Converting flue gas emissions into biofuel may seem like a pipe dream, but a groundbreaking process at Duke Energy’s East Bend Station in Boone County could make it a reality.
The Kentucky Department of Energy Development and Independence and the University of Kentucky are partnering with Duke Energy on the project, which converts the carbon dioxide in flue gas to algal biomass. The biomass is then periodically harvested to supply feedstock for upgrading into other products.
To put it in layman’s terms, pond scum feeds on a diet of carbon dioxide from a smoke stack and is then used to make stuff. Potential uses for the product, in addition to biofuel, include fertilizer, animal feed and the omega 3 fatty acids commonly used in pharmaceutical fish oil.
The process resembles something from a science fiction movie, with 8-foot-tall tubes of bubbling green liquid being fed from a large storage tank below.
The procedure begins with a line connected to the flue gas stack atop the plant. The flue gas containing the carbon dioxide is transferred to a shed on the ground and then pumped into a feed tank.
The mixture is fed into the 3.5-foot packing tubes with the algae at 160 gallons-per-minute, and the process of photosynthesis converts it into biomass and oxygen. When the biomass is harvested and dries, it hardens into dark-colored chips.
When the tubes turn dark green, usually about once a week, it is time to harvest. The algae consumes about half of the carbon dioxide in flue gas.
There is some maintenance and sampling required, but the system is self-contained and can be monitored from a researcher’s home in Lexington or a cellular phone.
In 2008, the Department for Energy Development and Independence tasked the University of Kentucky with developing technology to mitigate carbon dioxide emissions biologically. Jack Groppo, with the UK Center for Applied Energy Research, said it was a tall order because researchers were starting from scratch.
“There was some experimenting with growing algae to provide other chemicals, but nobody has done what we are doing on a large scale,” Groppo said. “We’ve had to develop a lot of the technology ourselves.”
More than 90 percent of Kentucky’s power comes from coal, which produces carbon dioxide as a waste product when burned.
The East Bend Station, near Rabbit Hash, was a candidate for the process because it removes or “scrubs” the sulfur from flue gas before it is emitted, which makes it compatible with algae. It also met the environmental requirements for the process, which include a reasonable amount of sunlight, a water source and moderate temperatures.