Mechanisms and applications of gas-driven mineral weathering: Implications for the geologic carbon cycle and engineered carbon storage

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The CO2-driven weathering of silicate minerals removes CO2 from the atmosphere as well as releasing nutrients essential for plant and microbial growth, whereas O2-driven sulphide weathering can release CO2. These gas-driven mineral weathering processes, followed by the precipitation of carbonate minerals in the oceans, regulate atmospheric CO2 concentrations and global climate over geologic time. Moreover, the engineering of these natural processes to accelerate CO2 storage is a promising strategy to help mitigate greenhouse gas-fuelled climate change. Although the global-scale implications of gas-driven mineral weathering reactions have been recognized, the mechanisms that control their reaction in water-unsaturated Earth materials remains poorly understood. The proposed research aims to elucidate the physical and chemical controls on gas-driven mineral weathering, and will comprise three main themes: 1) the impact of CO2 concentration on mineral weathering, 2) the role of water in mineral weathering reactions, and 3) designing engineered CO2 storage strategies. An experimental approach will be taken to determine mechanisms of gas-driven mineral weathering reactions, and reactive transport and geochemical modelling will be used to extrapolate experimental results to larger spatial and temporal scales. Fundamental mechanisms of gas-driven mineral weathering reactions revealed through Themes 1 and 2 will inform the design of engineered CO2 storage strategies that exploit natural weathering processes to capture and store anthropogenic CO2. Experiments will test strategies to optimize CO2 storage during accelerated weathering of natural rock as well as waste products from the mining industry. Fine grained waste products, known as tailings, from certain mine sites have a significant but untapped potential to capture and store atmospheric CO2. Reactive transport modelling will be used to tailor CO2 sequestration strategies to particular sites based on characteristics such as climate and chemical properties of the tailings or rock. Together, these studies will provide insight into the mechanisms that have helped moderate Earth's climate through geologic time, permit better assessment of the response of mineral weathering reactions to changes in water availability due to climate change, and contribute to the design of climate change mitigation strategies. Tangible benefits will be achieved through the production of reactive transport models that can be used by academic and industrial users to simulate the consequence of environmental change on weathering reactions, and design CO2 storage strategies. Such CO2 storage strategies will help Canada to meet ambitious greenhouse gas reduction targets. During this research, highly qualified personnel will be trained in analytical, experimental, and modelling techniques, and gain transferable skills. This skill set can be applied to environmental policy, environmental consulting, or continued academic research.