
An overview – in plain English – of the biggest sustainability problems with cruise ships, and some solutions for how to fix them (from interviews with experts).
Among other foiled travel plans this year, I had scheduled a dreamy sounding trip in Mexico with UnCruise, a company that bills itself as a sustainable alternative to big-ship cruising.
So I started researching: What does it mean to be an alternative to cruising? An alternative to what, exactly?
For starters, what I had planned with UnCruise was to be a week-long sailing trip in a small corner of the Sea of Cortez, with sustainably-caught, local seafood, and farm-to-table (or farm-to-boat) fruits and veggies. There were going to be shore excursions for interpretive desert hikes and horse-back rides among the cacti of Baja California. And only 100 people on the boat, 30 of them crew.
I’ve never been on a “normal” cruise, but this didn’t sound anything like one.
If you keep up with the sustainable travel world, you know it’s sort of a trope to hate on big cruise ships.
We know cruise ships are dirty. They pollute… but how, exactly? And how much? Is cruising really as bad for the environment as they say?
That’s what I wanted to learn before my “alternative cruise” trip. But, 2020 being what it was, of course the trip had to be canceled.
So I want to share what I’ve learned about pollution, environmental problems, and sustainability in the cruise industry – so that you have the information before we start booking vacations again.
(I’m hoping to be able to reschedule my trip with UnCruise in 2021… or 2022, and of course I’ll report back on how it goes!)
Is There Such a Thing as Sustainable Cruising?
UnCruise supposedly offers a sustainable way to travel. Or at least a more sustainable way to cruise. Which, according to 99% of what I’ve heard about the cruise industry, doesn’t really set the bar very high.
But there are better and worse ways to do everything. An idea I keep coming back to in lots of posts on this blog is whether one company can be meaningfully different, especially in a dirty industry – and of course, I think the answer is clearly YES!
For example: Do LastObject’s reusable Q-tips and cotton pads really make a difference in how wasteful our toiletries are? Do electric cars really make a difference to the climate impact of driving? (Coming soon!)
And is UnCruise really greener than any other cruise company on the high seas?
To answer that question, I want to establish a baseline (what is normal for sustainability in the cruise industry? What are the problems?) so I can understand if any one company is doing better than the rest. This article will be that baseline.
And in a future post, I’ll get into what UnCruise does to be more sustainable. (I’ll add a link here when that post is up!)
Why Cruising Has a Bad Reputation
There’s a lot more to it, but if you don’t take anything else away from this post, these are the major sustainability issues with cruise ships:
The most famous is probably dumping grime into the ocean – both untreated sewage and oil. But even worse is that many cruise ships burn really dirty diesel fuel, including when they’re docked at a port, which releases tons of greenhouse gases and creates air pollution in port cities. (Of course, they create the same pollution out at sea, but it’s more noticeable at port.)
Who’s Reporting on Cruise Ships?
An environmental group called Friends of the Earth (FOE for short) writes a detailed “cruise report card” every year that ranks the big cruise companies from cleanest to dirtiest. And those are the main factors they look at: How well they treat sewage, where they dump it (and if they do so legally, which many don’t), and what they do to minimize air pollution. (Plus, FOE considers whether or the not the companies are transparent in replying to their questions.)
Here’s the 2020 report card. And here you’ll find every report card, starting in 2009. You can even look up the performance of individual ships, because they’re all different, even when they’re owned by the same company.
A lot of the info in this post is from conversations I had with two very helpful cruise ship experts at FOE – John Kaltenstein and Marcie Keever. (Marcie is FOE’s Legal Director, and Director of the Oceans and Vessels program, and John is that program’s Deputy Director.)
Basically, I picked their brains to break down, in plain English, what the ratings in their cruise report cards actually mean. Here’s an overview of the problems:
Cruise Ships and Sewage
Ugh, I hate to start with the gross and surprisingly complicated part, but it’s important.
The sewage issue is really about two questions: How well ships treat it (if they even do treat it), and where they dump it.
Treatment
FOE ranks how well ships treat sewage by whether or not they’ve installed the latest “advanced sewage treatment systems.” There are two kinds of sewage: “black water” is from toilets; “gray water” is everything else – from laundry, dish washing, sinks and showers. The treatment systems are for both because, as John told me, around 95% of a ship’s sewage is gray, and gray water can be as toxic as black water, with similar polluting nutrient and bacteria content.
