From waste to resource: exploring beneficial reuse options for brine

CSIRO scientists have recently completed a year-long project to help answer some of those questions. The research addressed both the technical aspects of brine reuse options, and the social and economic implications of different choices.

“It’s very important to consider the social implications of technologies and infrastructure projects right up front before anything is deployed,” says Dr Andrea Walton, Acting Group Leader with CSIRO’s Adaptive Communities and Industries group.

“In order to do that, you need to engage with the community. It’s not just a question of putting information up on a website. You have to go and talk to people directly; you need to listen and understand what the concerns are so community voices are being heard.”

The Narrabri Gas Project

In 2020, Santos was granted approval by State and Federal governments to extract coal seam gas from the Gunnedah Basin in the Narrabri region of northern New South Wales. Like all coal seam gas projects, the Narrabri Gas Project (NGP) is expected to generate large volumes of produced water, which will be treated through the reverse osmosis process and will create brine as a by-product.

Brine is a highly saline by-product of coal seam gas extraction that will be produced in large volumes if the Santos NGP goes ahead as planned. Recent technological developments, driven by interest in the recovery of useful salts and critical minerals, biofuels, and energy production and storage, raise the possibility of beneficial reuses of brine. 

Although regulations allow for disposal if other options aren’t available, the Development Consent for the NGP, which was published by the Independent Planning Commission of NSW, has a preference for undertaking beneficial reuse options where feasible.

“The waste hierarchy says that you have to make your best efforts to ensure beneficial reuse rather than simply dumping the brine,” explains Dr Prashant Srivastava, a soil contaminant chemist who led the CSIRO project.

“What the community needs is clear, reliable information about whether brine can be beneficially used for alternative purposes and, if so, what would the potential impacts of those options be – both in terms of risks and in terms of benefits. That’s what we have tried to provide through this project.”

Exploring the options

There are a range of potential beneficial reuse options for brine, and the research team selected five to investigate in depth. For each one, they undertook a 30-year techno-socio-economic analysis. The five options were:

• recovery of high-purity salts for industrial applications
• recovery of critical minerals and other important elements
• acid mine drainage neutralisation
• high-value algae cultivation
• energy harvesting and storage

“Our overall finding was that three of these options were potentially beneficial,” says Dr Srivastava. “The recovery of critical minerals and other important elements was not shown to be economically viable. And, unfortunately, energy harvesting and storage was not shown to be a viable option either.”

The findings for the remaining three beneficial reuse options – selective salt recovery, acid mine drainage neutralisation and algae cultivation – were much more promising.

Selective salt recovery employs technologies to generate salt products from brine for potential beneficial uses. Preliminary tests on brine samples from the Narrabri site showed a concentration of 64% sodium carbonate – which can be converted into sodium bicarbonate – and 20% sodium chloride.

“Currently, all the sodium carbonate or soda ash that we use in Australia is imported,” says Dr Srivastava. “It is used in industrial processes like glass manufacturing, soap and detergent production, and paper processing. Sodium bicarbonate is also very useful in our everyday lives. We examined two different processing options for salt recovery – Solvay and Sal-Proc – and discovered that, from an economic perspective, Sal-Proc yielded a positive net present value of $17 million over 30 years.”

Acid mine drainage neutralisation, the process of using brine to neutralise the acidic mine heaps produced during mining processes, was also shown to have a positive net present value. Beyond the economics, this is an appealing option because of its potential contribution towards a more sustainable mining industry and a circular economy for brine.

“The last option we looked at was high-value algae cultivation,” says Dr Srivastava. “Some algal species are salt tolerant – you might even say that they love salt – and there is potential to use the NGP brine ponds to cultivate algae that can then be processed into high-value products. This is a process that can take place in tandem with other options to bring co-benefits. For example, you could focus on algae cultivation and then, when that pond is fully utilised, you could move to selective salt recovery and acid mine drainage neutralisation.” 

The importance of community engagement

While the techno-economic analysis of each brine reuse option provided valuable information to support industry decision making, the research team were also keen to take a broader look at the social implications of each option. This included potential benefits, such as local job creation and training opportunities, and potential risks, such as adverse environmental or health impacts.

The project team held workshops with local community stakeholders in the Narrabri region (local government, small and medium sized businesses (SMEs), farming groups, and other community members) to seek their views on the five options, and to capture their questions and concerns before feeding these back to the technical scientists.

“We find when we seek stakeholder feedback, there are often recurring themes across different projects and different regions,” says Dr Walton. “We know there will likely be environmental concerns and social impact concerns. But then it’s important to dig deeper and learn about the specifics of what matters to people – whether that’s a big environmental footprint, use of scarce water resources, a long construction phase that might impact housing, or whatever it happens to be for that community.”

“In the context of beneficial reuse of brine from the NGP, some of the key questions were around job creation – not just about how many jobs but about the longevity of those jobs. There were also questions about opportunities for SMEs and local businesses to get involved, and questions about ongoing monitoring for adverse impacts.”

Dr Walton also notes that there was some important feedback from the community about using clear, transparent language to communicate the findings of the study, for example, through using relatable examples or comparisons when talking about water volumes.  

The technical and economic analysis, in addition to the community engagement, will help to inform decision making.

“As scientists, it’s not our job to make the decision about which option is the best one,” concludes Dr Walton. “But what CSIRO can do with our approach to the research – an approach that is very broad but also very well integrated – is look at social, economic and technical considerations, and provide that information in a way that is helpful to communities as well as to industry and government.” 

The project is now complete and the results are available on the GISERA website.

You can also learn more about our projects on the social and economic impacts of the onshore gas industry.