P. W. Westerman

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.

Water treatment and waste characterization evaluation of an intensive recirculating fish production system

A combination of two different technologies used for fish production was evaluated at the North Carolina State University (NCSU) Fish Barn facility. The combined system included the ECOFISH∗ tank, developed at the Norwegian Hydrotechnical Laboratory (NHL) at SINTEF (Trondheim, Norway) and water treatment and recycle technology designed at NCSU. Approximately 2170 fingerling tilapia (Oreochromis niloticus, Oreochromis niloticus × Oreochromis aureus) were grown from 3.6 to 507 g in 177 days in a 20 m3 four-zone tank. The system design included patented particle traps at the bottom of each zone to remove feed waste and excrement, sludge collectors where the removed particles settled, a rotating screen filter for suspended solids removal, a high-rate linear-path trickling biological filter for nitrification, and two down-flow columns for oxygen injection. The measured suspended solids level in the tank zones were usually less than 7.5 mg l −1. Based on six efficiency tests with a mean total ammonia nitrogen (TAN) concentration in the culture tank of 0.62 mg l −1, the biofilter removed approximately 65% on a single pass through the filter, with an average removal rate per unit of filter surface area of 0.33 g TAN m −2 day −1. Sampling every 4 h over a 24-h period showed variability in concentrations and TAN removal rates by the biofilter. Six efficiency tests on the sludge collectors and the screen filter showed 80% and 41% suspended solids removal efficiency, respectively, based on the influent and effluent concentrations. On a daily basis, the sludge collectors and the screen filter each removed about 18% of feed volatile solids input, respectively, based on three 24-h periods studied. Fresh water use averaged approximately 1500 l day −1, which was about 7% of the system volume.

Upflow biological aerated filters for the treatment of flushed swine manure

Abstract A pilot plant with capacity to treat up to 8 m 3 /day of supernate from settled flushed swine wastes was monitored for 12 months. The main system is composed of two upflow aerated biofilters connected in series. The aerated biofilters, operated under warm weather conditions (average temperature of 27°C), were able to remove about 88% of biochemical oxygen demand (BOD), 75% of chemical oxygen demand (COD), and 82% of total suspended solids (SS) with loading of 5.7 kg COD/m 3 /day of biofilter media. The total Kjeldahl nitrogen (TKN), total ammonia nitrogen (NH 3 -N), and total nitrogen (Total-N) reductions averaged 84%, 94% and 61%, respectively, during warm weather, with a significant portion of the NH 3 -N being converted to nitrite plus nitrate nitrogen (NO 2 +NO 3 -N). At higher organic loading (over 9 kg COD/m 3 /day) during September, the biofilters had only slightly lower percentage removal rates. Operation at lower temperatures (average of 10°C) resulted in lower performances. The COD, TKN, NH 3 -N, and Total-N removal averaged 56%, 49%, 52%, and 29%, respectively, in December through March. The COD mass removal rate was linear with loading rate over the range of approximately 2–12 kg COD/m 3 /day of filter. A mass balance average for the 12 months indicated that about 30% of the influent volume, 35% of Total-N and 60% of total phosphorus (Total-P) are removed with the biofilter backwash. Management and utilization of the backwash are important factors in implementing this type of system on farms. The unaccounted-for nitrogen was about 24% and could have been lost as ammonia volatilization or possibly through denitrification within the biofilm.

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).

AERATION OF LIVESTOCK MANURE SLURRY AND LAGOON LIQUID FOR ODOR CONTROL: A REVIEW

Odors can be generated on livestock production farms from three major sources: production facilities, waste treatment system and land application. Aerobic treatment of animal manure slurry and lagoon liquid can be an effective treatment for odor control. The energy costs required for aeration, however, is a major factor that has prevented aerobic treatment from being used widely for livestock manure treatment. There are many different aeration devices and several possible aeration schemes and processes which can be used on livestock farms. Recent research has been focused on developing more efficient aeration techniques and equipment, determining the minimum aeration requirements for odor control, and developing optimum intermittent aeration schemes to obtain efficient manure decomposition and to effect nitrogen transformation and removal from the manure slurry or liquid. This article reviews the basic concepts of aerobic treatment and presents general recommendations for designing and operating various aeration systems for treating animal manure slurry and lagoon liquid.

Performance of a low temperature lagoon digester

Abstract An earthen digester was constructed to treat the separated liquids from flushed dairy cattle manure. A floating cover was used to harvest the biogas produced. Satisfactory digester performance was found for both winter and summer conditions. However, biogas production was found to fluctuate seasonally with reduced biogas production being noted during the winter. Mean methane (CH4) yield was found to be 0·39 m3 CH4/kg volatile solids (VS) added. Mean biogas concentrations was 68·9% CH4 and 28·3% carbon dioxide (CO2). The loading rate during the period of study (31 October 1988–25 March 1991) was 0·12 kg VS/m3 -day.

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.

Low-temperature digestion of dairy and swine manure

Abstract Laboratory anaerobic digesters were fed dairy and swine manure at the rates of 0.1 and 0.2 kg volatile solids (VS)/ m 3 -day over the temperature range of 10–23°C. The digesters were operated successfully with little indication of instability. Methane (CH 4 ) yield, (B, m 3 CH 4 /kg VS added) was determined to typically decrease linearly as temperature (T, °C) was decreased: Dairy at 0.1 kg VS/m 3 -day B=0.1153+0.0053T Dairy at 0.2 kg VS/m 3 -day B=0.0820+0.0063T Swine at 0.1 kg VS/m 3 -day B=0.2011+0.0053T Swine at 0.2 kg VS/m 3 -day B=0.3177+0.0044T Some increased performance was suggested for the lower loading rates compared with higher loading rates.

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.

NUTRIENT CONTENT AND SLUDGE VOLUMES IN SINGLE-CELL RECYCLE ANAEROBIC SWINE LAGOONS IN NORTH CAROLINA

Fifteen single-stage anaerobic lagoons representing four types of swine production farms (farrow-to-feeder, crossing, farrow-to-finish, and finish) were monitored during two years to evaluate performance. Lagoon liquid and sludge were characterized for all sites. Lagoon loading rates, percent of lagoon volume occupied by sludge, sludge accumulation and age of lagoon at the time of evaluation were determined. The mean annual lagoon liquid Total Kjeldahl Nitrogen (TKN) increased with increase in average daily live animal weight per cubic meter (LAW/m3) of lagoon volume, and the rate of increase depended upon the type of production farm. The monthly supernatant TKN concentration varied as much as 50% over two years for the same lagoon, generally showing a cyclic pattern with highest concentration in mid-summer. Of the nutrient mass contained in the lagoon, about 30% of TKN and more than 90% of Total Phosphorus (Total-P) and volatile solids (VS) were contained in the sludge. The accumulation of TKN and Total-P in the sludge increased linearly with time. Sludge accumulation was found to be impacted both by age of lagoon and loading rate. Based on total sludge accumulated and the age of lagoon, it was determined that sludge accumulated at an approximate rate of 0.003 m3/yr per kg of LAW. This is higher accumulation rate than reported from a study in Missouri, but lower than reported by a study in South Carolina. It is approximately 25% of the value predicted by ASAE Engineering Practice EP 403.2 and ASAE DATA D384.1. Additional data is needed on sludge accumulation rates in swine lagoons and characterization of sludge, especially considering likely changes in swine nutrition to improve nutrient utilization and reduce nitrogen and phosphorus excretion.