Production of Greenhouse Gases, Ammonia, Hydrogen Sulfide, and Odorous Volatile Organic Compounds from Manure of Beef Feedlot Cattle Implanted with Anabolic Steroids

Animal production is part of a larger agricultural nutrient recycling system that includes soil, water, plants, animals and livestock excreta. When inefficient storage or utilization of nutrients occurs, parts of this cycle become overloaded. The U.S. Beef industry has made great strides in improving production efficiency with a significant emphasis on improving feed efficiency. Improved feed efficiency results in fewer excreted nutrients and volatile organic compounds (VOC) that impair environmental quality. Anabolic steroids are used to improve nutrient feed efficiency which increases nitrogen retention and reduces nitrogen excretion. This study was conducted to determine the methane (CH4), carbon dioxide (CO2), nitrous oxide (N2O), odorous VOCs, ammonia (NH3), and hydrogen sulfide (H2S) production from beef cattle manure and urine when aggressive steroid implants strategies were used instead of moderate implant strategies.

What Did We Do?

Two groups of beef steers (60 animals per group) were implanted using two levels of implants (moderate or aggressive). This was replicated three times, twice with spring-born calves and once with fall-born calves, for a total of 360 animals used during the study. Both moderate and aggressive treatment groups received the same initial implant that contain 80 mg trenbolone acetate and 16 mg estradiol. At second implant, steers in the moderate group received an implant that contained 120 mg trenbolone acetate and 24 mg estradiol, while those in the aggressive group received an implant that contained 200 mg trenbolone acetate and 20 mg estradiol. Urine and feces samples were collected individually from 60 animals that received a moderate implant and 60 animals that received an aggressive implant at each of three sampling dates (Spring and Fall 2017 and Spring 2018). Within each treatment, fresh urine and feces from five animals were mixed together to make a composite sample slurry (2:1 ratio of manure:urine) and placed in a petri dish. There were seven composite mixtures for each treatment at each sampling date. Wind tunnels were used to pull air over the petri dishes. Ammonia, carbon dioxide, and nitrous oxide concentrations were measured using an Innova 1412 Photoacoustic Gas Analyzer. Hydrogen sulfide and methane were measured using a Thermo Fisher Scientific 450i and 55i, respectively. Gas measurements were taken a minimum of six times over 24- to 27-day sampling periods.

What Have We Learned?

Flux of ammonia, hydrogen sulfide, methane, nitrous oxide, and total aromatic volatile organic compounds were significantly lower when an aggressive implant strategy was used compared to a moderate implant strategy. However, the flux of total branched-chained volatile organic compounds from the manure increased when aggressive implants were used compared to moderate implants. Overall, this study suggests that air quality may be improved when an aggressive implant is used in beef feedlot animals.

Table 1. Overall average flux of compounds from manure (urine + feces) from beef feedlot cattle implanted with a moderatea or aggressiveb anabolic steroid.
Hydrogen Sulfide Ammonia Methane Carbon Dioxide Nitrous  Oxide Total Sulfidesc Total SCFAd Total BCFAe Total Aromaticsf
µg m-2 min-1 ——–mg m-2 min-1——–
Moderate 4.0±0.1 2489.7±53.0 117.9±4.0 8795±138 8.6±0.1 0.7±0.1 65.2±6.6 5.9±0.5 2.9±0.3
Aggressive 2.7±0.2 2186.4±46.2 104.0±3.8 8055±101 7.4±0.1 0.8±0.1 63.4±5.7 7.6±0.8 2.1±0.2
P-value 0.01 0.04 0.01 0.01 0.01 0.47 0.83 0.05 0.04
aModerate treatment =  120 mg trenbolone acetate and 24 mg estradiol at second implant; bAggressive treatment = 200 mg trenbolone acetate and 20 mg estradiol at second implant; cTotal sulfides = dimethyldisulfide and dimethyltrisulfide; dTotal straight-chained fatty acids (SCFA) = acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, and heptanoic acid;  eTotal branch-chained fatty acids (BCFA) = isobutyric acid and isovaleric acid; fTotal aromatics = phenol, 4-methylphenol, 4-ethylphenol, indole, and skatole

Future Plans
Urine and fecal samples are being evaluated to determine the concentration of steroid residues in the livestock waste and the nutrient content (nitrogen, phosphorus, potassium and sulfur) of the urine and feces.

Authors

mindy.spiehs@ars.usda.gov Mindy J. Spiehs, Research Animal Scientist, USDA ARS Meat Animal Research Center, Clay Center, NE

Bryan L. Woodbury, Agricultural Engineer, USDA ARS Meat Animal Research Center, Clay Center, NE

Kristin E. Hales, Research Animal Scientist, USDA ARS Meat Animal Research Center, Clay Center, NE

Additional Information

Will be included in Proceedings of the 2019 Annual International Meeting of the American Society of Agricultural and Biological Engineers.

USDA is an equal opportunity provider and employer. 

Acknowledgements

The authors wish to thank Alan Kruger, Todd Boman, Bobbi Stromer, Brooke Compton, John Holman, Troy Gramke and the USMARC Cattle Operations Crew for assistance with data collection.

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2019. Title of presentation. Waste to Worth. Minneapolis, MN. April 22-26, 2019. URL of this page. Accessed on: today’s date.

Production of Greenhouse Gases and Odorous Compounds from Manure of Beef Feedlot Cattle Fed Diets With and Without Ionophores

Ionophores are a type of antibiotics that are used in cattle production to shift ruminal fermentation patterns. They do not kill bacteria, but inhibit their ability to function and reproduce. In the cattle rumen, acetate, propionate, and butyrate are the primary volatile fatty acids produced. It is more energetically efficient for the rumen bacteria to produce acetate and use methane as a hydrogen sink rather than propionate. Ionophores inhibit archaea forcing bacteria to produce propionate and butyrate as hydrogen sinks rather than working symbiotically with methanogens to produce methane as a hydrogen sink. Numerous research studies have demonstrated performance advantages when ionophores are fed to beef cattle, but few have considered potential environmental benefits of feeding ionophores. This study was conducted to determine if concentrations of greenhouse gases, odorous volatile organic compounds (VOC), ammonia, and hydrogen sulfide from beef cattle manure could be reduced when an ionophore was fed to finishing cattle.