When they’re dumped in the ocean, those nutrients and bacteria cause oxygen depletion, and toxic algae blooms – which cause ocean dead zones. And they spread bacteria and viruses, which means anyone eating seafood from areas where cruise ships have dumped can get sick. Plus… gross.
But if ships do proper treatment, with advanced systems, then the water they’re dumping is cleaner than the tap water in most US cities. (Although it still could have other problems, like containing metals that kill baby salmon in Alaska.)
John also said the “non-advanced” systems are pretty rudimentary and basically don’t do very much at all. Yet only about 60% of cruise ships have the advanced treatment systems. That’s progress, but John said there’s no excuse for it not to be 100%.
“These are billion-dollar-plus ships – this is a small fraction of the cost. Considering the harm sewage can do, and the pristine nature of a lot of the places these ships are visiting, it’s pretty much a no-brainer. It’s kind of shameful that they’re not all equipped at this point.”
John Kaltenstein
Dumping (The Really Gross & Complicated Part)
Want to know the most disgusting and shocking thing? If a ship is more than three nautical miles from the US coastline, it’s allowed to dump ANY sewage, WHEREVER it wants.
That means cruise ships regularly dump hundreds of thousands of gallons of human waste. The biggest ships can carry 9,000 people, and all of their untreated sewage is dumped into the ocean, just three miles from land. (Three nautical miles = 3.5 normal miles, or 5.5 km.)
It’s so complicated because the rules depend on the country and state. Three nautical miles is the general rule in the US. Some countries extend it to 12, but with even weaker treatment standards. And most countries don’t have any regulations for gray water treatment or dumping – but remember, gray water is just as toxic as black water!
Even after I wrote all of that, I just couldn’t even believe it was possible. So I checked it with Marcie. She confirmed:
“This is true – there are no rules in the US beyond three nautical miles, except in a few places like the National Marine Sanctuaries in California and all of Puget Sound, Washington, for example.”
Marcie Keever
Plus, almost all ships break the rules, anyway. (Carnival Corporation is currently on criminal probation, along with all the cruise brands it owns, for repeatedly dumping raw sewage and lying about it.)
This is why it’s so important that cruise companies install the right treatment systems! If it’s treated properly (with an advanced treatment system) then it’s not nearly as big of a deal where it gets dumped, because it’s basically tap water.
But if they don’t do proper treatment, sadly, all they have to do is go a few miles from shore to legally dump it.
Alaska has the strictest regulations in the world for cruise ships and sewage.
That’s why complying with Alaska’s rules is one of the categories that FOE grades cruise companies and individual ships on. If the company applies for a permit to dump sewage within three miles of Alaskan shore, then they’re graded on whether or not the Alaskan government cited them for any violations.
But the problem is, if they just don’t apply for a permit, and dump their sewage further from shore, then they’re excluded from this grading category – but they’re still doing huge environmental damage to delicate marine ecosystems that didn’t evolve to have all that human waste dumped on them.
Air Pollution from Cruise Ships
You made it through the confusing part! The air pollution issue is simpler than the sewage stuff (and there’s less about regulation).
There are three parts of the air pollution problem: Cruise ships burning dirty diesel fuel (way dirtier than what goes into a diesel car). Ships using “scrubbers” to cheat the regulations on burning that extra-dirty fuel. And whether or not ships can plug in to shore power – which lets them avoid burning the dirty fuel, at least while they’re docked at port.
The basis of all these problems is the diesel engines that power most cruise ships. (Some ships run on LNG – liquified natural gas – which is cleaner for air pollution, but actually worse for greenhouse gas emissions.)
Dirty fuel
Dirty diesel fuel is what Marcie said is the worst sustainability problem with cruising:
“Their fuel is thousands of times dirtier than truck fuel. It’s really the biggest problem with the industry right now.”
Marcie Keever
The dirty fuel means those big diesel engines on cruise ships emit tons of toxic smog that people on board and in port cities have to breathe. And they emit greenhouse gases, but the smog is the most visible problem, especially in port.
This might make you wonder: Then how clean is the air when you’re on a cruise? And the answer is not very. It’s at least as toxic as the air in the most polluted cities in the world.
Smoke Stack “Scrubbers” (A Way of Cheating)
“Scrubbers” are like filters that theoretically clean the bad stuff out of exhaust fumes as it comes out of a ship’s engines. (Imagine holding a wet sheet over a campfire. It would collect all the tiny pieces of ash that the smoke carries up into the air.)
