Growing Algae on Dairy ManureBy
Can dairy farms become algae farms? All that manure might grow a lot of
algae, according to Walter W. Mulbry, an Agricultural
Research Service microbiologist in Beltsville, Md. Mulbry recently began
the first lab test to see how well algae remove nitrogen and phosphorus from
manure, to keep these nutrients out of streams. He is using treated manure from
the ARS Beltsville Agricultural Research
Center's 300-cow dairy barns.
In Mulbry's vision, a dairy farm could grow algae year-round on a diet of
manure. The algae would grow on mesh mats lining a series of parallel,
shallow raceways about 100 yards long. Treated manure would be mixed with water
and pumped into the first raceway, flowing down its length. Then it would be
pumped into the second raceway, and so on.
Each time the algae grew about an inch, the mats would be mechanically
rolled up to harvest the algae. Dried algae could be made into high-protein
feed for livestock and fish. Other possible products: fertilizer and high-value
Walter Adey, director of the Smithsonian
Systems Laboratory at the Museum of
Natural History in Washington, D.C., invented the technique in the 1970's to
clean water in the Museum's coral reef exhibit, using fish waste to grow algae.
The Smithsonian patented it in 1982.
The technology is now in commercial use in aquaculture and in two wastewater
treatment plants. Adey loaned Mulbry a miniature prototype like the one on
display at the coral reef exhibit--more a basin than a raceway, measuring 3 feet
by 3 feet. Mulbry expects to know in about a month if the system works as well
with dairy manure as it does with fish waste and municipal wastewater.
If it does, he proposes building a test raceway outside the center's dairy
Scientific Contacts: Walter W. Mulbry,
Soil Microbial Systems
Laboratory, Beltsville, Maryland, phone (301) 504-6417, fax (301) 504-7976,