REPROCESSING AND RETREATMENT
The re-cycle
A way to recover minerals , remediate land and lower environmental liabilities , reprocessing and retreating waste streams could prove integral to mining companies ’ social licence to operate in the future . Dan Gleeson explores some of the technologies being developed to facilitate the process
Retreating tailings or waste dumps to obtain valuable minerals was considered ‘ novel ’ a decade ago : the work of a few specialist companies outside of the mainstream mining markets .
As ore grades have continued to plummet , remediation considerations have risen up the agenda , and sustainable mining practices have been championed by various stakeholders , the concept has gained in popularity .
In the South African PGM space , for example , Jubilee Metals continues to mine a rich vein by assembling and extracting metals from a growing portfolio of assets . In the country ’ s gold sector , DRDGold and Pan African , among others , are finding rich pickings from old tailings assets .
In Australia , New Century Resources has left off where MMG curtailed operations at the Century zinc operation by recovering value from waste streams , and the partners of the Greenbushes lithium operation have made plans to take reclaimed tailings from an existing tailings storage facility and upgrade the contained lithium content to produce a saleable lithium concentrate .
In the US , Barrick recently cut the ribbon on a Tailings Reprocessing Project at its end-of-life Golden Sunlight Mine , seeking to remove and concentrate sulphur contained in iron pyrite for use at its majority-owned gold operations in Nevada . At the same time as this , the company is removing a source of potential groundwater contamination .
In Spain , meanwhile , First Quantum Minerals has come up with a method to reprocess tailings from already mined material , which was expected to yield around 22,000 t of copper and help bridge the gap between the cessation of open-pit mining and the commencement of an underground operation .
The examples are far , wide and growing , hence the reason many more equipment , process and service providers are getting involved .
The big three mineral processing OEMs – Metso Outotec , FLSmidth and Weir Minerals – have all developed reprocessing business streams , explaining that mining ‘ waste ’ can provide value not only as recovered metals , but also as a construction material that can be sold to third parties or integrated into their own infrastructure projects .
Metals without mining
EnviroGold Global ’ s circular-economy business model is designed to produce precious , critical and strategic metals while reprocessing mine waste ( tailings ).
Its analytics-driven approach to project origination and development leverages extensive mine and mill production data , and geological records to identify tailings sites expected to contain significant quantities of residual metals due to refractory mineralogy and / or the inefficiency of outdated technology used during legacy mining operations , the company says .
In addition to recovering metals , the company
A second lease of life : New Century Resources plans to produce 110,000-130,000 t of zinc metal from the Century Mine in its 2022 financial year
remediates the tailings footprint consistent with environmental best practices , thereby reducing the environmental footprint of legacy mining . This approach , which eliminates the extractive phase of metal production , can reduce the energy intensity of metal production by over 80 %, EnviroGold claims .
After signing a series of binding agreements with Hellyer Gold Mines Pty Ltd in Australia and the owners of the Buchans River Delta Reclamation Project in Canada , EnviroGold , last month , was able to display the sustainability credentials of its model to the wider investment community .
It announced that the precious ( gold , silver ) and battery metals ( copper , zinc , lead ) to be produced at the company ’ s Hellyer Tailings and Buchans Tailings reprocessing projects were expected to show a 96 % reduction in greenhouse gas ( GHG ) intensity per gold-ounce-equivalent produced and an over 80 % reduction in energy intensity relative to industry averages for conventional mining .
The calculations , based on the framework set forth by the World Resources Institute ’ s Greenhouse Gas Protocol and assessments of expected Scope 1 and Scope 2 emissions for the company ’ s planned operations at the Hellyer Tailings and Buchans Tailings reprocessing
36 International Mining | APRIL 2022