CARBON MINERALIZATION FIELD TEST AT THE KING CITY ASBESTOS CORPORATION (KCAC) JOE PIT MINE

Carbon mineralization is a promising method to remove carbon dioxide from the atmosphere to halt and reverse climate change. Medium to large scale field trials are critical to advancing the science. California has an ideal location for such field trials – the former King City Asbestos Corporation (KCAC) Joe Pit Mine located in the New Idria serpentinite. In Phase I we characterized the site to determine whether reactive material is still present in the mine waste rock and the background rate of CO₂ uptake using dynamic closed chambers (DCC) and eddy covariance (EC) systems in tandem, supported by mineralogical and radiocarbon analysis. We found that the near-surface mine waste contains magnesium carbonates and hydrotalcites, indicating past carbon mineralization. Brucite is consistently present and abundant at depths below ~40cm, indicating significant unreacted material at relatively shallow depths. The DCC and EC methods showed a net uptake of CO₂ of 1.03 and 1.24 kg CO₂ m^-2 yr^-1, respectively, and radiocarbon analysis of surface carbonates indicated the incorporation of atmospheric carbon. In the current phase we are seeking to accelerate the rate of CO₂ uptake by exposing unreacted material below the surface, using the same methods as Phase I to verify the rate of uptake and source of CO₂.

An additional objective of the project is to assess the potential human health and safety risks of conducting carbon mineralization in chrysotile asbestos-bearing rocks and mine waste. The field research team has been working closely with environmental health and safety experts to measure exposure to asbestos. Monitoring of personnel indicates asbestos exposure is well below regulated limits for all activities to date.