Love them or loathe them, the allure of a cruise holiday is undeniable. Enthusiasts wax poetic about how cruises offer the perfect blend of relaxation and adventure, a magical passport to exotic ports of call, interspersed with sublime moments gliding across the open ocean on a colossal vessel. To their harshest critics, cruise ships are floating monstrosities, obscene monuments to extravagance and excess, a slap in the face to Mother Nature and a smokestack-shaped middle finger to coastal communities.
As the cruise industry comes roaring back to life post-pandemic, frustration over cruise ship pollution is escalating. One of the cruise industry’s most vocal critics is Friends of the Earth, which publishes a Cruise Ship Report Card that rates the environmental performance of 18 different cruise lines. In 2022, as in the nine previous Report Cards, the industry received mostly failing grades for sewage treatment, air pollution reduction and water quality compliance.
The price of cheap fuel is dirty air
For decades, most cruise ships have run on heavy fuel oil (HFO), also known as bunker fuel, a cheap and dirty fuel that emits harmful sulphur dioxide (SOx), which is known to cause eye, lung, and respiratory tract damage. When mixed with water, SOx forms corrosive sulphuric acid and leads to acid rain. A 2019 study found that the outdoor air quality on cruise ship decks in open water was comparable to highly polluted cities in China.
In 2020, the International Maritime Organisation (IMO) set a cap on the sulphur content of marine fuels, but provided a loophole. Ships can continue to use high-sulphur HFO if they install exhaust gas cleaning systems, known as scrubbers, to reduce emissions. These scrubbers work by spraying alkaline water, usually seawater, into the ship’s exhaust stacks. Scrubbers are designed to reduce sulphur levels, and studies show that they don’t reduce emissions of harmful particulates or soot.
Despite the new rules, according to a recent report, Europe’s 218 cruise ships “emitted more SOx than one billion cars in 2022, or 4.4 times more than all the continent’s cars,” leaving Europe’s port cities “choking on toxic air pollution from cruise ships.” In Barcelona, Europe’s most polluted port, “cruise ships emitted almost three times more SOx than all the cars in the city.”
Most cruise ships run their engines around the clock when at port, generating electricity to power their onboard systems and serve their guests. Only 35% of cruise ships operating today are able to “plug in” to shore-side power grids when docked, and most of the world’s ports are not yet electrified. The EU has mandated that by 2030, European ports must install enough shore-side power connections to meet the electricity needs of docked cruise ships and ferries, and ships will be required to plug in. Spanish ports such as Valencia and Barcelona are currently building electrical substations to comply with the regulation.
Turning air pollution into water pollution
Scrubber effluent and sludge, which is highly acidic and contaminated with heavy metals and nitrates, is often discharged directly into the ocean, essentially turning air pollution into water pollution. Many ports, such as Vancouver, have now banned the discharge of scrubber effluent while at anchor or berth.
Europe is moving towards stricter rules on scrubber and sewage discharges, which critics say are too lax and often not enforced. For example, current international rules allow ships to discharge treated sewage within three nautical miles of shore and raw sewage beyond 12 nautical miles. Cruise lines have been sanctioned repeatedly for illegally polluting the oceans. Satellite data on global scrubber effluent shows that many of the most affected areas coincide with popular cruise ship routes and ports of call, particularly in the Caribbean and the Mediterranean
What is the industry doing about it?
For their part, cruise lines claim to be going green, with many of the latest mega-cruise ships powered by liquefied natural gas (LNG), a cleaner-burning fossil fuel. While this should eventually help improve the air quality in ports of call and eliminate the need for scrubbers, environmentalists point out that this fuel is actually worse for the climate than HFO because the low-pressure, dual-fuel engines used in cruise ships leak large amounts of unburned methane into the atmosphere, a potent greenhouse gas much worse than carbon dioxide.
So if the cruise industry was serious about going green, what would it look like? Environmentalists suggest that a good start would be to immediately phase out the use of HFO worldwide and switch to the lowest sulphur fuel available; stop using scrubbers and install efficient particulate filter systems; stop dumping all waste, including sewage, within 24 nautical miles of any coastline; halt investment in LNG and redirect resources to zero-emission strategies, including sustainable fuels such as green hydrogen; and commit to using 100% shore-side power by 2025 and pay for the cost of building electrical substations in ports of call with limited resources.
Many holidaymakers overlook the cruise industry’s poor environmental record or the high carbon footprint of a cruise holiday, focusing instead on the price being low enough that they can afford to go. But in order to deliver that affordable price, cruise lines have for decades externalised environmental costs, choosing dirty fuel over clean air, or dumping at sea over responsible waste management on land. This has been a winning strategy for the bottom line, but a losing strategy for human and planetary health.
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