Mining waste puts biodiversity under intense pressure

Almost 30% of the world’s mining waste storage could threaten protected conservation areas, according to just released data in a new study published in Nature Sustainability.

The research, led by University of Queensland researcher Bora Aska for her Honours thesis, finds that 9% of the world’s tailings storage facilities are in protected areas, while a further 20% are within 5km.

Mine tailings are the residue from mining, once the minerals of interest have been extracted. They can be both waste rock and chemicals used to process ores, and they form the biggest solid waste stream in the world. And it’s getting worse.

“We’ve had a situation where the grades for ore, which is the concentration of the desired metal in the rock, have been in decline for a long period of time,” says study co-author Professor Daniel Franks, a researcher at UQ.

“For every unit of resource that the world’s trying to produce, we have to mine more material just to get that same unit. And on top of that, we’ve got greater demands for that material, for the energy transition, and for other reasons.”

These tailings can have deleterious effects on the surrounding environment if their storage facilities fail. Two recent such events in Brazil – one in 2015 and one in 2019 – resulted in the release of huge amounts of tailings into local waterways, causing 289 deaths and irreversible damage to aquatic life.

“As a result of that, the United Nations and series of responsible investors decided to drive some change in sector,” says Franks.

Franks undertook a global analysis of tailings storage facilities for the global tailings review led by the UN and the International Council on Mining and Metals.

“As part of that, they requested all the mining companies in the world disclose their information about their tailings storage facilities,” he says.

Aska and colleagues used this disclosure database to examine 1,721 storage facilities around the globe. This represents around 30% of the world’s total active storage facilities.

“Our findings suggest that mine wastes threaten biodiversity within protected areas all over the world, including eight active tailings storage dams in Australian protected areas, recognised by the International Union for the Conservation of Nature,” says Aska.

The researchers are calling for better planning around tailings facilities to prevent extra risks to biodiversity.

“One of the suggestions we make is including the environment and sensitive ecosystems in the consequence classification standards for tailings facilities,” says Aska.

They’re also suggesting that the relatively new Global Industry Standard on Tailings Management will trigger facilities to review the effect of their facilities on the surrounding environment.

“Luckily, the data needed to manage these risks is emerging, and opportunities exist to factor this knowledge into the design of new facilities, and manage those already in place,” says study co-author Associate Professor Laura Sonter, also at UQ.

Franks says there are ways to build tailings facilities that make the risk of failure much lower.

“The upstream raise style, which is the most common and the cheapest style, also has the largest number of stability issues, and largest number of failed facilities as well.”

Then, there’s an opportunity to reduce the total mass of tailings too. This is best done prior to making the tailings: it’s easier to turn ore into multiple useful things than it is to turn waste products back into useful materials.

“You want to treat the ore as having multiple commodities, and take out the large volumes of silicates that are in that ore – so you add mineral processing circuits to take that material out, and then use that as a byproduct in construction,” says Franks.

Aska is now beginning a PhD on the topic – looking specifically at minerals needed for the energy transition.

“[I’m] focussing mostly on non-metallic minerals that are usually overlooked when considering the energy transition – those minerals would be the aggregates usually needed for construction, such as sand or gravel.”