AIR QUALITY RESEARCH AND TECHNOLOGY TRANSFER WHITE PAPER AND RECOMMENDATIONS FOR CONCENTRATED ANIMAL FEEDING OPERATIONS

 

 

 

 

 

 

by

 

Confined Livestock Air Quality Committee of the

USDA Agricultural Air Quality Task Force

 

John M. Sweeten (Chair), Texas A&M University

Larry Erickson, Kansas State University

Phyllis Woodford, Colorado Department of Public Health & Environment

Calvin B. Parnell, Texas A&M University

Kendall Thu, Northern Illinois University

Tommy Coleman, AAMU - Plant, Soil, and Animal Sciences

Robert Flocchini, University of California - Davis

Clinton Reeder, Pendleton, OR

Jerold R. Master, Arkansas Pork Producers Association

William Hambleton, Fresno, CA

George Bluhm, USDA-NRCS

Dennis Tristao, J. G. Boswell Company

 

 

 

Adopted by

 

USDA Agricultural Air Quality Task Force

Washington D.C.

 

 

July 19, 2000

 

 

 

Acknowledgements

The following persons also contributed written material or valuable editorial suggestions:

·        Dr. Allen Sutton, Purdue University

·        Dr. Brent W. Auvermann, Texas A&M University

·        Dr. Lowell Ashbaugh, University of California - Davis

 

 

Table of Contents

 

EXECUTIVE SUMMARY

 

Introduction

 

Air Quality Parameters and Concerns

      1.   Odors and Odorants

      2.   Major Gases of Concern - Ammonia and Hydrogen Sulfide

      3.   Particulate Matter -- PM₁₀ and PM_2.5

      4.   Co-Product Gases – CO₂, CH₄, etc

 

Emission Factors: A Case for Accuracy

      1.   Significance of Emission Factors

      2.   Emission Factors for Cattle Feedyards and Dairies

      3.   Errors in the AP-42 Cattle Feedyard Emission Factor

      4.   Comparison of Emission Factors Using a Line Source (TAMU Process)

            and ISC Dispersion Modeling

      5.   PM Concentrations

      6.   Recommendations for Correcting Emission Factors

 

Human response and health effects

      1.   Confined Animals

      2.   Employee Concerns

      3.   Affected Public

 

Current Policy – Characterization and Assessment

      1.   Overview

      2.   Federal Policies

      3.   Recent State Policy Developments

 

Current Technologies to Address Odor Problems

      1.   Approaches: An Overview

      2.   Diet Effects on Odors

      3.   Manure Treatment for Odor Control

      4.   Capture and Treatment of Odorous Gases

      5.   Enhanced Dispersion of Odor

      6.   Summary of Odor Control Opportunities

 

Candidate Dust (PM) Control Practices

 

Current Research Programs to Address Problems

      1.   General Characterization of Prior Research

      2.   Health Issues/Risks

      3.   Current Research Levels

 

Research Needs Assessment

      1.   PM Emission Factors

      2.   Odors and Odorants

      3.   Dispersion

      4.   Indoor Air Quality, CAFO Buildings

      5.   Health Effects

 

Technology Transfer Program Needs

      1.   Producers and Private Industry

      2.   General Public and Affected Neighbors

      3.   Public Programs

      4.   Technical/Engineering Assistance

 

Discussion of Recommended Program Needs

      1.   Prioritized Topics

      2.   Partnerships

      3.   Budgetary Requirements & Recommendations

      4.   Implementation - Initiatives, Agency Actions, etc

 

SUMMARY

 

REFERENCES

 

TABLES

 

APPENDICES

 

 

 

 

AIR QUALITY RESEARCH AND TECHNOLOGY TRANSFER WHITE PAPER AND RECOMMENDATIONS FOR CONCENTRATED ANIMAL FEEDING OPERATIONS

 

Report Prepared by:

Confined Livestock Air Quality Subcommittee

USDA Agricultural Air Quality Task Force (AAQTF)

 

