The company's CEO Somruedee Chaimongkol, in an interview with CNBC this week said that the publicly-traded company was committed to transforming the company into a leader in clean energy.

According to Banpu's 2020 annual report, 95 per cent of the company's profits came from coal investments. Ms Chaimongkol has signaled her intention to slash that to 50 per cent by 2025. CNBC also reported the company "won't invest in new coal assets".

The Energy Australia-owned Mount Piper power station is currently supplied by Centennial Coal Springvale Colliery, which is forecast to run out of viable reserves by 2024.

By then, Centennial Coal hopes to have received planning approvals to reopen and expand its mothballed Angus Place colliery.

The expansion will destroy several wetland ecosystems by cracking the underlying rock formations and draining them of water.

"In the circumstances, the Energy Australia should be investigating alternative coal supplies in the short-term and a more rapid switch to renewables in the medium-term," Nature Conservation Council Chief Executive Chris Gambian said.

"With global coal companies shifting from coal to clean energy, diversifying Lithgow's economy is more important than ever. Last week, Energy Australia announced plans to establish a pumped hydro facility near Lithgow, which will help the city maintain its position as a key player in the state's electricity sector.

"Lithgow is the centre of several other clean-energy projects, including a big battery and an eco-precinct on the old Wallerawang power station site and a push for an electric bus manufacturing plant.

"These sorts of initiatives will help Lithgow thrive as the economy moves past coal-fired power to clean, renewable wind and solar.

"The energy future beyond coal is starting to take shape."