LABORATORY MEASUREMENT OF HYDROGEN SULFIDE AND SULFUR DIOXIDE RELEASES FROM SWINE MANURE OF DIFFERENT SOLID CONTENTS

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1 Paper No An ASAE Meeting Presentation LABORATORY MEASUREMENT OF HYDROGEN SULFIDE AND SULFUR DIOXIDE RELEASES FROM SWINE MANURE OF DIFFERENT SOLID CONTENTS by Summary: J. Q. Ni (1) A. J. Heber (1) K. J. Fakhoury (1) P. Shao (1) Research Associate Associate Professor Research Associate Graduate Research Assistant A. L. Sutton (2) D. Kelly (2) J. A. Patterson (3) S. T. Kim (1) Professor Research Assistant Associate Professor Visiting Professor (1) Agricultural & Biological Engineering Dept. Purdue University, West Lafayette, IN Written for presentation at the 2000 ASAE Annual International Meeting Sponsored by ASAE Milwaukee, WI July 9-12, 2000 (2) Animal Sciences Dept. Purdue University, West Lafayette, IN Releases rates of hydrogen sulfide (H 2 S) and sulfur dioxide (SO 2 ) from finishing swine manure of two different solid contents and two initial manure accumulation days were measured under laboratory conditions for one month. Manure was stored in reactors of 122 cm height and 38 cm diameter. The reactors were continuously ventilated with 7.7 L/m of fresh air. Temperature was controlled at 20 C. Mean H 2 S release in all manure treatments ranged from 75 to 146 µg/h per reactor or 0.7 to 1.3 mg/h per m 2 of manure surface. The effect of manure solid contents and initial manure accumulation days on H 2 S releases was not consistent. Mean SO 2 release in the four manure treatments ranged from 24 to 30 µg/h. The effect of manure solid contents and initial accumulation days on SO 2 releases was not significant. There were evident fluctuations of H 2 S and SO 2 releases during the test. High gas release rates occurred about two days after initial manure addition. High gas releases were also observed after some weekly manure additions. Keywords: Air quality, environment, gas emission, agriculture, measurement The author(s) is solely responsible for the content of this technical presentation. The technical presentation does not necessarily reflect the official position of ASAE, and its printing and distribution does not constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review process by ASAE editorial committees; therefore, they are not to be presented as refereed publications. Quotation from this work should state that it is from a presentation made by (name of author) at the (listed) ASAE meeting. EXAMPLE -- From Author's Last Name, Initials. "Title of Presentation." Presented at the Date and Title of meeting, Paper No. X. ASAE, 2950 Niles Rd., St. Joseph, MI USA. For information about securing permission to reprint or reproduce a technical presentation, please address inquiries to ASAE. ASAE, 2950 Niles Rd., St. Joseph, MI USA Voice: FAX: <hq@asae.org>

