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Characterization of gaseous pollutant and particulate matter emission rates from a commercial broiler operation part I: Observed trends in emissions
Atmospheric Environment 44 (2010) 3770e3777
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Characterization of gaseous pollutant and particulate matter emission rates from a commercial broiler operation part I: Observed trends in emissions Taylor S. Roumeliotis, Brad J. Dixon, Bill J. Van Heyst* School of Engineering, University of Guelph, 50 Stone Rd. Guelph, Ontario N1G 2W1, Canada
a r t i c l e i n f o
a b s t r a c t
Article history: Received 21 January 2010 Received in revised form 25 June 2010 Accepted 28 June 2010
This paper characterizes the emission rates of size fractionated particulate matter, inorganic aerosols, acid gases, ammonia and methane measured over four flocks at a commercial broiler chicken facility. Mean emission rates of each pollutant, along with sampling notes, were reported in this paper, the first in a series of two. Sampling notes were needed because inherent gaps in data may bias the mean emission rates. The mean emission rates of PM10 and PM2.5 were 5.0 and 0.78 g day1 [Animal Unit, AU]1, respectively, while inorganic aerosols mean emission rates ranged from 0.15 to 0.46 g day1 AU1 depending on the season. The average total acid gas emission rate was 0.43 g day1 AU1 with the greatest contribution from nitrous and nitric acids and little contribution from sulfuric acid (as SO2). Ammonia emissions were seasonally dependent, with a mean emission rate of 66.0 g day1 AU1 in the cooler seasons and 94.5 g day1 AU1 during the warmer seasons. Methane emissions were relatively consistent with a mean emission rate of 208 g day1 AU1. The diurnal pattern in each pollutant’s emission rate was relatively consistent after normalizing the hourly emissions according to each daily mean emission rate. Over the duration of a production cycle, all the measured pollutants’ emissions increased proportionally to the total live mass of birds in the house, with the exception of ammonia. Interrelationships between pollutants provide evidence of mutually dependent release mechanisms, which suggests that it may be possible to fill data gaps with minimal data requirements. In the second paper (Roumeliotis, T.S., Dixon, B.J., Van Heyst, B.J. Characterization of gaseous pollutants and particulate matter emission rates from a commercial broiler operation part II: correlated emission rates. Atmospheric Environment, 2010.), regression correlations are developed to estimate daily mean emission rates for data gaps and, using the normalized hourly diurnal patterns from this paper, emission factors were generated for each pollutant. Ó 2010 Elsevier Ltd. All rights reserved.
Keywords: Acid gases Ammonia Methane Inorganic aerosols Particulate matter Emission rates Broiler chickens Diurnal pattern
1. Introduction Commercial poultry facilities are responsible for emitting a variety of pollutants. Of these pollutants, ammonia (NH3) and particulate matter less than or equal to ten and 2.5 microns in diameter (PM10 and PM2.5, respectively) have been focused on due to their detrimental effects on human health and the environment and abundance inside the poultry houses (Lacey et al., 2003; Phillips et al., 1995; Roumeliotis and Van Heyst, 2008; Wheeler et al., 2006). In Canada, 87% of the NH3 emissions are attributed to agriculture and 82% of these emissions have been estimated to originate from primary livestock production (Kurvits and Marta, 1998). Ammonia is the most prevalent alkaline gas in the atmosphere and associates with acidic gases to neutralize the pH. This * Corresponding author. Tel.: þ1 519 824 4120x53665; fax: þ1 519 836 0227. E-mail address: [email protected] (B.J. Van Heyst). 1352-2310/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2010.06.052
neutralization process results in the formation of liquid and solid inorganic aerosols, typically in the PM2.5 size fraction. Sulfuric, nitric, and hydrochloric acid are the three main acidic species that interact with NH3 to form ammonium sulfate, ammonium bisulfate, ammonium nitrate and ammonium chloride, respectively (Anderson et al., 2003; Baek et al., 2004). As poultry houses experience elevated levels of ammonia, it may be possible that any acid gases present in the barn atmosphere will be neutralized prior to being emitted from the facility and contribute to the overall PM2.5 burden. Another gaseous pollutant of concern is methane (CH4) but it has not been well characterized for poultry operations since, unlike ruminants, poultry do not generate large quantities of CH4 in their digestive tract. Methane, however, can be generated from the anaerobic decomposition of the organic matter in the litter. The objective of this paper was to quantify the emissions of PM10, PM2.5, inorganic aerosols in the PM2.5 size fractionation, acid gases, ammonia, and methane from a commercial broiler chicken
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facility using discrete and continuous measurement techniques. Emission trends need to be characterized, both diurnally and seasonally, to be able to interpret any data gaps due to instrument calibration and failures. Influential house management and/or environmental factors that affect one or more of the pollutants also need to be considered in any data interpolation method. This paper, the first in a series of two, focuses on characterizing the emissions of numerous pollutants from a broiler facility over four production flocks. The second paper develops correlations needed to address the missing data gaps and provides estimates of total emissions (Roumeliotis et al., 2010). 2. Materials and methods The commercial broiler chicken facility used in the current study was a single storey (150.5 m by 18.3 m), mechanically cross-ventilated house located just outside of Guelph, Ontario, Canada. The house used a litter floor with new bedding, either wheat straw or wood shavings, placed at the beginning of each bird production cycle. Feed was auger-fed to the birds through rows of troughs and water was delivered via nipple drinkers. The house temperature and relative humidity were controlled using radiant pipe heaters and a staged ventilation program. Heaters were used for roughly the first ten days to maintain a temperature that gradually decreased from 34 to 27 C. After this time, fans were used to provide air exchanges in order to continually decrease the temperature from 26 to 19 C over the remainder of the production cycle. The facility used six variable speed fans (0.56 m diameter), 12 dual speed on/off fans (0.65 m diameter), and 10 single speed on/off fans (1.3 m diameter) for a total of 28 fans. Two lighting schedules of either 23 or 18 h of light each day were used at different stages in the production cycle to control the sleeping patterns of the chickens. The 23 hour day1 cycle was used for the first five to six days and again after 22e24 days until completion. The measurement campaign spanned four production flocks of broilers of approximately 45,000 broilers from February to September 2009. These four flocks of broilers were raised during representative seasons for the geographic region of winter, spring, summer, and summer/fall, respectively. During the four observed cycles, birds were raised from an average weight of 47 g to 1810 g over a period of 31e34 days. 2.1. Instrumentation Reactive gases (ammonia, hydrochloric acid, nitric acid, nitrous acid, and sulfuric acid (as sulfur dioxide)) and inorganic aerosol species (ammonium bound with chloride, nitrate, and sulfate) were collected from inside the broiler house using an annular denuder system (ADS; URG-3000C-ADS; URG Corporation, Chapel Hill, NC, USA). Samples were collected three times a week with each sampling period lasting approximately one hour. The ADS consisted of a 2.5 micron sharp cut-size cyclone followed by a series of nine, three-channel glass annular denuders used to adsorb the reactive gases by coating their walls with either 1% phosphorous acid or 1% sodium carbonate solutions. This was followed by a two-stage filter pack that collected the inorganic aerosols on a Teflon and nylon filter. Contents on both the annular denuders and filters were extracted following Winberry et al. (1999). All extracts were analyzed using an ion chromatography system (Dionex IC-2000 ICS; Dionex Corporation, Sunnyvale, CA, USA). The resulting cationic and anionic species were converted to their respective gaseous and particulate concentrations based on the extraction volume and the standardized air sample volume. Continuous PM10 and PM2.5 concentrations were measured using two DustTrakÒ aerosol monitors (Model 8520; TSI Incorporated,
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Shoreview, MN, USA) installed with 10 and 2.5 micron sharp cut-size inlet conditioners. Dust samples collected from the broiler house were used to adjust the calibration density of the DustTrak aerosol monitors. For the summer production cycle, ammonia was measured using a chemiluminescent ammonia analyzer (Model 17C, Thermo Electron Corporation, Franklin, MA, USA) while methane was measured continuously using a back-flush gas chromatography system coupled with a flame ionization detector (Model 55C, Thermo Electron Corporation, Franklin, MA, USA). Volumetric exhaust rates from the three different fan sizes were quantified using an AlnorÒ balometer kit (EBT721; Alnor Products, Shoreview, MN, USA) consisting of a capture hood and a 16 point velocity matrix connected to micromanometers. 2.2. Sampling procedures Air samples were drawn from the longitudinal midpoint of the barn through four horizontally integrated inlets, positioned inside the broiler house at a distance of 2.5 m from the exhaust fans and at a height of 1.8 m. This location produced representative pollutant concentrations in the exhaust air while avoiding a large change in velocity between the inlets and surrounding air (Heber and Bogan, 2006). The ADS and DustTrak monitors were located inside the facility while the Model 17C and 55C were situated in a climatecontrolled trailer located on the fresh air intake side of the facility. The house ventilation was managed by a 14 progressive stage, automated control system that records power used by the three fan sizes. The balometer was used to measure representative flow rates for the fans used in each of the 14 stages. The hourly averaged total house ventilation was, then, estimated using the individual exhaust rates with continuously monitored power usage by the facility’s ventilation. In addition, temperature, relative humidity and pressure were continuously measured both inside and outside the facility. Water consumption, average bird weight, and mortalities were recorded daily. Litter moisture, pH, ammonium-N, total ammoniacal nitrogen, and extractable chloride, were quantified every three to five days from composite litter samples and subsequent lab analysis. 2.3. Emission rate calculation Hourly averaged pollutant emission rates (E, g day1 AU1) were calculated on an animal unit (AU, equivalent to 500 kg live weight) basis using the number of birds and their average mass (M, kg), the hourly exhaust concentration (C, g m3), the outdoor concentration (Co, g m3), and the hourly total house ventilation rate (Q, m3 day1) as (Wheeler et al., 2006):
E ¼
ðC Co ÞQ 500 kg M AU
(1)
Since the outdoor air concentrations could not be measured simultaneously with the indoor air concentrations, a single daily averaged value for Co was estimated for each pollutant using a set of outdoor air measurements. The mean concentration (C o , g m3) from the outdoor set of measurements was adjusted using a statistical method designed to contain a specified proportion of the population with a specified confidence based on the standard deviation of the outdoor concentration measurements (S, g m3) and the uncertainty of the sample size, n, represented by the t-distribution with 95% coverage, t0.95,n1, as (McBean and Rovers, 1998):
Co ¼ C o þ t0:95;n1 S
(2)
If an exhaust concentration was quantified to be lower than Co, the emission rate was set to zero.
