Cruise Ships Vs Planes: Who's The Bigger Polluter?

The cruise industry is often criticised for its negative environmental impact, with cruise ships being compared to planes in terms of carbon emissions and pollution. While flying is by no means environmentally friendly, cruise ships emit more carbon dioxide per passenger kilometre and generate large amounts of waste, including sewage and oil-contaminated water, which is often pumped into the ocean. Cruise ships also emit sulphur oxides and nitrogen oxide, which are carcinogenic. However, some cruise companies are making efforts to become more sustainable, with advancements in technology and fuel choices.

Cruise ships emit more carbon dioxide per passenger kilometre than planes

This means that if a person goes on a 5-night cruise that covers 2,000 km, they are responsible for 500 kgCO2. The same person flying by jet would emit 160 kgCO2, and even adding in the emissions from a hotel stay, the total is still only 235 kgCO2. This shows that, in this example, a passenger on a cruise ship emits about two times more CO2 than someone who flies and stays in a hotel.

Cruise ships also emit large amounts of sulphur oxides and nitrogen oxide, which are carcinogenic substances. In addition, waste produced on cruise ships is often not properly disposed of, with several cruise liners having been charged with discharging oily waste, grey water, and plastic into the oceans.

While planes also produce pollution and waste, the relative difference in carbon footprint may not outweigh the benefits of taking a cruise for some individuals. However, it is important to note that the cruise industry is starting to make improvements, with some ships switching to cleaner-burning liquefied natural gas and companies like Hurtigruten planning to launch emissions-free cruise ships.

Cruise ships produce more waste than planes

Cruise ships and planes are both highly polluting modes of transport that contribute massively to global warming. However, cruise ships produce more waste than planes.

On a typical one-week voyage, a cruise ship generates over 50 tonnes of garbage, a million tonnes of grey (waste) water, 210,000 gallons of sewage, and 35,000 gallons of oil-contaminated water. Some of this waste is pumped into the ocean, and some is treated. In comparison, all the waste produced during a flight is brought back down to ground level and disposed of properly. While flights do produce a large volume of food and plastic waste, this waste is not disposed of by throwing it out of plane windows. Airlines generate 6.7 million tonnes of cabin waste annually, with 20-30% consisting of untouched food and drinks.

Cruise ships are known for choosing the cheapest fuel on the market and opting to use scrubbers instead of safer, more expensive alternatives. Scrubbers, also known as the "emission cheat" method, work by cleaning the cheap fuel and disposing of the pollutants directly into the ocean. The scrubber discharge water is contaminated with polycyclic aromatic hydrocarbons and heavy metals, which have been linked to cancers and reproductive dysfunction in marine mammals. Cruise ships emit large amounts of sulfur oxides and nitrogen oxide, which are both carcinogenic substances. Carnival Corporation, the largest cruise operator, emitted ten times more sulfur oxide than all the cars in Europe combined in 2017.

The carbon footprint of cruise ships is also higher than that of planes. The most efficient cruise ship lines emit about 250 gCO2/pax-km, while the industry average carbon intensity for planes ranges from approximately 10 gCO2/pax-km to 130 gCO2/pax-km, with longer flights tending to have lower carbon intensity. For example, a standard seven-day return cruise traversing 3,500 km has a carbon footprint of 875 kg of CO2 per passenger. In comparison, a direct return flight from London to A Coruña, with a distance of approximately 1,096 km, has a carbon footprint of 110 gCO2/pax-km.

While the cruise industry is making efforts to become more sustainable, such as switching to cleaner-burning liquefied natural gas, it is clear that cruise ships produce more waste and have a higher carbon footprint than planes.

Cruise ships emit more sulphur oxides than planes

Cruise ships are known to emit more sulphur oxides than planes. In 2017, Carnival Corporation, the largest cruise operator, emitted ten times more sulphur oxide than all the cars in Europe combined. According to a June 2023 report by the Brussels-based NGO Transport & Environment (T&E), cruise ships in Europe emitted more sulphur than one billion cars, which is 4.4 times more than the number of cars on the continent. The sulphur oxide emissions from cruise ships at Europe's busiest ports reached 509 tonnes in 2022, a 9% increase from 2019 levels.

The high sulphur oxide emissions from cruise ships are attributed to the use of scrubbers, which are employed to clean cheap fuel and dispose of pollutants directly into the ocean. This practice allows cruise ship operators to choose cheaper, high-sulphur heavy fuel oil instead of more expensive low-sulphur fuels. The scrubber discharge water is contaminated with polycyclic aromatic hydrocarbons and heavy metals, which have been linked to cancers and reproductive dysfunction in marine mammals.