2 Laboratory Measurement of Hydrogen Sulfide and Sulfur Dioxide Releases from Swine Manure of Different Solid Contents by J. Q. Ni, A. J. Heber, K. J. Fakhoury, P. Shao, A. L. Sutton, D. Kelly, J. A. Patterson and S. T. Kim INTRODUCTION Hydrogen sulfide (H 2 S) is considered the most dangerous gases in animal buildings. It has been responsible for many animal as well as human deaths in animal facilities (Field, 1980; Osbern and Crapo, 1981; Hagley and South, 1983; Anonymous, 1996). Critically high concentrations of H 2 S in confined swine facilities were related to agitation of manure during pump-out when large quantities of H 2 S were released (Patni and Clarke, 1991) or when insufficient ventilation existed. However, in normally ventilated buildings without manure agitation, the H 2 S concentration is usually below 1000 ppb (Muehling, 1970; Heber et al., 1997; Ni et al., 1999a). Some States have implemented ambient H 2 S limits. For example, the Minnesota Pollution Control Agency has implemented a state monitoring program for ambient H 2 S concentrations at the property line around livestock facilities (MPCA, 1999). Heber and Heyne (1999) analyzed some data at a large pig facility and reported 10-day mean concentrations at the property line (under downwind conditions only) between 4 and 22 ppb during a five-month monitoring period. The first available report on measurement of emission from swine buildings was published 25 years ago (Avery et al., 1975). In recent years more and more studies were conducted on H 2 S emissions (Heber et al., 1997; Jacobson, 1997; Jacobson et al., 1997; Ni et al., 1998; Jacobson et al., 1999; Bicudo et al., 2000; Ni et al., 2000a; Ni et al., 2000b; Zhu et al., 2000). There was also effort made to investigate the mass transfer coefficient of H 2 S from swine manure (Arogo et al., 1999). However, there is yet no available report studying the effect of manure solid contents and manure age on H 2 S releases. Sulfur dioxide (SO 2 ) is one of the six criteria pollutants defined in the US Clean Air Act. However, information of agriculture related SO 2 can hardly be found. Although a recent report of USEPA (2000) published a figure of about million tons of total national SO 2 emission in 1998, there was no agricultural/biological sources included. However, at locations with large quantities of manure storage, like animal barns, there may have certain SO 2 release and concentration. If the release and concentration are high, SO 2 may have negative environmental and health impacts. In the USEPA National Ambient Air Quality Standards (NAAQS), the SO 2 annual arithmetic mean is 0.03 ppm (primary standard), the SO 2 24-hour average is 0.14 ppm (primary standard) and the SO 2 3-hour average is 0.50 ppm (secondary standard). The primary standards set limits to protect public health, including the health of "sensitive" populations such as asthmatics, children, and the elderly. The secondary standards set limits to protect public welfare, including protection against decreased visibility, damage to animals, crops, vegetation, and buildings. Release or emission of H 2 S was found related to temperature, ventilation and animals under field conditions (Ni et al., 1998). In laboratory studies, it was affected by air temperature, manure temperature and air velocity (Arogo et al., 1999). Ni et al. (2000a; 2000b) reported a special 2

3 behavior of burst H 2 S release in swine houses, which suggested that more factors, some still unknown, play important roles in the process of H 2 S and probably also SO 2 releases from liquid manure. Supported by the National Pork Producers Council, a laboratory pilot study on emissions of odor, volatile organic compounds (VOC) and gases, including ammonia (NH 3 ), carbon dioxide (CO 2 ), H 2 S and SO 2, from swine manure was conducted from October 18 to November 18, Swine manure with two different solid contents and two initial accumulation days was used. Hydrogen sulfide and SO 2 were measured during the test. The objectives of this paper were to study: 1. quantities of releases and concentrations of H 2 S and SO 2 obtained with continuous measurement; 2. effects of manure solid contents and initial manure accumulation days on the releases of H 2 S and SO 2, and 3. fluctuations of H 2 S and SO 2 releases and effects of weekly manure addition on the releases. MATERIALS AND METHODS Swine manure was tested in 39 reactors of 122 cm height and 38 cm diameter. The reactors were made of white PVC. The headspace of the reactors was lined with Tedlar sheets. There were an air inlet, an air outlet, an odor/voc sampling port, and a manure operation port on the top of each reactor. Different manure treatments were assigned randomly to the reactors, which were installed in a temperature-controlled room at 20 C. The manure was collected from a commercial swine finishing farm in Indiana and was transported in a plastic tank to the laboratory. Two batches of manure, old and new, were filled in the reactors on October 18. The old and new manure had four weeks and one week accumulation time, respectively. After the reactors treated with undiluted manure had been filled, water was added to dilute the manure to 50% of the original concentrations and filled to the reactors treated with diluted manure. The initial filling pumped 69.6 L of manure into each reactor (61 cm manure depth inside the reactor). New manure was added to all reactors four times during the test, on 10/22, 10/29, 11/5 and 11/12. Each reactor received 5.8 L manure in each additional filling, which added 5.1 cm manure depth in each reactor. The manure to the reactors with diluted treatment in the additional fillings was also diluted the same way as in initial filling. During the initial and additional fillings, manure in the plastic tank was agitated with a pump starting 15 minutes before filling. The agitation continued until the filling finished to ensure homogeneity of the manure. The agitation continued until the fillings finished to ensure homogeneity of the manure. Three manure samples were obtained during initial filling. Four or five samples were obtained during each additional filling. At the end of the test, one manure sample was taken from each reactor. The manure samples were analyzed in the Purdue Animal Sciences Waste Management Laboratory. Fresh air was continuously supplied by a compressor to the reactors at a mean rate of 7.74 L/min through an air supply system consisting of some filters, pressure regulators, manifolds and orifices (Figure 1). 3

