The Environmental Impact of Cruising

Cruise ships are one of the most carbon-heavy ways to get anywhere, worse per passenger than flying or driving, and that’s before you count the sewage, sulphur and noise that come with them. Not every operator is equally guilty, though. Pick a smaller ship, a smarter route or a line that’s actually put money into cutting emissions, and you can bring your own share of the damage down.

Below you’ll find the rules that govern emissions and waste, the promises the industry has made itself, and the parts brochures tend to skip over, discharges, fuel burn, noise, so you can decide for yourself whether to book or walk away entirely.

Minimal impact cruising: what the phrase actually means

Nobody hands out a certificate for this. “Minimal impact cruising” just means picking a ship, operator and itinerary that pollutes less than the average one. Sometimes that’s a small expedition ship instead of a floating city, sometimes it’s a line that’s put real money into shore power and modern waste treatment, and sometimes it’s simply fewer port days spread over a longer, slower trip.

If that sounds like your route, our guides to small ship cruising options and environmentally focused polar expedition cruises are worth a look, both carry a fraction of the passengers a mainstream mega-ship does.

Cruise ship carbon footprint: the numbers behind the headlines

Friends of the Earth puts it plainly: a cruise passenger produces around eight times more CO2 per day than someone holidaying on land. It’s a number that confirms what most people already suspected. Several sources trace this back to the same study, which puts the daily per-passenger figure at 421.43kg of CO2.

Scale that up and it gets worse. A single medium-sized ship, somewhere between 1,000 and 2,400 passengers, produces roughly the same CO2 as 12,000 cars over the same stretch of time, according to Friends of the Earth.

Global totals track the industry’s fortunes closely. OECD data, that’s the Organisation for Economic Co-operation and Development, compiled by Statista shows emissions dropped sharply during the pandemic-era travel restrictions, stayed low the year after, then climbed straight back up as passengers returned.

Cruise pollution facts: emissions per mile, compared with flying and driving

Even the biggest, most efficient cruise ships emit around 250 grams of CO2 per passenger-kilometre, according to the International Council on Clean Transportation (ICCT), higher than almost anything flying can manage. Aircraft typically sit somewhere between 10 and 130 grams per passenger-kilometre, and the longer the flight, the better the number tends to get.

Put another way, the ICCT reckons a passenger on even the cleanest cruise ship emits roughly double the CO2 of someone who flies to the same place and stays in a hotel. Swap a road trip for a cruise and the same research suggests you could more than double the carbon cost of your week away.

How much fuel does a cruise ship actually burn?

This is one question nobody has managed to answer with a single, tidy figure. Estimates of daily fuel use for a modern cruise ship are scattered and inconsistent from one source to the next, which makes a fair comparison hard for anyone trying to work out their own footprint.

The CO2 figures above are the best stand-in you’ll get, since fuel burn and carbon output are joined at the hip. A ship producing the CO2 equivalent of 12,000 cars, or emitting 250g per passenger-kilometre, is burning a serious amount of marine fuel by definition, whatever the exact daily tonnage turns out to be for that particular ship, engine, speed and route.

Air pollution: sulphur, NOx and the ports that feel it most

Cruise ships produced around 15% of the nitrogen oxide that Europe’s entire passenger car fleet manages, according to Transport & Environment data cited by GreenMatch. In one recorded year, just 57 ships docking in Marseille put out nitrogen oxide equivalent to almost a quarter of what the city’s 340,000 passenger cars produced between them.

Spain, Italy, Greece, France and Norway carry the heaviest sulphur oxide, or SOx, burden from cruise ships, mostly because they’re popular destinations with looser marine fuel standards than some other parts of the world.

Waste and sewage: what actually goes overboard

A large cruise ship can release around a million gallons of greywater, the runoff from sinks, showers and laundries, in a single week at sea, according to Marine Insight. The same week might also see around 210,000 gallons of blackwater, meaning human sewage, go over the side.

