Carnival Corp. (CCL) - Get Report has started construction on the first of seven cruise ships that will run entirely on liquefied natural gas, the world's cleanest burning fossil fuel, the company said in a statement recently.

The ships will be the world's first to run entirely on LNG and will be delivered between 2018 and 2022. The LNG innovation will reduce exhaust emissions, in line with what Carnival calls "aggressive" sustainability goals.

The LNG-powered ships will source fuel from Royal Dutch Shell PLC-owned (RDS.A) Shell Western LNG B.V. Carnival's AIDA brand released ships in 2015 that used LNG hybrid barges and LNG in a dual-fuel powered engine while at port, but the new ships will be the first to use 100% LNG both in port and at sea.

The new fleet is under construction by German and Finnish shipbuilders Meyer Werft and Meyer Turku. Carnival, which is the world's largest leisure travel company, celebrated the ceremonious start of construction on the ship with a keel-laying ceremony in Hamburg this week.

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The first of the seven ships will go to Carnival brand AIDA Cruises and is set to be christened as the AIDAnova next fall. The next ship to complete construction will go to Carnival's Costa brand in 2019. Carnival will get its first LNG-powered ship in 2020, followed by another in 2022.

"We are committed to continuing to reduce air emissions and improving air quality by evaluating both new and established solutions, including LNG," Carnival CEO Arnold Donald said.

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