Download this Paper - MS Word

ODOR CARRYING CHARACTERISTICS OF DUST FROM SWINE FACILITIES

Summary:

Odor nuisance has become a major problem in the swine industry. Foul-smelling dust plays a major role in the spreading of odor. Gas chromatography equipped with a flame ionization detector has successfully separated the compounds adsorbed on the dust. Initial results show that there are approximately 70 to 100 volatile compounds adsorbed on the dust. The major compounds are similar for different buildings during different seasonal operations although there is a difference in the concentration levels. A comparison of the gas chromatograms of Tenax with dust and feed reveals a large amount of volatile fatty acids (VFA) and p-cresol adsorbed to the Tenax, but not dust or feed. Also, indolic compounds were not detected on the Tenax, dust or feed. All compounds will be identified with mass spectrometry in the future.

Keywords: Dust, odor compounds, swine facilities

ODOR CARRYING CHARACTERISTICS OF DUST FROM SWINE FACILITIES

Abstract: Odor nuisance has become a major problem in the swine industry. Foul-smelling dust plays a major role in the spreading of odor. Gas chromatography equipped with a flame ionization detector has successfully separated the compounds adsorbed on the dust. Initial results show that there are approximately 70 to 100 volatile compounds adsorbed on the dust. The major compounds are similar for different buildings during different seasonal operations although there is a difference in the concentration levels. A comparison of the gas chromatograms of Tenax with dust and feed reveals a large amount of volatile fatty acids (VFA) and p-cresol adsorbed to the Tenax, but not dust or feed. Also, indolic compounds were not detected on the Tenax, dust or feed. All compounds will be identified with mass spectrometry in the future.

Keywords: Dust, odor compounds, swine facilities

INTRODUCTION

Due to market forces, there is a trend towards raising large numbers of animals in livestock management facilities. According to the Illinois Pork Producers Association, Illinois is the fourth largest hog producer and approximately 41% of Illinois hog farms have at least 2,000 animals - four times more than the typical large-scale facility from 17 years ago. As the number of animals at a livestock management facility increases, there is a potential for greater environmental impact in adjacent area. The importance of pork production is often overlooked when environmental problems arise. Unpleasant odor is one of the main problems associated with swine facilities. A well-managed lagoon has very little odor production and is not considered a major source of odor. Land application can release odorous gases only for short periods. Much of the odor comes from the building's exhaust air. Foul-smelling dust plays a major role in the spreading of odor, especially for odor nuisance outside the building because odorous molecules adsorbed and absorbed to a dust particle can travel long distances and stay odorous for a long time.

A strong correlation exists between the presence of odors and aerosol particles from livestock buildings (Day et al., 1965; Burnett, 1969; Eby and Willson, 1969; Hammond et al., 1979). Day et al. (1965) reported that most of the odor of swine houses was carried on dust. Eby and Willson (1969) also reported that most of the odor of poultry houses can be eliminated by removal of air-borne dust. Hammond et al. (1979) confirmed that the intensely odorous air inside the swine confinement building was odorless when smelled through a Millipore filter. To assess dust carrying odor problems, three fundamental questions need to be answered:

1. What types of compounds make dust unpleasant?
2. How much odor does it carry?
3. What sizes of particles carry most of the odor?

Without a clear answer to these questions, measurement and control of swine odor will be a slow trial and error process. O'Neill and Phillips (1992) recommended that the relationship between odor and dust should be studied further. Therefore, it is very important to study odor carrying characteristics of dust, so that the nature of odor transportation can be better understood and appropriate control strategies can be implemented. For example, quantifying odor carried on different sizes of dust particles allows for optimization of dust and odor removal strategies. The objectives of our research are:

1. Confirm the importance of the dust in the odor from swine facilities;
2. Identify the odorous compounds carried on the swine dust;
3. Compare the odor level of dust from different swine buildings;
4. Develop an odor and dust sampling protocol that can be used for odor studies.

Identifying swine odor is very complicated. A variety of direct (olfactmetry) and indirect methods (analytical instruments) have been used to measure the odor intensity and determine the odor components (Mackie et al., 1998). More than 168 volatile compounds have been identified in swine waste (O'Neill and Phillips, 1992). Olfactmetry is based on the threshold measurement method and depends on panel members. One of the limitations of olfactometry is that they can not identify the compounds that cause the odor. Gas chromatography (GC) with flame ionization detection (FID) is a widely used powerful tool, which can identify and quantify the multitude of odorous compounds. In this project, we are using a GC/FID to produce chromatograms for analysis. For identification of unknown compounds, where the retention time of standards do not match, MS is used.