EXECUTIVE SUMMARY

 

U.S. farmers are leaders in producing the safest and most economical food supply in the world.  Each year, U.S. consumers spend less than 11% of their income on food.  Concentrated animal feeding operations (CAFOs) have largely contributed to the ability of U.S. producers to meet growing demands for the production of meat, milk, poultry and eggs.  To maintain a safe and economical food supply, producers must have sufficient lead-time, cost-effective technologies, and resources to adjust to changing public agendas that include air quality protection.  To continue this predominance in agricultural production, the USDA Agricultural Air Quality Task Force (AAQTF) established by Congress in the 1996 Farm Bill, recommends an additional $65 million be annually appropriated for agricultural air quality issues.  Of this amount, $12.8 million should be specifically targeted for CAFO research needs.

 

The following information summarizes the findings of the AAQTF in regard to air quality issues associated with CAFOs.  A full discussion of the issues can be found in the “Air Quality Research & Technology Transfer White Paper and Recommendations for Concentrated Animal Feeding Operations”.

 

CAFO Air Quality Parameters

• CAFOs can affect air quality through emissions of odor, odorous gases (odorants), particulates (including biological particulate matter), volatile organic compounds and/or some of the so-called greenhouse gases.

 

• Odor from CAFO sources, as experienced by humans, is the composite of as many as 170 or more specific gases, present in trace concentrations either above or below their olfactory thresholds. 

 

• The primary odorous gases of concern include ammonia and hydrogen sulfide.  However, the importance of ammonia and hydrogen sulfide to downwind composite odor as perceived by neighbors is questionable.

 

• Field and laboratory research has largely focused on measuring concentrations of odor.  Data on emission rates, flux rates and emission factors are needed to develop science-based policies for the reduction of CAFO odor and odorants.

 

• Future research should be directed toward odorous gases that more closely correlate with odor as perceived by humans.

 

• Carbon dioxide, methane and non-methane reactive organic gases are natural products of manure decomposition.  Strategies to reduce emissions of odor and odorants are likely to reduce emissions of these co-product gases.

 

Emission Factors

• Improved processes for updating emission factors for an array of CAFO-related air contaminants, such as PM₁₀, PM_2.5, volatile organic compounds and ammonia should be initiated.

 

Human Response and Health Effects

• Concerns with health effects of odor, odorants, biological and other particulate matter from CAFOs include livestock, employees and neighbors.  Recent evidence suggests greater secondary health effects on frequently exposed neighbors than previously documented.

 

Current Federal and State Policies

• Water quality concerns were first addressed in the Federal Water Pollution Control Act of 1972, which listed CAFOs as point sources.  A patchwork of tailored policies and regulations has attempted to address voids of groundwater protection and nutrient management, and only in a few cases have air quality concerns been addressed.

 

Integrated Programs

• Integrated programs to address air quality from CAFOs have not been funded or developed.  A collaboration of agencies is needed to work with issues associated with CAFOs and air quality, just as similar collaborative activities have succeeded in regard to water quality.

 

Odor Control Technologies

• There are four basic approaches to control odor and odorants: ration/diet manipulation, manure treatment, capture and treatment of emitted gases and enhanced dispersion.  Each approach has multiple technologies that need to be tailored on a site-specific basis.

 

Dust Control Technologies

• Technologies for particulate (dust) control from open-lot feeding systems, where needed, include frequent manure removal, stocking density adjustment to take advantage of excreted manure moisture and water sprinkling.

 

Research Funding

• A program of accelerated research, education, technical training, technology transfer and financial assistance to address CAFO air quality problems is strongly recommended. 

 

Of the USDA-ARS FY96-99 animal waste research budget of $5.65 million per year and $6.9 million in the CSREES FY97 budget, the amounts devoted to air quality were so small as not to be separately reported.

 

USDA and EPA funding levels have not been adequate to address or solve air quality problems associated with CAFOs.  The USDA AAQTF recommends at least $12.8 million per year for coordinated, integrated programs for animal agriculture, as part of the additional $65 million in total funding requested for agricultural air quality.

