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Last updated: 4 April 2024

Can the Large Cruise Ships Drive Systemic Change in Maritime Sustainability?

World largest cruise ship to set sail later in the year

The recent launch of the Icon of the Seas, which holds the title of the world's cruise ship, has drawn attention to the impact associated with cruise tourism. While Royal Caribbean emphasises that the ship operates on liquefied gas (LNG), considered one of the marine fuels available, environmental experts have raised concerns regarding this claim.

Bryan Comer, director of the marine program at the International Council on Clean Transportation, has criticised LNG usage as a "misleading solution" and an example of attempting to appear environmentally friendly without truly addressing climate issues.

The cruise industry faces challenges due to its high carbon emissions footprint, sulfur oxide releases and other pollutants that harm air quality and contribute to acid rain.

Despite technological advancements and some monitoring efforts, cruising continues to be a source of pollution that affects ecosystems and poses risks to public health. Furthermore, colossal ships like the Icon of the Seas consume energy due to their size and extravagant amenities, resulting in greenhouse gas emissions.

To put things into perspective, a cruise ship's carbon footprint surpasses 12,000 cars. The Icon of the Seas is particularly noteworthy because it presents challenges in being classified as the vessel in its category.

Although it already exceeds shipping regulations by being 24% more efficient in carbon emissions, environmental organisations have raised concerns about the cruise ship's methane emissions.

Now, let's explore how cruise ships can help kickstart a sustainability movement within the industry.

What Do We Mean With Cruise Ships Exactly?

Cruise ships are large vessels designed to carry passengers in comfort and luxury across the seas and oceans. They are floating resorts with many amenities, such as restaurants, swimming pools, theatres, and other entertainment options. 

Globally, the cruise industry is a significant economic driver, generating over £114 billion in economic activity annually and supporting 1.17 million jobs with more than £38 billion in salaries and wages. 

The industry's revenues primarily come from cruise ship passengers, and the ability to attract and maintain clientele is crucial for its growth. 

The Environmental Impact of Cruise Ships

Cruise ships are often likened to floating cities because of their size and capacity. For example, the Icon of the Seas can accommodate over 9,000 passengers and crew members. This ship alone would release around 15 million tonnes of CO2 annually, equivalent to 2.2 million cars.

Furthermore, on average, cruise ships and other maritime vessels, such as cargo ships, tankers, oil tankers, and ferries, account for about 3% of greenhouse gas emissions yearly. On average, a cruise ship emits 250g of CO2 per passenger kilometre travelled—much more carbon intensity than a short-haul flight.

One area of concern for cruise ships like the Icon of the Seas is methane emissions or what is known as "methane slip ", referring to leakage during combustion from pressure dual-fuel engines.

They have been criticised for their harmful effects on the ocean, including the dumping of sewage and wastewater, emissions of air pollutants and greenhouse gases, and the use of heavy fuel oil. To put this into perspective, a medium-sized cruise ship can emit as much particulate matter as one million cars. 

The most common pollutants that cruise ships emit

Here are the most common pollutants, shedding light on their environmental challenges.

  1. Sulfur Oxide Emissions: Cruise ships emit large amounts of sulfur oxides (SOx), contributing to air pollution and acid rain. For instance, in 2022, Europe's 218 cruise ships emitted as much SOx as 1 billion cars. Cruise liners run by Carnival Corporation emitted nearly 10 times more SOx air pollution around European coasts than all of Europe's cars.
  2. Nitrogen Oxide Emissions: Cruise ships also release nitrogen oxides (NOx) into the atmosphere, affecting the environment and human well-being. Cruise ships accounted for 15% of the nitrogen oxide particles emitted by Europe's passenger vehicles. In Marseille, where 57 cruise ships docked in 2017, their NOx emissions were nearly equivalent to those produced by a quarter of the city's 340,000 passenger cars.
  3. Carbon Emissions: Cruise ships have gained a reputation for contributing to carbon emissions. The largest and most efficient cruise ships emit around 250 grams of CO2 per passenger per kilometre, considerably higher than the carbon intensity of air travel, which ranges from 10 to 130 grams of CO2 per passenger per kilometre. Surprisingly, an individual on a cruise ship emits as much CO2 as someone who travels by plane and stays in a hotel. One person aboard a cruise ship emits 421.43 kilograms of CO2 daily.
  4. Black Carbon (BC): Cruise ships account for a disproportionate amount of black carbon emissions, a component of soot that can exacerbate climate change, particularly in the Arctic region. This accounts for 6% of black carbon emissions despite making up only 1% of the global fleet. 
  5. Heavy Metals: These vessels can release heavy metals into the environment, which are toxic to marine life
  6. Methane (CH4): Some cruise ships that use liquefied natural gas (LNG) emit methane, a potent greenhouse gas, due to methane slipping from their engines
  7. Waste Streams: Cruise ships generate different types of waste, such as wastewater from sinks, showers, and kitchens (grey water), as well as solid waste.
  8. Impact on Fragile Habitats and Wildlife: Cruise ship pollution can impact ecosystems, coastal communities, and wildlife. It releases waste into our oceans, contributes to increased atmospheric carbon dioxide levels, and can pose risks to animals.
  9. Air Pollution in Port Cities: Increased air pollutants from cruise ships have negatively impacted the air quality in Europe's port cities, surpassing the pollution levels observed before the pandemic.

