Photo: Denis Belitsky/Shutterstock

Where Does the Waste Go on Cruise Ships, and Is It Really Sustainable?

by Eben Diskin Mar 4, 2024

Don’t pretend it hasn’t crossed your mind. When you flush a cruise ship toilet and hear that rapid, louder-than-usual whooshing sound, you wonder as you stare at the empty bowl … “where does it all go?” On land, we have all kinds of easy explanations. We have sewer systems that pump to sewage treatment plants where the waste is processed and treated. But at sea, when you may not be making landfall for days, what happens to it?

You wander out of the bathroom and onto your private balcony, where you sit and stare out at the vast sea. Then it hits you. “What about everything else?” It’s not just human waste that seemingly has nowhere to go in the middle of the ocean, but food waste, plastic waste, and pretty much everything else we mindlessly toss in the trash. There are no dumpsters around the corner, no recycling plants nearby. How do cruise ships dispose of waste in a sustainable manner, so that doesn’t do irreparable harm to the environment?

Nothing that’s human-made in this world is 100 percent sustainable. That said, as public attention to sustainability efforts across all industries has increased, cruise ships have implemented a number of sophisticated treatment and recycling programs for everything from sewage and organic waste to landfill diversion in order to minimize the environmental impact of leisure on the water.

How waste disposal actually works

First of all, before we start talking about getting rid of waste — what happens to it on the ship? It has to be stored somewhere until it’s ready to be discharged, after all.

“Human waste is processed through our advanced wastewater treatment system,” Sarah Dwyer, Sustainability Program Manager for Virgin Voyages, tells Matador Network. “This system processes all blackwater (toilets), greywater (sinks and showers), laundry water, galley greywater, and food waste reject water to comply with MARPOL (International Convention for the Prevention of Pollution from Ships) regulations.”

The process is similar on Uniworld Boutique River Cruises although waste storage on a smaller river ship will differ somewhat from storage on a huge ocean liner.

“Human waste is collected in a tank (with a bacteria system) and this is emptied regularly, depending on where the ships are docked and whether we have access to the local sewerage system or if we have an external company coming to pump it out,” Julie Higgins, Sustainability Officer for Uniworld Boutique River Cruises, tells Matador Network. “For food waste, each ship has a geographical partner that either collects the food waste for animal feed or uses it for biofuel creation. These pickup points are fixed according to each itinerary.”

It’s not exactly surprising that cruise ships have pretty well-developed and intricate methods of getting rid of their waste. On Uniworld, both collection and offloading are more frequent, given the closer proximity of port.

Food waste is “collected by various companies, while human waste is collected in tanks on board each ship and then disposed of either directly into the city or town sewerage system,” Higgins says. “Otherwise, we have companies that come and collect it from our tanks when this is not possible depending on port facilities.”

As for larger ships like those operated by Virgin Voyages, waste must be discharged a certain distance from shore, or stored in a special recycling center for offloading.

“For our advanced wastewater treatment process, effluent (liquid waste or sewage) is held on board and then discharged at distances greater than three nautical miles from shore,” Dwyer says. “Food waste is either pulverized and discharged (12 nautical miles from shore and at a speed greater than six knots), or it’s stored in our waste recycling center to be offloaded in port.”

Is waste disposal actually sustainable?

The big complaint facing cruise lines is the issue of sustainability. From carbon emissions to how waste impacts the surrounding ecosystem, there are very real concerns about the impact cruises have on the ocean. That’s why environmental regulations are tighter than ever, and cruise lines have implemented strict treatment methods to limit any harm done by waste disposal.

“Our advanced wastewater treatment system is calibrated to meet stringent water quality standards under MARPOL and the US Clean Water Act,” Dwyer says. “Our crew ensures that our vessels are in compliance with the the National Pollutant Discharge Elimination System and Vessel General Permit, which are monitored by the Environmental Protection Agency.”

What does this actually mean? Well, everything from wastewater treatment methods to offloading strategies that divert waste from landfills.

“Our wastewater is treated by the bacteria within our tanks on board, which forms something we call ‘sludge,’” Higgins says. “We then dispose of this ‘sludge’ responsibly … over the years we have formed a reliable network that allows us to dispose in a responsible manner and not pollute the areas we sail through.”

The most visible part of Virgin Voyages’ sustainability program is its reduction of single-use plastics on board, as well as incorporating more sustainable materials for its passengers. From banning plastic utensils to using reusable food containers in restaurants, the goal is to limit how much non-recyclable waste is even produced in the first place.

“We collect and sort recyclable waste on board, which is then offloaded in our primary ports such as Miami,” Dwyer says. “We also have a recycling takeback program from our beach club operation in Bimini (Bahamas) to limit recyclable materials that would otherwise be sent to the landfill. We also vet the waste providers that we partner with on-shore to ensure waste is handled appropriately.”

In an industry that’s inherently not known for sustainability, it’s clear that cruise lines do all they can to reduce their environmental impact. But is it enough?

The impact of waste disposal on the ocean

While many cruise lines take sustainability seriously and ensure their waste management systems are up to code, that’s not always the case, resulting in harmful pollutants entering the ocean.

“Several cruise ships still use scrubber technology, which discharges a toxic cocktail of petroleum byproducts from ships directly into the ocean with little to no treatment,” Marcie Keever, Oceans Program Director at Friends of the Earth, tells Matador Network. “The ICCT (International Council on Clean Transportation) estimates that in one year, ships worldwide will emit at least 10 gigatons of scrubber wastewater, approximately 15 percent of which comes from the cruise industry.”

She also believes more oversight is needed to ensure the cruise industry’s sustainability standards are as strict as they should be. And indeed, however strict those regulations might be, without proper oversight, the rules themselves (if frequently broken) are irrelevant.

“The cruise industry remains a major contributor to air and ocean pollution, repeatedly failing health compliance and environmental tests,” she claims. “At the federal level, Homeland Security and the EPA provide little regulation enforcement and no oversight on wastewater discharge or public health, even though cruise ships continue to be a major spreader of harmful pathogens like COVID-19.”

Indeed, Carnival was fined in 2019 for dumping waste into the ocean. Apart from ocean water, Keever notes cruise ports themselves are also a serious victim of cruise ship waste.

“One community in Alaska fought hard against the industry after being filled with trash and sewage from ships,” she says. “In addition, carbon emissions from ships harm the places where they dock. Friends of the Earth is working to help ports electrify to reduce carbon emissions and improve air quality for surrounding communities.”

Just as every cruise line has its own waste processing and disposal system, each cruise line also adheres differently to sustainability standards. Clearly, most cruise lines take plenty of steps to make sure they’re handling and disposing of waste as sustainably as possible, though there will always be improvements to be made and higher standards to be reached. It’s also important to continue holding cruise lines accountable for their waste disposal processes.

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