ARS | Publication request: Effect of wind tunnel air velocity on VOC flux rates from CAFO manure and wastewater

Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Proceedings
Publication Acceptance Date: June 1, 2008
Publication Date: June 29, 2008
Repository URL: http://asae.frymulti.com/azdez.asp?search=1&JID=5&AID=25026&CID=prov2008&v=&i=&T=1
Citation: Parker, D., Caraway, E., Rhoades, M., Donnell, C., Spears, J., Cole, N.A., Todd, R.W., Casey, K.D. Effect of wind tunnel air velocity on VOC flux rates from CAFO manure and wastewater. In: Proceedings of 2008 Annual International Meeting of the American Society of Agricultural and BIological Engineers International, June 29-July 2, 2008, Providence, Rhode Island. Meeting Presentation Paper Number 083897.

Interpretive Summary: Volatile organic compounds (VOC) emissions from livestock feeding operations are a major cause of odor. In research studies of VOC emissions wind tunnels or flux chambers are often used to estimate VOC emissions from animal feeding operations (AFO). However, in many of these experiments the air velocity or sweep air flow rates through the chamber are not measured or evaluated. In this study, laboratory experiments were conducted to evaluate the effect of wind tunnel air velocity on VOC emission rates from different sources (standard solutions of VOC in water, cattle manure, and wastewater from beef cattle and dairy AFO) at wind tunnel air velocities that ranged from 0.003 and 0.2 m/s. These corresponded to volumetric air exchange rates of 0.6 to 39 exchanges per minute. VOC in outlet air were measured using thermal desorption and gas chromatography/mass spectrometry. VOC emission rates increased linearly with increasing wind velocity. These results show that wind velocity is a major factor affecting VOC emissions from AFO. Thus proper selection of representative air velocity or sweep air flow rate is critical when estimating VOC emissions using wind tunnels and flux chambers. Use of low sweep air velocities, as is often seen in flux chamber experiments, will result in great underestimates of true VOC emissions.

Technical Abstract: Wind tunnels and flux chambers are often used to estimate volatile organic compound (VOC) emissions from animal feeding operations (AFOs) without regard to air velocity or sweep air flow rates. Laboratory experiments were conducted to evaluate the effect of wind tunnel air velocity on VOC emission rates. VOC emissions were measured on standard solutions of VOCs in water, and on manure and wastewater from beef cattle and dairy AFOs at wind tunnel air velocities between 0.003 and 0.2 m/s corresponding to volumetric air exchange rates of 0.6 to 39 exchanges per minute. Activated carbon-filtered air was passed through a small rectangular wind tunnel (30.5 cm length, 15.2 cm width, 5.1 cm height). Outlet air was sampled using stainless steel sorbent tubes (Tenax TA) and analyzed for seven volatile fatty acids (acetic, propionic, isobutyric, butyric, isovaleric, valeric, hexanoic) and four heavier molecular weight (MW) semi-VOCs (phenol, p-cresol, indole and skatole) using gas chromatography/mass spectrometry. VOC emission rates increased linearly with increasing wind velocity. These results show that wind velocity is a major factor affecting VOC emissions from AFOs. Selection of representative air velocity or sweep air flow rate is critical when estimating VOC emissions using wind tunnels and flux chambers.