Air Quality Measurements at a Laying Hen House: Experimental Methods 1 A. J. Heber 2, J.-Q. Ni, and T.-T. Lim

Transcription

1 ABSTRACT Air Quality Measurements at a Laying Hen House: Experimental Methods 1 A. J. Heber 2, J.-Q. Ni, and T.-T. Lim Measurements of air emissions from confined animal buildings are perhaps more challenging for laying hens than for any other species. Modern laying houses typically have the greatest volume, the greatest mean live mass density, the greatest number of exhaust fans, the highest ridge, the largest particles, and the highest concentrations of ammonia and particulate matter (PM). This paper describes a comprehensive air emission measurement program carried out for over six months at a 250,000-hen high-rise caged-hen building. The contaminants studied included total suspended particulates (TSP), PM 10, PM 2.5, ammonia (NH 3 ), hydrogen sulfide (H 2 S), carbon dioxide (CO 2 ), and odor. Besides quantifying these air emissions, the objective of this field test was to study and improve measurement strategies and methods with a goal of developing standard protocols. Continuous measurements of gas and PM concentrations, building static pressure and airflow, inside and outside temperature and humidity, wind speed and direction, and barometric pressure were conducted. Extractive air sampling was used to provide continuous gas streams to two sets of gas analyzers and to fill sample bags for odor evaluations. NH 3, H 2 S, CO 2, and odor were measured using chemiluminescence, pulsed fluorescence, photoacoustic infrared detectors, and olfactometry, respectively. Ventilation rates were assessed using electronic monitoring of fan operation and static pressure, small vane anemometers, a portable fan tester, and a certified fan testing laboratory. Data was published continuously to a web page for improved project oversight. Several subtests and comparisons of methods were conducted resulting in improved techniques and recommendations for future research. Keywords: Livestock, ventilation, dust, air pollution, chickens, emission INTRODUCTION AND OBJECTIVES Buildings play an important role in the emissions of particulate matter (PM), ammonia (NH 3 ), hydrogen sulfide (H 2 S), and odor emitted by livestock and poultry facilities, which have recently drawn increasing amounts of attention by government agencies in the United States. More reliable scientific air emission data are needed for all parties involved with this issue. However, accurate building emission measurements are not trivial, and careful planning and implementation of field studies are necessary to obtain quality data (Heber, 2003). The methodology used in European studies of air emissions from livestock buildings in the 1990s were published five years ago (Hinze and Linke, 1998; Phillips et al. 1998). These authors described techniques for automatically monitoring gas and PM emissions. Using these concepts and techniques, a comprehensive field test involving eight large swine finishing houses and up to 12 months of continuous gas emission monitoring resulted in several reports of data (Heber et al., 1997, 1998, 2000; Lim et al., 1999; Ni et al., 1999, 2000ab, 2002abc) and recommendations for improving future studies (Heber et al., 2001). This project focused on obtaining greater spatial and diurnal resolution in a single building, on testing existing methods, and introducing new 1 International Symposium on Control of Gaseous and Odour Emissions from Animal Production Facilities, Horsens, Denmark, June 2-4, pp Dept of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN ; phone: ; fax: ; heber@purdue.edu 1

