2006 Poultry Science Association, Inc.
Improving In-House Air Quality in Broiler Production Facilities Using an Electrostatic Space Charge System C. W. Ritz,*1 B. W. Mitchell,† B. D. Fairchild,‡ M. Czarick III,§ and J. W. Worley§ *Department of Poultry Science, University of Georgia, Calhoun 30701; †Southeast Poultry Research Laboratory, USDA-Agricultural Research Service, Athens, Georgia 30605; and ‡Department of Poultry Science, and §Department of Biological and Agricultural Engineering, University of Georgia, Athens 30602
Primary Audience: Broiler Production Managers, Poultry Producers, Researchers SUMMARY Reduction of airborne dust in enclosed animal housing has been shown to result in corresponding reductions in airborne bacteria, ammonia, and odor. The search for strategies to reduce particulate matter and ammonia emissions from animal housing has led to considerable interest in the poultry industry for practical systems to reduce these air emissions. Technologies that have been shown to be effective for reducing airborne dust in animal areas include misting with an oil spray, water mists, extra ventilation, and electrostatic space charge systems. An electrostatic space charge system (ESCS) was designed to reduce airborne dust and ammonia emissions from a commercial broiler production house. The ESCS for this application was based on patented technology developed to reduce airborne dust and pathogens. Two commercial broiler houses with built-up litter (a control house and one outfitted with an ESCS unit) were monitored for dust and ammonia concentrations over a period of 7 flocks. Results of this study indicate the ESCS significantly reduced airborne dust by an average of 43% and reduced ammonia by an average of 13%. Power consumption of the ESCS system was less than 100 W when in operation. Commercial application of this technology within the production house has the potential to improve in-house air quality and reduce particulate emissions. Key words: electrostatic, ionization, poultry, dust, ammonia 2006 J. Appl. Poult. Res. 15:333–340
DESCRIPTION OF PROBLEM Air quality relating to poultry production housing has been a major concern for years, particularly with regard to poultry health. Environmental concerns and nuisance issues related to poultry house air emissions are now issues affecting the poultry industry. Of specific concern are ammonia, particulate matter, and odor. Although 1
Corresponding author:
[email protected].
there is considerable research directed at defining the problem and scope of emissions, it is equally important that practical and economical control measures be examined. Dust concentrations in poultry houses have been reported to vary from 0.02 to 81.33 mg/m3 for inhalable dust and from 0.01 to 6.5 mg/m3for respirable dust [1]. Sources of dust in broiler
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Figure 1. Electrostatic space charge system (ESCS) inline ionization units hanging from the ceiling of the treatment house (TH). Four units, 2 in the brood end and 2 in the growout end, were hung on either side from the center of the house.
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Table 1. Efficiency of electrostatic space charge system (ESCS) for reduction of broiler house dust and ammonia concentrations1 Dust concentration mean (mg/m3) Flock 1 2 3 4 5 6 7 Mean ± SEM
NH3 concentration mean (ppm)
Period
CH
TH
Reduction (%)
CH
TH
Reduction (%)
Aug-Sept Oct-Nov Nov-Dec Jan-Feb Mar-Apr May-Jun Jun-Jul
0.47 0.63 1.10 1.13 0.48 0.14 0.49 0.63 ± 0.030
0.23 0.38 0.44 0.60 0.27 0.09 0.36 0.34 ± 0.014
51.1 39.7 60.0 46.9 43.7 35.7 26.5 43.4 ± 0.913
12 31 51 44 54 24 20 34 ± 1.369
11 27 47 38 46 19 17 29 2± 1.187
8.3 12.9 7.8 13.6 14.8 20.8 15.0 13.3 ± 4.086
CH = control house; TH = treatment house.
1
houses include feed, down feathers, excrement, microorganisms, and crystalline urine [2]. There are several factors that affect dust levels in poultry houses, including animal activity, animal density, and moisture conditions [1]. Dust can contain large numbers of microorganisms that could have potential effect on human and bird health. Several studies have focused on dust levels in various animal housing and characterization of the dust
components, which include microorganisms, endotoxins [3], and odors [4, 5]. Several approaches can be used to reduce dust concentration in animal housing areas. These include adding fat to feed, fogging with water, fogging with an oil-based spray, ionization, electrostatic filtration, vacuum cleaning, filtration and recirculation, cleaning with wet scrubbers, purge ventilation, deep litter, and optimization of air
Figure 2. Data profile showing dust concentration comparison between the treatment house (TH) and control house (CH) during brooding. Data are displayed as a 30-period moving average.