As the cruise industry continues to grow with an increase in vessel size by 10,000 tonnes, these environmental issues will inevitably become more significant for average-sized liners.

What Is So Bad About Cruise Ships For The Environment?

Cruise ships impact the environment in several ways, from the air pollution they emit to the waste they generate. A critical issue is dumping sewage and wastewater into the ocean, which can harm marine life and ecosystems. 

These floating cities of leisure and luxury have long been celebrated for their ability to offer a unique travel experience. However, beneath the surface of these grand voyages lies a less talked-about truth: their significant environmental impact.

Cruise ships comparative analysis to an average care
Image credit: Transport & Environment

According to a study, one on a typical cruise ship emits roughly 421.43kg of CO2 daily, eight times more than one individual staying on land. In absolute terms, countries like Spain, Italy, Greece, France, and Norway are the most exposed to SOX air pollution from cruise ships due to their status as major tourist destinations and less stringent marine sulphur fuel standards. 

What is the Impact of Cruise Ships?

The environmental impact of cruise ships is significant when viewed from different angles.

Total Impact per Year

Cruise ships are known to be heavy carbon emitters. A medium-sized cruise ship emits greenhouse gases equivalent to those of 12,000 cars, and it could dump over 1 billion gallons of untreated sewage into the ocean.

For instance, during the six-month cruise season, a ship sailing from Seattle to Alaska emitted 1.1 million tons of CO2 to 559,414 passengers. This data indicates that the cruise industry can generate more than a million tonnes of garbage annually. 

Impact per Day

A daily cruise trip averages 700-1000 pounds of carbon emissions, much higher than flying, driving, or a traditional 'land' vacation. Additionally, the sulphur dioxide emissions from a single cruise ship can equal the emissions from 13.1 million cars per day, exacerbating air pollution and acid rain.

Data shows that large cruise ships can burn up to 250 tons of fuel daily, producing substantial CO2 emissions. Primarily, bunker fuel, the dirtiest fuel, exacerbates the environmental damage, emitting considerable amounts of black carbon, sulfates, and other harmful chemicals​. 

Impact per Usage

When considering the impact per usage, vacationers generate eight times more carbon on a cruise ship than on land. A week-long journey on a cruise ship for one passenger can result in over 200 kilograms of CO2 emissions, significantly higher than many other forms of travel.

For instance, a five-night, 1,200-mile cruise produces about 1,100 lbs of CO2 emissions. The average CO2 emissions for a 3,000-passenger cruise ship is 1,200 kg/km, and trips can be thousands of kilometres long. 

The water and energy consumption rates are equally alarming, with a cruise ship passenger's daily water usage being more than twice that of an average person on land.

This highlights cruise vacations' disproportionate environmental impact compared to more sustainable travel options.

Top Largest Cruise Ships and their CO2

The cruise industry has seen substantial growth in ship sizes, with the most significant ships now exceeding 200,000 gross tons (GT). 

The largest cruise ship in the world, as of 2024, is the Icon of the Seas, operated by Royal Caribbean International. The carbon footprint of such a large cruise ship is significant.

A person who takes a five-day cruise on a cruise ship, even the most efficient one, will be responsible for generating about 500 kg of CO2. This is about twice the total greenhouse gas emissions of an aeroplane flight. 

The carbon emissions of these ships are a critical environmental concern, with the largest and most efficient cruise ships emitting about 250 gCO2 per passenger kilometre.

