Japanese trading house Itochu Corporation agreed to buy the 15% stake for $345 million in December.

Aston’s net profit after tax reached $242.9 million for the year ending in June while the next month it paid off the remaining debt that was borrowed to acquire the Maules Creek project in the Gunnedah Basin of New South Wales off Rio Tinto subsidiary Coal & Allied for $480 million in 2009.

Tinkler’s purchase was struck as Rio sought to sell off various assets around the globe to reduce debt levels during the global financial crisis.

Aston still has other debts and secured $350 million in revolving credit facilities from ANZ and Macquarie Bank during the recent financial year.

The explorer said a corporate loan facility of $175 million and a bank guarantee facility of $60 million remained undrawn.

But both of these facilities can be ramped up to a total of $350 million once the Maules Creek project receives its environmental approvals.

The environmental assessment application of the project is under public exhibition and is under the NSW government’s Planning Assessment Commission for review.

Aston said the PAC must provide its report to the state’s planning minister by December 16.

“All planning approvals are now expected in the first quarter of calendar 2012, and first commercial coal is expected in mid-2013 – ramping up to 10.5 Mtpa by 2015,” the explorer said.

Aston shares are unchanged at $10.02 this morning.