J. Arogo

A REVIEW OF AMMONIA EMISSIONS FROM CONFINED SWINE FEEDING OPERATIONS

Ammonia emissions from swine feeding operations depend on the housing type; animal size, age, and type; manure management, storage, and treatment; climatic variables; and manure utilization or land application techniques. Techniques or methods for estimating or quantifying NH3 flux from a source to the atmosphere include nitrogen mass balance, micrometeorology, flux chambers, models, and emission factors. Of these techniques, emission factors, once established, provide the most convenience in estimating emissions. However,it is important to understand how a particular emission factor is determined and whether it accurately reflects a composite or average emission for all the variable conditons. Using an average ammonia emission factor multiplied by pig inventory to determine a regional or national ammonia emission inventory may be misleading, especially in the U.S. where existing emission factors were developed using data from swine facilities in Western Europe. Housing, manure management practices, and climate vary among different regions of the U.S. and can be very different from those in Western Europe. In addition, ammonia concentrations and emission estimations have been determined with a variety of methods, making it difficult to compare results. To determine representative ammonia emissions from confined swine feeding operations, it is important that emission factors be specific enough to account for animal type and size, housing system, manure storage and treatment, land application, and climatic effects. This article describes the strengths and limitations of emission factors as currently used and provides recommendations for determining realistic ammonia emission factors for swine feeding operations. Because of the limited nature of the data published in the literature, emission factors for different animal management systems could not be presented. Regulators, consultants, cooperative extension personnel, and other leaders in the agricultural community with interest in ammonia emissions should be aware of the lack of reliable U.S. data available for calculating accurate emission factors. The scientific research community should standardize methods for measurement, calculation, and reporting of ammonia emissions.

AMMONIA EMISSIONS FROM ANIMAL FEEDING OPERATIONS

An accepted definition of antibiotic resistance as presented in 1998 by the Institute of Medicine is “a property of bacteria that confers the capacity to inactivate or exclude antibiotics, or a mechanism that blocks the inhibitory or killing effects of antibiotics, leading to survival despite exposure to antimicrobials (Jjemba and Robertson, 2002). The occurrence of microbial pathogens demonstrating “resistance” to adverse stressors threatening their very survival is not a new (Phillips et al., 2004; WHO, 2001). Bacteria have developed mechanisms for protection in a wide range of environments over time, some of which are currently better understood due to advances in scientific methods and analytical techniques. The development of antibiotics for human and animal use dates back many years; perhaps most notable was Alexander Flemming’s creation of penicillin in 1928 (GIH, 2000). Many infectious diseases that once caused increasing mortality and morbidity rates among humans and animal populations have been effectively managed as a result of having antibiotics and pharmaceuticals available in health care management. Despite these positive outcomes, both the widespread usage and lack of prudent use of antibiotics have caused global concerns about increasing incidences of antibiotic resistance properties and strains of resistant organisms. Concerns have also increased with the recognition of greater interconnectedness between humans, animals and the environment throughout the global community. Further complicating this issue are the economic interests associated with industrial progress; hazards considered low-level and long-term seldom gain the same attention as that of crisis scenarios; and incremental knowledge about public health concerns often raises troubling questions about risk and response (GIH, 2000).

