How green is the cruise industry? Not very, say some. Getting better, say others.

In a recent New York Times article, Terry Dale, chief executive officer of the Cruise Line International Association, which includes 23 cruise lines representing 95 percent of the global cruise market, said, "Even in these tough economic times, we are forecasting that in 2009 a record 13.5 million people will take a cruise."

Cruising is a polluting industry. Some cruise ships carry more than 2,000 passengers and half again as many crew. They generate all the solid waste and sewage that you would expect from a floating village, as well as toxic chemicals from such activities as cleaning, painting, and photo processing. There's also the problem of oily waste and air pollution from diesel engines.

According to the environmental group Oceana, the average cruise ship produces the following immense amount of pollution every day:

• 25,000 gallons of sewage from toilets;
• 143,000 gallons of sewage from sinks, galleys and showers;
• Seven tons of garbage and solid waste;
• 15 gallons of toxic chemicals; and
• 7,000 gallons of oily bilge water.

However, the cruise industry is making a growing effort to become more sustainable. In an article for G Living, Jennifer Buonatony wrote, "Over the past five years, the major cruise lines have spent an average of $2 million dollars per ship to upgrade vessels with better systems for dealing with waste management and emissions. And while the industry has grown 7.6% annually over the last decade, cruise ships have cut waste almost in half, which is an amazing figure."

Several cruise lines have been making serious efforts to clean up their acts. For example:

• Princess Cruises has modified its engines so that they can be plugged into onshore hydroelectric power while in port, which reduces the air pollution produced by idling ships.
• Holland America also has several ships that plug into shore power while in port and has installed a special seawater-scrubbing emissions system to reduce air pollution, as well as using a hybrid power system in its newer ships.
• Carnival uses eco-friendly detergents for dry cleaning and has developed a new, energy-efficient and nonpolluting engine for its newer ships.
• Royal Caribbean and Celebrity have dramatically reduced emissions of nitrous oxide and sulfur oxide by using gas turbine engine technology in their newer ships. Both cruise line are also installing Advanced Wastewater Purification systems on all their ships, and Royal Caribbean has made adjustments to its itinerary timings and cruising speeds to save fuel.
• Norwegian Cruise Line recycles thousands of gallons of used cooking grease by donating it to organic farmers in Hawaii and Miami.

Smaller cruise lines, such as Lindblad Expeditions and Adventure Smith Explorations, have also taken measures to be environmentally sound, such as offsetting their carbon footprint, purchasing seafood from sustainable sources, and adopting new sustainable technologies suitable for smaller vessels.

For more on the environmental initiatives of different cruise lines, see the G Living article or Melissa Baldwin's article on green cruising at Cruise Critic.

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Finally, Some Good News About Our Oceans
Sailing Cargo Ships on Solar Sails

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