What Did We Do?

Four pens of feedlot cattle were fed an ionophore (monensin) and four pens received no ionophore (n=30 animals/pen). Samples were collected six times over a two-month period. A minimum of 20 fresh fecal pads were collected from each feedlot pen at each collection. Samples were mixed within pen and a sub-sample was placed in a small wind-tunnel. Duplicate samples for each pen were analyzed. Ammonia, carbon dioxide (CO2), and nitrous oxide (N2O) concentrations were measured using an Innova 1412 Photoacoustic Gas Analyzer. Hydrogen sulfide (H2S) and methane (CH4) were measured using a Thermo Fisher Scientific 450i and 55i, respectively.

What Have We Learned?

 

Table 1. Overall average concentration of compounds from feces of beef feedlot cattle fed diets with and without monensin.
Hydrogen Sulfide Ammonia Methane Carbon Dioxide Nitrous  Oxide Total Sulfidesa Total  SCFAb Total BCFAc Total Aromaticsd
µg L-1 —————-mg L-1—————-
No Monensin 87.3±2.2 1.0±0.2 4.3±0.1 562.5±2.2 0.4±0.0 233.4±18.3 421.6±81.9 16.8±3.1 83.7±6.4
Monensin 73.9±1.4 1.1±0.2 3.2±0.2 567.1±2.1 0.5±0.0 145.5±10.9 388.9±32.5 20.3±2.3 86.4±5.6
P-value 0.30 0.40 0.01 0.65 0.21 0.01 0.79 0.48 0.75
aTotal sulfides = dimethyldisulfide and dimethyltrisulfide; bTotal straight-chained fatty acids (SCFA) = acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, and heptanoic acid;  cTotal branch-chained fatty acids (BCFA) = isobutyric acid and isovaleric acid; dTotal aromatics = phenol, 4-methylphenol, 4-ethylphenol, indole, and skatole

Total CH4 concentration decreased when monensin was fed. Of the VOCs measured, only total sulfide concentration was lower for the manure from cattle fed monensin compared to those not fed monensin. Ammonia, N2O, CO2, H2S, and all other odorous VOC were similar between the cattle fed monensin and those not fed monensin. The results only account for concentration of gases emitted from the manure and do not take into account any urinary contributions, but indicate little reduction in odors and greenhouse gases when monensin was fed to beef finishing cattle.

Future Plans

A study is planned for April – July 2019 to measure odor and gas emissions from manure (urine and feces mixture) from cattle fed with and without monensin. Measurements will also be collected from the feedlot surface of pens with cattle fed with and without monensin.  

Authors

Mindy J. Spiehs, Research Animal Scientist, USDA ARS Meat Animal Research Center, Clay Center, NE

mindy.spiehs@ars.usda.gov

Bryan L. Woodbury, Agricultural Engineer, USDA ARS Meat Animal Research Center, Clay Center, NE

Kristin E. Hales, Research Animal Scientist, USDA ARS Meat Animal Research Center, Clay Center, NE

Additional Information

Dr. Hales also looked at growth performance and E. coli shedding when ionophores were fed to finishing beef cattle. This work is published in Journal of Animal Science.

Hales, K.E., Wells, J., Berry, E.D., Kalchayanand, N., Bono, J.L., Kim, M.S. 2017. The effects of monensin in diets fed to finishing beef steers and heifers on growth performance and fecal shedding of Escherichia coli O157:H7. Journal of Animal Science. 95(8):3738-3744. https://pubmed.ncbi.nlm.nih.gov/28805884/.

USDA is an equal opportunity provider and employer.

Acknowledgements

The authors wish to thank Alan Kruger, Todd Boman, and the USMARC Cattle Operations Crew for assistance with data collection.

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2019. Title of presentation. Waste to Worth. Minneapolis, MN. April 22-26, 2019. URL of this page. Accessed on: today’s date.

Evaluation of current products for use in deep pit swine manure storage structures for mitigation of odors and reduction of NH3, H2S, and VOC emissions from stored swine manure

The main purpose of this research project is an evaluation of the current products available in the open marketplace for using in deep pit swine manure structure as to their effectiveness in mitigation of odors and reduction of hydrogen sulfide (H2S), ammonia (NH3), 11 odorous volatile organic compounds (VOCs) and greenhouse gas (CO2, methane and nitrous oxide) emissions from stored swine manure. At the end of each trial, hydrogen sulfide and ammonia concentrations are measured during and immediately after the manure agitation process to simulate pump-out conditions. In addition, pit manure additives are tested for their impact on manure properties including solids content and microbial community.

What Did We Do?

Figure 1. Reactor simulates swine manure storage with controlled air flow rates.

We are using 15 reactors simulating swine manure storage (Figure 1) filled with fresh swine manure (outsourced from 3 different farms) to test simultaneously four manure additive products using manufacturer recommended dose for each product. Each product is tested in 3 identical dosages and storage conditions. The testing period starts on Day 0 (application of product following the recommended dosage by manufacturer) with weekly additions of manure from the same type of farm. The headspace ventilation of manure storage is identical and controlled to match pit manure storage conditions. Gas and odor samples from manure headspace are collected weekly. Hydrogen sulfide and ammonia concentrations are measured in real time with portable meters (both are calibrated with high precision standard gases). Headspace samples for greenhouse gases are collected with a syringe and vials, and analyzed with a gas chromatograph calibrated for CO2, methane and nitrous oxide. Volatile organic compounds are collected with solid-phase microextraction probes and analyzed with a gas chromatography-mass spectrometry (Atmospheric Environment 150 (2017) 313-321). Odor samples are collected in 10 L Tedlar bags and analyzed using the olfactometer with triangular forced-choice method (Chemosphere, 221 (2019) 787-783). To agitate the manure for pump-out simulation, top and bottom ‘Manure Sampling Ports’ (Figure 1) are connected to a liquid pump and cycling for 5 min. Manure samples are collected at the start and end of the trial and are analyzed for nitrogen content and bacterial populations.