 

Research and Technology Transfer Needs

 

Numerous research and/or technology transfer needs and opportunities were mentioned in the text of this report. In brief, these include:

 

·        Develop accurate and broadly applicable emission rates, flux rates and emission factors for particulate matter, odor and specific odorants applicable to CAFOs;

·        Define emission rates as a function of diurnal, seasonal, and climatic variations, as well as design and management practices;

·        Develop effective, practical and economically feasible odor control technologies for confined animals, treatment, and land application systems;

·        Determine relationships among odor, odorants, particulates and airborne microbial species;

·        Identify kinetic release mechanisms for odorants and odor from principal manure sources and target the development of control technologies accordingly;

·        Develop practical ways, capable of widespread adoption, of reducing ammonia from CAFOs;

·        Transfer economically viable technologies for odor control to all producers regardless if they are a CAFO or animal feeding operation (AFO);

·        Develop innovative air treatment processes for confinement building exhausts or covered lagoon surfaces;

·        Develop odor reduction treatments for use prior to land application;

·        Develop accurate standardized measurement technologies for odor, odorants of principal concern, and fine particulate, and ensure these systems become widely available for research and demonstration; this should include electronic measurement devices that are well-correlated with the human odor experience;

·        Develop accurate dispersion models for odor, odorants, and PM appropriate to specific types of CAFOs, addressing the inherent problems of Gaussian models;

·        Characterize air quality as a function of distance from CAFOs;

·        Implement cooperative industry/agency/university programs for scientific evaluation of new products for producers’ consideration and adoption;

·        Assess the importance of indoor air quality at CAFOs and devise ways to reduce exposure levels;

·        Devise suitable acceptability criteria for community-level exposure to odor and specific associated gases;

·        Assess potential relationships between emission constituents, concentrations, and potential health indicators, and devise appropriate mitigation strategies accordingly;

·        Establish partnerships with health research organizations to identify potential health concerns associated with CAFOs.

 

 

 

AIR QUALITY RESEARCH AND TECHNOLOGY TRANSFER WHITE PAPER AND RECOMMENDATIONS FOR CONCENTRATED ANIMAL FEEDING OPERATIONS

 

Report Prepared by:

Confined Livestock Air Quality Subcommittee

USDA Agricultural Air Quality Task Force (AAQTF)

 

Introduction

 

Animal agriculture in the U.S. is important to the nation’s economic well being, producing almost $100 billion per year in farm revenue contributing to the vitality of rural communities and insuring the sustainability of America’s food supply (GAO, 1999).  The U.S. has developed a very efficient, sophisticated system for production of meat, milk, poultry, and egg products involving concentrated animal feeding operations (CAFOs).  For instance, the United States has 99.0 ± 0.9 million cattle and calves (average ± standard deviation for 1998-2000), and in 1999, a monthly average of 10.32 ± 0.75 million head were in beef cattle feedlots being finished for slaughter (TCFA, 2000).  These finishing cattle generally range in liveweight from 272 kg (600 lbs) to 544 kg (1,200 lbs) per head, with an average liveweight of approximately 408 kg/hd (900 lbs/hd).  During a normal 150 day finishing period, each animal excretes about 900 kg (2,000 lbs) of collectible manure, or about 1,800 kg/hd (4,000 lbs/hd) of manure per head of feedlot capacity per year.  Cattle feedlots in the U.S. produce an estimated 18 million metric tons/yr (20 million tons/yr) of collectable manure containing at least 360,000 metric tons/yr (400,000 tons/yr) of total nitrogen and 135,000 metric tons/yr (150,000 tons/yr) of total phosphorus (P).