Comparisons of GC/FID chromatograms of dust from various building types and seasonal operation are made in this paper. Additionally, comparisons of GC/FID chromatograms of feed and Tenax, a wide spectrum adsorbent, are presented.

MATERIAL AND METHODS

Analytical Method

The GC/FID used for all the work presented was a dual column, dual FID system. One column was a 30 m x 0.25 mm ID, 0.25 μm film thickness, non-polar DB-5 column (J&W Scientific, P/N 122-5532). The second column was a 30 m x 0.25 mm ID, 0.25 ?m film thickness, polar DB-WAX column (J&W Scientific, P/N 122-7032). The carrier gas was helium (11.6 psi) with a flow rate of 1 ml/min. The oven temperature was programmed as follows: 40°C for 5 minutes followed by a 5°C/min increase to 250°C and then held for 10 minutes. The dust samples were stored in 22 ml headspace vials sealed with Teflon lined silicone septa, which were automatically sampled with a Tekmar 7000/7050 Equilibrium Headspace Autosampler. The autosampler was set as follows: platen = 90°C, sample equilibrium = 10 minutes, mixer off, cryo cool down = 5 minutes @ -165°C, vial pressurization for 1 minute @ 7 psi, vial pressure equilibrium = 0.25 minute, loop fill = 0.26 minute, loop equilibration = 0.20 minute, inject = 5 minutes, cryo inject = 5 min @ 250°C, loop = 150°C, line = 180°C, cryo union heater = 200°C, vial needle flow control set to 3/4 turn open or 47 ml/min, loop fill exhaust connected to Tekmar Viper back pressure regulator. A data system with a Pentium processor and a large hard disk was equipped to collect, store, and manipulate the data generated by the GC/FID system. Hewlet Packard Chemstation software was used to integrate the data and report the results. Integration parameters for each column were as follows: DB-5 minimum peak area = 1,000, minimum peak width = 0.105, slope sensitivity = 284; DB-WAXETR minimum peak area = 3,000, minimum peak width = 0.048, slope sensitivity = 696.

Sampling Method

The buildings used for the experiments are located at the Swine Research Center, University of Illinois at Urbana-Champaign (UIUC). One is a finishing building (80' x 40' x 7') with 240 pigs weighing approximately 160-250 lbs. and the other is a growing building (60' x 40' x 7') with 240 pigs weighing approximately 100 lbs. Ventilation was provided to these two buildings by exhaust fan systems. During winter operation, the building temperature was approximately 65-70?F, while during summer operation the temperature was approximately 85-90°F. The approximate ventilation rate for the growing building was 6,000 cfm for winter operation and 20,000 cfm for summer operation. The approximate ventilation rate for the finishing building was 9,000 cfm for winter operation and 32,000 cfm for summer operation. Six trays were hung from the ceiling at a height of 6 ft from the floor in each room to collect fresh dust. The six sampling collectors were positioned along the runway above the pen. Dust samples were collected from the different swine buildings at different times. In order to study odorous components adsorption characteristics, clean feed and Tenax were placed in the finishing building for three days in the sample collectors to adsorb odorous compounds. The feed is corn/soy blend with approximately 16% protein. Tenax is an inert, thermally stable synthetic and has a low affinity for water. It is widely used as a sampling medium for capturing organic gases because the adsorbed compounds can be removed by heating for analysis. All dust samples were transferred from collectors to vials and sealed with Teflon lined silicone caps inside the swine building in order to avoid the loss of compounds in the dust, then stored in a refrigerator @ 4°C prior to analysis. In the lab, approximately 0.5 g of each sample was weighed and transferred to a new vial for GC/FID analysis. The dust samples are listed in Table 1.

Table 1. Dust samples from Swine Research Center, UIUC.

