Electrochemical K-struvite formation for simultaneous phosphorus and potassium recovery from hog and dairy manures

Purpose

Intensive animal husbandry produces large  volumes of liquid manure with significant amounts of phosphorus, ammonium, and potassium as they pass through the feed of farm animals. As a result, direct land application of manure, the current common approach, causes environmental concerns such as soil over-fertilization and groundwater and surface water contamination, which leads to eutrophication. Manure nutrient management is, therefore, necessary to address these problems. While most engineering options are focused on phosphorus and ammonium recovery, few studies have pursued recovery methods for potassium. In this talk, we present an electrochemical technology using a sacrificial magnesium anode and a stainless-steel cathode for simultaneous recovery of phosphorus and potassium in the form of potassium-magnesium-phosphate (KMgPO4·xH2O, K-struvite).

Mg2+ + K+ + HnPO4n-3 + 6H2O = KMgPO4*6H2O + nH+

K-struvite has the potential to be used as a slow-release fertilizer and this technology will add flexibility to the  manure management strategies currently available by diversifying the recoverable by-products.

What Did We Do?

Figure 1. Calculated saturation index values as a function of pH. The water matrix contains 3000 mg/L potassium, 1000 mg/L phosphate, and magnesium with Mg:P ratio of 1.4.

To predict the thermodynamic stability of K-struvite, a thermodynamic model was developed based on the average ion concentrations of phosphorus, and potassium measured in real liquid pig manure (Figure 1). According to this model, magnesium phosphate is a possible by-product of K-struvite precipitation. Also, the probable formation of magnesium hydroxide was enhanced with increasing pH value due to the increase in hydroxide ion concentration. As a result, the ideal range for precipitation of K-struvite lies at pH values between 10 and 11.

To understand the role of pH on K-struvite formation, a 50 mM KH2PO4 solution was used to perform the preliminary batch electrochemical experiments. A constant voltage of -0.8 V vs. the Ag/AgCl reference electrode was applied to the pure magnesium anode using a potentiostat. One experiment was performed on the natural pH of the initial solution, 4.5, while potassium hydroxide was used to raise the initial pH of the second experiment to 9.5.

What Have We Learned?

Figure 2. The EDS results obtained of the recovered precipitates (a) pH=4.5, (b) pH=9.5 in 50 mM KH2PO4.

Energy-dispersive x-ray spectroscopy (EDS) of the recovered precipitates (Figure 2) indicate that by raising the initial pH from 4.5 to 9.5 the amount of potassium is increased in the precipitates. Also, due to the equimolar ratios of K:Mg:P at pH=9.5, the produced precipitates are likely K-struvite, while the pH= 4.5 sample likely contains some amount of magnesium phosphate.

This process also eliminates the disadvantages of the commonly used chemical precipitation methods, including magnesium salt dosing, and adding base to the system for pH control, due to in situ magnesium corrosion and hydroxide production at the magnesium anode surface. These advantages could potentially reduce the operating cost of the system and eliminate the addition of unnecessary salinity to wastewater through magnesium salt dosing.

Future Plans

Further investigation by using multiple characterization techniques (e.g., x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR)) is necessary to identify the exact nature of precipitates. The initial experiments will be repeated at additional pH values to further understand the role of pH on the precipitation of K-struvite in the simplified synthetic wastewater and to further detail the characterization of the composition and morphology of K-struvite precipitates. These experiments are valuable , particularly because there are few literature reports that detail the physical and chemical structure of K-struvite.

Authors

Presenting author

Amir Akbari, Ph.D. Candidate, Department of Chemical and Biomedical Engineering, Pennsylvania State University

Corresponding author

Lauren F. Greenlee, Associate Professor, Department of Chemical and Biomedical Engineering, Pennsylvania State University

Corresponding author email address

greenlee@psu.edu

 

Additional Information

Once completed, future publications and data repository information will be available at https://sites.psu.edu/greenlee/

Acknowledgements

The authors would like to thank the U.S. Department of Agriculture, NIFA AFRI Water for Food Production Systems (#2018-68011-28691) for providing the funding support of this research through the “Water and Nutrient Recycling: A Decision Tool and Synergistic Innovative Technology” project.

 

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. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.

Electrocatalytic reduction of nitrate on hydrophobic, negatively, and positively charged peptide-coated gold electrodes

Purpose

As a pollutant in water resources, nitrate is a target contaminant for removal by water treatment technologies. Therefore, it is necessary to develop new techniques of water treatment to remove nitrate from water resources. This study worked on developing a new technique for nitrate reduction and to produce valuable ()/harmless () products without employing energy-intensive processes. To reach this goal, it is necessary to understand the possibilities and the pathways of nitrate reduction by negatively and positively charged, and hydrophobic peptide-coated Au electrodes. Also, stability and kinetics analysis will help us to understand the durability and capability of peptide-coated Au electrodes for nitrate reduction.

What Did We Do?

In this study three different types of peptides including, hydrophobic (V type), negatively charged (E type), and positively charged (K type) peptides were synthesized. The synthesized peptides were coated on the surface of bare Au. To assess the response of peptide- coated Au electrodes, and to compare them with bare Au, cyclic voltammetry (CV) experiments were employed. To do the CVs, an electrochemical cell with the gold electrode (working electrode), platinum (counter electrode) electrode, and a background solution (0.5 M) were used for electrochemical experiments. As a source of nitrate, 0.1 M sodium nitrate was added to the background solution. Cyclic voltammetry trials were done on three different peptide-coated Au electrodes and bare Au electrode, with a scan rate of 20 mV/s. After CV analysis, and to analyze the products of nitrate reduction, potential hold experiments were done on peptides with promising responses to the CV experiments. In other words, a potential hold experiment with a potential equal to the onset potential of peptide-coated Au electrodes were employed for 1 hour. During the potential hold trials, samples  were analyzed using Ultraviolet–visible spectroscopy method in time intervals (e.g., every 10 minutes) to measure the concentration of ammonia and nitrite.

