BHP mine shows how tailings can become a climate change-fighting ‘superpower’

Arca is trialling with BHP the use of mining tailings to absorb greenhouse gases which could remove ‘gigatonnes’ of carbon dioxide from the atmosphere.

Arca's smart churning machine in action, allowing rocks containing magnesium to absorb carbon dioxide from the atmosphere.

A by-product of mining holds the key to stripping out “gigatonnes” of carbon dioxide from the atmosphere, according to a Canadian start-up that has raised more than $12m and been testing its technology with BHP in Western Australia.

Arca has entered a new partnerships with Wyloo after testing its climate tech at BHP’s Mount Keith mine. It has also raised $US8m ($12.65m) from Side Stage Ventures and Saniel Ventures to accelerate its development.

Arca – founded by University of British Columbia researchers – uses mining tailings to absorb greenhouse gases via a process similar to corrosion, chief executive Paul Needham said.

“We’re all familiar with rust. You’ve got oxygen from the air in gaseous form that binds and forms new solid minerals – the iron oxide that we see as rust,” Mr Needham said.

“Well carbon mineralisation is similar but completely different elements at work. Carbon dioxide is the molecule in the air and it binds with magnesium … that forms new magnesium carbonate minerals.”

The magnesium, in the case of mining, is found in rock – and there is a lot of it that goes to waste in the form of tailings.

“Mining produces an enormous amount of waste. A good nickel mine might be 1 per cent nickel in the ore, maybe 0.5 per cent nickel – so 99.5 per cent of what is mined, crushed and ground into a fine powder is not nickel,” Mr Needham said.

“This is a waste material that was left behind and ignored and considered a liability. Now the mining industry is seeing that it might be an asset.”

Arca's smart churning machine.

Despite Donald Trump seeking to reverse the Biden administration’s climate policies, branding the US Inflation Reduction Act as the “green new scam”, Mr Needham says there is still a strong appetite among companies – including American ones – to slash emissions.

Amazon has been steadily increasing investments in its $US2bn ($3.2bn) Climate Pledge Fund. And its Australian arm has signed a power purchase agreement with Global Power Generation to buy 100 per cent of the electricity from its wind farm in south-west Victoria.

This is despite Mr Trump halting approvals for leases, permits and loans for onshore and offshore wind energy projects, saying they are “driving the whales crazy” and “is the most expensive energy there is”, being “many, many times more expensive than natural gas”.

“The companies that we’re working with and talking to are deeply committed. There’s more than 5000 companies that have publicly declared their commitment to get to net zero, usually by 2050, some by 2030, and the kinds of companies that are doing it tend to be companies with really strong consumer facing brands,” Mr Needham said.

An Arca technician measures flux rates in WA.

“You get companies like Microsoft that are going way up front and saying, ‘we’re going to get to net zero, we’re going to remove all the CO2 from the atmosphere that we’ve ever generated’. And we’ve already sold carbon removal credits to companies like Shopify.

“We’re continuing to see really strong interest from the voluntary carbon markets. But I really don’t think it’ll stop there. Countries like Canada and Australia have to be thinking about where their markets are and what are the opportunities for collaboration when major players are introducing new trade barriers.”

Carbon removal is not new. Geosequestration has been touted for decades as a way to remove greenhouse gases from the air and lock them in spent aquifers or other enclosed systems.

Mr Needham said Arca’s solution was simpler than geosequestration.

Arca chief executive Paul Needham.

“They’re using direct air capture technology to capture the CO2 from the air, the end result is concentrated CO2 in a tank, and then they take that or pipe that and then inject that underground. So there’s several steps in the process, all of which are very energy intensive.

“Our approach is quite different. We’re starting with minerals that have already been finally crushed. They’re already laying out in the open air, and for one reason or another, they have the capacity to capture and store CO2 all by themselves.”

But Arca isn’t a set and forget approach. The surface of tailings can harden making absorption impossible and halting the mineralisation process, so Arca uses a process called “smart churning” to keep rotating the tailings to prevent hardening and maintain absorption.

“Gigatonnes. Billions of tonnes (of CO2 absorption) is possible with this method.”

Yet the process is slow, and Mr Needham said it will use the $US8m it has raised to give the magnesium rocks “superpowers” to accelerate the mineralisation process.

“This is what we call mineral activation technology, to put it simply, we are giving this material some superpowers. So it goes way beyond what we’re doing with the smart churning today.

“This mineral activation technology uses microwave energy to effectively break apart the minerals at the molecular structure, break the molecular bonds and release more magnesium, which makes the material more reactive.”

The company has also joined the Development Partner Institute as an associate partner, to ensure traditional owners and stakeholders are engaged from the outset in designing future carbon removal projects.

Originally published as BHP mine shows how tailings can become a climate change-fighting ‘superpower’