Dispatch, Mardi Gras du Carnaval: LNG 101: Travel Weekly
ON BOARD MARDI GRAS – Every Carnival Cruise Line ship since the first Mardi Gras in 1972 has sported a distinctive T-shaped funnel, and the last ship in the fleet, the 2020 version of Mardi Gras, is no different.
But in addition to the giant red and blue T-shaped funnel, the Mardi Gras has three smaller stacks. Painted white with a simple red stripe, these chimneys conceal vents for the three liquid natural gas tanks that make this vessel different from most others.
Compared to other Carnival ships, LNG engines add a different battery profile to Mardi Gras. Photo credit: Tom Stieghorst
Although there are a few cruise ships in Europe fueled by liquefied natural gas (LNG), Mardi Gras is the first ship to bring the innovative technology to North America. Cruise executives see a future in LNG as a cheaper, cleaner alternative to the traditional heavy diesel fuel that has powered passenger ships for the past 100 years.
Clean-burning natural gas offers great advantages over traditional fuel, especially now that cruise ships have had to drastically reduce the amount of sulfur emitted in their exhaust gases. Natural gas, which is primarily methane, does not produce sulfur dioxide when burned and much lower levels of nitrous oxide and particulate matter, two other pollutants from the combustion of fuel oil.
In addition, the supply of natural gas in North America is plentiful, making it cheaper to purchase on an energy equivalent basis than fuel oil.
Fit the bolt
Pretty scary. This is the verdict of Tom Stieghorst on the first roller coasters at sea.
Natural gas, however, requires special handling. It has to be liquefied to be a practical fuel, and that requires keeping it at a temperature of minus -259 degrees Fahrenheit. The three tanks built in the depths of Mardi Gras hold fuel at this temperature until it is ready to be burnt in the ship’s engines.
“These tanks are insulated as you wouldn’t believe,” said Rich Pruitt, vice president of environmental operations for Carnival, who was aboard Mardi Gras on its pre-inaugural cruise in July from Port Canaveral.
Pruitt said the tanks keep the gas so cold that it actually has to go through a warming process before ignition to be burned. A very small amount of gas evaporates naturally and must be vented to prevent pressure build-up, which is the purpose of the three additional chimneys.
Mardi Gras meal
Tom Stieghorst reviewed the new dining options at Mardi Gras, including Shaquille O’Neal’s restaurant and his massive chicken cookie for breakfast.
The quartet of school bus-sized 16-cylinder engines that burn natural gas are basically the same as those that burn diesel fuel. One small difference, Pruitt said, is that natural gas does not burn under pressure in an engine cylinder, so a small amount of diesel fuel is injected with each piston stroke to trigger combustion.
When burned, natural gas produces no visible emissions, none of the belching black smoke that many diesel engines generate when first started. “There is effectively nothing, there is no smoke, there is no fog. This is what LNG provides us,” said Pruitt.