Thermal-Chemical Conversion of Animal Manures – Another Tool for the Toolbox


How Can Thermo-Chemical Technologies Assist in Nutrient Management?

Livestock operations continue to expand and concentrate in certain parts of the country. This has created regional “hot spot” areas in which excess nutrients, particularly phosphorus, are produced. This nutrient issue has resulted in water quality concerns across the country and even lead to the necessity of a “watershed diet” for the Chesapeake Bay Watershed. To help address this nutrient concern some livestock producers are looking to manure gasification and other thermo-chemical processes. There are several thermo-chemical conversion configurations, and the one chosen for a particular livestock operation is dependent on the desired application and final by-products. Through these thermo-chemical processes manure Factory processingvolumes are significantly reduced. With the nutrients being concentrated, they are more easily handled and can be transported from areas of high nutrient loads to regions of low nutrient loads at a lower cost. This practice can also help to reduce the on-farm energy costs by providing supplemental energy and/or heat. Additional benefits include pathogen destruction and odor reduction. This presentation will provide an overview of several Conservation Innovation Grants (CIG) and other manure thermo-chemical conversion projects that are being demonstrated and/or in commercial operation. Information will cover nutrient fate, emission studies, by-product applications along with some of the positives and negatives related to thermo-chemical conversion systems.

Exterior of factory processingWhat did we do? 

Several farm-scale manure-to-energy demonstration projects are underway within the Chesapeake Bay Watershed. Many of these receive funding through the USDA-NRCS Conservation Innovation Grant program. These projects, located on poultry farms, are being evaluated for the performance of on-farm thermal conversion technologies. Monitoring data is being collected for each project which includes: technical performance, operation and maintenance, air emissions, and by-product uses and potential markets. Performance of manure gasification systems for non-poultry operations have also been reviewed and evaluated. A clearinghouse website for thermal manure-to-energy processes has been developed.

What have we learned? 

The projects have shown that poultry litter can be used as a fuel source, but operation and maintenance issues can impact the performance and longevity of a thermal conversion system. These systems are still in the early stages of commercialization and modifications are likely as lessons are learned. Preliminary air emission data shows that most of the nitrogen in the poultry litter is converted to a non-reactive form. The other primary nutrients, phosphorus and potassium, are preserved in the ash or biochar co-products. Plant availability of nutrients in the ash or biochar varies between the different thermal conversion processes and ranges from 80 to 100 percent. The significant volume reduction and nutrient concentration show that thermal conversion processes can be effective in reducing water quality issues by lowering transportation and land application costs of excess manure phosphorus.

Future Plans    

Monitoring will continue for the existing demonstration projects. Based on the lessons learned, additional demonstration sites will be pursued. As more manure-to-energy systems come on-line the clearinghouse will be updated. Based on data collected, NRCS conservation practice standards will be generated or updated as necessary.

Author       

Jeffrey P. Porter, PE, Manure Management Team Leader, USDA-Natural Resources Conservation Service jeffrey.porter@gnb.usda.gov

Additional information                

Thermal manure-to-energy clearinghouse website: http://lpelc.org/thermal-manure-to-energy-systems-for-farms/

Environmental Finance Center review of financing options for on-farm manure-to-energy including cost share funding contact information in the Chesapeake Bay region: http://efc.umd.edu/assets/m2e_ft_9-11-12_edited.pdf

Sustainable Chesapeake: http://www.susches.org

Farm Pilot Project Coordination: http://www.fppcinc.org

National Fish and Wildlife Foundation, Chesapeake Bay Stewardship Fund: http://www.nfwf.org/chesapeake/Pages/home.aspx

Acknowledgements

National Fish and Wildlife Foundation, Chesapeake Bay Funders Network, Farm Pilot Project Coordination, Inc., Sustainable Chesapeake, Flintrock Farm, Mark Weaver Farm, Mark Rohrer Farm, Riverview Farm, Wayne Combustion, Enginuity Energy, Coaltec Energy, Agricultural Waste Solutions, University of Maryland Center for Environmental Science, Environmental Finance Center, Virginia Cooperative Extension, Lancaster County Conservation District, Virginia Tech Eastern Shore Agricultural Research and Extension Center, Eastern Shore Resource Conservation and Development Council, with funding from the USDA Conservation Innovation Grant Program and the U.S. EPA Innovative Nutrient and Sediment Reduction Program.

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.

User capabilities and next generation phosphorus (P) indices

Purpose

The phosphorus (P) index is the primary approach to identify field management strategies and/or manure application strategies likely to lead to excessive risk of P loss. It has been over 40 years since the first research connecting agronomic P management and water quality and over 20 years since the initial publication defining a P Index. This session will consider opportunities to build on and expand existing P Index strategies to make them more effective at protecting water quality and friendlier to the target user.

What did we do?

Nutrient management is a process providing guidance on the rate, source, timing, and method of nutrient applications. After completing an initial one to five year strategic plan there are tactical adjustments for new information such as new soil and manure tests and changes in crop selection. Additional assessments are needed when implementing the plan such as determining if current weather and soil conditions are appropriate for application.

We initially reviewed current P Indices and the skills needed to implement those P Indices. We then considered how those requirements aligned with the likely users of the P Index at a particular steps in the development and implementation of a nutrient management of plan.

What have we learned?

Many current P Indices require using the soil erosion program RUSLE2 which is then a barrier to the use of these P Indices by anyone except planners with specialized planning. Such expertise is never available on some farms and unlikely to be available on most farms during tactical and implementation phases of the plan. There has also been suggestions that more complex strategies such as models should replace existing P Indices; this will lead to more complex P loss assessment tools.

Next generation P Indices will be more effective if we consider the capabilities and training of those likely to be making decisions at each critical juncture. Instead of “the” P Index we need to design a suite of tools that target key decision points. At each decision point, a first step of the development process must be defining who the likely decision maker is and what are their skills and training. We can only succeed if our tools are accessible to those that need to use them.

Future Plans  

Sessions like this one and regional efforts to evaluate and update P Indices are critical to the continued improvement of state P Indices. We all must recognize that the P Index concept is still relatively young; in comparison it took about a century to move from the first research on agronomic soil testing to our current soil test extraction methods and interpretation. We are still early in our journey to identify and implement the most effective tools to minimize P loss from agricultural fields.

