Experimental Studies of Thermodynamics, Kinetics and Mechanics of Carbonation of Ultramafic Rocks for CO2 Storage

Timespan: 
2009-2011

Of all greenhouse gases in the current atmosphere, it is well-recognized that CO2 represents the biggest radiative forcing on the earth’s climate (1.6 W/m2). Carbon sequestration thus becomes the critical task to retain our current climate state and mitigate the effects of projected global warming. One of many mitigation methods is to store CO2 in rocks as carbonate minerals.

Carbonate minerals can be naturally produced as weathering or hydrothermal alteration products of mafic/ultramafic rocks. This process is thought to be economically viable for removing CO2 from the atmosphere because these reactions are spontaneous and exothermic (release heat), the magnitude of mafic/ultramafic rocks is significant, and carbonate is very stable at Earth’s surface temperature and pressure. However, many questions, such as the reaction mechanisms and rates and the impact of reactions on porosity, permeability, and fluid flow, are still not yet well understood. In addition, economic, legal and policy aspects of long-term geologic carbon storage remain highly uncertain, particularly at a scale that is required to reduce CO2 concentrations to safe levels. Solving these issues is essential to apply the natural carbonation process at the industrial scale.

We will conduct experimental studies to understand the physical and chemical conditions that are optimal for storing CO2 as carbonates after CO2 reacts with mafic/ultramafic rocks. Our work has the following goals: 1) to calibrate necessary thermodynamic, kinetics and mechanic parameters to describe the chemical reaction pathways and fluid transport, 2) to use the computer program to simulate the chemical and physical processes and determine the optimized conditions for carbon sequestration, 3) to evaluate if this process is approach is economically viable under optimal conditions or suboptimal, but acceptable, conditions.

Our study is directly relevant to the key issues about carbon sequestration that could help reduce the impact of anthropogenic activities on global climate, providing much needed scientific constraints on carbon sequestration by carbonation of mafic/ultramafic rocks. It can also help to assess the feasibility and outcome of carbon sequestration strategies by injecting CO2 into brine aquifers. This study will provide invaluable knowledge regarding fundamental scientific problems such as fluid-rock interaction kinetics and deformation of the oceanic crust, low degree metamorphism during initial stages of subduction, kinetic isotope fractionation and element mobility.

Jay Ague, Department of Geology and Geophysics
David Bercovici, Department of Geology and Geophysics
Edward Bolton, Department of Geology and Geophysics
Rob Bailis, Yale School of Forestry and Environmental Studies
Shun Karato, Department of Geology and Geophysics
Zhengrong Wang, Department of Geology and Geophysics