What Have We Learned?

Based on the preliminary results, Au electrodes coated by E and V peptides showed promising responses to the applied potential. Results indicate that reduction of nitrate takes place at the onset potentials of -0.35V and -0.23V versus reversible hydrogen electrode (RHE) for E and V types of peptide-coated Au electrodes, respectively. However, bare Au did not show a reduction peak in the voltammogram. Results of potential hold experiment and product analysis indicate that V and E peptide-coated Au electrodes are capable of nitrate reduction to both nitrite and ammonia. However, bare Au electrode can only reduce nitrate to ammonia.

Future Plans

To have a comprehensive analysis of products, gas chromatography will be used to measure the products (e.g., hydrogen and nitrogen) in gaseous phase. Also, to investigate the structure and stability of thiolate– gold bonding on the surface of Au electrodes, Fourier transform infrared (FTIR) method will be employed before CV, and potential hold experiments. A mass balance between products and nitrate available in the background solution will be done. Moreover, the rate and kinetics of nitrate reduction will be assessed using the product analysis data.

Authors

Presenting author

Arash Emdadi, Ph.D. student, Pennsylvania State University

Corresponding author

Lauren F. Greenlee, Associated Professor, Pennsylvania State University

Corresponding author email address

greenlee@psu.edu

Additional authors

Julie Renner, Assistant Professor, Case Western Reserve University; Amir Akbari, Ph.D. student, Pennsylvania State University

Additional Information

    1. Matteo Duca, Marc T. M. Koper, Powering denitrification: the perspectives of electrocatalytic nitrate reduction, Energy Environ. Sci., 2012, 5, 9726-9742. https://doi.org/10.1039/C2EE23062C
    2. Phebe H. van Langevelde, Ioannis Katsounaros, Marc T. M. Koper, Electrocatalytic Nitrate Reduction for Sustainable Ammonia Production, Joule, 2021, 5, 290–294. https://doi.org/10.1016/j.joule.2020.12.025

Acknowledgements

The authors acknowledge funding from the USDA NIFA AFRI Water for Food Production Systems program, grant #2018-68011-28691.

 

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. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.

Effects of centrifuges and screens on solids/nutrient separation and ammonia emissions from liquid dairy manure

Purpose

Some Idaho dairies use liquid manure handling systems that result in large amounts of manure applied via irrigation systems to adjacent cropland during the growing season. Solids and nutrients presented in liquid dairy manure pose challenges to manure handling. Separating solids and nutrients from liquid dairy manure is a critical step to improve nutrient use efficiency and reduce manure handling costs. Most Idaho dairies have primary screens that separate coarse particles from their liquid streams. A few dairies have incorporated secondary solid separation technologies (centrifuge and secondary screen) into their manure handling systems to achieve higher solids and nutrient removal rates. Idaho dairymen want to know more information about solid and nutrient separation efficiencies by centrifuges and screens to make informed decisions on upgrading their solid/nutrient separation technologies. The objectives of this study were to evaluate centrifuges and screens in terms of removing solids and nutrients from liquid dairy manure and affecting ammonia emissions from the treated liquid dairy manure.

What Did We Do?

A year-long evaluation of on-farm centrifuges and screens on removing solids and nutrients and affecting ammonia emissions from centrifuge- and screen-separated liquid dairy manure was conducted. Triplicate fresh liquid dairy manure samples were collected monthly from before and after screens and centrifuges on a commercial dairy meanwhile triplicate screen- and centrifuge separated solids were collected from the same dairy. Figure 1 shows the dairy’s liquid manure flow diagram and locations where the liquid and solid manure samples were collected. The collected solids were analyzed for nitrogen (N), phosphorus (P), and potassium (K) concentrations by a certified commercial laboratory. The collected liquid samples were analyzed for total and suspended solids based on Methods 2540B and D (APHA, 2012) in the Waste Management Laboratory at the UI Twin Falls Research and Extension Center. Ammonia emissions from the monthly collected liquid dairy manure were evaluated using Ogawa ammonia passive samplers outside the Waste Management Lab for a year. Ammonia emission rate was calculated based on the duration and NH4-N concentrations from the Ogawa ammonia passive sampler tests. Ogawa passive ammonia sampler and Quickchem 8500 analysis system are shown in Figures 2 and 3.

Figure 1. Liquid manure flow diagram (liquid manure samples were collected at points 1 (before screens), 3 (after screens), and 5 (after centrifuges), solid samples were collected at points 2 (screen separated solids) and 4 (centrifuge separated solids).
Figure 2. Ogawa ammonia passive sampler.
Figure 3. Quickchem 8500 analysis system (Lachat Instruments, Milwaukee, WI).

What Have We Learned?

Centrifuge can further remove finer particles than cannot be removed by primary screens. Figure 4 shows both the screen- and centrifuge separated solids.

Figure 4. Centrifuge separated (left) and screen (right) separated solids.

Total nitrogen, phosphorus, and potassium in screen- and centrifuge separated solids are shown in Figures 5, 6, and 7. It was noticed that centrifuge separated solids had significantly (P<0.05) higher N, P, and K than that in screen separated solids. Yearlong averages of 9.2 lb/ton of total nitrogen, 8.0 lb/ton of P2O5, and 7.2 lb/ton of K2O were in the centrifuge separated solids while yearlong averages of 5.4 lb/ton of total nitrogen, 2.0 lb/ton of P2O5, and 4.4 lb/ton of K2O were in the screen separated solids.

Figure 5. Total nitrogen in screen separated and centrifuge separated solids.
Figure 6. Phosphorus in screen separated and centrifuge separated solids.
Figure 7. Potassium in screen separated and centrifuge separated solids.

Liquid dairy manure total solids and suspended solids are shown in Figures 8 and 9. Both the total solids and suspended solids in the liquid stream were significantly (P<0.05) reduced after the screen and centrifuge treatment.

Figure 8. Total solids in raw (before screens), after screens, and after centrifuges.
Figure 9. Suspended solids in raw (before the screens), after the screens, and after the centrifuges.

