The U.S. may have the capacity to store about a century’s worth of America’s carbon dioxide emissions underground in deep saline aquifers, according to a study published last week by Massachusetts Institute of Technology scientists.
The scientists found that using carbon capture and storage, or CCS, is “geologically viable,” according to the study. CCS is a process that involves capturing carbon dioxide emissions at such sources as power plants and compressing and injecting them into reservoirs for long-term storage.
The nation produces about six gigatons of carbon dioxide per year, the equivalent of about twenty million barrels of oil per day, said Ruben Juanes, the researcher who led the study and a professor of energy studies in the Department of Civil and Environmental Engineering.
Researchers found deep saline aquifers – geological formations situated deeper than one kilometer underground that hold saline fluids in their pores – presented feasible storage conditions for these emissions.
Deep saline aquifers could hold up to 20,000 billion metric tons, according to the study, and CCS could hold deposits of carbon dioxide for up to 20,000 years, he said.
The nation’s carbon dioxide emission rates have hovered at about 5.5 billion metric tons per year since the late 1990s, according to United Nations data.
“Human emissions have been increasing in a sustained fashion ever since the advent of the industrial revolution,” Juanes said.
The study sought to determine the best methods for injecting liquefied carbon dioxide to increase the maximum capacity of the aquifers, analyzing such factors as injection rates and pressures. It determined the optimal conditions for employing CCS.
The study also faced constraints such as “uncertainty in geologic storage capacities and sustainable injection rates.”
It attributed the first issue to different procedures of calculating large-scale capacity. Injection rates of carbon dioxide also caused problems due to an accumulation of pressure.
In order to estimate the storage capacity for the U.S., researchers transposed data related to the behavior of fluid carbon dioxide and constraints on injection rates onto a model that applied the nation’s known deep saline aquifers, according to the study.
The aquifers are distributed throughout the country, but clusters of them center in such areas as the Southeast, including Alabama, Georgia and South Carolina, and the area bordering Lake Michigan – Illinois, Indiana and Michigan.
Storage technology similar to CSS has already been implemented in a number of places, Juanes said, in Norway and Algeria.