Oct 26, 2007

Pond Scum May Have Bright Future

University of Georgia researchers are aspiring to give pond scum an image makeover.

Along with a shuttle bus running off chicken fat biodiesel and a tractor using soybean biodiesel, UGA researchers at the Sunbelt Expo last week demonstrated that algae isn’t the scum of the earth. It might just prove to a viable source of biofuels, while at the same time providing Georgia a solution for wastewater woes.

UGA has been experimenting with the manufacture of fuel from biomass — trees, grasses, poultry waste, industrial and agricultural waste. The university has been researching algae’s fuel potential for about a year, said K.C. Das, coordinator of the UGA Biorefining and Carbon Cycling Program, but the concept isn’t new. The Department of Energy primarily in the 1980s and 1990s invested hundreds of millions of dollars in algae research but stopped because at the time oil prices were affordable. Today, he said, oil is selling for more than $85 a barrel.

“Now globally, there’s interest,” he said.
Algae can be both marine and freshwater. There are even some saltwater varieties that can grow in freshwater, he said. On average, algae produces 12 to 15 dry tons per acre at an average of 25 to 30 percent oil that can be used as biodiesel. Some algae produces even more oil.

The most robust systems are those based on the native flora in the area of cultivation, he said. Das and his team also are combining species in an attempt to find mixed cultures which grow best together.

Algae is particularly interesting, because it is a source for biodiesel and that process’ biproducts can be made into both ethanol and methane, Das said. After lipid extraction, the remaining sugars and other carbohydrates can be fermented to produce ethanol or anaerobically digested to produce methane.

“Anaerobic digestion is commonplace. The ethanol part, we still have a little devilment to go through, but it’s very feasible,” he said.

An intriguing partner of algae in fuel generation is wastewater. Algae aids in the processing of wastewater into clean effluent while a wastewater treatment plant provides a good environment for algae to thrive.

“We do need to couple it with something else to make the benefit of the technology maximized. If we just try to do it without the treatment aspect of it, then we don’t get the full benefit,” Das said. “...Get two problems solved at the same time. The wastewater has phosphorus and nutrients. What is missing in the wastewater you can add.”

Most wastewater treatments plants are designed to remove carbon. Algae consumes carbon dioxide and then releases oxygen and produces biomass, he said. The carbon required for algae is coming from BOD (biochemical oxygen demand) removal from the wastewater. 
Algae can assist in “polishing” the wastewater of the pollutant phosphorous, Das said. Phosphorous is problematic to many municipalities and its discharge into waterways is limited by the Georgia Environmental Protection Division.

To make algae grow even faster, carbon dioxide can be added from any combustion source, a power plant perhaps, he said.