MODELING AMMONIA EMISSION FROM SWINE ANAEROBIC LAGOONS

A mathematical model to estimate ammonia emission from anaerobic swine lagoons was developed based on the classical two–film theory. Inputs to the model are wind speed and lagoon liquid properties such as total ammonia nitrogen (TAN) concentration, pH, and temperature. Predicted emission rates of ammonia increase when any of these parameters are increased, but the relationship is linear only with TAN concentration. The dissociation constant (Kd) for ammonia in lagoon liquid is also an important factor, with higher flux predictions for higher Kd. The model was validated by comparing the model outputs to measured fluxes from two lagoons in North Carolina. The predicted ammonia emission fluxes for the two lagoons ranged from 1 to 38 kg NH3–N/ha–d, which was a wider range than the fluxes measured (2.5 to 22 kg N/ha–d) by other researchers using the micrometeorological method. Compared to measured fluxes at each lagoon, the model tended to predict higher ammonia fluxes at lagoon A and lower fluxes at lagoon B when a Kd of 0.5 was used. Additional information is needed regarding ammonia dissociation (Kd) values for anaerobic lagoon liquid. Comparison of the model results with a linear regression equation indicated that the model predicted much higher fluxes at temperatures above 25 ³ C and at upper ranges of pH and wind speed. Finally, the model was used with typical lagoon TAN concentration and pH, and average monthly values for wind speed and estimated liquid temperature at Raleigh, North Carolina, to predict monthly ammonia emissions for a typical anaerobic swine lagoon in North Carolina. The highest and lowest monthly ammonia emission occurred in June and January, respectively. Based on the average monthly emissions, it is estimated that the average annual ammonia nitrogen emission rate from the surface of a typical lagoon in North Carolina would be 234 g/m 2 or 2340 kg/ha. However, the model and results from other researchers indicate that ammonia emission can vary greatly.

Ammonia emissions from anaerobic swine lagoons: Model development

Concentrated animal production may represent a significant source for ammonia emissions to the environment. Most concentrated animal production systems use anaerobic or liquid/slurry systems for wasteholding; thus, it is desirable to be able to predict ammonia emissions from these systems. A process model was developed to use commonly available measurements, including effluent concentration, water temperature, wind speed, and effluent pH. The developed model simulated emissions, as measured by micrometeorological techniques, with an accuracy that explains 70% of the variability of the data using average daily emissions and explains 50% of the variability of the data using 4-h average data. The process model did not show increased accuracy over a statistical model, but the deviations between model and measurement were distributed more evenly in the case of the process model than in the case of the statistical model.

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.

COMPARING AMMONIUM ION DISSOCIATION CONSTANT IN SWINE ANAEROBIC LAGOON LIQUID AND DEIONIZED WATER

The dissociation constant of ammonium ion both in deionized water and swine anaerobic lagoon liquid was determined experimentally in a convective emission chamber at three temperatures (15.C, 25.C, and 35.C) commonly experienced in lagoons in the south and southeastern regions of the U.S. Ammonium chloride (NH4Cl) salt was used to make the solution for the deionized water tests. The dissociation constant (Kd) values obtained for NH4Cl in deionized water approximately doubled with every 10.C increase in liquid temperature from 15.C to 35.C. A similar trend was obtained for lagoon liquid in the 25.C to 35.C liquid temperature range, but the Kd values for the lagoon liquid were ~50% of those for NH4Cl in deionized water. However, at 15.C, the Kd value for the lagoon liquid was almost the same as for deionized water, and was 0.75 the lagoon liquid value at 25.C. Based on these results, it can be concluded that the Kd values of ammonium ion in anaerobic lagoon liquid was 50% of the value in deionized water at 25.C and 35.C, and 94% of the value at 15.C. This implies that for lagoons with characteristics similar to those of the anaerobic lagoon liquid reported in this study, the Kd values (normally derived from NH4 + dissociation in deionized water) used in ammonia volatilization calculations should be adjusted to a fraction of that in deionized water. More studies to determine the Kd values for lagoon liquids with different total ammonia nitrogen concentrations and solid contents are needed. Studies should include the effects of temperature and perhaps distinguish between the effects of dissolved and suspended solids on the dissociation constant.

