Ship operators’ need to cut the level of sulphur emitted from the fuels they burn by 2020 is focusing minds on cleaning up their act — and the cost of doing so. They might want to start thinking a bit wider.

The debate largely revolves around the cost of fitting and using exhaust scrubbers versus burning low-­sulphur marine gas oil (MGO), which currently costs about $300 per tonne more than high-sulphur heavy fuel oil (HFO).