The effectiveness of the product efficacy to mitigate emissions is estimated by comparing gas and odor emissions from the treated and untreated manure (control). The mixed linear model is used to analyze the data for statistical significance.

What we have learned?

Figure 2. Hydrogen sulfide and ammonia concentration increased greatly during agitation process conducted at the end of trial to simulate manure pump-out conditions and assess the instantaneous release of gases. The shade area is the initial 5 minutes of continuous manure agitation.

U.S. pork industry will have science-based, objectively tested information on odor and gas mitigation products. The industry does not need to waste precious resources on products with unproven or questionable performance record. This work addresses the question of odor emissions holistically by focusing on what changes that are occurring over time in the odor/odorants being emitted and how does the tested additive alter manure properties including the microbial community. Additionally, we tested the hydrogen sulfide and ammonia emissions during the agitation process simulating pump-out conditions. For both gases, the emissions increased significantly as shown in Figure 2. The Midwest is an ideal location for swine production facilities as the large expanse of crop production requires large fertilizer inputs, which allows manure to be valued as a fertilizer and recycled and used to support crop production.

Future Plans

We develop and test sustainable technologies for mitigation of odor and gaseous emissions from livestock operations. This involves lab-, pilot-, and farm-scale testing. We are pursuing advanced oxidation (UV light, ozone, plant-based peroxidase) and biochar-based technologies.

Authors

Baitong Chen, M.S. student, Iowa State University

Jacek A. Koziel*, Prof., Iowa State University (koziel@iastate.edu)

Daniel S. Andersen, Assoc. Prof., Iowa State University

David B. Parker, Ph.D., P.E., USDA-ARS-Bushland

Additional Information

  • Heber et al., Laboratory Testing of Commercial Manure Additives for Swine Odor Control. 2001.
  • Lemay, S., Stinson, R., Chenard, L., and Barber, M. Comparative Effectiveness of Five Manure Pit Additives. Prairie Swine Centre and the University of Saskatchewan.
  • 2017 update – Air Quality Laboratory & Olfactometry Laboratory Equipment – Koziel’s Lab. doi: 10.13140/RG.2.2.29681.99688.
  • Maurer, D., J.A. Koziel. 2019. On-farm pilot-scale testing of black ultraviolet light and photocatalytic coating for mitigation of odor, odorous VOCs, and greenhouse gases. Chemosphere, 221, 778-784; doi: 10.1016/j.chemosphere.2019.01.086.
  • Maurer, D.L, A. Bragdon, B. Short, H.K. Ahn, J.A. Koziel. 2018. Improving environmental odor measurements: comparison of lab-based standard method and portable odour measurement technology. Archives of Environmental Protection, 44(2), 100-107.  doi: 10.24425/119699.
  • Maurer, D., J.A. Koziel, K. Bruning, D.B. Parker. 2017. Farm-scale testing of soybean peroxidase and calcium peroxide for surficial swine manure treatment and mitigation of odorous VOCs, ammonia, hydrogen sulfide emissions. Atmospheric Environment, 166, 467-478. doi: 10.​1016/​j.​atmosenv.​2017.​07.​048.
  • Maurer, D., J.A. Koziel, J.D. Harmon, S.J. Hoff, A.M. Rieck-Hinz, D.S Andersen. 2016. Summary of performance data for technologies to control gaseous, odor, and particulate emissions from livestock operations: Air Management Practices Assessment Tool (AMPAT). Data in Brief, 7, 1413-1429. doi: 10.1016/j.dib.2016.03.070.

Acknowledgments

We are thankful to (1) National Pork Board and Indiana Pork for funding this project (NBP-17-158), (2) cooperating farms for donating swine manure and (3) manufacturers for providing products for testing. We are also thankful to coworkers in Dr. Koziel’s Olfactometry Laboratory and Air Quality Laboratory, especially Dr. Chumki Banik, Hantian Ma, Zhanibek Meiirkhanuly, Lizbeth Plaza-Torres, Jisoo Wi, Myeongseong Lee, Lance Bormann, and Prof. Andrzej Bialowiec.

 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2019. Title of presentation. Waste to Worth. Minneapolis, MN. April 22-26, 2019. URL of this page. Accessed on: today’s date.

 

Seasonal and Spatial Variations in Aerial Ammonia Concentrations in Deep Pit Beef Cattle Barns

There are known benefits and challenges to finishing beef cattle under roof. The accumulated manure is typically stored in either a bedded pack (mixture of bedding and manure) or in a deep pit below a slatted floor.  Previous research measured particulate matter, ammonia and other gases in bedded pack barn systems. Deep pit manure storages are expected to have different aerial nutrient losses and manure value compared to solid manure storage and handling. Few studies have looked at concentrations at animal level or aerial/temperature distributions in the animal zone. There is little to no documentation of the air quality impacts of long-term deep pit manure storage in naturally ventilated finishing cattle barns. The objective of this work is to describe the seasonal and spatial variations in aerial ammonia concentrations in deep pit beef cattle barns.

What Did We Do?

We measured ammonia concentrations among four pens in three beef cattle barns oriented east and west with deep pit manure storage during summer and fall conditions in Minnesota. We measured the concentration below the slatted floor (above the manure surface), 4-6 inches above the floor (floor level) and 4 ft above the floor (nose level). While collecting samples from within a pen, we also collected samples from the north and south wall openings surrounding the pen. We collected air and surface temperatures, air speed at cow level, and surface manure samples to supplement the concentration data. We collected measurements three times between 09:00 and 17:00 on sampling days. The cattle (if present) remained in the pen during measurement collection.

