A study into the viability of mineral carbonation as a means of CO2 sequestration in South Africa
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Date
2014-01-16
Authors
Naidoo, Yogandhri.
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Abstract
Long term geological storage of CO2 is currently considered a most attractive option
in the reduction of greenhouse gas emissions while continuing to utilize fossil fuels
for energy production. Mineral carbonation is a long term storage option where CO2
binds with geologic material (certain rocks minerals) to form stable environmentally
benign carbonate minerals (carbonation). Rocks containing the elements calcium
(Ca) and or magnesium (Mg) bound in silicate minerals are considered feasible for
the process of mineral carbonation. In this study a two phase assessment of the
potential for mineral carbonation as a means of CO2 sequestration in South Africa is
investigated. The desktop study investigates suitable locations of ultramafic or
silicate bearing rocks in South Africa, for the purpose of mineral carbonation.
Potential starting materials and reaction routes are addressed, as well as the slow
kinetics of the solid –fluid mineral reaction rates. Current global projects are
examined, their applicability in the South African context assessed. The
investigation, though conceptual, is hoped to add value to South Africa’s carbon
emission mitigation strategy.
The experimental study compares the data resulting from the generation of CO2
adsorption isotherms of a basalt and shale, to those generated from a coal and ash
under similar experimental conditions. As adsorption isotherms provide information
pertaining to the uptake of CO2 by a material, and not retention, a second aim of the
study attempts to determine the effect of supercritical CO2 on mineral composition of
these rocks, over a period of thirty days or so. This period of time may be
insufficient for mineral carbonation to have a detectable effect; longer term samples,
are anticipated in future research projects. It is hoped that this research will
contribute to the advancement of mineral carbonation processes, especially in South
Africa, if not globally.