KNOT Offshore Partners (KNOP) plans to pass on installing exhaust gas scrubbers to become compliant with the pending IMO 2020 low-sulphur mandate.

"We build ships at Tier II because actually, weirdly, ships with scrubbers are less efficient, and they've got more deadweight," chief executive John Costain said during the company's second-quarter conference call.

He said a scrubber-equipped vessel will burn up to two more tonnes of fuel a day, given the added weight, and open-loop scrubbers discharge sulfates into the sea.