Largest Cruise Ships by Size and Emissions (2024 and Beyond)

RankShip NameCruise LineYear LaunchedGross Tonnage (GT)Maximum Passenger CapacityCarbon Emissions (gCO2/pax-km)
1Icon of the SeasRoyal Caribbean2024248,3367,600250
2Wonder of the SeasRoyal Caribbean2022236,8576,988250
3Symphony of the SeasRoyal Caribbean2018228,0816,680250
4Harmony of the SeasRoyal Caribbean2016226,9636,687250
5Oasis of the SeasRoyal Caribbean2009225,2826,780250

Mid-Size Cruise Ships (5-10 Years Ago)

RankShip NameCruise LineYear LaunchedGross Tonnage (GT)Maximum Passenger CapacityCarbon Emissions (gCO2/pax-km)
6Quantum of the SeasRoyal Caribbean2014168,6664,905250
7Anthem of the SeasRoyal Caribbean2015168,6664,905250
8Norwegian EscapeNorwegian Cruise Line2015164,9984,266250
9Carnival VistaCarnival Cruise Line2016133,5003,934250
10MSC MeravigliaMSC Cruises2017171,5984,500250
Data source: Statista, Wikipedia and other reputable sources


  • The gross tonnage (GT) reflects the ship's overall internal volume, with larger numbers indicating bigger ships.
  • The maximum passenger capacity is based on double occupancy per cabin, a standard measure in the cruise industry.
  • Carbon emissions are estimated based on the most efficient cruise ship data. It's important to note that actual emissions can vary based on the ship's operational efficiency, actual usage, fuel type, and occupancy implemented by the cruise line.

Can Cruise Ships Become Toxic?

Yes, cruise ships can become toxic to the environment in various ways. In Europe, for example, the 218 cruise ships operating last year emitted more than four times more sulfur oxides than all of the continent's cars combined. These emissions are particularly harmful around ports, where they exceed pre-pandemic levels.

Moreover, air pollutants from cruise ships can lead to serious public health problems. For instance, nitrogen oxide (NOx) emissions from cruise ships in Europe impact some cities, equivalent to about 15% of the NOx emitted by Europe’s passenger car fleet.

Regarding water pollution, cruise ships generate billions of gallons of waste pumped into our oceans. This waste includes sewage, solid waste, oily bilge water, and scrubber wastewater, all of which contain toxins harmful to marine ecosystems.

While some cruise operators are investing in liquefied natural gas (LNG) as a cleaner alternative, LNG-powered ships can produce methane (CH4) emissions, a potent greenhouse gas.

The Top Most Polluted Cruise Ports

While offering an escape to the sea's tranquillity and diverse cultural experiences at each port, cruise ships cast a long shadow on the environment. Their impact on the world's most visited cruise ports is a growing concern, especially regarding air and water pollution.

According to Statista, Barcelona was Europe's most sulfur-polluted cruise port in 2022, with cruise ships emitting 18,277 kilograms of sulfur dioxide (SOx). The Mediterranean region bears the brunt of cruise ship pollution, with Italy surpassing Spain as Europe's most cruise ship-polluted country. 

Venice significantly improved after banning large cruise ships, resulting in an 80% fall in SOx emissions. 

Cruise ships also contribute to black carbon (BC) emissions, with the industry accounting for 6 per cent of BC emissions despite making up only 1 per cent of the global fleet.

This indicates the disproportionate environmental impact of cruise ships compared to other vessels.

RankPort CityCountryNotable PollutantsSulphur Oxide Emissions (Tonnes per Year)Measures Taken
1BarcelonaSpainSOx, NOx, PM2.532,800-
2CivitavecchiaItalySOx, NOx, PM2.528,500-
3Palma MallorcaSpainSOx, NOx, PM2.528,000-
4VeniceItalySOx27,500Ban on large cruise ships, 80% reduction
5PiraeusGreeceSOx, NOx, PM2.526,000-
6SouthamptonUnited KingdomSOx, NOx, PM2.527,100Electrification at ports
7LisbonPortugalSOx, NOx, PM2.520,000-
8HamburgGermanySOx, NOx, PM2.520,000-
Data was sourced from Statista, Transport & Environment (T&E), and other environmental studies.

Are Cruise Ships Sustainable?

The sustainability of cruise ships is debated among environmentalists, industry stakeholders, and tourists due to their multifaceted impact on the planet and communities. The maritime industry has been scrutinised for its substantial carbon footprint, waste generation, and impact on marine ecosystems.

