A $1 billion concessional loan to the controversial Adani Carmichael mine project in Queensland's Galilee Basin could expose taxpayers to a high risk of losing their money, according to an independent business analysis.

The economic assessment of the troubled project's outlook found the collapsing coal price, the uncertain global picture for thermal coal, and the $21.7 billion project's heavy reliance on external financing contributed to a high risk for taxpayers.

Among the problems was Adani's hope of using the Northern Australia Infrastructure Facility to fund a key part of the project - a rail link to Abbot Point - while relying extensively for security on the availability of other, as yet unsecured, debt and equity financing.

The assessment was done by the business consulting firm, ACIL Allen, and commissioned by the Australian Conservation Foundation.