Process to Use Shrimp, Tilapia to Extract Algae Oil for Biofuel

Using algae, brine shrimp, and tilapia, researchers have designed a novel system that extracts oil for use as biofuel, potentially reducing greenhouse gas (GHG) emissions in a proposed electric power plant.

Microalgal biomass production offers the potential to reduce GHG emissions by providing biofuel replacement of fossil fuels as well as carbon-neutral animal feeds, said David Brune, bioprocessing engineering professor at the University of Missouri.

“Algae have been shown to produce 100 times more fuel than soybean oil, but they are hard to extract and convert into usable fuel,” he explained.

Brune and colleagues developed a biomass cultivation model for a proposed 50-megawatt natural-gas-fired power plant in Southern California. In the researchers’ design, sludge-fed algae would be cultivated in large raceways. Paddle wheels would hasten reproduction by moving the water. This is where the brine shrimp and tilapia come in. “The brine shrimp eat the algae and convert it into a consistent, high-quality protein and oil,” Brune said. Tilapia consume the algae to prevent overproduction, reduce zooplankton and clean up algal waste to provide clean water.

The shrimp are harvested and separated into high-protein feeds and oils. The shrimp waste is collected and fermented in an anaerobic digester.

“If 100 percent of the algal biomass consumed by the shrimp were harvested and fermented, the resulting biomass production could replace 26 percent of the plant’s natural gas usage,” Brune said.

Another advantage of the system is that carbon dioxide generated by the plant can be fed to the algae.

The research appears in the November 2009 issue of the ASCE Journal of Environmental Engineering.

Earlier research by Brune and others at Clemson University using actual raceways and fermenters showed that brine shrimp feeding on algae could produce up to 500 gallons of biodiesel per acre per year with little environmental waste.

“I originally started my focus on oils for food,” Brune said. “But the government’s interest and the push for alternative fuels changed the direction of our research.”

Microalgal biomass production offers several advantages over conventional biomass production, he said. In addition to higher productivity, this method can use otherwise nonproductive land, reuse and recover waste nutrients, and use saline or brackish waters.

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