INTRODUCTION

Gas, odor, and particulate concentrations and emissions have been, and will continue to be, targeted components of livestock and poultry production systems. Local units of government (counties and townships) have or are considering the establishment of setback requirements from rural residences and livestock operations to prevent odor and other nuisance complaints. State and federal regulatory agencies have begun to enforce existing or enact new air quality standards that are being addressed during the permitting process. In addition, the environment established by the ventilation system has a direct influence on worker and animal health.

Airborne contaminants present inside animal buildings are in general difficult and expensive to measure continuously. For these reasons, relatively few studies have reported on continuous ammonia (NH3), hydrogen sulfide (H2S), and particulates (especially PM10) inside animal buildings. Many studies exist that have reported on discontinuous gas and particulate concentrations, and while beneficial, do not describe the true environment that animals and workers are exposed to on a daily and long-term basis. Bicudo et al. (2002) and Hoff et al. (2002) provided reviews regarding gas and particulate concentrations in pig barns and reported wide variations in all concentrations due to seasonal, diurnal, maturity level, and other factors.

State and federal regulators have begun to examine particulate matter (PM) emissions from animal production systems. USEPA (1987) replaced the TSP standards with a PM10 standard (dust particles with a mass median diameter of 10 microns or less) to place more emphasis on relatively fine, rather than coarse, dust particles to provide greater human health protection and to limit the amount actually emitted to the atmosphere (Sweeten et al., 2000).

The ambient primary and secondary PM10 standards are a 24-hour average value of 150 μg/m3 with no more than one exceedance allowed per year (USEPA, 1987). The major objective of the project summarized in this paper was to quantify long-term (yearly) air pollutant concentrations and emissions from confined animal buildings and establish methodologies for real time measurement of these emissions and build a valid database of air emissions for U.S. animal facilities. The focus of this paper is to summarize the results collected from a deep-pit pig grow-finish barn located in central Iowa USA and to relate these results to indoor air quality for humans and pigs.

EXPERIMENTAL METHODS

The results presented in this paper are a subset of a six-state collaborative effort conducted in the USA between 2002 and 2004. The goal of the study was a 15-month sampling period assuring that long-term inside barn concentrations (and subsequent emissions) could be fully characterized allowing the recording of variations in inside barn concentrations due to seasonal effects, animal growth cycles, diurnal variations, and in-house manure storage levels.

A Mobile Emission Laboratory (MEL) was developed for this research and positioned between two similar, mechanically-ventilated, grow-finish pig barns. MEL housed a gas sampling system (GSS), gas analyzers, environmental instrumentation, a computer, the data acquisition system, and all required calibration gas cylinders. Gas concentrations (Heber et al., 2002b) were measured at the air inlets and outlets of each building. PM10 was measured continuously using a Tapered Element Oscillating Microbalance (TEOM). The specific gas and PM instrumentation included the following:

NH3 - a chemiluminescence NH3 analyzer, Model 17C, Thermal Environmental Instruments (TEI), Franklin, MA
H2S - a pulsed fluorescence SO2 detector, Model 45C, Thermal Environmental Instruments (TEI), Franklin, MA
CO2 – two photoacoustic infrared CO2 analyzers (2,000-ppm & 10,000-ppm), Model 3600, Mine Safety Appliances (MSA), Co., Pittsburg, PA
PM10 – two “tapered element oscillating microbalances” or TEOM ambient PM10 monitors, Model 1400a, Rupprecht & Patashnick, Albany, NY

Two “identical in design” pig grow-finish barns located in central Iowa were monitored. These barns are characterized as deep-pit barns where manure produced in one year is stored below the occupied zone of the pigs in a 2.4 m deep holding tank below the occupied zone of the pigs. Once a year, usually late October, the manure pits are emptied with the manure injected into nearby cropland as a fertilizer. The two barns monitored were part of a 4-building site. The two center barns were monitored for this study in an attempt to equally distribute wind effects caused by adjacent barns. One of the two barns monitored is shown in detail in figure 1.

