Juan C. Ramirez-Dorronsoro

The National Air Emissions Monitoring Study: Overview of Barn Sources

The National Air Emissions Monitoring Study (NAEMS) is required by a U.S. EPA air consent agreement, in which livestock producers agreed to collect air emission data in exchange for more time to report their emissions and apply for any necessary permits. Field measurement of livestock air emissions is a major part of the study. Compared with most previous field studies of barn air quality, the NAEMS was designed to have 1) several pollutants measured simultaneously including particulate matter (PM), ammonia (NH3), hydrogen sulfide (H2S), and non-methane volatile organic compounds (NMVOC), 2) a long duration of two years, 3) a large number of measured barns (38) using the same protocol, 4) careful selection of farms to enhance their representativeness, and 5) a high level of quality assurance and quality control as required by the U.S. EPA, which is supervising the study. The NAEMS is collecting continuous air emission data from 38 barns at five dairies, five pork production sites, three egg layer operations, one layer manure shed, and one broiler facility for a period of 2 years starting in 2007. At each barn monitoring site, an on-farm instrumentation shelter houses equipment for measuring pollutant concentrations at representative barn air inlets and outlets, barn airflows, operational processes, and environmental variables. A multipoint gas sampling system delivers selected air streams to gas analyzers. Mass PM concentrations are measured at one representative exhaust location per barn using real-time monitors. Motion sensors monitor activity of animals, workers and vehicles. Building ventilation rate is assessed by monitoring fan operation and building static pressure in mechanically ventilated barns, and air velocities through ventilation openings in naturally-ventilated buildings. Data is logged every 15 and 60 s and retrieved with network-connected PCs, formatted, validated, processed, and delivered to the U.S. Environmental Protection Agency (EPA).

Ventilation rates in large commercial layer hen houses with two-year continuous monitoring.

1. Ventilation controls the indoor environment and is critical for poultry production and welfare. Ventilation is also crucial for assessing aerial pollutant emissions from the poultry industry. Published ventilation data for commercial layer houses have been limited, and are mostly based on short-term studies, mainly because monitoring airflow from large numbers of fans is technically challenging. 2. A two-year continuous ventilation monitoring trial was conducted at two commercial manure belt houses (A and B), each with 250 000 layers and 88 130-cm exhaust fans. All the fans were individually monitored with fan rotational speed sensors or vibration sensors. Differential static pressures across the house walls were also measured. Three fan performance assessment methods were applied periodically to determine fan degradations. Fan models were developed to calculate house ventilations. 3. A total of 693 and 678 complete data days, each containing >16 h of valid ventilation data, were obtained in houses A and B, respectively. The two-year mean ventilation rates of houses A and B were 2·08 and 2·10 m3 h−1 hen−1, corresponding to static pressures of −36·5 and −48·9 Pa, respectively. For monthly mean ventilation, the maximum rates were 4·87 and 5·01 m3 h−1 hen−1 in July 2008, and the minimum were 0·59 and 0·81 m3 h−1 hen−1 in February 2008, for houses A and B, respectively. 4. The two-year mean ventilation rates were similar to those from a survey in Germany and a 6-month study in Indiana, USA, but were much lower than the 8·4 and 6·2 m3 h−1 hen−1 from a study in Italy. The minimum monthly mean ventilation rates were similar to the data obtained in winter in Canada, but were lower than the minimum ventilation suggested in the literature. The lower static pressure in house B required more ventilation energy input. The two houses, although identical, demonstrated differences in indoor environment controls that represented potential to increase ventilation energy efficiency, and reduce carbon footprints and operational costs.

Ammonia and Hydrogen Sulfide Emissions from Naturally Ventilated Free-Stall Dairy Barns

Emissions of ammonia (NH3) and hydrogen sulfide (H2S) from two naturally-ventilated freestall dairy barns are presented in this paper. Barn 1 (B1) housed 400 fresh-lactating cows, while Barn 2 (B2) housed 850 non-fresh-lactating cows. The relationships between NH3 and H2S emissions and environmental factors (temperature, wind speed, and relative humidity) were evaluated. Average emissions of NH3 (32.3 g/d-cow) from the smaller B1 were approximately two times as the average emissions (16.6 g/d-cow) from the larger B2. Average emissions of H2S, however, were similar at 2.05 and 1.74 g/d-cow from B1 and B2, respectively. Average emissions of NH3 and H2S were highest in summer (July) at 44.2 and 2.78 g/d-cow from B1, and 23.2 g and 1.92 g/d-cow from B2, respectively. The lowest emissions, on the other hand, were observed in winter (January) at 27.8 and 1.92 g/d-cow from B1, and 10.2 and 0.87 g/d-cow from B2, respectively. In general, emissions of NH3 increased with temperature (R2=0.87) and wind velocity (R2=0.77), while inverse relationships were observed between NH3 emissions and relative humidity (R2=0.84). The correlations between H2S emissions and the same environmental parameters, in general, were poor (R2 = 0.01). Significant spikes of H2S emissions were observed during manure-flushing events.

A Method for Determination of Pollutant Emissions from Naturally Ventilated Freestall Dairy Barns

In mechanically-ventilated freestall dairy barns, pollutant emissions can accurately be determined from the differences in concentrations between the influent and exhaust gases and the measured flow of the ventilating air. In contrast, emissions from naturally ventilated (NV) freestall dairy barns do not have well defined specific air entry or exit points. In addition, pertinent airflow characteristics (velocity and direction) vary continuously, both temporally and spatially. This scenario significantly complicates the determinations of emissions. This paper examines a method being developed and tested for determining emissions from NV livestock barns. The method essentially entails placement of sonic anemometers (to measure air movement in and out of the structure) at salient points all around the barn in order to determine the airflow characteristics. Air samples are simultaneously collected at these selected points to determine the respective representative concentrations of the air entering or leaving the barn over a given sampling cycle or time. The airflow data is subsequently coupled with pollutant concentrations data to determine respective emissions from the barn. Results indicate credibility of sonic anemometers in the determination of ventilation characteristics in naturally ventilated barns, which are critical to accurate determination of pollutant emissions calculations from such barns.

Fan Monitoring and Ventilation Rate Calculation at Two Large Commercial Layer Barns

The ventilation rate has equal importance as pollutant concentration when determining air pollutant emissions from barns at concentrated animal feeding operations (CAFOs), as the emission rate is the product of ventilation rate and pollutant concentration. This paper evaluated fan monitoring and performance verification technologies, and fan model development methodology for a large commercial layer farm emission measurement site, where there were two manure belt barns, each equipped with 88 exhaust fans that housed 250,000 layers. All the fans were individually and continuously monitored with fan rotational speed (FRS) sensors or vibration sensors. Differential static pressures (â–³Ps) across the walls of each barn were also continuously measured with pressure transducers. The Fan Assessment Numeration System (FANS) and fan airflow traverse method were applied periodically to assess the actual fan performance at barn conditions. Two groups of fan ventilation models, each with three speed regimes of high, medium and low FRS, were developed based on off-site laboratory fan chamber tests, on-site fan performance checks, and the first and second fan laws. The corresponding degradation factors of the fan models were also estimated. The mean ventilation rates of the two barns from Jan. 1 to Dec. 31, 2009 were calculated. Barn ventilations was influenced by indoor temperature variations, FRS, â–³Ps conditions and fan performance degradation situations.