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Read: a story on the algal scrubber system in Agricultural Research.

From the Nation's Attic to the Nation's Farm

By Don Comis
July 21, 2000

An Agricultural Research Service microbiologist has gone to the nation's attic for inspiration in designing an algal scrubber system to clean waste from dairy barns.

ARS scientist Walter Mulbry redesigned and moved a device out of the darkness of the Smithsonian Institution's living coral reef exhibit into the daylight outside 300-cow dairy barns at a research center about 15 miles away in Beltsville, Md.

Mulbry teamed up with Walter Adey, director of the Marine Systems Laboratory at the Natural History Museum in Washington, D.C., to see if Adey's invention would clean dairy waste as well as it cleaned fish waste. He began with one of the scrubbers that Adey kept in a behind-the-coral-reef exhibit attic space. The scrubbers were algae-lined tanks that filtered water flowing out of, and back into, the coral reef aquaria on public view.

The scrubber did such a good job of removing nitrogen and phosphorus from liquid dairy manure in the lab, that Mulbry recently moved the experiment outdoors. Instead of the scrubber tank, Mulbry used a series of four parallel water troughs, or raceways, each 50 meters long by 1 meter wide. He lined these with plastic mesh for growing algae.

Mulbry dilutes the liquid manure from the dairy barns into tanks at the ends of each raceway, and the diluted manure is then pumped down the raceways in waves. The algae use the manure as fertilizer. Each week, the algae will be harvested by rolling up the mesh mats. The algae will then be dried for testing as a high-protein feed supplement for cattle on the farm and as an aquaculture feed.

The algae will also be tested as a green manure fertilizer to grow corn, soybeans and wheat. Possible commercial uses in the future include high-value chemicals made from the algae.

A brief story on the algal scrubber system appears in the July issue of Agricultural Research.

ARS is the chief scientific agency in the U.S. Department of Agriculture.

Scientific contact: Walter Mulbry, ARS Soil Microbial Systems Laboratory, Beltsville, Md., phone (301) 504-6417, fax (301) 504-7976,