The 850-well project, which is currently before the Independent Planning Commission (IPC), would likely produce as much as a b-double truck of salt per day during full operation. Disposing of the waste has long been a problem for the industry.

In early July, the company revealed they had been in a year-long negotiation with major American firm Natural Soda to convert the waste by-product into baking soda in a new Narrabri factory. Soda ash, used in glass production, is another option.

But University of NSW professor Stuart Khan said residents should take that promise with a grain of salt.

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He said it was "unreasonable" for the company to announce the plan just 13 days before the start of public hearings into the scheme this week.

"I think people would be forgiven for being cynical about it given that timing," he said.

"If they were keen on producing soda ash then this is an opportunity that's been sitting before them for a long time, for well over a decade," he said.

"It shouldn't be something pulled out of a hat in order to charm the very last stage of the approvals process. If there are real market opportunities there and there are real benefits then why is it happening now? Why not a decade ago, and why not with other sources of produced water?"

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A Santos spokesperson said the company is "very serious about this concept study".

Asked a series of questions as to whether the proposed project could be feasible, whether there would be contaminants to be dealt with, and whether the company anticipated making a final investment decision before the end of the year, the spokesperson said Santos hoped the study would lead to a new industry for Narrabri and Australia.

"Natural Soda is a well-established company with a strong track record in sodium bicarbonate production in the United States," they said.

Dr Khan said if the plan really it should be made a condition of approval of the project by the IPC.

But he said the project doesn't have a business plan, which he said should exist before approval of the controversial 850-well gas project.

"This is the only long-term sustainable solution that's been floated. Therefore I think the whole project should rest on its viability."

Dr Khan, a Professor in the School of Civil and Environmental Engineering at UNSW, has been calling on the industry to investigate alternatives to dumping salt since 2013.

That was the same year Australia's last producer of the product Penrise soda stopped producing it in South Australia, forced by the country's high dollar to instead import it.

He conceded the region would be an unusually good one for the plan compared with other regions where gas wells exist.

When contacted for comment Natural Soda referred the Leader to Santos.