Exterra Secures $20-million Series a to Turn Mining Byproducts Into Decarbonization Gold

Cleantech company hopes to open Québec asbestos mitigation plant by 2027

Montréal-based cleantech company Exterra has raised a $20-million Series A to turn mining waste into useful materials that it says can help decarbonize a polluting industry.

Exterra has developed two techniques for repurposing mining waste: extracting minerals and storing carbon. Exterra says it has constructed a solution that takes a harmful mining byproduct—asbestos tailings—and harvests critical minerals from the waste, some of which can store carbon dioxide.

“It’s essential for the mining industry to get integrated into the circular economy to help fight the climate crisis,” Exterra CEO Olivier Dufresne said in an interview with BetaKit.

The all-equity, all-primary round was co-led by Clean Energy Ventures and BDC Capital through its Climate Tech Fund. Representatives from both are joining Exterra’s board. Other investors included the Québec government through Investissement Québec, MOL Switch, and Karpowership. The round, which closed April 1, brings the startup’s total funding to $32 million.

Exterra has developed two techniques for repurposing mining waste: extracting minerals and storing carbon. Treating the tailings with a strong acid destroys the leftover asbestos fibres, then initiates a process that leaches the rocks to form silica, nickel, and magnesium oxide — all of which Exterra can sell to industrial partners. Magnesium oxide is known for its fireproofing properties, but its traditional production is carbon-intensive.

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The startup’s second technology takes the magnesium oxide and forms magnesium carbonate in a process known as carbon mineralization. Magnesium oxide absorbs roughly 1.1 tons of carbon dioxide per ton. This sequesters carbon within the rock, allowing Exterra to put carbon credits on the market. Mining and other heavy industry activities produced 78.3 million metric tons of carbon dioxide in 2023, according to Environment and Climate Change Canada.

With the new funding, Exterra plans to launch the world’s largest asbestos mitigation plant, called Hub One, which the company claims would process 400,000 tonnes of asbestos mine tailings every year. The company is still in the pre-commercial scoping phase, with plans to open the facility in 2027 in a former hotbed of asbestos mining in Québec.

Workers at Exterra’s pilot plant site in Val-des-Sources, Que. Image courtesy Exterra.

Exterra plans to build its commercial facility in either Thetford Mines, Que., roughly 230 kilometres northeast of Montréal, or Val-des-Sources—the town formerly known as Asbestos, Que.

Val-des-Sources’ last asbestos mine closed in 2012. It once produced half of the world’s asbestos, whose uses include fireproofing and insulation. Inhaling asbestos fibres in industrial settings is associated with deadly forms of cancer. The substance is responsible for over 70 percent of deaths from work-related cancers, according to the World Health Organization.

Exterra has a mountain of work ahead of it before the facility can open. Dufresne told BetaKit that the new capital will be used to execute more pilot operations at a larger scale. The company needs to run its technology in batches continuously to get more data, complete engineering studies, and secure long-term clients before building Hub 1.

The Exterra team currently sits at 13 people, Dufresne said, with plans to expand to 20 over the next 18 months.

Workers at Exterra’s pilot plant site in Val-des-Sources, Que. Image courtesy Exterra.

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Once Exterra hits its commercialization phase, Dufresne said its revenue model will be multifaceted: selling magnesium oxide to large-scale industrial partners, selling its nickel product to smelters in the electric-vehicle battery supply chain, and selling credits on the voluntary carbon-credit market. Dufresne said all of their available credits have already been purchased by Frontier Climate and MaRS through its carbon credit repurchasing program.

Though the regulatory environment has championed increased corporate emissions disclosures, there have also been widespread rollbacks in voluntary sustainability pledges. Dufresne said he has noticed this shift, but that Exterra is lucky because its business model is not totally reliant on revenue from carbon credits.

“It’s more of a near-term shift, I’d say,” Dufresne said. “We’re talking to large producers, and they’re still moving forward with their decarbonization roadmap.”

Exterra is not the only Canadian company looking to revitalize old mining waste. BAIE Minerals, in Newfoundland, also aims to extract minerals from mining byproducts and do carbon mineralization, but through a slightly different process.

Other Canadian startups are trying to decarbonize large operations through carbon credits. Montréal-based Deep Sky is exploring an underground carbon storage facility in Thetford Mines, Que. Dufresne said Exterra’s technology is not in competition with, but rather complementary to, Deep Sky’s underground operation.

“If we look at the amount of carbon we need to capture, we’re going to need every single possible way to store it,” Dufresne said.

Feature image courtesy Exterra.