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Figure 3. Data profile showing ammonia concentration comparison between the treatment house (TH) and control house (CH) during brooding. Data are displayed as a 30-period moving average.
inlet position. Reductions reported with these approaches have ranged from 15% for weekly washing of pigs and floors, 23% with ionizers, to 76% with a rapeseed oil spray [6]. Other reports of ionizer efficiency have ranged from 31% [7] and 67% [8] to 92% [9]. Furthermore, studies have shown that reducing airborne dust levels by 50% can reduce airborne bacteria by 100-fold or more [10, 11]. Ammonia in broiler houses, like much of the dust, originates from the litter base. Litter type, management, humidity, pH, and temperature affect the ammonia concentration and release [10, 12, 13]. High moisture levels in the air facilitate the absorption of ammonia onto dust particles, and the inhalation of the dust particles containing ammonia can cause damage to the respiratory tract [14]. For broiler house ammonia, reduction of aerial concentrations has been largely accomplished through ventilation. However, as fuel costs increase particularly during the winter months, poultry growers tend to reduce ventilation to minimize heating costs. Another trend is less
frequent complete house clean-out, resulting in birds being grown on built-up litter with the cake removed and the remaining litter top dressed with new bedding material. The combination of these trends can be detrimental to air quality in broiler houses if dust and ammonia levels are not managed, particularly during the brooding phase. The electrostatic space charge system (ESCS) described by Mitchell and Stone [15] has been shown to significantly improve air quality by reducing airborne pathogens and disease transmission in poultry. The principle behind the ESCS is to transfer a strong negative electrostatic charge to airborne dust particles within an enclosed space. The negatively charged particles will then precipitate out of the air as they are attracted to grounded surfaces. Nitrogen compounds attached to the dust should also precipitate out of the air. In broiler breeder studies completed within a controlled research facility, ESCS technology has shown reductions in airborne pathogens and birdto-bird or bird-to-egg transmission by reducing airborne dust, ammonia, and total aerobic bacteria
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Figure 4. Data profile showing temperature and relative humidity comparisons between the treatment house and control house during brooding. Data are displayed as a 30-period moving average.
by averages of 60, 56, and 76%, respectively [16, 17, 18]. Airborne Salmonella enteritidis (SE) experiments conducted in controlled environment transmission cabinets with and without an ESCS showed that chicks exposed to a naturally generated aerosol of SE beginning at 1 d of age had no cecal contamination 8 d later [19, 20]. Experiments conducted in a 15 × 22 ft (330 ft2) isolation room with SE-infected caged layers showed reductions of airborne SE of approximately 95% over a test period of 10 d when the room was treated with the ESCS [21]. Electrostatic fields have not been shown to produce adverse health effects in animals or humans [22, 23]. Evaluation of an ESCS for reducing dust and ammonia concentrations on a commercial broiler production scale has not been attempted. The primary goals of this research were to determine whether a practical ESCS could be developed and operated in a commercial broiler production house and to evaluate the effectiveness of this technology for improving air quality in the house through reductions in emissions of dust and ammonia.
