+ pollution from ships. The large cruisecos have been loath to use marine diesel so have chosen to install scrubbers which - though approved (by the U.S. E.P.A.?) - seem to work much better(or only) in the lab than in actual deployment. Use of bunker oil is otherwise forbidden within 200 miles of U.S. shores.

There's also the matter of what to do with the acids, heavy metals and other nasty byproducts of bunker fuel.

https://www.cruiselawnews.com/2019/0...ter-pollution/

Last cruise I did, the cruise line went to exclusively using marine diesel worldwide.