American President Lines container ships calling regularly at Terminal 5 near Harbor Avenue Southwest are switching to low-sulfur fuel while in port to reduce air pollution.

The voluntary changeover to low-sulfur fuel while in Seattle is expected to reduce by 80 percent the amount of sulfur dioxide emissions from docked American President Lines' ships and 75 percent of their particulate matter. That adds up to approximately 30 tons less sulfur dioxide and 3.5 fewer tons of particulates in the air, said John Bowe, president of American President Lines' American section.

The company also began fueling its fleet of 71 yard tractors and 11 top picks with biodiesel.

Three months ago, American President Lines similarly converted 23 of its ships that regularly call at California ports.

The ship APL Coral ties up at Terminal 5 along the West Waterway of the Duwamish River. Equal to the length of three football fields, APL Coral's homeport is Singapore. The ship usually arrives on Thursdays, as it did last week, bringing 3,000 containers to the shores of West Seattle for transfer to trucks and rail cars, said Chew Englai, the ship's chief engineer.

As the ship sails toward West Seattle with its cargo, it is propelled by a 60,000-horsepower engine. But once it is docked at Terminal 5, the ship switches to any one of three 3,000-horsepower auxiliary engines, which generate the ship's electrical power while longshoremen unload and load shipping containers.

An auxiliary engine burns about 100 gallons of fuel per hour.

APL Coral stays in West Seattle for about two days each visit before sailing off to other ports. Five APL container ships come to Seattle on a regular basis.

Marine diesel emissions include 40 polluting substances, said Dennis McLerran, director of the Puget Sound Clean Air Agency. People inhale particulates that can lodge deep in the lungs, he said. Other pollutants contribute to acid rain.

Students from the University of California-Irvine will conduct follow-up studies to measure the effects of the company's switch to cleaner fuel.

While biodiesel seems to be a good alternative for auxiliary engines, the shipping industry must turn to petroleum fuels to sail the oceans. So far, there isn't enough biodiesel being produced to meet the heavy demands of the shipping industry.

Tim St. Clair can be reached at timstc@robinsonnews.com or 932-0300.