Portland will soon be visited by the largest cruise ship it’s ever hosted. Do you know what kind of impacts these behemoths with their thousands of passengers have on our environment? We didn’t either, so we asked:

On Aug. 28, the biggest cruise ship ever to visit Portland is due to dock at the Ocean Gateway at 8 a.m. The Anthem of the Seas, which sets sail on its first American voyage on Aug. 25, is 1,140 feet long and is slated to carry 4,974 passengers and a crew of 1,480.

That’s roughly the population of Belfast contained in a boat nearly four football fields long and equipped with a viewing pod that rises so high off the deck that passengers will be able to look down on the Portland Observatory on Munjoy Hill. (The city had to check with the Federal Aviation Authority to make sure this didn’t interfere with flight plans at the nearby Portland International Jetport.) The ship will be in town only about nine hours, but that ought to be enough time for a lot of double takes.

And questions.

In a town so focused on sustainability that it has competing composting companies and a public housing project with a rooftop garden, some residents are likely to wonder just what kind of environmental impacts wash ashore with a giant ship like the Anthem of the Seas.

Worldwide, cruising is on the rise, with 24.2 million people expected to go on cruises in the course of 2016, up 4.3 percent from 2015. In Maine, Portland has become an increasingly popular destination for cruise lines – Bob Leeman, the marketing manager of Cruise Portland, said the city is scheduled to receive 104,000 visitors from cruise ships this year, up about 10 percent from the previous year.

It’s only natural then to ask what impact these ships have on our marine life, the waters of Casco Bay, the local food economy and environment and whether the economic benefits of selling T-shirts and lobster rolls to some very short-term tourists balances out the carbon footprint of ships so big they make the Time and Temperature building look dainty.

Some of the answers are surprising.

For instance, the average ship size is increasing all the time, a factor driven by the simple capitalism involved with the cruise ship industry.

“You can operate a ship as effectively for a larger number of people with a relatively smaller capital expenditure and a less than proportional increase in cruise size,” said Bud Darr, senior vice president, Technical and Regulatory Affairs, with Cruise Lines International Association.

But a huge ship like Anthem of the Seas isn’t, relatively speaking, more of a sea-bound gas guzzler, because the newer the cruise ship, the more energy efficient it is likely to be, according to both the industry and some of its critics.

“We are going to continue to see a more and more efficient generation of ships,” Darr said. “It is not only good for the environment, but let’s face it, we pay for our fuel.”

Anthem of the Seas was completed in 2015 and is one of Royal Caribbean’s “quantum” class of ships. Royal Caribbean has already built a bigger ship, the Harmony of the Seas; the size just keeps growing.

But Darr said so do the energy efficiencies. The industry expects to reduce emissions by 30 percent by 2025, aided by improvements on new and as yet unfinished ships. LED lighting has been a huge help, Darr said, as well as improved heating and cooling systems. About 20 of the 300 oceangoing cruise ships in the world are managing waste on board to the point where “nothing actually goes to a landfill,” he said. Most ships have on-board incinerators that cut back on the amount of waste returning to shore with passengers (although incinerator emissions come with hazards of their own).

What does return to shore in terms of waste, typically? A lot of squished packaging. Ships’ provisioners don’t shop the way we do: they take nothing extra on board, and any leftover materials are compressed to be returned to shore and recycled at the end of the voyage.

Darr said it is “typical to see a 60 percent recycling rate per person, which is better than recycling rates onshore.”

One of the ways the industry avoids burning more fuel is by minimizing the distance between ports of call; an itinerary that calls for a stay in Boston one night and Portland the next, for example, means the vast ship spends less time getting up to maximum speed on a journey. Portland expects 28 cruise ship dockings, large and small, just in September.

So is Portland, a relatively new port of call for the industry, compared to, say, the Bahamas, a cheap pit stop? Darr had plenty of flattering things to say about Portland and its appeal to cruise passengers.