Authors  

Dr. John A. Lory, Associate Professor of Extension, University of Missouri, Columbia, MO loryj@missouri.edu

Dr. Nathan Nelson, Associate Professor, Kansas State University, Manhattan, KS

Additional information            

Please contact the authors for more information about this topic.

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.

 

Variation in state-based manure nitrogen availability approaches

The phosphorus (P) index is the primary strategy used in nutrient management planning to identify field management strategies and/or manure application strategies likely to lead to excessive risk of P loss.  Current P Indices were developed primarily as strategic planning tools guiding the development of a nutrient management plan spanning one to five years.  In reality, a nutrient management plan should be viewed more as a process than a result.  After completing the initial strategic plan there are tactical adjustments for new information such as new soil and manure tests and changes in crop selection.  Additional assessments are needed when implementing the plan, determining if current weather and soil conditions are appropriate for application.  Many current P Indices require using the soil erosion program RUSLE2 which is then a barrier to the use of these P Indices by anyone except planners with specialized planning.  Such expertise is never available on some farms and unlikely to be available on most farms during tactical and implement phases of the plan.  There has also been suggestions that more complex strategies such as models should replace existing P Indices; this will lead to more complex P loss assessment tools.  Next generation P Indices will be more effective if we consider the capabilities and training of those likely to be making decisions at each critical juncture.  Instead of “the” P Index we need to design a suite of tools that target key decision points.  In each instance a first step of the development process must be defining who the likely decision maker is and what are their skills and training.  We can only succeed if our tools are accessible to those that need to use them.

Purpose      

Extensive research has documented fertilizer value of manure nutrients for crops. It has been long recognized that manure nitrogen (N) excreted by animals is not 100% available to crops. Surveys indicate failure to credit or under crediting manure nutrient value to a crop by farmers continues to be an issue. Our goal was to assess the current state of manure nutrient availability recommendations and requirements in the US.

What did we do?

We surveyed state recommendations for state nutrient availability calculations for four sources of manure: finish hog slurry, dairy cow slurry, solid cattle manure and broiler litter. The top 12 states for production of each associated commodity were determined using inventory data from the 2012 Agricultural Census; the top 12 states for production were states we surveyed for each manure type. For each state and each manure type surveyed we attempted to identify nitrogen availability calculation recommendations from three sources: the State Land Grant University, the state USDA Natural Resource Conservation Service (NRCS) standards and supporting documents, and the state regulatory documentation for operations with a National Pollution Discharge and Elimination System (NPDES) permit.

What have we learned?

We were able to identify a primary publication or publications published by the State Land Grant University in all but four of the 30 surveyed states for the manure types of interest. Median date of publication for the 22 dated publications was 2006 (range 1991-2014). The NRCS documentation referenced the state Land Grant publication (10 states), a state-specific NRCS worksheet or reported numbers in the standard (7 states) or referred to regional or national reference (3 states). The USEPA NPDES regulatory documentation did not specify availability coefficients in 11 of 30 states. In nine states the regulatory documentation cited the USDA-NRCS 590 standard but in three of those states the NRCS standard did not provide nutrient availability coefficients. Consequently it was not possible to determine regulatory nutrient availability coefficients in nearly half of the surveyed states (14 of 30). Availability calculation approaches fell into two main categories, states that calculate availability based on manure total nitrogen content and states that account separately for availability of organic and ammonium nitrogen. Availability estimates among states were more variable for strategies known to be more variable (e.g. surface application of liquid manure).

Future Plans

Our work emphasizes the varied approach to N availability calculations as we cross state borders. We hope this publication will encourage regional discussions among states with similar climate to work towards more consistent recommendations. More consistent recommendations may help farmers have more confidence in those recommendations,

Our work also demonstrates how difficult it can be to identify the appropriate calculations within a given state. We encourage that state recommendations from all three organizations (Land Grant, NRCS, regulatory) be documented in a standard place in the state NRCS Nutrient Management Standard so planners, farmers, and people developing and managing nutrient management tools can easily and with confidence access the most current information on N availability information for manure nutrients.

Authors    

Dr. John A. Lory, Associate Professor of Extension, University of Missouri, Columbia, MO loryj@missouri.edu

Ms. Caitlin Conover, USEPA and Visiting Scholar, University of Missouri, Columbia, MO

Additional information         

Please contact the first author for more information.

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.

Estimation of phosphorus loss from agricultural land in the Heartland region using the APEX model: a first step to evaluating phosphorus indices

Purpose

Phosphorus (P) indices are a key tool to minimize P loss from agricultural fields but there is insufficient water quality data to fully test them. Our goal is to use the Agricultural Policy/Environmental eXtender Model (APEX), calibrated with existing edge-of-field runoff data, to refine P indices and demonstrate their utility as a field assessment tool capable of protecting water quality. In this phase of the project our goal is to use existing small-watershed data from the Heartland Region (IA, KS, MO and NE) to determine the level of calibration needed for APEX before using the model to generate estimates of P loads appropriate for evaluating a P Index.

What did we do?

APEX model is designed to simulate edge-of-field water, sediment, and nutrient losses. Our analysis included data from 19 watersheds at four sites in the Heartland Region representing a range of hydrologic conditions and including grazing, tilled row-crop, and no-till row-crop management systems.

We evaluated two strategies to optimize settings of model parameters: i. a watershed-specific parameterization based on full calibration/validation comparing measured data with simulated results of the model for runoff volume, sediment load and P load, ii. a minimal parameterization approach based on best professional judgment (BPJ) consistent with using APEX when measured runoff, sediment and P data are not available for model calibration. Model fitting for strategy (i) was done using event data in each watershed. The two parameterization strategies were evaluated based on the fit of “annual” totals where data at each location were summed by year (total of 97 site-years). The Nash-Sutcliffe model efficiency and regression methods were used to quantify model fit.

Figure 1. Examples of small watershed studies that generated runoff water quality used to assess APEX calibration strategies: a.Kansas; b. Missouri.

What have we learned?

Full calibration provided excellent fit for runoff and total P (NSE>0.8 for each) and marginal fit for sediment (~0.3). In contrast, the BPJ resulted in unacceptable estimates of sediment and P load, and marginal fit for runoff volume (NSE~0.4). These results emphasize that failure to calibrate APEX with runoff and water quality data (the BPJ approach) will result in poor estimates of annual sediment and total P loads.

Future Plans      

We are testing a regional parameterization strategy as another possible way to extend the APEX model to locations where there is no runoff and water quality data. The next phase of this project will then use appropriately calibrated models to generate the long-term estimates of P loss needed to evaluate P indices in IA, KS, MO and NE.

