Emission Characteristics of Odorous Compounds from a Swine Farm on Jeju Island, Korea

: This study investigated 26 malodorous substances emitted from a swine farm on Jeju Island, South Korea, to discern their specific emission characteristics and potential implications for workers’ health and environmental management. A detailed analysis of emissions from livestock buildings, the compost facility, and the manure storage tank was conducted. Accurate quantification involved rigorous collection methods measuring concentrations of NH 3 , hydrogen sulfide (H 2 S), trimethylamine (TMA), aldehyde compounds, volatile organic compounds (VOCs), volatile fatty acids (VFAs), p-cresol, indole, and skatole. High concentrations of NH 3 and H 2 S, particularly in the manure storage tank, raised concerns about the health of workers. TMA levels were notably elevated in the livestock building, whereas aldehydes and VOCs remained within limits. VFAs were prevalent in the livestock building, with p-cresol, indole, and skatole in the manure storage tank. Distinct emission profiles across farm facilities highlight the need for tailored odor management strategies, ensuring worker well-being and effective environmental practices. These findings offer valuable insights for implementing targeted mitigation measures in similar agricultural settings


Introduction
The livestock industry is rapidly developing around the world.Jeju Island has become a significant hub for livestock husbandry, with huge impacts on the local economy.Consequently, the number of livestock and swine facilities has increased, leading to a rise in odor emissions from manure, which has evolved into a local human and environmental issue.Livestock emissions represent a serious environmental issue on Jeju Island and globally.
Odors are composed of volatile compounds that stimulate the human sense of smell and can result in discomfort and disgust.Furthermore, the detection of even minute quantities of specific odorous substances poses a challenge in addressing their impact on odor, thereby complicating mitigation efforts.Addressing and preventing odors poses numerous difficulties.Individuals vary in their olfactory sensitivity, making it challenging to accurately assess the quality and intensity of odors through sensory methods.Specifically, odors originating from pigsties can induce mental and physiological stress in humans, resulting in adverse reactions such as nausea, headache, loss of appetite, breathing difficulties, and allergic phenomena [1,2].
Malodorous substances from swine manure encompass hundreds of compounds, including nitrogen compounds such as ammonia (NH 3 ) and amines, sulfurous compounds such as hydrogen sulfide (H 2 S) and dimethyl sulfide (DMS), esters, ketones, and aromatic compounds [3].NH 3 is a neurotoxin with strong negative effects on the health of animals, humans, and the environment.At high concentrations, it can cause ulceration in the eyes and severe irritation to the respiratory tract [4].Additionally, atmospheric H 2 S concentrations > 10 ppm are considered stressors for both humans and swine.For example, H 2 S gas exposure can lead to neurological, respiratory, and eye diseases in animals and humans [5,6].
Odors from swine farms are principally generated by feed digestion and manure fermentation.The main components of swine feed are carbohydrates, crude protein, crude fat, crude ash, neutral detergent fiber, acid detergent fiber, non-fiber carbohydrates, and nitrogen-free extract.Among these components, crude protein is decomposed into amino acids by intestinal microorganisms, which in turn is broken down into NH 3 , volatile fatty acids (VFAs), hydrogen, and carbon dioxide by the deamination of amino acids [7,8].Furthermore, amino acids such as tyrosine, tryptophan, and phenylalanine are metabolized to generate the main components of manure odors such as indole (IND), phenol (PHE), p-cresol (p-CRE), and 4-ethyl phenol [7][8][9].
Swine farms contain livestock buildings, manure storage tanks, manure composting facilities, and liquid manure treatment facilities, and diverse types and intensities of odors are generated in these facilities.Consequently, the management of odors in each facility and the construction of odor reduction systems on a swine farm demand significant expenditure in terms of costs, labor, and time [3].
In Korea, 22 target offensive odorants have been officially specified for the management of odor emissions in industrial and surrounding areas.These 22 malodorous substances are regulated based on the permissible emission standards set by the Odor Prevention Law, with a particular focus on sulfur compounds, NH 3 , volatile amines, VOCs, aldehydes, and VFAs [15].However, PHEs and INDs, which are the main malodorous substances generated from swine farms, are excluded, making it difficult to manage livestock odors.
On Jeju Island, 259 swine farms were operating in 2022, with farms with <3000 swine accounting for 85% (220 swine farms) of this total.By region, Hallim-eup, Jeju City, has 128 swine farms, accounting for 49% of the total.As there are numerous swine farms in this small area and as the number of livestock has increased, odor complaints have increased accordingly.
To achieve the sustainable development of the livestock industry globally, systematic livestock odor management is required to solve air quality deterioration, health issues, and odor complaints.Consequently, this research focused on swine farms on Jeju Island, characterized by an average breeding scale within a region exhibiting a dense distribution of swine farms.To achieve this objective, samples were collected and analyzed for malodorous substances.A comprehensive set of 26 substances, including 22 malodorous compounds specified by the Korean Ministry of Environment, two types of PHEs, and two types of INDs, were examined.These samples were derived from a swine farm comprising a livestock building, a compost facility, and a manure storage tank.The analysis aimed to identify the distinctive characteristics of the primary malodorous substances associated with each facility and their respective contributions to odor.