It was found that there was no significant difference (p≥0.05) between treatments for the ammonia emission rate in Figure 10 Which indicates that further treatment is needed to reduce ammonia emissions.

Figure 10. Ammonia emission rate during the test period.

In Figure 11 a correlation was determined between ammonia emission rate and suspended solids. As suspended solids were reduced within liquid dairy manure the ammonia emission rate increased among the treatments.

Figure 11. Ammonia emission rate vs. suspended solids.

In Figure 12 a correlation was determined between ammonia emission rate and ambient temperature. As the ambient temperature increased, so did the ammonia emission rate among the treatments.

Figure 12. Ammonia emission rate vs. suspended solids.

The test results showed:

    1. Centrifuge can further remove finer particles that can’t be removed by primary screens.
    2. Centrifuge separated solids contained higher N, P, and K contents, especially P (at an average of 8 lb/ton of P2O5 in centrifuge separated solids vs. 2 lb/ton of P2O5 in screen separated solids).
    3. Ammonia emissions from raw liquid manure, screen- and centrifuge separated liquid manure did not show significant differences.
    4. The most influential factors for ammonia emissions from liquid dairy manure were ambient temperatures and suspended solids within the liquid dairy manure.

Future Plans

We will hold workshops and field days to communicate the results with producers and promote on-farm adoption of advanced separation equipment such as centrifuge.

Authors

Lide Chen, Waste Management Engineer, Department of Soil and Water Systems, University of Idaho

Corresponding author email address

lchen@uidaho.edu

Additional author

Kevin Kruger, Scientific Aide, Department of Soil and Water Systems, University of Idaho.

Additional Information

APHA. (2012). Standard Methods for the Examination of Water and Wastewater. Washington D.C. : American Public Heath Association., Pp. 2-64 and Pp. 2-66

Acknowledgements

USDA NIFA WSARE financially supported this study. Thanks also go to Scientists at USDA ARS Kimberly Station for their help with analyzing ammonia emission samples.

 

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. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.

Manure Nutrient Sensing Systems

Purpose

Manure is rich in essential elements, including nitrogen (N), phosphorus (P), and potassium (K), for plant growth. Although applying manure as a fertilizer at agronomic rates can restore organic matter and nutrients to the soil, over-application of manure may contribute to environmental issues such as eutrophication and water contamination. Manure nutrient prediction and variable rate application are promising new technologies to reduce the risk of over-application, however, the variability in manure nutrient concentrations and the time-lag caused by traditional chemical analysis of manure composition make precise nutrient application difficult to achieve.

Near-infrared (NIR) spectroscopy is a high-energy vibrational spectroscopy performed in the wavelength range between 750 to 2500 nm and has been proven to accurately determine total solid (TS), organic matter (OM), total nitrogen (TN), and ammoniacal nitrogen (NH4-N) of animal manure in several previous studies. A low-field nuclear magnetic resonance (NMR) device that is designed based on the absorption and emissions of energy in the radio frequency range of the electromagnetic spectrum is another potential method for predicting manure nutrients accurately. The main purpose of this manure sensing project was to determine if the NIR and NMR sensing techniques can provide robust prediction of manure nutrients and, therefore, improve the precision of field application.

What Did We D

We investigated NIR spectroscopy with reflectance and transflectance modes to predict micronutrients in dairy manure. In this study, 20 dairy manure samples were collected and spiked by dissolving a specific amount of ammonium chloride (NH4Cl) or Arginine to achieve incremental NH4-N and organic nitrogen (Org-N) concentrations, respectively. Each raw sample was spiked at four levels which were 1.25, 1.5, 2, and 4 times the NH4-N or Org-N concentrations of the raw manure as analyzed by a certified lab. All samples were scanned and analyzed using a NIR with a reflectance head sensor and a transflectance probe of three different optical path lengths. NIR calibration models were developed using partial least square regression analysis and the coefficient of determination (R2) and root mean square error (RMSE) were calculated to evaluate the models.

The accuracy and precision of a low-field NMR designated for manure nutrient prediction was assessed. Twenty dairy manure samples were collected and analyzed for TS, TN, NH4-N, and total phosphorus (TP) in a certified laboratory and using the NMR analyzer. Runtimes of 15 min to 90 min were tested to investigate their effects on accuracy and precision of NMR.

What Have We Learned

For the NIR study, the transflectance probe yielded calibrations that had higher R2 and RMSE for TS, ash, and particle size (PS), and reflectance sensor improved the accuracy of NH4-N and Org-N predictions. NIR sensors have the potential to predict N concentrations without being affected by the TS, ash content, and PS of the dairy manure.

The NMR predictions of TS, NH4-N, and TN were accurate for samples with relativley low TS, but not well correlated to the lab measurements for high TS samples. TP predicted by NMR was not affected by TS levels and the TP prediction was not precise and robust. The effects of runtime on the accuracy and precision of NMR prediction were not consistent.

Future Plans

Additional work is needed to improve the accuracy and precision of NIR calibration models. The procedure of spiking method in manure analysis using NIR techniques needs to be enhanced in order to be widely applied for preparing manure samples for NIR calibrations. Finally, further investigation of the methodology with other manure constituents such as P and K and conducting online variable rate application of organic fertilizer using NIR sensing system are needed to evaluate the potential effects of reducing the overall system variability.

Additional work to improve NMR prediction includes recalibrating the system based on specific manure samples and improving the accuracy and precision of TP prediction.