All farms had 12 ft deep pits below slatted floors, and pen stocking densities of 22 ft2 per head at capacity. Barn F finished beef cattle breeds under a monoslope roof, in four pens, with feed alleys on north and south side of pens. Two pens shared a common deep pit, and the farm pumped manure from the deep pits 1 week prior to the fall sampling period. Two pens were empty and the other two pens partially filled with cattle during the fall sampling period. Barn H finished dairy steers under a gable roof in a double-wide barn, in twelve pens over a deep pit and two pens with bedded packs, with a feed alley down the center of the barn. Four (east end) and eight (west end) pens shared common deep pits; the bedded pack pens were in the middle of the barn. The farm moved approximately 1 foot of manure from the east end pit to the west end pit one week prior to fall sampling period. Barn R finished dairy steers under a gable roof with four pens and a feed alley on the north side of the pens. All pens shared a common deep pit. Two pens were empty of cattle during the summer and fall sampling periods.

What Have We Learned?

The ammonia concentration levels differed based on the location in the pen area (Figures 1 and 2). As expected, the ammonia concentrations in the pit headspace above the manure surface was the greatest, and at times more than 10x the concentration at floor and nose level. The higher concentration levels measured at Barn F coincided with higher manure nitrogen levels (Total N and Ammonium-N) (Figure 2). Based on July and September measurements, higher ammonia concentration levels also coincided with higher ambient temperatures (Figure 1). The presence and size of cattle in the pens we measured did not strongly influence ammonia concentrations at any measurement height within a barn on sampling days.

Ammonia concentration is variable between barns, and within barns. However, at animal and worker level, average concentrations for the sampling periods were less than 10 ppm during the summer and fall periods. Higher gas levels can develop in the confined space below the slatted floor.

Future Plans

The air exchange between the deep pit headspace and room volume relates these two areas, but is challenging to measure. We are looking at indirect air exchange estimations using ammonia and other gas concentration measurements collected to quantify the amount of air movement through the slatted floor related to environmental conditions. Additional gas and environmental data collected will enhance our understanding of deep pit beef cattle barn environments.

Authors

Erin Cortus, Assistant Professor and Extension Engineer, University of Minnesota

ecortus@umn.edu

Brian Hetchler, Research Technician, University of Minnesota; Mindy Spiehs, Research Scientist, USDA-ARS; Warren Rusche, Extension Associate, South Dakota State University

Additional Information

USDA is an equal opportunity provider and employer

Acknowledgements

The research was supported through USDA NIFA Award No. 2015-67020-23453. We appreciate the producers’ cooperation for on-farm data collection. Thank you to S. Niraula and C. Modderman for assisting with measurements.

Figure 1. Average ammonia concentration levels in the animal and worker zone for three deep pit beef cattle barns during spring and fall sampling days, and the corresponding airspeed and temperature at cow nose level.
Figure 1. Average ammonia concentration levels in the animal and worker zone for three deep pit beef cattle barns during spring and fall sampling days, and the corresponding airspeed and temperature at cow nose level.
Figure 2. Average ammonia concentration levels at nose and manure surface levels for three deep pit beef cattle barns during spring and fall sampling days, and the corresponding surface* manure characteristics. (* Barn F 14-Sep-18 manure sample was an agitated sample collected during manure removal).
Figure 2. Average ammonia concentration levels at nose and manure surface levels for three deep pit beef cattle barns during spring and fall sampling days, and the corresponding surface* manure characteristics. (* Barn F 14-Sep-18 manure sample was an agitated sample collected during manure removal).

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2019. Title of presentation. Waste to Worth. Minneapolis, MN. April 22-26, 2019. URL of this page. Accessed on: today’s date.

Sodium Bisulfate Treatment of Horse Stalls in the Southeastern United States

For the equine industry, concerns about ammonia (NH3) levels in the barn environment are multifaceted and include issues of animal welfare, animal and human health, and environmental impacts. In Florida, many performance horses are housed in stalls at least part of the day as are horses with allergic skin conditions and/or pasture associated asthma. The warm and humid climate produces favorable conditions for ammonia generation and fly emergence. Previous research has demonstrated the effectiveness of sodium bisulfate in lowering floor substrate and bedding pH, reducing ammonia concentrations, and fly populations in livestock facilities (poultry houses and dairies)1,2. However, research on application of sodium bisulfate in equine facilities is limited to two studies conducted in the northeastern United States3.

What did we do?

The objective of this pilot study was to determine the effects of sodium bisulfate (PLT®) application in a north central Florida equine facility on bedding pH, NH3 concentration, and fly counts. Four 12 x 12 ft stalls in a 20-stall barn were used, 2 control (CON) and 2 treated with sodium bisulfate (SB), individually housing mature geldings. Data were collected during the third week of August, 2018. Stalls were initially bedded with 67 lbs of wood shavings. Amount of product initially added to SB stalls was 14 lbs (manufacturer recommended application rate of 100 lbs/1,000 sqft) followed by 7 lbs daily for 4 days. Horses were housed in stalls overnight (12 hours/day) and stalls cleaned (manure and wet bedding removed) once/day. An aspirating pump and gas detection tubes (Kitagawa, Japan) were used to determine NH3 concentration before stall cleaning (AM measurement), to allow for manure and urine accumulation, and 10 hours post stall cleaning (PM measurement). Three 5-gallon buckets were placed over the stall surface in a triangular pattern to standardize airflow and the location of each bucket was marked to allow replication across AM and PM readings. OnSet HOBO loggers were used to monitor temperature and relative humidity. Fly traps containing no fly attractant, were suspended 8 feet above the floor in the center of each stall to determine fly counts.

What Have We Learned?

Background (cleaned stalls without bedding material; rubber mats only) and baseline (bedded stalls) NH3 concentrations were < 5 ppm and not different between SB and CON stalls. NH3 concentrations had a cumulative effect and were greater on day 3 (69.8 ppm) compared to day 1 (< 5 ppm) and day 2 (16.7 ppm). NH3 concentrations were greater in CON stalls (28.6 ppm) compared to SB stalls (< 5 ppm). Bedding pH was lower in SB stalls (1.82) compared to CON stalls (6.16) demonstrating an overall treatment effect, but pH of the bedding increased over the duration of the study. The number of flies caught in traps did not differ between treatments, although fly counts did increase over time. Reductions in pH and NH3 observed in the present study were comparable to previous studies. We expected reductions in flies in stalls treated with SB, however, fly counts were extremely low overall and a different approach for quantifying fly numbers may be necessary.

