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Researcher ‘sniffing out’ emissions from cattle feedyards


March 12, 2008
By Kay Ledbetter

Topics

A researcher with Texas A&M
University’s Agricultural Experiment Station believes locating an air
quality trailer in the midst of cattle pens at a feedlot will help
measure gaseous emissions.

research 1
 A Texas Agricultural Experiment Station climate-controlled instrument trailer is parked among the feeding pens at a Texas Panhandle feedyard to monitor emissions of ammonia and hydrogen sulfide.

A researcher with Texas A&M University’s Agricultural Experiment Station believes locating an air quality trailer in the midst of cattle pens at a feedlot will help measure gaseous emissions. Dr. Ken Casey, an air quality engineer with the experiment station in Amarillo, Texas, wants to measure ammonia and hydrogen sulfide emissions from feedyards.

His research team set up two climate controlled instrument trailers in different locations at a Texas feedyard. The trailers are equipped with two continuous emissions analyzers – one for ammonia, the other for hydrogen sulfide.

Samples from above the trailer are drawn into a heated manifold inside the trailer, where the analyzers draw their sample, Dr. Casey explains. This instrumentation allows measurement of both ammonia and hydrogen sulfide with a high degree of precision.

Ammonia emitted at feedyards comes from excess nitrogen fed to cattle and excreted primarily in the urine, Dr. Casey says. His research is aimed at determining when conditions are most favorable for emissions to occur. With this knowledge, feedyard operators can then better target their mitigation strategies.

research 2
Dr. Ken Casey, an air quality engineer with the Texas Agricultural Experiment Station, shows how the sample collected in the trailer is drawn into two continuous emissions analyzers.   

Photos By Kay Ledbetter. Texas Agricultural Experiment Station.

Ammonia is considered an environmental pollutant associated with a number of undesirable issues that are both regional and extensive in nature, Dr. Casey explains, adding that two federal acts – the Comprehensive Environmental Response, Compensation and Liability Act and Emergency Planning and Community Right-to-Know Act – establish reportable levels of ammonia, hydrogen sulfide and other emissions.

In recent years, the courts have applied this legislation to swine and poultry operations, which has resulted in a heightened awareness of environmental concerns within the agriculture community, he says, although he adds, to date, these acts have not been applied to cattle feedyards.

Dr. Casey says that by combining the measurement data with meteorological data collected by other researchers at the same yard and an air pollution model allows the total emission rate to be determined.

“Because we’re going to monitor this over the course of a year, we’ll pick up daily and seasonal trends,” he explains. “We’ll be able to correlate the rate with feedyard and climatic conditions, such as pen moisture content, days since rainfall, temperature and solar radiation.”

By better understanding the mechanisms that influence these emissions, researchers can establish strategies that may be useful in controlling them, Dr. Casey says.

“Clearly, addressing the problem at its source through waste minimization potentially has the greatest effect,” he says. “That means not feeding a level of nutrients to cattle in excess of what they need.”

research 3
Dr. Ken Casey, an air quality engineer with the Texas Agricultural Experiment Station, checks the heat manifold from which samples are continuously drawn.

Dr. Casey will also be measuring hydrogen sulfide, which can also
impact human health, particularly at high concentrations. Even though
he is monitoring and measuring for hydrogen sulfide, he reassures that concentrations are usually very low around feedyards.

“There is concern that even relatively low concentrations of hydrogen sulfide can have health effects as well,” Dr. Casey says. “There is legislation in a number of states, including Texas, of threshold exposure limits for hydrogen sulfide in the community around sources of emission.”

Within a feedyard, most of the hydrogen sulfide emissions are thought
to come from the runoff retention structures or lagoons, he says. Yard emissions are already being measured. The next step is to float a wind tunnel on the surface of the lagoon to measure emissions.

Additional measurements of the ambient concentration downwind of the runoff retention structure also will be taken, allowing an emission rate to be obtained through modeling.

“So, in effect, we get two goes at measuring the emission rate – directly and indirectly,” Dr. Casey says. “This will give us more confidence in the emission rates we have for these facilities.”

Kay Ledbetter is a writer with Texas A&M University’s News and Public Affairs Department. 


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