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Abstract
The major source of emissions in animal production sites is from animal waste (manure), which can be in solid, slurry, or liquid states, exhibiting varying physical properties. Once manure is excreted from an animal, processes of biological decomposition and formation of gaseous compounds continue, but diminish as the manure cools and dries. However, increases in gas emissions following rewetting, particularly from precipitation, have been observed in various agricultural lands. Our study investigates changes of gaseous emissions through manure drying and rewetting processes to identify the effects of climatic conditions and manure management on gaseous emissions. We carried out drying and rewetting processes of dairy manure in a greenhouse to maintain moderate wintertime temperatures (20 – 40 C) while monitoring gaseous emissions through these processes. Closed dynamic chambers (CDC) coupled with a multiplexed Fourier Transformed Infrared (FTIR) spectroscopy gas analyzer provided gas flux estimates. The analyzer was capable of monitoring 15 pre-programmed gases simultaneously including typical gaseous compounds and greenhouse gases emitted from manure sources; namely, ammonia, carbon dioxide, methane, nitrous oxide, oxides of nitrogen, and volatile organic compounds. Magnitude of dairy manure gas emissions resulting from variations in moisture and temperature provide insight toward enhancing manure management decisions. Results from our study should further understanding of manure gas emission temporal dynamics that are largely dictated by heat and by drying and rewetting processes that impact the generation and delivery of gasses to the atmosphere. Our overall goal is to advance development of appropriate best management practices to reduce gas emissions for dairy operations in semi-arid regions.
Purpose
The objective of this project is to identify the effects of climatic conditions and manure management on gaseous emissions. The results from our study will be used to advance development of appropriate best management practices to reduce gas emissions for dairy operations in semi-arid regions.
Fig 1. Gas emissions from two dairy manure samples were monitored in a greenhouse to compare the magnitude of gas fluxes through manure drying and rewetting processes. |
What Did We Do?
We investigated changes in gaseous emissions by carrying out drying and rewetting processes of dairy manure in a greenhouse to maintain moderate summertime temperatures (20 – 40 oC) while monitoring gaseous emissions. Closed dynamic chambers (CDC) coupled with a multiplexed Fourier Transformed Infrared (FTIR) spectroscopy gas analyzer provided gas flux estimates. The analyzer was capable of monitoring 15 pre-programmed gases simultaneously including typical gaseous compounds and greenhouse gases emitted from manure sources; namely, ammonia, carbon dioxide, methane, nitrous oxide, oxides of nitrogen, and volatile organic compounds. Gas emissions from two dairy manure samples were monitored to compare the magnitude of gas fluxes during 14 days of manure drying and rewetting processes.
Fig 2. Gas emissions were determined using the closed dynamic chambers integrated with a multiplexed Fourier Transformed Infrared (FTIR) spectroscopy gas analyzer. |
What Have We Learned?
An increase in surface water content occurring after a rewetting event (e.g., simulated 5 mm of rain) represents an abrupt increase in manure moisture content, which can promote microbial activity and a commensurate increase in gas emissions from manure. In our study, we found gas fluxes were actually suppressed during and shortly after the rewetting process, mainly due to reduction in air-filled pore space causing reduced gas diffusivity in the manure crust layer. As the wet layer dried, gas emissions eventually increased to levels prior to wetting.
Future Plans
Future experiments include: (1) simulation of manure drying-rewetting with various amount of water and rewetting times, (2) considering the immediate response time and effective period of the pulse response of the gas fluxes after rewetting which might have been missed in our study, (3) Further
Fig 3. Manure sample after the rewetting process. |
investigation of the effect of the crust layer on water and gas transport from and into manure.
Authors
Pakorn Sutitarnnontr, Graduate Student, Dept. of Plants, Soils, and Climate, Utah State University, pakorn@aggiemail.usu.edu
Enzhu Hu, Dept. of Plants, Soils, and Climate, Utah State University
Rhonda Miller, School of Applied Sciences, Technology, and Education, Utah State University
Markus Tuller, Dept. of Soil, Water, and Environmental Science, University of Arizona
Scott B. Jones, Dept. of Plants, Soils, and Climate, Utah State University
Additional Information
Contact Information: Pakorn Sutitarnnontr, Environmental Soil Physics Laboratory, Dept. of Plants, Soils, and Climate, Utah State University. Email: pakorn@aggiemail.usu.edu
Acknowledgements
The authors gratefully acknowledge support from the USDA-NIFA under the AFRI Air Quality Program (Grant # 2010-85112-50524) and the Western Sustainable Agriculture Research and Education Program (Grant # GW13-006).
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