2 techniques with the ultimate goal of developing standard protocols for building emission measurements. The objectives of this paper are: to describe the building, equipment, and methodology used to conduct the test, to describe the comparison tests of methods conducted during the study, and to make recommendations for improving measurement protocols. MATERIALS AND METHODS Description of Overall Monitoring Plan The laying house, located 60 km from campus, was oriented E-W and was located in the NW corner of a complex of 14 houses and one of two new houses built in The mean inventory in the 36.6 m x 183 m building was 246,113 hens and the average bird mass was 1.55 kg. Lights were automatically shut off at night. An automatically-adjusted ceiling inlet over each of the 10 rows of cages admitted air into the second floor from the attic. Ceiling inlet openings were controlled in three zones along the length of the building (east, middle and west). On the 3.7-m high second floor, the hens were kept in ten, 177-m long rows of cages. A narrow slot in the floor beneath each row of cages communicated manure and ventilation air into the pit. Manure was scraped daily from the cages into the slots. Ventilation air flowed through the slots into the pit as a result of underpressure created by 4 to 73, 1.23-m diameter exhaust fans in the first floor. Ventilation stages 1 through 8 had 4, 5, 9, 9, 9, 9, 15 and 13 exhaust fans (Model , Choretime-Brock, Milford, IN), respectively. The building environmental control system used 15 temperature sensors (5 rows x 3 sensors per row). Twenty-five, 92-cm dia. circulation fans (Choretime-Brock Model ), suspended from the ceiling of the first floor, promoted drying of stored manure. The emission monitoring plan focused on direct source measurements by sampling from exhaust air while accounting for background concentrations in the air inlets and providing information about bird exposure to the pollutants (fig. 1). Instruments were housed in a mobile shelter near the middle of the south sidewall (fig. 2). A significant portion of the instrumentation and equipment described by Heber et al. (2001), including two sets of gas analyzers (fig. 3), was used in this study. One set of analyzers was used to assess diurnal variation at location 7 (fig. 1). The other set of analyzers was used to assess spatial variation among eight exhaust fans, two cage locations, and the incoming attic air. Since ventilation air flowed sequentially through the attic, the second floor (cages), and the first floor (manure pit), in that order, the cage locations (air leaving the caged area) were allocated to allow partitioning of emissions between the first and second floors. Air was drawn sequentially from several building locations for gas analysis. The nine exhaust locations were distributed among four, continuous, stage-1 fans (locations 1, 3, 7 and 9) and the five stage-2 fans (locations 2, 4, 5, 6, and 8) (fig. 1). Time resolution of exhaust air measurements was decreased when stage 2 was shut off in cold weather because the sampling sequence was fixed, even in winter. The distributed nature of the numerous exhaust fans coupled with the potential for spatial variation in concentrations severely challenged the required representativeness of the exhaust air concentration measurement. Fortunately, however, the fans of stages 1 and 2 were distributed evenly among the other 64 fans (fig. 1). Sampling location groups (SLG) (Heber et al., 2001) were used for ventilation inlet air and the cage locations (animal exposure). Until the animal exposure group was added on March 8, the three ceiling inlet locations were sampled individually. Because the inlet control was based on temperature instead of pressure, the inlets in the western third of the building were sometimes opened too wide and allowed warm contaminated air to rise into the attic, causing error in the background measurement. Thus, background measurement locations should be moved to a location less vulnerable to errors. 2

3 To instrument shelter AD592 temperature sensors Air sampling locations Vane anemometer RH/temp probe Static pressure port TEOM sensors Instrument shelter Met tower Cages End view Pit Floor plan (186 m x 30 m) Mixing manifold Air inlet group 12 Animal exposure group Exhaust air locations N Instrument shelter Side view Hall Attic Cages Pit Figure 1. End view, floor plan and side view of laying house with locations of instruments, sensors and instrument shelter. Measurements began in November Description of the Gas Sampling System The gas sampling system (GSS) was conceptually similar to that used previously (Heber et al., 2001), but there were several important differences (fig. 4): 1. An in-line flow restrictor was used in the exhaust line of the pump to reduce the airflow to about 3.6 L/min. The restrictor was manufactured by trial and error from a small piece of Teflon inserted into the Teflon sample tube. 2. The analyzer manifold was located downstream of the sampling pump resulting in a slight positive pressure in the manifold instead of a relatively high underpressure (Heber et al., 2001). 3. An in-line mass flow meter for monitoring sample flow rate (fig. 4) was introduced late in the study and tested successfully for several weeks. 4. A bidirectional differential pressure sensor (fig. 4) was briefly tested on the last day of the study for monitoring the underpressure in the probe manifold. 5. Bypass pumping (Heber et al., 2001) was used only for a short time. It shortens response time of the gas analysis system depending on total sample residence time. 6. The GSS provided sample air to two sets of analyzers. Sampling of a single line by both sets simultaneously was carefully avoided. 7. The mixing, probe and analyzer manifolds were smaller than previous versions to reduce the wetted surface area and the sample residence time. 8. The number of sampling locations or SLGs was twelve compared with six, resulting in a longer sampling cycle (2 h). 9. A background location (ceiling inlets) was included in each sampling cycle. 3

