E. F. Wheeler

Fan Assessment Numeration System (FANS) Design and Calibration Specifications

A device for insitu fan airflow measurement, known as the Fan Assessment Numeration System (FANS) device, previously developed and constructed at the USDAARS Southern Poultry Research Laboratory, was refined at University of Kentucky as part of a project for quantifying building emissions from mechanically ventilated poultry and livestock facili- ties. The FANS incorporates an array of five propeller anemometers to perform a realtime traverse of the airflow entering fans of up to 137 cm (54 in.) diameter. Details of the updated design, including hardware, software, and calibration methodolo- gy are presented. An error analysis of the flow rate, and calibration results from ten FANS units, is provided. Sufficient details of fabrication and calibration are presented so that interested readers can replicate a FANS for their use. Full design details are available at www.bae.uky.edu/IFAFS/FANS.htm.

Ammonia Emissions from U.S. Laying Hen Houses in Iowa and Pennsylvania

Ammonia (NH3) emission rates (ER) of ten commercial layer houses (six high-rise or HR houses and four manure- belt or MB houses) with different manure handling or dietary schemes were monitored for one year in Iowa (IA) and Pennsylvania (PA). Gaseous (NH3 and CO2) concentrations of incoming and exhaust air streams were measured using custom-designed portable monitoring units that shared similar performance to EPA-approved measurement apparatus. Building ventilation rates were determined by calibrated CO2 mass balance using the latest metabolic rate data for modern laying hens. The field monitoring involved a total of 386 and 164 house-day measurements or 18,528 and 7,872 30-min emission data points for the HR houses and the MB houses, respectively. The ER showed considerable diurnal and seasonal variations. The annual mean ERs (g NH3 hen-1 d-1) and standard errors were 0.90 ±0.027 for IA-HR houses with standard diet, 0.81 ±0.02 for IA-HR houses with a nutritionally balanced 1% lower crude protein diet, 0.83 ±0.070 for PA-HR houses with standard diet, 0.054 ±0.0035 for IA-MB houses with daily manure removal, and 0.094 ±0.006 for PA-MB houses with twice a week manure removal. Mass balance of nitrogen (N) intake and output performed for IA-HR houses revealed a total N intake recovery of 94% to 101%, further verifying the certainty of the NH3 ER measurements. Results of the study contribute to the U.S. national inventory on NH3 emissions from animal feeding operations, particularly laying hen facilities as affected by housing type, manure handling scheme, crude protein content of the diet, and geographical location.

Ammonia Emissions from Twelve U.S. Broiler Chicken Houses

Twelve commercial broiler houses in the U.S. were each monitored for at least thirteen 48 h periods over the course of one year to obtain ammonia emission data. Paired repetition of houses on four farms represents current construction with variety in litter management (built-up or new litter each flock) and climate conditions (cold or mixed-humid). Ammonia concentration was determined using portable electrochemical sensors incorporating a fresh air purge cycle. Ventilation rate was determined via in-situ measurement of fan capacity, fan on-off times, and house static pressure difference. There were seasonal trends in exhaust ammonia concentration (highest in cold weather) and ventilation rates (highest in warm weather) but not for emission rate. Flocks with at least three monitoring periods (13 of 22 flocks) demonstrated similar emission rates at a given bird age among the four study farms and across the seasons. An analysis of emissions from all houses on the three farms using built-up litter resulted in predicted regression slopes of 0.028, 0.034, and 0.038 g NH3 bird-1 d-1 per day of age; the fourth farm, managed with new litter, had the lowest emission rate at 0.024 g NH3 bird-1 d-1. The intercept of these composite relationships was influenced by litter conditions, with flocks on new litter having essentially no emissions for about six days while built-up litter flocks had emissions starting at flock placement. Data from all four farms and all flocks provided a regression slope of 0.031(±0.001 std error) g NH3 bird-1 d-1 per day of age. Emission rate per animal unit for built-up litter flocks indicated very high emissions for the youngest birds (under 14 days of age), after which time the emissions decreased exponentially and were then relatively steady for the balance of the flock cycle.

