A group of Texas-based researchers provided answers for the nation's cattle feeding industry after it was given a very short window by the U.S. Environmental Protection Agency to begin reporting ammonia and hydrogen sulfide emissions.

EPA issued a final ruling on Dec. 18 that required the reporting of continuous air releases of these gases by large confined animal feeding operations to local and state emergency management entities.

Until this ruling, EPA had not required agricultural operations to report air emissions under the Comprehensive Environmental Response, Compensation & Liability Act of 1980 and Emergency Planning & Community Right-to-Know Act of 1986.

However, with the new EPA rule, it was determined that the reporting was required under the 1986 act, and operations falling within the guidelines must report emissions by Jan. 20, said Ben Weinheimer, Texas Cattle Feeders Assn. vice president.

The rule applies to operations that can emit 100 lb. or more of ammonia or hydrogen sulfide during any 24-hour period, Weinheimer said. These operations are now required to report the emissions to state and local emergency responders.

However, with the rule came no guidelines on how to gather that information or report it, and there were no officially adopted emission factors available, he said.

Weinheimer said the industry turned to researchers working on "Air Quality: Reducing Emissions from Cattle Feedlots & Dairies," a federally funded project headed by Dr. John Sweeten, director of the Texas AgriLife Research & Extension Center at Amarillo.

The project researchers, who had been gathering emissions data from area feedlots for the past six years, were pulled together to determine the best way for feedyard operators to estimate their emissions and develop a worksheet for calculating emissions, Sweeten said.

"The EPA rule basically gave these livestock operations one month to report ongoing emissions that exceeded the thresholds," Dr. Ken Casey, Texas AgriLife Research air quality engineer, said. "Needless to say, releasing the rule when they did, just before Christmas, without any advance notice and requiring reporting in the early new year, left the industry scrambling to get together a response as well as give responsible guidance to their members."

The writing team of Dr. Rick Todd and Dr. Andy Cole with the U.S. Department of Agriculture's Agricultural Research Service, Dr. David Parker with West Texas A&M University and Dr. Brent Auvermann with Texas AgriLife Extension, as well as others on their teams, worked to distill the collective ammonia results on short notice.

"We needed to convey to EPA that no single number is adequate to represent a basis for an emission factor, because emissions vary with what the cattle are fed, with the season and even with the time of day," Auvermann said. "We presented EPA and the cattle feeding industry with a range of emission factors that we believe would represent most feedyards in our area."

Research from this project has shown that emission rates for ammonia during winter months are about half of the emission rates during summer months, Todd said.

"Texas Panhandle feeding operations with more than 1,000 cattle could exceed the 100 lb.-per-day reporting requirement," Todd said, "but the negative environmental effects of ammonia that EPA is concerned about are most likely where ammonia mixes with urban air pollution or when ammonia is removed from the atmosphere in rain and over-fertilizes sensitive ecosystems."

He and Auvermann agreed that on the High Plains, ammonia is more of a regional than a local environmental concern.

"Ammonia does not stay in the atmosphere very long in its gaseous form," Auvermann said. "Unless it reacts with other gases to form fine particles, it's gone from the air within a few hours to a few days. We don't see much of the fine particles around here that would suggest otherwise."

Casey and Parker aggregated hydrogen sulfide field data for the reporting process. Their research shows that emission rates for hydrogen sulfide are lower during dry weather conditions and higher in wet conditions. On average, they are three times lower than ammonia concentrations -- approaching the minimum detection levels by sophisticated equipment.

"Hydrogen sulfide is not currently classified as a hazardous air pollutant by EPA; it is primarily of local and of minor regional concern," Casey said. "The regulation of hydrogen sulfide varies from state to state."

Concentrations measured at the center of a commercial Panhandle feedyard were substantially below the Texas regulatory threshold for the property boundary during the majority of the two-year monitoring period, he said. Also, concentrations at the boundary were considerably less than those measured at the center of the yard.

"What these researchers have found is that both ammonia and hydrogen sulfide represent exceedingly low concentrations over relatively large emitting surfaces and long time scales," Sweeten said. "The annual emission numbers can add up to the low threshold values of reporting that EPA just set, but they do not reach levels of general public concern."

Research Points

  • Ammonia emission rates during winter months are about half of summer rates.
  • Ammonia more a regional concern than a local one.
  • Hydrogen sulfide emissions lower during dry periods.
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