NSW's coal seam gas industry has a “complete lack of solutions” to deal with large quantities of salt, with one pilot project alone producing five tonnes of salt a day, a report commissioned by the state's Chief Scientist says.
Since the methane is typically trapped in rock fractures that also contain water, when miners such as Santos and AGL extract the gas they also bring water to the surface, much of it highly salty.
In their report, University of NSW's Stuart Khan and Geena Kordek cited Santos' recently approved drilling project in the Pilliga Forest, in the state's north-west. It will probably produce an average of three tonnes of salt a day over three years, or as much as five tonnes daily during peak output.
The company is now building two 300-million-litre ponds adjacent to the Pilliga to hold water produced from its gas wells. Part of the operations were suspended in 2011 after 10,000 litres of untreated saline water leaked from a pipe.
While Santos is “actively exploring” commercial uses for the salt, the company's challenges are shared across the industry, Dr Khan said. “It is very surprising the complete lack of solutions at the moment for dealing with large quantities of salt,” said Dr Khan, an associate professor in the school of civil and environmental engineering. “You've got huge amounts of water and salt looking for a home.”
A Santos spokesman said “the industry has a range of options to safely and sustainably deal with the produced water and associated salt, and we continue to look at new and innovative options”.
Santos is “considering the conversion of some of the salt into saleable products such as sodium bicarbonate”, the spokesman said. “A less preferable but regulatory acceptable option would be to send the salt to waste treatment and containment facilities.”
Dr Khan said buyers of the salt will probably be hard to find after Penrice Soda, Australia's only commercial manufacturer of sodium bicarbonate – used in glass-making – ceased production this year.
He recommended CSG companies form a co-operative to make such products, even at a loss.
Much of the report's information came from Queensland's Environmental Protection Agency – where the industry is more developed – rather than the NSW Environment Protection Authority. “It took me a lot of time to get any information out of the NSW EPA, and when I eventually did, it was clear that it was not an issue they had spent a lot of time thinking about,” he said.
Economic options for salt disposal are few.
Santos said its Queensland operations are “successfully injecting salt brines ... in accordance with strict regulatory approvals”.
The report is one of a series of background studies commissioned by Mary O'Kane, NSW Chief Scientist, as part of a review of CSG ordered by the O'Farrell government.