping fleet.
The process of converting natural gas into power in cruise ship engines involves cylinders, where ensuring the full conversion of natural gas to energy is crucial. Any unconverted natural gas has the potential to escape into the atmosphere during the combustion process.
Research from 2024 indicates that cruise ship engines exhibit an average methane slip of 6.4%, surpassing the International Maritime Organization’s (IMO) assumed level of 3.5%.
Looking ahead, the Cruise Line International Association projects that 63% of the 54 ships expected to be commissioned between January 2024 and December 2028 will be powered by LNG, even though currently only about 6% of the 300 existing cruise ships operate on LNG. The latest cruise ship designs are versatile, accommodating traditional marine gas oil, LNG, or alternative fuels like bio-LNG, although these alternatives make up only a fraction of U.S. fuel consumption.
Written by Alius Noreika