Cruise ships produce significant environmental harm through fuel consumption, waste, and emissions

Cruise ships burn heavy fuel oil—a thick, carbon-intensive fuel left over from refining petroleum—and release the exhaust directly into the air. A single large cruise ship can emit as much sulfur dioxide in a day as a million cars do in a year. The ships also generate sewage, food waste, and wastewater that enters the ocean, and they consume enormous amounts of fresh water and energy to operate.

The environmental cost comes from three main sources: the fuel itself, what comes out of the smokestacks, and what goes overboard. Unlike land-based industries, cruise ships operate in international waters where emissions rules are weaker than they are on shore. The industry has grown steadily, and so has the total damage per year.

Key Takeaways

  • Cruise ships burn heavy fuel oil that produces sulfur dioxide, nitrogen oxides, and particulate matter—pollutants that damage air quality and contribute to respiratory illness in coastal communities.
  • A typical cruise ship generates 1 million gallons of wastewater per week, including sewage and greywater, much of which is discharged into the ocean.
  • Cruise ships produce roughly 50,000 tons of carbon dioxide per ship per year, making them one of the highest-emission forms of travel per passenger.
  • Ships also strike whales, disturb marine ecosystems through noise pollution, and introduce invasive species through ballast water discharge.
  • Some cruise lines have begun switching to liquefied natural gas fuel and installing scrubbers to reduce emissions, but these changes remain voluntary and incomplete across the industry.

Fuel and air pollution from cruise ship engines

Cruise ships operate on heavy fuel oil (HFO), a residual fuel that contains high levels of sulfur and other contaminants. When burned, it releases sulfur dioxide, nitrogen oxides, and fine particulate matter into the atmosphere. These pollutants don't stay over the ocean—wind carries them to shore, where they contribute to smog, acid rain, and respiratory disease in port cities and nearby communities.

A large cruise ship can carry 3,000 to 6,000 passengers and crew. The main engines that move the ship produce roughly 80 megawatts of power continuously. For comparison, a typical coal power plant produces around 500 megawatts but is subject to strict emissions controls that cruise ships are not. The ship's auxiliary engines also run constantly to power hotels, kitchens, air conditioning, and desalination plants, adding to the total emissions.

Some cruise lines have installed scrubbers—devices that spray seawater into the exhaust to remove sulfur dioxide before it leaves the stack. However, scrubbers transfer the pollution from air to ocean by dumping the acidic residue overboard. Other lines have switched to liquefied natural gas (LNG), which produces fewer emissions than heavy fuel oil but still releases carbon dioxide and methane. These technologies are expensive, so adoption remains limited.

Wastewater and solid waste discharged into the ocean

A cruise ship with 3,000 passengers generates roughly 1 million gallons of wastewater per week. This includes sewage from toilets, greywater from sinks and showers, bilge water (oily water from engine rooms), and food waste. In U.S. waters and European Union waters, ships must meet discharge standards and often send waste to port facilities. In international waters, the rules are much looser, and ships can legally dump treated sewage and greywater overboard.

Food waste is ground up and discharged at sea if the ship is far enough from shore. Solid waste—plastic, glass, metal, and paper—is compacted and either stored until port or, in some cases, thrown overboard illegally. Cruise lines have been caught dumping trash and oily waste, and fines have reached millions of dollars, but enforcement remains inconsistent because ships operate across many jurisdictions.

The wastewater introduces excess nutrients (nitrogen and phosphorus) into the ocean, which can trigger algal blooms that deplete oxygen and kill fish. Plastic waste breaks down into microplastics that enter the food chain. Sewage introduces pathogens and pharmaceutical residues that affect marine life and can contaminate drinking water supplies in small island nations that depend on cruise tourism.

Carbon emissions and climate impact

A cruise ship emits roughly 50,000 tons of carbon dioxide per year, depending on size and fuel type. When spread across all passengers and crew, that works out to about 5 to 14 tons of CO2 per person for a week-long cruise. By comparison, a round-trip transatlantic flight produces about 1.6 tons of CO2 per passenger, and driving a car for a year produces about 4 to 5 tons per person.

The cruise industry carried roughly 30 million passengers in 2019 (before the pandemic). If each passenger generates 5 to 14 tons of CO2, the industry's annual carbon footprint is enormous—comparable to the emissions of a small country. The industry has committed to reducing emissions by 50 percent by 2050, but that target is voluntary and does not account for growth in the number of ships and passengers.

