Douglas G. Overhults

Use of CO2 Concentration Difference or CO2 Balance to Assess Ventilation Rate of Broiler Houses

Ventilation rate (VR) is one of the two key elements for quantifying aerial emissions from animal production facilities. Direct, continuous measurement of building VR can be challenging and impractical under certain circumstances, e.g., naturally ventilated animal housing or a large number of ventilation fans in the building. This study examined the suitability of estimating VR of broiler houses with built-up litter (mixture of manure and bedding), when supplemental heating was not in use, through either carbon dioxide (CO 2 ) balance or the relationship of VR to CO 2 concentration difference between exhaust and inlet air. The reference VR was based on direct measurement by continuously monitoring operation of the in-situ calibrated exhaust fans. The comparative analysis of the direct method vs. each indirect method was conducted for a measurement integration time (MIT) of 10, 30, 60, or 120 min. The analyses revealed that MIT of 30 min or greater resulted in non-significant differences in VR between the indirect and direct methods. The broiler building VR (m 3 s -1 ) may be related to the exhaust-inlet CO 2 concentration difference (ΔCO 2 , ppm) as VR (±3.0) = 4456 (±41) ΔCO 2 -0.786 (±0.019) at 30 min MIT. The VR may also be determined by the CO 2 balance method (including litter CO 2 generation) with a correction factor of 0.97 at MIT of 30 to 120 min. If litter CO 2 generation is omitted from the total building CO 2 production, the actual VR may be estimated by applying a correction factor of 1.077 to the bird respiration CO 2 balance VR. Hence, the CO 2 balance or concentration difference method offers a viable alternative or supplemental check for quantifying building VR under certain conditions where direct, continuous VR measurement is not feasible.

Regional Variation in Temperature Humidity Index for Poultry Housing

A building thermal model was used to compute hourly values of temperature humidity index (THI) for a broiler house with and without an evaporative misting system. Hourly summer time weather data for 238 U.S.A. locations covering 30 years were used to develop extreme occurrences of THI. Results were incorporated into a Geographical Information System (GIS) database to create isolines of THI and percentage of hours exceeding a heat stress threshold. Regional variations in misting as a suitable cooling technique are presented in terms of hours reduction in annual heat stress. The technique may be used for assisting in management decisions regarding poultry facilities housing design and siting, and with appropriate THI may be extended to other livestock production.

Minimum Ventilation for Modern Broiler Facilities

New functions for whole-house broiler heat production as a function of bird age using modern straight run broiler growth rates are presented and compared to values in the literature. The approximations are based on field measurements of environmental conditions in modern broiler housing, using a technique that matches predicted to actual fuel use to estimate partitioning between latent and sensible heat. Development of a program utilizing these approximations to compute ventilation and heating requirements for temperature and humidity control in broiler housing is described. The program utilizes steady-state heat and moisture balances commonly used for design purposes, with hourly or daily time steps. Data input includes bird weight and numbers, house data including overall R-value and size, inside and outside temperature, and relative humidity. The program estimates ventilation for temperature and moisture control, minimum ventilation rate, and supplemental heat required. Example predictions are provided.

Ammonia Emissions from Broiler Houses in the Southeastern United States

Continuous monitoring of ammonia (NH3) emissions from two mechanically ventilated commercial broiler houses located in the southeastern United States was performed during a one-year period over 2005-2006 as a joint effort between Iowa State University and the University of Kentucky. Ammonia concentrations were measured using Innova 1412 photoacoustic NH3 monitors. Ventilation rates in each house were measured continuously by monitoring the 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. Expressed in various units, NH3 emissions from the two broiler houses over the one-year production period were of the following values: a) 35.4 g per bird marketed (77.9 lb per 1,000 birds marketed), including both grow-out (50-54 d per flock) and downtime (12-25 d between flocks) emissions; b) annual (365-d) emission of 4.63 Mg (5.1 US tons) per house, including both grow-outs and downtime; c) maximum grow-out daily emission of 30.6 kg/d-house (67.4 lb/d-house) for one house and 35.5 kg/d-house (78.2 lb/d-house) for the other; d) mean grow-out daily emission of 14.0 ± 9.1 ( S.D.) kg/d-house; e) mean downtime daily emission of 8.8 ± 8.3 kg/d-house. Flocks on new bedding had a lower emission rate of 12.4 ± 9.4 kg/d-house, as compared to 14.5 ± 8.9 kg/d-house for flocks on built-up litter. The NH3 emission factor of 35.4 g/bird marketed from this study is substantially lower than that cited by US EPA of 100 g/yr-bird (the US EPA yr-bird unit is equivalent to bird marketed).

Limiting Swine Stress with Evaporative Cooling in the Southwest

ABSTRACT Three-Hourly weather data for 7 locations in the Southeast and Central United States were used to evaluate the feasibility of evaporative cooling for reducing swine stress. Stress was defined as a relationship between dry and wet bulb temperatures which exceeded a stress index of 85. This analysis indicates that properly installed evaporative coolers could reduce the number of hours that stress would occur in swine facilities from 89.6 to 96.4% depending on location.

