When the world's largest merchant ship ferries its monthly cargo of 13,000 containers between China and Europe it burns nearly 350 tonnes of fuel a day. The Emma Maersk supplies Britain with everything from toys and food to clothes and televisions, but its giant diesel engine can emit more than 300,000 tonnes of CO2 a year - equivalent to a medium-sized coal power station...

..."Crucially, shipping exploits a ready supply of the world's cheapest, most polluting "bunker" fuel. Marine heavy fuel oil, which is burned by all large ships, is the residue of the world's oil refineries and is so thick that when cold it can be walked on. It is 60% cheaper than cleaner oils and, according to the report, demand for it is soaring.

"Bunker fuel is just waste oil, basically what is left over after all the cleaner fuels have been extracted from crude oil. It's tar, the same as asphalt. It's the cheapest and dirtiest fuel in the world," said Christian Eyde Moller, chief executive officer of the Rotterdam-based DK Group, a leading shipping technology company...."