Test work conducted by the University of British Columbia (UBC) on mineralised material from the Turnagain nickel project has demonstrated significant mineral sequestration of carbon dioxide (CO₂), supporting owner Giga Metals’ ambition to build a “true” carbon natural mine.

Test work shows that the greenhouse gas is absorbed by exposing tailings or other waste rock to the atmosphere, which converts the host rock minerals to carbonate minerals, locking away the CO₂ for geological time periods.

Giga Metals president Martin Vydra says Turnagain could achieve carbon neutrality without purchasing carbon credits.

“As the only North American undeveloped nickel deposit of this scale solely focused on the Class I and the battery chemical market, we think our emphasis on low carbon and other ESG principles will make us a desirable source of battery metals for electric vehicles,” he comments in a statement, announcing the test results.

The test work was conducted by a team led by UBC’s Dr Greg Dipple, who has been studying mineral sequestration of CO₂ in mine tailings around the world for more than 15 years and whose work has recently been cited in the MIT Technology Review outlining the potential for mineral carbonation processes to permanently sequester vast amounts of CO₂ and the interest that is being shown in generating carbon credits through this form of sequestration.

Dipple explains that the initial testing of the Turnagain material took place over a four-week period and showed average absorption rates of 2.7 kg CO₂/m²/y for the control sample, with absorption continuing at this rate over the four-week test period. 

A second sample was tested with periodic mixing of the tailings layer, reflecting potential active management of a tailings facility; this second sample showed a sustained increase in carbon sequestration rates of 25%.  During periods of optimal moisture and mixing, the sequestration rates increased up to three times the long-term average. 

In the 2020 preliminary economic assessment (PEA), Giga Metals disclosed expected emissions from a commercial operation of less than 2.5 t CO₂e/t of nickel produced in concentrate with a diesel haul fleet and less than 0.75 t CO₂e/t of nickel produced with an electrified haul fleet. This is an order of magnitude lower than the global weighted average of 25.6 t CO₂e/t of finished nickel reported by Wood Mackenzie.

At the demonstrated basic sequestration rate of 2.7 kg/m²/y and factoring in the tailings management facility size used in the PEA, Giga Metals estimates that about 900 000 t of CO₂ would be sequestered over the mine life, or 0.72 t CO₂/t of nickel produced. Seasonal variations and management strategies may cause CO₂ sequestration rates to vary. This sequestration rate would make Turnagain a carbon neutral project if an electrified haul fleet becomes available.