Researchers discover a way to improve mining yields while capturing CO2 from the atmosphere

A University of Alberta researcher has found a way to remove carbon dioxide from the atmosphere while mining critical metals needed for renewable energy infrastructure — and has received funding to build a world-first demonstration project to prove the new solution works on a larger scale.

“To build the ‘green grid,’ we need to at least double the amount of mining we do globally to get the raw materials we need,” says Sasha Wilson, professor in the Department of Earth and Atmospheric Sciences and Canada Research Chair in Biogeochemistry of Sustainable Mineral Resources. Additionally, billions of tonnes of carbon dioxide need to be removed from the atmosphere by 2100 to limit climate warming, Wilson adds.

As Wilson explains, to create the renewable energy infrastructure required to achieve carbon neutrality, we need more of metals such as nickel, chromium and platinum, which are used in everything from batteries to electric vehicles. The problem is, current methods of obtaining these metals aren’t efficient and effective enough.

In addition, many of the metals needed to build green infrastructure are mined from rocks that are rich in minerals like magnesium, calcium and iron. The current process of extracting the metals from these rocks results in tailings, in the form of finely pulverized mineral wastes that are disposed of. However, Wilson and collaborator Jessica Hamilton at the Australian Synchrotron have found a way to extract more nickel from these tailings.

“Today a lot of nickel mines throw out about a third of the nickel they mine as waste because it’s in tailings, in a form that’s not recoverable,” says Wilson. “We’ve figured out a way to recover that nickel while sequestering CO2.”

The new process essentially solves two problems at once by increasing the yield of metals from nickel mines while also decreasing the amount of CO2 in the atmosphere.

Wilson and Hamilton, along with collaborators Andrew Frierdich from Monash University and Phil Renforth from Heriot-Watt University, recently received a $2.8-million grant from the Grantham Foundation for the Protection of the Environment that will allow them to demonstrate the process on a pre-industrial scale. By testing the method on a larger scale, they will streamline the process as well as measure how much time and energy it takes. Next steps will involve finding industry partners to pilot the process in existing mines.

Turning trash into multi-purpose treasure

The majority of mined nickel comes from deposits called laterites — a type of old, weathered soil formed by minerals breaking down over millions of years. It’s much easier to extract metals from laterites than from unweathered rocks, Wilson notes.

“You only need to know how to process one part of the laterite to get as much nickel out as possible, whereas in the type of rocks that host nickel in Canada, the nickel might be trapped in 20 different types of compound and you have to pick one or two to target,” Wilson explains. “It’s just not possible to design a mine that can extract all of it from every different type of material.”

By creating artificial nickel laterites, the researchers are able to fast-track the process of the rocks breaking down from millions of years to just a few days.

“We get the same benefit in terms of ease of processing and getting more of the resource out of the rock.”

The tailings are transformed into artificial nickel laterites through an acid heap-leaching technique that mimics the natural process. Wilson says the technique involves a neutralization reaction similar to the vinegar and baking soda volcanoes familiar to young science students.

“The acid dissolves out all the nickel and concentrates it into basically just rust. The nickel’s in the rust, and all the magnesium and calcium we need to trap carbon dioxide just falls out the bottom and we bind it with CO2 from the air.”

While the researchers haven’t yet confirmed where the pre-industrial scale testing will occur, Wilson says the new solution has a uniquely Albertan benefit.

“For nickel, it’s relevant to Alberta and the growing hydrogen economy here. You need to be able to produce a lot of nickel to process and store hydrogen.”

Learn more: University of Alberta