Authors

Xiaoyu Feng, Research Associate, University of Wisconsin-Madison
xfeng43@wisc.edu

Additional Authors

-Rebecca Larson, Associate Professor and Extension Specialist, University of Wisconsin-Madison; Matthew Digman, Assistant Professor, University of Wisconsin-Madison;
-Joseph Sanford, Assistant Professor, University of Wisconsin- Platteville

Additional Informaion

Feng, X.Y., R.A. Larson, and M. Digman. 2022. Evaluating the Feasibility of a Low-Field Nuclear Magnetic Resonance (NMR) Sensor for Manure Nutrient Prediction. Sensors 22(7):2438. https://doi.org/10.3390/s22072438

Feng, X.Y., R.A. Larson, and M. Digman. 2022. Evaluation of Near-Infrared Reflectance and Transflectance Sensing System for Predicting Manure Nutrients. Remote Sensing 14(4): 963. https://doi.org/10.3390/rs14040963

Acknowledgements

Support for this project was provided by the Wisconsin Dairy Innovation Hub.

 

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. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.

Vermifiltration as a Technology for Lowering Dairy Wastewater’s Nutritional and Organic-Strength

Purpose

Due to increased demand for milk and milk products, the dairy industry has grown tremendously over the last several decades. This has resulted in an increase in the production of dairy manure. In recent years, the industry has also seen significant changes, such as a decrease in the number of dairy farms but an increase in the size of individual operations, and regional concentrations of dairy operations. Because of the regional concentrations of large dairies, large volumes of manure are produced in small geographical areas, raising concerns about the effects on local air, land, and water resources. Various dairy manure management technologies have been suggested ranging from anaerobic lagoons to membrane filtration. Many of these technologies, however, are not considered economically viable due to the high energy and labor requirements for sludge management.

Vermifiltration is on the other hand an emerging low-cost manure management technology, which is an aerobic wastewater treatment system that employs a community of microorganisms and earthworms in a filter bed media. The purpose of this research was to assess the effectiveness of this technology in reducing solids, organic strength, and nutrients (nitrogen and phosphorus) in dairy wastewater from a dairy operation with a manure-flush system. The treatment’s ultimate goal was to: (1) reduce the nutrient load of the wastewater so that it could be recycled via irrigation on nearby land, (2) recycling to flush fresh manure from the barns, and (3) recover the nutrients in the form of earthworm biomass and vermicasts.

What Did We Do

In this study, we assessed the efficacy of a vermifilter for treating dairy wastewater in terms of effluent quality and potential air emission reductions. For these tests, a pilot-scale vermifilter unit (Fig 1) was installed on a commercial dairy and monitored for 6 months. Additional lab-scale (Fig 2) studies looked into the effects of earthworm density, organic loading rate, and hydraulic loading rate on the vermifilter’s performance. Total solids, total suspended solids, chemical oxygen demand, total nitrogen, total ammonia-nitrogen, nitrate-nitrogen, total phosphorus, and orthophosphate were among the wastewater parameters of interest. A closed-loop dynamic chamber method was used to measure potential gas emissions (ammonia—NH3, methane—CH4, carbon dioxide—CO2, and nitrous oxide—N2O) from these samples. Lab scale Plexiglass vermifilters were also used to study the effect of earthworm density, organic and hydraulic loading rates.

Fig 1: Layout of the pilot scale vermifilter system (IIBC tanks for storage, BIDA is the vermifiltration system)
Fig 2: Lab scale vermifilter system

What Have We Learned

We observed that reduction efficiencies of up to 90% of inlet wastewater organics, nutrients, and solids can be achieved by the vermifilter (Fig 3). These results showed that vermifiltration has a high potential for reducing the concentrations of organics, nutrients, and solids in dairy wastewater. We also noted that the vermifilter system reduced emissions of gases by 84 – 100% for NH3, 58 – 82% for CO2, and 95 – 100% for CH4. Nitrous oxide emissions were mostly undetectable. We also learned that the vermifilter system reduced the global warming potential of untreated dairy wastewater by up to 100% and demonstrated the ability to generate carbon credits while maintaining a low carbon footprint. We further learned that vermifiltration at earthworm densities of 10,000 and 15,000 earthworms m-3 is best for treating dairy wastewater in terms of organic matter, nutrients, and solids concentration removal.

Fig 3: Reduction efficiencies of organics, solids, nitrogen and phosphorus
Fig 4: Influent, effluent gas fluxes through the vermifilter system

Future Plans

To enable effective scale-up, additional studies of a full-scale vermifilter system’s techno-economic and life cycle assessment are required. The techno-economic analysis will serve as a foundation for addressing vermifiltration optimization processes, as well as determining the system’s cost implications and economic performance. The life cycle assessment, on the other hand, will reveal potential environmental impacts associated with a full-scale vermifilter system.

Vermifiltration uses a variety of microbial pathways for nutrient conversion, including aerobic and anaerobic organic matter stabilization, ammonification, nitrification, immobilization, and denitrification. These pathways are heavily reliant on the system’s dominant microbiota, which has an impact on the system’s treatment efficiency. Genomic sequencing is required to better understand the microbiota present in dairy wastewater streams and vermifilter units, as well as how the introduction of earthworms affects the microbial communities. This will allow us to optimize the treatment and thus increase the vermifilter’s efficiency.

Authors

Gilbert Miito, Post Doctoral scholar, University of Missouri
gilbertjohn.miito@wsu.edu

Additional Authors

-Pius Ndegwa, Professor, Washington State University
-Femi Alege, Post Doctoral Fellow, University of California Berkeley
-Joe Harrison, Professor, Washington State University

Additional Information

Publication: https://www.sciencedirect.com/science/article/abs/pii/S2352186421002960

Acknowledge

Biofiltro, Organix Inc, Washington State University, Washington State Department of Agriculture

 

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. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.

Phosphorus Densification and Availability From Manure-Derived Biochar

Purpose

Manure produced at livestock facilities contains plant essential nutrients, such as nitrogen and phosphorus, which is typically land applied as a fertilizer source for crops near where it is generated. However, in areas of high livestock density, due to the imbalance of nitrogen and phosphorus in manure compared to crop requirements, soil phosphorus concentrations have increased. This has resulted in soil phosphorus legacy issues throughout the Midwest, contributing to water quality issues in surrounding waterways. To reduce phosphorus application near livestock facilities, advanced manure management systems are needed to separate and concentrate manure nutrients, particularly phosphorus, to expand transport distances. In this study, we investigated converting separated anaerobically digested manure solids into biochar through pyrolysis to densify manure nutrients. In addition, we examined the availability of phosphorus from manure derived biochar in a soil incubation study to evaluate its fertilizer potential.

