Using algae to lock away greenhouse gas

Oct 03, 2013 by Keith Hautala, Whitney Hale & Alicia Gregory

The University of Kentucky Center for Applied Energy Research is developing green technology to capture carbon dioxide emissions from coal-fired power plants, using algae.

Four years ago, CAER and UK's Biosystems and Agricultural Engineering Department set out to demonstrate that an algae-based system could recycle the carbon dioxide in . Now, with $1.8 million in funding from the Kentucky Energy and Environment Cabinet, CAER is partnering with Duke Energy to test a pilot-scale algae system at East Bend Station in Northern Kentucky.

Scientists looking for ways to curb have taken a keen interest in algae. These simple, plantlike, aquatic organisms—their family includes both pond scum and seaweed—are among the oldest forms of life on Earth. Like plants, they draw from photosynthesis, using light from the sun and carbon dioxide from the air.

More than 90 percent of Kentucky's power comes from , which when burned produces carbon dioxide as a waste product. With federally mandated carbon emissions limits on the horizon, the work underway at CAER is more critical than ever. Algae does an efficient job of sequestering carbon, taking it out of the air and locking it away in solid biomass. That biomass could, in turn, find use as a raw material for making products or as a renewable fuel itself.

"The industry will adapt technology, which right now doesn't exist. So that's our challenge," said Jack Groppo, CAER's principal research engineer for environmental and coal technologies. "The nice thing about algae is that it actually does capture and sequester the carbon dioxide."

Instead of acres of ponds, CAER's strategy is based on a closed system of photobioreactors to grow algae. CAER's system, made of plastic tubes and off-the-shelf PVC pipes, is built by UK students and staff and glued together on-site. Expanding the system simply means adding more tubes. The closed system is more efficient, even in winter when sunlight is minimal. It is less prone to contamination, and evaporation is much less of a problem than with ponds.

"We are harnessing algae's ability to grow very fast and perform photosynthesis in order to take the carbon dioxide in flue gas and turn it into biomass," said Michael Wilson, CAER engineer.

CAER has installed a 5,000-gallon feed tank with two centrifugal pumps on the east side of the power plant, with southern exposure to maximize the sunlight on the tubes. The feed tank serves as the hub, where carbon dioxide and nutrients are added, and where water returns. Algae comes out of the photobioreactors and it goes into the harvest tank, where it settles to the bottom.

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The algae that comes out is dark green and the consistency of pesto. That material can be fed into an anaerobic digester to produce methane gas that the power plant can burn for fuel. It can be dried and processed into fish food or animal feed. Or it can undergo different processing to be turned into biodiesel, or even .

"We have to work in the realm of feasible economics," Groppo said. "From a biofuels processing point of view, it makes sense. It is not extremely profitable, but when you look at what's happened, you have actually captured from a dilute stream and turned it into a value-added product."

If, in the future, CAER got the funding to install 100 acres of algae tubes to take coal flue gas and make jet fuel, what would that look like? That task was given to UK College of Design students.

Architecture students and faculty understood the needs of this type of technology having designed theoretical proposals for algae systems before. However, Duke Energy's support of CAER's concept gave them an opportunity to develop a potential real-world solution.

"It's a great opportunity to work with these students because their creativity is unlimited," Groppo said. "They are enthusiastic, they have great ideas, and they are just not confined by anything, which is refreshing. You can see the raw enthusiasm when we open up the greenhouse doors, and when they look at those same tubes, they are just overwhelmed, and the questions just begin flowing."

Under the direction of Assistant Professor Anne Filson, last spring UK students were charged with imagining the future by designing an algae research facility and conference center within a 100 acre demonstration bioreactor on the East Bend Station property. CAER wanted to see what fresh eyes could bring to the project.

The CAER's team introduced students to the fundamental principles of algae growth, bioreactor design, and serviceability, which gave each student a functional foundation to explore architectural innovation.

"My students are looking at it as this really amazing surreal landscape that must be experienced," Filson said. "All of them are looking at ways to choreograph the movement through the algae bioreactors, what is it like to approach it, to drive through it, to get out of your car and walk up to a research lab within it, and how does this landscape inspire people to think about energy in a new way."

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An algae bioreactor and research facility on the site of a massive coal power plant is a project without precedent, making it a powerful student problem.

"It really creates the perfect architecture project, where there is a big landscape of hundreds of acres of algae bioreactor tubes, with ancillary buildings that would house laboratories for researchers, processing facilities to process the into useful mediums like biofuels and jet fuel, and it also presented a fascinating challenge to provide accommodations for the vehicles, materials, and people that would be moving on and off the site," Filson said.

The CAER project served the College of Design's mission to provide students with the opportunity to apply rigorous design research and architectural thinking to address the unique environmental issues facing Kentucky. Additionally, the project simulated real world professional conditions, by offering students opportunities to engage CAER's experts and Duke Energy's client team to assist in the development of ambitious and innovative architectural proposals for East Bend.

"It's been a great education from a sustainability standpoint," Filson said. "We're learning and talking every day about how do we transition from a coal economy and coal energy to alternative fuels…slowly, steadily, and how do we participate in that transition."

But as students look for answers to the questions surrounding the alternative energy technology, they haven't forgotten the value of design.

"You're talking to engineers. They are more concerned about whether it is going to work or not," said architecture senior Robert Pekrul, of Lexington. "Taking that functionality and adding an artistic value to it, is what we are really trying to do here. Because that's what we do, we design."

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