Sanjay B. Shah

Measuring Ammonia Concentrations and Emissions from Agricultural Land and Liquid Surfaces: A Review

Abstract Aerial ammonia concentrations (C g) are measured using acid scrubbers, filter packs, denuders, or optical methods. Using C g and wind speed or airflow rate, ammonia emission rate or flux can be directly estimated using enclosures or micrometeorological methods. Using nitrogen (N) recovery is not recommended, mainly because the different gaseous N components cannot be separated. Although low cost and replicable, chambers modify environmental conditions and are suitable only for comparing treatments. Wind tunnels do not modify environmental conditions as much as chambers, but they may not be appropriate for determining ammonia fluxes; however, they can be used to compare emissions and test models. Larger wind tunnels that also simulate natural wind profiles may be more useful for comparing treatments than micrometeorological methods because the latter require larger plots and are, thus, difficult to replicate. For determining absolute ammonia flux, the micrometeorological methods are the most suitable because they are nonintrusive. For use with micrometeorological methods, both the passive denuders and optical methods give comparable accuracies, although the latter give real-time C g but at a higher cost. The passive denuder is wind weighted and also costs less than forced-air C g measurement methods, but it requires calibration. When ammonia contamination during sample preparation and handling is a concern and separating the gas-phase ammonia and aerosol ammonium is not required, the scrubber is preferred over the passive denuder. The photothermal interferometer, because of its low detection limit and robustness, may hold potential for use in agriculture, but it requires evaluation. With its simpler theoretical basis and fewer restrictions, the integrated horizontal flux (IHF) method is preferable over other micrometeorological methods, particularly for lagoons, where berms and land-lagoon boundaries modify wind flow and flux gradients. With uniform wind flow, the ZINST method requiring measurement at one predetermined height may perform comparably to the IHF method but at a lower cost.

Ammonia Adsorption in Five Types of Flexible Tubing Materials

Five different types of tubing materials, namely, polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP), high density polyethylene (HDPE), and polyvinyl chloride (PVC) were evaluated for ammonia adsorption at two nominal ammonia concentration values (1 and 10 ppm) at ~24°C. All tubing sections were 2.5 m in length and 4.76 mm in i.d. except the HDPE which had an i.d. of 4.32 mm. Mass balance was used to determine ammonia (as ammonium-nitrogen (N)) adsorbed on the inside of the tubing versus the total N recovered in the tubing plus the gas scrubbers (primary and secondary). No tubing significantly differed in N adsorption. Averaged for both ammonia concentrations, N adsorption as percent of total N ranged from 0.15% (PVC) to 1.69% (FEP). Hence, the least expensive PVC tubing may represent the best option under conditions similar to those used in this study. The gas scrubber design used in this study had excellent trapping efficiency (>99%).

Modeling Ammonia Emissions from Broiler Litter at Laboratory Scale

The objectives of this study were to develop a mechanistic emission model to estimate ammonia flux from broiler litter and to evaluate the model at laboratory scale. In the proposed model, the ammonia flux is essentially a function of the litters total ammoniacal nitrogen (TAN) content, moisture content, pH, and temperature, as well as the Freundlich partition coefficient (Kf), mass transfer coefficient (KG), ventilation rate (Q), and emission surface area (A). The Freundlich partition coefficient (Kf) was used as a fitting parameter in the model. A dynamic flow-through chamber system and a wind tunnel were designed to measure ammonia fluxes from broiler litter. The dynamic flow-through chamber experiments evaluated the proposed model with various litter samples under a constant temperature and wind profile. The wind tunnel experiments evaluated the proposed model under various temperatures and wind profiles. Model parameters such as Kf and KG were estimated. The results from the two experiments were consistent with each other. The estimated KG ranged from 1.11 to 27.64 m h-1, and the estimated Kf ranged from 0.56 to 4.48 L kg-1. A regression sub-model was developed to estimate Kf as function of litter pH and temperature, which indicated that Kf increased with increasing litter pH and decreased with increasing temperature. The proposed model was used to estimate the equilibrium gas phase ammonia concentration (Cg,0) in litter, and the model-predicted values were compared with the observed values. The normalized mean error (NME), the normalized mean square error (NMSE), and fractional bias (FB) were calculated to be 25%, 12%, and -0.3%, respectively, for all 94 measurements, and the model was able to reproduce 80% of the variability of the data. Sensitivity analysis of the model showed that ammonia flux is very sensitive to litter pH and to a lesser extent temperature. The relative sensitivity of pH or temperature increases as the pH or temperature increases.