What Did We Do

We collected anaerobically digested manure solids from a screw press separator at a local dairy facility. Manure solids were dried and converted to biochar at two different temperatures (662°F and 932°F). The mass of the dried manure and biochar were determined and samples analyzed for total nitrogen, total phosphorus, and available phosphorus to evaluate densification of manure nutrients.

We additionally evaluated nutrient availability of manure solids and biochar in a soil incubation study. In the study manure solids and biochar were applied at equal agronomic phosphorus rates to two different soil textures (loam and sandy loam). Soils were then incubated for 182 days with samples collected and analyzed Every week for four weeks throughout the period to evaluate phosphorus release over time.

What Have We Learned

We found that converting manure solids to biochar is an effective method for reducing manure mass while retaining the original manure phosphorus content (as shown in Figure 1). However, manure derived biochar had lower available phosphorus following pyrolysis than the original separated manure solids, with the available P decreasing as the pyrolysis temperature increased.

Figure 1: Mass reduction and P content following drying and pyrolysis of manure.

During the soil incubation study, while soils with manure derived biochar application had lower available phosphorus at the start of the incubation period, within 28 days available soil phosphorus reached similar levels to those amended with separated manure solids in both soil textures. While nitrogen was applied at different rates, making comparisons difficult, there were minor changes in soil available nitrogen for manure derived biochar, suggesting no additional nitrogen availability during the incubation period.

Future Plans

We plan to further investigate manure derived biochar as a potential advanced manure processing pathway, by evaluating whether manure derived biochar can provide additional soil benefits, such as reducing nitrogen leaching when amended to agronomic soils and increasing crop yields in field studies.

Authors

Joseph R. Sanford, Assistant Professor and Wisconsin Dairy Innovation Hub Affiliate Researcher, School of Agriculture, University of Wisconsin-Platteville
sanfordj@uwplatt.edu

Additional Authors

Rebecca A. Larson, Associate Professor, Biological Systems Engineering, University of Wisconsin-Madison

Additional Information

Sanford, J., H. Aguirre-Villegas, R.A. Larson, M. Sharara, Z. Liu, & L. Schott. 2022. Biochar Production through Slow Pyrolysis of Animal Manure. University of Wisconsin-Extension, Publication No. A4192-006/AG919-06, I-01-2022.

Acknowledgements

This material is based on work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number 2017-67003-26055. Partial support was provided by the Wisconsin Dairy Innovation Hub. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or Wisconsin Dairy Innovation Hub.

 

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. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.

Manure Treatment Technology Adoption by Swine and Dairy Producers: Survey Feedback

Purpose

Sound management of manure is essential to optimize its benefits for soil health and crop production, and to minimize costs and environmental risks. Along with changes in farm scale and practices, modern farms are increasingly looking to process or treat manure to address problem areas and to take advantage of market opportunities on their operations. A variety of manure treatment technologies are available and new technologies continue to be developed for managing nutrients, solids, energy, water, and other components of manure. But, while these new treatment technologies hold potential to improve the environmental, economic, and social sustainability of livestock and poultry production, questions remain regarding producer adoption of treatment systems on their operations. To improve our understanding of decision-making processes employed when producers evaluate and adopt manure treatment technologies, the authors conducted a survey aimed at dairy and swine producers in the Midwest.

What did we do?

Two surveys were developed, one tailored to dairy producers and one for swine producers. All operation sizes and production systems were included. The surveys were administered using Qualtrics, an online survey platform. Questions asked covered manure-related practices in animal facilities, manure handling, and land application. Additional questions asked producers to prioritize their needs for manure treatment, factors influencing technology selection, current technologies being utilized, and principal barriers for adoption. Respondents were asked to select up to three critical outcomes for their farms’ manure treatment technologies, the most influential factors (or technology characteristics) for manure treatment adoption, and the main barriers for technology adoption. The authors collaborated with Nebraska Extension and with state producer associations to reach swine and dairy producers in Nebraska and other Midwest states, with the survey first launched in the fall of 2021. Magazine articles, radio programs, listservs, and social media were used to promote the surveys.

Responses were analyzed using descriptive methods. Eighteen respondents provided information to characterize seven swine farms and ten dairy operations. Swine respondents had farms in Nebraska (7), Iowa (2), and Ohio (1). For dairy, 7 of the farms were in Nebraska and 1 was in Minnesota. Swine farm systems were divided between the ones that had farrowing (farrow-to-finish and farrow-to-wean systems) and the ones without it (grow-to-finish and wean-to-finish systems) (Table 1). Respondents were asked to provide insights for their farms’ primary manure management systems. A dairy operation’s primary manure management system was defined as the one receiving manure from the lactating cows. For swine, the primary manure management system received manure from the gestation sows or the finishing herd. For both swine and dairy, secondary systems were defined as utilizing separate storage and handling facilities.

Table 1. Herd size information of dairy and swine farms represented in the survey responses.
Species and herd type Number of farms Herd size – average Herd size – range
Dairy – lactating cow herd 8 933 30 to 2,150
Swine (farrowing) – sow herd 4 2,762 250 to 7,500
Swine (finishing) – finisher herd 5* 23,600 1,200 to 70,000
Note: *One finishing farm did not share its herd size information.

What have we learned?

The dairy and swine farms demonstrated differences in manure treatment needs and consequently adopted different treatment technologies (Figures 1 and 2).