ON-FARM PERFORMANCE OF TWO SOLIDS/LIQUID SEPARATION SYSTEMS FOR FLUSHED SWINE MANURE

Two different solids/liquid separation systems were evaluated for performance for six months on different farms with about 3500 finishing pigs each where barns were flushed two to four times a day with recycled anaerobic lagoon liquid. The two systems consisted of: (1) a screw-press separator followed by tangential flow separation (TFS) tanks, and (2) a screen and screw-press separator followed by TFS tanks. Sludge from the TFS units was recycled to input to the screw-press or the screw-press feed tank. As a percentage of input to the systems, the recoveries in separated solids were about 10% for total solids(TS), about 10% to 20% for suspended solids (SS), and about 1% to 4% for total Kjeldahl nitrogen (TKN) and total phosphorus (TP). Mass of moist solids (approximately 70% moisture content) removed per unit of flow was variable and averaged about 3 to 4 kg/m3 (25 to 33 lb/1000 gal). Moist separated solids averaged about 0.5% TKN and 0.1% to 0.2% TP. Concentrations reductions based on single grab samples taken every 2 to 3 weeks reflected performance of the various separation components, but did not agree well with the mass recoveries. The concentrations reductions through the TFS systems were similar for the two sites and showed 40% to 60% reduction for SS, TP, and several other parameters.

PERFORMANCE OF A POND AERATION SYSTEM FOR TREATING ANAEROBIC SWINE LAGOON EFFLUENT

The waste treatment system presented in this article is one of the alternative waste management systems that have been evaluated for swine farms in North Carolina. The treatment system was designed and installed on a commercial hog farm by International Ecological Systems and Services (IESS), Inc. The objectives of the treatment system were to reduce odor and ammonia emissions and nitrogen to be land applied. The treatment system consisted of an aeration pond with bacterial augmentation and was designed to treat 190 m3/d (50,000 gal/d) of swine anaerobic lagoon effluent. System performance was evaluated continuously over a 27-month period (Nov. 2000 to Jan. 2003). Nitrification, based on increased nitrite and nitrate concentrations in the aeration pond, varied with temperature. Dissolved oxygen (D.O.) concentrations during the last 18 months of monitoring were usually 2 to 3 mg/L. Low D.O. sometimes occurred because of increased loading or loss of aeration due to broken belts on the blower or severed aeration lines. Based on the inflow and outflow concentrations of the aeration pond, total Kjeldahl nitrogen (TKN) and total ammoniacal nitrogen (TAN) reductions during the last 18 months of monitoring were 93% and 95%, respectively. The nitrate + nitrite nitrogen concentrations and the nitrite concentrations increased from near zero in inflow to the aeration pond to averages of 224 and 25 mg/L, respectively, in outflow during the last 18 months of monitoring. The treatment system experienced some operational and maintenance problems during the evaluation period, mainly with the bacteria delivery system, the blower, the flush tank plunger valves, and flushing controls. Effluent from the aeration pond had low odor intensity, usually low total ammonia nitrogen, variable amount of nitrate/nitrite nitrogen, and lower concentrations of phosphorus, copper, and zinc compared to the anaerobic lagoon effluent.

Evaluation of Ekokan Biofiltration Treatment System on a Swine Farm

Ekokan biofiltration treatment system is one of several systems chosen for demonstration and evaluation as a candidate for “Environmentally Superior Technology” determination under an agreement with Smithfield Foods, Inc and the North Carolina Attorney General. The Ekokan system was constructed to treat manure from about 4000 finishing pigs housed in five barns with pit-recharge system. A pit “release” occurrs about every 4 hours resulting in about 681m3 (180,000 gal.) wastewater per day. After a solids/liquid separation (conveyor/screen separator), the waste water is pumped to an equalization tank, and then gravity flows through two sets of two-stage upflow aerated biofilters that have fixed media. Biofilters are periodically cleaned or flushed to remove excess organic material. Part of the treated effluent is recycled to dilute influent, and the rest is stored in a partitioned section of the pre-existing anaerobic lagoon. Liquid from this section is pumped to the barns to recharge the pits. Information on the demonstration/evaluation procedure is presented, as well as system design, startup of the system, and data for flows and performance of the system for January through March 2003.