A Study on the Air Flow and Odor Emission Rate from a Simplified Open Manure Storage Tank

AN ABSTRACT. This study presents a numerical evaluation of air flow and odor emission rate from an open manure storage tank. Odor emission rate is needed to facilitate the odor dispersion study and to compare different odor sources in terms of odor emission. The concentration at the manure surface, the tank dimensions, and wind speed were used to calculate air flow and the emission rate. The SIMPLER algorithm developed by Patankar (1980) and a two-layer turbulence model were used in the numerical simulation with a grid of 152 x 139. The predicted emission rate agreed with the field measurement results found in the literature. Experimental verification of the air flow showed that the flow pattern and velocity profile prediction were also in agreement with the experimental results. The calculated odor-emission rate was a function of the manure surface area, the odor concentration at the manure surface, the tank dimensions, and the wind speed. Keywords. Odor emission rate. Manure storage tank. Livestock, Numerical simulation. O dor is one of the major environmental concerns for the livestock industry. Complaints and lawsuits are filed because of odors generated from livestock facilities. Liquid manure storage is a major source of complaints and lawsuits. A number of studies were carried out to study odor dispersion and the area downwind that may be affected by a given odor source under given weather conditions. However, as shown by Li et al. (1994), dispersion studies are hindered due to lack of adequate methods to estimate the odor emission rate from a manure storage facility. The odor emission rate is the source term in the dispersion study. An accurate odor emission calculation is also needed to compare different storage facilities in terms of odor emission and to compare odor emission from the building with the manure storage. Odor emission from a production facility can be estimated by knowing the exhaust-air flow rate and odor concentration in the exhaust air. For a manure storage facility, the problem is more complicated because the air exchange rate is difficult to obtain. Carney and Dodd (1989) calculated the emission rate from manure storage or treatment facility by multiplying the odor concentration at the source by the surface area of the source and by the prevailing wind speed. Bode (1991) studied odor and ammonia emission by covering tanks. Li et al. (1994) backcalculated the odor emission rate from field measurements of an odor plume width and odor intensity downwind by

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