Researchers at MIT have revealed that the United States has sufficient capacity to store fossil fuel emissions for a century in its deep saline aquifers. Carbon dioxide emissions are released from powerplants that use coal as fuel.
Using tiny glass beads, the researchers simulated the way liquified carbon dioxide would spread through salty water in the pores of deep rock formations. Image: Michael Szulczewski, of the Juanes Research Group, MIT
Over 40% of the global carbon emissions occur due to coal-burning powerplants. Coal cannot be avoided as it is a widely available, cost-effective fuel. Hence, carbon emissions need to be addressed. The ARCO Associate Professor in Energy Studies in the Department of Civil and Environmental Engineering at MIT, Ruben Juanes, led the research team, which included Michael Szulczewski and Christopher MacMinn, two graduate students.
Economical and practical sources of clean energy may not be enough for reducing greenhouse gas emissions. Carbon capture and storage (CCS) has been proposed for capturing fossil fuel emissions, compressing and storing them in underground geological formations. Estimations for the capacity of deep saline aquifers have ranged up to thousands of years’ worth.
The extent of deep saline aquifers has not been explored as they do not possess any commercial value. The fluid dynamics of how liquefied and concentrated CO2 will percolate through the aquifers proved difficult to model. The MIT researchers used tiny glass beads and created a model to show how liquefied CO2 percolates through salty water. They studied the micron level trapping mechanisms that existed in porous rocks and then applied the knowledge to large areas.
The study demonstrated the importance of rate of injection of CO2 into a salt water reservoir. Liquefied CO2 dissolves slowly in salt water and forms a denser, heavier fluid that sinks. This completes the process as the heavy mixture may not allow the CO2 to escape.
The study has been published in the Proceedings of the National Academy of Sciences. The U.S. Department of Energy, the Reed Research Fund, the MIT Energy Initiative, the ARCO Chair in Energy Studies and the Martin Family Society of Fellows for Sustainability provided grants for the project.