4 Exhaust air from each reactor was conducted to a manifold for six minutes in order to measure airflow rate and gas concentrations. The timing of the measurement was controlled by a PC through 40 three-way solenoids for 40 air streams consisting of one fresh air from the air supply system, one reactor containing water and 38 reactors containing manure. The fresh air and reactors numbered 1 to 19 were initially measured starting from October 19. Twelve measurements daily were obtained for each reactor. From November 3, 39 reactors were all included in the measurement. The number of daily measurements for each reactor was reduced to six. Measurement data, acquired every 20 seconds, were averaged every minute and recorded to the PC by a data acquisition system. The first five of the six minutes of gas concentration data in each reactor were not used in data processing in order for the measurement system to reach equilibrium. This paper presents data from 18 of the reactors, of which the measurements were the most complete. The 18 reactors included 5 for old manure, 5 for old diluted manure, 4 for new manure and 4 for new diluted manure. Air compressor Exhaust hood After cooler Oil filter F S 1 S 0 M 3 NH 3 F Pump P R 1 H 2 S O0 O 1 F S 2 M 2 Flow meter CO 2 Charcoal filter Pressure regulator Pressure regulator M 1 O 2 O n R 2 F Gas analyzers Flow meter F: Teflon holder & filter M: manifold O: precision orifice P: pressure transmitter R: manure reactor S: 3-way solenoid R n F S n Gas analyzer calibration loop From gas cylinders Figure 1. Schematic of reactor ventilation and continuous emission measurement system. Hydrogen sulfide and SO 2 concentrations were measured with a SO 2 analyzer (Model 45, TEI, Inc., Mansfield, MA) combined with a H 2 S converter (Model 340, TEI, Inc.). Hydrogen sulfide was first converted to SO 2 with the converter. The SO 2 was measured with the pulsed fluorescence SO 2 analyzer. This instrument had data averaging time of 60 seconds and a maximum measurement range of 10,000 ppb. Its sample flow rate was 1.0 L/min. It was calibrated weekly before, during and after the test with certified gases, 2690 ppb H 2 S and 2700 ppb SO 2. Airflow rates were measured with a Model 50S-10 mass flow meter (McMillan Company, Georgetown, TX). Gas release rates were calculated by multiplying the gas concentrations by the airflow rates. Heber et al. (2000) provided a more detailed description of the test set up. 4

5 RESULTS Partial analysis results of six batches of manure for initial and additional fillings are presented in Table 1. The ph values of the manure ranged from 6.88 to After dilution, the dry matter contents dropped to about 49 to 61% of the undiluted manure and the wet base ash content dropped to about 50 to 68% of the undiluted manure. Table 1. Selected analysis results of six batches of manure for initial and additional fillings. Manure * Number of Dry matter Ash (%) ph samples (%) Dry base Wet base 10/18/1999 Old Old diluted /18/1999 New New diluted /22/1999 Undiluted Diluted /29/1999 Undiluted Diluted /05/1999 Undiluted Diluted /12/1999 Undiluted Diluted * Only initial filling on October 18 had different manure accumulation days (old and new). Table 2 presents partial analysis results of the manure sampled in the reactors at the end of the test. The difference between ph values from the undiluted and diluted manure was The dry matter content of the new diluted manure was 53% of the new manure and that of the old diluted manure was 55% of the old manure. The wet base ash in the new diluted manure was 55% of the new manure. In the old diluted manure, the wet base ash was 53% of that in the old manure. Table 2. Selected analysis results of the manure from individual reactors at the end of the test. Treatment Number of Dry matter Ash (%) ph Reactors (%) Dry base Wet base New New diluted Old Old diluted