International laws for dirty fuel have gotten stronger recently, but ships can just install scrubbers and be excused from following those laws. (And get out of buying the cleaner but more expensive fuel, which has lower sulfur content.)
The problem is most cruise ships clean their scrubbers with sea water – and often just dump that dirty filter water right back into the sea. (Marcie described it as, “acid sludge and waste water that are incredibly damaging to the ocean environment.”)
“They’re basically taking an air emission problem and making it a water problem.”
John Kaltenstein
Shore Power (A Reason for Hope!)
When a cruise ship (or any ship) is parked at port for a day, it keeps its engine running to provide electricity for everything on the boat – often a diesel engine.
Have you ever waited at a stoplight with your windows down next to someone driving a diesel truck? I’m from Montana, so I have. If not, you’ll have to imagine: It’s stinky and leaves a dark cloud in the air, and it’s so loud it’s hard to have a conversation.
“Shore power” is a simple-ish solution: Cruise companies retrofit ships to be able to “plug in” to electricity from land when they’re in port, so they can turn their engines off. And cities design their ports to allow this plug-in. Literally, these systems look like gigantic wall plugs.
It’s been done really well in some cities and on some ships – so we know it’s possible. Sometimes cruise companies even help cities pay for shore power (as Princess did with the city of Juneau).
But most ports still don’t have shore power. And since it’s not there, most cruise companies haven’t set up their ships to connect to it… Or is it the other way around?
Brooklyn is the only port on the East Coast that has shore power access. Out of about 30 cruise ships that dock there in a (non-pandemic) year, only half of them hook up to the cleaner shore power, which is totally absurd.
Even worse is that the Manhattan cruise terminal gets 180 ships a year, and has zero shore power. Charleston gets 100 ships a year and also has none.
“Carnival made a little over 3 billion dollars last year in profit,” John said, when we were discussing the situation on the East Coast. “This is the west side of Manhattan – there’s no reason there shouldn’t be shore power.”
Lots of European and Chinese ports are adding shore power for cruise and cargo ships. (China says it will require every cruise ship that has hook-ups to use shore power by 2021, and will require cleaner fuel.) Even tiny Malta is doing it.
But most of the US is way behind – maybe because everyone’s bickering over who should make the upgrades first. For example, Miami – obviously a massive hub for cruise ships – just redid their ports without adding any shore power hook-ups.
And Everything Else:
So those are the main problems (dirty sewage, dirty fuel, and lots of ways for cruise ships to break the laws). And I know, it was a lot. But there’s more.
There are lots of sustainability problems with cruising that FOE doesn’t report on: Like cruise ships causing floods of over-tourism in the ports where they stop, totally overwhelming local life without adding much to the local economy. The egregious use of single-use plastic. Food waste. Engine efficiency. Greenhouse gas emissions per passenger per mile.

Marcie and John both said these are also really important issues, but they’re just much harder to measure. The information simply isn’t available to create a fair grading system for plastics, CO2 emissions, food waste and other problems.
Sustainability Improvements… Maaaybe?
I was searching for a silver lining, so I asked John if there were any companies he thought were truly better than the rest and he said he really just doesn’t trust any of them.
Still, I can’t say the cruise industry is totally evil – there are a lot of improvements happening. And just like with airlines, and every other industry, there are huge differences from one company and the next.
But a lot of the improvements I’ve read about sound more like companies trying to cut costs and look good than meaningfully improve their environmental impact. (A slimy practice called greenwashing, which I talk about more in this post.)
Some examples: Replacing throw-away shampoo bottles with refillable dispensers. Yes, single-use plastic is totally an issue, but it’s not the biggest problem in the cruise industry – dirty fuel is. But that’s more expensive to fix.
Or reducing the portion sizes at meals “to reduce food waste.” Yeah, sure – reducing food waste is a bonus. But why should we believe that they’re cutting portions for any reason other than to save money?
Win-win improvements are great, and I totally believe that people and brands deserve to do well for doing good (that’s why I’ve been writing all these reviews of brands that make plastic-free cleaning products and toiletries with non-toxic ingredients).
But the majority of cruise companies only make the changes that save money, and skip the ones that cost money – but which would do the most good for the environment.
So it’s clear that they’re not the ones innovating on sustainability.
When companies make changes that actually cost them money, we can all see that they’re doing it for the right reasons.
Stay tuned for more on this topic! Including about sustainability initiatives (the non-money-saving kind) and which cruise companies are better and worse. If there’s something else you want answered, let me know in the comments!
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