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3. Results and discussion Table 1 contains a summary of all the emissions quantified from the facility using both continuous and discrete measurement techniques. Each flock had incomplete continuous measurements (see sampling notes in Table 1) and a limited number of discrete measurements. 3.1. Particulate matter emissions As given in Table 1, the average PM10 and PM2.5 emission rate for the four flocks were 5.0 and 0.78 g day1 AU1, respectively. There was, however, significant variability in the PM10 and PM2.5 emissions on a diurnal basis as displayed in Fig. 1aed. On an hourly basis, the PM10 and PM2.5 emissions ranged from 0.22 to 60.48 g day1 AU1 and 0.08 to 7.34 g day1 AU1, respectively. In spite of the variations, the PM emissions, in units of g day1, generally increased exponentially over time similar to the increase in bird mass. Thus, the emission rates, on an AU basis, as given in Fig. 1, tended to remain relatively constant or even decreased at the tail end as a result of the exponential increase in the bird live weight. The dependence of PM emissions on bird mass is due to the increasing quantity of excreta produced, litter disturbed, feathers and dander shed and feed consumed and spilled as the bird grows (Dando et al., 2000). The spring and summer/fall flocks had less than 80% completeness. Data gaps in the spring flock occurred during the second and fifth week due to power failures, which may have caused the mean emission factor for PM10 of 6.1 g day1 AU1 to be inflated since the initial spike in the first week would have a relatively greater contribution to the mean emission. Conversely, the summer/fall flock is missing data for the first week, or the period with elevated emissions on an AU basis, which implies that the estimate for PM10 of 2.9 g day1 AU1 may be low. Aside from the third week of the summer/fall flock, the PM2.5 and PM10 behaved similarly as shown in Fig. 1 with the PM2.5 axis set to 1/10th of the PM10 axis. The average ratio of PM2.5 to PM10 for the winter and spring flocks was approximately 0.13 0.10 while for the summer and summer/fall flocks, the average ratio was approximately 0.20 0.13, which is statistically different from the winter/spring flocks. In comparison to literature values, the mean PM10 and PM2.5 emission rates were 14 and 36%, respectively, lower than the emission rate estimates from a 2006 measurement campaign at the same facility using different bird growth cycles (Roumeliotis and Van Heyst, 2007). Two studies with similar broiler facility design reported PM10 emission rate, Lacey et al. (2003) and Van Der Hoek (2007). The mean PM10 emission rate was lower than the average PM10 emission rate of 12.9 g day1 AU1 obtained from Lacey et al. (2003) but higher than 1.9 g day1 AU1 derived using emission data reported by Van Der Hoek (2007) (Roumeliotis and Van Heyst, 2008).
The prominent diurnal trend in PM10 and PM2.5 emissions depended greatly on the photoperiod or activity level of the birds. To illustrate this point, Fig. 2aed displays the average hourly ratios of the hourly emission rate to the daily average emission rate for the 18 hour day1 and 23 hour day1 lighting periods. The average standard deviation for each flock in Fig. 2 was 20% with the exception of PM2.5 under the 18 hour day1, which was slightly higher at 26%. The minimum and maximum normalized emission rates for PM10 and PM2.5 for each flock were statistically different using a two group comparison test (p-value was zero using three decimal place accuracy). The diurnal pattern for both the PM10 and PM2.5 ratio of average hourly to average daily emission rates with the 18 h of light were similar for all flocks. During the dark periods, the ratio of average hourly to average daily emission rates were 0.31 0.13 and 0.61 0.14 for PM10 and PM2.5, respectively, thus indicating that PM2.5 emissions may not have been as dependent on bird activity as the PM10 emissions. The reasons for this may include the relatively slower settling velocity of the smaller particulates as well as different generation mechanisms for the PM2.5 such as the formation of fine inorganic aerosols. During the hours of light, the PM10 emissions spiked between 06:00 and 08:00 when the lights were switched on. Although each flock displayed a unique behaviour during the hours of light, the overall trend was fairly constant with average normalized values of 1.22 0.16 and 1.13 0.11 for PM10 and PM2.5, respectively. When the 23 hour day1 lighting period was utilized, there was insufficient time to exhaust or settle the PM10 and PM2.5, which resulted in virtually no uniform diurnal pattern. One pattern that does emerge is the dependence on season. In the PM10 and PM2.5 plots, the winter and spring flocks’ ratio was greater than 1.0 during the daytime from approximately 08:00 until 23:00, whereas the summer and summer/fall flocks ratio was typically greater than 1.0 at night from approximately 20:00 until 08:00. The summer and summer/fall flocks’ diurnal pattern is the result of excessive indoor house temperatures (approaching 30 C) that could not be maintained in the ideal range due to the warm weather especially in the afternoon. To maintain optimal feed conversion ratios and normal weight gain, the indoor temperature should be gradually reduced from 22 C down to 19 C from day 22 to 34 (SCAHAW, 2000). As indoor temperatures in the afternoon exceed the comfort point, the birds reduced their activity levels and feeding to remain in the zone of thermoneutrality (SCAHAW, 2000). Thus these periods of elevated indoor temperatures during the two summer flocks resulted in reduced bird activity leading to lower PM emission rates measured in the later afternoon periods. For the winter and spring flocks, bird activity typically increased in the afternoon as the outdoor temperatures increased. As this lighting period is typical at the end of the cycle the reliance on the radiant pipe heaters is dramatically reduced from the start of the cycle.
