Cruise Ships: A Major Source Of Water Pollution

Cruise ships have long been criticised for their negative environmental impact, with concerns raised about their emissions of air pollutants, greenhouse gases, and the dumping of sewage and wastewater. The cruise industry is the fastest-growing in tourism and, despite efforts to improve sustainability, it continues to face scrutiny over its pollution record. So, how much pollution do cruise ships cause?

Cruise ships emit large amounts of sulfur and nitrogen oxides, contributing to air pollution and health risks

Cruise ships emit large amounts of sulfur and nitrogen oxides, which have severe impacts on both the environment and human health. In 2022, Europe's 218 cruise ships emitted as much sulfur oxide (SOx) as one billion cars, with Carnival Corporation's cruise liners emitting nearly ten times more SOx pollution around European coasts than all of Europe's cars. SOx emissions form sulfate aerosols that contribute to serious health risks, including premature death from lung cancer, throat cancer, COPD, cardiovascular diseases, and childhood asthma.

Nitrogen oxide (NOx) emissions from cruise ships also have detrimental effects. In Marseille, France, 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. The high levels of NOx in Marseille have led to residents being diagnosed with respiratory-related cancers at abnormally high rates. Additionally, studies have shown that passengers on cruise ships are exposed to heightened concentrations of nitrogen oxides during their voyage, posing significant health risks.

To address these issues, cruise ships are required to use low-sulfur fuel or abatement technologies while docking in populated areas. However, critics argue that these measures are insufficient to protect the health of locals and passengers. Some ports, such as Vancouver and those in the European Union, have implemented regulations and projects aimed at reducing air pollution from cruise ships. For example, the Port of Vancouver has banned the use of scrubbers, which redirect pollution from the air into the water. The International Council on Clean Transportation (ICCT) is also working on the FUMES project to measure methane emissions from LNG-fueled ships, including cruise ships.

While some cruise lines are taking steps to reduce their environmental impact, such as MSC Cruises' new LNG-powered ship, the industry as a whole has been criticized for its pollution, greenhouse gas emissions, and over-tourism. Environmental groups have expressed doubts about the industry's ability to achieve its goal of "net-zero carbon" cruising by 2050.

Greenhouse gas emissions from cruise ships are high, with LNG engines having a higher life-cycle GHG emission

Cruise ships have gained a reputation for contributing significantly to carbon emissions. The largest and most efficient cruise ships emit around 250 grams of CO2 per passenger per kilometre, which is considerably higher than the carbon intensity of a short-haul flight. On average, a cruise ship emits 250g of CO2 per passenger kilometre travelled. In comparison, an average airline emits 160 kgCO2 per passenger on a 2,000-km journey.

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 operated by Carnival Corporation emitted nearly ten times more SOx air pollution around European coasts than all of Europe's cars. Sulfur oxide (SOx) emissions form sulphate (SO4) aerosols, which are detrimental to human health. SOx emissions, fine particles (PM2.5), and nitrogen oxides (NOx) cause premature death by various means, including lung cancer, throat cancer, chronic obstructive pulmonary disease (COPD), cardiovascular diseases, and morbidity such as childhood asthma.

Cruise ships are also responsible for releasing nitrogen oxides (NOx) into the atmosphere, impacting the environment and human well-being. In Marseille, France, 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. Additionally, 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.

Furthermore, some cruise ships that use liquefied natural gas (LNG) emit methane, a potent greenhouse gas, due to methane slipping from their engines. This "methane slip" occurs during combustion from pressure dual-fuel engines, and the life-cycle greenhouse gas (GHG) emissions from these engines are higher than using low-sulfur marine gas oil. LNG-powered ships are transitioning to reduce direct air pollution emissions, but the "methane slip" leads to higher overall emissions.

The cruise industry is the fastest-growing sector in tourism, and environmental groups have expressed concerns about its ability to achieve sustainability goals. While the industry has promised to make zero-emission vessels and fuels widespread by 2030 and achieve "net-zero carbon" cruising by 2050, critics argue that without legally binding regulations, the cruise industry will continue to pollute and endanger public health.

Cruise ships generate different types of waste, including sewage, wastewater, and solid waste

Cruise ships produce several types of waste, including sewage, wastewater, and solid waste. Sewage includes human waste from toilets, while wastewater (also known as greywater) comes from sinks, showers, and kitchens. Solid waste includes food scraps, unfinished beverages, scrap paper, and plastic.

The sewage and wastewater generated on cruise ships are typically treated and filtered onboard using advanced water treatment facilities before being discharged into the ocean. These facilities employ settlement tanks, filters, chemical treatments, and water quality tests to ensure that the water is free from harmful contaminants and meets regulatory standards. However, it is important to note that some cruise ships lack adequate sewage treatment facilities, leading to the release of untreated sewage into the ocean.

The solid waste produced on cruise ships is segregated and dehydrated. Recyclable materials, such as reusable plastics, glass containers, and metal cans, are cleaned and stored for recycling once the ship reaches land. Larger cruise ships may also have incineration facilities that can treat solid waste at high temperatures, reducing its volume and sterilizing it.