MATERIALS AND METHODS A custom-made ESCS system was designed and installed in a 500 ft × 40 ft tunnel ventilated
commercial broiler house with drop ceiling. The treatment house (TH) system consisted of 4 rows of inline, negative air ionization units with two 200-ft rows on each side of the house in the brood end and two 200-ft rows in the growout end, as shown in Figure 1. Separate high-voltage (−30 kV DC, 2 mA) power supplies were used to supply −25 kV DC to the ion generators in each half of the house. The high-voltage power supply for the ESCS was limited to a safe level of 2 mA. The inline generators consisted of a conductive tube with sharp pointed electrodes at 1-in. intervals and pointing downward. The tubing was attached to a grounded 1-in. diameter black iron pipe with Teflon insulators at 2-ft intervals (Figure 1). The iron pipe was located 3 in. above the discharge points to provide a close proximity ground plane and to increase the negative ion output [15]. The inline generators were centered between the first row of water lines and the feeders such that they were about 12 ft from the sidewalls. The inline generators were installed on each end of the house such that they were centered between the center curtain (used for half-house brooding) and the evaporative cooling pads on one end and between the center curtain and the tunnel ventilating fans on the other end. Winches were used to
338 raise the ESCS to a height of 7 ft above the litter (sufficiently high to walk under, but as low as possible to concentrate the charge near the birds where dust is being generated). A broiler house adjacent and essentially identical to the treatment house was instrumented for airborne dust and ammonia monitoring but operated as the control house (CH) without ionization. The treatment and control houses were operated simultaneously. Both houses were stocked at a density of 0.7 ft3/ bird. Each house was initially bedded with pine shavings, and the caked litter material around the feeders and drinkers was removed between each flock and followed by a thin top dressing of new shavings. No change in bird strain or age at processing occurred throughout the study period. Dust and ammonia concentrations and temperature and relative humidity readings were each measured at 2 sites within the house and approximately 4 ft above the litter in the center of the house. During the brooding period, measurements were made in the center of the brooding section, 100 ft from the end wall. After brooding, when birds occupied the entire house, measurements were made in the center of the growout end of the house 20 ft in front of the tunnel fans. Dust concentrations were measured with a TSI DustTrak [24], a laser-based instrument with a range of 0.001 to 100 mg/m3. Aerial ammonia was measured with a Draeger Polytron I [25] electrochemical sensor with a sensitivity range of 0 to 100 ppm. The ammonia sensors were calibrated with 50 ppm calibration gas prior to each sampling period and kept within a protective enclosure during use. Data were collected for 3 sampling periods during each of 7 flocks, during the first, third, and fifth weeks of production. Air samples were collected continuously for approximately 5 d during each period. Sampling frequency was once every 15 min for dust and every 1 min for ammonia. Mean dust and ammonia concentrations were calculated for each sampling period. Due to the large amount of collected data during each sampling period, hourly means were generated to calculate the sampling period mean. The 3 samplingperiod means were then used to generate a flock mean concentration for dust and ammonia. Temperature and relative humidity were recorded at 1-min intervals with Hobo data loggers [26]. The houses were set up to be as identical as possible, and special efforts were made to as-
JAPR: Field Report sure that treatment and control houses were operated at the same temperature and ventilation rate. A computer located at the farm was connected to the house controller system and recorded fan run time along with in-house relative humidity and temperature. Bird performance (body weights and feed efficiencies), immune response, and microbial load of the house were not evaluated in this study. Due to the large volume of data collected during sampling, data are expressed as simple 30period moving averages within the accompanying figures.
RESULTS AND DISCUSSION Table 1 contains the mean dust and ammonia concentrations and reduction efficiencies for aerial dust and ammonia within a broiler production house for each of the 7 consecutive flocks. The results of this study show that the use of the ESCS produced an overall airborne dust reduction of 43% in the commercial broiler house. Aerial dust concentrations within the broiler houses were low and ranged from 0.2 to 1.9 mg/m3. Charged dust could often be seen extending from the grounded water and feeder support cables in the treatment house. Besides reducing airborne dust, the ESCS likely inhibited aerosolization of dust by keeping surface dust near its source due to the negative space charge. Loose dust on the floor of a treated area will tend not to become airborne because as soon as it leaves the floor it would be charged and re-attracted to the floor. Long-term exposure to airborne dust and pathogens in poultry houses is associated with chronic respiratory problems for workers [27, 28]; therefore, an additional benefit of reducing airborne dust and pathogens in poultry houses would be the improvement of air quality for workers. Ammonia levels in the study houses ranged from an average of 11 to 54 ppm with concentrations reduced by 13% with the ESCS (Table 1). This reduction of ammonia is much lower than the 56% average reduction obtained in a breeder pen study by Mitchell et al. [17]. However, the breeder study was conducted within an enclosed small-scale research setting where ammonia concentrations were much lower than in the present broiler study. The variability of the conditions and control of the environment in the research rooms compared with the commercial setting likely contributed to ammonia concentration vari-
