Ruminal Fermentation of Propylene Glycol and Glycerol

Bovine rumen fluid was fermented anaerobically with 25 mM R-propylene glycol, S-propylene glycol, or glycerol added. After 24 h, all of the propylene glycol enantiomers and approximately 80% of the glycerol were metabolized. Acetate, propionate, butyrate, valerate, and caproate concentrations, in decreasing order, all increased with incubation time. Addition of any of the three substrates somewhat decreased acetate formation, while addition of either propylene glycol increased propionate formation but decreased that of butyrate. R- and S-propylene glycol did not differ significantly in either their rates of disappearance or the products formed when they were added to the fermentation medium. Fermentations of rumen fluid containing propylene glycol emitted the sulfur-containing gases 1-propanethiol, 1-(methylthio)propane, methylthiirane, 2,4-dimethylthiophene, 1-(methylthio)-1-propanethiol, dipropyl disulfide, 1-(propylthio)-1-propanethiol, dipropyl trisulfide, 3,5-diethyl-1,2,4-trithiolane, 2-ethyl-1,3-dithiane, and 2,4,6-triethyl-1,3,5-trithiane. Metabolic pathways that yield each of these gases are proposed. The sulfur-containing gases produced during propylene glycol fermentation in the rumen may contribute to the toxic effects seen in cattle when high doses are administered for therapeutic purposes

Field sampling method for quantifying volatile sulfur compounds from animal feeding operations

Volatile sulfur compounds (VSCs) are a major class of chemicals associated with odor from animal feeding operations (AFOs). Identifying and quantifying VSCs in air is challenging due to their volatility, reactivity, and low concentrations. In the present study, a canister-based method collected whole air in fused silica-lined (FSL) mini-canister (1.4 L) following passage through a calcium chloride drying tube. Sampled air from the canisters was removed (10–600 mL), dried, pre-concentrated, and cryofocused into a GC system with parallel detectors (mass spectrometer (MS) and pulsed flame photometric detector (PFPD)). The column effluent was split 20:1 between the MS and PFPD. The PFPD equimolar sulfur response enhanced quantitation and the location of sulfur peaks for mass spectral identity and quantitation. Limit of quantitation for the PFPD and MSD was set at the least sensitive VSC (hydrogen sulfide) and determined to be 177 and 28 pg S, respectively, or 0.300 and 0.048 μg m−3 air, respectively. Storage stability of hydrogen sulfide and methanethiol was problematic in warm humid air (25 °C, 96% relative humidity (RH)) without being dried first, however, stability in canisters dried was still only 65% after 24 h of storage. Storage stability of hydrogen sulfide sampled in the field at a swine facility was over 2 days. The greater stability of field samples compared to laboratory samples was due to the lower temperature and RH of field samples compared to laboratory generated samples. Hydrogen sulfide was the dominant odorous VSCs detected at all swine facilities with methanethiol and dimethyl sulfide detected notably above their odor threshold values. The main odorous VSC detected in aged poultry litter was dimethyl trisulfide. Other VSCs above odor threshold values for poultry facilities were methanethiol and dimethyl sulfide

Effects of Swine Dietary Treatment on Odor and VOCs Emitted from Swine Manure

Odor and VOCs emissions associated with swine production facilities is a major concern for the swine industry. Swine manure is one of the major sources of odor from swine operations. Odor control approaches include ration manipulation, improved manure treatment processes, capture and treatment of odorous gases, and improved dispersion. This study was conducted to investigate the effects of low level of crude protein and low sulfur content in small swine diet on odor and VOCs emissions from the headspace of swine manure. Small pigs in metabolic stalls were fed twice daily over 28 days with diets containing either 19.36 % crude protein, 7.06 % cellulose and 2,296 mg/kg sulfur (diet B) or 17.83 % crude protein, 6.82 % cellulose and 1,772 mg/kg sulfur (diet H). Three replicate trials were conducted and three pigs were used for each diet. All excreted manure (feces and urine) were collected daily after morning feeding and added to the manure storage vessel designed to hold waste from the same growing pig. Gas samples were collected from the headspace of manure storage container using 85 µm Carboxen/PDMS SPME fibers at the end of each trial and three replicate gas samples were collected for each pig. All samples were analyzed simultaneously for chemicals and odors on a GC-MS-olfactometry system. Statistical analyses were performed to determine the effects on diets on target odorous chemicals and odor. A total of 40 compounds belonging to 14 chemical classes were identified the headspace of swine manure. A subset of 14 odorous compounds responsible for the characteristic odor of swine manure odor were selected for statistical analyses. Lower sulfur and lower crude protein diet was associated with reduced methanethiol (p=0.0686), dimethyl sulfide (p=0.0006), 2,4-dithiapentane (p2S) (p=0.0014), \u27acetic\u27 (acetic acid) (p=0.00001), \u27skunky\u27 (2,4-dithiapentane) (p=0.0261), \u27onion\u27 (dimethyl trisulfide) (p=0.0122) and phenolic\u27 (4-ethyl phenol) (p=0.0168)

