A little clean air to go with that sunshine and sea breeze?

For many American families, taking a cruise is a dream vacation: sailing on the open sea, playing on beautiful beaches, and leaving ordinary life behind. About 10 million Americans board cruise ships bound for Alaska, Hawaii, or the Caribbean each year [PDF], making North America the largest cruise market in the world. Three times as many cruise passengers depart from North America as from all other regions combined [PDF].

The seemingly insatiable demand for cruise travel has fueled tremendous growth in a number of cruise terminals along US coasts. One of these is the Port of Miami, recognized for many years as the “Cruise Capital of the World.” (Miami’s cruise terminal is growing in part at the expense of other ports, as cruise ships are redeployed there.) According to the Maritime Administration, between May 2011 and March 2012 over six hundred cruise ships carrying about two million passengers sailed from Miami to a number of destinations in the Caribbean. The industry collectively earned about $30 billion in gross revenue in 2012 from the North America market, riding a wave of economic recovery and a series of tax breaks that were enjoyed by cruise lines.

An often overlooked factor in the success of the cruise business is the failure to account for and internalize its environmental costs. Cruise ships are often equipped with colossal diesel engines [PDF], which provide not only propulsion for the ship but also power for onboard activities. The engine output from a 3000-passenger cruise ship can total 50,000 kW, enough to power 28,000 residential homes. Even in port, operating at a fraction of full capacity, those engines still generate the energy equivalent of 70 diesel-powered SUVs operating at full speed. Not only are these diesel engines huge, they also use cheap, dirty fuel. Before August of last year, cruise ships operated on high-sulfur heavy fuel oil (HFO), a refinery residue with sulfur content as high as 35,000 part per million. For comparison, since 2007 the sulfur content of the diesel used in road vehicles is 15 ppm. Emissions from cruise ships of sulfur oxides (SOx), which cause acid rain and soil degradation, and PM10 emissions, particles with an aerodynamic diameter of 10 micrometers that are small enough to penetrate deeply into the lung and cause various respiratory diseases, dwarf those of on-road transportation. The emissions from cruise ships idling outside of the Port of Miami between May 2011 and March 2012, for example, equaled those of about 24,000 diesel-powered light-duty vehicles running 15,000 miles per year.

To alleviate the environmental impact of oceangoing vessels, the US Environmental Protection Agency (EPA) required all ships operating in US waters to burn cleaner fuels beginning August 1, 2012. The mandatory sulfur cap in the so-called Emission Control Area (ECA) is set at 10,000 ppm (1%) between 2012 and 2015, and 1,000 ppm (0.1%) after 2015. While the 2015 sulfur level will remain hundreds of times higher than for on-road diesel fuel, the ECA still represents a remarkable improvement for international shipping, an industry traditionally without regulatory oversight. If cruise activity grows 5% a year and the ECA is implemented as planned, PM 10 emissions from cruise ships berthed in the Port of Miami would be reduced by some 60 tons in 2012, and by 75 tons in 2015 That’s equivalent to taking 16,000 light duty vehicles off the road in 2012, and 20,000 in 2015.

The EPA forecast [PDF] that the cost of the marine gas oil (MGO) needed to meet the 2015 requirement will be 40% higher than high-sulfur HFO. Calculated from the data published by the Cruise Lines International Association, the higher fuel price would translate to a $10 per day increase in ticket prices. That seems like a reasonable price to pay for clean air to go along with the scenery.