Korea Electric Power Corp (Kepco) sought to develop the Bylong Coal project, about 200 km (124 miles) northwest of Sydney, to mine up to 6.5 million tonnes of thermal coal annually for 25 years.

But it lost its bid on Tuesday and the appeal court in New South Wales, Australia's most populous state, ordered it to pay costs.

"The appellant has been unsuccessful with respect to each ground of appeal. The appeal must be dismissed and the appellant must pay the costs," the court said.

Its ruling upheld a 2019 decision by the state's Independent Planning Commission, and a second challenge in the state's land court.

Bylong Coal did not immediately respond to a request for comment.

The IPC denial of planning approval had cited the impact Bylong would have had on water, highly productive farming country, and the climate.

"The IPC made its decision based on that evidence, finding that this coal mine is not in the public interest," the Environmental Defenders Office, which opposed the project, said in a statement.

"Two subsequent appeals have thoroughly tested and supported the IPC's decision to refuse the mine."

The United Nations has called for coal to be phased out by 2030 in nations belonging to the Organisation for Economic Co-operation and Development.

Australia is among the grouping, but its conservative government has steadfastly backed fossil fuel industries, saying tougher action on emissions would cost jobs.

Prime Minister Scott Morrison has said Australia is on a path to net zero carbon emissions but has stopped short of setting a timeline. He has said Australia will update its 2030 emissions projections going into the Glasgow talks in November.

(Reporting by Melanie Burton; Editing by Clarence Fernandez)