T309 Mining and the Environment: Addressing Common Challenges Faced across the Mining Industry (Posters)

Wednesday, 22 October 2014
9:00 AM - 6:30 PM
Exhibition Hall C

STRATEGIZING CARBON-NEUTRAL MINES: A CASE FOR PILOT PROJECTS

Paper number: T309-10
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

Ultramafic and mafic mine tailings are a valuable feedstock for carbon mineralization that should be used to offset carbon emissions generated by the mining industry. Carbon mineralization occurs via kinetically controlled mineral-microbe-fluid-gas reactions in an environment that is readily accessible for isotopic, mineralogical and geochemical characterization. Observations from mine sites in Canada and Australia suggest passive carbonation of ultramafic mine tailings can be significant: on the order of 10-4 to 10-2 tonnes of CO2 per tonne tailings per year, which can represent a substantial, but not total, offsetting of a mine’s greenhouse gas emissions1. Carbon mineralization can be accelerated through abiotic and biotic processes that drive silicate and hydroxide mineral dissolution and carbonate precipitation. For instance, silicate dissolution may be accelerated by at least one order of magnitude through bioleaching using Acidithiobacillus spp2. Subsequently, phototrophic microbes (algae and cyanobacteria) can promote carbonate precipitation from leachate waters through the alkalinization of their microenvironment2. The use of phototrophic microbes has the advantage that biofuel and other value added by-products could be produced concurrently with carbonate minerals. The supply of CO2 is often rate-limiting for carbon mineralization in mine tailings, yet can be enhanced through tailings management practices and use of CO2 point sources1,3. Highly reactive phases, e.g. brucite [Mg(OH)2], a minor tailings mineral, can be rapidly carbonated by supplying gasses with elevated CO2 partial pressures into mine tailings3. CO2 injection into mine tailings could act as a testing facility and offer valuable insights for injection into geological formations. Mining environments that contain vast quantities of pulverized ultramafic rock represent a valuable carbon sink that could be an economically efficient alternative to other technologies currently under development for carbon sequestration. Scenarios for pilot scale projects are proposed with the aim of moving towards carbon-neutral mines.

1Wilson et al., 2014, Int. J. Greenh. Gas Control 25: 121-140.

2Power et al., 2011, Environ. Sci. Technol. 45: 9061-9068.

3Harrison et al. (2013) Environ. Sci. Technol. 47: 126-134.