BRISBANE - Extracting copper, nickel, cobalt and other minerals from mine waste could provide a key new source of the minerals needed for the energy transition while at the same time cleaning up old mine sites, mining executives said at a conference.

Australia by some estimates has more than 50 000 old mine sites. Its government last month released a map of 1 050 tailings sites as potential sources of metals for which demand is set to boom over coming decades for green energy products including batteries and wind turbines.

BHP estimates the world will need an additional $100-billion annually in capital investment in the resources sector to get on track to meet the Paris aligned 1.5C scenario, or twice as much copper, steel and potash and four times as much nickel in the next 30 years as it used in the past 30.

As resources with high metal content get harder to find and develop, mine waste could be an important source for metals.

"The sub 0.5% copper resources of tomorrow will be just as attractive as the 2% copper resources of yesterday, delivering the critical minerals the world needs to decarbonise at low cost," said Laura Tyler, chief technical officer at top global miner BHP.

"This means the mine waste of the past, will become some of the new resources of the future," she told delegates to a conference in Brisbane on Wednesday.

There is around five-million tonnes of copper in tailings waste in Australia alone, estimates Gavin Mudd, an associate professor at Australia's RMIT University, but it is unclear how much of that could be recovered at the sites which often also host toxic heavy metals.

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Rio Tinto has been working to find ways to take traditional mining waste and turn it into useful products, head of minerals Sinead Kaufman said at the conference.

Some 85% of Rio's waste material, or around 400 000 tonnes, from its aluminium operations in Canada is used to make new products.

It has also begun producing tellurium, used in solar panels, from waste generated by refining copper at its US Kennecott operation.

The critical mineral is difficult to mine at scale because it is usually found in small, sparse rock deposits. Rio is now ramping up its output to become the world's sixth biggest producer.

"As a result we have become one of only two producers of the critical minerals used in solar panels and other critical equipment in the U.S.," Kaufman said.

Government mapping of mine sites shows plenty of cobalt, as well as copper, nickel and other metals, Associate Professor Anita Parbhaker-Fox at the University of Queensland.

Australia is the world's third-largest cobalt exporter as well as the largest lithium producer and a significant producer of copper.

In Queensland, mapping shows plentiful cobalt at mine sites in the state's north west, while on the west coast of Tasmania state, cobalt can be found mixed in pyrite in mine waste, which can oxidise over time into acid, Parbhaker-Fox said.

Recovery of these metals will offer a chance to stop the pyrite oxidising.

"We see mine waste as a huge opportunity," said Helen Degeling, project acquisition manager at developer Cobalt Blue COB.AX.

Cobalt Blue's processing plans target pyrite, which was previously overlooked because it was difficult to process, but with cobalt in demand for battery materials, now has value.

"Turning it into a useful product has not only economic value but strong environmental positives as well," Degeling said.