I am looking at the PortStMaarten webcam right now. There are 4 ships in. I know that they have to keep their diesel engines running for power (this has been discussed here previously). Generally you do not see much smoke but the one smaller ship, Silver Wind, seems to be spewing a large amount of black smoke into the air The larger ships don't seem to be visible from their smoke stacks, better scrubbers perhaps.
Are there no industry standards for this?

David K

And now it is not emitting dark smoke. Perhaps they were incinerating some garbage?

Yes, there are standards, not just for cruise ships but for all marine shipping, and the allowed emission levels were significantly reduced as of January 1 of this year.

Have a read here: http://www.imo.org/en/MediaCentre/HotTopics/GHG/Documents/2020%20sulphur%20limit%20FAQ%202019.pdf

If you can't sleep, spend a few hours Googling "MARPOL VI" and "IMO 2020".

There are two ways to comply with the new emission levels. One is to burn cleaner (and more expensive) fuel. The other is to install scrubbers (less expensive, but then you have to dispose of the scrubbed material). You can probably guess which way many cruise ships went.

One would think that they would "scrub" while far out to sea instead of while in port. If it was done at sea, very early in the morning no one would even know. In port is the worst possible place to do it. Exposing everyone to the pollution, and the unsightly smoke that everyone has to look at is certainly a negative the Cruise line doesn't need.

Scrubbers are a part of the exhaust system, and should be in operation whenever any of the diesel engines are running. Disposal of the scrubbed matter is a different issue, which I know nothing about. Hopefully, dumping it at sea is illegal.

Then I misunderstood what they were scrubbing. It sounded like it was just a smoky residue that they had to expel into the air at some point. If it is illegal to do it at sea, how are they able to do it in Port? If it is a solid, then I agree there has to be some other way to safely dispose of it other than dumping at sea.

Wikipedia an Scrubbers:

https://en.wikipedia.org/wiki/Scrubber

Interesting. Thanks for that link.