 

State and federal regulations have directly addressed water quality protection from CAFOs since the early 1970s.  Accordingly, in the last 30 years systems designed for manure and wastewater management have historically been optimized for water quality protection to comply with EPA effluent limitations guidelines (ELGs) adopted in 1974 and 1976, and currently being updated.  Most states have surpassed USEPA in requiring groundwater protection measures, nutrient balances for land application of manure and wastewater.  Air quality protection has received secondary consideration.  Changing regulatory priorities now have begun to include phosphorus and pathogens in water quality goals and particulate matter, odor, and/or specific odorants in air quality as goals.  For example, ammonia volatilization was considered a desirable means to balance N for land application, and only recently has ammonia loss been viewed as a potential problem in terms of air quality considerations.

 

Water and air quality issues are interrelated.  There has been a major lack of adequate research to deal with both water and air quality issues in a holistic systems approach while maintaining high standards of confined livestock productivity, animal health, and production cost efficiency.  For example, EPA’s anticipated update of Effluent Limitation Guidelines will likely embrace phosphorus (P) limits in land application criteria, and lead toward reduced manure and wastewater application rates in some watersheds.  In turn, this may increase producers’ incentives to reduce N loss and retain N to more nearly balance nitrogen application rates.  Increased funding is needed for research and development that will properly quantify particulate matter (PM) and gaseous emission rates as a function of system design and operational parameters.  Public interest in these issues will need to be tempered by realizations of needed

lead time, resources, and appropriate technologies for producers to meet a changing public agenda and avoid major dislocations in animal agriculture, which is an area of very significant U.S. leadership in the world.

 

AIR QUALITY PARAMETERS AND CONCERNS

 

Concentrated animal feeding operations (CAFOs), including swine and poultry operations, dairies and cattle feedlots and the associated animal waste management systems may produce emissions of odor, odorants, odorous gases, such as ammonia, H₂S, VOCs, “greenhouse” gases (CO₂ and CH₄), and PM.  Regardless of type of contaminant, the emissions load on the atmosphere in terms of mass per unit time is the product of contaminant concentration and the air flow rate (e.g., load = concentration x ventilation rate).

 

1.   Odor and Odorants

Principal sources of odor emissions may include:

      -  Production Facilities -- open lot and confinement buildings;

      -  Manure/wastewater storage and/or treatment systems-- ponds, pits, lagoons, stockpiles, composting operations;

      -  Land application systems for solid or liquid manure, treated effluent, or open lot runoff; and

      -  Animal mortalities/carcasses.

 

Odor may become an annoyance to, and affect the well being of, nearby residents.  Odorous gases (odorants) arise from feed materials, fresh manure, and stored, decomposing or treated manure, and wastewater.  Eaton (1996) listed 170 different compounds present in swine manure odor.  Odorous gases emitted from animal waste include ammonia and amines (Hutchinson et al., 1982; Peters and Blackwood, 1977), sulfides, volatile fatty acids, alcohols, aldehydes, mercaptans, esters, and carbonyls (National Research Council, 1979; Miner, 1975b; Barth et al., 1984; ASAE, 1999a).  Peters and Blackwood (1977) listed 31 odorants identified at cattle feedlots, together with their threshold limit value (TLV) in ppm and odor threshold (ppm), where known.  An olfactory threshold value detected by human panelists is the concentration where half the panelists detect and half do not detect an odor.  Consequently, the threshold value may span a range as great as 5 or 6 orders of magnitude for a single compound and range from as low as 7.5 x 10^-8 ppm for skatole to as high as 12,000 ppm for formaldehyde (Eaton, 1996).  For instance, ammonia has reported odor threshold values spanning three orders of magnitudes ranging from 0.0317 ppm to 37.8 ppm (Eaton, 1996).  Concentrations of odorants at downwind locations are very low; however, some may exceed olfactory threshold values and create nuisance conditions (Sweeten, 2000b).  Odorous compounds generally have not been considered toxic at concentrations found downwind of livestock feeding facilities.  Mackie et al. (1998) and Tamminga (1992) cited lowest toxic values (LTV) of frequently cited odorous gases from confinement buildings.  These LTV values were from 5 to 20,000 times higher than cited odor threshold values for these compounds.  However, recent evidence suggests potential for adverse health effect in some instances (Wing and Wolf, 1999).

