Comprehensive field studies were initiated in 2002 to measure emissions of ammonia (NH 3 ), hydrogen sulfide (H 2 S), carbon dioxide (CO 2 ), methane (CH 4 ), nonmethane hydrocarbons (NMHC), particulate matter Ͻ10 m in diameter, and total suspended particulate from swine and poultry production buildings in the United States. This paper focuses on the quasicontinuous gas concentration measurement at multiple locations among paired barns in seven states. Documented principles, used in air pollution monitoring at industrial sources, were applied in developing quality assurance (QA) project plans for these studies. Air was sampled from multiple locations with each gas analyzed with one high quality commercial gas analyzer that was located in an environmentally controlled on-farm instrument shelter. A nominal 4 L/min gas sampling system was designed and constructed with Teflon wetted surfaces, bypass pumping, and sample line flow and pressure sensors. Three-way solenoids were used to automatically switch between multiple gas sampling lines with Ն10 min sampling intervals. Inside and outside gas sampling probes were between 10 and 115 m away from the analyzers. Analyzers used chemiluminescence, fluorescence, photoacoustic infrared, and photoionization detectors for NH 3 , H 2 S, CO 2 , CH 4 , and NMHC, respectively. Data were collected using personal computerbased data acquisition hardware and software. This paper discusses the methodology of gas concentration measurements and the unique challenges that livestock barns IMPLICATIONSThe emission of air pollutants is currently the biggest manure management issue facing U.S. agriculture. Gas pollutants emitted by concentrated animal feeding operations can create neighborhood nuisance, animal and/or human health concerns, or noncompliance with state and/or federal regulations. Currently, an assessment of the true impact of these pollutants is limited by the lack of reliable emission rate data. Gas emission measurement methods described in this paper were used to determine baseline emission rates for animal confinement buildings, provide data for the development of process-based models, and test abatement methods.
Biofilter media mixtures were compared in 18 pilot-scale biofilters treating pit gases from a swine facility. The compost and wood chips mixtures ranged from 100% wood chips to a 50-50 blend in 10% increments. The effect of three media moisture contents (low, medium, and high) on biofilter performance was also evaluated. Odor and hydrogen sulfide reduction did not change significantly for mixtures with greater than 20% compost. For efficient odor, hydrogen sulfide, and ammonia reduction media moisture must be greater than 40% wb. Media moisture content influenced odor, hydrogen sulfide, and ammonia reduction more than the ratio of compost and wood chips. The count of heterotrophic or sulfur-oxidizing bacteria did not change in a discernable pattern with respect to media mixture or moisture content. As the amount of compost increased in the media mixtures, the pressure drop also increased. Based on this experiment, the recommended mixing ratio of compost to wood chips for biofilters on swine facilities is minimum 30% compost and 70% wood chips by weight.
The objective of the study was to develop a science-based model, OFFSET (Odor from Feedlot-Setback Estimation Tool), to establish setback distances from animal production sites based on the use of an air dispersion model (INPUFF-2) and the actual odor emission data from these sites. Extensive research was conducted to obtain representative odor emissions from various animal facilities and to evaluate the air dispersion model. Odor emissions were measured from 280 animal buildings and manure storage units on 85 farms in Minnesota during 1998 to 2001. The geometric means of the odor emission rates for each type of odor source were obtained to represent odor emissions of that source. The efficiencies of some odor control technologies were summarized. The air dispersion model was evaluated for short-distance (<0.5 km) odor dispersion prediction against the odor plumes measured by trained field assessors on 20 farms and also for long-distance (4.8 km) odor dispersion prediction against odor data recorded by trained resident observers living in the vicinity of livestock operations in a 4.8 × 4.8 km rural area. The relationship between odor detection threshold and intensity was obtained for swine and cattle odors in order to convert odor intensity to detection threshold. The results indicated that the INPUFF-2 model was capable of simulating odor dispersion downwind from animal production operations for low-intensity odors. Six stable or neutral weather conditions that favor odor transport were identified, and their historical occurrence frequencies in all 16 directions at six weather stations in Minnesota were obtained. The occurrence frequencies of these weather conditions were used to determine odor occurrence frequencies in the OFFSET model.
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