RITZ ET AL: BROLER HOUSE AIR QUALITY ability between the 2 studies. Reduction in aerial ammonia levels within the treatment house primarily occurred during the evening hours when ammonia concentrations were highest and ventilation rates were lowest. Examples of recorded data profiles of dust and ammonia concentrations for the fifth flock (March 2003) during the third week of the brooding period are shown in Figures 2 and 3. Aerial dust levels in TH were consistently lower than in CH (Figure 2). Peak dust levels in CH in the latter part of the period were noticeably higher than those in TH. Temperature and humidity measurements in the 2 houses over the same sampling period are shown in Figure 4, depicting that very little variation occurred in house operations over the sampling period. Although it is known that some ammonia and odors are sorbed to poultry house dust, it is not known what percentage of total ammonia production the sorbed fraction represents. Previous studies indicate that a significant portion of airborne ammonia in animal rearing facilities is associated with dust particles [29, 30]. An assumption in the present study was that reduction of airborne dust by the ESCS would result in a similar reduction in airborne ammonia, based on previous work with broiler breeders [17]. In the present study with built-up litter over a period of 1 yr, the ESCS did not appreciably reduce ammonia concentrations. The reasons for this discrepancy are not clear. It is likely that the amount of gaseous ammonia is much greater compared with that which is sorbed onto the dust, resulting in less opportunity for overall ammonia reduction by a dustreduction system. It should be noted that the ammonia levels in the present study were 2 to 3 times higher, whereas the dust levels were 2 to 3 times lower than in the study reported by Mitchell et al. [17], which may explain the lower ammonia removal effectiveness of the ESCS in the present study.
339 No differences in bird activity were observed in the form of decreased water consumption or increased mortality, and no adverse effects of the continuous charge were observed in the form of stray voltage or static discharge at the feeder and water lines. The incidences of static discharge to workers were minimal. The intensity of a discharge from direct contact with an ESCS ionizer was similar to touching a spark plug wire on a gasoline engine. Dust collection on the ESCS and the subsequent need for cleaning was not a major issue. Brushing the dust from the equipment every 7 to 10 d was sufficient to maintain desired high charge levels from each unit. Telescoping brushes were used to clean the ESCS after the power was shut off to the unit. Cleaning time of the prototype system was about 1 h. Maintenance of the system during the study period was minimal. The cost of materials and installation of the experimental ESCS unit was approximately $4,000. Power consumption of the entire system was less than 100 W during operation. It is reasonable to assume that a commercially available product would have a reduced capital outlay and quicker return on investment than the experimental prototype used in this study. Although not documented in this study, high ventilation rates may cause resuspension of dust particles prior to expulsion from the house. A potential application of the ESCS technology would be to concentrate exhaust air within close proximity of an ESCS unit compared with units suspended within a poultry house as in the present study. This technology may facilitate higher charges on dust particles and with potentially much greater removal of dust and ammonia from the exhaust air than can be obtained within the house. Additional rows of inline chargers or higher voltage levels may also improve dust removal. Such schemes using the ESCS technology merit further evaluation.
CONCLUSIONS AND APPLICATIONS 1. Broiler house airborne dust concentrations were reduced with the use of an ESCS. The effectiveness of the system was increased with higher dust concentrations. 2. Ammonia levels in broiler houses with average dust concentrations less than 1 mg/m3 did not appear to be affected by an ESCS. Seasonal differences in ammonia concentration were observed.
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3 Reduction of ammonia concentrations inside poultry houses may require separate control strategies than those designed for dust reduction to ameliorate poor air quality and emissions attributed to ammonia. 4. Further investigation is needed to determine the commercial economic feasibility of the system based on potential improvements in bird performance and airborne microbial reduction.
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Acknowledgments
16. Richardson, L. J., B. W. Mitchell, J. L. Wilson, and C. L. Hofacre. 2003. Effect of an electrostatic space system on airborne dust
This work was made possible by support from the US Poultry and Egg Association.
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