Future Plans

Future research directions include testing different application rates for equine stalls and determining efficacy of SB with different bedding types. Additional studies to investigate the effectiveness of SB in mitigating NH3 emissions in equine facilities4 and reducing fly populations and bacteria in stalls should be pursued. There is also potential to assess the benefits of SB application near manure storage areas on equine operations.

Corresponding author, title, affiliation and email

Carissa Wickens, Extension Equine Specialist, University of Florida.   cwickens@ufl.edu

Other authors: Jill Bobel, Biological Scientist, University of Florida; Danielle Collins, Graduate Student, University of Florida; Alex Basso, Graduate Student, University of Florida

Additional information:

1Johnson, T. M. and B. Murphy. 2008. Use of sodium bisulfate to reduce ammonia emissions from poultry and livestock housing. Proceedings of the Mitigating Air Emissions from Animal Feeding Operations Conference, Des Moines, IA. Iowa State University, pp. 74-78.

2Sun, H., Y. Pan, Y. Zhao, W. A. Jackson, L. M. Nuckles, I. L. Malkina, V. E. Arteaga and F. M. Mitloehner. 2008. Effects of sodium bisulfate on alcohol, amine, and ammonia emissions from dairy slurry. J. Environmental Quality 37:608-614. 

3Sweeney, C.R., S.M. McDonnell, G.E. Russell, and M. Terzich. 1997. Effect of sodium bisulfate on ammonia concentration, fly population, and manure pH in a horse barn. Am. J. Vet. Res. 57(12):1795-1798.

4Weir, J., H. Li, L.K. Warren, E. Macon, C. Wickens. 2017. Evaluating the impact of ammonia emissions from equine operations on the environment. Waste to Worth: Spreading Science and Solutions. Cary, NC. April 18-21, 2017. https://lpelc.org/evaluating-the-impact-of-ammonia-emissions-from-equine-operations-on-the-environment/. Accessed on: February 28, 2019.

Additional information regarding this project is available by contacting Carissa Wickens (cwickens@ufl.edu), or Jill Bobel (jbrides2@ufl.edu).

Acknowledgements:

The authors wish to thank Dr. Josh Payne, Technical Services Manager, Jones-Hamilton Company, Agricultural Division, and Dr. Hong Li, Associate Professor, Department of Animal and Food Sciences, University of Delaware for providing technical expertise and support for this project. We would also like to thank Carol Vasco, Tayler Hansen, Agustin Francisco, and Claudia Lopez for their assistance with data collection.

Figure 1: Placement of buckets over the stall floor for measurement of NH3 concentrations. The ammonia pump with attached gas detection tube was placed through a small hole drilled into the top of each bucket.
Figure 1: Placement of buckets over the stall floor for measurement of NH3 concentrations. The ammonia pump with attached gas detection tube was placed through a small hole drilled into the top of each bucket.
Figure 2: Average daytime and nighttime temperatures and percent relative humidity during the study period.
Figure 2: Average daytime and nighttime temperatures and percent relative humidity during the study period.

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2019. Title of presentation. Waste to Worth. Minneapolis, MN. April 22-26, 2019. URL of this page. Accessed on: today’s date.

The Use of USDA-NRCS Conservation Innovation Grants to Advance Air Quality Improvements

USDA-NRCS has nearly fifteen years of Conservation Innovation Grant project experience, and several of these projects have provided a means to learn more about various techniques for addressing air emissions from animal agriculture.  The overall goal of the Conservation Innovation Grant program is to provide an avenue for the on-farm demonstration of tools and technologies that have shown promise in a research setting and to further determine the parameters that may enable these promising tools and technologies to be implemented on-farm through USDA-NRCS conservation programs.

What Did We Do?

Several queries for both National Competition and State Competition projects in the USDA-NRCS Conservation Innovation Grant Project Search Tool (https://www.nrcs.usda.gov/wps/portal/nrcs/ciglanding/national/programs/financial/cig/cigsearch/) were conducted using the General Text Search feature for keywords such as “air”, “ammonia”, “animal”, “beef”, “carbon”, “dairy”, “digester”, “digestion”, “livestock”, “manure”, “poultry”, and “swine” in order to try and capture all of the animal air quality-related Conservation Innovation Grant projects.  This approach obviously identified many projects that might be related to one or more of the search words, but were not directly related to animal air quality. Further manual review of the identified projects was conducted to identify those that specifically had some association with animal air quality.

What Have We Learned?

Out of nearly 1,300 total Conservation Innovation Grant projects, just under 50 were identified as having a direct relevance to animal air quality in some way.  These projects represent a USDA-NRCS investment of just under $20 million. Because each project required at least a 50% match by the grantee, the USDA-NRCS Conservation Innovation Grant program has represented a total investment of approximately $40 million over the past 15 years in demonstrating tools and technologies for addressing air emissions from animal agriculture.

The technologies that have been attempted to be demonstrated in the animal air quality-related Conservation Innovation Grant projects have included various feed management strategies, approaches for reducing emissions from animal pens and housing, and an approach to mortality management.  However, the vast majority of animal air quality-related Conservation Innovation Grant projects have focused on air emissions from manure management – primarily looking at anaerobic digestion technologies – and land application of manure. Two projects also developed and enhanced an online tool for assessing livestock and poultry operations for opportunities to address various air emissions.

Future Plans

The 2018 Farm Bill re-authorized the Conservation Innovation Grant Program through 2023 at $25 million per year and allows for on-farm conservation innovation trials.  It is anticipated that additional air quality projects will be funded under the current Farm Bill authorization.

Authors

Greg Zwicke, Air Quality Engineer, USDA-NRCS National Air Quality and Atmospheric Change Technology Development Team

greg.zwicke@ftc.usda.gov

Additional Information

More information about the USDA-NRCS Conservation Innovation Grants program is available on the Conservation Innovation Grants website (https://www.nrcs.usda.gov/wps/portal/nrcs/main/national/programs/financial/cig/), including application information and materials, resources for grantees, success stories, and a project search tool.