A summary of each of two barns monitored:

Livestock Type: Pig grow-finisher, reared from ~20 and 120 kg.
Capacity: 960 pigs per barn.
Manure Storage: 2.4 m deep-pit below barn floor; 365 day capacity.
Building Dimensions: 13 m wide, 59 m long, 2.4 m sidewall height.
Ventilation Type: Full mechanical, combined ceiling diffusers and tunnel ventilation.
Feeder Type: Wet-dry.
Gas sample Lines: 12 total, 6 per barn.

Data was collected at 1 minute intervals for the duration of the study in a quasicontinuous method by switching gas sample lines sequentially in 10 minute sample sequences using a series of 3-way solenoid valves. All gas sample lines not being sampled were still allowed to sample with the sample air diverted to atmosphere to allow for a valid sample to be present at the analyzers when called for. The sampling sequence allowed for concentrations to be measured every 120 minutes at each of the sample location shown in figure 1. For each 10 minute analysis period per sample location, the first 7 minutes was discarded allowing the analyzers to reach steady-state, leaving the final 3 minute average to represent the gas concentration at that location for that particular 120 minute sequence.

RESULTS AND DISCUSSION

This paper presents the daily average inside barn concentrations for NH3, H2S, CO2, and PM10 for the barn highlighted in figure 1. Nineteen months of data were collected between October 2002 and April 2004. The data summarized for this paper includes the daily mean and maximums for February 2003 through April 2004 which encompasses three complete production cycles as shown in figure 2a. Airflow and inside temperature control during the study period is shown in figure 2b. The daily mean and maximum NH3, H2S, CO2, and PM10 concentrations for the study period are shown in figures 3 to 6, respectively. A general review of the concentrations given in figures 3 to 6 indicate a great deal of variability for each of the variables monitored. This variability was expected due to the extreme outdoor temperature ranges experienced (figure 2a) combined with the ventilation rate changes required to achieve interior climate control (figure 2b). Additionally, the barns monitored experienced three production cycles of pigs (figure 2a) that also varied in placement time relative to climate.

Inside Barn Ammonia Concentration

Daily ammonia concentration averaged 17.6±12.1 ppm with a maximum daily mean concentration of 49.8 ppm (figure 3). The maximum measured ammonia concentration (i.e., for any individual sample event) averaged 24.2±14.6 ppm with a maximum of 59.7 ppm. Ammonia emission (not plotted) averaged 50.2±21.3 g/d-AU or on a per pig basis of 7.15±3.80 g/d-pig.

Inside Barn Hydrogen Sulfide Concentration

Daily hydrogen sulfide concentration averaged 361±209 ppb with a maximum daily mean concentration of 1290 ppb (figure 4). The maximum measured hydrogen sulfide concentration (i.e., for any individual sample event) averaged 588±616 ppb with a maximum of 14200 ppb. Hydrogen sulfide emission (not plotted) averaged 2.69±2.46 g/d-AU or on a per pig basis of 0.40±0.46 g/d-pig. One specific period resulted in significantly higher concentrations compared to the rest of the monitored period. This period, shown in October 2003, was the result of emptying manure from the deep-pit storage beneath the building. During this removal event, the average daily hydrogen sulfide emission was 3.85 kg/d. This level represents roughly 10 times the average daily emission levels otherwise measured. Details of these pump-out events can be found in Hoff et al. (2004).

Inside Barn Carbon Dioxide Concentration

Daily carbon dioxide concentration averaged 2572±1666 ppm with a maximum daily mean concentration of 6390 ppm (figure 5). The maximum measured carbon dioxide concentration (i.e., for any individual sample event) averaged 3343±1884 ppm with a maximum of 7710 ppm. Carbon dioxide emission averaged 12039±6983 g/d-AU or on a per pig basis of 1.56±0.65 kg/d-pig.