 

Odor characteristics that contribute to nuisance conditions are as follows:  (a) the intensity, concentration or strength of the odor; (b) the odor frequency or number of times detected during a time period; (c) the duration of the period in which the odor remains detectable; (d) the perceived offensiveness and character or quality of the odor (Jones, 1992).  These factors interrelate in causing nuisance conditions.  Odor frequency and duration are partly dictated by climatic conditions, including wind-direction frequency, atmospheric stability, and moisture conditions.

 

A weak link in developing odor abatement technologies has been an inability to precisely quantify odor strength with sufficient reproducibility and accuracy (Clanton et al., 1999b).  Odor measurement methods have been applied to animal waste management systems (Bulley and Phillips, 1980; Barth, et al., 1984; Watts, 1991; Sweeten, 1995; McFarland and Sweeten, 1995).  General approaches to estimate the strength or intensity of livestock manure odors include:

      a.   Sensory methods that involve collecting and presenting odor samples to human panelists (diluted or undiluted) under controlled conditions, e.g., Scentometer, dynamic olfactometers, suprathreshold referencing methods, absorption media, etc.

      b.   Measurement of concentrations of specific odorous gases (directly or indirectly).

      c.   Electronic “nose” devices that register presence, concentration or activity of selected odorous gases.

 

Olfactometry is the most widely used method to evaluate odor concentration.  Perhaps the simplest method of field sensory odor concentration measurement is the Barnebey-Sutcliffe Scentometer (Barnebey-Cheney, 1987).  This simple, portable field instrument involves direct sampling of the ambient air, and it has been used as the basis for setting property line odor concentration standards by several states (e.g., Colorado, Montana, North Dakota) and cities.  The Scentometer has also been used for field odor measurement at numerous livestock and poultry operations in the U.S. (Sweeten et al., 1977; Sweeten et al., 1983; Miner and Stroh, 1976; Sweeten et al., 1991) and in data collection contributing to nuisance litigation (Sweeten and Miner, 1993).  The use of suprathreshold referencing (ASTM, 1975) for measuring intensity of livestock waste odor was described by Sweeten et al. (1983 and 1991).  The deployment and improvement of dynamic triangle forced-choice olfactometers (DTFCO) (ASTM 1991; Dravnieks and Prokop, 1975) for livestock odor research is occurring rapidly (Watts, 1991; Jones, 1992; Nicolai et al., 1997; Li et al., 1997) and appears to be the instrumentation of choice for sensory odor measurement for current research.  For instance, Lim et al. (1999) reported odor concentrations, measured by 8 panelists with a dynamic triangle forced-choice olfactometer, for swine nursery buildings with underfloor liquid manure storage pits, as 190 odor units (OU)/m³ in the exhaust air and 18 OU/m³ outside the building.  The data were used to calculate an odor emission rate per head (51 OU/hd/sec) or per unit area (2.1 OU/m²/sec) using airflow rate data.  Regression relationships were found between odor concentration, odor intensity, and odor offensiveness.  Similar data using a DTFCO system was reported by Heber et al. (1998) for four 1,000 head finishing buildings, which produced an average odor concentration of 294 ± 65 OU (range of 12-1,586 OU), and an emission rate of 96 ± 30 OU/hd/sec, or 5.0 OU/m²/sec.

 

Pain et al. (1988) used a small wind tunnel (2 m x 0.5 m x 0.45 m) to collect samples of odorous air and to measure ammonia emissions following the surface spreading of liquid dairy cattle manure (1 to 2 day storage time), before and after mechanical separation with a roller press, onto grassland in the United Kingdom.  Odor samples were collected beneath the flexible plastic sheet canopy into 50 L Tedlar bags inflated within 4 to 5 minutes time.  Odor concentration was measured by 4 to 8 panelists using dynamic olfactometry with 4 to 6 dilutions of each sample presented for determination of the odor threshold (ED₅₀) value.  The odor emission rate was calculated as the product of odor units (OU) and the volumetric airflow rate (odor units/m²/hr).  The odor emission rates measured by Pain et al. (1988) for liquid dairy manure spread on pastures were reported by Smith and Watts (1994) at 22 OUm/s and 11 OUm/s at time intervals of 3 and 48 hours, respectively, after spreading.  In essence, the odor emission rate was reduced by 50% two days after spreading liquid manure.  Similar values were obtained for swine manure slurry.  Total odor emissions were similar for whole dairy cattle manure slurry and separated slurry (Pain et al., 1988). 