6 About 160 reliable 6-minute measurements were obtained for H 2 S and SO 2 release rates for each manure treatment (Table 3). The mean H 2 S releases ranged from 75 to 146 µg/h for the four treatments. The new undiluted manure released more H 2 S (105 µg/h) than the new diluted manure (98 µg/h). However, for the old manure, diluted treatment released almost twice as much H 2 S (146 µg/h) as the undiluted treatment (75 µg/h). The minimum H 2 S releases were close to 0 µg/h and the maximum ranged from 414 to 1283 µg/h for the four treatments during the entire test. Table 3. Selected statistics of the hydrogen sulfide and sulfur dioxide release rates in the test. New New diluted Old Old diluted H 2 S Mean (µg/h) * 105±20 98±13 75±10 146±19 Min (µg/h) Max (µg/h) n SO 2 Mean (µg/h) * 27±5 27±5 24±4 30±6 Min (µg/h) Max (µg/h) n * Mean concentration ± 2 times standard error. The mean SO 2 releases ranged from 24 to 30 µg/h for the four treatments. The undiluted and diluted treatments had the same mean SO 2 release rates for the new manure. The minimum SO 2 releases were 0 µg/h for all the four treatments. The maximum SO 2 releases ranged from 119 to 175 µg/h. Figure 2 and Figure 3 illustrate the fluctuations of the H 2 S and SO 2 releases during the test, respectively. The highest H 2 S release rate occurred on the second day of initial manure addition. There were three H 2 S release peaks, each lasted for several days, during the entire test. The highest releases of SO 2 occurred during the first week of the test. In the middle of the test, the SO 2 releases for all the treatments were quite low. During the last nine days, the SO 2 releases came up and remained at about 30 µg/h. Hydrogen sulfide concentrations ranged from 0 to 3506 ppb for the four treatments (Table 4). The highest concentration of 3506 ppb was detected at the beginning of the test in the new manure reactors. The minimum concentrations for the four treatments were zero or close to zero ppb. The mean concentrations of each treatment ranged from 113 ppb for old manure to 223 ppb for old diluted manure. Sulfur dioxide concentrations ranged from 0 to 364 ppb. Mean concentrations of SO 2 in the four treatments were quite close. 6

7 1500 New New diluted H 2 S release (µg/h) Old Old diluted 0 10/18 10/23 10/28 11/2 11/7 11/12 11/17 Date Figure 2. Fluctuations of hydrogen sulfide release rates from different manure treatments during the test (arrows indicate the days of manure addition). 200 New New diluted SO 2 release (µg/h) Old Old diluted 0 10/18 10/23 10/28 11/2 11/7 11/12 11/17 Date Figure 3. Fluctuations of sulfur dioxide release rates from different manure treatments during the test (arrows indicate the days of manure addition). 7

8 Table 4. Selected statistics of hydrogen sulfide and sulfur dioxide concentrations during the test. Mean * (ppb) Min (ppb) Max (ppb) n H 2 S New 181± New diluted 146± Old 113± Old diluted 223± SO 2 New 24± New diluted 21± Old 19± Old diluted 24± * Mean concentration ± 2 times standard error. DISCUSSION Reported H 2 S emissions from finishing swine buildings under field conditions in Indiana, Illinois and Minnesota ranged from 5.0 to 95.4 mg/h per m 2 of release area (Table 5). In the present study, the maximum H 2 S release flux was 11.3 mg/h per m 2 of manure surface. The mean releases from the four treatments ranged only from 0.7 to 1.3 mg/h per m 2, much lower than the reported field measurements. However, the H 2 S concentrations in the present study are within the reported H 2 S concentrations measured in some commercial swine buildings (Heber et al., 1997; Ni et al., 1999b). The reason of low release fluxes in this laboratory study was the low ventilation rate per m 2 of manure surface compared with the reported field measurements. Table 5. Reported hydrogen sulfide emissions from commercial swine finishing buildings. H 2 S emission Number of (mg/h m 2 ) Buildings Building type References 7.8 and Naturally-ventilated Heber et al. (1997) Mechanically ventilated Ni et al. (1998) 5.0, 16.2 and Deep pit buildings Jacobson et al. (1999) 18.3 and Mechanically ventilated Ni et al. (1999b) Naturally ventilated Bicudo et al. (2000) Mechanically ventilated Zhu et al. (2000) Naturally ventilated Zhu et al. (2000) Since no available report of SO 2 release from manure was found, it is difficult to compare our results with the literature. If the ratio of SO 2 to H 2 S in swine buildings were close to the ratio of the two gases in this study, we expect that as high as about 360 ppb of SO 2 could also be found in swine buildings. 8

