In order to inject carbon dioxide into the ground, Ball said it needs to be a relatively pure form of the gas.
“An ethanol plant, because the process is based on fermentation, inherently produces a relatively pure carbon dioxide,” said Ball.
That makes Ethanol plants, like the Anderson’s Marathon Ethanol Plant in Greenville, ideal for this project.
During smaller injection projects Ball said they trucked in carbon dioxide. However, in Greenville they plan to inject 1 million tons of carbon dioxide into the ground. That’s too much gas to simply truck in town.
Coal burning power plants are society’s largest source of carbon dioxide, but the carbon dioxide that comes out of the smokestacks is mixed with other gases.
Ball said there are separate projects working on separating the carbon dioxide from the other gases, so carbon dioxide injection can one can occur at all coal burning power plants.
The geology is an even more important aspect when it comes to choosing a site to inject carbon dioxide.
Ball said they look for sandstone or other porous rocks that are at least 2,500 feet beneath the surface. The porous rock level must be under a non-porous cap rock, such as granite or shale.
The carbon dioxide goes into the ground through a well under extreme pressure. When it reaches the sandstone layer it pushes the saltwater located there out of the way, and takes its place. The cap rock holds the pressurized gas in the sandstone’s pours.
“These are very similar mechanisms and similar conditions to what occur naturally and have kept oil and gas and carbon dioxide that are naturally occurring in these sandstone formations for millions of years,” said Ball.
Geologists have determined that Greenville, along with much of the Midwest, sits over what’s called Mount Simon Sandstone. This sandstone layer sits 3,500 feet below the surface.
Over that layer of sandstone is a layer of non-porous shale. Ball says this is the ideal set-up for holding carbon dioxide.
However, Ball said they will continue to do seismic testing to make sure the geologic formations are indeed what they’re looking for, before they start injecting.