A Portable System for Continuous Ammonia Measurement in the Field

A portable and relatively low-cost monitoring unit (PMU) for continuous measurement of ammonia and carbon dioxide in CAFO (poultry in particular) applications has been developed and partially compared with an EPA-approved measurement method. The PMU utilizes sampling and purging cycles to overcome the sensor saturation characteristic of electro-chemical NH3 sensors. Preliminary comparative results show that performance of the PMU is quite comparable to the sophisticated, highercost, and less portable mobile lab method. For the range of ammonia level typical of commercial poultry buildings, the PMU is expected to produce emission rate data of reasonable quality when combined with properly measured or determined building ventilation rate.

COMPARISON OF DIRECT VS. INDIRECT VENTILATION RATE DETERMINATIONS IN LAYER BARNS USING MANURE BELTS

Direct measurement of building ventilation rate in livestock housing is a formidable task due to uncontrollable variations in fan and system performance that are caused by factors such as building static pressure, fan belt slippage, and dust accumulation on shutters and blades. Estimating building ventilation rate by an indirect method based on a CO2 balance offers a potentially viable alternative to direct measurement. The validity of the CO2 balance method depends on the validity of relationship between CO2 production inside the building and metabolic rate of the animals and the knowledge of CO2 generation by the housing environment. Metabolic rates of modern laying hens have recently been quantified in intensive large-scale laboratory measurements. However, performance of the indirect method remains to be evaluated under field conditions. This article compares building ventilation rates obtained by direct measurement and by a CO2 balance. The test was conducted at a commercial laying hen house that used manure belts with daily manure removal. The results indicate that ventilation rates estimated by the indirect method were not significantly different (P > 0.2) from those as determined by the direct measurement when the averaging or integration time interval was 2 h or longer. Careful application of the indirect method could greatly improve the affordability and versatility of endeavors toward quantifying air emissions from confined animal housing.

TEMPERATURE EFFECTS ON WASTEWATER NITRATE REMOVAL IN LABORATORY-SCALE CONSTRUCTED WETLANDS

Constructed wetlands may be used for removal of high nutrient loads in greenhouse wastewater prior to discharge into the environment. Temperature affects both the physical and biological activities in wetland systems. Since nitrification and denitrification are temperature-dependent processes, effluent nitrate concentrations will fluctuate due to changes in air and wetland temperature. In a cold climate, constructed wetlands can function in a temperature-controlled, greenhouse environment year-round. This work evaluates four temperature treatments on nitrate removal rates in five planted and five unplanted laboratory-scale wetlands. Wetlands were supplied with a nutrient solution similar to the fertigation runoff solution (100 PPM nitrate-N) used in greenhouse crop production. A first-order kinetic model was used to describe experimental nitrate depletion data and to predict nitrate removal rate constants (k) in the wetlands planted with Iris pseudocoras. The negligible removal in unplanted wetlands was thought to be due to lack of carbon source in the fertigation solution. Between 18 and 23°C in planted systems, k increased from 0.062 to 0.077 h–1, appeared to peak around 30°C (k = 0.184 h–1), but decreased at 38°C (k = 0.099 h–1). Based on the Arrhenius equation, k was a first-order exponential function of temperature between 18 and 30°C in planted systems. Quantification of temperature effects on planted and unplanted laboratory-scale constructed wetlands can be used to enhance the design and management of wastewater treatment wetlands.

Ammonia and Greenhouse Gas Flux from Manure in Freestall Barn with Dairy Cows on Precision Fed Rations