4 During each sampling cycle, the locations numbered 1 to 12 (fig. 1) were sampled with the following sequence: 5, 12, 2, 9, 6, 11, 4, 1, 8, 10, 3. The sampling period was 10-min except for a short test when a 5-min sampling period was implemented. Figure 2. Instrument shelter near south wall of laying house. Figure 3. J.-Q. Ni checks analyzers in instrument shelter. Photo by V. Walters. 4

5 Sample lines Solenoid valves M1 P1 M2 Sampling bag Gas analyzers (Set 1) NH 3 F1 H 2 S F2 CO 2 Exhaust Mass Gas analyzers (Set 2) M3 flow P4 NH meter 3 F3 M4 H 2 S P2 f F4 CO 2 Flow restrictor Gas standards Pressure p SO sensor* H 2 S 2 NH NO ml/min rotameter** CO 2 Zero air P3 *Tested briefly at end of study. **Used to test individual solenoids for leaks. Figure 4. Gas sampling and analysis system. F, Teflon filter; M, manifold; P, air pump. Real-Time PM Monitoring PM 10 was monitored with a Tapered Element Oscillating Microbalance (TEOM), which utilizes microweighing technology (Heber et al., 2000b), between November 14 and January 27. A second TEOM was collocated with the first TEOM between January 28 and March 31. Four collocated TEOMs were tested between April 1 and June 8. The multiple TEOMs at the fan inlet (fig. 5) facilitated several tests of various methods and configurations (table 1). A primary representative exhaust fan (PREF) must be identified when there is only one measuring point for exhaust air, which is necessary with expensive real-time PM measurements (Heber et al., 2002b). For this building, the 17 th fan from the east end of the south wall was selected as the PREF. Some problems observed with the use of the TEOM in the laying house were rapid loading of filters (7 d or less), vacuum line condensation, sensitivity of mass concentration to relative humidity, and clogging of insect screens (Heber et al., 2002). Gas Measurements NH 3 and H 2 S were measured using chemiluminescence and pulsed fluorescence after conversion to NO and SO 2, respectively, as described by Heber et al. (2001). Although the nominal range of the NH 3 analyzer was 100 ppm, it was increased to 200 ppm by reducing instrument sensitivity by 5

6 50%. A comparison between the NO and N t modes of the NH 3 analyzer showed that the response time is shorter when the analyzer is in the N t mode (NO and NO 2 assumed negligible). The ppm and 27-ppm span gases used for NH 3 calibrations were much lower than winter exhaust concentrations (50 to 150 ppm), but similar to warm weather concentrations of 15 to 30 ppm. Table 1. Summary of tests conducted with the TEOMs. Date(s) Description of Tests n 11/14 Started one TEOM 1 11/20-3/27 Collocated FRM with TEOM PM /31-1/30 Pilot test of wind break (no control) 1 1/14-1/27 Pilot test of 30 C sensor (no control) 1 1/28-2/24 Collocated two TEOMs - 2/25-3/10 Tested effect of cleaning 1 3/11-3/17 Observed effect of replacing filter 1 3/18-3/24 Tested effect of wind break 1 3/25-3/31 Compared new with loaded filters 1 4/1-4/18 Collocated four TEOMs - 4/19-4/26 Tested effects of air inlet height 2 4/29-5/1 Compared 30 C with 50 C temp. 2 5/6-5/12 Compared TSP with PM /20-5/26 Compared new with loaded filters 2 5/17-6/2 Tested effects of external screen 2 6/3-6/8 Collocated PM 2.5, PM 10 and TSP 1 Figure 5. A.J. Heber inspects two collocated TEOMs. Photo by Vince Walters. 6