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2019. Title of presentation. Waste to Worth. Minneapolis, MN. April 22-26, 2019. URL of this page. Accessed on: today’s date.

Evaluating the Impact of Ammonia Emissions from Equine Operations on the Environment


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Purpose 

In the United States, animal agriculture is the largest source of ammonia (NH3) emissions that are a major air and water pollutant contributing to eutrophication, soil acidity, and aerosol formation that can impair atmospheric visibility and human health. Ammonia volatilization occurs when excess crude protein (CP) is fed and excreted as urinary nitrogen, primarily as urea. Information regarding NH3 emissions from equine operations is limited. It is generally understood that air quality in stables can adversely affect both horse and human health, however, the effects of different housing systems and nutritional management of horses on air quality have received little investigation.

What did we do? 

In the first study, 9 mature horses were used in a 3 X 3 replicated Latin square design study to determine the effects of dietary CP concentrations on potential NH3 losses from feces and urine. Horses were fed 3 diets formulated using bahiagrass and Tifton-85 bermudagrass hays and a commercial vitamin mineral supplement. The 3 diets differed in dietary CP concentration and were labelled as: LOW-CP, MED-CP, and HIGH-CP (10.6, 11.5 and 12%, respectively). Total collection of feces and urine was conducted over 3 days. For in-vitro determination of NH3 concentrations, urine samples were pooled and mixed with either wheat straw or wood shavings, while fecal samples were pooled and mixed with wheat straw. Ammonia emission by these samples was measured using a vessel emission system with an airflow rate (2.5 L min-1) at 20°C over a 7-d period. Concentration of NH3 in each vessel was measured using a photoacoustic multi-gas analyzer. Temperature, airflow rate and NH3 concentration in each vessel were used to calculate NH3 emission rate (ER).

The objective of the second study was to determine air emissions from 4 Mid-Atlantic equine operations as affected by housing type and feeding practices. A questionnaire was administered to respective farm managers to record facility and individual stall dimensions, daily cleaning practices, and feeding practices. Farm A was a University riding stable, Farm B was a University breeding farm, Farm C was a racehorse training facility, and Farm D was a Standardbred breeding facility. At least 4 stalls were chosen in each facility based upon location within barn to quantify NH3 concentrations. Body weight, breed, age, class of horse, exercise schedule, and time spent in the stall were recorded for the horses in the selected stalls. For analysis of NH3 concentration, air samples were collected from stall floors using a dynamic flux chamber and concentrations measured using a photoacoustic NH3 analyzer. To achieve a representation of NH3 emitted from stall surfaces, 5 locations were selected and measurements taken at approximately the same time each day. Temperature, airflow rate and a weighted concentration of NH3 in the flux chamber were used to calculate NH3 emissions.

 

Figure 1 Cumulative ammonia emissions rate of urine when mixed with A) shavings and B) straw and incubated

Figure 2. Daily ammonia emissions per horse over 3 days using the flux chamber system on 4 horse operations

What have we learned? 

When measuring NH3 concentrations and calculating the ER in-vitro, urinary-N was the main source of NH3 volatilized from equine manure, potentially due to the high urea-N concentration in the urine. Cumulative fecal NH3 emissions ranged from 19.7 to 39.8 mg/m2 and contributed only a small amount in comparison to the NH3 lost from urine. While dietary CP intake did not influence NH3 emissions, cumulative emissions tended to be higher when horses consumed more CP. Urinary NH3 emissions were greater when mixed with wheat straw compared to wood shavings. This study shows there may be a relationship between dietary CP intake and potential NH3 losses from equine urine under laboratory conditions. When estimating NH3 emissions on the 4 equine operations, greater dietary CP intake was associated with increased urinary NH3 volatilization. Daily CP intake ranged from 149-211 % above NRC CP requirement. Estimated NH3 emissions from facilities ranged from 18.5 to 124 g d-1 horse-1 and were similar to emissions previously reported from other large livestock species. Differences in NH3 emissions could be due to several factors including cleaning practices and ventilation rate. These studies provide a better understanding of the impact equine operations are having on atmospheric NH3 levels.

Future Plans    

Future research will aim to quantify NH3 emissions from entire equine operations as well as accounting for diurnal, seasonal and regional fluxes in NH3. In addition, there is interest to determine how protein quality will affect NH3 emissions from horse urine.

Corresponding author, title, and affiliation        

Jessie Weir, University of Florida

Corresponding author email   

jessie23@ufl.edu

Other authors   

Hong Li, Assistant Professor, University of Delaware; Lori K. Warren, Associate Professor, University of Florida; Erica Macon, Graduate Student, Middle Tennessee State University; Carissa Wickens, Extension Equine Specialist, University of Florida

Additional information               

Additional information regarding these projects is available by contacting Jessie Weir (jessie23@ufl.edu), or Carissa Wickens (cwickens@ufl.edu). 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2017. Title of presentation. Waste to Worth: Spreading Science and Solutions. Cary, NC. April 18-21, 2017. URL of this page. Accessed on: today’s date.

Using Wet Scrubber to Reduce Ammonia Emission from Broiler Houses


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Purpose 

Research on mitigating the effects of animal feeding operations (AFOs) on air quality in the US has made great strides in recent years. Development of cost-effective air emission mitigation and assessing the effectiveness of these technologies is urgently needed to improve our environmental performance and to help producers address increasing regulatory pressures. Scrubbers have been shown to be a powerful tool in reducing ammonia (NH3), dust and odor emissions. An affordable two-stage acid scrubber was developed by USDA ARS for treating exhaust air and can easily be installed onto the exhaust fans of existing poultry facilities. A field project was conducted to evaluate the efficiency of the acid scrubber under field conditions on three broiler farms, two located in Delaware (DE) and one located in Pennsylvania (PA).

What did we do? 