Carbon dioxide stays in the atmosphere for centuries, so emissions from cruise ships today will continue warming the planet for generations. The industry's growth in recent decades has outpaced any efficiency improvements, meaning total emissions have risen even as individual ships have become slightly more efficient.

Damage to marine ecosystems and wildlife

Cruise ships strike and kill whales, sea turtles, and other marine mammals. Large ships cannot stop or steer quickly, so collisions often happen in shipping lanes that overlap with migration routes. Noise from ship engines also disrupts whale communication and feeding, forcing them to move away from traditional habitats.

Ships carry ballast water—seawater taken on board to stabilize the vessel—and discharge it in different ports. This practice introduces invasive species to new ecosystems. A species that is harmless in its native ocean can become a pest when released in a new region, outcompeting native species and disrupting food chains.

Cruise ships also anchor in sensitive areas like coral reefs and seagrass beds, damaging them through direct contact and stirring up sediment that smothers marine plants. The sheer number of ships in popular destinations—some ports receive 10 or more cruise ships per day—concentrates this damage in small areas.

Comparison to other forms of travel

A cruise is often marketed as an economical vacation, but the environmental cost per passenger is high. A week-long cruise produces more emissions per person than a round-trip flight to Europe. However, a cruise does include accommodation, meals, and entertainment, whereas a flight is just transportation. The fair comparison depends on what alternative you would choose.

If the choice is between a cruise and a land-based vacation (hotel, rental car, restaurants), the cruise often produces fewer emissions because the ship's fuel consumption is spread across thousands of people. If the choice is between a cruise and staying home, the cruise is worse. If the choice is between a cruise and flying to a resort, the emissions are similar or slightly worse for the cruise.

Trains and buses produce far fewer emissions per passenger than either cruise ships or planes. A week-long train journey across Europe produces roughly 1 to 2 tons of CO2 per person—a fraction of a cruise's impact.

What the cruise industry is doing to reduce environmental impact

Some cruise lines have invested in newer ships with more efficient engines, waste treatment systems, and renewable energy sources like solar panels and wind information technology. A few lines have ordered LNG-powered ships, which produce fewer emissions than heavy fuel oil. However, these ships are expensive to build and operate, so only the largest cruise lines can afford them.

The International Maritime Organization (IMO) has set rules requiring ships to reduce carbon intensity by 30 percent by 2030 and 50 percent by 2050. These targets explore to all ships, not just cruise ships, and they measure efficiency per ton of cargo or per passenger, not total emissions. A cruise line can meet the target by carrying more passengers on the same ship, without reducing total emissions.

Port cities have begun requiring ships to use shore power (electricity from the dock) instead of running engines while docked, which reduces local air pollution. Some ports have also banned the dirtiest fuels or required ships to use scrubbers. However, these rules explore only in specific ports, so ships can straightforward avoid them by changing their itinerary.

Frequently Asked Questions

Is it better to take a cruise or fly to a vacation destination?

A week-long cruise typically produces more carbon emissions per person than a round-trip flight, but the comparison depends on what you're comparing it to. If you would otherwise drive to a resort or take multiple flights, a cruise might produce fewer total emissions. If you would stay home, a cruise is worse for the environment.

Do cruise lines have to follow environmental rules?

Cruise ships operating in U.S. and European waters must follow stricter rules than those in international waters. The International Maritime Organization sets global standards, but enforcement is weak because ships operate across many countries. Some cruise lines have been fined millions of dollars for illegal dumping, but violations continue.

Can I take a cruise that's better for the environment?

Newer ships with LNG engines and advanced waste treatment systems produce fewer emissions and less pollution than older ships. Some cruise lines publish environmental reports showing their emissions and waste management practices. However, no cruise ship is truly "green"—they all produce significant emissions and waste compared to land-based travel.

What happens to cruise ship waste in port?

In U.S. and European ports, ships must use port waste facilities to dispose of sewage, greywater, and solid waste. However, in many developing countries and small island nations, these facilities don't exist or are inadequate, so ships discharge waste at sea even in territorial waters. This is often illegal but rarely prosecuted.

Are cruise ships the worst polluters in the shipping industry?

Cruise ships produce more emissions per ton of cargo than cargo ships because they carry people and supplies rather than goods, and they operate at higher speeds. However, cargo ships carry far more total tonnage, so the industry as a whole produces more emissions. Cruise ships are the worst polluters per passenger-mile.