ANTARCTICA - The cruise industry, long criticized for polluting the environment, is slowly trying to go greener by exploring new technologies, from hybrid solutions to high-tech sails.
Cruises get a bad reputation for their climate footprint and even more for the air pollution they generate.
Most cruise ships run on heavy fuel, which is cheap but full of harmful substances -- such as sulphur oxide, nitrogen oxide (NOx) and fine particles -- that increase the risk of respiratory and cardiovascular disease.
The use of heavy fuel is currently permitted everywhere except in Antarctica.
Some 203 cruise ships in Europe generated more than 10 million tons of CO2 emissions in 2017 -- the equivalent of the annual emissions of Luxemburg or Cyprus -- according to a report by campaign group Transport & Environment.
Their study also said the ships spewed 20 times more sulphur oxide than the 260 million cars on Europe's roads.
While some progress is being made, it is slow going.
"Only a small proportion of fleets is becoming cleaner, while the industry by large continues to rely on heavy fuels and fails to employ exhaust technology," German NGO Nabu said in its 2019 ranking of cruise ships by air pollution and climate emissions.
Sulphur levels allowed in ship fuel will be reduced from 3.5 percent to 0.5 percent under new International Maritime Organization rules from Jan. 1, 2020.
In some areas, like the North Sea and the Baltic Sea, the maximum level authorized is already 0.1 percent.
Norwegian company Hurtigruten launched the world's first hybrid diesel-electric cruise ship, the Roald Amundsen, this summer equipped with two lithium-ion battery packs that complement its four diesel engines -- similar to a Toyota Prius.
The batteries provide the necessary energy to meet peaks in demand without having to start another engine and reduce both fuel consumption and CO2 emissions by 20 percent, according to Hurtigruten.
French shipbuilder Ponant has opted for a hybrid with dual-fuel LNG/battery propulsion for its icebreaking cruise ship Le Commandant Charcot, due to be finished by 2021.
The ship, which will sail to the geographic North Pole, will be zero-emission in electric mode, which it can do for a few hours.
When running on LNG, CO2 emissions will be reduced by 25 percent, nitrogen oxide by 85 percent and fine particles by 95 percent, according to the company. Like Hurtigruten, Ponant voluntarily stopped using heavy fuel on its fleet this year.
The full-gas behemoths Aida Nova and Costa Smeralda top the Nabu ranking.
Owned by Italy's Costa Cruises and its German subsidiary Aida, the two cruise ships were launched in 2018 and 2019 and can each carry 6,500 passengers.
They are the first to run entirely on LNG, which means they generate very low levels of fine particles.
Several other companies have also ordered LNG cruise ships.
Numerous shipyards are looking to the past for inspiration, particularly sail power. Chantiers de l'Atlantique, a French shipyard, has developed a new sailing series named Silenseas.
It reduces emissions using a special kind of sail together with other clean energies, such as LNG and batteries.
Companies such as Aida and American Princess Cruises have decided to modify their ships so they can plug into electricity grids on land rather than running their engines, which is a major source of pollution in the harbours they visit.
While still rare, this type of land-based infrastructure is slowly gaining ground.
And MSC Cruises of Switzerland aims to become the first big cruise company to be carbon neutral by offsetting its emissions worldwide as of Jan. 1, 2020.