In the United States alone, EPA research has found cruise ships dump more than a billion gallons of sewage into the ocean every year, and Friends of the Earth has accused the regulator of not properly monitoring who’s breaking the rules. Blackwater discharge introduces pollutants into coastal waters that can trigger harmful algal blooms and strip out oxygen, creating “dead zones” where nothing can survive, according to Earth.Org.

Ballast water, taken on board to keep a ship stable and dumped somewhere else entirely, typically runs to around 1,000 metric tons per discharge, and it’s a well-known way of shipping invasive species from one region to another. On top of that, scientists estimate the industry discharges around 1.5 gigatons of scrubber wastewater, the leftovers from cleaning ship exhaust, into the ocean each year.

Cruise ship pollution effects on marine life

Engine and propeller noise disrupts normal behaviour in marine animals, according to Friends of the Earth, throwing off feeding, raising stress and drowning out communication between them. Whale calls have been recorded growing louder over the years, essentially the animals having to yell to be heard over the racket.

The Convention on the Conservation of Migratory Species (CMS) has flagged ocean noise as a potential threat to marine life in its own right, and a report cited by Earth.Org found it can push both predators and fish clean out of their usual habitats. Separately, cruise ships are behind the vast majority of scrubber discharge, which contributes to ocean acidification and can be toxic to marine life, according to World Wildlife Fund Canada, or WWF Canada, as reported by High Country News.

Cruise ship regulations: what MARPOL and the IMO actually require

The main rulebook here is MARPOL Annex IV, part of the International Convention for the Prevention of Pollution from Ships, overseen by the International Maritime Organisation, or IMO. It bans ships from discharging sewage within a set distance of land unless it’s been treated first, and it covers any ship of 400 gross tonnage or above, or certified to carry more than 15 people.

Ships covered by the rule need one of three things on board, an approved sewage treatment plant, a comminuting and disinfecting system, or a holding tank. A treatment plant certified to the IMO’s MEPC.227(64) standard is allowed to discharge treated effluent anywhere, any time.

The Baltic Sea is the only Special Area under MARPOL Annex IV with tougher discharge limits than the rest, and existing passenger ships sailing there now have to meet enhanced standards to protect this enclosed sea. The IMO has also banned heavy fuel oil outright in Arctic waters, and the European Union has started charging ships for their carbon emissions through its Emissions Trading Scheme.

UK and European rules: what applies to ships sailing from British ports

Most of the published detail on waste and emissions rules is written with the US or the EU in mind, and there’s no single, UK-specific summary of what applies to ships sailing from British ports. In practice, UK-flagged and UK-departing ships are bound by the same international framework, MARPOL and the wider IMO conventions, since the UK is a signatory in its own right regardless of its relationship with the EU.

It’s harder to pin down how much of the industry’s progress, shore power, emissions control area compliance, is actually happening at British departure ports specifically, rather than being folded into a global total. If you want ship-specific detail, you’re generally better off asking the line directly, or checking whether your departure port is one of those confirmed for onshore power supply.

Is the cruise industry getting cleaner?

Cruise lines say they’re working towards net zero by the middle of the century, in line with the IMO’s own strategy on shipping emissions, according to Cruise Lines International Association, or CLIA, the industry’s main trade body. CLIA member lines have also committed, fleet-wide, to cutting the rate of carbon emissions by 40% by the end of this decade, measured against an earlier baseline.

Onshore Power Supply, OPS for short, lets a docked ship plug into the local grid instead of idling its engines in port, and it can cut dockside pollutant emissions by up to 98%. OPS now reaches 147 ships, 52% of the CLIA fleet by capacity, a sharp jump from just a few years ago, according to CLIA’s Global Cruise Industry Environmental Technologies and Practices Report.

The catch is the ports. Only around 35 worldwide, fewer than 3% of the total, currently have a berth wired for OPS, though 22 more are funded and 16 are still on the drawing board. CLIA membership also requires lines to never discharge untreated sewage anywhere in the world during normal operations, treating it instead through onboard Advanced Wastewater Treatment Systems that CLIA says beat many coastal treatment plants on land.