Sulphur dioxide, a key component of acid rain, causes respiratory and cardiovascular problems. Port cities are increasingly considering banning or restricting cruise ships due to pollution concerns. Friends of the Earth claims cruise ships harm the air, water, fragile habitats, coastal communities, and wildlife. 

For cruise ships to align with broader sustainability goals, concerted efforts from the industry, governments, and travellers will be required.

Environmental Impact Compared to Everyday Things

Though often criticised for their substantial environmental impact, how do they compare to everyday activities and choices?

A medium-sized cruise ship can emit greenhouse gases equivalent to 12,000 cars. Furthermore, the industry's growth has led to larger ships, exacerbating the problem.

To put this into perspective, let's compare the environmental impact of cruise ships to everyday activities. A five-night, 1,200-mile cruise results in about 1,100 lbs of CO2 emissions. In contrast, flying the same distance and staying in a hotel would emit a carbon footprint of 264kg of CO2 per person. 

Even a medium-sized cruise ship can have worse emissions than thousands of cars. To put this into perspective, the average person driving to work emits a fraction of this amount in a year.

An average cruise ship produces about 25,000 gallons of sewage and 143,000 gallons of greywater from sinks, showers, and galleys daily. Comparatively, an average household in the UK produces about 350 gallons of sewage a month, highlighting the vast disparity in waste generation.

Cruise ships also contribute to water pollution through the discharge of ballast water, which can introduce invasive species to new environments, significantly impacting local ecosystems. This issue is not commonly encountered in everyday activities but parallels agricultural runoff in terms of its potential to harm aquatic life.

What Are Alternatives to Cruise Ships?

While cruising offers a unique and convenient way to vacation. Fortunately, numerous alternatives provide similar benefits with fewer ecological drawbacks.

  • All-Inclusive Resorts: These provide a fixed price for accommodation, meals, and activities, often in beachfront locations with various amenities.
  • National Parks: For nature enthusiasts, national parks offer scenic beauty, wildlife, and outdoor activities.
  • Escorted Tours: Guided tours can offer a structured travel experience with the benefit of expert knowledge and pre-arranged itineraries.
  • Multi-City/Country Trips: Planning a trip that includes multiple destinations allows for a tailored experience and the opportunity to explore diverse cultures and landscapes.
  • Staycations: Enjoying local attractions and relaxation without needing long-distance travel can be a refreshing alternative.
  • Land Cruises: These bus tours mimic the cruise experience on land, with stops at various attractions.
  • Freighter Ship Travel: Booking accommodations on a cargo ship can provide a unique and less environmentally impactful way to travel by sea.
  • Sailboat Cruises: Sailing offers a more eco-friendly way to enjoy the water with a smaller carbon footprint.
  • River Cruises: Smaller and often more environmentally friendly, river cruises provide a more intimate setting and access to inland destinations.
  • Catamaran Trips: Offering more space and stability, catamaran trips can be a relaxing way to enjoy the water.

To illustrate the environmental impact of cruise ships compared to alternatives, enjoy unforgettable experiences while protecting the planet.

Vacation TypeCO2 Emissions (per passenger)Notable Environmental Impact
Cruise ShipEquivalent to 12,000 carsHigh emissions, waste issues
All-Inclusive ResortLower than cruise shipsDepends on resort practices
National Park VisitMinimalLow impact, promotes conservation
Sailboat CruiseMuch lower than cruise shipsEco-friendly, low-emissions
Freighter Ship TravelLower than cruise shipsUtilizes existing transport

Is It Better Than Alternatives?

From an environmental perspective, almost all alternatives to traditional cruising offer benefits. They typically result in lower carbon footprints, less pollution, and reduced harm to marine ecosystems.

Moreover, these alternatives can provide more authentic and immersive experiences, allowing travellers to engage more deeply with the destinations they visit.

Statistics, Facts, and Figures About Cruise Ships

As of 2023, global ocean cruise passengers reached 31.5 million.

The cruise industry generates over £114 billion in economic activity annually, supports 1.17 million jobs, and contributes more than £38 billion in salaries and wages.

The unsustainable practices of massive vessels include dumping sewage and wastewater, air pollutants, and greenhouse gas emissions.

The average cruise duration is seven days, with seven-day cruises accounting for 40% of all cruises. 

The average age of cruise passengers is 47, and many cruisers are aware of the environmental impact of their travels.

Cruise ships comprise about 1% of the global fleet but are responsible for over 6% of black carbon emissions.

