The cruise industry thrives on dreams: It offers a chance to see pristine shores and exotic locales while providing an escape from the reality of everyday life.
But some of the industry's side effects make travelers uneasy and antipollution groups unhappy.
The largest ships, which hold more than 6,000 passengers, can burn nearly 100,000 gallons of fuel a day and generate the same amount of sulfur dioxide fumes as 5 million cars, environmental organizations say.
Some of those dreamy locales have suffered consequences because of their popularity with cruise companies. In Venice, Italy, large ships have been banned because of the air pollution and number of tourists they bring to the city.
Other bans have occurred in Norway and Antarctica.
"Seventy percent of cruises take place in sensitive biodiversity hot spots in the Caribbean and Alaska, and environmental monitoring is notoriously difficult,” said Martha Honey, executive director of the Center for Responsible Travel, based in Washington, D.C.
“Cruise ships have typically burned bottom-of-the-barrel bunker fuel, which is what remains of crude oil after gasoline and distillate fuel oils are extracted. These dirty fuels release elevated levels of a number of noxious gases when burned, including many known carcinogens.”
But change is coming. New regulations, coupled with a building boom in the cruise industry, is ushering in greener and cleaner technologies.
A detailed special report issued in November by Cruise Industry News chronicles changes that have affected the industry in the past two decades and will increasingly restrict it in the future.
"Zero emissions is the cruise industry's long-term ambition, both for water and air, and not only at sea but also in port," according to the “2019 Zero Emissions Target Report” study.
The International Maritime Organization and other groups are mandating that new ships be 20% and 30% more energy efficient in 2020 and 2025.
"New ships are well on their way to meeting these targets already…. New developments also promise to turn garbage into energy that can be burned as fuel rather than being incinerated."
Another factor, the report continues, is that port communities are becoming more concerned about air emissions from cruise ships. Norwegian authorities, for instance, are requiring that their heritage fjords, which are popular with cruise ships, be emission-free by 2025.
"Cruise lines may someday get to zero emissions," said Oivind Mathisen, editor and publisher of Cruise Industry News. "It may not happen in our time, but the technology that's out there is fascinating."
One of those technologies is liquefied natural gas, or LNG, among the most popular alternative fuels.
Carnival Corp. has 11 LNG-fueled ships on order, including ships for its brands Princess, Carnival, Costa, P&O and its German brand, Aida cruises. The AidaNova just made history by becoming the first cruise ship to be powered by LNG while both at sea and in port.
Carnival Cruise Line's first LNG ship is due to launch in 2020 and will become one of North America's first LNG ships.
"We’re proud of our role as an industry leader and to pioneer the use of LNG technology," said Christine Duffy, president of the line. “LNG has a variety of benefits that will support our efforts to continually minimize our environmental footprint."
But at least one industry pioneer isn't satisfied.
"The entire global cruise industry needs to give sustainability a much higher priority," said Daniel Skjeldam, chief executive of Hurtigruten cruise line.
Hurtigruten, with 17 ships, is one of the world’s largest expedition cruise operators and sails primarily in environmentally sensitive areas such as the Norwegian fiords, the Arctic and Antarctica.
"We have an obligation to take care of our resources, both land and ocean, in the best possible way,” he said. “The industry must commit to building new ships and older ships need to be converted to a much more efficient level."
Hurtigruten has three hybrid electric-powered ships on order, due to go on line in 2019, 2020 and 2021.
“These are greener, more advanced cruise ships than the world has ever seen — and ships that will raise standards for the whole industry to follow,” Skjeldam said.
What can cruise passengers do to help raise the environmental bar?
Before booking a cruise, said Honey of the Center for Responsible Travel, “travelers should look at the environmental scorecard ratings done periodically by the nonprofit organization Friends of the Earth.