Maersk say that despite the financial sweeteners from Singapore's Maritime and Port Authority the company is actually losing money by using low-sulfur fuel that can cost twice as much as ordinary bunker fuel.

CNN: Shipping looks to clean up its act

That means shipowners who wish to ply these waters will have to stop using bunker fuel (the cheap stuff left over once petrol, diesel and aviation fuel have been distilled from crude oil) to power their vessels because burning it produces too much sulphur dioxide, nitrogen oxides and soot.

ECONOMIST: Marine technology: A voyage of discovery | The

Another is the gritty bunker fuel burned by the many ships in a once-fragrant harbour.

ECONOMIST: An encouraging appointment addresses an enduring problem