Design and Evaluation of a Regenerating Scrubber for Reducing Animal House Emissions

Animal houses can emit substantial quantities of air pollutants. Compared with other pollutants, ammonia is emitted from animal houses in relatively large quantities and can have adverse public health and environmental impacts. This article describes the development and evaluation of a novel scrubber prototype, consisting of an endless polypropylene screen running in a trough of alum solution, that could be used to reduce ammonia emissions from animal houses. When building exhaust ventilation air contacts the screen, ammonia is dissolved in the aqueous solution on the screen and transported into the trough. Low ammonia concentration ( 66 h of evaluation under low and high concentration conditions, with a weighted average airflow rate of 0.93 m3 s-1 and velocity of 0.52 m s-1, the scrubber reduced ammonia emissions by 58.3%. Compared with commercial spray and packed column scrubbers used in industry, it had a lower pressure drop (~110 Pa). It also had a low water consumption of ~1 mL m-3 treated air. Further evaluation of the scrubber in different types of animal houses and for different pollutants is required. Its design should be improved to increase ammonia removal efficiency and reduce pressure drop, footprint size, and cost. There is also need to model gas transfer in this type of scrubber.

Design and Operation of a Biofilter for Treatment of Swine House Pit Ventilation Exhaust.

A down-flow biofilter was designed to treat exhaust air from a swine barn pit ventilation fan in Raleigh, NC. Computational Fluid Dynamics was used to model airflow to ensure spatial uniformity of treatment. The biofilter medium consisted of ~70% compost and 30% woodchips by volume. The biofilter was evaluated during August 2010 through April 2011 under different summer, fall, and winter conditions. The medium depth was 0.3 m, empty bed residence time (EBRT) was 7.6 s, residence time was 2.7 s, and the biofilter had a unit airflow rate (U) of 0.04 m3/m2-s. A photoacoustic multi-gas field monitor (Innova) was used to measure concentrations of ammonia, carbon dioxide, methane, and nitrous oxide. The Innova was evaluated with regard to its response time for ammonia, nitrous oxide, and methane. Boric acid scrubbers were also used to measure time averaged ammonia concentrations. Air samples were collected and analyzed in a gas chromatograph (GC) for methane and VOCs. Operating conditions such as temperature, medium moisture content, and system pressure drop were measured during biofilter operation. Pressure drop across the fan averaged 125 Pa. The biofilter’s removal efficiencies (RE) for ammonia ranged from 89 to 92%. Greenhouse gases methane and nitrous oxide REs ranged from 13 to 50% and 14 to 17% respectively, while carbon dioxide REs ranged from -6 to 37%. Results show that the biofilter can be effective at removing gases such as ammonia, but also, methane and nitrous oxide. The cost of the system was

Fine Particulate Matter in a High-Rise Layer House and Its Vicinity

1,225 per 0.50 m3/s.

Leaching of Nutrients and Trace Elements from Stockpiled Turkey Litter into Soil

Fine particulate matter (PM2.5) is one of many air pollutants emitted from animal feeding operations (AFOs). Knowledge about PM2.5 in AFO production facilities and their vicinity is important for studies of its impact on health, animal welfare, and the environment. However, very little information is available about PM2.5 concentrations and emissions, and their spatial and temporal variations, associated with egg production facilities. In this study, Partisol 2300 PM2.5 speciation samplers were used to take daily PM2.5 samples in a high-rise layer house and at four ambient stations. The sampling period covered four seasons, with a total of 300 samples. The results showed that none of the ambient PM2.5 concentrations exceeded the 35 µg m-1 (24 h) and 15 µg m-1 (annual) PM2.5 National Ambient Air Quality Standards (NAAQS). The ambient stations and the in-house station showed strong seasonal variations; the ambient stations had the highest PM2.5 concentrations in summer, and the in-house station had the highest concentration in winter. Based on the gamma distribution, 95% confidence intervals of PM2.5 emissions (mg PM2.5 d-1 hen-1) were [7.86, 11.4]. The downtime PM2.5 concentration mean was one-tenth that of the occupied house. PM2.5 concentrations were negatively correlated with ambient RH, egg production, and ventilation rate. Statistical tests did not show a strong correlation between ambient PM2.5 concentrations and emissions from the layer house. This study adds to a growing body of research assessing the environmental impact, air quality, emissions of AFOs and the relationship between PM2.5 and the environmental and farm management inventory information.