9 Statistical analysis (ANOVA) of mean H 2 S release rates showed that significant differences existed for manure treatments of old vs. old diluted, new vs. old, and new diluted vs. old diluted (P<0.01). The new manure released 40% more H 2 S than the old manure, but the old diluted manure released 49% more H 2 S than the new diluted manure. However, the difference of new vs. new diluted was not significant. It appeared that the effect of manure solid contents on H 2 S release was not consistently significant. Variations of the SO 2 releases between treatments were smaller as compared with the H 2 S releases. Mean release rates of SO 2 in the four treatments ranged from 21 to 32% of those of H 2 S. There were no significant differences for SO 2 releases between all the treatments. Unlike field tests, where diurnal and seasonal variations of H 2 S emissions existed (Ni et al., 1999b), the fluctuations of gas releases in this laboratory test were not correlated to diurnal patterns. The evident reason was that there were no diurnal changes of temperature during the test. Since the ventilation air supply to the reactors was kept constant, the magnitudes of fluctuations of gas concentrations and release rates were very similar. All four treatments appeared to have similar fluctuation patterns during the 30-day test for H 2 S (Figure 2). It was true for SO 2 too (Figure 3). Correlation coefficient calculation confirmed that release fluctuations for each gas followed a similar pattern in all the four treatments (Table 6). High correlation coefficients were obtained, except between H 2 S releases from diluted and undiluted new manure, which had only a coefficient of Different solid contents of the manure did not seem to influence the release patterns of the two gases. Table 6. Correlation coefficients of gas release from different manure treatments. New New diluted Old H 2 S New diluted Old Old diluted SO 2 New diluted Old Old diluted Addition of manure apparently affected the release quantities of both gases (Figures 2 and 3). Since the manure added to the reactors was agitated continuously, little dissolved gas of H 2 S and SO 2 in the manure was expected. The increases of gas releases after the manure additions were most probably caused by the new substrate brought in by the added manure. 9