7 The 4.3-ppm span gas used for H 2 S calibrations until April 12 was much greater than the measured concentrations of less than 50 ppb (Lim et al., 2003). The 670-ppb H 2 S span gas used after April 12 was a big improvement, but a dynamic dilution system would have allowed the introduction of spans that were in the same range as the measurements. Span gases were introduced into the analyzer manifold (M4 in fig. 4). A gas analyzer was first challenged with zero air, and was adjusted, if necessary and if possible, after recording the displayed concentration. It was challenged next with a span gas, and was adjusted to its concentration after recording the displayed concentration. The difference between the numbers is analyzer drift (fig. 6). Zero and span checks using bagged calibration gases were conducted twice to test the response and calibration of the entire gas sampling system. The 50-L Tedlar bags were attached to the sampling probe of the longest sampling line (approximately 200 m long) until nearly emptied during a 10 min sampling period at 3.6 L/min. Tests were conducted to compare the sampling of odor at the fans compared with using the GSS to fill the bags by attaching them to the exhaust of the analyzer manifold M4 (fig. 3). It was concluded that there was no difference in odor concentration (Heber et al., 2002) Drift, ppm /5 12/26 1/16 2/6 2/27 3/20 4/10 5/1 Date of 2001 Figure 6. Differences between recorded and span (4300 ppb) H 2 S before adjustment. Airflow Measurements The importance of measuring airflow accurately for building emission studies is well documented (Heber et al., 2001; Casey et al., 2002). In this project, a special effort was undertaken to account for degradation of published fan curves due to dust buildup, belt wear, etc., and for instantaneous airflow variations (Heber, 2003). Two fans were removed from the building and tested at the University of Illinois Bioenvironmental Systems and Simulations (BESS) lab (Ford et al., 2001) before and after cleaning and belt renewal. The as-found fans delivered 7 to 24% less airflow as compared with published fan curves, depending on static pressure. A portable fan tester (Casey et al., 2002) used on the outlets of the exhaust fans was calibrated with these fans at the BESS lab 7

8 and used to determine the airflow of 22 other fans in the building (Lim et al., 2003). Static pressure was used with the new curves determined per fan stage to estimate airflow as follows: ( P P ) Q P = S where Q P = fan airflow (plastic shutter), S is a correction factor (0.858, 0.882, 0.905, 0.929, 0.953, 0.976, 1.00, and for stages 1 to 8, respectively), and P is static pressure. ( P P ) Q M = S where Q M = fan airflow (metal shutter). The concept of continuously monitoring airflow with BESS-calibrated small vane anemometers (SVAs) immediately downstream of the fan impeller was pilot tested using 18-cm and 45-cm diameter free-wheeling impellers. It was observed that cleaning the anemometers at least weekly is needed to maintain their calibration at laying houses. Data Acquisition System A commercial data acquisition (DAQ) software (Labview for Windows, National Instruments, Austin, TX) was used with the DAQ hardware described by Heber et al. (2001). A wireless connection to an internet service provider near the farm was found to be quite reliable and made the following things possible that enhanced quality assurance and quality control: 1. Web publishing of real-time data (fig. 7) 2. Daily ing of 24-h data files. 3. ing of instant warning messages when alarm limits were exceeded. 4. Remote access to the DAQ PC. RECOMMENDATIONS FOR FUTURE STUDIES The following recommendations are based on the experience gained from this project: 1. Measure the ambient PM 10 concentration (Heber et al., 2002b). 2. Randomize sampling sequence to reduce systematic bias caused by previous sample residue. 3. Move background sample line outside the barn and measure less frequently. 4. Introduce calibration gases into the probe. 5. Utilize a programmable dynamic dilution system for calibration gases. ACKNOWLEDGEMENTS Support from the U.S. EPA and Rose Acre Farms was appreciated. The authors acknowledge assistance of John Z. Gallien, Douglas J. Riggs, Curtis M. Daly, Craig S. Pendl, and Norb D. Schmidt. 8

9 Figure 7. Web-published front panel of PC DAQ for emission measurements. REFERENCES Casey, K.D., Wheeler, E.F., R.S. Gates, H. Xin, P.A. Topper, J. Zajaczkowski, Y. Liang, A.J. Heber, and L.D. Jacobson Quality assured measurements of animal building emissions: Part 4. Airflow. Symposium on Air Quality Measurement Methods and Technology, San Francisco, CA: November 13-25, Air and Waste Management Association: Pittsburgh, PA. Ford, S. E., G. L. Riskowski, and L. L. Christianson Agricultural Ventilation Fans: Performance and Efficiencies. Bioenvironmental and Structural Systems Laboratory, University of Illinois, Urbana-Champaign, Ill. Heber, A.J., R.K. Duggirala, J.Q. Ni, M.L. Spence, B.L. Haymore, V.I. Adamchuk, D.S. Bundy, A.L. Sutton, D.T. Kelly, and K.M. Keener Manure treatment to reduce gas emissions from large swine houses. International Symposium on Ammonia and Odour Control from Animal Production Facilities, Vinkeloord, The Netherlands, October 6-10, pp Heber, A. J., D. S. Bundy, T. T. Lim, J. Q. Ni, B. L. Haymore, C. A. Diehl, and R. K. Duggirala Odor emission rates from swine finishing buildings. In Proc. Animal Production Systems and the Environment, Des Moines, IA, July. Heber, A.J., J.Q. Ni, T.T. Lim, C.A. Diehl, A.L. Sutton, R.K. Duggirala, B.L. Haymore, D.T. Kelly, and V.A. Adamchuk Effect of a manure additive on ammonia emission from swine finishing buildings. Trans. ASAE 43(6):