The two-stage scrubbers were installed on the minimum fans of three farms that were using different practices and settings. One farm used 36” minimum fans and reused existing litter throughout the project while an organic farm used a 36” minimum fan, but used new bedding materials for every flock. The third scrubber was installed on a research farm with a 24” minimum fan and used litter. Sodium bisulfate was used as the acid agent. Ammonia concentration and airflow rate through each fan were continuously measured. Scrubber liquid samples were analyzed to calculate the efficiency of each scrubber. Acid, water and electricity consumption of each scrubber were recorded over multiple flocks and seasons.

What have we learned?              

The mean NH3 capturing efficiencies of the three scrubbers for the three sites were 31.3, 34.3 and 11.0 %, respectively. The low efficiency (11%) of one scrubber was due to high NH3 emission rate and inadequate acid solution in the scrubber (the solution at this site was checked and replaced weekly whereas the solution at the other two sites were checked daily). For every kg NH3 captured, the average water, sodium bisulfate and electricity consumption at the three sites were 0.23 m3, 15.10 kg and 43.74 kWh, respectively.

Future Plans 

Based on the field experiences of running the three scrubbers, several recommendations are suggested: 1) increase fan run time to compensate for air flow loss due to high pressure drop, 2) add insulation on drain valves, 3) heat fresh water line and add a heater in pump boxes, 4) clean dust scrubber at least twice per flock for houses with used litter, 5) replace acid solution more frequently toward end of the flock for best performance, 6) add a storage tank for spent liquid if the growers do not have crops or pasture to apply to, and 7) add an automatic acid dosing system to reduce labor requirement and improve scrubber performance.

Corresponding author, title, and affiliation        

Hong Li, Assistant Professor, University of Delaware

Corresponding author email    

hli@udel.edu

Other authors   

Chen Zhang, Philip Moore, Michael Buser, Cathleen J. Hapeman, Paul Patterson, Gregory Martin, Jerry Martin

Additional information              

Zhang, Chen, Hong Li , Philip A Moore , Michael Buser, Cathleen J. Hapeman, Paul Patterson, Gregory Martin. 2016. ASABE Annual International Conference. Paper number 2461008; Orkando,Florida, July 17 – July 20.

Acknowledgements       

This study was partially supported by funds from USDA-NRCS Conservation Innovation Grant Program (Award No. NRCS 69-3A75-12-244), University of Delaware, Penn State University, Oklahoma State University, University of Maryland, and USDA-ARS. The cooperation and assistance of the collaborating producer is also acknowledged.

 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2017. Title of presentation. Waste to Worth: Spreading Science and Solutions. Cary, NC. April 18-21, 2017. URL of this page. Accessed on: today’s date.

Poultry Digestion – Emerging Farm-Based Opportunity

While EPA AGSTAR has long supported the adoption of anaerobic digestion on dairies and swine farms, they have not historically focused on the use of anaerobic digestion on egg laying and other poultry facilities. This has been because the high solids and ammonia concentrations within the manure make anaerobic digestion in a slurry-based system problematic. Development of enhanced downstream ammonia and solids recovery systems is now allowing for effective digestion without ammonia toxicity. The process also generates dilution water, avoiding the need for fresh water consumption, and eliminating unwanted effluent that needs to be stored or disposed of to fields. The system produces high-value bio-based fertilizers. In this presentation, a commercial system located in Fort Recovery Ohio will be used to detail the process flow, its technologies, and the co-products sold.

Why Examine Anaerobic Digestion on Poultry Farms?

The purpose of this presentation is to supply a case study on a commercial poultry digestion project for production of combined heat and power as well as value-added organic nutrients on a 1M egg-layer facility in Ohio.

What did we do?

In this study we used commercial farm information to demonstrate that poultry digestion is feasible in regard to overcoming ammonia inhibition while fitting well into an existing egg-layer manure management system. Importantly, during the treatment process a significant portion of nutrients within the manure are concentrated for value-added sales, ammonia losses to the environment are reduced, and wastewater production is minimized due to recycle of effluent as dilution water.

What have we learned?

In this study, commercial data shows that ammonia and solids/salts levels that are potentially inhibitory to the biology of the digestion process can be controlled. The control is through a post-digestion treatment that includes ammonia stripping and recovery as ammonium sulfate as well as fine solids separation using a dissolved air flotation process with the addition of a polymer. The resulting treated effluent is sent back to the front of the digester as dilution water for the high solids poultry manure. The separated fine solids and the ammonium sulfate solution are dried using waste engine heat to produce a nutrient-rich fertilizer for off-farm sales. The stable anaerobic digestion process resulting from the control of potential inhibitors that might accumulate in the return water, if no post-treatment occurred, leads to production of a significant supply of electrical power for sales to the grid.

Demonstration at commercial scale shows the promise anaerobic digestion with post-digestion treatment and effluent recycle can play in a more sustainable poultry manure treatment system including managing nutrients for export out of impacted watersheds.

Future Plans

Future plans include continued work with industry in developing and/or providing extension capabilities around novel digestion and post-treatment processes for a variety of manures and on-farm situations. Expansion of such processes to poultry and other on-farm business plans will allow for improved reductions in wastewater production, concentrate nutrients for export out of impacted watersheds and do so within a positive economic business plan.

Authors

Craig Frear, Assistant Professor at Washington State University cfrear@wsu.edu

Quanbao Zhao, Project Engineer DVO Incorporated, Steve Dvorak, President DVO Incorporated

Additional information

Additional information about the corresponding author can be found at http://www.csanr.wsu.edu while information about the poultry project and the industry developer can be found at http://www.dvoinc.net. Numerous articles related to anaerobic digestion, nutrient recovery and separation technologies for climate, air, water and human health improvements can be found at the WSU website using their searchable articles function.

Acknowledgements

This research was supported by funding from USDA National Institute of Food and Agriculture, Contract #2012-6800219814; National Resources Conservation Service, Conservation Innovation Grants #69-3A75-10-152; and Biomass Research Funds from the WSU Agricultural Research Center. 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.