The Impact of Carbohydrate and Protein Level and Sources on Swine Manure Foaming Properties

This study explored the impact of swine diet on the composition, methane production potential, and foaming properties of manure. Samples of swine manure were collected from controlled feeding trials with diets varying in protein and carbohydrate levels and sources. Protein sources consisted of corn with amino acids, corn-soybean meal with amino acids, corn-soybean meal, corn-canola meal, corn-corn gluten meal, and corn-poultry meal. Carbohydrate sources consisted of corn-soybean meal, barley, beet pulp, distillers dried grains with solubles (DDGS), soy hulls, and wheat bran. Manure samples were tested for a number of physical and biochemical parameters, including total solids, volatile solids, viscosity, density, methane production rate, biochemical methane potential, foaming capacity, and foam stability. Statistical analyses were performed to evaluate whether different carbohydrate and/or protein ingredients affected these physico-chemical properties or the samples’ ability to produce methane gas. After conducting these trials, another feeding trial was performed to evaluate if the addition of Narasin into rations (corn-soybean and DDGS) could reduce the methane production rate or potential of the manure. These samples were also tested for the physical and biochemical parameters mentioned previously. Finally, an additional manure foaming study was conducted involving the addition of specific carbohydrates ground to different particle sizes and corn oil to observe the effects that the additives had on foaming capacity and stability

Three-Phase Foam Analysis and the Development of a Lab-Scale Foaming Capacity and Stability Test for Swine Manures

Foam accumulation on the manure slurry at deep pit swine facilities has been linked to flash fire incidents, making it a serious safety concern for pork producers. In order to investigate this phenomenon, samples of swine manure were collected from over 50 swine production facilities in Iowa with varying levels of foam accumulation over a seven month period. These samples were tested for a number of physical and chemical parameters including temperature, pH, total solids, volatile solids, volatile fatty acid concentration, biochemical methane potential, and methane production rate. After establishing these parameters, a foaming capacity and stability test was performed where samples were placed in clear PVC tubes with air diffusers at the bottom to simulate biogas production. The amount of foam produced at a set aeration rate was recorded as a measure of foaming capacity, and foam stability was assessed by measuring the height of foam remaining at certain time intervals after aeration had ceased. The results of this test indicated that samples collected from foaming barns showed a greater capacity to produce and stabilize foam. In addition, statistical analysis indicated that manures with foam produced methane at significantly greater rates than non-foaming manures (0.154 ± 0.010 and 0.052 ± 0.003 L CH4./L slurry*day respectively, average standard error), and consequently had significantly greater fluxes of methane moving through the manure volume. On the other hand, the biochemical methane production assay suggested that manure from foaming pits had less potential to generate methane (112 ± 9 mL CH4/g VS) than non-foaming pits (129 ± 9 mL CH4/g VS), and the VFA analysis showed significantly lower concentrations in foaming pits (4472, 3486, and 1439 μg/g for the surface level and descending depths of the pit, respectively) as compared to non-foaming pits (9385,8931, and 6938 μg/g for the same sample depths). When taken together, these assays suggest enhanced anaerobic digestion efficiency from foaming barns, as well as the possible accumulation of a surfactant at the manure-air interface of foaming deep pits. Overall, this work supports a three-phase system conceptualization of foam production in swine manure deep pits, and that the control of one or more of these phases will be required for mitigation

Hydrogen Sulfide and Nonmethane Hydrocarbon Emissions from Broiler Houses in the Southeastern United States

Hydrogen sulfide (H2S) and nonmethane hydrocarbon (NMHC) emissions from two mechanically ventilated commercial broiler houses located in the southeastern United States were continuously monitored over 12 flocks for a one-year period during 2006-2007 as a joint effort between Iowa State University and the University of Kentucky. H2S and NMHC concentrations were measured using UV-Fluorescence H2S analyzers and methane/nonmethane/total hydrocarbon dual flame ionization detector gas chromatographs. Ventilation rates in each house were measured continuously by monitoring building static pressure and operational status of all ventilation fans in conjunction with individual performance curves developed and verified in situ using a Fan Assessment Numeration System (FANS) unit. United States EPA methods TO-15 and TO-17 were used for the nonmethane hydrocarbon compound speciation. The top-25 compounds are presented. The overall mean H2S and NMHC emission rates for a one-year period were 65.7 ± 42 g/d-house and 0.76 ± 0.43 kg C3H8/d-house, respectively. Annual H2S emission for the two broiler houses (including downtime emissions) averaged 19.2 kg per year per house or 0.147 g per bird marketed when the birds were marketed at 52 days of age with a stocking density of 11.8 bird per m2 (1.1 bird per ft2). Annual NMHC emission averaged 231 kg per year per house (510 lb per year per house) or 1.77 g per bird marketed