Sampling Sites and Substances
This study was performed at a commercial swine facility on Jeju Island (33 • 36 ′ N, 126 • 31 ′ E), located in Geumak-ri, Hallim-eup, Jeju City, South Korea.The swine farm comprised approximately 350 sows, which produce 4000-5000 market pigs (i.e., 100~110 kg per pig) per year.The swine farm comprised various buildings, including thirteen pig houses, two manure treatment facilities (a compost facility and manure storage tank), and management/administration offices.The total area of the swine farm was approximately 4200 m 2 .In addition, the total area of the pig house structures, the compost facility, and manure storage were 2800, 495, and 330 m 2 , respectively.Each pig house was a closed structure constructed with concrete materials, devoid of windows, and operated using a deep-pit manure removal system.Additionally, the buildings had fully slatted floors.Approximately 400-500 pigs are reared in each pig house.The volume of the manure storage tank was 5000 m 3 , which was operated using an oxygen aeration system, and manure was transferred to the tank from the pig house.The water level in the manure storage tank was maintained at 60-70%.

Sampling Method
Diverse methods were applied to collect samples of 26 malodorous substances from the swine facility.First, absorption solutions were used to collect NH 3 , TMA, and VFAs (PA, n-BA, iso-VA, n-VA) with a low-volume air sampler (Yotsubishi Corp., KP-10O, Tokyo, Japan).The absorption solutions used were 0.5% boric acid for NH 3 , 0.1 M sulfur acid for TMA, and a 0.1 M NaOH absorption solution for VFAs.

Analysis Method
Analytical methods for determining various components in air samples and absorption tubes were based on a preconcentration step followed by subsequent separation and detection using gas chromatography, whereas absorption solutions were analyzed using a UV/vis spectrophotometer.
NH 3 was collected and absorption solutions were analyzed at 640 nm using a UV/vis spectrophotometer (Shimadzu Corp., UV-1280, Kyoto, Japan).TMA was analyzed using the Headspace System (PerkinElmer Inc., Turomatrix 40, Shelton, CT, USA) and GC-NPD (PerkinElmer Inc., Clarus 690, Shelton, CT, USA).Sulfur compounds were analyzed using the thermal desorber system (Markes International Ltd., Unity-xr/Air Server, Bridgend, UK) and GC-FPD (PerkinElmer Inc., Clarus 690, Shelton, CT, USA).Aldehydes were analyzed using a high-performance liquid chromatograph (HPLC) coupled with a photodiode array detector (Waters Corp., e2695/2998, Milford, MA, USA) at a 360 nm absorption wavelength.VOCs, PHEs, and INDs were analyzed using GC/MSD (PerkinElmer Inc., Clarus 690/Clarus SQ8T, Shelton, CT, USA) connected to a thermal desorber system (PerkinElmer Inc., Turbomatrix 650, Shelton, CT, USA).VFAs were analyzed using the Headspace System (PerkinElmer Inc., Turomatrix 40, CT, USA), and GC/MSD (PerkinElmer Inc., Clarus 680/Clarus SQ8T, Shelton, CT, USA) was used for the analysis of TMA.The analytical conditions of these components are listed in Table 2, and the reliability of the analysis is presented in Table 3, including the method detection limit (MDL) and coefficient of variation (CV), as specified in the Odor Prevention Law of the Korean Ministry of Environment [15].