 

Despite standardization and control procedures to reduce bias, elements of subjectivity and sources of imprecision remain in odor measurement with sensory panels.  Combined with the high cost per sample of large odor panels, this creates the need for reproducible, inexpensive instruments that mimic the human olfactory response (Lacey, 1998).

 

Clanton et al. (1999b) evaluated several possible sources of variation in determining dilution to threshold odor units using a dynamic triangle forced choice olfactometer.  For the same samples, two different 8-person odor panels consistently produced 22 to 50% differences odor concentration (measured in odor units), depending on odor strength.  Two different olfactometer airflow rates resulted in 9 to 28% differences in odor units.  There were large differences in individual panelist sensitivity to odor detection and likewise variations by individual panelists across different testing days and within a testing session.  A learning curve for individual odor panelists was demonstrated.  To improve the probability of detecting significant reductions in odor resulting from a particular treatment, Clanton et al. (1999b) recommended that several identical pairs of air samples will be needed, together with a sufficient number of panelists to achieve statistically significant differences with current olfactometry technologies.

 

Considerable effort has been devoted to identification and measurement of specific gases within the atmosphere of livestock and poultry confinement buildings (Burnett, 1969; Elliot et al., 1978; Hammond and Smith, 1981).  A large number of odorous compounds are present in very low concentrations.  Miner (1974) reported that the measured concentration of each gaseous compound identified in animal waste odor was below the reported minimum olfactory threshold.  Zahn et al. (1997) reported that volatile organic acids with carbon numbers from 2 to 9 demonstrated the greatest potential for accounting for manure odor.

 

Instruments available to identify and measure the concentrations of specific odorous gases (odorants) emitted from animal manures include gas chromatography and mass spectrometry (GC/MS) (White et al., 1971; Hammond et al., 1974).  These methods are very sensitive in detecting compounds in very low concentrations.  Peters and Blackwood (1977) reported difficulty in positively identifying compounds present in feedlot air samples using GC-FID (gas chromatography-flame ionization detector) technology.  Low peak values precluded the use of GC/MS for amines.  As a result of the low concentrations of many odorants in and around CAFOs, the compounds may need to be concentrated further prior to analysis by use of methods such as solvent desorption, thermal adsorption (Wright, 1994: Zahn et al., 1997) or solid-phase microextraction (SPME) (Zhang et al., 1994).

 

An electronic nose is an array of gas sensors that are combined with pattern recognition software to mimic human olfactory response (Lacey, 1998).  Current commercial applications are focused on high-valued food products.  Lacey (1998) and Mackay-Sim (1992) listed electronic approaches to volatile gas (odor) detection: metal-oxide semi-conductors; field-effect transistors; optical fibers; semi-conducting polymers; and piezo-electronic quartz crystal devices.  These approaches raise the possibility of remote odor monitoring/surveillance networks for individual compounds or odorant mixtures.  The piezo-electric crystals are sensitive to changes in surface mass caused by interaction with gaseous molecules.  As mass is added to the surface, the resonant frequency decreases.  The sensor surface can be designed to respond to single chemicals or groups of chemicals.  Berckmans et al. (1992) in Belgium developed a thick film semiconducting metal oxide sensor for monitoring ammonia concentrations within, and emissions from, livestock confinement buildings.  Some sensors may be affected by water vapor, methane, and temperature (Lacey, 1998).

