Recovering and re-mining mine waste is a credible and potentially financially alluring prospect as the mineral intensity of the clean energy transition requires new solutions to avoiding supply shortfalls.

The World Bank has indicated the production of minerals, such as graphite, lithium and cobalt, could increase by nearly 500 per cent by 2050 to meet the growing demand for clean energy technologies.

It estimates that more than three billion tonnes of minerals and metals will be needed for the wind, solar, geothermal power and energy storage requirements of projects to be built to meet carbon reduction targets.

With existing resources either depleted or declining in quality, and new resources proving hard to find and mine, meeting part of the supply gap may be in plain sight – the detritus of past mining operations.

The Minerals Research Institute of Western Australia says the value of precious, critical, and strategic metals contained in tailings worldwide is estimated to exceed US$3.4 trillion.

Dr Dave Lawie, Chief Geoscientist with global mining-tech company IMDEX, says technology has a role to play in characterising the tailings and defining the ore to enable extraction.

He said as well as re-assessing tailings, there has also been a shift in sentiment, particularly in Europe, in support of bringing old mines back into production.

“You could probably bring these mines back with much less local community and environmental impact and much better ESG credentials,” Dr Lawie said.

“There seems to be a realisation now that we do need these metals and it seems to be becoming more acceptable now to try to restart this activity in Europe.

“To do something with the tailings you need to understand what is in the tailings, some of which have been in place for 100 years and there’s no record of what is in them.

“But if you want to make a case to re-open them in some way it’s very difficult to make an economic case unless you know what’s in them, and that’s the role of technology.”

In Australia, the Federal Government has released an Atlas of Australian Mine Waste, in collaboration with Geoscience Australia, RMIT University, and the University if Queensland.

Federal Resources Minister Madaleine King said it could provide industry with additional opportunities to extract valuable resources from previously mined rock and earth.

“Some of the minerals we need now, and into the future, may not just be in the ground – they’re also in rock piles and tailings on mine sites around the country,” Minister King said.

“These minerals might not have been of interest when first extracted but could now be in hot demand as the world seeks to decarbonise – for example, cobalt in the tailings of old copper mines.

“This new Atlas puts these potentially lucrative sites on the map for the first time and may open new sources of critical materials.”

So far, the Atlas had identified 1,050 sites across Australia as possible sources of critical minerals.

“Our resources sector is the key to our net zero future – and this is another tool developed by Government to help facilitate the discovery of critical minerals in a more efficient, sustainable way – and to the highest standards,” Minister King said.

“Reprocessing rocks and earth that have been previously excavated during mining operations can give new life to old mining towns, create jobs and rejuvenate local economies.”

Dr Lawie said re-processing offered value by recovering valuable material in tailings left behind by past inefficient mining practices, finding new uses for the tailings, and by creating value from an asset that would otherwise be carried as a liability by mining companies.

“Some of the older processing plants and processes weren’t that efficient compared to today’s technology and the recovery might have been 70 per cent to 80 per cent which means 20 or 30 per cent of the valuable material is still sitting in the tailings,” Dr Lawie said.

“Another value is in the material itself. There is research being done because material that has been through processing and are in tailings is special material.

“Groups such as Regeneration  are involved in research to determine what you can turn tailings into.  and they’re developing projects focused on remining and restoring legacy mines.

“If we put our minds to it, we’d probably be able to transform them into specialised building materials; they’ll have certain thermal capacities, we might be able to make insulation panels, or bricks that are resilient to losing heat in houses.

“Then there is putting a dollar value on the liability mining companies carry for the tailings.

“Re-processing the tailings means you can potentially turn it into something valuable, and there are environmental credits for remediating these areas.”

Regeneration Chief Innovation Officer John Thompson told an IMDEX Tech Symposium in Vancouver earlier this year the company’s aim was to capture the metals and minerals from mine waste and put it back into the supply chain or repurpose materials for other uses.

Earnings and credits are used to help fund restoration of nature and bring closure to communities and the reclaimed minerals and metals would help to meet increasing demand.

“This is a real challenge. It’s easy to say we are going to remine waste, but it is difficult to do. We will need technologies and partners,” Mr Thompson said.

Rio Tinto was Regeneration’s first investor and is a site and technology partner.

“There are hundreds of thousands of sites, a huge amount of material to work on; legacy messes that we as an industry have left. How can society like us when we leave these scars, so we have to address them and that’s what Regeneration is about.

“If we are copied and others followed our lead, that’s a fantastic outcome. We all own this space.

“Re-mining is not a new concept, but making it pay for the restoration is the innovation we are trying to establish.

“Tailings reflect the change in the mining operation over time and the change in grade, mineralogy, character, so characterisation of tailings is just as important as characterisation of ore bodies.”

ABOUT IMDEX

IMDEX is a leading global Mining-Tech company, which enables successful and cost-effective operations from exploration to production. The ASX listed company develops cloud-connected sensors and drilling optimisation products to improve the process of identifying and extracting mineral resources for drilling contractors and resource companies globally. IMDEX’s unique end-to-end solutions for the mining value chain integrate its leading product brands. Together they enable clients to drill faster and smarter, obtain accurate subsurface data and receive critical information in real-time.