Authors

Dr. John A. Lory, Associate Professor of Extension, University of Missouri, Columbia, MO loryj@missouri.edu 

Dr. Nathan Nelson, Associate Professor, Kansas State University, Manhattan, KS

Dr. Claire Baffaut, Research Hydrologist, USDA Agricultural Research Service, Columbia, MO

Dr. Anomaa Senaviratne, Post-doctoral Researcher, University of Missouri, Columbia, MO

Dr. Mike Van Liew, Watershed Modeling Specialist, University of Nebraska, Lincoln, NE

Ammar Bhandari, Doctoral Candidate, Kansas State University, Manhattan, KS

Dr. Antonio Mallarino, Professor, Iowa State University, Ames, IA

Dr. Matt Helmers, Professor, Iowa State University, Ames, IA

Dr. Ranjith Udawatta, Associate Research Professor, University of Missouri, Columbia, MO

Dr. Dan Sweeney, Professor, SE Agricultural Research Center, Kansas State University, Parsons, KS

Dr. Charles Wortmann, Professor, University of Nebraska, Lincoln, NE

Additional information 

Please contact the authors for more information about this project.

Acknowledgements      

This project is funded, in part, by a USDA-NRCS Conservation Innovation Grant.

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.

Nutrient Management Planners’ Feedback on New York and Pennsylvania Phosphorus Indices

Purpose 

The Phosphorus Index (PI) estimates the relative risk of P loss from agricultural fields and encourages the implementation of best management practices to reduce this risk. A majority of states designed their own PI version to address local conditions and priorities, resulting in a large variation in PI structures among states. Currently, multiple projects nationwide are evaluating if the different PIs are directionally and magnitudinally correct in ranking fields based in their potential for P loss. In the Chesapeake Bay, New York (NY), Pennsylvania (PA), Delaware (DE), Maryland (MD), Virginia (VA), and West Virginia (WV) are working cooperatively to fulfill this objective. Several approaches have been proposed to determine the effectiveness of the various PIs. The following results summarize one approach: a survey of certified nutrient management (CNMP) planners with questions specifically related to their perspectives on the NY and PA PIs. This approach recognizes that planners have experience with the PI and have a close knowledge of the landscape scenarios and management that have previously resulted in water quality violations.

What did we do? 

A total of 36 CNMP planners were surveyed in NY in the winter of 2013-2014. The survey included questions about (1) the relative importance of the different factors in the current PI; (2) the main reasons for water-quality violations; (3) the management practices the PI should encourage and discourage, (4) the use of a screening tool to identify fields that need and do not need a PI assessment; and (5) the PI assessment across and within geographic regions.

In PA, a survey structure and question content similar to NY was used to ensure comparability of results. Certified private and public nutrient management (NM) specialists as well as other members of the PA NM community received the survey in the spring of 2014.

What have we learned? 

All source and transport factors included in the NY PI were considered important by the CNMP planners. More than half of the planners indicated that the water quality violations were mainly driven by manure applications (1) just before snow melt or rainfall events, (2) on frozen or saturated soils, (3) too close to streams or ditches, or (4) without incorporation. Many nutrient management planners suggested that the PI should incentivize manure incorporation, implementation of cover crops, setbacks and buffers, and preferential manure applications to fields without connectivity. A high percentage of planners also suggested that the PI should discourage manure applications to saturated or frozen soils, to fields close to streams, to fields with steep slopes, manure spreading without incorporation, and high manure rates. Several CNMP planners in NY indicated the weighting of factors in the NY PI should be reevaluated, in particular, the timing of manure application. Some planners proposed to use real weather data to fine-tune the timing of manure application, while others suggested replacing the calendar year as a driver for PI weights by field conditions. Most of the CNMP planners in NY (1) did not support including a screening tool to quickly identify fields of no P runoff risk in the revised PI,(2) supported a physiographic-based PI (NY plus Northern PA), and (3) did not support multiple PIs within the NY. Some planners also raised concerns about the lack of systematic assessment of water quality, and the attempt to numerically predict P loss as opposed to predict the relative risk of P applications.

Overall, responding NM specialists indicated a need to revise the PA PI and favored the continued use of a screening tool. State boundary was the preferred regional basis for revising and implementing the PA PI, but some respondents showed support for using physiographic region. Current, PA PI source and transport factors were considered important and reliable in assessing fields for vulnerability to P loss. However, many NM Specialists recognized other potential PA PI factors such as flooding frequency, concentrated flow, leaching potential, and degree of soil P saturation as important for consideration in revising the PA PI. Based on their experience, respondents reported water quality violations typically resulted from manure spills, manure discharge events, and erosions events. Management practices to be encouraged by the PA PI include buffers, cover crops, and erosion control practices such as no tillage. In turn, management practices to be discouraged by the PA PI include winter manure application and manure application to land without suitable cover.

Future Plans 

The management practices identified by CNMP planners will be evaluated in the revised version of the NY PI.

The information obtained from the PA survey will be considered in the PA PI revision process. Similarities in responses between PA and NY especially with respect to practices to be encouraged or discouraged by the PI demonstrate the need for continued cooperative regional work and PI evaluation.

Authors

Quirine M. Ketterings, Professor, Cornell University qmk2@cornell.edu

Sebastian Cela, Postdoctoral Associate Cornell Univ.,Karl J. Czymmek, Senior Extension Associate Cornell Univ., Jennifer Weld, Graduate Student Penn State, Douglas Beegle, Distinguished Professor Penn State, Peter Kleinman, Research Leader USDA-ARS PSWMRU

Additional information 

For additional information, contact Quirine M. Kettertings at qmk2@cornell.edu

Acknowledgements

This project is funded by a USDA-NRCS CIG Grant.

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.

Anaerobic Digestion Projects: Environmental Credits 101

Several renewable natural gas (RNG) projects are either recently completed or on the books as potential new projects. With such a new business model, Washington State University, in concert with State officials embarked on a feasibility study to investigate costs/revenues as well as project consideration, hurdles and options for production of RNG as compared to an industry standard combined heat and power (CHP) model. The feasibility study was for an existing dairy anaerobic digestion project located near the Yakima Valley of Washington State.  

What Are Some of the Benefits of Anaerobic Digestion?