 

Collection and storage of odorous air samples for presentation to panelists or instrumental analysis is an important consideration (Sweeten, 1995).  Tedlar bags (10-50 L) that are inflated in the field using portable wind tunnel or negatively-pressurized canisters have become the most commonly used method.

 

Schmidt et al. (1999) described wind tunnel design parameters for odor sampling and concluded that odor and hydrogen sulfide concentrations and corresponding emission rate increase with bulk wind speed of the tunnel according to a power function relationship.  Results of Schmidt et al. (1999) corroborated earlier work by Smith and Watts (1994b) on open unsurfaced cattle feedlots.

 

2.   Major Gases of Concern – Ammonia and Hydrogen Sulfide

Ammonia is one of the fixed gases of both aerobic and anaerobic decomposition of organic wastes.  Much of the nitrogen excreted by cattle is in the form of urea, which rapidly hydrolyzes to NH₃.  Additional NH₃ as well as amine are produced during microbial breakdown of fecal material in confinement buildings, on feedlot surfaces, in stockpiles, and in lagoons or runoff retention ponds.  Ammonia evolution rates are a function of time, temperature, pH of the manure surface, and level of biological activity.  Ammonia (NH₃) volatilization is probably the most important pathway for on-site loss of nitrogen in animal manure to air and water resources.  There are four main sources of ammonia emissions on a commercial swine facility: confinement buildings, manure and storage treatment lagoons, land application of lagoon effluent to cropland, and potential NH₃ re-emission from the soil (Aneja et al., 2000a).  In the atmosphere, ammonia can react with acidic species to form ammonium sulfate, ammonium nitrate, ammonium chloride, or particulate (Aneja et al., 2000a).  Battye et al. (1994) reported that ammonia in the atmosphere can have a significant effect on oxidation and deposition rates of acidic compounds.

 

Ammonia concentrations can be measured by packed bed chemical-specific syringe tubes that are primarily used in occupational safety and health applications (Sweeten et al., 1991).  A second approach is GC/MS as mentioned previously in which odorant samples are presented to the GC/MS either by vapor syringe or by solid-phase microextraction.  The third approach is an ammonia (and amine) absorption trap in which a known volume of air is passed through a weak acid media: sulfuric acid solution (Luebs et al., 1974; Hutchinson et al., 1982; Cole and Parker, 1999); boric acid solution (Moore et al., 1995; O’Halloran, 1993); sulfuric acid-impregnated fiberglass (Peters and Blackwood, 1977).  The ammonia-absorption technique allows for comparisons of ammonia concentrations and emission rates between various times and locations (White et al., 1974).  A fourth approach (Oosthoek and Kroodsma 1990; and Phillips et al., 1995), involves chemoluminescence, in which ammonia and NO₂ are converted to NO at 750°C.  In a split airstream at 350°C, the NO₂ is converted to NO.  Ammonia concentration is calculated as the difference in NO concentration between the 350° and 750°C airstream. Prior U.S. research has indicated that ammonia is emitted from surfaces of open, unpaved cattle feedlots and dairy corrals at concentrations of 360-980 mg/m³ as compared to background levels of 1-4 mg/m³ (Sweeten et al., 1999).  Ammonia volatilization losses are reportedly 50% or more of total N excreted from open lot surfaces and 23-70% following field spreading of manure. 

 

Luebs et al. (1974) measured ammonia concentrations at 1.2 m height upwind and downwind of open-lot dairy operations near Chino, California, in which 145,000 dairy cows were concentrated in several farms within a 60 square mile area near Los Angeles.  Concentrations of ammonia (distillable nitrogen) were below the odor threshold concentrations reported for ammonia.  An ammonia concentration of 540 Fg/m³ was measured at the downwind corral fence of a 600-cow dairy.  This concentration was reduced to 18 Fg/m³ at a downwind distance of 0.5 miles (0.8 km).  By comparison, ammonia concentrations were 92 ± 89 Fg/m³ at Chino airport near the center of the dairy area and 4 ± 2 Fg/m³ at a non-agricultural reference site. Diurnal fluctuations were observed in ammonia concentration at the Chino airport with highest concentrations between 1800 and 2200 hours (184 Fg/m³) and 0600 to 1000 hours (128 Fg/m³).  Much lower ammonia concentrations occurred in afternoons 1400 to 1800 hours (6 Fg/m³).  Fenceline observations at an individual dairy did not coincide with the diurnal pattern at the center of the dairy area.