Table 1 Summary of continuous and discrete emission measurements from four flocks of broilers. Sampling regularity
Pollutant emissions Flock (representative season) g day1 AU1
1 (winter)
Sampling notes 2 (spring)
Sampling notes 3 (summer)
Sampling notes 4 (summer/fall) Sampling notes
Continuous
PM10 PM2.5 Ammonia Methane
5.7 3.4 0.74 0.54 ND ND
96.9% complete 6.1 5.4 96.9% complete 0.85 0.73 e ND e ND
51.5% complete 5.3 3.0 51.5% complete 0.94 0.54 e 107.4 42.0 e 208.2 126.5
86.8% 86.8% 60.6% 57.0%
complete 2.9 1.5 complete 0.61 0.58 complete ND complete ND
72.4% complete 72.4% complete e e
Discrete Inorganic aerosols (w1 h Samples) Acid gases Ammonia
0.15 0.08 16 samples 0.40 0.39 9 samples 72.8 57.4 9 samples
0.24 0.23 16 samples 0.46 0.41 13 samples 84.3 56.9 13 samples
0.46 0.26 0.42 0.42 109.7 65.0
14 samples 14 samples 14 samples
0.45 0.23 0.42 0.22 123.9 76.4
10 samples 10 samples 10 samples
Adjusted
63.0 49.9 9 samples
69.0 46.6 13 samples
92.8 52.0
14 samples
101.8 62.0
10 samples
Ammonia
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Fig. 1. Emission rates on an animal unit basis (AU), equivalent to 500 kg live weight, for PM10 and PM2.5 during (a) winter, (b) spring, (c) summer, and (d) summer to fall production cycles.
Fig. 2. Ratio of the hourly emission rates to the daily mean emission rate for PM10 using (a) 18 hour and (b) 23 hour lighting periods and for PM2.5 using (c) 18 hour and (d) 23 hour lighting periods for all four broiler production cycles.
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3.2. Inorganic aerosol and acid gas emissions Fig. 3aed displays the inorganic aerosol emission rates on an AU basis according to each anionic species for the four production cycles, respectively. The winter and spring flocks (Flocks 1 and 2) resulted in lower overall inorganic aerosol emission rates than the summer and summer/fall flocks (Flocks 3 and 4) (see Table 1). Recalling that the PM2.5 to PM10 ratio for flocks 3 and 4 was approximately 50% greater than the first two flocks, it is reasonable to conclude that the inorganic aerosol formation contributed to the additional PM2.5 in these later flocks. The average ratio of inorganic aerosols (including chloride, sulfate, nitrate, associated with ammonium) to PM2.5 emissions was 26% for flocks 1 and 2 in contrast to 42% for flocks 3 and 4. The third and fourth flocks occurred during the warmer months with frequent inorganic aerosols emissions in excess of 400 mg day1 AU1. During the warmer months, there are two competing issues. The first is that the air retention time in the house decreases due to increased ventilation which should lower pollutant concentrations. The second issue is that the increased indoor temperature will allow the inorganic aerosol formation kinetics to progress at a faster rate. Based on the experimental measurements, the indoor temperature is responsible for a larger effect on the inorganic aerosol generation. Spikes in the inorganic aerosol emissions typically occurred simultaneously with spikes in the PM2.5 emissions. This is best illustrated in the summer/fall flock on days 18 and 20 where the spikes in inorganic aerosol emissions (hourly average emission > 600 mg day1 AU1) corresponded to the large spikes in PM2.5 emissions (see Fig. 1d). Of the individual inorganic aerosol species, the chloride-based aerosols were always the most abundant in all four flocks. The average proportion of chloride-based aerosols to total inorganic
aerosols over the four flocks was 90%. This is somewhat unexpected since ambient inorganic aerosols are dominated by the sulfate and nitrate species (Anderson et al., 2003). This points to a potential chloride source within the house. Emission rates of acid gases, one of the precursors required for inorganic aerosol formation, are given in Fig. 4aed for hydrochloric acid (HCl(g)), nitrous acid (HONO(g)), nitric acid (HNO3(g)) and sulfur dioxide (SO2(g)) respectively. Acid gas concentrations that were at or below the detection limit of the ion chromatograph or below their outdoor air concentration were not included in Fig. 4. Note that Fig. 4 is organized based on acid gas species rather than the bird cycle to facilitate comparison between the acid gases. From Fig. 4, it is apparent that very little sulfuric acid (as SO2) is emitted from the house for any flock implying that any SO2 in the house reacts quickly with ammonia. In addition, the HCl concentrations are consistently above ambient but its gaseous emission rate was comparatively low to its aerosol emission rate implying that most of the HCl is consumed in inorganic aerosol formations. For the nitrogen-based species, very little of the HONO and HNO3 acids react in spite of an excess of gaseous ammonia (see next section). These results suggest that the sulfate and chloride formation sequences are favoured over the nitrogen-based sequences. Concentrations of HCl, HONO and HNO3 were regularly above the mean ambient concentration, whereas SO2 concentrations were only above the mean ambient 14% of the time suggesting that there may be a source inside the house for HCl, HONO and HNO3. The near constant behaviour of HCl emissions on an AU basis suggests that the HCl is increasing exponentially at a rate similar to the exponential increase in bird mass and thus its source is related to the bird growth. For the case of HONO, the decreasing emission rate on an AU basis implies an independence from the bird mass and
Fig. 3. Emission rates on an AU basis for three inorganic aerosol species during (a) winter, (b) spring, (c) summer, and (d) summer to fall production cycles.
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Fig. 4. Emission rates on an AU basis for acidic gases including (a) hydrochloric acid, (b) nitrous acid, (c) sulfur dioxide, and (d) nitric acid for four production cycles.
thus any in house source would need to be independent of the bird production. For HNO3, no distinct relationship with bird mass can be discerned. 3.3. Ammonia and methane emissions Ammonia and methane are discussed jointly since their generation mechanisms should be similar due to both being formed from the microbial breakdown of nutrients found in excreta. The discrete ammonia measurements given in Table 1 indicate a seasonal variation with greater emissions during the warmer months. Continuous measurements of ammonia and methane were conducted simultaneously with the ADS ammonia measurements for the last 21 days of flock 3 (summer) with the results shown in Fig. 5. For ammonia, the emission factors estimated based on the discrete and continuous measurements are consistent, however, the hourly fluctuations in NH3 emissions can be significant and that the ADS discrete measurements cannot capture diurnal trends. For methane, no other data exists to compare with the continuous data. Using the continuous data from flock 3, the average of the hourly ratios of NH3 and CH4 hourly average to daily average emission rates are displayed in Fig. 6, similarly to Fig. 2 for PM. The error bars on the data in Fig. 6 represent one standard deviation of all the ratios collected for that particular hour. As with the PM emissions, the difference between the minimum and maximum hourly ratio for NH3 and CH4 were statistically different. For ammonia, the normalized hourly emissions were less than unity from 00:00 to 06:00, then increased above unity from 06:00 until 15:00, and then decreased to approximately unity for the remainder of the average day. For methane, which exhibited more extremes than NH3, the normalized emission rate was approximately 0.5 during the night (00:00 to 06:00), then increased to
above unity for most of the day (07:00 to 19:00), after which it dropped below unity for the remainder of the average day. The data presented in Fig. 6 is a combination of both the 18 hour day1 and 23 hour day1 lighting cycles. Thus, the low normalized emissions for NH3 and CH4 between 00:00 and 06:00 is not solely a result of the lighting schedules as seen with PM. Counter to the PM10 and PM2.5 emissions for the summer flock, the ammonia and methane emissions were highest during the daytime from 06:00 until 18:00. This implies that NH3 and CH4 emissions were not influenced by bird activity as significantly as PM emissions but their source strength and/or release mechanisms were greater during the day. Ammonia emissions arise from the chemical and microbial breakdown of uric acid found in the
Fig. 5. Ammonia emission rates collected with the model 17C ammonia analyzer and an annular denuder system (ADS) for the duration of the summer production cycle (w45,000 birds).
