Cecil
In your recent column about pollution from cruise ships. You talked about their dumping of raw sewage into the ocean. On one of my cruises, we were told that the ship collected and processed all sewage and that no raw or untreated sewage was discharged. Were they telling less than the truth or is your information out of date?
A Florida Fool
Ok, so it’s sewage with chemicals added. Happy?
For shits and giggles, the column
Whoah the OP is an original 99’er who has 3 posts in 19 years, that blew my socks off!
Unlikely, since that’s not how sewerage is normally treated. Sewerage is normally treated by mixing it with oxygen, from air. Treating it with some other chemical – say chlorine – would require an enormous amount of the “other” chemical. Which you’d have to store, and then you’d have to dispose of any even larger volume, now contaminated with chlorine.
Enzymes are used mostly to break down fats, so that the fats don’t build up in your sewerage system. If you’re just pouring the stuff straight into the sea, there wouldn’t be much point.
I’ve heard that cruise ships are enormously sensitive about the public perception that they dump raw sewerage into the sea, And they are normally in port every couple of days. So they could be offloading all their sewerage. Or perhaps offloading some of their sewerage some of the time, and the rest of the time…
Recent rules on garbage disposal suggest that if they are disposing of sewerage at sea, they would be skimming/filtering it first (to get rid of the plastic). The next stage is settlement: if they are serious, they could be doing settlement, which would mean that they have to clean the tanks and dispose of the sludge in port. If they are doing settlement then first stage treatment would be reasonable, and they could be disposing of “treated” sewerage at sea — still sewerage, and not even properly treated, but not “raw” by careful re-definition.
If a ship of any kind is more than three nautical miles offshore, they do not have to treat their sewage.
I don’t think fish process their waste, do they? (Except by other aquatic creatures.)
For a bit of perspective on how much a billion gallons is, that’s less that the daily water usage for New York City … it’s about 5,000 cubic yards, or a layer 1 yard deep over a football pitch, per year, for all the cruise ships in the world … the three mile limit is so coastal cities can dump their sewage into the ocean …
Here’s an interesting article “Cruise Ship Fuel Efficiency” … cruise ships get about 12 feet per gallon, or close to 20 mpg per human on board … better than some rigs on the road today … a fully loaded 747 gets about 90 mpg per passenger …
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Cruise ships … jet airliners … pure luxury … these are some of the things that have to go, completely, if we want to reduce our CO[sub]2[/sub] output … just a small fraction of the people can enjoy this, most of us can’t even dream of it … especially those billion plus of us who still have to burn wood to cook meals … where a single electric light bulb at night is still generations off in the future …
One thing that rarely discussed is where these jet airliners are exhausting their engines, in the lower stratosphere … in the stratosphere, vertical motion is inhibited, thus the carbon dioxide, water vapor and soot will tend to remain at the level it’s been deposited … as The Master points out, this is only a small part of the total pollution from jet engines, however this pollution will remain where it’s left, building up, it’s still 50 maybe 100 jets at any given moment in time …
That’s a lot of soot … all so YOU can get your Amazon order in two days instead of two weeks … I hope the folk who watch the oceans boil off will forgive us …
There’s something wrong with your units here. 20 miles per gallon per passenger would imply that a cruise ship carrying a single passenger could go 20 miles on a single gallon. And that a single gallon could carry 5,000 passengers 100,000 miles! (Because 100,000 miles / 1 gallon / 5,000 passengers is 20 mpgpp.)
Consider a passenger car that gets 40 miles to the gallon. If it’s only got one human inside, that’s 40 mpg per passenger, but if you put 4 people in the car, that’s only 10 mpg per passenger. That doesn’t seem like the right metric for measuring mass fuel efficiency.
Powers &8^]
one car at 40 mpg with one passenger is 40 passenger miles per gallon
one car at 40 mpg with four passengers is 160 passenger miles per gallon
20 mpg per human on board and 5,000 crew and passengers
= 20 miles per 5,000 gallons.
maybe call it 20 mp(g times hob)
Would 17 furlongs/bushel be better? …
So if 3000 or so people ( that’s the makeup of a modest sized cruise ship) didn’t go to sea, do they still not poop?
And if they all went on a nature hike to an eco sensitive place in the rain forest instead, where does the result of their visit end up? 
You’re right: the term “eco-tourism” is an oxymoron.