The cost-effectiveness of installing scrubbers has centred on the price spread between high-sulphur and low-­sulphur fuel.

But as this spread continues to erode, the added costs associated with ships being detained and fined due to the discharge of scrubber wash water could make a critical difference in the debate.

Although the International Maritime Organization considers open-loop scrubbers to be an acceptable method of compliance with Marpol Annex VI, countries around the world are taking a closer look at the impact of scrubber wash water on the environment.