Particulate Matter in the Vicinity of an Egg Production Facility: Concentrations, Statistical Distributions, and Upwind and Downwind Comparison

In addition to nutrients, poultry are fed trace elements (e.g., As) for therapeutic purposes. Although a large proportion of the nutrients are assimilated by the birds, nearly all of the As is excreted. Hence, turkey litter constituents can leach into the soil and contaminate shallow ground water when it is stockpiled uncovered on bare soil. This study quantified the leaching of turkey litter constituents from uncovered stockpiles into the underlying soil. Four stockpiles were placed on Orangeburg loamy sand in summer 2004 for 162 d; 14 d after their removal, four stockpiles were created over the same footprints and left over winter for 162 d. Soil samples at depths of 7.6 to 30.5 cm and 30.5 to 61 cm adjacent to and beneath the stockpiles were compared for pH, electrical conductivity, total C, dissolved organic C, N species, P, water-extractable (WE)-P, As, WE-As, Cu, Mn, and Zn. All WE constituents affected the 7.6- to 30.5-cm layer, and some leached deeper; for example, NH(4)(+)-N concentrations were 184 and 62 times higher in the shallow and deep layers, respectively. During winter stockpiling, WE-As concentrations beneath the stockpiles tripled and doubled in the 7.6- to 30.5-cm and 30.5- to 61-cm layers, respectively, with WE-As being primarily as As(V). Heavy dissolved organic C and WE-P leaching likely increased solubilization of soil As, although WE-As concentrations were low due to the Al-rich soil and low-As litter. When used as drinking water, shallow ground water should be monitored on farms with a history of litter stockpiling on bare soil; high litter As; and high soil As, Fe, and Mn concentrations.

Acidifier Dosage Impacts on Ammonia Concentrations and Emissions from Heavy-Broiler Houses

Animal feeding operations (AFOs) satisfy the demand for meat, dairy, and eggs; however, they may negatively impact air quality. In this study, the concentrations of PM2.5 and PM10 were simultaneously monitored at four ambient locations in the vicinity of a commercial egg production farm for over two years. Overall, concentrations and temporal patterns were similar to other rural sites in the southeast U.S. Concentrations near the farm property line did not exceed the 24 h National Ambient Air Quality Standards (NAAQS) for PM2.5 (35 µg m-3) or PM10 (150 µg m-3). Daily average ambient PM concentrations were best described by a lognormal distribution. Downwind concentrations were statistically significantly higher than upwind concentrations, but differences were <1.0 µg m-3 for PM2.5 and <5.0 µg m-3 for PM10. Relationships between ambient PM concentrations and rates of PM emission from the poultry houses were statistically significant; however, the strength of the linear relationships (Pearson correlation) was relatively weak (r = 0.15 for PM10 and r = 0.33 for PM2.5). On a diurnal time scale, variability was consistent with expected patterns of mobile source emissions, with observed higher concentrations of PM10 on weekdays attributed to on-farm vehicle activity. The observation of higher ambient PM concentrations during summer months was attributed primarily to seasonal variability in non-local primary PM emissions, as well as regional secondary PM precursor emissions and formation mechanisms. Results of this study provide helpful information for understanding the influence of emissions from egg laying facilities on local PM concentrations.

Value-addition of methane via selective catalytic oxidation

Broiler production results in the production of ammonia, and at high concentrations, ammonia can affect bird performance, and hence, productivity. When released into the environment through ventilation, ammonia can adversely affect public health and the environment. Because of its environmental and health impacts, ammonia emissions from animal feeding operations may be regulated by the EPA. Acidifying amendments have been shown to be effective in reducing ammonia emissions from poultry operations. The purpose of this study is to evaluate in-house ammonia concentrations and emissions from four commercial heavy-broiler houses in eastern North Carolina receiving four levels of PLT® (a commercial amendment): control (0.37 – 0.49 kg/m2 center brood area), low (0.37 – 0.49 kg/m2 whole house), medium (0.73 kg/m2 whole house), and high (>0.73 kg/m2 whole house). Ammonia concentrations were measured with acid scrubbers and ammonia emissions were calculated from exhaust ammonia concentrations and ventilation volumes. Based on monitoring of three flocks (September 2007 to May 2008), in-house ammonia-N concentrations decreased with increasing PLT application rates. A medium application rate was adequate for maintaining ammonia levels at or below 25 ppm for 9-wk grow-out period during the spring. Based on data from three flocks, ammonia emission factors (only grow-out) for the control, low, medium, and high treatments were 1.06, 1.12, 0.97, and 0.92 g/bird-d, respectively. These emission factors are mostly higher than those reported in the literature mainly because they represent heavier (>4 kg) and older (9-wk) birds fed a higher protein diet. Acid scrubbers proved to be suitable for measuring time-averaged ammonia concentrations for a wide range of values. Emissions data will be collected for four more flocks and PLT impacts on bird performance and energy use will also be quantified.