Figure 1. Farm characterization and manure management of ten swine farms.
FTF = farrow-to-finish
PSOP = partially slotted open pens
PP = pull-plugs
FTW = farrow-to-wean
ISWPSF = individual stalls w/partial slotted floor
DP = deep pits
GF-F = grow-finish or finishing
ASFB = all slotted-floor building
FL = flushing
WTF = wean-to-finish
CH = chemicals
AE = aeration
LA = lagoons
AD = anaerobic digestion
CO = composting
Figure 2. Farm characterization and manure management of eight dairy farms.
CS = corn stalks
Sd = sedimentation
DD = direct drying
Mch = mechanical
TL = treatment lagoon
Co = composting
Stt = sand settling lane or basin
AE = aeration
NS = no separation
AD = anaerobic digestion

The most-used technologies in the primary manure management system for each industry were: mechanical separation, sand settling lanes, and sedimentation basins for dairy farms; and addition of chemicals, treatment lagoons, and composting for swine operations (Figure 3).

Figure 3. Manure treatment technologies being used in primary manure management systems.

Allowing water to be reused and exporting nutrients were the primary desired outcomes of implementing manure treatment technologies for dairy and swine farms, respectively (Figure 4). Accordingly, 6 of 7 dairy farms were recycling water in their operations, while only 1 out of 10 was doing so on the swine side.

Figure 4. Primary desired outcomes of the implementation of manure treatment technologies in swine and dairy farms.

Diverse factors influenced the selection of the implemented technologies in both livestock operations. Low management demand, low maintenance, “performs best functionally” (best performance achieving the desired goals of manure treatment), and low initial cost are among the most-mentioned factors (Figure 5).

Figure 5. Factors that most influenced the selection of implemented manure treatment technologies.

Swine and dairy farmers identified initial cost, operational cost, and return on investment as the primary barriers to future technology adoption (Figure 6). Management demand was another important barrier among swine producers.

Figure 6. Barriers of highest concern when upgrading manure management systems on farms, especially through the adoption of manure treatment technology.

None of the survey respondents used membranes, electrochemical precipitation, or gasification technologies, demonstrating that cutting-edge manure treatment technologies are being more slowly adopted by regional livestock producers. The high cost and potential high management demand of these technologies could be barriers for their adoption.

Future plans

Our research work has moved into qualitative exploration. Focus groups will be held with swine and dairy producers, where they will discuss and share their manure treatment needs and desired outcomes from new treatment options. These activities will be organized online and will allow producers to share their manure management perspectives for the present and future. The results of our surveys and focus groups are being used to inform a decision-support tool being developed as part of the Management of Nutrients for Reuse  (MaNuRe) project. Our findings will also be used to help develop extension programs that meet the needs of producers for manure management in Nebraska and neighboring states.

Authors

Juan Carlos Ramos Tanchez, Graduate Research Assistant, University of Nebraska-Lincoln.

Corresponding author email address

jramostanchez2@huskers.unl.edu

Additional authors

Richard Stowell, Professor of Biological Systems Engineering, University of Nebraska-Lincoln.

Amy Schmidt, Associate Professor of Biological Systems Engineering, University of Nebraska-Lincoln.

Acknowledgements

Funding for this effort came from the USDA NIFA AFRI Water for Food Production Systems program, grant #2018-68011-28691. The authors would like to express gratitude to Dr. Teng Lim and Timothy Canter (University of Missouri), Mara Zelt, and Lindsey Witt-Swanson (University of Nebraska-Lincoln) for their relevant support to this study. We would also like to thank the staff at the Nebraska Pork Producers Association and the Nebraska State Dairy Association for their collaboration on our research.

A Workshop to Review BMPs and BATs for Control of Dust, Ammonia, and Airborne Pathogen Emissions at Commercial Poultry Facilities (Zhao)

Purpose

Poultry production is a significant source of air pollutant emissions including particulate matter (PM), ammonia (NH3), and  pathogens, which negatively impact bird health and performance, human respiratory health, food safety, and local environmental quality. Effective and economically feasible management practices and technologies to mitigate air pollutant emissions and pathogen transmission are urgently needed.

In the past decade, a variety of management practices and control technologies have been developed and preliminarily tested in commercial poultry facilities, with varying degrees of success. Technologies that have been applied for PM control include air filtration, impaction curtains, oil/water spraying, wet scrubbers, electrostatic precipitation, and electrostatic spray scrubbing. Among these, electrostatic methods and wet scrubbing achieve high removal efficiencies for both fine and coarse PM. For NH3 gas mitigation, various forms of scrubbing technologies such as trickling biofilters, acid spray scrubbers, and electrolyzed water spraying have been tested in commercial poultry facilities, alongside management practices such as feed additives and litter amendments. Acid spray scrubbers can be particularly attractive to poultry facilities since the sulfuric acid from the scrubber reacts with NH3 to create ammonium sulfate, which can be used as fertilizer to offset scrubber operating costs. A new technology using artificial floor was recently studied and demonstrated significant reduction in ammonia and PM concentrations and emissions at laying hen housing.

The avian influenza outbreak in 2014/15 and the current spread of the Highly Pathogenic Avian Influenza (HPAI) remind us that pathogen control at poultry facilities is crucial. Technologies such as electrostatic precipitators, electrostatic spray scrubbers, and electrolyzed water spraying systems have been tested to assess their capacities for airborne bacteria reduction.

The technical and economic feasibilities of these methods need to be evaluated for proper consideration by poultry producers and their stakeholders. All the above research results need to be introduced to producers for practical applications.

What Did We Do?

This workshop is organized for the researchers and Extension specialists to review the latest BMPs and BATs on control of dust, ammonia, and pathogens at poultry facilities for improved biosecurity, food safety, environmental quality, and the overall sustainability of poultry production.  We have developed the following presentations and will present them at 2022 W2W.

    1. Manure Drying Methods to Control Ammonia Emissions (Dr. Albert Heber-Professor Emeritus, Purdue University)
    2. A Spray Wet Scrubber for Recovery of Ammonia Emissions from Poultry Facilities (Dr. Lingying Zhao, Professor, Ohio State University)
    3. Electrostatic Precipitation Technologies for Dust and Pathogen Control at Poultry Layer Facilities (Dr. Lingying Zhao, Professor, The Ohio State University)
    4. Field Experiences of Large-Scale PM Mitigation (Dr. Teng Lim, Professor, University of Missouri)
    5. Mitigation of Ammonia and Particulate Matter at Cage-free Layer Housing with New Floor Substrate (Dr. Ji-Qin Ni, Professor, Purdue University)

What Have We Learned?