“What I will say is those ports that are closer do have some appeal with regard to energy efficiency,” he said. “The main driver is going to be, what is the guest experience there?” What Portland offers to cruise ship passengers is “great,” he said. That list includes sightseeing, trips to Freeport to shop L.L. Bean and the outlets, bus trips to Mt. Washington to enjoy the foliage, and pursuit of local foods, including lobster in all its shapes and sizes.

NO-DISCHARGE ZONE

Some people look at a cruise ship and see nothing but temptation, a birthday cake of a boat ready to deliver a dream vacation. Then there are those like Cathy Ramsdell, executive director of Friends of Casco Bay, who would recoil on drives through Acadia National Park when she’d look down and see cruise ships in Frenchmen’s Bay. “It just seemed wrong to me,” she said. “It was one of the most offensive sights I have ever seen, dwarfing those islands.”

When the cruise ship industry increased its focus on Portland as a destination after the turn of the century, Friends of Casco Bay worked in tandem with state Rep. Herb Adams, who sponsored legislation to make Casco Bay a No Discharge Area, or NDA. That means ships are not allowed to dump even treated wastewater within three miles of the shoreline from Small Point to Two Lights. Not gray water (from showers and sinks) or black water (untreated sewage) or oily bilge water.

At times, Ramsdell said she was terrified it wouldn’t pass. “There were some very big guns there,” she said, referring to the attorneys for the cruise ship industry. The threat that the industry would simply go elsewhere (taking with them those tourists buying T-shirts) was implicit.

“It was a real David and Goliath effort and it involved legislators who leaned in from both sides of the aisles,” Ramsdell remembered.

That protective zone victory, which took effect in 2006, led to other regions in Maine being added to the no-discharge list. Boothbay, Kennebunk to Wells, southern Mount Desert Island and West Penobscot Bay were added in 2009. (It’s worth noting that all of Connecticut’s and Rhode Island’s coastal waters and all waters in New Hampshire are no discharge zones.)

If it hadn’t happened, Ramsdell said, “we would be wringing our hands every time we saw those ships coming and going.”

This relatively early action made Maine something of a hero among the sector of the environmental community that focuses on cruise ships. Ross Klein, a professor from Newfoundland whose website Cruise Junkie tracks the industry with watchdog ferocity, said the story of Portland and cruise ships is cause for celebration.

“Because of these good environmental activists, the nature of the problem that you are going to experience is considerably less than other ports,” Klein said.

Further protections were put in place by the Environmental Protection Agency, first in 2009 and then in 2013, which go beyond the No Discharge Areas established in Maine and elsewhere. But black water, ie toilet waste, can still be dumped outside of those three miles, a cause of concern for some. So too are those possible mistakes made within the three-mile protected zone.

“Every once in a while we’ll get a call from a citizen who says, ‘There is a ship in town and it doesn’t smell right,’ ” Ramsdell said. “And we’ll check it out.”

But about all Friends of Casco Bay could do in that case is buzz by in the Baykeeper and then give a call to the U.S. Coast Guard, which is in charge of enforcing such regulations on cruise ships.

WHO YOU GONNA CALL?

The cruise ship industry is heavily regulated by multiple entities, but it falls to the Coast Guard to respond to problems and conduct at least two scheduled inspections annually and up to four depending on the situation.

In Maine, which is part of Sector Northern New England, three inspectors are qualified to inspect cruise ships. One of them is Lt. Mike Metz, now stationed in Portsmouth, New Hampshire, but a veteran of the cruise ship inspection process, having spent six years in Miami and Fort Lauderdale, including three years in the Coast Guard Cruise Ship National Center of Expertise.

Metz explained these annual inspections happen at ports all over the country, but said in Maine, nine were performed in 2014, five in 2015, and two so far in 2016, with not yet half the cruising season completed.

That’s a small number compared to what happens in cruise ship hubs like Florida. But inspectors must be on hand in every sector.

“As complex as all these cruise ships are getting, it is crucial,” Metz said. “We may not have the volume but we certainly have the diversity.”

The inspections performed can range from testing the smoke extraction systems (fire protection measures) to seeing how the crew performs their jobs. The ship’s waste stream systems also undergo annual examinations, with the officer in charge choosing among the five types of systems – black water, gray water, oil, hazardous solid waste or non hazardous, aka, garbage – he or she wants to check. It takes a team of about four people an entire day to complete the examination, which includes checking all previous inspection records and consulting with officers elsewhere.

