Monitoring Temporal Variations In Greenhouse and Regulated Gas Emissions From Cow Manure In Relation to Moisture Content and Temperature.

Animal feeding operations (AFOs) are a significant source of greenhouse and regulated gas emissions. Moisture content and temperature are two primary regulators of gas emissions. In our study, we investigated and analyzed the trends and temporal variations of major greenhouse and regulated gas (CO₂, CH₄, N₂O, and NH₃) emissions from cow manure. Focusing on diurnal and weekly variations, our study initially aimed to characterize individual gas emission rates from manure corresponding to fluctuations in moisture content and temperature, and time after excretion. Our goal was to monitor emissions during the drying process, including the impact of diurnal temperature variation and significant change of moisture content on the weekly time-scale due to evaporation. The experiment was setup in a greenhouse to maintain typical summer-time temperatures. The gas emission fluxes were determined with a closed chamber method employing an automated chamber (LI-8100; LI-COR Biosciences, Lincoln, NE). The gas concentrations were monitored with a FTIR (Fourier Transform Infrared) spectroscopy analyzer (Gasmet DX-4030; Gasmet Technology Oy, Helsinki, Finland) and a CO₂ analyzer (LI-8100A; LI-COR Biosciences, Lincoln, NE) for comparison. The CO₂ emission fluxes determined with both analyzers were in excellent agreement. In addition to measuring gas emissions, evaporation rates, changes in manure moisture content, and temperatures were closely monitored throughout the course of the experiment to define the degree of temporal variability. In this presentation, we will demonstrate a strong correlation between gas emission fluxes and temperature and moisture content on diurnal and two-week time-scales. The measurements of gas buildup in chambers and the resulting estimates of flux provide important information on greenhouse and regulated gas emission rates and contribution to greenhouse gas buildup.