Temporal Variations in Greenhouse Gas Emissions from Dairy Cow Manure

Greenhouse and regulated gas emissions degrade air quality and contribute to environmental problems including acid rain and climate change. Gas emissions from animal feeding operations are of increasing concern as urban expansion encroaches on rural farming areas as well as due to increasing awareness of climate change. 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. The types of gases generated and their emission rates are dependent on several variables, generally including animal species, feeding diets, and physical controls on gas emissions (i.e., temperature, manure’s water content and aeration). Focusing on the physical controls on gas emissions, we have designed and setup an experiment in a research greenhouse to investigate the impact of temperature and manure water content on gas emission rates. Our research initially aims to characterize individual gas emission rates from manure as a function of temperature, manure water content and time after excretion. The gas emission fluxes are determined with a closed-chamber method employing an automated LI-8100 chamber (LI-COR Biosciences, Lincoln, Neb.) and the gas concentrations are monitored with a Fourier Transform Infrared (FTIR) spectroscopy Gasmet DX-4030 analyzer (Gasmet Technology Oy, Helsinki, Finland). Evaporation rates, changes in manure water content, and temperature are also monitored during the experiment to define the degree of temporal variability affected by these factors. In our presentation, we will discuss the experimental design and setup, challenges, and results as well as potential application of the information gathered that will facilitate more simple and accurate estimation of gas emissions from animal feeding operations