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Fig. 6. Ratio of the hourly emission rates to the daily mean emission rate of ammonia and methane for the final 21 days of a summer-time production cycle.
excretions of the chickens (Kim et al., 2009; Liu et al., 2006). Methane emissions arise from the anaerobic deposition of organic carbon compounds. During the day, birds produce more excreta, which will replenish or increase the concentration of microbes, uric acid and organics, thus increasing the source strength potential for both ammonia and methane. In addition, daytime temperatures within the house during the summer flock were elevated thus promoting chemical and biological reactions within the litter matrix. For ammonia, the diurnal patterns from the continuous measurements were used to adjust the discrete measurements to represent the mean daily emission rate. In this manner, data from all four flocks could be used to assess the ammonia emissions with respect to bird age as given in Fig. 7. For flock 3, the continuous data for ammonia and methane was averaged on a daily basis and included in the figure. Fig. 7 illustrates an increasing trend in the NH3 emission rate on an AU basis for all four flocks, which indicates that the NH3 emissions are increasing at a rate that is greater than the bird growth. This positive slope suggests that there were additional factor(s) that influence the ammonia emissions. One possible factor is the litter pH, which heavily dictates the conversion of aqueous ammonium to aqueous ammonia and, consequently, the release of ammonia into the air. Equilibrium aqueous chemistry determines the partitioning of the total ammoniacal nitrogen (TAN) between ammonium and ammonia and thus controls the amount of ammonia in the litter that can volatilize into the air. Using an equilibrium constant of 5.5 x 1010, the percentage of ammonia comprising the
TAN is 5% for a pH level of w 8.0 and increases rapidly such that, at a pH of 9.26, 50% of the TAN is ammonia. The litter pH at the end of the first week was approximately 6.0 and increased steadily such that by the end of the second week the litter pH exceeded 8.0 on an average basis. This increase in litter pH by the end of the second week may explain the rise in ammonia emissions observed in Fig. 7 during the same time period. More frequent litter pH measurements would be necessary to ascertain the correlation between ammonia emissions and litter pH. The average of the adjusted daily ammonia emission factors for each flock have been included in Table 1 and give an indication of the potential bias when using the discrete measurements alone. The adjusted mean NH3 emission rate for the winter and spring flocks averaged to 66 g day1 AU1 while the mean emission rate in the summer and summer/fall flocks averaged to 98 g day1 AU1. These emission rates are three times lower than those reported Lacey et al. (2003) and Wheeler et al. (2006). However, these two studies were conducted at broiler facilities that reused built-up litter for subsequent flocks of birds, which would result in more uric acid build-up in the house and greater ammonia emissions. Other studies conducted in Europe indicate that the emission rates from the current study are comparable or lower, with extremes ranging from 57 g day1 AU1 to over 200 g day1 AU1 (Demmers et al., 1999; Phillips et al., 1995). Unlike ammonia, methane emissions on an AU basis peaked early in the summer production cycle and then remained relatively constant for the remainder of the cycle. The initial peak in CH4 emissions during the first week suggests that there was either significant anaerobic decomposition of organic matter in the facility or that there were additional methane source(s) in the facility for a finite period of time. Since there was very little excreta buildup in the first week and limited anaerobic conditions in the litter, it was likely that additional source(s) of CH4 caused the initial rise in the emissions. After the first week, the methane emissions on an AU basis were relatively constant, excluding the 20th and 21st days of the production cycle, thus indicating increases proportional to bird mass. The two CH4 peaks on the 20th and 21st days corresponded to similar peaks in gaseous nitric and hydrochloric acids as well as nitrate-based and chloride-based aerosols, which points to a commonality in behaviour between various pollutants. The average methane emission of 208 g day1 AU1 is much larger than the reported range of zero emission (Guiziou and Béline, 2005) to approximately 15 g day1 AU1 (Monteny et al., 2001). Monteny et al. (2001), however, state that their CH4 emissions were thought to be exceptionally low and were especially hard to justify. 4. Conclusions
Fig. 7. Daily mean emission rates on an AU basis of ammonia and methane over four production cycles and the summer-time flock, respectively.
The mean emission rates of PM10 and PM2.5 on a animal unit basis were 5.0 and 0.78 g day1 AU1, respectively, and were heavily influenced by bird activity. The ratio of PM2.5 to PM10 was seasonally dependent such that, in the cooler seasons, the average ratio was 0.13 whereas in the warmer seasons, the average ratio was 0.20. Inorganic aerosols mean hourly emission rates ranged from 0.15 to 0.46 g day1 AU1 depending on the season, with lower inorganic aerosol emission rates in the cooler months. The contribution of inorganic aerosols to the PM2.5 emissions varied seasonally from 26% for the cooler seasons and increased to 42% for the warmer seasons. Of the inorganic aerosol species, the chloride-based aerosols were the most abundant, contributing on average 90% of the total inorganic aerosol emissions. The average total acid gas emission rate over the four flocks was 0.43 g day1 AU1 with the greatest contribution from nitrous and nitric acids and little contribution from sulfuric acid (as SO2).
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The average emission factor for ammonia, adjusted to the mean daily value, was 82 g day1 AU1 but displayed a seasonal trend with higher emissions in the warmer seasons. The NH3 emissions increased at a rate faster than the bird growth rate, which is attributed to the rise in litter pH after the second week of production. The average methane emission was 208 g day1 AU1 and is significantly higher than comparable values reported in the literature. Various data gaps in emissions rate estimates have not been filled and thus the reported mean values may be biased. In the second paper (Roumeliotis et al., 2010), regression correlations are developed to interpolate the measured emission rates and to apply the correlations to independent data sets. References Anderson, N., Strader, R., Davidson, C., 2003. Airborne reduced nitrogen: ammonia emissions from agriculture and other sources. Environment International 29, 277e286. Baek, B.H., Aneja, V.P., Tong, Q., 2004. Chemical coupling between ammonia, acid gases, and fine particles. Environmental Pollution 129, 89e98. Dando, P., Colls, J.J., Robertson, A.P., 2000. Use of sprays to control particulate concentration in poultry houses: session 1C e health impacts and monitoring. Journal of Aerosol Science 31, 829e830. Demmers, T.G.M., Burgess, L.R., Short, J.L., Phillips, V.R., Clark, J.A., Wathes, C.M., 1999. Ammonia emissions from two mechanically ventilated UK livestock buildings. Atmospheric Environment 33, 217e227. Guiziou, F., Béline, F., 2005. In situ measurement of ammonia and greenhouse gas emissions from broiler houses in France. Bioresource Technology 96, 203e207. Heber, A.J., Bogan, B.W., 2006. The study and regulation of agricultural air quality in the U.S. In: Proceeding from the Workshop on Agricultural Air Quality: State of the Science. MD, USA, pp. 32e35. Kim, W.K., Weeks, L.J., Anderson, R.C., Nisbet, D.J., Dunkley, K., Ricke, S.C., 2009. Effects of nitrocompounds on uric acid-utilizing microorganisms, nitrogen retention, and microbial community in laying hen manure. Journal of Environmental Science and Health, Part B 44 (4), 403e406. Kurvits, T., Marta, T., 1998. Agricultural NH3 and NOx emissions in Canada. Environmental Pollution 102 (SI), 187e194.