Despite these treatment measures, cruise ship waste can still contribute to ocean pollution. In the United States, cruise ships are permitted to dump treated waste into the ocean if they are more than three and a half miles offshore. This waste includes sewage, dirty wash water, and food waste. The discharge of sewage and wastewater can have significant impacts on water quality and marine ecosystems, leading to oxygen depletion and the growth of algae blooms that harm marine life.

Additionally, cruise ships may release other forms of waste, such as bilge water, which collects in the lowest part of the ship's hull and may contain oil, grease, and other contaminants. The cleaning of smokestacks and the use of scrubbers to treat air emissions can also result in the discharge of acidic wastewater containing heavy metals, polycyclic aromatic hydrocarbons (PAHs), and suspended particulate matter, further contributing to ocean pollution.

Cruise ships can negatively impact fragile habitats, coastal communities, and wildlife

Cruise ships have a detrimental impact on fragile ecosystems, coastal communities, and wildlife. The air pollution produced by these ships can cause serious health issues for those living in nearby port cities and coastal communities. A 2019 study by Transport & Environment found that approximately 50,000 Europeans die prematurely each year due to pollution from the shipping sector. This is especially true for those residing in harbour cities like Southampton, where playgrounds are often located near the docks, exposing children to harmful emissions. Cruise ships emit large amounts of sulfur oxides (SOx), contributing to air pollution and acid rain. In 2022, Europe's 218 cruise ships emitted as much SOx as one billion cars.

In addition to SOx emissions, cruise ships release nitrogen oxides (NOx) into the atmosphere, impacting both the environment and human well-being. NOx emissions have been linked to respiratory issues and cancers. For instance, in Marseille, residents have experienced abnormally high rates of respiratory-related cancers following the growth of the cruise industry. Furthermore, cruise ships account for a significant proportion of black carbon emissions, which can exacerbate climate change, particularly in the Arctic region. These ships also release heavy metals, which are toxic to marine life, and produce wastewater and sewage that can contaminate marine ecosystems.

The impact of cruise ships on fragile habitats is evident in Venice, Italy, where the passage of cruise ships through the Giudecca Canal has damaged the foundations of historical buildings and blocked the view for inhabitants and tourists. In 2012, UNESCO urged Venetian authorities to restrict cruise ship access to Venice and other Italian ports with vulnerable architecture. While some ports have implemented measures to reduce air pollution, such as using shore power or low-sulfur fuel, critics argue that these steps are insufficient to protect the health of local communities.

The cruise industry has recognized the need to reduce its environmental footprint, with promises to introduce zero-emission vessels and fuels by 2030 and achieve net-zero carbon cruising by 2050. However, environmental groups remain sceptical about the industry's ability to meet these goals without legally binding regulations. The impact of cruise ships on fragile habitats, coastal communities, and wildlife is undeniable, and addressing this issue requires a combination of industry initiatives and stronger regulatory measures.

Cruise ships' decks have poor air quality, with levels of pollution worse than the world's most polluted cities

Cruise ships have long been criticised for their contribution to air pollution, and the air quality on their decks has been a particular cause for concern. An undercover investigation by Channel 4 Dispatches found that the air quality on some cruise ship decks is worse than in the world's most polluted cities. The investigation focused on the levels of "ultra-fine particles" in the air, which are emitted from the fuel burned by the ships' engines. These particles can have serious health impacts, including respiratory and cardiovascular issues, and can even cause premature death.

The findings of the Channel 4 Dispatches investigation are supported by additional research and data. A 2019 study by Transport & Environment found that the European port cities of Southampton, Marseille, and Venice were among the most polluted by cruise ships. In Marseille, for example, the NOx emissions from cruise ships were nearly equivalent to those produced by a quarter of the city's passenger cars. Similarly, in Venice, the cruise ships passing through the Giudecca Canal not only polluted the air but also damaged the foundations of historical buildings and blocked the view for inhabitants and tourists.

The poor air quality on cruise ship decks is primarily due to the fuel used by these vessels. Heavy fuel oil, also known as bunker oil or marine fuel, is commonly used by cruise ships due to its low cost. However, this type of fuel is highly polluting and contributes to the emission of sulfur oxides (SOx), nitrogen oxides (NOx), and particulate matter. In recent years, some cruise ships have started using liquefied natural gas (LNG) as a transition fuel, which can reduce direct air pollution emissions. However, LNG engines can suffer from ""methane slip," where unburned methane is leaked into the atmosphere, contributing to greenhouse gas emissions.

To address the issue of poor air quality on cruise ship decks, some regions have implemented regulations and initiatives. For example, California requires cruise ships to use shore power, and the Port of Vancouver has banned the use of scrubbers, which redirect pollution from the air into the water. The International Council on Clean Transportation (ICCT) is also working to measure and reduce methane emissions from LNG-fueled ships. Additionally, some modern ships are using electric engines, LED lamps, and exhaust gas cleaning systems to reduce air pollution.

While there have been efforts to improve air quality on cruise ship decks, the industry still faces challenges in reducing its environmental impact. Environmental groups have criticised the cruise industry for its record on pollution, greenhouse gas emissions, and over-tourism. The industry has promised to make zero-emission vessels and fuels widespread by 2030 and to achieve "net-zero carbon" cruising by 2050. However, critics argue that stronger regulations are needed to hold the industry accountable and ensure the health and safety of passengers and local inhabitants.

Frequently asked questions