Quantification of Particulate Emissions from Broiler Houses in the Southeastern United States

Emissions of total suspended particulate (TSP), particulate matter with aerodynamic diameters = 10 µm (PM10), and = 2.5 µm (PM2.5) were continuously monitored at two mechanically ventilated broiler houses in the southeastern United States. Monitoring was performed over a one-year period during 2005-2006 as a joint effort between Iowa State University and the University of Kentucky. Tapered Element Oscillating Microbalances (TEOMs) were used to measure three species of particulate matter (TSP, PM10 and PM2.5). Ventilation rates were measured continuously by monitoring building static pressure and operational status of ventilation fans in conjunction with individual performance curves developed and verified in situ using a Fan Assessment Numeration System (FANS) unit. The magnitude of the TSP, PM10 and PM2.5 emissions are reported as a) annual house total emission and b) on a per 1,000 birds marketed basis. These emission values are: a) 785 kg (1,731 lb) TSP, 330 kg (727 lb) PM10, and 32.5 kg (71.7 lb) PM2.5 per house per year and b) 6.03 kg (13.3 lb) TSP, 2.52 kg (5.56 lb) PM10, and 0.25 kg (0.55 lb) PM2.5, per 1,000 birds marketed. Bird age is the predominant factor influencing particulate emissions. An empirical equation is presented that relates emissions to bird age for the monitored broiler houses. The use of a daily emission factor is not advised for broiler production systems or others in which substantial progressive animal growth occurs over time. The use of emissions per 1,000 birds marketed more realistically expresses emissions and allows for improved emissions inventory tracking.

Greenhouse Gas (GHG) Emissions from Broiler Houses in the Southeastern United States

Greenhouse gas (GHG) emissions, including carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), from broiler houses located in the southeastern United States were continuously monitored over a one-year period. The birds were grown to 52 days of age at an average stocking density of 11.8 birds/m2 (1.1 birds/ft2). Methane and CO2 emissions were measured in two broiler houses while N2O emissions were measured in one house. Carbon dioxide and N2O concentrations were measured using a photoacoustic multi-gas analyzer and CH4 concentrations were measured using a dual-channel methane/non-methane-hydrocarbon (NMHC)/total hydrocarbon analyzer with dual flame ionization detectors. Ventilation rates in each house were continuously calculated by monitoring the building static pressure and operational status of all ventilation fans in conjunction with individual fan performance curves developed and verified in situ using a Fan Assessment Numeration System (FANS) unit. Annual CO2 emissions measured from the two broiler houses averaged 606 Mg (668 US tons) per house. On a marketed bird basis the CO2 emissions averaged 4.64 Mg (5.49 US tons) per 1,000 birds marketed. Annual CH4 emissions averaged 445 kg (982 lbs) per house, or 3.41 kg (7.52 lbs) per 1,000 birds marketed. Annual N2O emissions measured from one broiler house was 225 kg (496 lbs) per house, or 1.72 kg (3.8 lbs) per 1,000 birds marketed. The CO2 equivalents of the CH4 and N2O emissions were, respectively, 85.3 kg (188 lb) and 512.6 kg (1,128 lb) per 1,000 birds marketed. Hence the total CO2 equivalent GHG emissions for the broiler operations monitored in this study were 5.238 Mg per 1,000 birds marketed, with 88.6% contributed by CO2.

Field Calibration of a Transient Model for Broiler Misting

A transient model to predict temperature within a tunnel ventilated broiler house during misting is developed. The model is calibrated with field data to obtain steady-state constants; transient predictions are compared to measured temperatures during cyclic misting for two different size birds. Measured temperatures during cyclic misting are shown to swing between steady-state asymptotes predicted from the model. Transient response of the model was faster than measured temperature data, in part due to temperature sensor dynamic response. The model predicts the length-wise temperature profile within the building during misting, and can be used to investigate alternate misting strategies and designs. Further improvements to the model are suggested.

Comparison between two systems for ammonia emission monitoring in broiler houses

This work aimed to compare two systems used for ammonia emission monitoring in broiler houses. The low cost PMU (Portable Monitoring Unit), and MAEMU (Mobile Air Emission Monitoring Unit) are systems used for ammonia concentration monitoring and, with broiler house ventilation rate, ammonia emission rate (ER) can be calculated. The accuracy of ammonia emission rate calculated with data from the PMU using a simplified calculation algorithm was quantified using the MAEMU as a standard.

Use of CO2 Concentrations or CO2 Balance to Estimate Ventilation Rate of Modern Commercial Broiler Houses

Ventilation rate (VR) is one of the two key elements for quantifying aerial emissions from animal production facilities. Direct measurement of building VR can be challenging and impractical under certain circumstances, e.g., naturally ventilated animal housing. This study delineates VR of broiler houses with build-up litter as estimated via CO2 balance or building CO2 concentration. The indirectly derived VR compared favorably with the directly measured VR. Specifically, integration time of 30 min or longer leads to non-significant differences in VR between the indirect and the direct methods (P>0.2). Omission of CO2 generation by the litter from total house CO2 production results in an overall 7% underestimation of the building VR. The indirect method provides a possible, viable alternative for quantifying VR of naturally ventilated broiler confinement.