Use of residence time distribution for evaluation of gaseous pollutant volatilization from stored swine manure

Abstract

A quantification analysis for evaluation of gaseous pollutant volatilization as a result of mass transfer from stored swine manure is presented from the viewpoint of residence time distribution. The method is based on evaluating the moments of concentration vs. time curves of both air and gaseous pollutants. The concept of moments of concentration histories is applicable to characterize the dispersal of the supplied air or gaseous pollutant in a ventilated system. The mean age or residence time of airflow can be calculated from an inverse system state matrix B]‐1 of a linear dynamic equation describing the dynamics of gaseous pollutant in a ventilated airspace. The sum elements in an arbitrary row i in matrix B]‐1 is equal to the mean age of airflow in airspace i. The mean age of gaseous pollutant in airspace i can be obtained from the area under the concentration profile divided by the equilibrium concentration reading in that space caused by gaseous pollutant sources. Matrix B]‐1 can also be represented in terms of the inverse local airflow rate matrix (W]‐1), transition probability matrix (P]), and air volume matrix (V]) as, B]‐1 =W]‐1P]V]. Finally the mean age of airflow in a ventilated airspace can be interpreted by the physical characteristics of matrices W] and P]. The practical use of the concepts is also applied in a typical pig unit.