Daniel Giammar, Walter E. Browne Professor of Environmental Engineering, Dept. of Energy, Environment and Chemical Engineering, Washington University
Abstract: Geologic carbon sequestration (GCS) is a potential strategy for mitigating the impacts of anthropogenic CO2 emissions on climate change. Fractured basalts are one of the geologic formations being considered for GCS. These formations have iron(II)-, calcium-, and magnesium-rich silicate minerals that can result in extensive trapping of CO2 in stable carbonate minerals. The pore space available for storage and fluid transport in such formations resides primarily in fractures. A series of laboratory experiments was performed to fill knowledge gaps regarding the location, mechanisms, and extents of mineral trapping in fractured basalts. Experiments were performed with natural basalts and with olivine, which is the most reactive mineral present in basalts. The solids were loaded into bench-scale reactors as either fractured core samples or packed beds of powdered solids and then immersed in CO2-rich aqueous solutions. While only limited magnesium, iron, and silicon were released from the solids to the aqueous solutions outside of the pore space, the conditions within the fractures and packed beds were favorable for the precipitation of magnesium and calcium carbonates. Geochemical gradients caused by diffusion of inorganic carbon and magnesium led to spatial localization of carbonate mineral precipitation, and the timing and location of precipitation could be predicted using a 1-dimensional reactive transport model. Carbonate minerals were observed using electron microscopy and identified using Raman spectroscopy. In situ measurements with forsterite using 13C nuclear magnetic resonance (NMR) spectroscopy were able to track the chemical speciation of the added inorganic carbon over time. The evolution of the pore space during reaction of the basalts and mineral powders was observed using X-ray computed tomography (CT). Collectively the observations indicate that mineral trapping within fractured basalts can be rapid and extensive.
Short Biography: Daniel Giammar is the Walter E. Browne Professor of Environmental Engineering in the Department of Energy, Environmental and Chemical Engineering at Washington University in St. Louis. Professor Giammar's research focuses on chemical reactions that affect the fate and transport of heavy metals, radionuclides, and other inorganic constituents in natural and engineered aquatic systems. He is particularly interested in reactions occurring at solid-water interfaces. His recent work investigated the removal of arsenic and chromium from drinking water, control of the corrosion of lead pipes, geologic carbon sequestration, and biogeochemical processes for remediation of uranium-contaminated sites. His current and recent research has been sponsored by the National Science Foundation, Department of Energy, and Water Research Foundation. Professor Giammar received a National Science Foundation Faculty Early Career Development (CAREER) Award in 2006. He has active collaborations with faculty in Earth and Planetary Science, Chemistry, and Social Work that enable interdisciplinary investigations of important environmental systems. Professor Giammar is currently an Associate Editor of Environmental Science & Technology and a member of the Journal Editorial Board of Journal American Water Works Association. Professor Giammar completed his B.S. at Carnegie Mellon University, M.S. and Ph.D. at Caltech, and postdoctoral training at Princeton University before joining Washington University in St. Louis in 2002. In 2012-2013 he was a visiting professor at Princeton, and he visited the University of Vienna in 2007 as a guest professor.