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United States Department of Agriculture

Agricultural Research Service


Glickman Says Research May Help Curb Manure Odor

By Ben Hardin
December 14, 1998

WASHINGTON, Dec. 14–Unpleasant odor from animal feedlots may be reduced as U.S. Department of Agriculture scientists learn more about how to “harvest” manure’s ammonia and re-use it as a valuable fertilizer, Agriculture Secretary Dan Glickman announced today.

“Odors from livestock manure have been a long standing challenge for scientists,” Glickman said. “USDA researchers are working on a solution to the odor issue that could also turn the smell of waste into valuable nitrogen fertilizer.”

As manure from cattle or swine decays, the released ammonia contributes to its pungent odor. Researchers are testing chemicals, one of which looks promising, that keep manure from rapidly decomposing and releasing its ammonia. An estimated half to three-fourths of the nitrogen in manure from beef cattle feedlots breaks down to ammonia gas and other compounds before it ever reaches farm fields.

Glickman’s announcement coincides with a listening session on the National Strategy for Animal Feeding Operations being held today in Denver, Colo. Today’s session is one of 11 held around the country to seek public comment on the joint USDA-Environmental Protection Agency draft strategy.

The unified national strategy, part of the Clinton Administration’s Clean Water Action Plan, seeks to minimize threats to water quality and public health caused by animal feeding operations, while ensuring the long-term sustainability of livestock production in the United States.

According to ARS microbiologist Vincent H. Varel, testing has focused on NBPT, a chemical that was recently commercialized as a nitrogen preservative for use in no-till, soil-saving farming. NBPT is one of a number of compounds known as urease inhibitors.

“Urease is an enzyme that converts the urea in urine into ammonia that escapes into the air,” said Varel, who has been conducting studies on several urease inhibitors at the Roman L. Hruska U.S. Meat Animal Research Center at Clay Center, Neb. “In preliminary experiments, NBPT worked even better in the feedlot than in the laboratory. That is promising.”

While urease inhibitors will reduce ammonia emissions, Varel cautioned that other odor-reducing compounds will be needed to more fully control the variety of unpleasant-smelling, volatile compounds from manure.

He and his colleagues envision encapsulating mixtures of odor reducers in starch or other protective materials. Encapsulation would ensure slow release of active compounds and require fewer applications to cattle feedlots, manure slurry tanks and covered lagoons used on livestock farms.

Scientific contact: Vincent H. Varel, ARS Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, Neb., phone (402) 762-4207, fax (402) 762-4209,

Last Modified: 5/15/2017
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