Adani has announced it's giving the green light to the Carmichael coal mine in Queensland's Galilee Basin.

Adani chairman Gautam Adani says pre-construction works for the $16.5 billion Carmichael projects will start in the September quarter of 2017.

But the announcement begs more questions than it answers.

Where's the money coming from?

To date, 19 banks have refused to finance the multi-billion-dollar venture — Westpac being the latest.

Some made the decision because of climate change policies, or the risk of exposure to an asset that could become stranded as the world prices out fossil fuels.

But they are not the only concerns. Adani's financial woes are also raising issues for financiers.

The Indian conglomerate is carrying a huge debt burden. It's facing pressure to cut debt and divest assets, including its ownership of the Abbot Point Coal Terminal in Queensland.

Adani recently told authorities its giant power station at Mundra, Gujarat — which is meant to take 60 per cent of the coal — may not be commercially viable because of rising costs for imported coal.

There has been speculation the Commonwealth's Export Finance Investment Corporation could step into the breach and finance the Carmichael mine — something the Government has not formally ruled out — but this would be a controversial step fraught with risk for taxpayers.

If the mine goes ahead, how extensive will the project be?

The world's biggest export coal venture, and the biggest mining site in Australia, was the project's promised, or threatened, scale, depending on your point of view — five underground pits, two massive, open-cut mines, exporting 60 million tonnes of coal.

But Adani has recently scaled back its ambitions, signalling, at least initially, the mine's output would be far smaller — about 25 million tonnes a year.

Some in the industry believe it could produce as little as 5 million tonnes, and coal industry analysts are not anticipating any output for at least four years.

A map showing the Adani Group's Carmichael coal mine and rail project as of March 2015. ( Sourced: adanimining.com )

Will Adani be granted a government subsidy?

Adani has asked the Government to subsidise the building of a railway from the mine site to the export coal terminal. And it appears the request has been answered.

Encouraged by the federal and Queensland governments, Adani applied last year for a concessional loan of up to a $1 billion from the Government's Northern Australia Infrastructure Facility (NAIF) to help cover the cost of building the railway.

The NAIF is yet to make an announcement, but the Minister for Resources and Northern Australia, Matt Canavan, appeared to pre-empt its decision in his press conference by speaking as if the railway funding was a done deal.

Queensland has already acceded to Adani's desire for a subsidy on mining royalties. ( AAP )

Queensland has already acceded to Adani's desire for a subsidy on mining royalties.

The state Labor Government's decision not to give an outright "royalties holiday" to Adani was interpreted as a tough stance.

But allowing a mining company to delay the payment of royalties still amounts to a subsidy under conventional definitions used by the Productivity Commission Trade and Assistance Review (p.17) and the World Bank.

Queensland Premier Annastacia Palaszczuk has reaffirmed this policy will apply to any new mines in the Galilee or Surat coal basins.

In other words, both the state and federal governments are prepared to offer subsidies and incentives to companies wanting to open mines in new coal regions.

This will certainly dismay climate scientists who want to limit the burning of coal, which produces greenhouse gas emissions, to limit global warming.

The Federal Government maintains the Carmichael mine will not worsen climate change and may be a net positive for the environment because the mine's clients — mainly Adani power stations in India — would otherwise get coal elsewhere.

The counter argument is that opening up a new coal basin and adding new coal supplies to the global market — potentially huge new supplies — will push down the price of coal and encourage the use of this greenhouse-gas emitting and polluting energy source.

That's economics 101.

How many jobs will the project create?

The state and commonwealth governments appear to be placing a priority on jobs, but how many jobs is debatable.

Certainly not the 10,000 direct and indirect jobs Adani continues to publicly claim its venture will create.

The Queensland Land Court rejected this claim as "overstated" in its decision to grant environmental approval for the mine.

It accepted the estimate of Adani's own expert witness that the mine and railway would create 1,460 jobs in net terms, with the judge saying he would write to the Federal Environment Minister to make this clear.

Despite this, federal ministers and the state's Premier continue to adopt and promote Adani's "10,000 jobs" claim.

Mr Canavan cites the potential for up to 16,000 jobs if the coal reserves in the Galilee Basin are fully exploited. But that's a big if.

Solar power prices have crashed to such an extent that new solar projects are now cheaper than coal in India.

Economics may yet defeat plans to exploit the untapped new coal reserves in Australia, where climate science has failed.