    1. Newly developed BMPs and BATs can improve air quality in commercial poultry facilities: Manure belt layer houses reduce ammonia emissions by removing manure from the layer houses in 1 to 7 days. Belt aeration using blower tubes is one method that has been used to dry the manure on the belt.  Drying tunnels take manure from layer houses and utilize ventilation exhaust air to further dry the manure before it enters the manure storage or compost facilities or transfers to pelletizing operations.  Manure sheds and compost facilities are ventilated with building exhaust air or fresh air to dry manure in storage.
    2. The use of acid spray scrubbing is promising, as it simultaneously mitigates and recovers ammonia emission for fertilizer. Its low contribution of backpressure on propellor fans makes it applicable on US farms. A full-scale acid spray scrubber was developed to recover ammonia emissions from commercial poultry facilities and produce nitrogen fertilizer. The scrubber performance and economic feasibility were evaluated at a commercial poultry manure composting facility that released ammonia from exhaust fans with concentrations of 66–278 ppmv and total emission rate of 96,143 kg yr−1. The scrubber achieved high NH3 removal efficiencies (71–81%) and low pressure drop (<25 Pa). Estimated water and acid losses are 0.9 and 0.04 ml m−3 air treated, respectively. Power consumption rate was between 90 and 108 kWh d−1. The scrubber effluents containing 22–36% (m/v) ammonium sulphate are comparable to commercial-grade nitrogen fertilizer. Preliminary economic analysis indicated that a break-even of one year is achievable. This study demonstrates that acid spray scrubbers can economically and effectively recover NH3 from animal facilities for fertilizer.
    3. Two types of electrostatic precipitation-based dust control technologies have been developed at the Ohio State University: the electrostatic precipitator (ESP) and the electrostatic spray scrubber (ESS). Field tests of the ESP and ESS conducted at a commercial layer facility indicated that (1) the fully optimized ESP achieved respective mean PM5, PM10, and TSP removal efficiencies of 93.6% ±5.0%, 94.0% ±5.0%, and 94.7% ±4.4% and (2) the ESS exhibited respective mean PM2.5, PM10, and TSP removal efficiencies of 90.5% ±10.0%, 91.9% ±8.2%, and 92.9% ±6.9%.  A system of 88 large ESP units to treat exhaust air from the 4-house poultry facility at the minimum required ventilation rate of 24.8 m3 s-1 would have an initial cost of $757,680 and an annual operating cost of $10,831 ($13.43 per 1,000 birds), increasing annual facility electricity consumption by 54.2%. A system of ESS units designed to treat exhaust air for six exhaust fans in each of the 4 poultry houses that operated continuously year-round for minimum ventilation, is estimated to have an initial cost of $71,280 with an annual operating cost of $21,663 for water consumption and electricity usage. The ESP is more effective, and the ESS is more economically feasible to mitigate PM at a commercial egg production facility.
    4. The field-scale measurements of PM mitigation technologies are usually time-consuming to set up and maintain, and often only limited replications can be obtained. It is important to minimize interference to the routine farm operation. The use of different PM measurements, setup and maintenance required to ensure data quality, and differences between the mitigation technologies are discussed. It is important to consider practicality of the mitigations, along with safety, and long-term use of the different technologies.
    5. A new mitigation approach, using AstroTurf ® as floor substrate, reduced indoor concentrations and emissions of ammonia and PM at cage-free aviary-style layer rooms in a recent study. Results demonstrated that the average daily mean ammonia concentration in the two AstroTurf® floor rooms (7.5 ppm) was significantly lower (p < 0.05) compared with that in the two wood shaving floor rooms (15.2 ppm) with a reduction rate of 51%. Average daily mean large particles (all particles detected above ~2.5 µm) and small particles (all particles detected below ~0.5 µm) in the two AstroTurf® floor rooms were significantly reduced (p < 0.05) by 70% (501,300 vs. 1,679,700 per ft3) and 63% (906,300 vs. 2,481,100 per ft3), respectively, compared with those in the two wood shaving floor rooms. With the controlled and consistent ventilation rates among the rooms in the study, the emissions of ammonia and PM (large and small particles) from the two AstroTurf® floor rooms had similar reduction rates.

Future Plans

More workshops to review BMPs and BATs for mitigation of air emissions and pathogen transmission in poultry facilities will be organized as new research development and findings emerge.  The workshop will target audiences of researchers, farmers, and professionals working with farmers.

Authors

Presenting authors

Lingying Zhao, Professor and Extension Specialist, The Ohio State University

Albert Heber, Professor Emeritus, Purdue University

Teng Lim, Professor, University of Missouri

Ji-Qin Ni, Professor, Purdue University

Corresponding author

Lingying Zhao, Professor and Extension Specialist, The Ohio State University

Corresponding author email address

Zhao.119@osu.edu

Additional authors

Matt Herkins, Graduate Research Associate, The Ohio State University

Albert Heber, Professor Emeritus, Purdue University

Teng Lim, Professor, University of Missouri

Ji-Qin Ni, Professor, Purdue University

Additional Information

Airquality.osu.edu

Hadlocon, L. J., A. Soboyejo, L. Y. Zhao, and H. Zhu. 2015. Statistical modeling of ammonia absorption efficiency of an acid spray scrubber using regression analysis. Biosystems Engineering 132: 88-95.

Hadlocon, L. S., R.B. Manuzon, and L. Y. Zhao. 2015. Development and evaluation of a full-scale spray scrubber for ammonia recovery and production of nitrogen fertilizer at poultry facilities. Environmental Technology 36(4): 405-416.