10 There were peaks of H 2 S release rates in reactors with all treatments about one or two days after initial manure filling. Release rates gradually went down after the peak. Weekly manure addition seemed to increase the H 2 S release rates. High peaks of SO 2 releases also occurred one or two days after initial manure filling. The first manure filling appeared to increase the SO 2 release. However, the other manure addition did not show a consistent positive effect on the SO 2 release. Unlike the other additions, there were no evident increases of H 2 S and SO 2 release rates during the first three days after the addition of 10/29. The manure in this addition had higher dry matter contents (9.32% for undiluted and 5.68% for diluted) as compared with other batches of manure. However, it was unclear whether the higher solid contents were the only cause of the constant gas releases. Ni et al. (2000a; 2000b) previously reported a new phenomenon of burst releases of H 2 S, which lasted for one or several hours, in commercial swine buildings. Our unpublished data with continuous measurement of H 2 S and SO 2 releases from a single reactor demonstrated that the burst releases also existed under laboratory conditions. Peaks of high release rates were detected as high as three to ten times as the adjacent valley release rates and lasted only for about 10 to 20 minutes. Peak release rates almost occurred 30 times a day. This suggests that the gas release measurement of 12 and 6 times a day in this study might be too few and might have caused unexpected information loss. Arigo et al. (1999) studied H 2 S mass transfer coefficient by measuring the total sulfur remained in the manure. This was another method of sulfur gas study. It would be beneficial that higher measurement frequencies are used, and both headspace gas concentration and manure total sulfur are measured in further studies of H 2 S and SO 2 releases. CONCLUSIONS 1. Mean H 2 S release rates in all manure treatments ranged from 75 to 146 µg/h per reactor. They were equivalent to 0.7 and 1.3 mg/h per m 2 of manure surface, which were much lower compared with the reported H 2 S emission from commercial swine finishing buildings. However, H 2 S concentrations at the headspace of the reactors were within the range of reported concentrations found in swine buildings. 2. There were significant differences (P<0.01) of H 2 S release rates between manure treatments of old vs. old diluted, new vs. old, and new diluted vs. old diluted. Nevertheless, the effects of manure solid contents on the H 2 S release rate were not consistently significant. 3. Mean SO 2 release rates in the four manure treatments ranged from 24 to 30 µg/h. The ratio of SO 2 to H 2 S concentrations in ppb was about 1:10. There is a possibility that similar concentrations of SO 2 (up to about 360 ppb) also could be detected in swine finish buildings. The effects of manure solid contents and initial accumulation days on the SO 2 release rate were not significant. 10

11 4. There were evident fluctuations of H 2 S and SO 2 releases during the 30-day test. Releases of H 2 S in different manure treatments appeared to have a similar fluctuation pattern during the entire test. Releases of SO 2 demonstrated the same characteristics. Differences of manure solid contents and initial accumulation time did not seem to affect the release patterns of the two gases. 5. There was some effect of manure addition on the gas releases. High peak releases occurred one or two days of initial manure filling. Weekly manure additions seemed to increase the H 2 S release rates except for one addition with higher manure solid contents (dry matter 9.32% for undiluted and 5.68% for diluted manure). However, about half of the weekly additions did not cause increase of SO 2 release. 6. Using higher frequency measurement and adding the analysis of total sulfur content of the manure could improve further test. ACKNOWLEDGEMENTS This research was supported by the National Pork Producers Council (NPPC) and the Purdue University Agricultural Research Program. Technical assistance of Rick Page, Garry Williams, Scott Brand, Kenneth Lam and Kate Bachman was greatly appreciated. REFERENCES Anonymous Nightmare on the hog farm: Hydrogen sulfide claims two lives in Minnesota. The Biobulletin 3(2):1-3. Arogo, J., R.H. Zhang, G.L. Riskowski and D.L. Day Mass transfer coefficient for hydrogen sulfide emission from aqueous solutions and liquid swine manure. Transactions of the ASAE 42(5): Avery, G.L., G.E. Merva and J.B. Gerrish Hydrogen sulfide production in swine confinement units. Transactions of the ASAE 18: Bicudo, J.R., C.L. Tengman, L.D. Jacobson and J.E. Sullivan Odor, hydrogen sulfide and ammonia emissions from swine farms in Minnesota. In Conference Proceedings Odors and VOC Emissions 2000, Session 8. Cincinnati, Ohio, USA, April Water Environment Federation. 20 p. Field, B Rural health and safety guild: Beware of on-farm manure storage hazards. Cooperative Extension Service, Purdue University, West Lafayette, Indiana. S p. Hagley, S.R. and D.L. South Fatal inhalation of liquid manure gas. Medical Journal of Australia 2(9): 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 11