Nitrogen Compounds
The results for the NH 3 components measured in the samples collected from the livestock building (nursery, growing, and finishing pig houses), compost facility, and manure storage tank in the investigated swine farm on Jeju Island are shown in Figure 1.High concentrations of NH 3 were observed in the following order: manure storage tank (373.4 ± 191.4 ppm) > nursery pig house (15.3 ± 4.0 ppm) > finishing pig house (12.3 ± 3.3 ppm) > growing pig house (12.1 ± 5.1 ppm) > compost facility (10.4 ± 7.9 ppm).The manure storage tank exhibited the highest NH 3 concentration (373.4 ppm), which was far above the short-term exposure limit (STEL) concentration of 35 ppm set by the Korean Ministry of Environment and the American Conference of Governmental Industrial Hygienists (ACGIH).Exposure to an NH 3 concentration exceeding 100 ppm can result in irritation to the eyes, nose, and skin, emphasizing the importance of managing concentrations with due regard to worker health.Additionally, NH 3 generated from the manure storage tank is likely to affect surrounding areas; its concentration in the rest of the livestock building and the compost facility was 10.4-15.3ppm, with a level similar to that of the NH 3 concentration in a general swine farm [16,17].
Atmosphere 2024, 12, x FOR PEER REVIEW 6 of 14 pig house, and finishing pig house, whereas the NH3 concentration was high and that of TMA was relatively low in the manure storage tank.In the livestock building (i.e., nursery, growing, and finishing pig houses), the correlation coefficient (r) between the NH3 and TMA was 0.75, indicating a good correlation; this result may have been due to urea decomposition in the intestines of the livestock, which results in the generation of these two components.

Sulfur Compounds
The concentrations of the main sulfur-based malodorous substances such as H2S, CH3SH, DMS, and DMDS were measured in the livestock building, compost facility, and TMA concentrations were observed in the following order: growing pig house (6.5 ± 1.9 ppb) > nursery pig house (6.4 ± 1.3 ppb) > finishing pig house (5.7 ± 2.4 ppb) > manure storage tank (1.3 ± 0.6 ppb) > compost facility (1.1 ± 0.6 ppb; Figure 2).The TMA concentrations were similar in the livestock building, including the growing pig house, nursery pig house, and finishing pig house, whereas the NH 3 concentration was high and that of TMA was relatively low in the manure storage tank.In the livestock building (i.e., nursery, growing, and finishing pig houses), the correlation coefficient (r) between the NH 3 and TMA was 0.75, indicating a good correlation; this result may have been due to urea decomposition in the intestines of the livestock, which results in the generation of these two components.
Atmosphere 2024, 12, x FOR PEER REVIEW 6 of 14 pig house, and finishing pig house, whereas the NH3 concentration was high and that of TMA was relatively low in the manure storage tank.In the livestock building (i.e., nursery, growing, and finishing pig houses), the correlation coefficient (r) between the NH3 and TMA was 0.75, indicating a good correlation; this result may have been due to urea decomposition in the intestines of the livestock, which results in the generation of these two components.

Sulfur Compounds
The concentrations of the main sulfur-based malodorous substances such as H2S, CH3SH, DMS, and DMDS were measured in the livestock building, compost facility, and

