Over 6,000 feet below the surface of southwestern Kansas lies the Arbuckle Aquifer, a thick layer of permeable rock saturated with saline water unfit for human consumption. However, according to Saugata Datta, associate professor of geology at K-State, the Arbuckle could prove useful for something other than providing drinking water: the permanent sequestration of carbon dioxide emissions.
Datta has been working in conjunction with researchers from universities and industrial companies around the country on a multiyear project investigating the feasibility of storing carbon dioxide, a greenhouse gas that occurs naturally in the atmosphere and as a byproduct of burning carbon-based fuels, in the Arbuckle.
“Fossil fuels are almost all carbon-based, so when you burn them to do anything, you’re producing this carbon dioxide,” said Ben Champion, director of sustainability at K-State. “Carbon dioxide, as well as methane and other greenhouse gasses, are absorbing heat and changing the heat flow in the atmosphere, and that’s where climate change comes from.”
Datta said the project began with what he called a reconnaissance phase in 2011 and 2012 in which he and other researchers surveyed the land, studied the composition of the rock and experimented with the chemical reaction between the gaseous carbon dioxide and the native rocks.
“The majority of scientists believe that there is some human control of the amount of CO2 being added to the atmosphere,” Datta said. “What is there, is there, so the question becomes, what do you do to mitigate this type of an issue? One of the ways to do it is through geological storage.”
Geological storage, according to Datta, consists of gathering carbon dioxide and injecting it deep into the subsurface, where it could be stored for a long period of time.
“Once the CO2 is piped down, from either the atmosphere or the industry where it’s being produced, it can be sequestered by means of forming new minerals,” he said. “Essentially, the CO2, in that state, under that pressure, usually can be locked up and formed into new minerals.”
Datta added that once these new minerals are formed, they typically don’t dissolve back into a gaseous state. This means that CO2 can essentially be stored indefinitely.
“The chemistry is very solid. It’s very easy to prove that this should happen,” he said. “But we always make sure. We have to be careful that no hazards or environmental issues can erupt from such a broad endeavor.”
Datta said that K-State’s responsibility in the project is the geochemical research. The researchers are looking at the chemistry of the formation water and the rock surrounding it.
“If we know what the quality of the water is before CO2 is injected, then you can monitor and see how the water is changed after the CO2 is injected,” he explained. “Similarly, we look at the structure of the rock, if there are any fractures or discontinuities that could be detrimental to CO2 injection, in case it can be released through these cracks back into the atmosphere.”
Brent Campbell, graduate student in geology, began working with Datta on the project this semester.
“I’m coming in for the second half of the project,” said Campbell, who said his role is to work on a model for the long-term storage of CO2. “Increases in atmospheric CO2 leads to global warming and other atmospheric issues. We need some place to get rid of the source of that, and sequestration has a lot of potential for that.”
Although Champion says that carbon capture, if it proves to be effective and economically affordable, could be helpful for the atmosphere, it is only a temporary solution.
“It’s an attractive technology, but it’s essentially just an add-on to our existing, coal-based energy system,” he said. “The more investments you make in that system, the more committed you are too it; so if, ultimately, we need to get away from those systems long-term, this is definitely something that’s going to buttress and support that side of the industry.”
Champion also said that anyone who’s serious about dealing with climate issues will take an “all of the above” approach, which includes carbon capture as well as increased use of renewable energies.
“We’re going to need a lot of different strategies to power our society sustainably,” he said. “I think we also need to be challenging our consumption habits and figuring out how much energy we really need to maintain a high quality of life.”
According to Champion, the bottom line is that if factors that contribute to climate change can be mitigated, they should be, but that’s just a small step.
“If we can take the emissions that are currently being produced at these plants and eliminate them from the carbon cycle, then that’s really an important step that needs to happen,” he said. “In the long term, though, I do think we need to question the entire infrastructure of our oil-based energy system.”
Datta said that the next step of the study is the injection phase, in which 40,000 metric tons of compressed CO2 captured from the Abengoa Bioenergy Corp. plant near Colwich, Kan. will be injected into the Arbuckle aquifer. The researchers are working closely with the Environmental Protection Agency to ensure no damage is done to the geological or biological features in the area.
“If this turns out to be a feasible way to do it, and everything works out, we will try to find other reservoirs for the CO2, and it doesn’t have to be just saline aquifers,” Datta said.
Datta also acknowledged that human society will continue to have to deal with CO2 as a byproduct.
“We are an oil-dependent society, and an energy-dependent society,” he said. “For our energy to be coming from these natural resources, we have to understand that this byproduct will be there. You can imagine that the whole industry will be able to benefit tremendously if it works.”
The project, which is funded by grants from the U.S. Department of Energy, will have benefits even if carbon dioxide sequestration doesn’t work out as expected.
“Whether the technology works or not is certainly a big part, but we already have a big thing that we accomplished,” said Datta. “We know our subsurface. We know what’s under our feet in Kansas much more clearly than we ever have.”