 

Ammonia volatilized from liquid dairy manure slurry spread on pastures was measured (Pain et al., 1988) by drawing air samples from the tunnel inflow and outflow sections through absorption flasks containing orthophosphoric acid (0.005 M).  Ammonia losses following application were 23 to 70 percent within 10 to 14 days after application, although 80 percent of these losses occurred within 2 days of application.  There was a strong correlation (r² = 0.94) between odor emissions and ammonia emissions following application of dairy cattle slurry to the grassland pasture.  A similar relationship was obtained for swine manure slurry.  A greater proportion of ammonia was lost from dairy cattle slurry than from swine slurry.

 

Montes and Chastain (2000) evaluated ammonia losses from sprinkler irrigation of swine lagoon effluent at two tree plantations (2 and 8 years old) in South Carolina.  As compared to prior research of others (1980-1997) which reported 10-60% ammonia-nitrogen loss through sprinkler irrigation, they observed erratic losses ranging from (-) 40% to (+) 38%, with a mean value of 2% ± 16%.

 

Keck (1997) determined the influences of manure removal frequency, climatic conditions, and exposed surface area on ammonia emissions from cattle exercise yards and from wind tunnel simulations of 7 m² manured surfaces where airflow volume could be determined. Ammonia concentration was determined using HCl absorption.  Urine caused more than 8 times greater ammonia emission per unit area than feces (205 mg/m²h vs. 25 mg/m²/h). Daily removal of manure (feces and urine) produced a small decrease in ammonia emission compared to removal at three-day intervals. Ammonia emissions were greater in warm season than in cold weather. Reducing the surface area of manure decreased the ammonia emission. 

 

Schmidt et al. (1997) conducted field measurements at 5 dairies in Southern California during winter and summer seasons to determine surface emission rates of ammonia and other compounds implicated in contributing to PM 10 emissions.  Sampling was conducted using a surface isolation flux chamber (EPA, 1986). Of the compounds studied, ammonia had the highest flux rate.  Manure stockpiles that were disturbed produced the highest ammonia flux rate. Amine compounds were not detected above the detection threshold. The average ammonia emissions for 4 dairies was 11.2 ± 4.3 kg/cow/year projected from the late summer/early fall testing period, and was 4.8 ± 1.1 kg/cow/yr projected from the winter testing period.

 

Oosthoek and Kroodsma (1990) reported monthly ammonia concentrations of 3.0-4.8 mg/m³ from a 40-cow dairy free-stall housing unit.  Monthly ammonia emission rates ranged from 39 to 60 kg/month, or 1 to 1.5 kg/head/month, where cattle were housed at night.  A scraped concrete floor had three times the ammonia emission rate of a flushed concrete floor (600 mg/m²/hr vs. 200 mg/m²/hr).

 

Peters and Blackwood (1977) measured both ammonia and hydrogen sulfide concentrations at two cattle feedyards on the Texas High Plains.  These one-time measurements were:

      a.   Ammonia -- 104-120 mg/m³

      b.   Total Sulfide -- 5-27.5 mg/m³

There was no correlation between the NH₃ and H₂S concentrations.

 

Battye et al. (1994) examined the European literature to arrive at what they termed “rough estimates” of ammonia emission factors for agricultural and nonagricultural sources in the U.S.  The NH₃ emission factors recommended for use in future U.S. emissions inventories were based primarily on European factors for animal agriculture and fertilizer application.  The relative contribution of animal agriculture to the total U.S. ammonia emission inventory was extrapolated to be as follows: all cattle and calves (43.4%