In Miami, cruise ships turn off their engines and plug in to help the environment

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Miami, the world's busiest port for passenger traffic, has taken a big step to reduce pollution from cruise ships. It spent $125 million to build and launch a shore power program. That allows cruise ships to turn off their engines and plug into the grid while docked, reducing emissions by more than 95%. NPR's Greg Allen reports it's the largest shore power system on the east coast.

GREG ALLEN, BYLINE: Shore power for cruise ships isn't new. Juneau, Alaska, in partnership with Princess cruise lines, has had it for more than 20 years. All west coast ports have it. In California, by 2030, all cruise ships and cargo vessels will be required to plug in while in port. But shore power has been slow to come to the east coast. That's why at dock side in Miami, Deputy Port Director Frederick Wong was proud to stand next to a 14-story tall cruise ship tethered to a giant extension cord.

FREDERICK WONG: This is our first one - Carnival Conquest. She successfully ran her power last week.

ALLEN: Nearly 5,000 passengers and crew are on board, ready for a short trip to the Bahamas. Cruise ships are typically in port for nine or 10 hours while they exchange passengers and reprovision. Their huge diesel engines, powering everything from their lights to air conditioning, run the whole time and emit exhaust that adds to Miami's air pollution. But Wong says now at five of Miami's cruise terminals, ships can plug in.

WONG: When the vessel comes alongside, that's when she ends up turning off her vessel engines, and then she goes completely off of our local grid.

ALLEN: The largest cruise ships are akin to floating cities and can use up to 16 megawatts of power while in port. At a ribbon cutting, Miami-Dade County's Mayor Daniella Levine Cava said plugging them into the grid will significantly improve Miami's air quality.

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DANIELLA LEVINE CAVA: Just one terminal going to shore power is the equivalent of taking 7,500 cars off the road.

ALLEN: Levine Cava is the person most responsible for bringing shore power to Miami's cruise port. It's an idea she first discussed with the port's director nearly a decade ago.

LEVINE CAVA: When I was a county commissioner and I broached the idea, I was told that the cruise companies were not interested, so it was really top of my agenda when I came in as mayor. And it was like something had flipped a switch. They were all in.

ALLEN: The cruise industry has been under fire for years now from environmental groups and others concerned about the impact these floating cities have on air and water quality and on the communities that they visit. Two years ago, the major cruise lines signed onto a pledge to reduce their carbon footprint to net-zero by 2050.

KELLY CRAIGHEAD: Part of that pathway to get to net-zero emissions by 2050 has to be with shoreside electricity capability.

ALLEN: Kelly Craighead is the CEO of the industry's trade group, the Cruise Lines International Association. She says the industry is sensitive to criticism that cruising is bad for the environment and is working to address it.

CRAIGHEAD: Our cruise line leaders have a sincere commitment to sustainability, and they're not just saying it. They're putting billions and billions of dollars behind it. And I think it's important for not only policymakers, but also consumers to feel good about the choices that they're making.

ALLEN: An environmental group, Friends of the Earth, issues an annual Cruise Ship Report Card. Most cruise lines typically receive Ds or Fs. Marcie Keever, who helps compile the annual score card, is a big fan of shore power, but says Miami is late to the game. She says east coast ports need to follow the example of places like Seattle and California that are now requiring cruise ships to plug in while docked. And a lot more needs to be done, she says, before the cruise industry can claim that it's sustainable.

MARCIE KEEVER: The CO2 footprint alone is eight times higher for a cruise vacation than a land-based vacation. That's really, really disturbing because the industry keeps talking about how much they're reducing their CO2 footprint, and yet it's still eight times higher than that of a land-based vacation.

ALLEN: In Miami, cruise ships are a vital part of the region's tourist economy. Last year, more than 7 million people left from terminals that are walking distance from the city's downtown, a downtown where the air now will be a little bit cleaner.

Greg Allen, NPR News, Miami. Transcript provided by NPR, Copyright NPR.