Sulfur Compounds
The concentrations of the main sulfur-based malodorous substances such as H 2 S, CH 3 SH, DMS, and DMDS were measured in the livestock building, compost facility, and manure storage tank, and the results were compared (Figure 3).H 2 S (63,915.1 ppb) and CH 3 SH (227.4 ppb) showed the highest concentrations in the manure storage tank; the concentrations were likely high because the manure undergoes anaerobic decomposition with an oxygen aeration system.H 2 S is detectable by its odor at 0.01-0.7 ppm, irritates the eyes and respiratory tract with an exposure of 50-100 ppm for 1 h, can be fatal in the case of exposure for 8-48 h at a concentration of 150 ppm, and causes rapid death at an exposure of 700-2000 ppm [18,19].Therefore, considering the health of workers in manure storage tanks is necessary [19].
In the manure storage tank, if the H2S concentration is between 50 and 100 ppm, eye and upper respiratory irritations, headaches, nausea, vomiting, and diarrhea may occur; the exposure of workers should be carefully managed.The concentrations of H2S and CH3SH reached their lowest levels in the compost facility, with values of 60.9 and 2.9 ppb, respectively.This reduction can be attributed to the anaerobic decomposition of manure in that specific area.In the rest of the livestock building, the concentrations of H2S and CH3SH were 1050.0-2186.0 and 18.8-22.6ppb, respectively, similar to the concentrations in livestock buildings in other general farms [20][21][22].Moreover, DMS and DMDS were detected below the emission limit value of 10 and 9 ppb, respectively, set by the Korean Ministry of Environment.These components were not considered the main malodorous substances generated from the swine farm.
In the livestock building, compost facility, and manure storage tank, the r values of H2S and CH3SH, DMS, and DMDS were 0.96, 0.82, and 0.65, respectively, indicating a good correlation, probably because these components had the same origin.

Aldehyde Compounds
Figure 4 shows the results of the analysis for aldehyde compounds such as ACHO, PCHO, BCHO, iso-VCHO, and n-VCHO.The livestock building, compost facility, and manure storage tank had ACHO and PCHO concentrations of 8.5-28.8 and 1.3-52 ppb, respectively; however, these concentrations were lower than the emission limit value set by the Ministry of Environment (50 ppb).Additionally, BCHO, iso-VCHO, and n-VCHO were not detected.Consequently, aldehyde compounds were not considered principal malodorous substances at the swine farm.In the manure storage tank, if the H 2 S concentration is between 50 and 100 ppm, eye and upper respiratory irritations, headaches, nausea, vomiting, and diarrhea may occur; the exposure of workers should be carefully managed.The concentrations of H 2 S and CH 3 SH reached their lowest levels in the compost facility, with values of 60.9 and 2.9 ppb, respectively.This reduction can be attributed to the anaerobic decomposition of manure in that specific area.In the rest of the livestock building, the concentrations of H 2 S and CH 3 SH were 1050.0-2186.0 and 18.8-22.6ppb, respectively, similar to the concentrations in livestock buildings in other general farms [20][21][22].Moreover, DMS and DMDS were detected below the emission limit value of 10 and 9 ppb, respectively, set by the Korean Ministry of Environment.These components were not considered the main malodorous substances generated from the swine farm.
In the livestock building, compost facility, and manure storage tank, the r values of H 2 S and CH 3 SH, DMS, and DMDS were 0.96, 0.82, and 0.65, respectively, indicating a good correlation, probably because these components had the same origin.

Aldehyde Compounds
Figure 4 shows the results of the analysis for aldehyde compounds such as ACHO, PCHO, BCHO, iso-VCHO, and n-VCHO.The livestock building, compost facility, and manure storage tank had ACHO and PCHO concentrations of 8.5-28.8 and 1.3-52 ppb, respectively; however, these concentrations were lower than the emission limit value set by the Ministry of Environment (50 ppb).Additionally, BCHO, iso-VCHO, and n-VCHO were not detected.Consequently, aldehyde compounds were not considered principal malodorous substances at the swine farm.

Volatile Fatty Acids (VFAs)
VFAs are produced in the dissolution process of proteins and carbohydrates.In the digestive tract, a neutral pH (pH 6-7) is typical; however, VFAs occur from the deamination of amino acids [23].Miller and Varel [24] reported that VFAs or aromatic substances were the main contributors to swine manure odor.
VFAs, including PA, n-BA, iso-VA, and n-VA, were analyzed and their concentrations were compared (Figure 6).PA (231.9 ± 81.0 ppb) and iso-VA (28.9 ± 23.8 ppb) exhibited the highest concentrations in the growing pig house, and n-BA (194.6 ± 94.1 ppb) and n-VA (35.8 ± 19.5 ppb) had the highest concentrations in the finishing pig house.The VFA components had the lowest concentrations in the manure storage tank.
were the main contributors to swine manure odor.
VFAs, including PA, n-BA, iso-VA, and n-VA, were analyzed and their concentrations were compared (Figure 6).PA (231.9 ± 81.0 ppb) and iso-VA (28.9 ± 23.8 ppb) exhibited the highest concentrations in the growing pig house, and n-BA (194.6 ± 94.1 ppb) and n-VA (35.8 ± 19.5 ppb) had the highest concentrations in the finishing pig house.The VFA components had the lowest concentrations in the manure storage tank.
The r values among VFA components were >0.90 in the livestock building, compost facility, and manure storage tank, demonstrating a good correlation because they had the same origin.The concentrations of VFAs were higher in the livestock building than in the compost facility and manure storage tank because of the leftover feed and high temperature in the livestock building, which causes carbohydrates and proteins in the manure to undergo catabolism and initiates anaerobic degradation processes [25].