One of the major advantages of anaerobic digestion (AD) is the environmental benefits that accompany the technology. AD systems mitigate greenhouse gas (GHG) emissions, can contribute to reducing nutrient export from dairies to surface and ground water, can reduce the risk of pathogen spread, and can improve air quality. In the field of economics, many of these types of environmental benefits and harms fall into the realm of market externalities. Externalities are outputs of a production process that are “external” to the producers’ decision-making process, such as methane emitted from a manure lagoon. A common way governments have attempted to reduce harmful environmental externalities is through emissions regulations. An alternative way to mitigate negative externalities that we have seen in recent years has been the formation of markets for environmental attributes. This induces producers to internalize the environmental costs and benefits of production. Existing environmental markets contribute revenue gains to AD adopters, and with further development have the potential to result in even larger revenue gains for AD projects.

What did we do?

We explored available and potential environmental credits that could be available to AD projects and classified them by environmental attribute. These include carbon credits, renewable energy / fuel credits, tax and utility credits, and nutrient credits. We present examples of types of these environmental credits and their impacts on AD project profitability under various scenarios. We further discuss questions of eligibility and considerations for project developers and managers in the context of positioning for future environmental credit opportunities.

Table 1: Available sources of environmental revenues for anaerobic digester owners based on combined heat and power (CHP) or compressed natural gas (CNG) generation.

AD Methane Use Environmental Credit Market Price Yearly Revenue $/Head Market Price Yearly Revenue $/Head Market Price Yearly Revenue $/Head
    Low Scenario Medium Scenario High Scenario
Combined Heat & Power Carbon Credit $10/tCO2e $42.13 $15/tCO2e $63.19 $20/tCO2e $84.25
REC $2.00/MWh $3.08 $4/MWh $6.16 $8/MWh $12.32
Compressed Natural Gas Carbon Credit $10/tCO2e $42.13 $15/tCO2e $63.19 $20/tCO2e $84.25
RIN $0.005/Mbtu $158.34 $0.01/Mbtu $316.68 $0.02/Mbtu $633.36
LCFS $12/tCO2e $380.02 $24/tCO2e $760.04 $48/tCO2e $1,520.07

What have we learned?

Environmental crediting options are highly variable both in terms of the types and mechanisms for the credit and their availability across space (jurisdiction) and time. History indicates there is likely to be continued variability and limited predictability for environmental crediting. Economic analyses show that AD projects can be profitable under many different scenarios, but is most sustainable when it allows for multiple revenues from electricity or renewable fuel, fiber products, nutrients, and carbon credits for avoided methane emissions. Environmental incentives like carbon credits and RFS credits (i.e., RIN) have a significant contribution to the profitability of an AD project, particularly when the project produces renewable natural gas.

Products AD-Combined heat and power (CHP) AD-Boiler AD-Renewable natural gas

Table 2: Net present values of alternative anaerobic digester (AD) systems given different revenue streams.

Energy1 -$2.1 million NA -$4.8 million
Energy, and fiber and nutrients $4.8 million $1.3 million $1.5 million
Energy, fiber and nutrients and environmental incentives2 $8.0 million $3.6 million $4.1 million
Note: NA – means not applicable for AD-Boiler Project because it does not produce electricity.
1Energy refers to electricity produced by the AD-CHP and AD-Boiler Projects, and electricity and renewable natural gas produced by the AD-RNG Project.
2Environmental incentives include the: Washington Energy Initiative, Renewable Energy Certificates, and carbon credits.

Future Plans

We will be publishing a Fact Sheet through WSU Extension providing more detailed discussion of environmental credits for AD projects. This fact sheet is part of an Anaerobic Digestion Systems Manual under development with support from USDA NIFA.

Authors

Chad Kruger, Director, WSU CSANR cekruger@wsu.edu

Greg Astill, Graduate Student WSU Econ; Suzette Galinato, Research Associate, WSU IMPACT Center; Craig Frear, Assistant Professor, WSU Biological Systems Engineering; Georgine Yorgey, Associate in Research, WSU CSANR; Jim Jensen

Additional information

Coppedge, B., G. Coppedge, D. Evans, J. Jensen, E. Kanoa, K. Scanlan, B. Scanlan, P. Weisberg and C. Frear. 2012. Renewable Natural Gas and Nutrient Recovery Feasibility for DeRuyter Dairy: An Anaerobic Digester Case Study for Alternative Off-take Markets and Remediation of Nutrient Loading Concerns within the Region. A Report to Washington State Department of Commerce. <http://csanr.wsu.edu/publications/deRuyterFeasibilityStudy.pdf>.

Galinatto, S.P., C.E. Kruger, and C.S. Frear (2015). Anaerobic Digester Project and System Modifications: An Economic Analysis. WSU Extension Publications EM090

Acknowledgements

The preparation of this fact sheet was funded by the WSU ARC Biomass Research Program, and USDA National Institute of Food and Agriculture Award #2012-6800219814.

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.

Composting and the Benefits: Achieving Practice Change through Education to Reduce Nutrient Loads and Increase Adoption of Best Management Practices

Purpose

Florida houses roughly 500,000 horses and is also home to 700 freshwater springs; Marion County is, “Horse Capital of the World” and houses two first magnitude springs and each is currently in a restoration plan with the Florida Department Environmental Protection Agency (FDEP). The Florida Department of Agriculture and Consumer Services (FDACS) equine Best Management Practices (BMP) Manual recommends composting as an excellent manure management option.

Composting is a controlled biological process that decomposes and heats up organic material to produce a biologically stable humus, which can then be used as a rich soil amendment. Composting provides protection to the ground and surface waters by preventing excess nutrients from being leached out and running-off into the waters. It destroys up to 90% of weed seeds contained in manure and kills parasite eggs and pathogens. Additionally, the organic matter/compost helps prevent and control soil erosion and can improve both soil quality and productivity.

Compost Bin SetupWhat did we do?

Individual and group programming has been developed to educate farm owners and managers about the benefits derived from composting horse manure/spent bedding. Since 2007, Over 800 farms have been seen in the county. In 2013 alone, 132 participants were involved in individual farm consultations or farm revisits, group presentations and composting workshops. Education was provided and supplemental materials were developed for clientele about composting manure, compost bin construction and composting’s soil-improvement capabilities. Compost Countryside

What have we learned?