Two lactating cow trials were conducted to evaluate the impact of diets differing in silage source (alfalfa/maize vs. grass/maize or maize/hay) and maize grain particle size (fine vs. coarse) on ammonia (NH3), carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions from a freestall barn floor with two groups of 60 cows each. In addition, the effects of environment (temperature, humidity) and management (manure depth, time since manure removal) factors were evaluated. Manure (feces and urine), spilled feed, bedding, and spilled drinking water were allowed to collect on the solid concrete, sloped barn alleys and were scraped twice a day. Gas fluxes from the freestall floor were measured at 64 locations over a 12 h period using a fast-response, non-steady-state flux chamber and an infrared photoacoustic gas analyzer during 18 trial days over a 9-month period. Fluxes of ammonia from manure on the barn floor were within average reported values for these 165 g kg-1 crude protein diets. All gas fluxes were similar (p = 0.253 to 0.977) regardless of silage source and maize grain particle size. The highest average ammonia emissions coincided with higher environmental temperature at 30 NH3 g AU-1 d-1, while the highest average greenhouse gas emissions from the manure on the floor were 10 g AU-1 d-1 for CH4 and 580 g AU-1 d-1 for CO2. Time in hours since scraping the floor had little impact on the production of ammonia, but greenhouse gas loss from the barn floor was reduced after scraping. Air and manure temperatures were positively correlated with emissions of NH3, CO2, and CH4 (p = <0.0001). NH3 (g AU-1 d-1) = (R2 = 0.38) for indoor air temperatures (Tair, °C) over the range from -5°C to 32°C (AU = 500 kg animal unit). Ammonia emissions were positively correlated with CO2 and CH4 gas emissions, suggesting that NH3 release from the manure was controlled to some extent by microbial activity and similar environmental factors. Nitrous oxide emissions remained <0.1 g AU-1 d-1 and were relatively constant for all diets and trials.

Field Estimation of Ventilation Capacity Using FANS

Instrumentation and procedures have been developed to characterize mechanical ventilation system capacity as part of an evaluation of ammonia emissions from commercial poultry housing. A FANS anemometer array unit, developed at the Mississippi USDA center, built and refined at University of Kentucky, and calibrated at the BESS laboratory, was found to have repeatability in the range of about 1% between two traverse readings performed one after the other. The unit was used to measure broiler house fans under typical system static pressure differences. A hydraulic lift cart was fabricated to streamline FANS positioning and movement through the large poultry houses. Taping all gaps between the FANS unit and fan housing improved airflow measurements about 6% versus not taping. Using a duct to transition down to 36-inch fans resulted in a 2.5% improvement versus not using a duct. Fan manufacturer performance data was 2 to 13% higher than actual field performance.

Validation of Ammonia Emissions from Dairy Cow Manure Estimated with a Non-Steady-State, Recirculation Flux Chamber with Whole-Building Emissions

A non-steady-state flux chamber with recirculation airflow was constructed and coupled with a portable photoacoustic multi-gas analyzer to determine ammonia emissions from dairy manure. The objective of this work was to validate this flux chamber system by performing a comparison between the flux chamber emission rates and whole-building emission rates calculated from an ammonia balance in a mechanically ventilated experimental test room. It was found that flux chamber emission estimates were greatly improved with the addition of internal air recirculation to provide air velocity over the enclosed manure surface. Validation tests of the recirculation flux chamber showed a 9% to 37% underestimation of the emissions calculated from the ammonia balance (R2 = 0.72). The non-steady-state, recirculation flux chamber method can be used to estimate ammonia emissions in naturally ventilated buildings with an accuracy comparable to other available methods. However, the validation tests showed high variability in the results, which is thought to be associated with the different consistency of the manure used in the experiments and the airflow dynamics over the enclosed manure surface.

Multiple-Chamber Steady-State Gas Emission Detection from Dairy Manure Slurry

In order to evaluate gas emission reduction potential of nutritional changes in lactating dairy cattle diets, an instrumentation system was developed to rapidly and accurately evaluate multiple treatments at one time. Six steady-state flux chambers were coupled via a multiplexer relay board and software with a photoacoustic multi-gas monitor to measure the concentration of ammonia and three greenhouse gases released from manure samples every 20 minutes over 24 hours. Each chamber sweep air flow rate was maintained at 0.5 air changes per minute via a calibrated flow meter. Five chambers evaluated emissions from manure samples consisting of 100 grams each of urine and feces from each cow on trial. This 50:50 urine:feces ratio produced as much or more ammonia gas than other ratios over 1 to 24 hour periods. The sixth chamber was filled with 200 grams of demineralized water for the initial gas concentration used in calculations. Emission was represented as the integral of gas released from the manure over a chosen time period. Results from five sub-samples of collected freestall manure had a standard error of 2% of the mean emission. Instrumentation use on manure slurry from trial cows was able to differentiate between diets but explanation of results may require additional information about other factors influencing gas emission. Results suggest that this method offers repeatable, simultaneous monitoring of gas emission from manure and offers potential to evaluate factors affecting emissions thus allowing better understanding and management of on-farm gas sources.