Dwaine S. Bundy

Emissions of Ammonia, Hydrogen Sulfide, and Odor before, during, and after Slurry Removal from a Deep-Pit Swine Finisher

Abstract It is a common practice in the midwestern United States to raise swine in buildings with under-floor slurry storage systems designed to store manure for up to one year. These so-called “deep-pit” systems are a concentrated source for the emissions of ammonia (NH3), hydrogen sulfide (H2S), and odors. As part of a larger six-state research effort (U.S. Department of Agriculture-Initiative for Future Agriculture and Food Systems Project, “Aerial Pollutant Emissions from Confined Animal Buildings”), real-time NH3 and H2S with incremental odor emission data were collected for two annual slurry removal events. For this study, two 1000-head deep-pit swine finishing facilities in central Iowa were monitored with one-year storage of slurry maintained in a 2.4 m-deep concrete pit (or holding tank) below the animal-occupied zone. Results show that the H2S emission, measured during four independent slurry removal events over two years, increased by an average of 61.9 times relative to the before-removal H2S emission levels. This increase persisted during the agitation process of the slurry that on average occurred over an 8-hr time period. At the conclusion of slurry agitation, the H2S emission decreased by an average of 10.4 times the before-removal emission level. NH3 emission during agitation increased by an average of 4.6 times the before-removal emission level and increased by an average of 1.5 times the before-removal emission level after slurry removal was completed. Odor emission increased by a factor of 3.4 times the before-removal odor emission level and decreased after the slurry-removal event by a factor of 5.6 times the before-removal emission level. The results indicate that maintaining an adequate barn ventilation rate regardless of animal comfort demand is essential to keeping gas levels inside the barn below hazardous levels.

COMPARISON OF OLFACTOMETRY, GAS CHROMATOGRAPHY, AND ELECTRONIC NOSE TECHNOLOGY FOR MEASUREMENT OF INDOOR AIR FROM SWINE FACILITIES

Indoor air from swine finishing facilities was analyzed by olfactometry, gas chromatography, and an electronic nose. Odorous air samples were collected from two feeding rooms at an Iowa State University facility. Six finishing pigs were housed in each room. Ten–liter room air samples, collected in Tedlar bags, were analyzed using the AC’SCENT International Olfactometer (St. Croix Sensory, Stillwater, Minn.). Dynamic dilution triangular forced–choice olfactometry was the method employed. One–liter air samples, also collected in Tedlar bags, were analyzed using an AromaScan A32S electronic nose (Osmetech, Crewe, U.K.) containing an array of 32 conducting–polymer sensors. Solid phase microextraction fibers (Supelco, Bellefonte, Pa.) were used to adsorb compounds in the air to be analyzed by gas chromatography/mass spectrometry (GC/MS). Sixteen compounds, primarily non–sulfur protein metabolites, were developed into a quantification standard for GC/MS based on the frequency of occurrence of these compounds in the collected samples. Using these compounds, an equation was generated to predict odor dilution threshold. Poor prediction capability (R2 < 0.3) indicates that additional analytes require consideration. Electronic nose evaluation of room air samples was not strongly correlated to olfactometry measures (r < 0.2). However, the equation developed from the GC/MS analyses was capable of predicting the electronic nose response to air samples (R2 > 0.8). The results suggest that human panelist responses may be based on detection of compounds that were not included in GC/MS quantification procedures and are not well detected by this electronic nose. Variation in response within and among human panelists likely accounts for some of the discrepancy between human assessment and chemical and instrumental methods of odor evaluation.

Manure Incorporation Equipment Effects on Odor, Residue Cover, and Crop Yield

Land application of manure may produce unacceptable odors. Field experiments in undisturbed (no-till) soybean and corn residue were conducted to evaluate six liquid swine manure application/incorporation methods. The methods were injection with a commercial (1) chisel or (2) sweep, (3) incorporation with tandem disk harrow after broadcast application, (4) broadcast application with no incorporation, (5) injection with a narrow-profile knife, and (6) surface application behind row cleaners. The row cleaner and all injection treatments used spoke-covering wheels. Air samples over the soil surface were obtained immediately following and one day after manure application, and odor level was measured by olfactometry (i.e., the amount of air dilutions to reach odor threshold). Residue cover and yield were also measured. Incorporation techniques typically reduced odor level by a factor of three to ten as compared with a broadcast application. One day after application, odor was greatly reduced and often indistinguishable from that of untreated soil (no manure application). Residue cover differences among application methods were more pronounced in soybean residue. Application by the narrow-profile knife, row cleaner, and chisel maintained soybean residue cover better than other incorporation methods yet limited odor similar to these methods. Although cover was reduced over winter, greater soybean residue cover remained after planting with fall than with spring manure applications. Differences in odor level and residue cover among methods were less in corn than soybean residue. All incorporation techniques reduced odor levels, and chisel incorporation maintained corn residue cover after planting similar to broadcast application. For both crops, broadcast application maintained the greatest residue cover but had the highest odor level. Incorporation of manure generally reduced odor, reduced residue cover, increased corn yield, and did not affect soybean yield.

Using Olfactometry to Measure Intensity and Threshold Dilution Ratio for Evaluating Swine Odor

Intensity and threshold dilution ratio are two important indices for odor control of swine buildings. Although odor threshold dilution ratio is a widely used index to describe an odor, it should be related to intensity to be more useful. A method was proposed to measure both indices simultaneously by using a dynamic forced-choice olfactometer. Four air samples were taken from each of four swine rooms including farrowing, finisher, gestation, and nursery. A panel of eight people was used to evaluate odor intensity. Odor threshold dilution ratios were calculated according to the American Society for Testing and Materials (ASTM) Standard Practice E679-91 to be 333, 424, 25, and 221 for samples collected from farrowing, finisher, gestation, and nursery rooms, respectively. After the samples were diluted 14.7 times, the odor intensities were evaluated to be 3.79, 3.46, 0.48, and 4.0 for the above-mentioned rooms, respectively. The data collected were used to develop a mathematical model.