Phenolic and Indole Compounds
PHE and PHE compounds such as p-CRE occur during the bacterial degradation of amino acids such as tyrosine and phenylalanine in the animal intestine [26].The metabolism of tryptophan produces IND acetate, which is converted to SKT (3-methyl IND) and IND by several types of bacterial flora [10].
The concentration of PHE was prevalent in the following order (Figure 7): growing pig house (12.4 ± 4.8 ppb) > finishing pig house (11.4 ± 4.8 ppb) > nursery pig house (6.4 ± 1.5 ppb) > manure storage tank (5.0 ± 3.7 ppb) > compost facility (2.9 ± 2.2 ppb).The PHE concentration was high in the livestock building.However, p-CRE had a high concentration in the manure storage tank, while showing a concentration pattern in the following order: manure storage tank (158.8 ± 198.1 ppb) > finishing pig house (146.2 ± 68.5 ppb) > growing pig house (117.7 ± 43.7 ppb) > nursery pig house (73.8 ± 29.3 ppb) > compost facility (12.7 ± 10.5 ppb); these results indicate that PHE and p-CRE components had different patterns.The r values among VFA components were >0.90 in the livestock building, compost facility, and manure storage tank, demonstrating a good correlation because they had the same origin.The concentrations of VFAs were higher in the livestock building than in the compost facility and manure storage tank because of the leftover feed and high temperature in the livestock building, which causes carbohydrates and proteins in the manure to undergo catabolism and initiates anaerobic degradation processes [25].

Phenolic and Indole Compounds
PHE and PHE compounds such as p-CRE occur during the bacterial degradation of amino acids such as tyrosine and phenylalanine in the animal intestine [26].The metabolism of tryptophan produces IND acetate, which is converted to SKT (3-methyl IND) and IND by several types of bacterial flora [10].
facility (Figure 8).The PHE, p-CRE, IND, and SKT components had low MDL concentrations at 0.28, 0.054, 0.30, and 0.0056 ppb, respectively.As SKT has a lower MDL compared to other components, it can trigger displeasure even at low concentrations when perceived by olfactory sensors.

Estimation of Odor-Causing Substances According to Pigsty Type
As malodorous substances exhibit distinct threshold limit values for each component, assessing the extent of their contribution to odor relies on the concentration of detected malodorous substances [27,28].Primary odor-causing substances can be predicted by calculating the odor quotient (OQ).The OQ is derived by dividing the concentration The IND and SKT components had highest concentrations in the manure storage tank at 5.9 and 100.6 ppb, respectively, and had the lowest concentrations in the compost facility (Figure 8).The PHE, p-CRE, IND, and SKT components had low MDL concentrations at 0.28, 0.054, 0.30, and 0.0056 ppb, respectively.As SKT has a lower MDL compared to other components, it can trigger displeasure even at low concentrations when perceived by olfactory sensors.