Pre and post-test results showed a 62% (82 of 132 total participants) knowledge gain from information taught. A total of 71% (n=12 of 17 farm revisit consultations) of farms revisited improved and adopted recommended manure handling practices after receiving education. Additionally, seven farms and facilities have begun cost-share planning with Southwest Florida Water Management District (SWFWMD) for compost bin construction. Results/impacts show improved management practices and a greater understanding of BMPs, allowing for a decrease in nutrient levels to the ground and surface waters. Pictures show sample bins which were constructed as a result of individual and group programming.

an example of a concrete manure storage areaFuture Plans

Continued group and individual programming needs to be continued, in partnership with trade journal articles being written about manure management, protection of the ground and surface waters and the benefits derived from composting manure/bedding. Cost-share dollars, coming from state organizations, will further incentivize farms to construct and use compost facilities as part of a regular manure management plan.

example of lattice compost storage areaAuthor

Jamie Cohen, Farm Outreach Coordinator, UF/IFAS Extension Marion County jamiecohen@ufl.edu

Additional information

My eXtension.org Manure Management Strategies Webcast:  https://connect.msu.edu/p8yko9zhhoq/?launcher=false&fcsContent=true&pbMode=normal

eXtension.org –Manure Management page:  https://lpelc.org/horse-manure-management/

A Guide to Composting Horse Manure:  www.whatcom.wsu.edu/ag/compost/horsecompost.htm

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.

Economical Anaerobic Digestion of CAFO Animal Waste


Purpose

The application of manure on croplands is increasingly under regulatory scrutiny, especially from impaired watersheds. The challenge facing many small farms is to find cost-effective and innovative solutions for manure reuse whilst responding to environmental, regulatory and public concerns. One option is to install an anaerobic digester (AD) in which microorganisms break down biodegradable material in the absence of oxygen. However, not all farmers are financially able to install an AD but do need the AD’s benefits to keep their livestock operation sustainable. This paper discusses a novel, cost effective and patented manure treatment system which can reduce the volume of manure for field application (see Figure 1).Earthmentor N2RTS Schematic

What did we do?

The EarthMentor® Natural Nutrient Reclamation and Treatment System (EMS), uses a combination of innovative sand separation technology (if necessary) and anaerobic treatment to concentrate manure nutrients into solid phases and treat approximately 70% of manure liquids into a product which can be applied to active cropland as low-nutrient liquid using irrigation methods. The primary economic advantage of using an EMS to treat livestock manure prior to land application is lower total manure disposal costs. The total manure handling costs are reduced because up to 75 % of the original manure volume can be handled as low-nutrient value irrigation quality liquid in bulk instead of hauling it by tanker for land application. This fact alone reduces total manure handling costs by over 50 %. Other tangible benefits of using an EMS include low odor, minimized environmental risks, and greater flexibility in proper land application of the treated manure. It can be installed at farms with as few as 250 cows. Depending on farm size, operators can realize a return on investment in as little as three years. Compared to a traditional AD installed to generate biogas the EMS is simple to operate, requires less energy, requires no chemicals or substrates to treat the waste, and reduces manure disposal costs.

The EMS involves six major steps: 1) collection of raw manure and transport to the processing center, 2) sand bedding is separated from the manure stream, 3) coarse manure components are removed from the liquid manure stream, 4) additional settling of the fine manure solids and sand particles occurs in a settling basin to a concentration of 8 to 10 percent solids, 5) AD treatment of the liquid manure and dissolved solids occurs in anaerobic treatment lagoon (ATL), and 6) The ATL effluent is stored in a Storage Pond for eventual discharge to active growing crops; additional natural treatment of the liquid manure occurs while in the Storage Pond.

All settling basins and ATL lagoon must meet state guidelines, such as Natural Resource Conservation Service technical guidelines or state requirements for waste storage facilities.

The ALT of the EMS system has a smaller footprint compared to traditional ALTs (primarily use in the south and western United States) because the majority of the nutrient-rich semi-solids are removed from the manure before discharge to the ATL. Due to this major operational change the EMS is economical to install and operate even in the northern climates of the United States where many of the top producing dairy states are located. While many facilities separate solids before land application, the EMS is different because is adds the AD step which converts the manure into a low-nutrient liquid capable of irrigation-style land disposal.  The method of solid separation can be as simple as a sloped screen followed by additional gravity separation as described in Step 4 above. The EMS ATL must be sized to account for reduced biodegradation during the colder weather. The EMS has successfully operated at multiple swine facilities and several Midwestern dairy farms.

If there is sufficient land near the farmstead, the EMS can be installed at existing dairies with minimum difficulty since the treatment system works equally well with multiple bedding materials and varying manure collection methods. Another benefit of the EMS is that is allows application on fields that may be high in phosphorus since much of the phosphorus will be stored in the accumulating ATL sludge. For dairies bedding with sand, a patented sand removal system can be provided that relies on a decanting method of sand separation. Once the sand is removed, it can be reused in the barn. 

What have we learned?

Typical Cost Savings for Manure Application Using EMS
Component
Disposal Method
Conventional Manure Handling
EarthMentor® Treatment System Handling
Liquid Manure

 

Land Application 100% $0.02/gallon 0% $0
Separated Solids Land Application 0% $0 10% $0.016/gallon
($4/ton equiv.)
Heavy Slurry Land Application 0% $0 20% $0.02/gallon
Treated Wastewater Center Pivot over Crop 0% $0 70% $0.002/gallon
Combined Cost   100% $0.02/gallon 100% $0.007/gallon
(weighted average of all components)

Using financial data from 2010 for a 2,000-cow Michigan dairy, it was estimated that the cost to handle manure using an EMS is reduced from $0.02/gallon to $0.007/gallon. The cost saving using the EMS is based on the assumption that the average dairy cow produces nearly 25 gallons/day of manure, including wastewater but excludes bedding since farms used different types and volumes of bedding for their dry and lactating cows. Based on the financial analysis, installation of an EMS benefits the farm’s economic sustainability while providing other benefits including reduced environment risk associated with manure land application.

Far beyond the obvious cost savings associated with the EMS installation, a livestock producer will realize many other benefits. A partial list is provided below:

  • This practical and manageable manure treatment system requires little or no additional farm labor commitments yet greatly reduces overhead expenditures to keep the farm sustainable and competitive,
  • All manure is treated prior to land application (environmentally sound),
  • The more consistent high solids slurry can be precisely applied to fields with the greatest need as opposed to the highly variable manure nutrient concentrations recovered from a traditional manure pond,
  • Minimizes the environmental risks (ecologically viable) and farm nuisance potential,
  • The window of opportunity for manure application is extended to over 200 days instead of being limited to spring and fall applications for typical liquid manure,
  • Can provide a safe unlimited recycled bedding source for cattle, if so desired, by the dairy owner,
  • Permits farmer to follow BMPs for soil conservation,
  • Permits farmer to follow timing, rate, source, and place for fertilizer/crop nutrient applications,
  • Benefits the non-farm neighbors and community through reduced nuisance odors, and
  • Continues using the farm’s manure as a soil amendment for crop production, the most efficient use known.

