An ancient geological formation, predating even the dinosaurs, is now at the forefront of discussions about Australia’s green energy future. Geoscience Australia is investigating a substantial salt deposit found in Queensland’s remote Adavale Basin as a novel solution for underground hydrogen energy storage. This ambitious project holds the potential to supply electricity to millions of homes across eastern Australia, directly addressing the nation’s looming renewable energy storage deficit.
The Adavale Basin is situated beneath the Queensland towns of Quilpie, Blackall, and Charleville, and importantly, it lies above the Great Artesian Basin (GAB), which is the largest underground freshwater reservoir globally. As Geoscience Australia concluded its $31 million drilling project in the region, a primary concern for local residents revolved around the potential impact on their sole reliable water source.
An “On-Demand” Underground Battery
The Adavale Basin, first identified in 1958, has long been considered by geologists to be “under-explored” and notoriously challenging to study. It is buried beneath the Eromanga and Galilee Basins, both significant rock formations that are part of the wider Great Artesian Basin. Crucially, there is no surface indication of the Adavale Basin’s presence. What makes it particularly unique is its possession of the only discovered layer of rock salt in eastern Australia that is potentially thick enough to facilitate the deep underground storage of hydrogen energy within the Earth’s crust.
This specific salt deposit, known as the Boree Salt deposit, has been highlighted by Mitchell Bouma, Geoscience Australia’s head of advice, investment, attraction, and analysis. He explained that the deposit could be leveraged to construct artificial, battery-like containment units.
“You can dissolve that rock salt out and you can store things within that dissolved cavern, like hydrogen gas or compressed air,” Bouma stated. “You can produce these things [hydrogen gas] out there, pump them into the cavern, and it’s basically this on-demand battery that’s under the ground.”
The concept of storing hydrogen gas in underground salt caverns is not new; it has been implemented internationally for decades. The Teesside facility in the United Kingdom, for instance, has been operational since 1971.
Mark Bunch, an independent energy geoscientist from the University of Adelaide, underscored the “enormous potential” of such storage methods. “You go underground because of the scale,” Bunch noted. “We can store all kinds of industrial gases and other chemical products at the surface in huge tanks, but you can do it at a much vaster scale (hundreds of cubic kilometres) if you go underground.”
In the United States, the Advanced Clean Energy Storage hub, currently under development in Delta, Utah, plans to utilise two salt caverns, each capable of storing 5,500 metric tonnes of working capacity. A collaborative venture between oil giant Chevron and Mitsubishi Power, the company estimates that the equivalent megawatt-hours of energy stored in one cavern would necessitate over 40,000 shipping containers filled with lithium-ion batteries.
Dr Bunch’s analysis suggests that a mere handful of artificial caverns within the Adavale Basin could potentially power 20 million homes daily, based on the average household energy consumption in Brisbane.
Depth Perception and Community Concerns
To thoroughly assess the viability of storing hydrogen in the Adavale Basin’s salt caverns, geologists undertook a significant drilling operation in November. They bored a 3-kilometre deep borehole directly into the Boree Salt deposit, setting a new depth record for Geoscience Australia. The operation yielded a substantial 976-metre solid rock core, over 500 rock chip samples, and several groundwater samples for analysis.
Mr Bouma, who managed the project, emphasised the cost-effectiveness of underground energy storage compared to surface-based alternatives. He pointed out that it bypasses the substantial “surface infrastructure costs” associated with above-ground solutions. A single cavern is estimated to have the capacity to hold approximately 6,000 tonnes of hydrogen, which translates to about 100 gigawatt hours of energy – a figure comparable to roughly 50 of Australia’s largest existing super battery installations.
However, the prospect of these underground energy storage facilities has not been met with universal enthusiasm by residents living in the vicinity. Their primary concern is not the energy potential but the potential for catastrophic events.
Andrew Martin, Mayor of the Blackall-Tambo Shire, representing approximately 1,900 residents, expressed caution regarding any development that could compromise the region’s vital and consistent water supply. “It’s the precautionary principle,” Martin stated. “If you get one increase in pressure in the Great Artesian Basin, or one movement of the subterranean plates, or some catastrophe somewhere, somehow, it just beggars belief.”
Conversely, Dr Bunch offered reassurance regarding the safety of pumping hydrogen gas into underground salt caverns. He argued that the interaction between salt and gas makes damage to the Great Artesian Basin unlikely. The critical factor for safe gas storage is maintaining precise pressure levels. While insufficient pressure in surface tanks can create a dangerous vacuum and excessive pressure can lead to explosions, the behaviour of salt underground offers a unique safety mechanism.
Dr Bunch explained that even in a “worst-case scenario” involving a rock fault caused by incorrect pressure, the salt would deform into a “toothpaste-like substance.” This material naturally adjusts to pressure variations, effectively preventing further movement or damage to the surrounding rock. “This shouldn’t ever be much of an issue because salt is free to move,” Bunch commented. “In the scenario [of a fault], the salt would move to fill the space, shrink and be pulled in.” This movement, he elaborated, would distribute any stress, thereby mitigating further damage to other rock strata. Importantly, this process would occur approximately 2 kilometres below the groundwater sources essential for drinking water and agriculture. “I just don’t see it as a scenario that would play out,” Dr Bunch concluded. “It’s a different scenario to storing gases in other rock types that might be more brittle.”
Geoscience Australia plans to utilise the collected samples to conduct detailed analyses of the region’s mineral and groundwater resources, with initial findings anticipated by mid-year.
Despite these reassurances, Mayor Martin remains steadfast in his call for more comprehensive evidence. He insists that any future exploration of the Adavale Basin must demonstrably serve the best interests of his community. “You cannot guarantee that this is absolutely fail-safe for time immemorial,” Martin asserted. “Take the community with you, otherwise you’re going to have a constant set of worry beads going on about what the bloody hell are they doing to our lifeblood?”
