A controversial trial for a highly polluting mining technology has been given the green light in South Australia, despite being banned in Queensland for what was described as the worst contamination in the state's history.

Key points: Controversial mining trial approved at Leigh Creek site in SA

Controversial mining trial approved at Leigh Creek site in SA The technology was legally banned in Queensland in 2016

The technology was legally banned in Queensland in 2016 Linc Energy was fined $4.5m after being found guilty of causing serious environmental harm

Leigh Creek Energy yesterday announced it had received final approval from the state's Energy and Mining Minister to commence a three-month trial of underground coal gasification (UCG) at the old Leigh Creek mine site in the state's north.

UCG — or in situ gasification — involves setting fire to coal underground to extract gas.

Conservation SA chief executive Craig Wilkins said the state's peak environment body was "outraged" that the trial had been approved.

"UCG has been banned interstate and right around the world because of the damage it causes," Mr Wilkins said.

"We simply do not believe the assurances from the company that they have finally worked out how to do it safely.

"The same claims were made by Linc Energy at Chinchilla in Queensland just before they caused such widespread devastation there. Why should we take the risk here?"

The Queensland Government banned UCG in April 2016 and the company in charge, Linc Energy, was found guilty of causing serious environmental harm in the District Court earlier this year.

Linc Energy was charged with five counts of wilfully and unlawfully causing environmental harm between 2007 and 2013 at Chinchilla and was fined $4.5 million.

Queensland's environment minister at the time, Steven Miles, described the case as the worst contamination event in the state's history.

Comparing the trial with Linc Energy is 'unreasonable'

Leigh Creek Energy executive chairman Justyn Peters said the technology had been proven with success stories across the globe.

An independent assessment found while there was much public concern about the Queensland project, "the scenario at Leigh Creek is vastly different to that at Chinchilla, in terms of geology and operations".

Linc Energy was fined $4.5 million earlier this year. ( Linc Energy )

"The State Government's environmental approval for this project came on the back of an expert independent assessment report developed to summarise potential issues and environmental risks associated with the Leigh Creek Energy trial, and how they will be managed," Mr Peters said.

He said a start date had not been locked in for the trial but its approval would show that UCG could be a viable gas production technology used in the future.

He hoped the trial would prove that, with the correct regulatory framework and site, in situ gasification could be done in a safe and environmentally sustainable way.

"There's still a lot to do on site, but preparations are underway for commencement in the coming weeks," he said.

"In the meantime, Leigh Creek Energy is continuing its ongoing process of keeping the local community and its shareholders informed of our progress."

Mr Peters said the trial would attract a larger workforce to the site and the company did not expect any offsite impacts to residents during the period.

The trial has been approved at the old Leigh Creek mine site. ( ABC Rural: Courtney Fowler )

Opposition from traditional owners

Coal was mined at Leigh Creek between 1888 and 2015.

Adnyamathanha traditional owner Vince Coulthard said it was time for the area to be "left alone".

"We're very concerned because people live in that area and it's time for healing of the site, not any more destruction," Mr Coulthard said.

"It's going to pollute that whole area and poison it — that's our concern."

He hoped Premier Steven Marshall, who is also Aboriginal Affairs Minister, would use a measure in the Aboriginal Heritage Act to stop the trial.

"The Premier needs to look at it very, very seriously," Mr Coulthard said.

"I'm hoping they will reverse it.

"I've had discussions with the Mines Minister and the Premier and it seems unlikely they will reverse it but you can only hope."

Energy and Mining Minister Dan Van Holst Pellekaan said there were always risks with projects like this, but the short-term pilot plant had been investigated thoroughly, and would run in a very controlled and temporary situation.

"After the pilot plant is completed, all consultation with local people with regard to the environment, with regard to cultural issues, with regard to every issue that exists starts again," he said.