Hadlocon, L.J. and L.Y. Zhao. 2015. Production of ammonium sulfate fertilizer using acid spray wet scrubbers. Agricultural Engineering International: CIGR Journal. 17 (Special Issue: 18th World Congress of CIGR): 41-51.

Hadlocon, L.J., L.Y. Zhao, B. Wyslouzil, and H. Zhu. 2015. Semi-mechanistic modeling of ammonia absorption in acid spray scrubbers based on mass balances.  Biosystems Engineering 136:14-24.

Heber, A. J., T.-T. Lim, J.-Q. Ni, P. C. Tao, A.M. Schmidt, J. A. Koziel, S. J. Hoff, L.D. Jacobson, Y.H. Zhang, and G.B. Baughman. 2006. Quality-assured measurements of animal building emissions: Particulate matter concentrations. Journal of the Air & Waste Management Association. 56(12): 1642-1648.

Knight, R. M. L.Y. Zhao, and H. Zhu. 2021. Modelling and optimisation of a wire-plate ESP for mitigation of poultry PM emission using COMSOL. Biosystems Engineering 211: 35-49.

Knight, R., X. Tong, L. Zhao, R. B. Manuzon, M. J. Darr, A. J. Heber, and J. Q. Ni. 2021. Particulate matter concentrations and emission rates at two retrofitted manure-belt layer houses. Transactions of the ASABE 64(3): 829-841. (doi: 10.13031/trans.14337)

Knight, R., X. Tong, Z. Liu, S. Hong, and L.Y. Zhao. 2019. Spatial and seasonal variations of PM concentration and size distribution in manure-belt poultry layer houses. Transactions of the ASABE 62(2):415-427. doi: 10.13031/trans.12950

Lim, T. T., H. W. Sun, J.-Q. Ni, L. Zhao, C. A. Diehl, A. J. Heber, and P.-C. Tao. 2007. Field tests of a particulate impaction curtain on emissions from a high-rise layer barn. Transactions of the ASABE 50(5): 1795-1805.

Lim, T.-T., Y. Jin, Ni, J.-Q., and A. J. Heber. 2012. Field evaluation of biofilters in reducing aerial pollutant emissions from commercial finishing barn. Biosytems Engineering 112(3): 192-201.

Lim, T.-T., C. Wang, A. J. Heber, J.-Q. Ni, and L. Zhao. 2018. Effect of electrostatic precipitation on particulate matter emissions from a high-rise layer house. In Air Quality and Livestock Farming, 372 p. T. Banhazi, A. Aland, and J. Hartung, eds. Australia: CRC Press, Taylor and Francis Group.

Ni, J.-Q., A.J. Heber, M. J. Darr, T.-T. Lim, Diehl, and B. W. Bogan. 2009. Air quality monitoring and on-site computer system for livestock and poultry environment studies. Transactions of the ASABE 52(3): 937-947.

Ni, J.-Q., A. J. Heber, E. L. Cortus, T.-T. Lim, B. W. Bogan, R. H. Grant, and M. T. Boehm. 2012. Assessment of ammonia emissions from swine facilities in the U.S. – Application of knowledge from experimental research. Environmental Science & Policy 22(0): 25-35.

Ni, J.-Q., L. Chai, L. Chen, B. W. Bogan, K. Wang, E. L. Cortus, A. J. Heber, T.-T. Lim, and C. A. Diehl. 2012. Characteristics of ammonia, hydrogen sulfide, carbon dioxide, and particulate matter concentrations in high-rise and manure-belt layer hen houses. Atmospheric Environment 57(0): 165-174.

Ni, J.-Q., S. Liu, C. A. Diehl, T.-T. Lim, B. W. Bogan, L. Chen, L. Chai, K. Wang, and A. J. Heber. 2017. Emission factors and characteristics of ammonia, hydrogen sulfide, carbon dioxide, and particulate matter at two high-rise layer hen houses. Atmospheric Environment 154: 260-273. http://dx.doi.org/10.1016/j.atmosenv.2017.01.050.

Tong, X., L.Y. Zhao, A. Heber, and J. Ni. 2020.  Mechanistic modelling of ammonia emission from laying hen manure at laboratory scale. Biosystems Engineering. 192:24-41.

Tong, X., L.Y. Zhao, A. Heber, and J. Ni. 2020. Development of a farm-scale, quasi-mechanistic model to estimate ammonia emissions from commercial manure-belt layer houses. Biosystems Engineering 196, 67-87.

Tong, X., L.Y. Zhao, R. B. Manuzon, M. J. Darr, R. M. Knight, C. Wang, A. J. Heber, and J.Q. Ni. 2021. Ammonia concentrations and emissions at two commercial manure-belt layer housed with mixed tunnel and cross ventilation. Transactions of the ASABE 64(6): 2073-2087. (doi: 10.13031/trans.14634)

Tong, X., S. S. Hong., and L.Y. Zhao 2019. Development of upward airflow displacement ventilation system of manure-belt layer houses for improved indoor environment using CFD simulation. Biosystems Engineering 178:294-308.

Zhao, L.Y., L. J. S. Hadlocon, R. B. Manuzon, M.J. Darr, H. M. Keener, A. J. Heber, and J.Q. Ni. 2016. Ammonia concentrations and emission rates at a commercial manure composting facility. Biosystems Engineering  150: 69-78.

Acknowledgements

The wet scrubber development was supported by National Research Initiative Competitive Grant 2008-55112-1876 from the USDA Cooperative State Research, Education, and Extension Service Air Quality Program. The ammonia emission modelling work was supported by the USDA-NIFA Grant 2018-67019-27803.

The electrostatic precipitation-based dust control work was supported by the USDA National Institute of Food and Agriculture Grant 2016-67021-24434.

The Project funding for the Mitigation of Ammonia and Particulate Matter at Cage-free Layer Housing with New Floor Substrate presentation was provided by the U.S. Poultry & Egg Association. GrassWorx LLC provided the AstroTurf and financed the building of the flooring systems.

Appreciation is also expressed to the U.S. EPA, and participating producers and staff for their collaboration and support.

 

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