RESULTS AND DISCUSSION

The gas chromatograms of all samples are listed in Figures 1-9. The total number of peaks in each gas chromatogram is summarized in Table 1, each peak representing a compound. All samples were thermally desorbed at 90°C, except for Tenax which was desorbed at 180°C as shown in Figures 7 and 9. This higher temperature was necessary to thoroughly desorb all compounds from Tenax. Figure 6 shows the same Tenax as Figure 7, but the desorption temperature was 90°C, resulting in a smaller number of peaks and lower peak size. A preliminary study was conducted to determine the desorption temperature for dust. A dust sample in a 22 ml headspace vials sealed with a Teflon lined silicone septum was inserted in a water bath of 90°C for one hour, then cooled down at room temperature for another hour, leaving dust with only a feed-like odor. A further test was conducted in Tekmar 7000/7050 Equilibrium Headspace Autosampler. A dust sample in a 22 ml headspace vials sealed with a Teflon lined silicone septum was heated to 90°C for 10 minutes. After cooling and removal of septum, the dust in the vial had only a feed-like odor. However, the septum still had the swine odor. These tests showed that 90°C was sufficient to desorb all odorous compounds from the dust. Comparisons of GC/FID chromatograms of dust and Tenax from various building types and seasonal operation are made and discussed as follows.

Finishing building vs. Growing building

Comparing the gas chromatogram of dust from the finishing building (Fig. 1) with that from the growing building (Fig. 2), the major compounds are the same according to the peak retention times although the total peak areas are different (Table 2). For the DB-5 column, the gas chromatogram of dust from the finishing building had 74 peaks while the gas chromatogram of dust from the growing building had 87 peaks. Whereas for the DB-WAX column, the gas chromatogram of dust from the finishing building had 106 peaks while the gas chromatogram of dust from the growing building had 90 peaks. This shows that the finishing building and the growing building have similar compounds adsorbed on the dust during winter operation.

Indole family compound standards were run on the GC/FID system, too. For the DB-5 column, indole family compounds had retention times greater than 22 minutes. However, in the gas chromatograms of dust from swine buildings, all major compounds have retention times less than 22 minutes. This means that indolic compounds are not associated with the dust.

Table 2. Comparisons of major compound peak areas (counts) in dust between finishing building and growing building during winter operation for the DB-5.

Summer operation vs. Winter operation

Comparing the gas chromatogram of dust from finishing building during summer operation (Fig. 3) with the gas chromatogram of dust from the same building during winter operation (Fig. 1), the major compounds are similar, but the levels for some compounds are different, as shown in Table 3. For example, for the compound with retention time of 16.61 min, it is 31,000 counts for winter operation, but 2,000 counts for summer operation. Most of the peak size (counts) of the major compounds in the dust during winter operation are higher than those during summer operation. This may reflect some change in odor and its intensity with the seasonal changes of operation. Also, a few of the compound peak sizes are greater during summer operation compared to winter operation (RT = 6.99, 11.30, 15.14, 18.75 min). This may be a result of the higher temperature during summer operation causing more volatilization of these compounds from the waste.

Figure 1. DB-5 gas chromatogram of the volatile compounds in the dust from the finishing building during winter operation.

Figure 2. DB-5 gas chromatogram of the volatile compounds in the dust from the growing building during winter operation.

Figure 3. DB-5 gas chromatogram of the volatile compounds in the dust from the finishing building during summer operation.

Table 3. Comparisons of major compound peak areas (counts) in dust from finishing building between winter operation and summer operation for DB-5.

Components with different retention time (min)	Winter operation (counts)	Summer operation (counts)
2.37	127,000	24,000
2.54	108,000	13,000
3.09	16,000	6,000
3.76	18,000	13,000
3.88	16,000	12,000
4.51	54,000	25,000
6.99	6,000	19,000
7.55	204,000	152,000
10.76	11,000	1,000
11.30	11,000	68,000
14.36	37,000	1,000
15.14	5,000	24,000
16.67	31,000	2,000
18.75	3,000	43,000

Clean Feed vs. Feed exposed to Swine Odor

Comparing the gas chromatogram of feed from the finishing building (Fig. 5) with the gas chromatogram of clean feed (Fig. 4), clean feed has far fewer peaks than feed exposed to swine odor. This means that the feed has adsorbed some compounds after three days of exposure in the swine house. We found four major compounds with retention times of 2.78 min, 2.88 min, 3.01 min and 3.31 min present in both chromatograms. This means that these compounds are associated with feed, not the swine odor. A comparison of the gas chromatogram of feed from finishing building (Fig.5) with the gas chromatogram of winter dust (Fig.1) shows that eighteen major compounds are the same. This means that feed, a source of dust, adsorbed most of these compounds from the swine building. Longer exposure of clean feed to swine odor was not tested, but it may adsorb additional compounds.

Figure 4. DB-5 gas chromatogram of the volatile compounds in the feed without exposure to swine odor.

Figure 5. DB-5 gas chromatogram of the volatile compounds in the feed from finishing building during winter operation.