In the event a ship fails an inspection, the Coast Guard can hold it at port. That hasn’t happened in the two years Metz has been stationed in Portsmouth.

The Coast Guard is also there during the planning and building process. “These ships are examined cradle to grave,” Metz said.

But the ships aren’t, say, followed to the three miles out point to make sure they’re obeying the No Discharge Area rules, according to Lt. David Bourbeau, public affairs officer for the Northern Northeast sector. In the past, cruise ships have been known to break those rules, either by mistake or by willful neglect.

The Government Accounting Office tracked 87 cases of illegal discharges in U.S. waters from cruise ships between 1992 and 1998, the majority involving oil. Between 1999 and 2003, many of the major cruise lines were fined for environmental violations, including Norwegian, Carnival and Royal Caribbean (which was assessed millions in fines). This led to a requirement by the Cruise Lines International Association – the group Darr represents – that its members adopt more stringent waste management practices and procedures.

“Obviously there have been a few violators,” Bourbeau said, “but I think they have way too much to lose to not follow the rules.”

Not everyone is willing to trust that the cruise lines have been scared straight. In Alaska, which has decades of experience with the cruise industry, a state-run group, the Ocean Rangers, provides another layer of protection from environmental problems. The program is funded by a tax on cruise ship passengers. Klein of Cruise Junkie is a proponent of Ocean Rangers, and he’d recommend it for any community that worries regular inspections aren’t enough. Or that trust hasn’t been earned yet.

“It’s kind of like the police saying, ‘We don’t have to patrol the highways because people aren’t stupid enough to go 120 miles per hour,’ ” Klein said. “We have lots regulation but not lots of enforcement.”

Metz wouldn’t argue against the presence of Ocean Rangers in Maine ports, were they to be added. “The more scrutiny any vessel can get is helpful,” Metz said.

Public scrutiny played a crucial role in pushing the cruise ship industry to improvements in wastewater treatment, to the point where these newer (and yes, bigger) vessels can handle human waste as efficiently as it is handled on land.

“They are building that into their design, which is a great thing,” said Pam Parker of the Maine Department of Environmental Protection. “That’s fabulous. These systems are equivalent to, or better, than some municipal systems that we have. They’re producing a very high-quality effluent.”

NEW DUMPING RULES

Still, effluent is effluent, and human waste contains nitrogen that isn’t good for any marine life, so concerns remain. Earlier this year the International Maritime Organization agreed to new regulations that will ban ships in the Baltic Sea from offshore dumping of any wastewater at all. If that becomes a trend in other world waters, either more port cities will have to be equipped to pump ships out or the technology on cruise ships will have to develop even further to treat and/or contain it.

Naval architecture technologies are moving at a fast pace, said the Coast Guard’s Metz, so much so that it can be a challenge for Coast Guard inspectors to keep up. Inspectors are regularly sent back to school to refresh their knowledge, Metz said, and even with his base of knowledge, he’s expecting more ship studying ahead.He’s not complaining. “I’m a nerd,” he said. “I dig it.”

He and others say they’d consider any ship built in the 1990s old. Klein said even a ship built before 2005 may not be up to good environmental standards. “There is a chance it doesn’t even have advanced wastewater treatment on board.”

By virtue of its newness, a giant ship like Anthem of the Seas starts to seem like a visitor that takes up a lot of room, but has a smaller environmental impact. Newer, nontoxic hull coatings that decrease the drag on ships and thus increase the fuel efficiency by up to 5 percent are also considered better for marine life. So too is the recent development of air lubrication systems that create a blanket of air bubbles around the ship in order to increase fuel efficiency. “It’s encouraging where it has been used,” Darr said.

Vibrations and engine noise interfere with marine life, particularly whales. That’s an area where the cruise ship industry is working on solutions, Darr said, not just to comply with international standards to protect sea creatures, but to keep its customers happy. “We do our very best on our ships to engineer out those sources of noises,” Darr said. “It is an extremely high priority for us. Our guests want to be comfortable.”