12 large swine houses. In International Symposium on Ammonia and Odour Control from Animal Production Facilities, eds Voermans, J.A.M. and G.J. Monteny. Vinkeloord, The Netherlands, Oct NVTL, PO-Box 83, 5240 AB Rosmalen, The Netherlands. Vol. II: Heber, A.J. and M.J. Heyne Outdoor hydrogen sulfide concentrations near a swine feeding facility. In ASAE/CSAE-SCGR Annual International Meeting. Toronto, Canada, July Paper No ASAE, 2950 Niles Rd., St. Joseph, MI USA. 23 p. Heber, A.J., J.Q. Ni, K.J. Fakhoury, A.L. Sutton and J.A. Patterson Laboratory testing of manure additives for odor control. In ASAE Annual International Meeting. Milwaukee, WI. July Paper No ASAE, 2950 Niles Rd., St. Joseph, MI USA. Jacobson, L.D Correlating sulfur sources and hydrogen sulfide emissions. Final report. University of Minnesota. December. 4 p. Jacobson, L.D., C.J. Clanton, D.R. Schmidt, C. Radman, R.E. Nicolai and K.A. Janni Comparison of hydrogen sulfide and odor emissions from animal manure storages. In International Symposium on Ammonia and Odour Control from Animal Production Facilities, eds Voermans, J.A.M. and G.J. Monteny. Vinkeloord, The Netherlands, Oct NVTL, PO- Box 83, 5240 AB Rosmalen, The Netherlands. Vol. II: Jacobson, L.D., D. Marcinek-Paszek, R.E. Nicolai, D.R. Schmidt, B. Hetchler and J. Zhu Odor and gas emissions from animal manure storage units and buildings. In ASAE/CSAE-SCGR Annual International Meeting. Toronto, Ontario Canada, July Paper No ASAE, 2950 Niles Rd., St. Joseph, MI USA. 11 p. MPCA Feedlot air quality summary: data collection, enforcement and program development. Minnesota Pollution Control Agency. March. Muehling, A.J Gases and odors from stored swine waste. Journal of Animal Science 30: Ni, J.Q., A.J. Heber, T.T. Lim, R. Duggirala, B.L. Haymore, C.A. Diehl and A.L. Sutton Hydrogen sulfide emissions from a mechanically-ventilated swine building during warm weather. In ASAE/CSAE-SCGR Annual International Meeting. Orlando, Florida, July Paper No ASAE, 2950 Niles Rd., St. Joseph, MI USA. 13 p. Ni, J.Q., A.J. Heber, T.T. Lim and C.A. Diehl. 1999a. Characteristics of hydrogen sulfide concentrations in mechanically ventilated swine buildings. In ASAE/CSAE-SCGR Annual International Meeting. Toronto, Ontario Canada, July Paper No ASAE, 2950 Niles Rd., St. Joseph, MI USA. 25 p. Ni, J.Q., A.J. Heber, T.T. Lim and C.A. Diehl. 1999b. Continuous measurement of hydrogen sulfide emission from two large swine finishing buildings. In ASAE/CSAE-SCGR Annual International Meeting. Toronto, Ontario Canada, July Paper No ASAE, 2950 Niles Rd., St. Joseph, MI USA. 17 p. 12

13 Ni, J.Q., A.J. Heber, C.A. Diehl and T.T. Lim. 2000a. Ammonia, hydrogen sulphide and carbon dioxide from pig manure in under-floor deep pits. Journal of Agricultural Engineering Research, In press. Ni, J.Q., A.J. Heber, C.A. Diehl, T.T. Lim, R.K. Duggirala and B.L. Haymore. 2000b. Burst releases of hydrogen sulfide in mechanically ventilated swine buildings. In Conference Proceedings Odors and VOC Emissions Cession 8-c. Cincinnati, Ohio, USA, April Water Environment Federation. 11 p. Osbern, L.N. and R.O. Crapo Dung lung: a report of toxic exposure to liquid manure. Annals of Internal Medicine 95(3): Patni, N.K. and S.P. Clarke Transient hazardous conditions in animal buildings due to manure gas released during slurry mixing. Applied Engineering in Agriculture 7(4): USEPA National Air Quality and Emissions Trends Report, Office of Air Quality Planning and Standards, United States Environmental Protection Agency, Research Triangle Park, NC EPA 454/R March. 221 p. Zhu, J., L.D. Jacobson, D.R. Schmidt and R.E. Nicolai Daylong variations in odor and gas emissions from animal facilities. Applied Engineering in Agriculture 16(2):