10 Heber, A.J., J.Q. Ni, B.L. Haymore, R.K. Duggirala, and K.M. Keener Air quality and emission measurement methodology at swine finishing buildings. Trans. ASAE 44(6): Heber, A.J., J.-Q. Ni, T.T. Lim, P.C. Tao, A.M. Millmier, L.D. Jacobson, R.E. Nicolai, J. A. Koziel, S.J. Hoff, Y. Zhang, and D.B. Beasley Quality assured measurements of animal building emissions: Part 1. Gas concentrations. Symposium on Air Quality Measurement Methods and Technology, San Francisco, CA: November 13-25, Air and Waste Management Association: Pittsburgh, PA. Heber, A.J., Fakhoury, K.J., T.T. Lim, J.-Q. Ni Measuring odor emissions from livestock buildings using olfactometry. ASAE Paper No , 16 pp. Heber, A.J Air emission measurements at livestock houses. Resource 10(4):7-8. Hinz, T., and S. Linke A comprehensive experimental study of aerial pollutants in and emissions from livestock buildings. Part 1: Methods. J. Agric. Eng. Res. 70: Lim, T.T., A.J. Heber, J.Q. Ni, and C.A. Diehl Production of carbon dioxide in swine finishing houses with deep pits. ASAE Paper No , 10 pp. Lim, T.-T., A.J. Heber, and J.-Q. Ni Air quality measurements at a laying hen house: Odor and hydrogen sulfide emissions. International Symposium on Control of Gaseous and Odour Emissions from Animal Production Facilities, Horsens, Denmark, June 2-4. Ni, J.Q. A.J. Heber, C.A. Diehl, and T.T. Lim. 2000a. Ammonia, hydrogen sulfide and carbon dioxide release from pig manure in under-floor deep pits. J. Agric. Eng. Res. 77(1): Ni, J. Q., A.J. Heber, T.-T. Lim, C. A. Diehl, R. K. Duggirala, B. L. Haymore, and A. L. Sutton. 2000b. Ammonia emissions from a large mechanically-ventilated swine building during warm weather. J. Environ. Qual. 29(3): Ni, J.-Q., A.J. Heber, C.A. Diehl, T.-T. Lim, R.K. Duggirala, and B.L. Haymore. 2002a. Characteristics of hydrogen sulfide concentrations in mechanically ventilated swine buildings. Canadian Biosystems Engng 44(6): Ni, J.-Q., A.J. Heber, T.-T. Lim, C.A. Diehl, R.K. Duggirala, and B.L. Haymore. 2002b. Hydrogen sulfide emission from two large pig finishing buildings with long term high frequency measurements. J. Agric. Sci. 138(2): Ni, J.-Q., A.J. Heber, C.A. Diehl, T.T. Lim, R.K. Duggirala, and B.L. Haymore. 2002c. Summertime concentrations and emissions of hydrogen sulfide at a mechanically-ventilated swine finishing building. Trans. ASAE 45(1): Phillips, V. R., M. R. Holden, R. W. Sneath, J.L. Short, R. P. White, J. Hartung, J. Seedorf, M. Schröder, K. H. Linkert, S. Pedersen, H. Takai, J. O. Johnsen, P. W. G. Groot Koerkamp, G. H. Uenk, R. Scholtens, J. H. M. Metz, and C. M. Wathes The development of robust methods for measuring concentrations and emission rates of gaseous and particulate air pollutants in livestock buildings. J. Agric. Eng. Res. 70: