Reduce Odor Emissions Research Articles

Typical Odor Mitigation Technologies for Swine Production Facilities - A Review

Odorous air emissions from confined animal feeding operation are causing public nuisance. Accordingly, different odor mitigation technologies were designed, developed, and evaluated in the last decades to reduce odor emissions. The purpose of this paper is to review the previous research related to odor mitigation from swine rearing facilities and provide information on the effectiveness of currently available and emerging odor mitigation technologies. This review focused on odor mitigation approaches at different stages of swine production, manure storage and handling, and land application. Several odor mitigation technologies have been suggested and evaluated including diet manipulation, solid-liquid separation, additives, aeration, anaerobic digestion, lagoon covers, biofilters, acid scrubbing, shelterbelts, and manure injection. The effectiveness of these mitigation technologies varied widely; however, diet manipulation, biofilters, shelterbelts, and direct injection of manure have shown advantages over other odor mitigation methods. Diet manipulation is the first line of defense for odor mitigation. Biofilters and shelterbelts provide solutions for treating the odorous air before releasing to atmosphere, whereas additives, lagoon covers, aeration, and anaerobic digestion reduce or control odor emissions during manure storage and treatment. Direct injection of manure provides ultimate disposal solution and can reduce odor significantly compared to surface application.

Annual Variations of Odor Concentrations and Emissions from Swine Gestation, Farrowing, and Nursery Buildings

ABSTRACT To obtain annual odor emission profiles from intensive swine operations, odor concentrations and emission rates were measured monthly from swine nursery, farrowing, and gestation rooms for a year. Large annual variations in odor concentrations and emissions were found in all the rooms and the impact of the seasonal factor (month) was significant (P < 0.05). Odor concentration was low in summer when ventilation rate was high but high in winter when ventilation rate was low, ranging from 362 (farrowing room in July) to 8934 (nursery room in December) olfactory unit (OU) m−3. This indicates that the air quality regarding odor was significantly better in summer than that in winter. Odor emission rate did not show obvious seasonal pattern as odor concentration did, ranging from 2 (gestation room in November) to 90 (nursery room in April) OU m−2 sec−1; this explains why the odor complaints for swine barns have occurred all year round. The annual geometric mean odor concentration and emission rate of the nursery room was significantly higher than the other rooms (P < 0.05). In order to obtain the representative annual emission rate, measurements have to be taken at least monthly, and then the geometric mean of the monthly values will represent the annual emission rate. Incorporating odor control technologies in the nursery area will be the most efficient in reducing odor emission from the farm considering its emission rate was 2 to 3 times of the other areas. The swine grower-finisher area was the major odor source contributing 53% of odor emission of the farm and should also be targeted for odor control. Relatively positive correlations between odor concentration and both H2S and CO2 concentrations (R 2 = 0.58) means that high level of these two gases might likely indicate high odor concentration in swine barns. IMPLICATIONS The emissions of air pollutants including odors, greenhouse gases, and toxic gases have become a major environmental issue facing animal farms in the U.S.A. and Canada. To ensure the air quality in the vicinity of intensive livestock farms, air dispersion models have been used to determine setback distances between livestock facilities and neighboring residences based on certain air quality requirement on odor and gases. Due to the limited odor emission data available, none of the existing models can take account of seasonal variations of odor emissions, which may result in great uncertainties in setback distance calculations. Therefore, the obtained seasonal odor and gas emission rates by this study can be used by the government regulatory organizations and researchers in air dispersion modeling to get improved calculation of setback distances.

On farm biogas production: A method to reduce GHG emissions and develop more sustainable livestock operations

We describe the potential contribution of on-farm biogas production to reducing greenhouse gas (GHG) emissions and other environmental impacts related to livestock operations. GHG are reduced by production of renewable energy as a substitute for fossil fuels via reduction of fugitive GHG emissions from stored and land applied manures, as well as by reduction in use of chemical fertilizers in crop production. Anaerobic digestion (AD) biotechnologies produce biogas at average rates of 0.30, 0.25 and 0.48L/g volatile solids from swine, bovine and poultry slurries, respectively. The biogas produced is of high quality with a CH4 concentration of 60–80%. AD may be an acceptable solution to management of P surplus by precipitating up to 25% of it in batch or semi-batch operated bioreactors, and by precipitating and concentrating up to 70% of bioreactor effluent P in long term storage bottom sludge. Effluents from AD are better balanced to meet crop needs than raw manure slurries, thereby reducing the need for supplementary chemical N and P fertilizers. Both capture of energy and reduced needs for chemical fertilizers will substantially decrease the C footprint of livestock food products. On-farm biogas production contributes to more sustainable livestock operations by substantially reducing other environmental impacts related to manure management. It reduces the risk of water pollution associated with animal manure slurries (i.e., eutrophication) by removing 0.80–0.90 of soluble chemical oxygen demand. In addition, some AD eliminate zoonotic pathogens and parasites in livestock manures. AD also improves human/farm cohabitation in rural regions by reducing odour emissions by 70–95%. This reduction allows more frequent and better timing of manure land application. Both timing of application and improved nutrient balance have the potential to increase nutrient uptake by crops and minimize nutrient losses to the environment. Reduction in the viability of weed seeds during AD reduces the need for herbicides and makes bioreactor effluent more acceptable to organic farmers. Inadequate regulatory polices and incentives are obstacles to widespread implementation of AD in developed and developing countries. However, adoption of AD is an alternative which could substantially reduce the C and environmental footprint of housed livestock operations.This article is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors; K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.

Vegetative Environmental Buffers and Exhaust Fan Deflectors for Reducing Downwind Odor and VOCs from Tunnel-Ventilated Swine Barns

Scientists have investigated methods for reducing odor emissions from livestock buildings for decades, yet few technologies have proven effective. Vegetative environmental buffers (VEB), which are specially designed combinations of trees, shrubs, and grasses, have shown promise in recent years for reducing odors at poultry operations, but they have seen less testing at swine farms. A field research project was conducted at two similar 8-barn swine finisher sites in Missouri to assess the effectiveness of VEBs in combination with fan deflectors for reducing downwind odor impacts from tunnel-ventilated swine barns. A VEB and fan plume deflectors were installed in spring 2009 at one 8-barn site, while the other site, with neither VEB nor fan plume deflectors, served as the control. Odor was monitored from July to November 2009, with trained human panelists at eight locations, upwind and downwind of the VEB, barns, and lagoons. Five aromatic volatile organic compounds (VOCs: phenol, 4-methylphenol, 4-ethylphenol, indole, skatole) were sampled from ambient air using sorbent tubes and gas chromatography/mass spectrometry. Compared to the control site, the VEB reduced odor concentrations (dilutions to threshold, D/T) by 49.1% in the VEB and by 66.3% at distance 15 m downwind of the VEB (p < 0.001). There was a larger percentage of non-detect odor concentrations (D/T < 2) at 15 m downwind for the VEB site (57.6%) as compared to the control site (16.4%). Mean upwind odor concentrations ranged from 1.4 to 2.4 D/T. Mean odor concentrations at the 150 m downwind location were not significantly different for the control (mean DT = 3.0) and the VEB site (mean DT = 3.5) (p = 0.42). Mean odor concentrations at 300 m downwind were not significantly different for the control (mean DT = 2.3) and the VEB site (mean DT = 2.5) (p = 0.47). In late 2010, a laboratory wind tunnel was used to compare VOC flux from VEB vegetation samples before and after rinsing. Wind tunnel VOC fluxes from vegetation were 78% to 98% lower after rinsing, qualitatively showing that particulate matter (PM) captured on the vegetation reduces VOC emissions. The results of these field and laboratory experiments confirm that VEBs reduce downwind odor within 30 m of the barn or 15 m from the VEB by increasing dilution and capturing odorous PM in the vegetation.

Evaluation of Biological Air Filters for Livestock Ventilation Air by Membrane Inlet Mass Spectrometry

Biological air filters have been proposed as a cost-effective technology for reducing odor emissions from intensive swine production facilities. In this work we present results from the application of membrane inlet mass spectrometry (MIMS) for continuously monitoring the removal of odorous compounds in biological air filters. The sensitivity and selectivity were tested on synthetic samples of selected odorous compounds, and linearity and detection limits in the lower ppb range were demonstrated for all compounds tested (methanethiol, dimethyl sulfide, carboxylic acids, 4-methylphenol, aldehydes, indole, and skatole) except trimethylamine. The method was applied in situ at two full-scale filters installed at swine houses. The results have been compared with analyses by thermal desorption gas chromatography-mass spectrometry (TD-GC/MS), and odor was measured by olfactometry. By comparison with TD-GC/MS, observed MIMS signals were assigned to 4-methylphenol, 4-ethylphenol, indole, skatole, the sum of volatile reduced organic sulfur compounds (ROS), and three subgroups of carboxylic acids. The removal rates were observed to be related to air-water partitioning with removal efficiencies in the range of 0 to 50% for low-soluble organic sulfur compounds and high removal efficiencies (typically 80-100%) for more soluble phenols and carboxylic acids. Based on the results and published odor threshold values, it is estimated that the low removal efficiency of ROS is the main limitation for achieving a higher odor reduction.

A Two-Airspace Building Design to Reduce Odor and Ammonia Emissions

Emissions from the barn ventilation system and manure storage facilities constitute two continuous sources of gas and odor emissions from pig facilities. In Canada, swine manure is generally stored outside the barn to minimize the risk of worker and animal exposure to hydrogen sulfide during manure agitation and to reduce construction costs. However, storing swine manure in the barn would decrease the number of continuous emission sources from two to one. By having two separate airspaces in the building consisting of a main airspace and an enclosed dunging area (EDA), swine manure can be stored within the barn with reduced risk. Gas transfer from the manure storage to the EDA and the building emissions would be reduced if the EDA exhaust air is treated. Preliminary experiments were conducted to determine a basic design for a functioning EDA: type and width of doorway and equipment necessary to minimize the time spent by the pigs in the EDA. The EDA design was incorporated into existing grower-finisher rooms and tested over three trials. Problems with dunging patterns necessitated the modification of the EDA as the study progressed. A 0.4-m rubber strip curtain doorway evolved into a full pen width curtain doorway. During the last trial, when the pigs properly used the EDA as a dunging location, the experimental room equipped with a full width curtain drawing across the EDA tended to reduce odor emissions and provided a 43% reduction in NH3 emissions. Considering the EDA concept and the modifications incorporated to address the experimental challenges over the trials, a full width curtain EDA is the most promising option for separating the main airspace of a barn from the dunging area. More research is required to further develop this concept.

Ozone Treatment of Animal Manure for Odor Control

Problem statement: The effectiveness of ozone in reducing odor emission from liquid animal manure was evaluated under batch and continuous treatment operations. Results: The results indicated that the use of ozone for the treatment of animal manure proved to be effective in reducing the odor offensiveness. A minimum 3.4 level out of 10 (66% reduction) was achieved in the continuous operation; while a minimum of 3.1 (69% reduction) was achieved in the batch operation. Increasing the level of ozone (O3) increased the level of offensiveness which was attributed to the presence of intermediate products due to the interaction between ozone and hydrogen sulfide and methylamine. Conclusion: The cost analysis indicated that the treatment is economical as a ton of manure could be treated at a cost of $ 0.23.

Development and testing of an evaluation procedure for commercial manure additive products

Manure additive products can be used to reduce odour emissions (OE) from livestock farms. The standardised evaluation of these manure additive products under specific farm conditions is important. In this study, the efficacy of a manure additive (WonderTreat(TM), CKLS, Inc., Hong-Kong) was assessed under Australian conditions utilising a combination of laboratory and field-scale evaluation techniques. As a first step, the efficacy of the manure additive was assessed in a laboratory-scale trial using a series of uniformly managed digesters and standard odour, liquor ammonia and hydrogen sulphide concentration measurement procedures. This showed that the addition of WonderTreat(TM) at the 'low dose rate' (LDR) (102.6 g m-2) used during the trial significantly, but only marginally (30%; P = 0.02) reduced the OE rate (mean 13.9 OU m-2 s-1) of anaerobic pig liquor relative to an untreated control (UC) (19.9 OU m-2 s-1). However, the 'high dose rate' (HDR) (205.3 g m-2) also assessed during the trial preformed similarly (19.7 OU m-2 s-1) to the UC. No statistically significant difference in the concentrations of a range of measured water quality variables at the 5% level was observed between the treatments or controls digesters. As a second step, a field-scale assessment of the manure additive was undertaken at a commercial piggery. Two piggery manure lagoons (each with approximately 2500 m2 surface area) were included in the study; one was treated with WonderTreat(TM) while the other was used as control. The efficacy of the treatment was assessed using olfactometric evaluation of odour samples collected from the surface of the pond using a dynamic wind tunnel and ancillary equipment. No statistically significant reduction in OE rate could be demonstrated (P = 0.35), partially due to the limited number of samples taken during the assessment. However, there was a numerical reduction in the average OE rate of the treatment pond (29 OU m-2 s-1 at 1 m s-1) compared to the control lagoon (38 OU m-2 s-1 at 1 m s-1).

Odour and ammonia emission from pig manure as affected by dietary crude protein level

The objective of this study was to determine the effects of dietary crude protein (CP) level on odour emission, odour intensity, odour hedonic tone, ammonia and greenhouse gaseous emission from pig manure, and on fresh faeces and manure characteristics. An experiment was conducted with finishing pigs ( n = 12) in a randomized complete block arrangement with 2 treatments of 12 and 15% dietary CP in six blocks. The 2 diets were supplemented with essential AA up to the level of the animal's requirement. Pigs with an initial body weight (BW) of 57.7 ± 0.7 kg were penned individually in partly slatted floor pens. Faeces and urine of each pig accumulated in separate manure pits under the slatted floor. In the 3rd week of the collection period, fresh faeces were collected for identifying fresh faeces characteristics and for assessing dry matter, organic matter, nitrogen (N), fat and non-starch polysaccharides digestibility using Cr 2O 3 as a marker. In the 6th week of the collection period, air samples were collected directly from each manure pit: one for odour, one for ammonia concentration and one for greenhouse gases. Afterwards the manure was mixed and a representative sample was taken for manure characteristic analysis. Odour samples were analyzed for odour concentration and for hedonic tone and odour intensity. Manure samples were analyzed for volatile fatty acids (VFA), indolic, phenolic, sulphurous compounds, ammonium and total N concentrations and pH. Reducing dietary CP level from 15 to 12% did not affect odour emission, odour intensity and odour hedonic tone and greenhouse gaseous concentration (CH 4, CO 2 and N 2O) ( P > 0.05) of odorous air above the manure pit. Reduced dietary CP level decreased manure pH ( P < 0.001), total N ( P < 0.001) and ammonium ( P < 0.001) concentrations and ammonia emission from pig manure ( P = 0.03). In addition, total VFA, acetic, propionic, iso-butanoic and iso-pentanoic acids, phenol, 4-ethyl phenol and carbon disulfide concentrations in manure were decreased by reducing dietary CP level ( P < 0.05). We conclude that reducing dietary CP from 15 to 12% did not reduce odour emission and greenhouse gaseous concentration; however, ammonia emission was significantly reduced.

Odor reduction rate in the confinement pig building by spraying various additives

The objective of this on-site experiment was to evaluate and compare the effectiveness of currently utilized various additives, i.e. tap water, salt water, digested manure, microbial additive, soybean oil, artificial spice and essential oil, to reduce odor emissions from the confinement pig building. Odor reduction rates were evaluated with respect to sensual odor (odor concentration index, odor intensity and odor offensiveness) and odorous compounds (ammonia and sulfuric odorous compounds). Of the additives investigated in this study, salt water, artificial spice and essential oil had a positive effect on reducing odor generation. The effectiveness of salt water was only observed on ammonia, showing the reduction rates as a function of time ( t = immediately, 1 h, 3 h, 5 h, and 24 h after spraying) were 0.1%, 20%, 36%, 11% and 0.2% as compared to initial level before spraying. The odor intensity and offensiveness were lessened by spraying artificial spice and essential oil of which maximum reduction rates ranged from 60% to 80%. Additionally, the essential oil had a significant effect on reducing sulfuric odorous compounds for 24 h after spraying, which implicates that it functioned as not only a masking agent but also as an antimicrobial agent.

Content of dietary fermentable protein and odour from pig manure

An experiment was conducted in growing pigs to determine the effects of content of potentially fermentable protein (FP) on odour and ammonia emissions from pig manure and on manure characteristics. Pigs ( n = 18) were allocated in a randomised complete block arrangement with 3 treatments in each of 6 blocks. The three treatments had 28.4, 38.2 and 48.0 g fermentable protein per kg of feed. Pigs with an initial body weight (BW) of 41.3 ± 3.2 kg (mean ± S.D.) were housed individually in pens with partly slatted floor and offered a daily feed allowance of 2.8 × maintenance requirement (293 kJ net energy (NE)/BW 0.75). Feed was mixed with water (1/2.5; w/w). After a 2-week adaptation period faeces and urine produced by each pig were collected in individual manure pits under the slatted floor. In the 5th week of the collection period air samples were collected from each manure pit for odour and ammonia analyses. Odour characteristics were measured by olfactometry and ammonia was measured by using two ammonia traps each containing 20 ml 0.5 M HNO 3 solution. Manure samples from each manure pit, taken in the same week as air samples, were analysed for volatile fatty acids (VFAs), indolic, phenolic, sulphurous compounds, ammonium nitrogen and total nitrogen concentrations. Data were evaluated using analysis of variance. Odour and ammonia emissions from pig manure were in the range from 1.88 to 2.78 ou E/(s m 2) and from 0.011 to 0.014 mg/(s m 2), respectively and were not affected by fermentable protein content of the diet (P >0.05). Increased fermentable protein content resulted in higher concentrations of total nitrogen, methyl sulphide, carbon disulphide, ethanethiol, phenol, 3-methyl indole and 4-ethyl phenol in the manure (P <0.01), but did not influence ammonium nitrogen, volatile fatty acids, cresols and indole concentrations in the manure. It is concluded that a decrease in the fermentable protein content of the diet does not reduce odour emission, odour intensity (OI) or odour hedonic tone (HT) in pigs.

A Temperature-Guided Three-Stage Inoculation Method for Municipal Solid Wastes Composting

Inoculation is a human-induced measure that can significantly enhance the composting process by increasing the initial microbial population, formulating viable microbial communities, and generating desired enzymes. However, the inoculation efficiency was usually subjected to competitions of indigenous microorganisms. In this study, a temperature-guided three-stage inoculation (TGTSI) method was developed to control the indigenous cell concentrations, and in turn, enhance the composting efficiency. The experimental results indicated that the TGTSI method could effectively suppress the initial cell concentrations of indigenous microorganisms, which resulted in significantly enhancement of biodegradations as well as the reduction of odor emissions. Moreover, a two-stage kinetics method was employed to analyze the TGTSI mechanisms. The model results were consistent with the experimental data. In conclusion, this study implied that TGTSI could not only enhance the composting process but also save system cost.

Nutrition, key factor to reduce environmental load from pig production

In different parts of Europe animal production is highly concentrated. Pig production generally is the main animal production activity in these areas. Main concerns of these large numbers of pigs are the amount of surplus nutrients in excreta and gaseous losses to the environment. Main nutrients of concern are N, P, and heavy metals and main gaseous losses of concern are ammonia, odour, and methane. Although losses are inevitable to a certain extent, nutrition seems to be a key factor in reducing these losses. Main nutritional strategies to reduce N and P excretions from pigs are: phase feeding (N, P), supplementation of limiting amino acids to the diet (N), and addition of phytase to the diet (P). Nutritional strategies to reduce heavy metals excretions from pigs are: finding alternative, natural, growth promoters that could replace Cu and Zn in the diet; using feedstuffs for the diet that are less contaminated with Cd. Main strategies to reduce ammonia emissions are: 1) lowering crude protein intake in combination with addition of limiting amino acids; 2) Shifting nitrogen excretion from urine to faeces by including fermentable carbohydrates in the diet; 3) lowering pH of urine by adding acidifying salts to the diet; 4) lowering the pH of faeces by inclusion of fermentable carbohydrates in the diet. These strategies proved to be independent from each other and effects are additive. By combining these strategies a total reduction of ammonia emission in growing-finishing pigs of 70% could be reached. Strategies to reduce odour emission are: 1) reducing protein fermentation by balancing available protein and fermentable carbohydrates in the large intestine; 2) Minimizing breakdown of absorbed sulphur amino acids. More studies are needed in this area of research, but results until now are very promising. A clear relationship exists between fermentable carbohydrates in the diet and methane emissions. This disadvantage should be considered when tackling ammonia emission by this strategy. It is concluded that there is a large potential to reduce environmental load within pig dense areas by nutritional means.

Effects of dietary crude protein level on odour from pig manure

The objective of this study was to determine the effects of dietary crude protein (CP) level on odour emission, odour intensity, hedonic tone, and ammonia emission from pig manure and on manure composition (pH, total nitrogen, ammonium, volatile fatty acids, indolic, phenolic and sulphur-containing compounds). An experiment was conducted with growing pigs (n = 18) in a randomised complete-block design with three treatments in six blocks. Treatment groups were 12%, 15% and 18% CP diets. Barley was exchanged for soya-bean meal. Crystalline amino acids (AA) were included in the 12% CP diet up to the level of pigs' requirement; the same amount of AA was added to the 15% and 18% CP diets. Pigs with an initial body weight (BW) of 36.5 ± 3.4 kg (mean ± s.d.) were individually penned in partly slatted floor pens and offered a daily feed allowance of 2.8 × maintenance requirement for net energy (NE: 293 kJ/kg BW0.75). Feed was mixed with water, 1/2.5 (w/w). Faeces and urine of each pig were accumulated together in a separate manure pit under the slatted floor. After an adaptation period of 2 weeks, the manure pits were cleaned and manure was collected. In the 5th week of the collection period, air samples for odour and ammonia analyses, and manure samples were collected directly from each manure pit. Air samples were analysed for odour concentration and for hedonic value and intensity above odour detection threshold. Manure samples were analysed for volatile fatty acids, and indolic, phenolic and sulphurous compounds, ammonium and total nitrogen concentrations. Reducing dietary CP from 18% to 12% lowered odour emission ( P < 0.05) and ammonia emission ( P = 0.01) from pig manure by 80% and 53%, respectively. Reduced dietary CP decreased total nitrogen, methyl sulphide, carbon disulphide, ethanethiol, phenol, 4-ethyl phenol, indole and 3-methyl indole concentrations in the manure ( P < 0.05). Volatile fatty acids and cresols concentrations in the manure of pigs fed different dietary CP levels were similar. A reduction of dietary CP and at the same time providing essential AA is an option to reduce odour emission as well as ammonia emission from pig manure.

Investigating the Capacity of an Activated Sludge Process to Reduce Volatile Organic Compounds and Odor Emissions

The effects of hydrogen sulfide (H2S) diffusion into activated sludge (AS) on odor and volatile organic compound (VOC) concentrations in offgas were studied over an 8-week period. Most VOCs detected in the offgas of both aeration tanks were aromatic hydrocarbons. The VOC concentrations generally decreased when H2S was introduced to the AS compared with the control, indicating a negative effect of H2S on VOC removal. Two volatile organic sulfur compounds present in the test AS offgas showed an increase followed by a decrease during H2S peak loads. Six VOCs and odor concentration increased during the introduction of an H2S peak; however no correlation was observed between H2S and odor concentration. The increase in odor concentration resulted from the increase in the concentration of six aromatic VOCs, which had their removal slowed down during a 100-ppmv H2S peak. Activated sludge diffusion provides effective H2S removal with minimal affect on odor emissions.

생물학적 첨가제 살포에 의한 밀폐형 돈사에서의 악취 저감 평가

본 연구는 지금까지 돈사 악취 제어를 목적으로 이용되었던 여러 종류의 첨가제를 살포 방법을 통해 실제 돈사 현장에 적용하여 악취 저감 효율 및 지속성을 비교 평가하기 위해 수행되었다. 소금물, 인공 식향료, 식물성 천연향료를 제외한 나머지 4개의 첨가제는 살포 전과 후의 악취 저감 현상이 뚜렷이 관찰되지 않았다. 소금물의 경우 특히 암모니아 농도의 시간에 따른 저감율이 현저했는데, 이는 소금물의 염소 이온이 피트 분뇨내 암모늄 이온과 결합, 수용액 상태로 존재하게 하여 대기 중으로 암모니아 발생을 억제했기 때문이라 판단된다. 인공 식향료의 경우 악취 원인 물질 농도의 저감 현상은 보이지 않았으나, 관능법으로 평가된 악취 강도와 불쾌도 측면에서는 상당한 제어 효과가 관찰되었다. 이러한 현상은 인공 식향료가 돈사내 피트 슬러리에서 발생되는 악취 원인 물질을 분해한다기 보다는 돈사내 악취 은폐제로써 작용하여 지속성은 짧지만 효율적인 악취 저감 작용을 한 것으로 사료된다. 식물성 천연향료의 경우 악취 강도와 불쾌도, 황 계열 악취 물질의 저감 효과가 다른 첨가제에 비해 상대적으로 월등하게 나타났다. 인공 식향료와는 달리 식물성 천연 향료는 은폐 효과와 더불어, 분뇨내 황 계열 악취 원인 물질을 생성하는 혐기성 미생물 군집의 생장을 제어하는 antimicrobial agent로서의 역할도 하는 것으로 사료된다. 그러나 악취 센서기를 통해 측정된 악취 농도는 위와는 상반된 결과가 나타났는데, 이는 악취 센서기가 인공 식향료와 식물성 천연향료가 자체적으로 지닌 향 성분도 악취의 한 범주로 인식되어 유도된 결과라 판단된다. 본 연구를 통해 나타난 결과는 현장에서 수행된 분석 결과로 실험 당일 날의 외부 기후 상황 및 돈사내 환경 여건에 따른 돼지들의 반응 행동 양상에 따라 실험 결과에 상당한 영향을 준다는 사실을 염두하여 고찰할 필요가 있다. 【Maintenance of an optimal air quality in the enclosed pig building is potentially important in terms of pig performance and farmer health. The objective of this on-site experiment is to evaluate and compare efficiencies of currently utilized biological additives to reduce odor emissions from the enclosed pig building. As a result, generally all the additives except for salt water, artificial spice and essential oil were proved ineffective in reducing odor generation. The beneficial effects of salt water, artificial spice and essential oil on odor reduction were highlighted on ammonia, odor intensity and offensiveness, and sulfuric odorous compounds, respectively. To efficiently utilize odor masking agent such as the artificial spice, ventilation rate should keep slightly lower than the optimal level. Essential oil functioned well as not only masking agent but also antimicrobial agent for reducing odor. To precisely quantify odor concentration, it should be measured by not the odor sensor but the olfactometry technique.】

Assessment of permeable covers for odour reduction in piggery effluent ponds. 2. Field-scale trials

The efficacy of supported covers was investigated under field conditions using a series of prototypes deployed on an anaerobic pond treating typical piggery waste. Research focused on identifying effective cover support materials and deployment methods, quantifying odour reduction, and estimating the life expectancy of various permeable cover materials. Over a 10-month period, median odour emission rates were five to eight times lower from supported straw cover surfaces and a non-woven, spun fibre polypropylene weed control material than from the adjacent uncovered pond surface. While the straw covers visually appeared to degrade very rapidly, they continued to reduce odour emissions effectively. The polypropylene cover appeared to offer advantages from the perspectives of cost, reduced maintenance and ease of manufacture.

EFFECTS OF ROOM OZONATION ON AIR QUALITY AND PIG PERFORMANCE

Reducing odor emissions from swine farms to avoid complaints about odor nuisance is a major issue. Ozonationhas been used to reduce odor in swine buildings, but little research exists on its benefits. A swine-finishing building wasdivided into two identical rooms and two treatments, ozonation and the control, were applied in a cross-over design. Thetreatments were switched between rooms every three weeks. The overall experimental period was 12 weeks, during whichthere were four trials. Pig growth performance, dust mass and size concentration, odor intensity, total sulfur compounds,hydrogen sulfide concentration, ammonia concentration, and total heterotrophic bacterial counts were measured andanalyzed during the test period. Sulfur-containing compounds detected included dimethyldisulfide, dimethylsulfide(methanethiol), and dimethyltrisulfide. Ozone application to a swine building at the maximum safe concentration of 0.1 ppmdid not have any statistically significant effects on dust mass concentration, odor concentration and emission rate, sulfurcompound concentrations, and bacteria counts. However, it did increase ammonia concentration and decrease pig averagedaily gain. The ozonation effects on hydrogen sulfide concentration could not be evaluated by the gas tube method used duringthis study.

EFFECTS OF ENVIRONMENTAL FACTORS ON ODOR EMISSION FROM PIG MANURE

Altering environmental factors may change odor emission from pig manure. The main objective of thislaboratory-scale study was to examine the effects of temperature, ventilation rate, emitting area, and manure dilution ratioon odor emission from growing pig manure, while also testing their effects on manure characteristics. Manure was placedin vessels with different surfaces (303, 475, and 595 cm2), and water was added to create different dilution ratios (0%, 50%,and 100%). The vessels were connected to glass capillaries with different ventilation rates through the headspace (0.5, 1.0,and 1.5 L min-1) and were placed in climate-controlled rooms with different temperatures (10C, 20C, and 30C). We useda face-centered central composite design with 54 experimental units in two rounds of three blocks. Odor samples were takenat the end of experiment (after seven days). Manure samples were collected at the start and at the end of the experiment. Themean odor emission from the manure vessel was 2326 ouE h-1 m-2. Increased temperature, ventilation rate, and dilution ratioincreased odor emission. Emitting area did not influence odor emission, but positively influenced total-N loss. Total-N lossincreased as temperature and ventilation rate increased, but decreased as dilution ratio increased. Lowering temperature andventilation rate can be considered as starting points to reduce odor emission from pig manure in practical conditions. Theeffects of dilution ratio and emitting area on odor emission could not be fully separated from the effect of headspace volumein this study and should be further studied.

Relationship between Organic Matter Decomposition and Odorous Compounds' Emission during Thermophilic Composting

We investigated the effect of inoculant on the emission of odorous compounds during isothermal thermophilic composting processes at 60°C. Of these compounds, ammonia and odorous sulfur compounds, hydrogen sulfide (H 2 S), methylmercaptane (MMC), dimethylsulfide (DMS), and dimethyldisulfide (DMDS) were measured. We used three different inoculants, and found that composting with two of them, where vigorous organic matter decomposition occurred, generated a very high concentration of NH 3 , as high as 4000 ppm, and also generated high concentrations of sulfur compounds, especially of MMC and DMDS. In contrast, very few odorous compounds were emitted during composting with the third inoculant; however, there was an extremely small degree of organic matter decomposition in this composting. These results indicate that it is not sufficient to merely compare odor emission when assessing the best operational conditions for composting with a small amount of odor emission. In other words, in assessing composting operations with regards to the effective reduction of odor emissions, it is important to simultaneously quantify the degree of organic matter decomposition that occurs.