Sail Away to a Dirtier Future

by Kyle Medin
(Tallahassee, FL, USA)

This article was originally published on, a new site for climate change news and opinion.

Let’s talk about cruise ships.

Immense Impact of Cruise Ships

In my lead-in research for writing this, I’ve come across many articles that have talked about the immense impact that cruise ships have on the world’s oceans. A cruise ship produces (on average) 150,000 gallons of sewage per week.

This is usually treated on board (and there are regulations which require this in many countries’ waters), but in international waters it can be dumped right into the ocean.

But once again, all of these well-intentioned articles are ignoring the more scientific but much more pressing issue: it’s not what comes out the bottom, but what comes out of the top that matters.

Alarming Statistics

In an average DAY, ONE cruise ship produces as much Sulfur Dioxide as 13 MILLION cars.

In an average DAY, ONE cruise ship produces more airborne soot than 1 million cars.

There are more than 230 cruise ships operating worldwide.

Harmony of the Seas

But of course, poop is the real problem here. The “Harmony of the Seas,” expected to be the largest cruise ship in the world when it hits the water in 2016, will hold 5,479 passengers, up only 79 from the current record-holder “Oasis of the Sea”.

That is 5,479 people (plus the 2,291 crew members) producing sewage which they would have on dry land. 150,000 gallons/(5,479 passengers + 2,291 crew) = 19 gallons of sewage produced per capita per week. New toilets are required to use under 1.6 gallons per flush, but some older models use as much as 7 gallons per flush.

So, unless someone uses the toilet less than three times a week, going on a cruise is actually more fecally responsible than using an old toilet.

"But, they’re dumping it in the OCEAN."

Dumping organic matter (which may even be treated already) into a reservoir of 1.335 BILLION CUBIC KILOMETERS of water? Somehow I think we’ll manage. You know what is a real crisis of sewage? It is sewage runoff from populated areas which ends up in drinking supplies. The ocean can put up with our crap.

Air Pollution Is the Main Problem

In fact, in Friends of the Earth‘s 2013 “Cruise Ship Report Card”, the average grade for the lines judged was a C+ for sewage treatment (a few lines earning As), but an F on air pollution reduction measures (no line scored above a B).

If you are concerned about the ocean, the sulfur dioxide should bother you more anyway. Sulfur dioxide is one of the key causes of acid rain, and when inhaled can cause or exacerbate respiratory problems such as asthma and emphysema.

When SO2 in the air condenses and rains back into the ocean, the water becomes more acidic, which can weaken the shells of marine animals at the base of the marine food web.

Their defenses compromised, they are vulnerable to overpredation, which could cascade throughout the web and cause real problems.

Given the numbers above, were we to cut down to only 138 cruise ships (60% of current numbers), we would be limiting sulfur dioxide emissions more than if we were to ELIMINATE CARS ALTOGETHER.

So, yes, cruise ships are probably the least environmentally conscious way to spend your vacation. But poop freely.

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