Increasingly scarce metals are being recovered from mining waste by University of Queensland researchers, who are making the most of native plants’ metal-absorbing nature.

The Crotalaria novae-hollandiae – a new future of mining. Image ©University of Queensland

Dr Antony van der Ent is studying hyperaccumulator plants at the sustainable minerals institute of the University of Queensland. He says the plants have devised ways of living with these otherwise toxic elements in their leaves and shoots.

There are heavy metal hotspots around the globe, many of which Antony has visited, including New Caledonia. It was here that he saw Pycnandra acuminata, which has up to 25 per cent nickel in its latex, turning the sap a blue-green colour.

“It’s probably the most metallic tree or plant known in the world,” says Dr van der Ent.

University of Queensland’s Sustainable Minerals Institute (SMI) researcher Dr Philip Nkrumah has been developing the phytomining technology at the Centre for Mined Land Rehabilitation.

Phytomining involves harvesting metals from the living tissue of a group of hyperaccumulators, which retain metals in high concentrations after absorbing them through their roots.

“These wastes, often stored in tailings facilities, contain valuable metals including cobalt, and represent some of the largest untapped resources globally,” said Dr Nkrumah.

“Some species of plants can contain up to one per cent of cobalt or four per cent of nickel in their shoots, translating to more than 25 per cent metal in their ash which is dubbed ‘bio-ore’.

“The high purity of bio-sourced metals makes them especially suited for applications in the electrochemical industry,” commented Dr Kkrumah.

Fieldwork at the Queensland’s MMG Dugald River Mine discovered zinc hyperaccumulation in the native legume Crotalaria novae-hollandiae, which opens up the possibility of zinc phytomining.

*Article published in the October-December 2019 issue of The Asia Miner