What happens when you flush the loo on a cruise ship?
The largest modern cruise ships, such as Harmony of the Seas, carry more than 6,500 passengers and 2,400 crew. That’s a floating population greater than the number of residents of the City of London, and equivalent to a town the size of Towcester.
Just how does a cruise line deal with the amount of waste created during the course of a voyage? Not just human waste, but leftover food, bottles, cans, cardboard, paper – everything we are accustomed to disposing of in our wheelie bins or recycling boxes.
Cruise lines get a bad rap when it comes to pollution. Among those pointing the finger is Friends of the Earth. A recent report from the organisation propounded the misconception that all cruise ships are nothing more than floating monstrosities, dumping millions of gallons of raw sewage and other pollutants into the world’s oceans.
The industry's image was not helped last year when Princess Cruises was fined a record ￡32 million for using a “magic pipe” to illegally off-load pollutants into the waters off the UK coast – albeit oily bilge water rather than human waste.
Such incidents are rare, however, and in the case of Princess Cruises it was a rogue engineer who was found to be at fault rather than a systematic failure of procedures.
According to environmental regulatory lead at Royal Caribbean International, Nick Rose, the idea that cruise lines go round dumping stuff in the ocean is just wrong. “Our multi-stage treatment systems exceed the requirements of all international regulations,” he says.
This is how it is done. For a start, there’s a lot of liquid to deal with every day. Even with aeration systems designed to reduce the amount of water coming out of bathroom taps and shower heads, the average ship will use average of 40-50 gallons per passenger per day.
The “grey water” from galleys, laundries and bathrooms is first mixed in carefully measured proportions with the “black water” lavatory waste before bio reactors deep in the bowels of the ship set to work.
There, all the nasty stuff is filtered out and digested by bacteria. The remaining liquid is disinfected by UV radiation rather than chlorine or other chemicals that would themselves be harmful to marine life.
At this stage, and having been monitored for any remaining bugs such as faecal coliform, it is discharged into the sea “cleaner than the seawater that it might have started out as before being desalinated,” according to Rose.
Because it is so clean, some ports have given approval for it to be discharged closer than the statutory 12 miles from land.
About three tons of solids left from the original 1,200 tons of waste per day is incinerated or contained until it can be offloaded.
Every ship has its own environmental officer and the crew are responsible for their own recycling. Cabin stewards, for example, separate the paper, plastic, metal and glass from cabin waste bins.
All glass – including thousands of drinks bottles – is separated into different colours before being crushed and bagged. All paper, apart from any that has been contaminated by food, is baled and landed for recycling.
Cardboard is the largest solid waste product by volume, and that too is separated, bound, baled and landed ashore.
The way that cruise ships handle waste is governed by strict international maritime laws (administered by the London-based International Maritime Organisation - a United Nations agency).
Its MARPOL (marine pollution) code prohibits any vessels or offshore platforms from disposing of any form of plastics, cooking oil and incinerator ash into the sea.
Some areas of the world, including the Baltic Sea, the Black Sea, the North Sea and the Caribbean and Antarctica have specially-protected status with even tighter regulations.
Disposal of waste in ports is just as carefully controlled and cruise lines go to great lengths to ensure that as much as possible is recycled rather than sent to a landfill.
The code of conduct enforced by the Cruise Lines International Association is even stricter.
Spokesperson Christina Perez said: “The cruise industry pioneered and operates advanced systems that reduce and often eliminate refuse and wastewater.
“While ocean-going ships can release untreated sewage into the ocean if they are at least 12 miles from land and traveling at a required speed, CLIA ocean-going Cruise Line Members must verify each year their full implementation of CLIA’s Waste Management Policy, which prohibits the discharge of untreated sewage at sea, anytime, anywhere, around the globe.
“This policy far exceeds the legal requirements and the existing regulations of the vast majority of the maritime industry. The advanced wastewater treatment systems used on many ships can produce cleaner water than most wastewater treatment facilities in US coastal cities.”
Britain’s biggest cruise line, P&O Cruises, says: “We recognise that without appropriate treatment the waste generated on board our ships, together with the fuel and other products we use to transport, feed, entertain and take care of [our passengers] could have an impact on the environment.
“Our waste treatment facilities ensure that all waste water is appropriately managed to minimise its impact upon the oceans. All general waste is treated on board to reduce its volume prior to landing ashore, and wherever possible general waste is recycled.”
“Everything we dispose of is sent for recycling. None of it ends up in landfill,” said Rose. And as an incentive to the crew, every penny earned from that recycling is paid into the staff welfare fund.
That’s something to remember every time you flush your cruise ship toilet or throw a leftover daily programme into the waste bin.