The pro-scrubber Clean Shipping Alliance 2020 says more than 20 ports have committed to allowing the open-loop version of the exhaust cleaning technology — and the ones that banned it are beginning to have second thoughts.

The 36-member advocacy group, with a collective fleet of more than 2,500 ships, said on Thursday that ports across the globe have assured them they would not ban open-loop scrubbers unless "compelling new research comes to light" following meetings with the alliance's executive committee.