How individual cruise lines compare

Friends of the Earth’s Cruise Ship Report Card ranks 21 major cruise lines and 243 individual ships against four criteria, sewage treatment, air pollution reduction, water quality and scrubber use, and transparency. Only two operators, Hurtigruten and Hurtigruten Expeditions, managed the top grade of B+.

Five lines, all under the Carnival Corporation umbrella, failed outright, and another eight scored a D. Carnival Cruise Line itself picked up an F for water quality and transparency, a D- for sewage, and a D for air pollution, which added up to an overall F for the brand.

It’s a useful independent benchmark, but it’s a US-centric list that doesn’t map neatly onto the ships UK cruisers actually book, P&O Cruises or Cunard don’t feature in the same way as the American brands do. The practical fix is to check whether your chosen line is a CLIA member, which brings the no-untreated-sewage and AWTS commitments above, and to just ask the line directly about scrubber use and OPS capability rather than leaning on one US report card.

Friends of the Earth has also gone after LNG, liquefied natural gas, used as fuel on some newer ships, calling it “a greenwashing fuel source” that adds to large ships’ climate footprint rather than actually cutting pollution. Scrubbers are another sore point. CLIA and much of the industry frame them as emissions-reduction kit, while Friends of the Earth argues they just move air pollution into the water via their discharge.

So, what’s cruising’s real impact on the environment?

Based on everything above, yes, cruising is more carbon-intensive per passenger than most land-based holidays, and cruise ships are heavier polluters mile for mile than flying, even the newest and most efficient ones. Whether that makes cruising “bad” in any absolute sense depends what you’re comparing it to, and how much weight you put on waste, sewage and noise alongside the carbon figures.

It’s not a level playing field across the industry, either. Some operators do noticeably better than others on sewage treatment, transparency and shore power, and picking a smaller ship, a CLIA member line, or an itinerary with more nights at sea and fewer in port can measurably shrink your own footprint. If you’re weighing this up alongside other concerns before booking, our guide to cruise ship safety records and statistics covers a question people often ask right alongside the environmental one.

Common Questions

Are cruise ships bad for the environment?
Per passenger, cruising produces more CO2 than most land-based holidays, plus more air, water and noise pollution than most people expect. How much varies a lot between operators and ship types.

Are cruise ships worse than flying?
Per kilometre, yes, for most ships. ICCT research puts even the most efficient large cruise ships at around 250g of CO2 per passenger-kilometre, above typical aircraft figures of roughly 10 to 130g.

What does minimal impact cruising mean?
It means choosing a smaller ship, a more sustainably run line, or an itinerary that cuts pollution per passenger. There’s no official certification behind the phrase.

Do cruise ships dump raw sewage into the sea?
Under MARPOL Annex IV, treated sewage discharge is allowed, and CLIA members commit to never discharging it untreated. Enforcement, particularly in the US, has been criticised as patchy.

What is a scrubber, and why is it controversial?
A scrubber cleans a ship’s exhaust of sulphur using seawater, then discharges that wastewater overboard. Campaigners argue it just moves the pollution from the air into the water rather than getting rid of it.

Which cruise lines score best environmentally?
Friends of the Earth’s report card gave its top grade, B+, to just Hurtigruten and Hurtigruten Expeditions. The ranking is US-focused though, so it doesn’t cover every line UK travellers commonly book.

Will cruise ships reach zero emissions?
CLIA member lines have committed to net zero by the middle of the century, along with a fleet-wide 40% cut in the rate of carbon emissions by the end of this decade.

Does cruise ship noise really harm marine life?
Yes. Research cited by Friends of the Earth and Earth.Org links ship noise to disrupted feeding, raised stress and displaced predators and fish, and whale calls have been recorded growing louder over time to compensate.

Is onshore power supply available at most cruise ports?
No. Fewer than 3% of the world’s cruise ports currently have a berth equipped for it, though CLIA reports dozens more are funded or in planning.

Why Trust About2Cruise

This article draws on published data from bodies including the International Maritime Organisation, the International Council on Clean Transportation, Cruise Lines International Association and independent environmental campaigners such as Friends of the Earth, rather than promotional material from any cruise line. You can read more about how we research and fact-check our guides on our about us page.