Different desorption temperature for Tenax

As mentioned previously, Tenax is an inert, thermally stable synthetic and the adsorbed compounds can be removed by heating for analysis. A high temperature is critical for desorption of some odor compounds. In this study, we tested two temperatures, 90°C and 180°C as shown in the following chromatograms (Figures 6 and 7).

Figure 6. DB-5 gas chromatogram of the volatile compounds of the Tenax from the finishing building during winter operation (desorbed at 90°C).

Figure 7. DB-5 gas chromatogram of the volatile compounds of the Tenax from the finishing building during winter operation (at 180°C).

Both gas chromatograms show that many more compounds desorb at 180?C than at 90?C. Also, larger amounts of volatile fatty acids (VFA) adsorbed to the Tenax than to dust or feed as shown by the shark fin shape of the peaks present in these gas chromatograms. For better VFA peak shapes and peak resolution, a comparison of the DB-WAX chromatograms is necessary.

Finishing winter dust vs. Tenax (DB-WAX)

Comparing the DB-WAX gas chromatogram of Tenax from the finishing building during winter operation (Fig. 9) with the gas chromatogram of dust from the same building during winter operation (Fig. 8), it is clear that many more compounds adsorbed on the Tenax than the dust. The DB-WAX gas chromatogram of Tenax from the finishing room has 203 peaks while the gas chromatogram of dust from the same building has only 106 peaks (Table 1.). Note that a larger scale was used to accommodate the large peak sizes in the DB-WAX gas chromatogram of Tenax. Large amounts of VFA (retention time between 21 and 29 minutes) and p-cresol (retention time = 36.3 minutes) are detected from the Tenax compared to the dust. Tenax is a good sampling medium to adsorb various compounds for odor analysis in swine buildings. However, if swine odor is associated with dust, then the additional compounds adsorbed by Tenax may not be important with regards to swine odor and its control.

Figure 8. DB-WAX gas chromatogram of the volatile compounds in the dust from the finishing building during winter operation.

Figure 9. DB-WAX gas chromatogram of the volatile compounds of the Tenax from the finishing building during winter operation (at 180°C).

CONCLUSIONS

Dust particles collected from swine buildings have a strong swine odor. Gas chromatography equipped with a flame ionization detector has successfully separated the compounds adsorbed on the dust. The initial gas chromatogram results show that there are approximately 70 to 100 volatile compounds adsorbed on the dust although there is a small difference in the total number of compounds for different buildings operating during different seasonal operation.

Although all compounds are not identified, a comparison of the gas chromatograms shows the major compounds of dust from the finishing building and the growing building are the same according to the peak retention time. The major compounds of dust from the finishing room during the summer operation are also the same as those during winter operation, but the concentration levels are different. This may reflect some change in odor and its intensity with seasonal changes of operation.

A comparison of the gas chromatograms of Tenax with dust and feed reveals a large amount of VFA and p-cresol adsorbed to the Tenax, but not the dust or feed. A comparison with the indole family shows that no indolic compounds are associated with the Tenax, dust or feed. In addition, many more compounds adsorbed on the Tenax than on the dust.

All other compounds will be identified by mass spectrometry in the future.

ACKNOWLEDGEMENTS

The authors thank John Jerrell for his technical assistance in analyzing the dust samples. Also we thank Dr. Ed Perkins for use of the GC/FID. Finally, we would like to thank Mr. Bill Fisher for his assistance at the Swine Research Center, UIUC.

REFERENCES

Burnett, W.E. 1969. Odor transport by particulate matter in high density poultry houses. Poultry Science 48:182-185.

Eby, H.J., and G.B. Willson. 1969. Poultry house dust, odor and their mechanical removal. pp. 303-309. In: Animal waste management. Proceedings, Cornell university Conference on agricultural waste management

Day, D.L., E.L. Hansen, and S. Anderson. 1965. Gases and odors in confinement buildings. Transactions of the ASAE, Vol. 8: 118-121.

Hammond, E.G., C. Fedler and G. Junk. 1979. Identification of dust-borne odors in swine confinement facilities. Transactions of ASAE, Vol. 22:1186-1189.

Mackie, R.I., P.G. Stroot and V.H. Varel. 1998. Biochemical identification and biological origin of key odor components in livestock waste. J. Animal Science: 76:1331-1342.

O'Neill, D.H. and V.R. Phillips. 1992. A review of the control of odour nuisance from livestock buildings: part 3, properties of the odorous substances which have been identified in livestock waste or in the air around them. J. Agric. Engng. Res. 53:23-50.