Inside Barn PM10 Concentration

Daily PM10 concentration averaged 248±202 μg m-3 with a maximum daily mean concentration of 1090 μg m-3 (figure 6). The maximum measured PM10 concentration (i.e., for any individual sample event) averaged 895±792 μg m-3 with a maximum of 4060 μg m-3. PM10 emission averaged 0.79±0.59 g/d-AU or on a per pig basis averaged 0.12±0.11 g/d-pig. For this particular production site, ownership had changed hands before the third production cycle and under new ownership the level of fat added to the diet was significantly decreased. The reduction in added fat resulted in the elevated PM10 concentrations as shown in figure 6.

CONCENTRATIONS RELATIVE TO OCCUPATIONAL STANDARDS

The long-term nature of this study allowed for an analysis of the interior climate relative to indoor air quality. Two basic standards exist intended to protect human health; ambient and occupational. Ambient standards are designed to protect the general public and are set at levels to protect sensitive populations such as small children, the elderly, and asthmatics. Occupational standards are established to protect those individuals who selfselect to work in environments that might not be suitable for those sensitive to low levels of air entrained gases and particulates. Occupational standards are set at significantly higher levels for any gas or class of particulates due to the self-selection characteristics of occupational settings. Table 1 summarizes the ambient and occupational standards established in the USA for common air entrained pollutants found in pig production settings. These standards are similar in other parts of the world.

Ambient versus occupational standards differ greatly as a consequence of the protective safety factors required for sensitive populations. The results presented in this paper will be compared against both the ambient and occupational standards given. The results from this study indicated that the daily average ammonia, hydrogen sulfide, carbon dioxide, and PM10 concentrations were all below occupational standards as set in the USA by either OSHA or ACGIH. Ammonia, with a daily average of 17.6±12.1 ppm, was below the 50 ppm and 25 ppm TWA levels set by OSHA and ACGIH, respectively. The one-time daily maximum measured over the course of this study was 59.7 ppm which is above the STEL for ammonia as established by ACGIH; however, the 59.7 ppm one-time maximum does not have an associated duration making judgement difficult. Hydrogen sulfide daily mean concentrations were all an order of magnitude below occupational guidelines, except during the pit pumping event where the interior climate hydrogen sulfide level reached 14.2 ppm. Carbon dioxide daily mean concentration was 2572±1666 ppm, roughly half the TWA limit established by OSHA. Daily PM10 concentration averaged 248±202 μg m-3 with a maximum daily mean concentration of 1090 μg m-3 both well below the OSHA established TWA limit of 5000 μg m-3.

The one-time overall maximum reading for PM10 was 4060 μg m-3, nearing the concentration limit established by OSHA but for a duration well below the TWA. Donham et al. (2002) recommended that pig farm workers should be limited to 8 hour time weighted averages (TWA) of 230 μg m-3 for PM10, 7 ppm for ammonia, and 1540 ppm for carbon dioxide; all significant reductions from regulated occupational standards and all levels that were not met in the barns monitored for this study.

SUMMARY AND CONCLUSIONS

Ammonia (NH3), hydrogen sulfide (H2S), carbon dioxide (CO2), and particulate matter (PM10) monitoring from two Iowa USA deep-pit grow-finish pig barns was conducted between October 2002 and April 2004. For the three complete production cycles between February 2003 and April 2004, the results indicated that the daily ammonia concentration averaged 17.6±12.1 ppm with a maximum daily mean concentration of 49.8 ppm and an overall one-time maximum of 59.7 ppm. Daily hydrogen sulfide concentration averaged 361±209 ppb with a maximum daily mean concentration of 1290 ppb and an overall one-time maximum of 14200 ppb that occurred during manure agitation and removal. Daily PM10 concentration averaged 248±202 μg m-3 with a maximum daily mean concentration of 1090 μg m-3 and an overall one-time maximum of 4060 μg m-3. PM10 concentration inside the barn significantly increased when fat in the diet was reduced. Indoor air quality levels associated with ammonia, hydrogen sulfide, carbon dioxide, and PM10 were below regulated levels based on enforced occupational standards but above those recommended by Donham et al. (2002).

ACKNOWLEDGEMENTS

The author would like to thank the United States Department of Agriculture for funding this research project under the USDA-IFAFS research and demonstration program.

Presented at the Congreso de Producción Porcina in Resistencia, Argentina, 2016.

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