Abstract

Australians are among the world’s largest human per capita contributors to carbon dioxide emissions. In 2008 the most populous state of NSW accounted for 158.2 Mt of these emissions, with 76 Mt of NSW emissions from stationary sources, such as power plants. NSW has not located adequate porous and permeable sedimentary basins to sequester carbon dioxide in underground reservoirs. Mineral carbonation is an alternative method of reducing emissions of CO₂ by chemical reaction with magnesium or calcium-bearing rocks to form insoluble carbonates, which bind CO₂ in a form that is stable over geological time. Current methods seek to replicate the natural weathering process of silicate rocks such as peridotite and serpentinite to form carbonates such as magnesite, but reduce the time for the carbonation reaction to proceed. New processing approaches focus on environmentally sustainable aqueous reactions which eliminate the use of acids, and biodissolution of reactants or precipitation of products using bacteria, which would reduce the energy penalty. Value-added by-products which could offset costs include magnesite, magnetite, silica, heat, nickel and chromite. Refractory magnesite bricks are currently used for a variety of steel-making and other furnaces, and potentially for insulated housing. The aim is to approach the estimated cost of geosequestration, which is possibly grossly underestimated due to inherent variability of each individual basin. Mineral carbonation should be evaluated in NSW, and other countries where geosequestration is a less than viable option in the short term. The mineral carbonation process represents a stable solution to storing carbon dioxide, without risk of leakage, without the need for monitoring and with the promise of products which will make the process economically viable.