Future Plans

The immediate future plans for EMS is to target small livestock producers, especially those within impaired watersheds.  Since many ADs need a substrate material imported from outside the farm to be economically sustainable, the EMS is ideal for those farms that want to be good neighbors with reduced farm air emissions, need greater convenience in manure management, and desire to maximize the real cash value of their manure.

As the EMS adapts well to any bedding material, by investing time and dedicating property for the ATL any size operation can begin to treat their manure prior to land application and reduce their overall cost for manure management.

In addition to small farms we envision four possible adaptations of EMS; these examples are provided to show the transferability of this technology to farms desiring various outcomes from an EMS:

  1. Installation of an Energy-Generating AD – if a farm wishes to generate energy using a traditional AD, it would be installed prior to the EMS system whereby the AD digestate discharges into the settling ponds. Since the residence time of a traditional AD is measured in days, there is a great deal of additional treatment that can occur so that the cost savings for land application can still be realized.
  2. Use manure solids for other uses besides land application – if the livestock producer decides to bed their cattle on manure solids or to compost the manure solids for sale off-farm to landscapers or bag and sell direction from the farm then the solids from the SS can be further treated with a screw press or roller then composting by various means.
  3. Greenhouse gas capture and sale of carbon credits – a geosynthetic liner cover can be added to the ATL and all captured gases burned through a flare. However, it should be noted that by removing a significant amount of high organic solids during the initial fiber solids separation step, much less organic material is subject to organic degradation into methane gas.
  4. Greenhouse gas capture and burning of the gases – to generate electricity or heat water (typically for on-farm use or export to an adjoining business, such as a greenhouse).

One future issue to resolve includes educating state governments on the benefits of installing an EMS, especially for those farms that may be under a Consent Order or other regulatory actions or those farms that may need to implement a manure treatment system to mitigate odors from the livestock operation.  The duration to install an EMS and get it operational is much shorter than the lead time to design and install a traditional AD so the EMS can help when farms need to implement changes quickly.  A second issue to overcome is to properly educate producers on the benefits of EMS and differences between traditional ADs.  Swine, beef, and dairy producers who already have a farm irrigation system will have a lower capital investment to begin achieving the reduced manure management costs referenced above.

Author

Matthew J. Germane, P.E., President at Germane Environmental Consulting, LLC MGermane@GECEnvironmental.net

Additional information

https://www.gecenvironmental.com, Envirolytic Technologies, LLC

Acknowledgements

Acknowledgements to Envirolytic Technologies, LLC, Greenville, OH manufacturer of the Earthmentor® N2RTS system and RAM Technologies, LLC, manufacturer of the sand separation equipment used in the EMS for their assistance in providing the laboratory data used in this paper.

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.

Fertilizer Value of Swine Manure: A Comparison of a Lagoon and a Deep Pit Slurry System

Why Compare Liquid and Slurry Systems for Pig Production?

Since 2000 the cost of fertilizer has more than doubled. According to information provided by the USDA Economic Research Service (2013), the national average price per pound of N has increased between 2000 and 2012 by a factor of 2.6. Over the same time period, phosphate price increased by a factor of 2.8, and potassium price increased by a factor of 4.0. As a result, fertilizer costs now contribute 30% to 40% of the annual variable costs to grow many cereal grains. Table 1. Fertilizer priceDuring the same time period environmental regulations have greatly decreased the construction of swine finishing facilities that use liquid manure handling systems that require the use of a lagoon or storage pond. In response to these economic and regulatory realities, some swine production companies are considering the use of deep pit slurry systems instead of an outdoor lagoon or storage. Benefits of the deep pit slurry system include the exclusion of rainfall, reduction in storage visibility, and conservation of valuable major plant nutrients (N, P, K) for the purpose of reducing production costs for feed grains. The objective of this presentation is to compare the fertilizer value of the manure produced from swine finishing barns that use a liquid manure handling with a treatment lagoon, and swine finishing barns that store manure below slotted floors in pits.

Table 2. Fertilizer priceWhat did we do?

Plant nutrient content and volume data were collected from a swine finishing farm that used a lagoon treatment system. The system was designed to provide storage of manure, anaerobic treatment of volatile solids, and storage for sludge for 3520 pigs. Treated lagoon surface water (total solids = 0.5%) was recycled through the four buildings to provide water to remove manure from the building using a pull-plug, pit-recharge design. Lagoon surface water was applied to nearby cropland annually to provide all major plant nutrients using traveling gun irrigation. Data were also collected concerning the plant nutrient content of lagoon sludge, and sludge volumes were estimated using the ASABE Standard (2011).

Image of barnThe realized value of swine manure was calculated for using lagoon water, and sludge to provide all or a portion of the N, P2O5, K2O used by corn based on typical crop needs. Only the portion of plant nutrients that met the recommendations was assigned value. No value was assigned to major plant nutrients applied in excess of plant uptake. The value was assigned based on price data obtained from USDA-ERS (2013). The prices used were $0.71/lb of N, $0.69/lb of P2O5, and $0.50/lb of K2O.

Two application rates were calculated for lagoon water. The first rate was to provide the N needs for corn and the second was to provide the P2O5 needs of the crop. The pounds of N, P2O5, and K2O applied per acre were determined and the value of the nutrients that met the fertilization rates was calculated.

Lagoon sludge (total solids = 10%) contained 4 times as much P2O5 as plant available N (PAN) per 1000 gallons (47.3 lb P2O5/1,000 gal vs 11.7 lb PAN/1,000 gal). Therefore, the only sludge application rate used was the rate needed to meet the fertilizer recommendation for P2O5. The realized value of the sludge was determined in the same way as for lagoon water.

Diagram lagoon system for finishing swineWhen lagoon water was applied to supply the N needs of one field, and sludge was applied to meet the P2O5 needs of another field the realized value of swine manure was $5.69 per hog-space per year. Application of lagoon water and sludge to meet the P2O5 needs of corn increased the annual value of manure to $6.64 per hog-space.