Estimation of Odor-Causing Substances According to Pigsty Type
As malodorous substances exhibit distinct threshold limit values for each component, assessing the extent of their contribution to odor relies on the concentration of detected malodorous substances [27,28].Primary odor-causing substances can be predicted by calculating the odor quotient (OQ).The OQ is derived by dividing the concentration of each individual malodorous substance, as determined through instrumental analysis using the threshold limit value for that particular substance, by the sum of the odor quotients (SOQ) [29].Here, threshold limit values refer to the data provided by the Korean Ministry of Environment [4].PHE, p-CRE, IND, and SKT have threshold limit values of 0.28, 0.054, 0.30, and 0.0056 ppb, respectively [23].If the OQ is >10, a weak odor is perceived, but if it is >100, a strong odor is perceived.Therefore, components with an OQ of 100 or more can be considered major odor-causing substances [30].
Odor Quotient(OQ) = Odor concentration(ppb) Threshold limit value(ppb) Sum of Odor Quotient(SOQ) = ∑ Odor Quotient (OQ) Odor Contribution (%) = OQ SOQ × 100 The computed OQ and SOQ values in the livestock building (nursery, growing, and finishing pig houses), compost facility, and manure storage tank are compared in Table 4.The results of the calculated odor contributions are presented in Figure 8. First, a comparison of the SOQ values of each facility indicated the following order of odor intensity: manure storage tank > finishing pig house > growing pig house > nursery pig house > compost facility, indicating that the intensity was the highest in the manure storage tank.Furthermore, a comparison of the odor index per livestock building indicated that H 2 S showed the highest odor index at the nursery, growing, and finishing pig houses, followed by p-CRE, SKT, and n-BA.The main malodorous substances (OQ > 100) in the livestock buildings were the same components, such as H 2 S, p-CRE, SKT, n-BA, iso-VA, CH 3 SH, n-VA, TMA, and NH 3 .Sulfur compounds showed the highest odor contribution (30.9-52.5%) in the livestock buildings, followed by PHEs, VFAs, INDs, and nitrogen compounds, accounting for more than 99% of the total.Therefore, five types of aldehyde compounds and seven types of VOCs were not considered key malodorous substances.
As shown in Figure 8, SKT, p-CRE, iso-VA, n-BA, H 2 S, n-VA, and NH 3 were confirmed to be the primary malodorous substances (OQ > 100) in the compost facility, and SKT, which is an IND, showed the highest odor index.In the compost facility, contributions of VFAs, PHEs, INDs, sulfur compounds, and nitrogen compounds were 38.3, 18.2, 18.2, 14.2, and 10.3%, respectively.
The H 2 S component had the highest odor quotient in the manure storage tankespecially H 2 S and SKT, which generated strong odors with an odor quotient of over 10,000.The main malodorous substances were confirmed to be H 2 S, SKT, NH 3 , CH 3 SH, p-CRE, and iso-VA.Sulfur compounds showed the highest odor contribution (86.4%), followed by INDs and nitrogen compounds.

Conclusions
This study investigated the characteristics of malodorous substances generated from a livestock building (nursery, growing, and finishing pig houses), a compost facility, and a manure storage tank on a swine farm located in a region with high concentrations of swine farms on Jeju Island.A total of 26 malodorous substances, including 22 malodorous substances designated by the Korean Ministry of Environment, two types of PHEs, and two types of INDs, which are known as key malodorous substances in swine farms, were collected and analyzed.
The concentration of NH 3 in the manure storage tank was the highest, and it caused irritation to the eyes, nose, and skin, requiring environmental and health care for workers.TMA exhibited a high concentration in the growing pig house.Four types of sulfur compounds exhibited the highest concentrations in the manure storage tank; H 2 S was at levels that irritate the eyes and respiratory tract of workers.Aldehyde compounds and VOCs were not detected or were below the emission limits set by the Ministry of Environment; they were thus not considered key malodorous substances on swine farms.VFAs exhibited high concentrations in the livestock building, but low concentrations in the manure storage tank.High concentrations of p-CRE, IND, and SKT were observed in the manure storage tank, but had low concentrations in the compost facility.
Swine farms on Jeju Island mainly target and manage NH 3 and H 2 S.However, in livestock buildings, sulfur compounds most significantly contribute to odor emissions, followed by VFAs, PHEs, and INDs-all of which contribute more than nitrogen compounds.In the compost facility, the contributions of VFAs, PHEs and INDs surpassed those of nitrogen or sulfur compounds, underscoring the need for the effective management of VFAs, PHEs, and INDs.Furthermore, in the manure storage tank, sulfur compounds accounted for 86.4% of the odor contribution, emphasizing the more urgent need for targeted odor management related to a series of sulfur compounds compared to other components.These findings highlight the variability in the types and quantities of odors generated depending on the specific facility within a swine farm.Therefore, we recommend tailoring odor management strategies on swine farms based on the unique characteristics of each facility and the source of emissions.