Vegetative Buffers for Swine Odor Mitigation: Wind Tunnel Evaluation of Air Flow Dynamics

One of the most significant and persistent environmental concerns regarding swine production is odor transport from animal feeding operations and manure storage facilities. Odor constituents include ammonia, hydrogen sulfide, and various volatile organic compounds (VOCs), which may exist as individual gaseous compounds or adsorbed onto particulates (Zahn et al., 1997; Trabue et al., 2006; Tyndall and Coletti, 2006). Building type, facility management, animal diet, and climate affect the amount of potential odor constituents generated at production facilities. Local environmental conditions, especially wind speed and direction, vegetative cover, and topography determine the amount of odor constituents transported downstream from production facilities. Odor mitigation strategies may be designed to reduce either odor generation or transport or both

Field Sampling Method for Quantifying Odorants in Humid Environments

Most air quality studies in agricultural environments use thermal desorption analysis for quantifying semivolatile organic compounds (SVOCs) associated with odor. The objective of this study was to develop a robust sampling technique for measuring SVOCs in humid environments. Test atmospheres were generated at ambient temperatures (23 ± 1.5 °C) and 25, 50, and 80% relative humidity (RH). Sorbent material used included Tenax, graphitized carbon, and carbon molecular sieve (CMS). Sorbent tubes were challenged with 2, 4, 8, 12, and 24 L of air at various RHs. Sorbent tubes with CMS material performed poorly at both 50 and 80% RH due to excessive sorption of water. Heating of CMS tubes during sampling or dry-purging of CMS tubes post sampling effectively reduced water sorption with heating of tubes being preferred due to the higher recovery and reproducibility. Tenax tubes had breakthrough of the more volatile compounds and tended to form artifacts with increasing volumes of air sampled. Graphitized carbon sorbent tubes containing Carbopack X and Carbopack C performed best with quantitative recovery of all compounds at all RHs and sampling volumes tested. The graphitized carbon tubes were taken to the field for further testing. Field samples taken from inside swine feeding operations showed that butanoic acid, 4-methylphenol, 4-ethylphenol, indole, and 3-methylindole were the compounds detected most often above their odor threshold values. Field samples taken from a poultry facility demonstrated that butanoic acid, 3-methylbutanoic acid, and 4-methylphenol were the compounds above their odor threshold values detected most often

Speciation of volatile organic compounds from poultry production

Volatile organic compounds (VOCs) emitted from poultry production are leading source of air quality problems. However, little is known about the speciation and levels of VOCs from poultry production. The objective of this study was the speciation of VOCs from a poultry facility using evacuated canisters and sorbent tubes. Samples were taken during active poultry production cycle and between production cycles. Levels of VOCs were highest in areas with birds and the compounds in those areas had a higher percentage of polar compounds (89%) compared to aliphatic hydrocarbons (2.2%). In areas without birds, levels of VOCs were 1/3 those with birds present and compounds had a higher total percentage of aliphatic hydrocarbons (25%). Of the VOCs quantified in this study, no single sampling method was capable of quantifying more than 55% of compounds and in several sections of the building each sampling method quantified less than 50% of the quantifiable VOCs. Key classes of chemicals quantified using evacuated canisters included both alcohols and ketones, while sorbent tube samples included volatile fatty acids and ketones. The top five compounds made up close to 70% of VOCs and included: 1) acetic acid (830.1 μg m−3); 2) 2,3-butanedione (680.6 μg m−3); 3) methanol (195.8 μg m−3); 4) acetone (104.6 μg m−3); and 5) ethanol (101.9 μg m−3). Location variations for top five compounds averaged 49.5% in each section of the building and averaged 87% for the entire building

Wind Tunnel Evaluation of Vegetative Buffer Effects on Air Flow Near Swine Production Facilities

Increasing concerns about odor transport from swine production facilities have substantiated both field and laboratory studies on air flow dynamics near these buildings (Mavroidis et al., 2003; Aubrun and Leitl, 2004b). Odor constituents include ammonia, hydrogen sulfide, and various volatile organic compounds (VOCs), which may exist as individual gaseous compounds or adsorbed onto particulates (Zahn et al., 1997; Trabue et al., 2006; Tyndall and Coletti, 2006). Building type, animal diet, facility management, and climate may potentially affect the amount of odor constituents generated at swine facilities. Vegetative cover, local weather conditions, and topography may determine the amount of odor constituents transported from swine facilities. There is an urgent need for designing mitigation strategies to reduce either swine odor generation or transport or both