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Lacey, R.E., Redwine, J.S., Parnell Jr., C.B., 2003. Particulate matter and ammonia emission factors for tunnel-ventilated broiler production houses in the southern US. Transactions of the ASAE 46, 1203e1214. Liu, Z., Wang, L., Beasley, D.B., 2006. A review of emission models of ammonia released from broiler houses. American Society of Agricultural and Biological Engineers. Paper # 064101. St. Joseph, MI., USA. McBean, E.A., Rovers, F.A., 1998. Statistical Procedures for Analysis of Environmental Monitoring Data and Risk Assessment. Prentice Hall, Inc., Upper Saddle River, NJ, USA, p. 313. Monteny, G.J., Groenestein, C.M., Hilhorst, M.A., 2001. Interactions and coupling between emissions of methane and nitrous oxide from animal husbandry. Nutrient Cycling in Agroecosystems. 60, 123e132. Phillips, V.R., Holden, M.R., White, R.P., Sneath, R.W., Demmers, T.G.M., Wathes, C.M., 1995. Measuring and reducing gaseous and particulate air pollutants from UK livestock buildings. In: Proceedings of the 7th International Symposium on Agricultural and Food Processing Wastes, pp. 241e251. Chicago, Il, USA. Roumeliotis, T.S., Dixon, B.J., Van Heyst, B.J., 2010. Characterization of gaseous pollutants and particulate matter emission rates from a commercial broiler operation part II: correlated emission rates. Atmospheric Environment, doi:10.1016/j.atmosenv.2010.06.051. Roumeliotis, T.S., Van Heyst, B.J., 2008. Summary of ammonia and particulate matter emission factors for poultry operations. Journal of Applied Poultry Research 17, 305e314. Roumeliotis, T.S., Van Heyst, B.J., 2007. Size fractionated particulate matter emissions from a broiler house in southern Ontario, Canada. Science of the Total Environment 383, 174e182. Scientific Committee on Animal Health and Animal Welfare (SCAHAW), 2000. The welfare of chickens kept for meat production (broilers). European Commission: Health and Consumer Protection Directorate-General. SANCO.B.3/AH/R15/2000. p. 150. Van Der Hoek, K., 2007. Particulate matter emissions from animal production in the Netherlands. In: DustConf International Conference. Maastricht, Netherlands, pp. 1e5. Winberry, W. Jr., Ellestad, T., Stevens, B., 1999. Determination of the strong acidity of atmospheric fine-particulates (<2.5 mm): Compendium method IO-4.1. Center of Environmental Research Information, Report: EPA/625/R-96/010a., U.S. Environmental Protection Agency, Cincinnati, OH, USA. Wheeler, E.F., Casey, K.D., Gates, R.S., Xin, H., Zajaczkowski, J.L., Topper, P.A., Liang, Y., Pescatore, A.J., 2006. Ammonia emissions from twelve U.S. broiler chicken houses. American Society of Agricultural and Biological Engineers: Transactions of the ASABE 49 (5), 1495e1512.
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Characterization of gaseous pollutant and particulate matter emission rates from a commercial broiler operation part I: Observed trends in emissions Taylor S. Roumeliotis, Brad J. Dixon, Bill J. Van Heyst* School of Engineering, University of Guelph, 50 Stone Rd. Guelph, Ontario N1G 2W1, Canada
a r t i c l e i n f o
a b s t r a c t
Article history: Received 21 January 2010 Received in revised form 25 June 2010 Accepted 28 June 2010
This paper characterizes the emission rates of size fractionated particulate matter, inorganic aerosols, acid gases, ammonia and methane measured over four flocks at a commercial broiler chicken facility. Mean emission rates of each pollutant, along with sampling notes, were reported in this paper, the first in a series of two. Sampling notes were needed because inherent gaps in data may bias the mean emission rates. The mean emission rates of PM10 and PM2.5 were 5.0 and 0.78 g day1 [Animal Unit, AU]1, respectively, while inorganic aerosols mean emission rates ranged from 0.15 to 0.46 g day1 AU1 depending on the season. The average total acid gas emission rate was 0.43 g day1 AU1 with the greatest contribution from nitrous and nitric acids and little contribution from sulfuric acid (as SO2). Ammonia emissions were seasonally dependent, with a mean emission rate of 66.0 g day1 AU1 in the cooler seasons and 94.5 g day1 AU1 during the warmer seasons. Methane emissions were relatively consistent with a mean emission rate of 208 g day1 AU1. The diurnal pattern in each pollutant’s emission rate was relatively consistent after normalizing the hourly emissions according to each daily mean emission rate. Over the duration of a production cycle, all the measured pollutants’ emissions increased proportionally to the total live mass of birds in the house, with the exception of ammonia. Interrelationships between pollutants provide evidence of mutually dependent release mechanisms, which suggests that it may be possible to fill data gaps with minimal data requirements. In the second paper (Roumeliotis, T.S., Dixon, B.J., Van Heyst, B.J. Characterization of gaseous pollutants and particulate matter emission rates from a commercial broiler operation part II: correlated emission rates. Atmospheric Environment, 2010.), regression correlations are developed to estimate daily mean emission rates for data gaps and, using the normalized hourly diurnal patterns from this paper, emission factors were generated for each pollutant. Ó 2010 Elsevier Ltd. All rights reserved.
Keywords: Acid gases Ammonia Methane Inorganic aerosols Particulate matter Emission rates Broiler chickens Diurnal pattern
1. Introduction Commercial poultry facilities are responsible for emitting a variety of pollutants. Of these pollutants, ammonia (NH3) and particulate matter less than or equal to ten and 2.5 microns in diameter (PM10 and PM2.5, respectively) have been focused on due to their detrimental effects on human health and the environment and abundance inside the poultry houses (Lacey et al., 2003; Phillips et al., 1995; Roumeliotis and Van Heyst, 2008; Wheeler et al., 2006). In Canada, 87% of the NH3 emissions are attributed to agriculture and 82% of these emissions have been estimated to originate from primary livestock production (Kurvits and Marta, 1998). Ammonia is the most prevalent alkaline gas in the atmosphere and associates with acidic gases to neutralize the pH. This * Corresponding author. Tel.: þ1 519 824 4120x53665; fax: þ1 519 836 0227. E-mail address: [email protected] (B.J. Van Heyst). 1352-2310/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2010.06.052
neutralization process results in the formation of liquid and solid inorganic aerosols, typically in the PM2.5 size fraction. Sulfuric, nitric, and hydrochloric acid are the three main acidic species that interact with NH3 to form ammonium sulfate, ammonium bisulfate, ammonium nitrate and ammonium chloride, respectively (Anderson et al., 2003; Baek et al., 2004). As poultry houses experience elevated levels of ammonia, it may be possible that any acid gases present in the barn atmosphere will be neutralized prior to being emitted from the facility and contribute to the overall PM2.5 burden. Another gaseous pollutant of concern is methane (CH4) but it has not been well characterized for poultry operations since, unlike ruminants, poultry do not generate large quantities of CH4 in their digestive tract. Methane, however, can be generated from the anaerobic decomposition of the organic matter in the litter. The objective of this paper was to quantify the emissions of PM10, PM2.5, inorganic aerosols in the PM2.5 size fractionation, acid gases, ammonia, and methane from a commercial broiler chicken
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facility using discrete and continuous measurement techniques. Emission trends need to be characterized, both diurnally and seasonally, to be able to interpret any data gaps due to instrument calibration and failures. Influential house management and/or environmental factors that affect one or more of the pollutants also need to be considered in any data interpolation method. This paper, the first in a series of two, focuses on characterizing the emissions of numerous pollutants from a broiler facility over four production flocks. The second paper develops correlations needed to address the missing data gaps and provides estimates of total emissions (Roumeliotis et al., 2010). 2. Materials and methods The commercial broiler chicken facility used in the current study was a single storey (150.5 m by 18.3 m), mechanically cross-ventilated house located just outside of Guelph, Ontario, Canada. The house used a litter floor with new bedding, either wheat straw or wood shavings, placed at the beginning of each bird production cycle. Feed was auger-fed to the birds through rows of troughs and water was delivered via nipple drinkers. The house temperature and relative humidity were controlled using radiant pipe heaters and a staged ventilation program. Heaters were used for roughly the first ten days to maintain a temperature that gradually decreased from 34 to 27 C. After this time, fans were used to provide air exchanges in order to continually decrease the temperature from 26 to 19 C over the remainder of the production cycle. The facility used six variable speed fans (0.56 m diameter), 12 dual speed on/off fans (0.65 m diameter), and 10 single speed on/off fans (1.3 m diameter) for a total of 28 fans. Two lighting schedules of either 23 or 18 h of light each day were used at different stages in the production cycle to control the sleeping patterns of the chickens. The 23 hour day1 cycle was used for the first five to six days and again after 22e24 days until completion. The measurement campaign spanned four production flocks of broilers of approximately 45,000 broilers from February to September 2009. These four flocks of broilers were raised during representative seasons for the geographic region of winter, spring, summer, and summer/fall, respectively. During the four observed cycles, birds were raised from an average weight of 47 g to 1810 g over a period of 31e34 days. 2.1. Instrumentation Reactive gases (ammonia, hydrochloric acid, nitric acid, nitrous acid, and sulfuric acid (as sulfur dioxide)) and inorganic aerosol species (ammonium bound with chloride, nitrate, and sulfate) were collected from inside the broiler house using an annular denuder system (ADS; URG-3000C-ADS; URG Corporation, Chapel Hill, NC, USA). Samples were collected three times a week with each sampling period lasting approximately one hour. The ADS consisted of a 2.5 micron sharp cut-size cyclone followed by a series of nine, three-channel glass annular denuders used to adsorb the reactive gases by coating their walls with either 1% phosphorous acid or 1% sodium carbonate solutions. This was followed by a two-stage filter pack that collected the inorganic aerosols on a Teflon and nylon filter. Contents on both the annular denuders and filters were extracted following Winberry et al. (1999). All extracts were analyzed using an ion chromatography system (Dionex IC-2000 ICS; Dionex Corporation, Sunnyvale, CA, USA). The resulting cationic and anionic species were converted to their respective gaseous and particulate concentrations based on the extraction volume and the standardized air sample volume. Continuous PM10 and PM2.5 concentrations were measured using two DustTrakÒ aerosol monitors (Model 8520; TSI Incorporated,
