BHP Billiton head Marius Kloppers has told European investors that Australia's carbon and mining taxes have helped to render the nation's coal industry unworthy of further investment at this time.

Despite reassuring Australians that the taxes were not to blame for BHP's mothballing of the $US30 billion Olympic Dam expansion, Mr Kloppers referred to both when telling British media that new investments in Australia's coal sector would not be profitable.

Old king coal not a very merry soul.

The comments came just hours before a joint venture between Gina Rinehart's Hancock Coal and GVK won approval from the federal government to develop its Alpha coal mine and rail project, which has previously been estimated to cost $6.4 billion.

The project had been held up by concerns it could harm the Great Barrier Reef marine zone, but Environment Minister Tony Burke yesterday said those concerns could be managed with strict operating conditions.