Figure 1 .
Figure 1.Comparisons of ammonia concentrations in the nursery pig house, growing pig house, finishing pig house, compost facility, and manure storage tank (n = 4).

Figure 2 .
Figure 2. Comparisons of TMA concentrations in the nursery pig house, growing pig house, finishing pig house, compost facility, and manure storage tank (n = 4).

Figure 1 .
Figure 1.Comparisons of ammonia concentrations in the nursery pig house, growing pig house, finishing pig house, compost facility, and manure storage tank (n = 4).

Figure 1 .
Figure 1.Comparisons of ammonia concentrations in the nursery pig house, growing pig house, finishing pig house, compost facility, and manure storage tank (n = 4).

Figure 2 .
Figure 2. Comparisons of TMA concentrations in the nursery pig house, growing pig house, finishing pig house, compost facility, and manure storage tank (n = 4).

Figure 2 .
Figure 2. Comparisons of TMA concentrations in the nursery pig house, growing pig house, finishing pig house, compost facility, and manure storage tank (n = 4).

Figure 3 .
Figure 3. Comparisons of the concentrations of sulfur compounds in the nursery pig house, growing pig house, finishing pig house, compost facility, and manure storage tank (n = 4).

Figure 3 .
Figure 3. Comparisons of the concentrations of sulfur compounds in the nursery pig house, growing pig house, finishing pig house, compost facility, and manure storage tank (n = 4).

Figure 4 .
Figure 4. Comparisons of the concentrations of aldehyde compounds in the nursery pig house, growing pig house, finishing pig house, compost facility, and manure storage tank (n = 4).

Figure 5 .
Figure 5. Comparisons of VOC concentrations in the nursery pig house, growing pig house, finishing pig house, compost facility, and manure storage tank (n = 4).

Figure 4 .
Figure 4. Comparisons of the concentrations of aldehyde compounds in the nursery pig house, growing pig house, finishing pig house, compost facility, and manure storage tank (n = 4).

Figure 4 .
Figure 4. Comparisons of the concentrations of aldehyde compounds in the nursery pig house, growing pig house, finishing pig house, compost facility, and manure storage tank (n = 4).

Figure 5 .
Figure 5. Comparisons of VOC concentrations in the nursery pig house, growing pig house, finishing pig house, compost facility, and manure storage tank (n = 4).

Figure 5 .
Figure 5. Comparisons of VOC concentrations in the nursery pig house, growing pig house, finishing pig house, compost facility, and manure storage tank (n = 4).

Figure 6 .
Figure 6.Comparisons of VFA concentrations in the nursery pig house, growing pig house, finishing pig house, compost facility, and manure storage tank (n = 4).

Figure 6 .
Figure 6.Comparisons of VFA concentrations in the nursery pig house, growing pig house, finishing pig house, compost facility, and manure storage tank (n = 4).

Figure 7 .
Figure 7. Comparisons of phenolic and IND compound concentrations in the nursery pig house, growing pig house, finishing pig house, compost facility, and manure storage tank (n = 4).

Figure 8 .
Figure 8. Comparisons of odor contributions of different swine facilities and chemical components.

Figure 7 .
Figure 7. Comparisons of phenolic and IND compound concentrations in the nursery pig house, growing pig house, finishing pig house, compost facility, and manure storage tank (n = 4).

Figure 8 .
Figure 8. Comparisons of odor contributions of different swine facilities and chemical components.

Funding:
This work was supported by the Korea Institute of Planning and Evaluation for Technology in Food, Agriculture and Forestry (IPET) through the 2025 Livestock Industrialization Technology

Table 1 .
Basic information regarding the five sampling sites selected for the research of malodor composition in the investigated swine farm.

Table 2 .
Analytical conditions of instruments.

Table 3 .
Method detection limit (MDL) and coefficient of variation (CV) for the analysis of odorous compounds (n = 7).
* In ppb unless stated otherwise.

Table 4 .
Comparison of SOQ, OQ, and OC at the swine facilities.