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Shoreview, MN, USA) installed with 10 and 2.5 micron sharp cut-size inlet conditioners. Dust samples collected from the broiler house were used to adjust the calibration density of the DustTrak aerosol monitors. For the summer production cycle, ammonia was measured using a chemiluminescent ammonia analyzer (Model 17C, Thermo Electron Corporation, Franklin, MA, USA) while methane was measured continuously using a back-flush gas chromatography system coupled with a flame ionization detector (Model 55C, Thermo Electron Corporation, Franklin, MA, USA). Volumetric exhaust rates from the three different fan sizes were quantified using an AlnorÒ balometer kit (EBT721; Alnor Products, Shoreview, MN, USA) consisting of a capture hood and a 16 point velocity matrix connected to micromanometers. 2.2. Sampling procedures Air samples were drawn from the longitudinal midpoint of the barn through four horizontally integrated inlets, positioned inside the broiler house at a distance of 2.5 m from the exhaust fans and at a height of 1.8 m. This location produced representative pollutant concentrations in the exhaust air while avoiding a large change in velocity between the inlets and surrounding air (Heber and Bogan, 2006). The ADS and DustTrak monitors were located inside the facility while the Model 17C and 55C were situated in a climatecontrolled trailer located on the fresh air intake side of the facility. The house ventilation was managed by a 14 progressive stage, automated control system that records power used by the three fan sizes. The balometer was used to measure representative flow rates for the fans used in each of the 14 stages. The hourly averaged total house ventilation was, then, estimated using the individual exhaust rates with continuously monitored power usage by the facility’s ventilation. In addition, temperature, relative humidity and pressure were continuously measured both inside and outside the facility. Water consumption, average bird weight, and mortalities were recorded daily. Litter moisture, pH, ammonium-N, total ammoniacal nitrogen, and extractable chloride, were quantified every three to five days from composite litter samples and subsequent lab analysis. 2.3. Emission rate calculation Hourly averaged pollutant emission rates (E, g day1 AU1) were calculated on an animal unit (AU, equivalent to 500 kg live weight) basis using the number of birds and their average mass (M, kg), the hourly exhaust concentration (C, g m3), the outdoor concentration (Co, g m3), and the hourly total house ventilation rate (Q, m3 day1) as (Wheeler et al., 2006):
E ¼
ðC Co ÞQ 500 kg M AU
(1)
Since the outdoor air concentrations could not be measured simultaneously with the indoor air concentrations, a single daily averaged value for Co was estimated for each pollutant using a set of outdoor air measurements. The mean concentration (C o , g m3) from the outdoor set of measurements was adjusted using a statistical method designed to contain a specified proportion of the population with a specified confidence based on the standard deviation of the outdoor concentration measurements (S, g m3) and the uncertainty of the sample size, n, represented by the t-distribution with 95% coverage, t0.95,n1, as (McBean and Rovers, 1998):
Co ¼ C o þ t0:95;n1 S
(2)
If an exhaust concentration was quantified to be lower than Co, the emission rate was set to zero.
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3. Results and discussion Table 1 contains a summary of all the emissions quantified from the facility using both continuous and discrete measurement techniques. Each flock had incomplete continuous measurements (see sampling notes in Table 1) and a limited number of discrete measurements. 3.1. Particulate matter emissions As given in Table 1, the average PM10 and PM2.5 emission rate for the four flocks were 5.0 and 0.78 g day1 AU1, respectively. There was, however, significant variability in the PM10 and PM2.5 emissions on a diurnal basis as displayed in Fig. 1aed. On an hourly basis, the PM10 and PM2.5 emissions ranged from 0.22 to 60.48 g day1 AU1 and 0.08 to 7.34 g day1 AU1, respectively. In spite of the variations, the PM emissions, in units of g day1, generally increased exponentially over time similar to the increase in bird mass. Thus, the emission rates, on an AU basis, as given in Fig. 1, tended to remain relatively constant or even decreased at the tail end as a result of the exponential increase in the bird live weight. The dependence of PM emissions on bird mass is due to the increasing quantity of excreta produced, litter disturbed, feathers and dander shed and feed consumed and spilled as the bird grows (Dando et al., 2000). The spring and summer/fall flocks had less than 80% completeness. Data gaps in the spring flock occurred during the second and fifth week due to power failures, which may have caused the mean emission factor for PM10 of 6.1 g day1 AU1 to be inflated since the initial spike in the first week would have a relatively greater contribution to the mean emission. Conversely, the summer/fall flock is missing data for the first week, or the period with elevated emissions on an AU basis, which implies that the estimate for PM10 of 2.9 g day1 AU1 may be low. Aside from the third week of the summer/fall flock, the PM2.5 and PM10 behaved similarly as shown in Fig. 1 with the PM2.5 axis set to 1/10th of the PM10 axis. The average ratio of PM2.5 to PM10 for the winter and spring flocks was approximately 0.13 0.10 while for the summer and summer/fall flocks, the average ratio was approximately 0.20 0.13, which is statistically different from the winter/spring flocks. In comparison to literature values, the mean PM10 and PM2.5 emission rates were 14 and 36%, respectively, lower than the emission rate estimates from a 2006 measurement campaign at the same facility using different bird growth cycles (Roumeliotis and Van Heyst, 2007). Two studies with similar broiler facility design reported PM10 emission rate, Lacey et al. (2003) and Van Der Hoek (2007). The mean PM10 emission rate was lower than the average PM10 emission rate of 12.9 g day1 AU1 obtained from Lacey et al. (2003) but higher than 1.9 g day1 AU1 derived using emission data reported by Van Der Hoek (2007) (Roumeliotis and Van Heyst, 2008).
The prominent diurnal trend in PM10 and PM2.5 emissions depended greatly on the photoperiod or activity level of the birds. To illustrate this point, Fig. 2aed displays the average hourly ratios of the hourly emission rate to the daily average emission rate for the 18 hour day1 and 23 hour day1 lighting periods. The average standard deviation for each flock in Fig. 2 was 20% with the exception of PM2.5 under the 18 hour day1, which was slightly higher at 26%. The minimum and maximum normalized emission rates for PM10 and PM2.5 for each flock were statistically different using a two group comparison test (p-value was zero using three decimal place accuracy). The diurnal pattern for both the PM10 and PM2.5 ratio of average hourly to average daily emission rates with the 18 h of light were similar for all flocks. During the dark periods, the ratio of average hourly to average daily emission rates were 0.31 0.13 and 0.61 0.14 for PM10 and PM2.5, respectively, thus indicating that PM2.5 emissions may not have been as dependent on bird activity as the PM10 emissions. The reasons for this may include the relatively slower settling velocity of the smaller particulates as well as different generation mechanisms for the PM2.5 such as the formation of fine inorganic aerosols. During the hours of light, the PM10 emissions spiked between 06:00 and 08:00 when the lights were switched on. Although each flock displayed a unique behaviour during the hours of light, the overall trend was fairly constant with average normalized values of 1.22 0.16 and 1.13 0.11 for PM10 and PM2.5, respectively. When the 23 hour day1 lighting period was utilized, there was insufficient time to exhaust or settle the PM10 and PM2.5, which resulted in virtually no uniform diurnal pattern. One pattern that does emerge is the dependence on season. In the PM10 and PM2.5 plots, the winter and spring flocks’ ratio was greater than 1.0 during the daytime from approximately 08:00 until 23:00, whereas the summer and summer/fall flocks ratio was typically greater than 1.0 at night from approximately 20:00 until 08:00. The summer and summer/fall flocks’ diurnal pattern is the result of excessive indoor house temperatures (approaching 30 C) that could not be maintained in the ideal range due to the warm weather especially in the afternoon. To maintain optimal feed conversion ratios and normal weight gain, the indoor temperature should be gradually reduced from 22 C down to 19 C from day 22 to 34 (SCAHAW, 2000). As indoor temperatures in the afternoon exceed the comfort point, the birds reduced their activity levels and feeding to remain in the zone of thermoneutrality (SCAHAW, 2000). Thus these periods of elevated indoor temperatures during the two summer flocks resulted in reduced bird activity leading to lower PM emission rates measured in the later afternoon periods. For the winter and spring flocks, bird activity typically increased in the afternoon as the outdoor temperatures increased. As this lighting period is typical at the end of the cycle the reliance on the radiant pipe heaters is dramatically reduced from the start of the cycle.
