By Tom Stieghorst

Carnival Corp. has reached an agreement with the U.S. Environmental Protection Agency to avoid using costly low sulfur fuels on 32 of its 102 ships.

The fuels are the main way the cruise industry is expected to meet stricter air pollution rules of the North American Emissions Control Area that take effect in 2015.

Under the agreement, Carnival will install exhaust scrubbers on the ships during a trial period, an alternate way to curb emissions of sulfur dioxide, nitrous oxides and particulates.

Carnival said it will spend $180 million to buy and install the equipment for some ships sailing for Carnival Cruise Lines, Holland America Line, Princess Cruises and Cunard Line. Which ships will get the technology has not been announced. Carnival has been testing a scrubber on Cunard’s Queen Victoria ship.

In addition to the EPA, the U.S. Coast Guard and Transport Canada support for the program, Carnival said. Armed with those key endorsements, it will now ask flag states that oversee various ships to allow the trial to proceed.

As part of the agreement, Carnival committed its ships to use shore power or less polluting marine gas oil for fuel while docked in U.S. ports.

Previously, the EPA had rejected a cruise industry proposal that would have let some ships burn high sulfur fuel as long as average emissions were lowered in a geographic area to meet the standard.

An agreement on the Emissions Control Area (ECA) is critical to cruise markets like Alaska, where cruises operate almost entirely within the 200 mile ECA zone, and costs for low-sulfur diesel can be double the charges for traditional fuel.