Real-Time Airflow Rate Measurements from Mechanically Ventilated Animal Buildings

Abstract This paper describes techniques used to determine airflow rate in multiple emission point applications typical of animal housing. An accurate measurement of building airflow rate is critical to accurate emission rate estimates. Animal housing facilities rely almost exclusively on ventilation to control inside climate at desired conditions. This strategy results in building airflow rates that range from about three fresh-air changes per hour in cold weather to more than 100 fresh-air changes per hour in hot weather. Airflow rate measurement techniques used in a comprehensive six-state study could be classified in three general categories: fan indication methods, fan rotational methods, and airspeed measurement methods. Each technique is discussed and implementation plans are noted. A detailed error analysis is included that estimated the uncertainty in airflow rate between ±5 and ±6.1% of reading at a building operating static pressure, air temperature, relative humidity, and barometric pressure of 20 Pa, 25 °C, 50%, and 97,700 Pa, respectively.

Reduction of odor and volatile substances in pig slurries by using pit additives

Abstract The effects of five commercial pit additive products on the release of odor nuisance and volatile compounds from swine manure were examined in this study. The changes of pH, volatile fatty acids, total solids, total volatile solids, total nitrogen, and total ammonia nitrogen in swine manure were measured and the levels of aerial ammonia and hydrogen sulfide were monitored. The odor threshold was determined by a dynamic triangle forced‐choice olfactometer. The results showed that all the five products reduced the levels of odor threshold by different degrees ranging from 58% to 87% as compared with the control samples. Three of the five products showed reductions in volatile fatty acids and total volatile solids. Comparing the reduction in odor threshold levels with the changes in the amount of volatile fatty acids indicated that the malodor intensities are not proportionally related to the overall amount of volatile fatty acids existing in the swine manure. The malodor could be produced by certai...

Modeling Receptor Odor Exposure from Swine Production Sources Using CAM

A model, called the Community Assessment Model for Odor Dispersion (CAM), was developed to predict receptor odor exposure from multiple swine production sources. The intended use of CAM was to provide a tool for evaluating the odor exposure to receptors in a community when siting new swine production systems and how a change in odor control technologies alters the odor exposure to receptors. CAM can handle up to 20 swine production sources with up to 100 receptors in a community of any size. The model incorporates historical average local weather data, coordinate locations of all sources and receptors, ground and above-ground area sources, seasonal variations in odor emission, source production footprint and orientation, and documented proven odor mitigation technologies. CAM does not predict the influence of calm conditions(wind speeds = 1.03m/s), topography, or obstruction downwash. CAM predicts the number of hours of exposure to weak (2:1) and greater or identifiable (7:1) and greater odors and these are used to assess a siting decision. CAM was compared against field collected odor concentration data and was found, using a technique of quantile-quantile plots, to over-predict observed odor concentrations by 1.49 for downwind distances between 152 and 1524 m in one comparison study. In a second comparative study, CAM over-predicted observed odor concentrations by 1.91, 1.31, and 1.35 for downwind distances of greater than 150, 275, and 300m, respectively.

The hindrance in the development of pit additive products for swine manure odor control ‐ A review

Abstract This paper reviews the literature on the development of pit additive products for swine manure odor control. It addresses the problems currently existing in the areas of both product designing and testing. Odors emitted from the swine manure storage system are complicated by the characteristics of many volatile organic compounds. A clear understanding of the major odorous compounds that serve as odor indicators is of great importance in developing quality odor control products. Past research has identified volatile fatty acids as indicators of malodor; however, the most recent studies showed that they still may be misleading. There exists a need of in‐depth classification of the odorous compounds with respect to the inherent characteristics of these compounds. Lack of this information has already contributed to the blind development of pit additive products. Another hindrance is the lack of a standard procedure to scientifically evaluate pit additive products. Thus, more effort is needed in devel...

Biofilter‐a malodor control technology for livestock industry

Abstract Biofilters give a new route to solve malodor problems from livestock and poultry production. Unlike wet‐scrubbers and trickling filters, the odor compounds and pollutants eliminated by biofilters aie completely metabolized and degraded without causing secondary pollution. This paper reviews these recently developed techniques and applications and intends to introduce this technology to livestock industry for malodor and contaminant control. pH adjustment and inoculation and nutrient seeding techniques improve the feasibility of biofiltration application in malodor control. Isolating deodorizing bacteria greatly increases the biodegradation rate and the possibility of equalizing the adsorption rate and metabolic rate, which will highly ameliorate the biofiltration efficiency.

Bacteria additives to the changes in gaseous mass transfer from stored swine manure

Abstract A bacteria additives treatment experiment in assessing the changes in gaseous mass transfer from stored swine manure is presented. The experiment is tested for ammonia, methane, hydrogen sulfide, and carbon dioxide emission data sampled from pilot swine manure columns and analyzed by GC/MS. The result shows that bacteria additives slightly reduce the methane and carbon dioxide releases, while the same additives do not show any effect on the reduction of ammonia. The hydrogen sulfide contents of stored swine manure continued to be low. Gas concentrations emitted from treated and untreated stored swine manure were: 3.76 and 2.2 ppm for methane, 0.35 and 0.11 ppm for ammonia, and 1000 and 470 ppm for carbon dioxide, respectively. A simple model to estimate gas emission rates is also developed from the viewpoint of two‐film resistance theory. The average emission rates calculated from the model for methane, ammonia, and carbon dioxide are respectively: 0.01, 0.0005, and 13.98 g/min from untreated sto...