Table 1 Summary of continuous and discrete emission measurements from four flocks of broilers. Sampling regularity
Pollutant emissions Flock (representative season) g day1 AU1
1 (winter)
Sampling notes 2 (spring)
Sampling notes 3 (summer)
Sampling notes 4 (summer/fall) Sampling notes
Continuous
PM10 PM2.5 Ammonia Methane
5.7 3.4 0.74 0.54 ND ND
96.9% complete 6.1 5.4 96.9% complete 0.85 0.73 e ND e ND
51.5% complete 5.3 3.0 51.5% complete 0.94 0.54 e 107.4 42.0 e 208.2 126.5
86.8% 86.8% 60.6% 57.0%
complete 2.9 1.5 complete 0.61 0.58 complete ND complete ND
72.4% complete 72.4% complete e e
Discrete Inorganic aerosols (w1 h Samples) Acid gases Ammonia
0.15 0.08 16 samples 0.40 0.39 9 samples 72.8 57.4 9 samples
0.24 0.23 16 samples 0.46 0.41 13 samples 84.3 56.9 13 samples
0.46 0.26 0.42 0.42 109.7 65.0
14 samples 14 samples 14 samples
0.45 0.23 0.42 0.22 123.9 76.4
10 samples 10 samples 10 samples
Adjusted
63.0 49.9 9 samples
69.0 46.6 13 samples
92.8 52.0
14 samples
101.8 62.0
10 samples
Ammonia
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Fig. 1. Emission rates on an animal unit basis (AU), equivalent to 500 kg live weight, for PM10 and PM2.5 during (a) winter, (b) spring, (c) summer, and (d) summer to fall production cycles.
Fig. 2. Ratio of the hourly emission rates to the daily mean emission rate for PM10 using (a) 18 hour and (b) 23 hour lighting periods and for PM2.5 using (c) 18 hour and (d) 23 hour lighting periods for all four broiler production cycles.
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3.2. Inorganic aerosol and acid gas emissions Fig. 3aed displays the inorganic aerosol emission rates on an AU basis according to each anionic species for the four production cycles, respectively. The winter and spring flocks (Flocks 1 and 2) resulted in lower overall inorganic aerosol emission rates than the summer and summer/fall flocks (Flocks 3 and 4) (see Table 1). Recalling that the PM2.5 to PM10 ratio for flocks 3 and 4 was approximately 50% greater than the first two flocks, it is reasonable to conclude that the inorganic aerosol formation contributed to the additional PM2.5 in these later flocks. The average ratio of inorganic aerosols (including chloride, sulfate, nitrate, associated with ammonium) to PM2.5 emissions was 26% for flocks 1 and 2 in contrast to 42% for flocks 3 and 4. The third and fourth flocks occurred during the warmer months with frequent inorganic aerosols emissions in excess of 400 mg day1 AU1. During the warmer months, there are two competing issues. The first is that the air retention time in the house decreases due to increased ventilation which should lower pollutant concentrations. The second issue is that the increased indoor temperature will allow the inorganic aerosol formation kinetics to progress at a faster rate. Based on the experimental measurements, the indoor temperature is responsible for a larger effect on the inorganic aerosol generation. Spikes in the inorganic aerosol emissions typically occurred simultaneously with spikes in the PM2.5 emissions. This is best illustrated in the summer/fall flock on days 18 and 20 where the spikes in inorganic aerosol emissions (hourly average emission > 600 mg day1 AU1) corresponded to the large spikes in PM2.5 emissions (see Fig. 1d). Of the individual inorganic aerosol species, the chloride-based aerosols were always the most abundant in all four flocks. The average proportion of chloride-based aerosols to total inorganic
aerosols over the four flocks was 90%. This is somewhat unexpected since ambient inorganic aerosols are dominated by the sulfate and nitrate species (Anderson et al., 2003). This points to a potential chloride source within the house. Emission rates of acid gases, one of the precursors required for inorganic aerosol formation, are given in Fig. 4aed for hydrochloric acid (HCl(g)), nitrous acid (HONO(g)), nitric acid (HNO3(g)) and sulfur dioxide (SO2(g)) respectively. Acid gas concentrations that were at or below the detection limit of the ion chromatograph or below their outdoor air concentration were not included in Fig. 4. Note that Fig. 4 is organized based on acid gas species rather than the bird cycle to facilitate comparison between the acid gases. From Fig. 4, it is apparent that very little sulfuric acid (as SO2) is emitted from the house for any flock implying that any SO2 in the house reacts quickly with ammonia. In addition, the HCl concentrations are consistently above ambient but its gaseous emission rate was comparatively low to its aerosol emission rate implying that most of the HCl is consumed in inorganic aerosol formations. For the nitrogen-based species, very little of the HONO and HNO3 acids react in spite of an excess of gaseous ammonia (see next section). These results suggest that the sulfate and chloride formation sequences are favoured over the nitrogen-based sequences. Concentrations of HCl, HONO and HNO3 were regularly above the mean ambient concentration, whereas SO2 concentrations were only above the mean ambient 14% of the time suggesting that there may be a source inside the house for HCl, HONO and HNO3. The near constant behaviour of HCl emissions on an AU basis suggests that the HCl is increasing exponentially at a rate similar to the exponential increase in bird mass and thus its source is related to the bird growth. For the case of HONO, the decreasing emission rate on an AU basis implies an independence from the bird mass and
Fig. 3. Emission rates on an AU basis for three inorganic aerosol species during (a) winter, (b) spring, (c) summer, and (d) summer to fall production cycles.
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Fig. 4. Emission rates on an AU basis for acidic gases including (a) hydrochloric acid, (b) nitrous acid, (c) sulfur dioxide, and (d) nitric acid for four production cycles.
thus any in house source would need to be independent of the bird production. For HNO3, no distinct relationship with bird mass can be discerned. 3.3. Ammonia and methane emissions Ammonia and methane are discussed jointly since their generation mechanisms should be similar due to both being formed from the microbial breakdown of nutrients found in excreta. The discrete ammonia measurements given in Table 1 indicate a seasonal variation with greater emissions during the warmer months. Continuous measurements of ammonia and methane were conducted simultaneously with the ADS ammonia measurements for the last 21 days of flock 3 (summer) with the results shown in Fig. 5. For ammonia, the emission factors estimated based on the discrete and continuous measurements are consistent, however, the hourly fluctuations in NH3 emissions can be significant and that the ADS discrete measurements cannot capture diurnal trends. For methane, no other data exists to compare with the continuous data. Using the continuous data from flock 3, the average of the hourly ratios of NH3 and CH4 hourly average to daily average emission rates are displayed in Fig. 6, similarly to Fig. 2 for PM. The error bars on the data in Fig. 6 represent one standard deviation of all the ratios collected for that particular hour. As with the PM emissions, the difference between the minimum and maximum hourly ratio for NH3 and CH4 were statistically different. For ammonia, the normalized hourly emissions were less than unity from 00:00 to 06:00, then increased above unity from 06:00 until 15:00, and then decreased to approximately unity for the remainder of the average day. For methane, which exhibited more extremes than NH3, the normalized emission rate was approximately 0.5 during the night (00:00 to 06:00), then increased to
above unity for most of the day (07:00 to 19:00), after which it dropped below unity for the remainder of the average day. The data presented in Fig. 6 is a combination of both the 18 hour day1 and 23 hour day1 lighting cycles. Thus, the low normalized emissions for NH3 and CH4 between 00:00 and 06:00 is not solely a result of the lighting schedules as seen with PM. Counter to the PM10 and PM2.5 emissions for the summer flock, the ammonia and methane emissions were highest during the daytime from 06:00 until 18:00. This implies that NH3 and CH4 emissions were not influenced by bird activity as significantly as PM emissions but their source strength and/or release mechanisms were greater during the day. Ammonia emissions arise from the chemical and microbial breakdown of uric acid found in the
Fig. 5. Ammonia emission rates collected with the model 17C ammonia analyzer and an annular denuder system (ADS) for the duration of the summer production cycle (w45,000 birds).