The analysis was repeated for the same size farm using volume and nutrient data for deep pit barns that provided 1 year of storage for swine slurry (total solids = 7.5%). The realized economic value of deep pit slurry was also calculated based on application of slurry, using direct injection, to meet the N and P2O5 needs of corn with the same price assumptions as for the lagoon system. The results indicated that spreading deep pit slurry based on the agronomic rate for N provided a realized manure value of $24.35/hog-space/yr. Application of slurry based on the agronomic rate for P2O5 yielded a manure value of $28.95/hog-space/year.

What have we learned?

Treatment lagoons were originally designed to provide treated water used to remove manure from flush or pit-recharge swine buildings. However, little consideration was given to the value of the N lost or the value of P and K. Essentially, lagoons provided the treatment needed for recycled flush or pit-recharge systems, but they wasted nitrogen that could be used to off-set fertilizer costs.

Over the last decade, fertilizer prices have increased greatly, and continue to fluctuate. As a result, the nutrients lost by manure treatment are now viewed as a valuable input for production of feed grains.

Using a deep pit barn eliminated the need for manure treatment and allowed plant nutrients to be stored until needed. It was estimated that a deep pit slurry system would allow a producer to increase nutrient value per hog-space by a factor of 4.3 from $6.68 to $28.95/hog-space per year. On a 4-house farm that provided housing for 3520 hogs the annual manure value may be as high as $101,920 per year.

Future Plans

The results from this study are being used to develop extension programs for swine producers. Information is being used to help plan farms and to encourage integration of swine and feed grain production.

Author

John P. Chastain, Ph.D., Professor and Extension Agricultural Engineer, Clemson University jchstn@clemson.edu

Additional information

Reference Cited

ASABE (2011). ANSI/ASAE EP403.4 FEB2011 Design of Anaerobic Lagooons for Animal Waste Management. In ASABE STANDARDS. ASABE, 2950 Niles Rd., St. Joseph, MI 49085-9659.

USDA-ERS (2013). Fertilizer Use and Price. United States Department of Agriculture, Economic Research Service. Available at: http://www.ers.usda.gov/data-products/fertilizer-use-and-price.aspx.

Acknowledgements

Support for this work was provided by the Confined Animal Manure Management Program of Clemson Extension, Clemson University, Clemson, SC.

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.

 

 

 

Plant Nutrient and Carbon Content of Equine Manure as Influenced by Stall Management and Implications for Nutrient Management


Purpose 

South Carolina’s equine industry is small compared to states like Texas (395,816 horses), Oklahoma (158,918 horses), and Kentucky (141,842 horses, USDA, 2013). However, the South Carolina equine industry has increased over the last twelve years.

The increase in interest and participation in horse ownership centers around several activities including trail riding, polo, fox hunting, Western and English competitions, shows, and training facilities of all kinds. These activities are facilitated by the hundreds of miles of riding trails available on public lands, the presence of a steeplechase track near Camden, SC, numerous polo fields near Aiken, SC, and large arenas for shows at Clemson University, and near Landrum, SC.

The increase in horse population also increased the amount of horse manure to be managed in a responsible manner. It has been estimated that about 30 kg (66 lb) of manure and soiled bedding is removed from a typical horse stall each day (Wheeler, 2006). Every 1000 kg of bedded horse manure contains about 6 kg of total-N, 2.5 kg of P2O5, and 4.5 kg of K2O (Wheeler and Zajaczkowski, 2001). Horse manure also contains large amounts of carbon, organic matter, and many valuable minor plant nutrients, such as Ca, Mg, S, Zn, Cu, Mn, and Fe. However, little data is available in the literature concerning concentrations of minor plant nutrients in stall manure (Lawrence et al., 2003).

The large amount of carbon contained in horse manure has been shown to greatly reduce the availability of nitrogen following land application of horse manure. Several sources and studies have indicated that the large amounts of carbon can induce nitrogen deficiency due to immobilization of soluble nitrogen (e.g. James, 2003, Doesken and Davis, 2007). As a result, horse manure is typically not a good source of nitrogen as compared to poultry litter.

The goal of this project was to obtain equine manure composition data that can be used for the development of manure management plans. Given the wide variability in the daily use of stalls, the amount of bedding used in stalls, and other stall management factors it was hypothesized that stall management would have a significant impact on the composition of equine manure, and may have an impact on recommended manure utilization practices. The objectives to meet this goal were to: (1) collect as-removed bedded stall samples on six horse farms during routine stall cleaning, (2) obtain bedding-free manure samples from at least three farms, (3) classify each barn by stall management, and stall use, (4) determine if stall management had a significant impact on the solids and plant nutrient content of equine manure, (5) develop manure management recommendations and a table of characteristics to be used for manure management planning for equine facilities.

What did we do? 

Six horse farms were selected that included facilities that ranged from small, pleasure horse barns to farms with multiple barns that provided intensively managed housing for race, and show horses. Each horse farm was visited once to obtain samples of bedded stall manure. Samples were collected as manure and fouled bedding was removed from the stalls according to normal daily stall management practices. During the site visit, the owner of the facility was asked questions about bedding practices, manure removal frequency, and stall use frequency. Based on these interviews and observations during the site visit, the farms were classified by stall use and bedding management categories as shown in Table 1.

Table 1. Description of the six horse farms and manure samples collected

Table 1.

On Farm 3 (see Table 1), bedded manure that was removed daily from stalls was stored in large, uncovered, windrows for extended periods of time prior to application to pastures. The owner called the piles compost piles. However, it was evident that very little heating was taking place. Samples were taken from several locations and depths in an old windrow of unknown age. These samples were well-mixed to provide a representative sample for analysis. The composition of these samples was to be compared with bedded manure as-removed from the stalls. While visiting Farms 2, 3, and 6 samples of horse manure without bedding were obtained from stalls to provide a comparison to heavily bedded horse manure.

