Dr. Ken Casey, Texas A&M AgriLife Research air quality engineer in Amarillo, collects a greenhouse gas sample from a static flux chamber. (Texas A&M AgriLife photo by Kay Ledbetter)
Dr. Ken Casey, Texas A&M AgriLife Research air quality engineer in Amarillo, collects a greenhouse gas sample from a static flux chamber.

Feedyard greenhouse gas study analyzes emissions, mitigation factors

Research also relevant to manure quality as more is learned about nutrient transformations and water losses from feedyard surface.

A week spent in a feedyard pen is helping researchers gain a better understanding of greenhouse gas emissions. Texas A&M AgriLife Research and the U.S. Department of Agriculture's Agricultural Research Service (ARS) are collaborating to analyze nitrous oxide and methane emissions from a feedyard pen in Texas.

AgriLife Research air quality engineer Dr. Ken Casey and ARS livestock nutrient management researchers Drs. David Parker and Heidi Waldrip spent the better part of a week sitting inside a feedyard pen that had just been vacated by cattle. Their goal is to improve the national inventory of greenhouse gases and determine potential mitigation measures. The project is funded by ARS and AgriLife Research, with instrumentation used in the study partly supported by the Texas Cattle Feeders Assn.

Using six automated chambers, more than 575 automated flux measurements and 60 manual flux measurements were taken from separate static chambers to help monitor nitrous oxide and methane gas emissions, AgriLife Research said. Halfway through the experiment, a half-inch of water was applied to the pen surface within the measurement chamber bases to simulate a rainfall event.

“We’re looking to understand better what controls nitrous oxide and methane coming off feedlot pen surfaces,” Casey said. “We’re interested in the emissions of these gases because of their contribution to climate change. We want to improve the national emissions inventories as they pertain to greenhouse gases from feedyards in the Texas High Plains.

“Second, we are also very interested in obtaining a better mechanistic understanding of the evolution of these gases from the pen surfaces," he continued. "What controls the release of these gases? If we are able to gain a better understanding of that, then we will potentially be able to provide advice to the industry about mitigation practices when it comes to pen management.”

Casey said the testing demonstrated that areas of the pen with shallower manure packs on the surface primarily emitted nitrous oxide, while two chambers sitting over deeper manure where the pen drain was located emitted almost no nitrous oxide but did emit methane.

“We are trying to understand the interplay of those two gases, because the processes that are producing them are related,” he said.

The different factors that influence the creation and release of the gases include temperature, moisture content and the amount of manure on the pen surface, Casey said.

“By understanding how those factors play together in the production of those gases, we can develop a greater understanding and potentially develop mitigation strategies,” he said. “However, it’s complicated, because a strategy that reduces one emission may, in fact, increase the other. So, our understanding of the production of these gases and the environmental factors that influence them are important.”

During the study, gas samples were collected twice a day from the static chambers and then taken to Casey’s air quality lab to be analyzed on a gas chromatograph. Six automated chambers took measurements each hour around the clock. The automated chambers were linked through a multiplexer to automated nitrous oxide and methane analyzers.

“We know emissions are influenced by temperature, and by taking diurnal measurements, we can understand the variability throughout the day and night, as well as that of the effects of moisture,” Casey added.

The week of measurements is only part of ongoing research being conducted by Casey and Parker. Casey said the results will be reported to the industry, as well as in various journals along the way, and will be used for extended air quality research.

Parker noted that their research is also relevant to manure quality. “Not only is this research important for greenhouse gas emissions, but through this and ongoing laboratory studies, we are learning more about nutrient transformations and water losses from the feedyard surface,” he said.

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