In South Australia, the trial would involve a UCG demonstration operating at the site of a coal deposit at Leigh Creek for two to three months to confirm the performance of the process.
UCG was banned in Queensland after flammable levels of hydrogen were detected in soil near the Linc Energy plant at Hopeland.
An excavation caution zone of more than 300 square kilometres was enforced.
Wilderness Society SA director Peter Owen said the South Australian government should opt for a renewable alternative.
"After Queensland has made it illegal in that state, how can minister (Tom) Koutsantonis think that it is appropriate in South Australia?" he said.
"Allowing this dirty technology in our state is completely at odds with a government that regularly flies to Paris and New York to trumpet their climate change credentials."
As minister for mineral resources, Mr Koutsantonis, will accept comments from the public on the project's environmental impact report and draft statement of environmental objectives.
But the minister said the approval of the UCG trial was ultimately out of his hands.
"The approval or otherwise of coal gasification projects should be based on science and determined by expert regulators, not politicians," he said.
"We have a very effective regulatory framework in South Australia and the merits of future projects will be assessed against that framework, not the decision in Queensland.
"We trust the scientists and independent regulators, and proponents need to prove to these regulators that they will do no harm to the environment."