Manure samples were collected from the stalls, or the uncovered windrow, using shovels and a wheel barrow. The manure was mixed well in the wheel barrow using a shovel and a pitch fork. Three, 2 to 3 L samples of the manure from each barn were placed in sealed, plastic containers, and were transported on ice to Clemson University for analysis at the Agricultural Service Laboratory. Three replicate analyses were performed for each of the 6 horse barns (Farms 1-6), bedding-free manure (one sample each from Farm 2, 3, and 6), and the uncovered pile (Farm 3). The plant nutrients concentrations measured were: total nitrogen (Total-N), total ammoniacal nitrogen (TAN = NH4+-N + NH3-N), nitrate-N, total P (expressed as P2O5), total K (expressed as K2O), calcium, magnesium, sulfur, zinc, copper, manganese, iron, and sodium. The organic-N content was calculated as: Organic-N = Total-N – TAN – nitrate-N. Other characteristics measured included: moisture content, total carbon content, organic matter content (O.M.), pH, and electrical conductivity (EC). Standard laboratory procedures were used for all analyses and details are provided by Moore (2014).

What have we learned? 

Statistical analysis of the organic matter, Total-N, P2O5, K2O, and several minor plant nutrient concentrations (dry basis) indicated that the composition of manure collected from each of the barns, and the covered pile were significantly different in one or more characteristics. These results point out that data collected from individual facilities are needed to account for farm-to-farm differences in feed composition, use of mineral supplements, stall management, and stall use. A summary of the data is provided in Table 2.

Table 2. Mean characteristics of horse manure based on stall management, and storage in an uncovered pile, wet basis

Table 2.

Storage of manure in an uncovered pile resulted in very little active composting as indicated by an insignificant reduction in organic-N, and only a small reduction in carbon (3%). Uncovered storage also resulted in reductions in major and minor plant nutrient concentrations ranging from 33% (Mn) to 74% (K2O). Therefore, nutrient content data obtained from bedded manure as-removed from a stall was shown to be inadequate to determine agronomic applications rates for manure removed from storage. In practice, separate data sets would be needed for management of as-removed horse manure, and manure removed from storage for development and implementation of a manure management plan.

In general, as the quality of stall management increased the amount of bedding provided per stall per day increased resulting in an increase in C:N. The C:N ranged from 23 to 48 for the barns sampled on the six farms. A correlation analysis was conducted to determine if the dry matter concentrations of organic matter, and plant nutrients were significantly correlated with C:N. The only measured characteristic that had a significant positive correlation with respect to C:N was the organic matter content. This was not surprising since bedding was the source of additional organic matter. The plant nutrients that had significant negative correlations with respect to C:N were: organic-N, total-N, P2O5, Ca, Mg, Zn, and Cu. It was apparent that one of the effects of additional bedding use was to dilute major and minor plant nutrient concentrations.

Electrical conductivity is often used as a general measure of the salt content in manure, compost, and other soil amendments. The eight different treatments included in this study had EC values ranging from 0.45 to 3.46 mmhos/cm. A correlation analysis was used to determine which of the conductive elements included in the analysis (Cu, Ca, Mg, Na, Zn, K2O, Fe, Mn) were significantly related to EC. It was determined that the only plant nutrient that was a significant predictor of elevated EC values was K2O content (dry-basis) with a correlation coefficient of 0.9727 and a coefficient of determination of 0.9462. Consequently, the high EC values observed were directly correlated to high levels of potassium and not harmful salts. These results demonstrate that EC alone cannot be used to determine if plant toxicity is likely, but sufficient analyses should be performed to determine if the elevated EC is from valuable nutrients or salts as suggested previously by others (e.g. Compost for Soils, 2011).

All of the horse manure samples collected on the six farms studied contained large amounts of carbon as indicated by C:N ratios ranging from 23 to 48. As a result, horse manure was not accessed to be a good source of nitrogen as compared to poultry litter. It may be best to compost horse manure to stabilize bioavailable carbon and nitrogen prior to use. After composting, the material should be applied based on agronomic rates for P2O5, or K2O while accounting for the organic nitrogen that will be slowly released.

Another alternative may be to apply horse manure based on agronomic rates for P2O5 or K2O while adding additional nitrogen to offset induced nitrogen deficiency. If un-composted manure is spread on cropland or pasture a portion of the mineralized-N will be converted to organic-N and would be expected to release slowly later in the year, and a portion may be carried over into subsequent growing seasons. Estimation of available carry-over nitrogen is difficult due to uncertainties related to soil pH, moisture, temperature, rainfall, and microbial activity. However, the best method of estimation appears to be a series of organic-N availability factors provided by Wheeler (2006).

A complete report on this study is provided by Chastain and Moore (2014).

Future Plans    

The results from this study will be used to develop extension classes and literature for owners of equine facilities. These data will also provide valuable information for nutrient management planning.

Authors       

John P. Chastain, Ph.D., Professor and Extension Agricultural Engineer, Clemson University jchstn@clemson.edu

Kathy P. Moore, Ph.D., Director, Agricultural Service Laboratory, Clemson University

Additional information 

References Cited

Chastain, J.P. & K.P. Moore. 2014. Plant Nutrient and Carbon Content of Equine Manure as Influenced by Stall Management in South Carolina. ASABE. Paper No. 1908331. ASABE, 2950 Niles Rd., St. Joseph, MI 49085-9659.

Compost for Soils. (2011). Compost Characteristics. Factsheet published by Compost for Soils, A Division of the Austrailian Organics Recycling Association. Retrieved from: http://compostforsoils.com.au/images/pdf/practical%20compost%20use/compo….

Doesken, K. C., & Davis, J. G. (2007). Determining plant available nitrogen from manure and compost topdressed on an irrigated pasture. In Proc. International Symposium on Air Quality and Waste Management for Agriculture. ASABE Publication Number 701P0907cd. St. Joseph, Mich.: ASABE.

James, R.E. (2003). Horse Manure Management: The Nitrogen Enhancement System. AGF-212-03. Ohio State University Extension, The Ohio State University, Columbus, OH.  Retrieved from: http://ohioline.osu.edu/agf-fact/0212.html.

Moore, K.P. (2014). Compost Analysis Procedures. Clemson, SC: Agricultural Service Laboratory, Clemson University. Available  at: Available at: http://www.clemson.edu/agsrvlb/procedures2/compost.htm.

Wheeler, E.F, and J.S. Zajaczkowski. (2001). Horse Stable Manure Management (G-97). Penn State University Extension. Available at: http://panutrientmgmt.cas.psu.edu/pdf/G97.pdf.

Wheeler, E. F. (2006). Manure Management, In Horse Stable and Riding Arena Design, (pp 91-93). Ames, Iowa: Blackwell Publishing.

Acknowledgements      

Support for this work was provided by the Confined Animal Manure Management Program of Clemson Extension, Clemson University, Clemson, SC.

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.