The International Maritime Organization (IMO) has implemented regulations to reduce the maximum sulphur content in fuels for ships, such as the 2020 Global Sulphur Cap, which lowered the limit from 3.5% to 0.5%. However, these regulations have been outweighed by the increasing number of cruise ships in European waters.

While planes also contribute to sulphur oxide emissions, the impact is relatively lower compared to cruise ships. The focus on sulphur oxide emissions from cruise ships is part of a broader concern about the environmental impact of cruising, including carbon emissions, waste disposal, and fuel spills.

To address the issue of high sulphur oxide emissions from cruise ships, there have been calls for the industry to abandon the use of scrubbers, increase the use of marine gas oil, and explore alternative fuels with low or zero life-cycle emissions. Additionally, investing in zero-emission technologies, such as shore power, batteries, fuel cells, and wind-assisted propulsion, can help reduce sulphur oxide emissions from cruise ships.

Cruise ships have a negative impact on the visual aesthetics of a location

Cruise ships have a significant environmental impact, and their carbon emissions contribute to climate change. They emit more carbon dioxide per passenger kilometre than planes, with the most efficient cruise ships emitting about 250 gCO2/pax-km, compared to an average airline flight, which emits approximately 160 kgCO2 per passenger for a 2000 km journey.

Cruise ships also have a negative impact on the visual aesthetics of a location. The exterior appearance of a ship is important in attracting passengers and building its brand image. Cruise ships, with their iconic and visually appealing exteriors, can be a stark contrast to the natural beauty of a location, especially when they dock in ports or coastal areas. Their sheer size can be overwhelming and may detract from the natural scenery, affecting the overall visual appeal of the area.

The design of a cruise ship plays a crucial role in passenger satisfaction, with spacious cabins, amenities, and innovative entertainment options contributing to the overall experience. However, the integration of advanced technologies and innovative designs can sometimes come at the cost of aesthetic appeal. While modern cruise ships aim to incorporate energy-efficient systems and waste reduction strategies, the implementation of such features may not always result in visually appealing designs.

Additionally, the presence of cruise ships in a location can impact the local environment and, consequently, the visual aesthetics. Cruise ships have been known to dump toxic waste into the water, affecting the marine ecosystem and potentially harming fragile habitats and wildlife. This can result in a decline in the natural beauty of the area, including the clarity of the water and the health of marine life, which are all important aspects of the visual aesthetics of coastal locations.

Furthermore, the construction of cruise ship ports and infrastructure can also alter the natural landscape. For example, Disney is currently working on a massive cruise ship port in the Bahamas at Lighthouse Point, which is opposed by community groups due to its potential harm to coral reefs and the migratory patterns of marine wildlife. The development of such infrastructure can permanently change the natural layout of a location, impacting its visual appeal and the overall experience of visitors seeking unspoiled natural environments.

Cruise ships use cheaper, more polluting fuels

Cruise ships are often criticised for using cheaper, highly polluting fuels. Cruise ship operators are known for choosing the cheapest fuel on the market, which tends to be diesel fuel or gas that emits lots of carbon and other pollutants, such as nitrogen oxides, sulphur oxides, and particulate matter.

The use of scrubbers, or the "emission cheat" method, is also common on cruise ships. Scrubbers clean the cheap fuel and dispose of the pollutants directly into the ocean. This allows cruise ships to continue using cheaper high-sulphur heavy fuel oil instead of more expensive low-sulphur fuels. In 2017, Carnival Corporation, the largest cruise operator, emitted ten times more sulphur oxide than all of the cars in Europe combined. More recently, in 2022, cruise ships at Europe's busiest ports emitted 509 tonnes of sulphur oxides, an increase of 9% compared to 2019 levels.

The International Maritime Organization (IMO) has implemented policies to reduce the maximum content of sulphur in fuels, such as the 2020 Global Sulphur Cap, which lowered the limit from 3.5% to 0.5%. However, the increase in the number of cruise ships in European waters has outweighed the potential emissions reductions from such policies.

Some cruise ships are transitioning to liquefied natural gas (LNG), which can reduce carbon emissions by up to 20%. However, the engines that burn LNG can suffer from "methane slip", where unburnt methane is leaked into the atmosphere, leading to higher greenhouse gas emissions than some alternative fuels.

The cruise industry is facing increasing pressure to reduce its environmental impact. Starting in 2024, the European Union will charge ships for their carbon pollution through its Emissions Trading Scheme. To stay competitive and environmentally responsible, the industry must abandon the use of scrubbers, adopt low or zero-emission fuels and technologies, and invest in decarbonisation initiatives.

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