Comment pubs.acs.org/est
Environmental and Geochemical Aspects of Geologic Carbon Sequestration: A Special Issue CO2 migrating from storage zones − especially capillary trapping, solubility trapping, and mineral trapping (discussed in the feature article) will also be governed by geochemical processes. This special issue of Environmental Science & Technology provides a panorama of current research on environmental and geochemical aspects of geologic carbon sequestration. It includes a feature article by the guest editors, and three critical reviews. The state of knowledge of caprock sealing mechanisms is examined in the first review, the second review evaluates how leakage may impact the geochemistry of aquifers and the vadose zone, and the third review explores the partitioning behavior of organic compounds in carbon sequestration environments. The reviews are followed by six papers on CO2 dissolution in brines and adsorption on minerals relevant to storage formations under geologic sequestration conditions. The focus then turns, through 14 papers, to CO2 interactions with three classes of minerals (carbonates, silicates, and aluminosilicates) when CO2 is injected and present in saturated brines. Next, five papers investigate physical-chemical processes involved with wetting phenomena, ganglion dynamics, viscous fingering, and CO2 trapping. Finally, ten contributions examine various processes relevant to the potential for leakage and transport out of storage zones, and to the monitoring of leakage. The coupling of chemical and physical processes is critical to the integrated assessment of GCS. The geochemical process studies presented in the special issue provide base-level science to inform the development and application of integrated performance assessment models for geologic carbon sequestration. In the U.S., the Department of Energy (DOE) has been developing one such modeling framework, CO2-PENS (Predicting Engineered Natural Systems), a comprehensive system-level computational modeling framework for performance assessment of geologic sequestration of CO2. CO2-PENS encompasses a (nonstatic) group of models that collectively enable probabilistic simulations of CO2 capture, transport, and injection in geologic reservoirs (Stauffer et al., Environ. Sci. Technol. 2009, 43(3):565−570). Integrated performance assessment is the organizing framework for research being conducted by the U.S. DOE and other organizations around the world. To advance prospects for implementation of geologic carbon sequestration, it is important for research to be aligned with an integrated framework for analysis of performance and risk. Such focused research will yield an improved understanding of the technology in ways that matter to the public and to companies that will be charged with implementing a very much needed technology.
T
he need to reduce atmospheric CO2 emissions from combustion of fossil fuels becomes more clear each day with the availability of new supporting information on, for example, global temperature, ocean levels, ice cover, extreme weather events, and ecological change. According to estimates from the International Energy Agency, total global emissions of CO2 were approximately 31.6 Gt in 2011, up from 23.7 Gt in 2001 and 21.1 Gt in 1991. Because of the long residence time of CO2 in the atmosphere, it will be necessary not only to stabilize CO2 emissions, but to decrease them significantlyin the order of 80% by 2050to avoid scenarios of warming, coastal inundation, drought, flooding, and other impacts with negative social and economic consequences that will be very difficult to manage. Due to the enormous amount of CO2 produced each year, the Intergovernmental Panel on Climate Change of the United Nations, as well as many other international bodies, has recognized that geologic carbon sequestration (GCS) will be an important part of any group of strategies to reduce CO2 emissions. Approximately 60% of global emissions of CO2 are from point sources such as electric power plants and cement kilns for which CO2 capture and geologic sequestration technology could be implemented. Since the late 1990s, a large amount of research and development on GCS has been undertaken to develop the technology and reduce its costs, and to assess technology performance and risk. While the individual components of CO2 capture, transport, and subsurface injection technology have existed for many years, they have not been integrated and implemented at anything approaching the scale needed for significant reductions in CO2 emissions, except for a small number of initial demonstration projects. Research is being conducted in Australia, Europe, the U.S., and elsewhere to enable large-scale field testing of carbon capture and geologic sequestration systems across a wide range of capture, transport, injection, and storage scenarios. Complementary research is being performed to develop improved scientific understanding of the fundamental physical and chemical processes involved, and to build models to simulate GCS technology performance and associated risks. Understanding of geochemical processes is critical for optimizing and controlling geologic carbon sequestration, and for assessing its risks. The ability to maintain injection rates into a porous formation over decades, and to maintain porosity in formations receiving fluids never before present is entirely dependent on geochemical processes. Interactions of the injected CO2 (and impurities remaining after capture from flue gases) with brines and hydrocarbons present in the receiving formations under high pressures and temperatures will yield solutions and mixed phases with unusual properties that will determine the performance of GCS. The interactions of these fluids and mixtures with the receiving formation and with overlying caprock also will determine the potential for fluid migration and leakage. The effectiveness of several important trapping mechanisms for © 2013 American Chemical Society
Young-Shin Jun*,† Daniel E. Giammar† Charles J. Werth‡ David A. Dzombak§
Special Issue: Carbon Sequestration Published: January 2, 2013 1
dx.doi.org/10.1021/es304681x | Environ. Sci. Technol. 2013, 47, 1−2
Environmental Science & Technology
Comment
†
■
Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States ‡ Department of Civil and Environmental Engineering, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States § Department of Civil and Environmental Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
research and teaching focus on the transport and fate of pollutants in surface water and groundwater systems, and the development of sustainable technologies for water treatment. His specific research interests include reactive transport mechanisms of pollutants in porous media, catalytic reduction technologies for oxyanions and halogenated organics in drinking water, and the fate of legacy/emerging pollutants in urban watersheds.
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
David Dzombak, the ES&T Associate Editor who collaborated in development of the Special Issue, is the Walter J. Blenko, Sr. University Professor of Environmental Engineering at Carnegie Mellon University. He is also Director of the Carnegie Mellon Steinbrenner Institute for Environmental Education and Research. His research is focused on topics in water quality engineering, and energy and environment.
Biographies
Young-Shin Jun is an Assistant Professor in the Department of Energy, Environmental & Chemical Engineering at Washington University, where she leads the Environmental NanoChemistry Laboratory (http://encl.engineering.wustl.edu/). Her research group aims to provide environmentally sustainable CO2 sequestration strategies, improve our understanding of the fate and transport of contaminants and nanoparticles, and elucidate physicochemical reaction mechanisms occurring during managed aquifer recharge to secure drinking water sources.
Daniel Giammar is an Associate Professor in the Department of Energy, Environmental and Chemical Engineering at Washington University in St. Louis. He is currently a Kenan Visiting Professor at Princeton University in the Department of Civil and Environmental Engineering and the Andlinger Center for Energy and the Environment. His research focuses on reactions that affect the mobility of metals, radionuclides, and inorganic contaminants in natural and engineered aquatic systems.
Charles Werth is Professor, Associate Head, and Director of Graduate Studies and Research in the Department of Civil and Environmental Engineering at the University of Illinois at Urbana-Champaign. His 2
dx.doi.org/10.1021/es304681x | Environ. Sci. Technol. 2013, 47, 1−2