Onboard spending, such as drinks, spa treatments, and speciality restaurants, can account for over a third of a cruise line's revenue.

Carnival Corporation & plc, a major player in the industry, reported a revenue of approximately £9.3 billion in 2023.

Large Cruise Ships as a Catalyst for Systemic Change

The cruise industry has developed, with ships becoming more opulent. The "Icon of the Seas ", the title of the world's cruise ship, exemplifies this trend.

According to the Shipping Initiative (SSI), bringing about change in the maritime sector necessitates a broader perspective beyond simply reducing greenhouse gas emissions. It involves fostering an equitable and sustainable system that considers workers' rights, safety measures, and responsible ocean governance.

Technology and Innovation

The construction and operation of such an intricate vessel can spur technological innovation. This includes advancements in making the ship more fuel efficient, improving waste management systems and incorporating design features.

It is crucial to adopt several key technologies and practices to transform this vessel from an environmental concern into a driver of positive change.

  1. Alternative Fuel System: Shifting away from fuels to lower carbon alternatives like liquefied natural gas (LNG) can significantly reduce emissions. Additionally, integrating hydrogen fuel cells holds promise for extending the ship's range capabilities and enabling refuelling.
  2. Embracing Energy Efficiency: Implementing energy-saving features such as LED lighting, advanced air conditioning systems, and efficient hull designs can decrease the ship's energy consumption. Heat recovery systems can also convert waste heat into energy, enhancing efficiency.
  3. Implementing Advanced Wastewater Treatment: To minimise water pollution, state-of-the-art onboard wastewater treatment plants can process sewage and greywater to levels that meet international standards for safe discharge.
  4. Reducing Waste Generation and Managing Waste: Onboard recycling programs, composting systems for food waste, and initiatives to minimise the use of single-use plastics can substantially decrease the amount of waste generated during voyages.
  5. Renewable Energy Integration: By incorporating solar panels and wind power systems, we can enhance the ship's energy requirements while decreasing fuel dependence. Additionally, it would be worthwhile to investigate the possibilities of utilising wave energy as a power source.

Regulatory Catalyst

The arrival of this vessel comes at a time when international organisations, like the International Maritime Organization (IMO) and other regulatory bodies, are becoming stricter with standards. This ship can potentially drive the implementation of environmental regulations, such as the IMO 2020 rule that restricts the amount of sulfur in ship fuel.

  1. Emission Control Areas (ECAs): By following ECA standards, this ship can set an example and encourage broader adoption of these strict emission regulations. For instance, in 2024, changes to the EU Emissions Trading System (EU ETS) will place responsibilities on the sector, including implementing carbon pricing for maritime transportation activities. 
  2. Tracking Carbon Footprint: The cruise line could establish a system to monitor and report its carbon footprint, promoting accountability throughout the industry.
  3. Collaboration with Ports: Ports can play a role in facilitating the shipping industry's transition towards zero carbon emissions. Collaboration across sectors will be essential as ports can support infrastructure for fuels and help manage risks involved in various projects.

Consumer Awareness and Demand

As more people become conscious of the environment, passengers increasingly become interested in sustainable travel options. The cruise industry can tap into this trend by showcasing the world's cruise ships' eco features and operational practices.

  1. Spreading Awareness: Cruise companies can engage passengers by providing information about sustainability initiatives and efforts to protect the environment. Create a demand for greener cruises.
  2. Certifications and Ratings: Obtaining third-party certifications for performance allows consumers to make informed choices and encourages competition within the industry to prioritise sustainability.
  3. Promoting Behaviour: Offering discounts or additional benefits to passengers who actively participate in eco practices while on board can incentivise them to adopt more environmentally responsible actions.

The Future of Cruise Ships

The largest cruise ship in the world is on the verge of marking a milestone in history. This ship has the potential to initiate changes within the industry, driving it towards a sustainable future.

It demonstrates that size and luxury can coexist with responsibility. The ship indicates that incorporating sustainability into design and operation is indeed feasible.

It is crucial for all industry stakeholders, including shipbuilders, policymakers, and consumers, to engage in discussions about cruise ship sustainability. These conversations should prioritise improvement, innovation, and the adoption of practices to protect our oceans for future generations.

Although the journey towards achieving sustainability may be prolonged, with the world's largest cruise ship leading the way, it is an endeavour worth pursuing.

Henceforth, balancing these innovations and considering the environment and workforce needs that drive this industry forward is vital.

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