SHOW US THE MONEY

No one is proposing that Portland shut the door on the cruise ship industry. But what about the economic impact to the city? Does it pay off in tourist dollars or in say, purchases of local foods? The jury is out.

Studies by a pair of University of Maine professors and more recently, a 2015 survey conducted by a private research firm on behalf of Cruise Portland, a collaboration between the city of Portland and five other groups, put spending at anywhere between $85 and $105 per passenger who lands in the city. A small percentage take excursions on buses arranged for and upsold by the cruise ships. But most stay local, very local.

Earlier this month, when the Grandeur of the Seas came into port with 1,950 passengers, only eight buses were needed to take prospective shoppers to Freeport. Typically, the bulk of passengers (71 percent, according to the survey) explore the city by foot, buying lunch (lobster rolls are a popular item) and souvenirs. Cruise Portland estimates that in 2016, cruise ship passengers will contribute about $11 million to the local economy. Could it be more?

Maybe. Out of concern for air quality in this era of increased cruise ship traffic, Sierra Club Maine has been discussing a suggestion to require the cruise ships to plug into the local grid while they’re in port. That process, called cold ironing, would cut back on the air emissions involved with the ship running generators while on the dock to keep the lights and air conditioning on (being on the city grid still means using energy, of course, albeit from a different source). Currently, cruise ships don’t hook into the city grid, and technologically speaking, most couldn’t unless the city made major – and expensive – infrastructure changes at the piers, said Bob Leeman, marketing director for Cruise Portland. But most cruise ships do fill up with city water (which comes from Sebago) while in port.

“We run the hoses all day long,” Leeman said. “We’re making money on that. They can make their own water on board, because they have their own desalination plant, but (using city water) is cheaper than them doing it themselves.”

Maine is water-rich, even in a drought like this year’s, so that doesn’t raise sustainability alarm bells. It’s also rich in local foods. What about loading up on them to serve passengers on the day or days after the ship leaves Portland?

“That is a company-by-company decision,” said Darr of the Cruise Line International Association. It’s more common on smaller ships: “Where food can be sourced locally, they often like to do that. But the bulk of provisioning happens at the turn-around point.”

In 2012, U.S. Rep. Chellie Pingree wrote to owners of 15 cruise ship lines asking them to consider purchasing Maine lobster while in port here. Her request met with some success that season, with Norwegian agreeing to purchase 5,000 lobsters and Celebrity Cruise Lines 3,800. In 2014 Pingree’s office reported a total of 3,840 Maine lobsters going on board here.

American Cruise Lines, the smaller Connecticut-based cruise line that runs cruises along the Maine coast (its ships American Glory and Independence are due to dock in Portland six times in August) said in 2014 it purchased up to 40,000 pounds of Maine lobster annually from local lobster dealers. No one from the company was available to update those numbers.

But Annie Tselikis, the executive director of the Maine Lobster Dealers’ Association, which represents the majority of the state’s lobster dealers, said those numbers are “negligible.”

Tselikis said the combined Canadian and United States lobster industry moves 300 million pounds of lobster a year. “It’s a nice story. Good for the company and good for Rep. Pingree. Anything we can do to shed light on what a great product it is. But let’s call a spade a spade.”

Picking up lobsters in Portland doesn’t represent the reality of the industry, Tselikis said. For both the vendor and the buyer, the business operates most efficiently when lobsters are moved in bulk, through warehouses and via tractor trailers, she said. It might seem absurd for Maine lobster to be trucked to Boston, or New Jersey or some other location, to be loaded onto a cruise ship and then chug up the coast to be consumed after a day ashore in Portland, but because the cruise industry usually deals in such high volume, it makes sense, she said.

For one thing, much of the lobster served on board is likely to have been processed: frozen tails, picked meat ready for pasta dishes and so forth.

“If it is more efficient for them to receive it through a different distribution channel, then they will,” Tselikis said. “The cruise ship is going to do whatever makes sense for the cruise ship.”