Anglo American’s Los Bronces copper mine in Chile. Picture: ALLAN SECCOMBE
Anglo American’s Los Bronces copper mine in Chile. Picture: ALLAN SECCOMBE

High in the arid mountains of South America water is a scarce and precious commodity for copper miners. Social pressure and business imperatives are forcing companies to find innovative technologies to change the way they operate.

Anglo American, one of the world’s largest diversified mining companies, is aggressively pursuing two technologies developed in-house to reduce water and electricity consumption, minimise effects on the environment and surrounding communities and become a sustainable, long-term business.

Anglo has stakes in the Collahuasi, Los Bronces and El Soldado copper mines in Chile and is building the $5.3bn (about R78bn) Quellaveco mine in Peru, raising output to more than 1-million tons from 600,000 tons.

Both these technologies will address a broad range of growing societal and environmental pressures that mining companies are coming under from shareholders, investors and governments.

Invisible mine

“People don’t want to see a mine. That’s the challenge. How do we make a mine that’s invisible with no [effect on the environment] and we keep providing the benefits of mining to the country,” says Patricio Chacana, general manager of Los Bronces.

“How do we keep contributing to the future, taking into consideration this challenge and the aspirations of society which grants you the right to operate?” he says.

The feeling in Anglo is that it is becoming difficult, costly and time consuming to build large mines because of these issues. To keep the world supplied with the minerals it needs, fresh ways to tangibly address concerns have to be found soon.

The Quellaveco copper project, which is planned to use largely conventional mining and processes, can be retrofitted with the two new Anglo technologies to make it a more palatable investment for shareholders.

The hot topic in mining is management of environmental, social and governance (ESG) matters, an important concept for investors and funders.

“ESG forms a bigger part of that investment decision. Sometimes you find projects with wonderful internal rates of returns, but all these ESG matters and the uncertainty, particularly when you consider mining is such a long-term game ... are now forming a bigger part of that decision-making process than the financial part at some point,” says Abigail Mukhuba, finance director at JSE-listed African Rainbow Minerals.

BlackRock, one of the world’s largest asset managers, overseeing investments worth $8.6-trillion, closely considers ESG matters in deciding where to allocate funds “first from the increased relevance of this, but also thinking about how these factors will affect commodity prices,” the organisation’s MD, Evy Hambro, said at the Joburg Mining Indaba.

Fresh water

The difficulties mining companies encounter in securing continued community support, the backing of governments to grant environmental, water and mining permits, and finding the money from financiers and shareholders willing to invest in projects that will potentially harm the environment all combine in making the development of large new opencast mines unlikely, says Tom McCulley, CEO of Anglo American in Peru.

Anglo intends halving its use of fresh water by 2030 and cutting by a third both the energy it consumes and greenhouse gas emissions by then. It wants to recycle all its on-mine water in a decade’s time, compared with reusing three-quarters in 2020, says CEO Mark Cutifani.

Anglo’s copper mines in Chile and Peru are the testing ground for technologies it wants to roll out across its businesses in SA, Australia, Brazil, Botswana, Canada and Colombia.

The El Soldado copper mine in Chile is small in Anglo’s suite of mines, producing about 50,000 tons of copper a year, but it has become a vital testing ground for the sorting of mineral-bearing rock from waste rock, and coarse particle flotation to use less water in extracting minerals from crushed ore.

The exact time frame to roll these technologies out at other mines is not firm, but the intention is to do so as soon as the tests are completed, and the efficacy and cost factors fully understood.

While these are just two technologies, the benefits go beyond just their economic upside in addressing pressing challenges mining companies face in their water and electricity consumption and pollution as well as the storage of waste at processing plants.

On the horizon … some sort of dry tailings technology has to happen
Aaron Puna, CEO of Anglo American in Chile

By using less water in processing ore Anglo will be able to transition to dry tailings dumps from the conventional wet tailings dams, which have resulted in catastrophic events killing hundreds of people when they collapse, destroying everything in their path in a flood of mud and rock.

Anglo expects the Chilean government to stop granting permits from the mid-2030s for wet tailings dumps, which are essentially enormous dams of fine-grained mud coming from processing plants once minerals have been extracted.

“Everyone knows tailings dams are a problem. On the horizon ... some sort of dry tailings technology has to happen,” says Aaron Puna, CEO of Anglo American in Chile.

In Chile, the government took a much tougher line on these facilities after a spate of at least six mine dam collapses caused by an earthquake in 1965, with the worst event at El Cobre killing 200 people.

“Something like dry tailings removes that risk completely. Dry tailings are nothing more than sand. We could stack sand practically anywhere and remove the hazard,” Puna says.

“What’s clear is Chile will lead the way ... as wet tailings facilities will not be accepted in the future. That timeline is to be determined,” Puna says, adding Anglo wants to have a dry tailings plan in place by 2033, shortly ahead of its tailings permits expiring in 2036.

Negative sentiment towards wet tailings dams has strengthened after an iron ore mine’s tailings dam at Brumadinho, Brazil, collapsed in January 2019, killing 248 people.

Brazil’s state-owned Vale, which operated the mine, was also responsible for the Samarco dam, which burst in 2015, causing the country’s worst environmental disaster, killing 19 people and displacing hundreds more.

In SA, the Merriespruit tailings dam in Virginia, Free State, collapsed in 1994, killing 17 people, after a heavy downpour coupled with poor management of the facility caused the disaster. Twenty years earlier, a burst dam sent sludge pouring down a mine shaft at Bafokeng, killing 12 people.

Mines normally crush ore, or mineral bearing rock, into “bug dust”, says McCulley. Large, spinning mills driven by big electric motors use steel balls and rocks to grind the ore into a fine powder, which is fed into steel tanks where it is mixed with water and chemicals called reagents to float the copper out of the mud.

Increase recoveries

The fine dust needs a lot of water to turn it into a soup that is stirred and agitated to free the copper.

Anglo is working on a system that uses a coarser material, much closer in appearance to sea sand, which uses less water and, with a new set of chemicals, promises to increase the recoveries of copper to more than 90% from the mid-80s.

Anglo will recover 85% of water used in the coarse-particle system.

By combining the flotation system with the bulk-sorting technology, which mechanically separates waste rock from mineral-bearing ore, recoveries increase, while energy and water consumption are reduced, says McCulley.

Anglo had two options to arrest the falling grade of copper content at its Los Bronces mine. Its grade has already fallen more than a quarter to 0.75% copper in each ton of ore since 2010. This is forecast to fall to 0.5% in the next decade if nothing is done, says Chacana.

Anglo could dig a new open-pit mine, putting environmentally and politically sensitive glaciers at risk, or build a $3bn underground mine, tunnelling below the glaciers and making its operation “invisible”, says Puna.

Anglo will use tailings material mixed with cement to pump into the huge voids left underground, reducing its mining footprint, removing waste from the surface and keep the operational area stable in an earthquake-prone zone.

Anglo joins other companies in finding ways to reduce their mining footprint, prevent harm to nearby communities, the environment and water sources. The world cannot do without minerals. As miners often say when confronted by activists opposed to their operations: “If you can’t grow it, we have to mine it.”

• Seccombe was Anglo American’s guest in Peru and Chile in October 

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