 

Scientific Evidence Indicates that Reducing NOx Emissions is the Most Effective Strategy to Reduce Concentrations of Ammonium Nitrate, a Significant Contributor to PM2.5 Concentrations in California’s San Joaquin Valley

Recently there has been increased interest in regulating ammonia emissions to reduce PM2.5 (“fine” particles with an aerodynamic diameter less than 2.5 micrometers)  concentrations.  However, understanding the quantity of and interactions between ammonia and nitrogen oxide (NOx) is necessary in determining whether controlling ammonia is an effective strategy for reducing PM2.5 in a particular region.  Research from the California Regional Particulate Air Quality Study and other studies has demonstrated the relative abundance of ammonia in comparison to the limited concentrations of the other key precursor, nitric acid formed by NOx emissions.  As a result, NOx acts as the primary limiting precursor for the formation of secondary ammonium nitrate in the San Joaquin Valley (SJV).  Modeling based on data from these studies also found that controlling NOx was the most effective strategy to reduce ammonium nitrate particulate in the SJV and controlling ammonia had little effect on PM2.5 concentrations. 

In summary and as explained in the San Joaquin Valley Air Pollution Control District 2012 PM2.5 Plan, the best scientific information available indicates that controlling NOx emissions is the most effective strategy to reduce secondary ammonium nitrate in the SJV.  While it has been demonstrated that controlling ammonia will not significantly reduce PM2.5 concentrations in the SJV, the District has adopted stringent regulations that have significantly reduced ammonia emissions.

Purpose

The San Joaquin Valley is primarily a rural region with large areas dedicated to agriculture. Recently there has been increased interest in regulating ammonia emissions from agricultural operations and other sources as a means to reduce PM2.5 concentrations. However, understanding the quantity and interactions between ammonia and NOx are necessary in determining whether controlling ammonia emissions is an effective strategy for reducing secondary PM2.5 formation in a particular geographic region.

average of peak day pm2.5 chemical composition

The United States Environmental Protection Agency (U.S. EPA) periodically reviews and establishes health-based air quality standards (often referred to as National Ambient Air Quality Standards, or NAAQS) for ozone, particulate matter (PM), and other pollutants. Although the air quality in California’s San Joaquin Valley has been steadily improving, the region is currently classified as “serious” non-attainment for the 1997 and 2006 federal ambient air quality standards for PM2.5. The periods for which measured PM2.5 concentrations drive nonattainment of these standards occur primarily in the winter months and air quality research in the San Joaquin Valley has identified ammonium nitrate as the predominant contributor to secondary PM2.5 in the region. Ammonium nitrate particulate is formed through chemical reactions between ammonia in the air and NOx emissions produced by mobile and stationary combustion sources. As shown in Figure 1 above, ammonium nitrate is commonly the largest contributor to PM2.5 mass during the winter in the San Joaquin Valley.

What did we do?

modeled ammonium nitrate response to NH3 vs NOxAtmospheric modeling has demonstrated that controlling NOx is the most effective strategy to reduce ammonium nitrate concentrations in the San Joaquin Valley and controlling ammonia has little effect on these concentrations. The California Air Resources Board conducted multiple modeling runs to simulate the formation of PM2.5 in the San Joaquin Valley and compare the effect of reducing various pollutants on PM2.5 concentrations. As seen in Figure 2, U.S. EPA’s Community Multi-scale Air Quality (CMAQ) indicated that reducing NOx by 50% reduced nitrate concentrations by 30% to 50% reductions, while reducing ammonia by 50% resulted in less than 5% reductions in nitrate concentrations. Similarly, the UCD/CIT photochemical transport model indicated that for the conditions on January 4-6, 1996 in the San Joaquin Valley, controlling NOx emissions is far more effective for reducing nitrate concentrations than controlling ammonia.

What have we learned?

abundance of NH3 in San Joaquin ValleyAmmonium nitrate particulate is limited by NOx in the San Joaquin Valley

Extensive research conducted through the California Regional Particulate Air Quality Study (CRPAQS) and other studies has demonstrated the relative abundance of ammonia in comparison to the limited concentrations of the other key precursor, nitric acid formed by NOx emissions in the San Joaquin Valley. As a result, NOx (via nitric acid) acts as the primary limiting precursor for the formation of secondary ammonium nitrate. (See Figures 3 and 4)

Future Plans

NOx control reduces ammonium nitrate more efficientlyAs explained in detail in the San Joaquin Valley Air Pollution Control District 2012 PM2.5 Plan, the best scientific information available indicates that controlling NOx emissions is the most effective strategy to reduce secondary ammonium nitrate in the San Joaquin Valley. While ammonia has been demonstrated to not significantly contribute to PM2.5 concentrations in the San Joaquin Valley, the District has developed control strategies, via stringent regulations (Confined Animal Facilities – Rule 4570, Organic Material Composting – Rule 4566, Biosolids, Animal Manure, and Poultry Litter Operations – Rule 4565), that have resulted in significant reductions in ammonia emissions.

Authors

Errol Villegas, Program Manager, San Joaquin Valley Air Pollution Control District errol.villegas@valleyair.org

Ramon Norman, Air Quality Engineer, San Joaquin Valley Air Pollution Control District

Additional information

California Air Resources Board Technical Symposium: Scientific Basis of Air Quality Modeling for the San Joaquin Valley 2012 PM2.5 Plan (April 27, 2012). Fresno, CA

Magliano, K. L. & Kaduwela, A. P. (2012) California Air Resources Board Technical Symposium: Technical Basis of the 2012 San Joaquin Valley PM2.5 Plan Modeling. Fresno, CA.

San Joaquin Valley Unified Air Pollution Control District. 2012 PM2.5 Plan (2012), Chapter 4 – Scientific Foundation and PM2.5 Modeling Results

Chen, J.; Lu, J.; Avise, J. C.; DaMassa, J. A.; Kleeman, M. J. & Kaduwela, A. P. (2014), Seasonal modeling of PM2.5 in Californias San Joaquin Valley, Atmospheric Environment 92, p. 182-190.

Kleeman, Michael J., Qi Ying, Ajith Kaduwela (2005) Control Strategies for the Reduction of Airborne Particulate Nitrate in California’s San Joaquin Valley. Atmospheric Environment, 39 (29), p. 5325 – 5341

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.