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Fig. 6. Ratio of the hourly emission rates to the daily mean emission rate of ammonia and methane for the final 21 days of a summer-time production cycle.
excretions of the chickens (Kim et al., 2009; Liu et al., 2006). Methane emissions arise from the anaerobic deposition of organic carbon compounds. During the day, birds produce more excreta, which will replenish or increase the concentration of microbes, uric acid and organics, thus increasing the source strength potential for both ammonia and methane. In addition, daytime temperatures within the house during the summer flock were elevated thus promoting chemical and biological reactions within the litter matrix. For ammonia, the diurnal patterns from the continuous measurements were used to adjust the discrete measurements to represent the mean daily emission rate. In this manner, data from all four flocks could be used to assess the ammonia emissions with respect to bird age as given in Fig. 7. For flock 3, the continuous data for ammonia and methane was averaged on a daily basis and included in the figure. Fig. 7 illustrates an increasing trend in the NH3 emission rate on an AU basis for all four flocks, which indicates that the NH3 emissions are increasing at a rate that is greater than the bird growth. This positive slope suggests that there were additional factor(s) that influence the ammonia emissions. One possible factor is the litter pH, which heavily dictates the conversion of aqueous ammonium to aqueous ammonia and, consequently, the release of ammonia into the air. Equilibrium aqueous chemistry determines the partitioning of the total ammoniacal nitrogen (TAN) between ammonium and ammonia and thus controls the amount of ammonia in the litter that can volatilize into the air. Using an equilibrium constant of 5.5 x 1010, the percentage of ammonia comprising the
TAN is 5% for a pH level of w 8.0 and increases rapidly such that, at a pH of 9.26, 50% of the TAN is ammonia. The litter pH at the end of the first week was approximately 6.0 and increased steadily such that by the end of the second week the litter pH exceeded 8.0 on an average basis. This increase in litter pH by the end of the second week may explain the rise in ammonia emissions observed in Fig. 7 during the same time period. More frequent litter pH measurements would be necessary to ascertain the correlation between ammonia emissions and litter pH. The average of the adjusted daily ammonia emission factors for each flock have been included in Table 1 and give an indication of the potential bias when using the discrete measurements alone. The adjusted mean NH3 emission rate for the winter and spring flocks averaged to 66 g day1 AU1 while the mean emission rate in the summer and summer/fall flocks averaged to 98 g day1 AU1. These emission rates are three times lower than those reported Lacey et al. (2003) and Wheeler et al. (2006). However, these two studies were conducted at broiler facilities that reused built-up litter for subsequent flocks of birds, which would result in more uric acid build-up in the house and greater ammonia emissions. Other studies conducted in Europe indicate that the emission rates from the current study are comparable or lower, with extremes ranging from 57 g day1 AU1 to over 200 g day1 AU1 (Demmers et al., 1999; Phillips et al., 1995). Unlike ammonia, methane emissions on an AU basis peaked early in the summer production cycle and then remained relatively constant for the remainder of the cycle. The initial peak in CH4 emissions during the first week suggests that there was either significant anaerobic decomposition of organic matter in the facility or that there were additional methane source(s) in the facility for a finite period of time. Since there was very little excreta buildup in the first week and limited anaerobic conditions in the litter, it was likely that additional source(s) of CH4 caused the initial rise in the emissions. After the first week, the methane emissions on an AU basis were relatively constant, excluding the 20th and 21st days of the production cycle, thus indicating increases proportional to bird mass. The two CH4 peaks on the 20th and 21st days corresponded to similar peaks in gaseous nitric and hydrochloric acids as well as nitrate-based and chloride-based aerosols, which points to a commonality in behaviour between various pollutants. The average methane emission of 208 g day1 AU1 is much larger than the reported range of zero emission (Guiziou and Béline, 2005) to approximately 15 g day1 AU1 (Monteny et al., 2001). Monteny et al. (2001), however, state that their CH4 emissions were thought to be exceptionally low and were especially hard to justify. 4. Conclusions
Fig. 7. Daily mean emission rates on an AU basis of ammonia and methane over four production cycles and the summer-time flock, respectively.
The mean emission rates of PM10 and PM2.5 on a animal unit basis were 5.0 and 0.78 g day1 AU1, respectively, and were heavily influenced by bird activity. The ratio of PM2.5 to PM10 was seasonally dependent such that, in the cooler seasons, the average ratio was 0.13 whereas in the warmer seasons, the average ratio was 0.20. Inorganic aerosols mean hourly emission rates ranged from 0.15 to 0.46 g day1 AU1 depending on the season, with lower inorganic aerosol emission rates in the cooler months. The contribution of inorganic aerosols to the PM2.5 emissions varied seasonally from 26% for the cooler seasons and increased to 42% for the warmer seasons. Of the inorganic aerosol species, the chloride-based aerosols were the most abundant, contributing on average 90% of the total inorganic aerosol emissions. The average total acid gas emission rate over the four flocks was 0.43 g day1 AU1 with the greatest contribution from nitrous and nitric acids and little contribution from sulfuric acid (as SO2).
T.S. Roumeliotis et al. / Atmospheric Environment 44 (2010) 3770e3777
The average emission factor for ammonia, adjusted to the mean daily value, was 82 g day1 AU1 but displayed a seasonal trend with higher emissions in the warmer seasons. The NH3 emissions increased at a rate faster than the bird growth rate, which is attributed to the rise in litter pH after the second week of production. The average methane emission was 208 g day1 AU1 and is significantly higher than comparable values reported in the literature. Various data gaps in emissions rate estimates have not been filled and thus the reported mean values may be biased. In the second paper (Roumeliotis et al., 2010), regression correlations are developed to interpolate the measured emission rates and to apply the correlations to independent data sets. References Anderson, N., Strader, R., Davidson, C., 2003. Airborne reduced nitrogen: ammonia emissions from agriculture and other sources. Environment International 29, 277e286. Baek, B.H., Aneja, V.P., Tong, Q., 2004. Chemical coupling between ammonia, acid gases, and fine particles. Environmental Pollution 129, 89e98. Dando, P., Colls, J.J., Robertson, A.P., 2000. Use of sprays to control particulate concentration in poultry houses: session 1C e health impacts and monitoring. Journal of Aerosol Science 31, 829e830. Demmers, T.G.M., Burgess, L.R., Short, J.L., Phillips, V.R., Clark, J.A., Wathes, C.M., 1999. Ammonia emissions from two mechanically ventilated UK livestock buildings. Atmospheric Environment 33, 217e227. Guiziou, F., Béline, F., 2005. In situ measurement of ammonia and greenhouse gas emissions from broiler houses in France. Bioresource Technology 96, 203e207. Heber, A.J., Bogan, B.W., 2006. The study and regulation of agricultural air quality in the U.S. In: Proceeding from the Workshop on Agricultural Air Quality: State of the Science. MD, USA, pp. 32e35. Kim, W.K., Weeks, L.J., Anderson, R.C., Nisbet, D.J., Dunkley, K., Ricke, S.C., 2009. Effects of nitrocompounds on uric acid-utilizing microorganisms, nitrogen retention, and microbial community in laying hen manure. Journal of Environmental Science and Health, Part B 44 (4), 403e406. Kurvits, T., Marta, T., 1998. Agricultural NH3 and NOx emissions in Canada. Environmental Pollution 102 (SI), 187e194.
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