ARS | Publication request: Standardization of flux chamber and wind tunnel flux measurements for quantifying emissions from area sources at animal feeding operations

Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: June 28, 2011
Publication Date: August 7, 2011
Citation: Parker, D.B., Ham, J., Woodbury, B.L., Cai, L., Spiehs, M.J., Rhoades, M., Trabue, S.L., Todd, R.W., Cole, N.A. 2011. Standardization of flux chamber and wind tunnel flux measurements for quantifying emissions from area sources at animal feeding operations. In: Proceeding of the American Society of Agricultural and Biological Engineers (ASABE) Annual International Meeting, August 7-10, 2011, Louisville, Kentucky. Paper No. 1111166.

Interpretive Summary: Environmental regulations enforced by the USEPA now require the reporting of air emissions from animal feeding operations. Portable wind tunnels and flux chambers are one method used to quantify air emissions from large area sources such as pens and lagoons. The flux chamber or wind tunnel is placed over the emitting surface, clean air is passed through the chamber, and the amounts of air emissions are measured. There have been dozens of different designs of flux chambers and wind tunnels. One problem with chamber-type measurements is that the emission rate changes depending on the air flow rate passed through the chamber, leading to highly variable and potentially inaccurate emission estimates. Because of this variability, there is a need to standardize flux chamber and wind tunnel measurements so that results can be compared on an ‘apples to apples’ basis. In this paper, we present a simple methodology for standardization and comparison of different chamber types by measuring water evaporation within the chamber. By comparing evaporation rates within the chamber and in the field, correction factors can be developed for other compounds like ammonia and odorous volatile organic compounds. The net result will be the development of more accurate emission estimates at animal feeding operations.

Technical Abstract: A variety of wind tunnels and flux chambers have been used to measure fluxes of volatile organic compounds (VOC) and ammonia (NH3) at animal feeding operations (AFO). However, there has been little regard to the extreme variation and inaccuracy caused by inappropriate air velocity or sweep air flow rates. There is a need to standardize flux chamber and wind tunnel measurements. In this paper, we present results of evaporative and VOC flux measurements with the EPA flux chamber and a small wind tunnel. Emissions of gas-film controlled compounds NH3 and VOC commonly found at AFO are positively correlated with evaporation rates. We propose a simple methodology for standardization and comparison of different chamber types by measuring water evaporation using a mass balance approach. This same methodology holds promise for correcting field-measured chamber flux measurements resulting in more accurate emission estimates.