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An Analysis of Poultry Litter Purchases in South Carolina

Purpose

Poultry production is the number one agricultural enterprise in value of production for South Carolina with approximately 280,000,000 birds in inventory.  Poultry litter as a by-product of poultry production is a low-cost fertilizer that can provide nitrogen (N), phosphorus (P), potassium (K), and micronutrients for forage systems. Poultry litter can improve soil fertility and health by adding organic matter and enhancing water infiltration and soil fertility over time on more than 300,000 acres of forages in South Carolina.

Yet, despite purported benefits to the pasture system and use as a fertilizer to improve forage, questions remain for livestock producers looking to apply poultry litter to their pastures. There is a lack of information about the availability, cost, and quality of litter.  With the increase in interest in poultry litter applications as a climate-smart agricultural practice or to participate in conservation programs, this work is expected to assist regional producers in understanding poultry litter attributes and inform purchasing decisions.

What Did We Do?

Using a dataset of 68 producers utilizing poultry litter and the corresponding transactions, we characterize the availability and market for poultry litter in South Carolina. Data on transactions, including prices paid, delivery date, application rate, and county-level location of litter, forms the basis for analysis. Also, we use sample analysis results to compare nutrient price with commercial fertilizer nutrient values.

What Have We Learned?

Of the 68 producers reporting data, 45 reported detailed price, location and application information. An exploration of prices paid per ton of litter across the state suggests differences based on location (Table 1).  Based on the results of a t-test, higher prices are observed for the mid-state compared to the upstate (statistically significant at 6% level for two tail t-test). Differences in prices observed by season appear but are not statistically significantly different based on ANOVA tests.

Table 1: Average price per ton of litter based on region of the farm and season applied.
Midstate (n=20) Upstate (n=25)  Average
Fall 25.55 22.32 23.30
Spring 32.13 22.55 28.02
Summer 22.31 — 22.31
Winter — 19.33 19.33
Average 27.37 22.02 24.40

Other findings from the data could be helpful to design outreach and assist producers looking to purchase litter for their operation. Some other interesting information includes the type of litter: broiler, layer, turkey, and other sources. Also, of the producers in the sample, 19 were unable to find litter with the majority of producers located in the Upstate area (74%).

Next, for the approximately 40 samples that included nutrient analysis, a summary of mean and standard deviation of pounds per ton of ammonium N, organic N, P205 and K20 are given in Table 2. From prices reported by each producer, the cost per pound of nutrient is also calculated. From here, average fertilizer and nutrient prices were gathered for South Carolina and displayed in Table 3. Similar costs can be seen when comparing the average cost per pound for each nutrient (Table 2) to the average price per pound for commercial fertilizers (Table 3).  For example, the average cost of a pound of ammonium N from the poultry litter sources was $2.46/lb and $2.45/lb from commercial sources.

Table 2: Summary statistics of nutrient analysis from 40 samples.
Nutrients
  Ammonium N (lbs./ton) Organic N (lbs./ton) P205 (lbs./ton) K20 (lbs./ton)
n 41 40 42 42
mean 10.04 50.21 47.15 51.65
std dev 3.93 15.09 20.41 21.04
$/# $2.46 $0.49 $0.52 $0.48
Table 3: Average fertilizer prices for South Carolina by fertilizer type and cost per pound for nutrients N, P, K.
South Carolina Average Fertilizer Prices FY2024
DAP (18%-46%-0%) Urea (46%) 10-10-10 Potash (60%)
Mean $881.00 $504.45 $489.00 $482.45
Std. Dev. $8.02 $13.30 $5.72 $13.05
N ($/#) $2.45 $0.55 $2.45 $0.00
P ($/#) $0.96 $0.00 $2.45 $0.00
K ($/#) $0.00 $0.00 $2.45 $0.40

Source: South Carolina Crop Production Report (Monthly), Livestock, Poultry, and Grain Market News, USDA Agricultural Marketing Service.

Future Plans

Findings and data from this analysis will first be prepared for outreach and dissemination efforts to producers across the state. Information will also be summarized for current enrollees in the grant program. Finally, given that this data was collected as part of a five-year study, data will be collected in subsequent years. Ultimately, a hedonic analysis of poultry litter attributes to help understand differences in price as a result of nutrient attributes, storage conditions, type, and trucking could inform producer sourcing of litter and prices paid.

Authors

Presenting & corresponding author

Nathan B. Smith, Extension Economist, Clemson University, nathan5@clemson.edu

Additional authors

Anastasia W. Thayer, Assistant Professor, Clemson University; Matthew Fischer, Extension Associate, Clemson University; Maggie Miller, Extension Associate, Clemson University.

Additional Information

https://www.climatesmartsc.org/

Acknowledgements

This material is based upon work supported by the U.S. Department of Agriculture, under agreement number NR2338750004G049.

 

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. 2025. Title of presentation. Waste to Worth. Boise, ID. April 7-11, 2025. URL of this page. Accessed on: today’s date.

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Bridging the Gap: Communicating Sustainability Research to Southern Idaho Dairy Farmers

Purpose

This is an example of an informative social media post that shows the ISAID Grant’s research with dairy manure.
This is an example of an informative social media post that shows the ISAID Grant’s research with dairy manure.

Dairy farming is at the heart of Southern Idaho’s economy and way of life. As pressures mount around environmental impact, consumer expectations, and long-term viability, sustainability has become essential to the future of dairy. While research in this area has made significant strides, many farmers struggle to access and apply this information in a way that makes sense for their operations. Scientific studies are often dense, packed with technical jargon, and filled with data that doesn’t always connect to the everyday realities of farming.

This graphic explains what circular bioeconomy is, a term used often in sustainability research.
This graphic explains what circular bioeconomy is, a term used often in sustainability research.

This project aims to close the information gap by using research from the Idaho Sustainable Agriculture Initiative for Dairy (ISAID) Grant to make sustainability science more accessible and actionable. Our goal is to translate research into tools and messages that help farmers adopt practical, sustainable practices that benefit their operations and the broader agricultural landscape.

What Did We Do?

To better understand the communication barriers farmers face, we conducted a literature review focusing on agricultural communication and knowledge transfer, particularly in dairy sustainability. Our review included studies on the communication preferences of dairy producers, social media engagement in agriculture, and the role of trusted advisors such as veterinarians and extension specialists in knowledge dissemination. Key findings from this review highlighted the importance of concise, visually engaging content and digital platforms like Facebook and YouTube for reaching dairy farmers. We also examined studies on farmers’ motivations and perceived barriers to adopting sustainable practices, which emphasized the need for messages that align with farmers’ economic and operational priorities.

This graphic gives farmers suggestions for how to make their land more sustainable.
This graphic gives farmers suggestions for how to make their land more sustainable.

Additionally, research on sustainable practice adoption highlights that behavioral change plays a critical role in whether farmers choose to implement new sustainability measures. Concepts from the social science of behavior change, such as the Diffusion of Innovation (DOI) theory and the Reasoned Action Approach (RAA), help explain how farmers evaluate new practices. Key factors include perceived relative advantage, compatibility with existing practices, complexity, trialability, observability, and riskiness. These insights suggest that effective communication strategies should focus not just on providing information but also on addressing these concerns to increase adoption likelihood. Studies also show that demographics, land tenure, and financial constraints play significant roles in whether a farmer adopts new practices, reinforcing the need for tailored communication that takes these contextual factors into account.

Hydrochar and Biochar are often mentioned in the ISAID Grant’s research. This graphic explains what each one is and how it is used.
Hydrochar and Biochar are often mentioned in the ISAID Grant’s research. This graphic explains what each one is and how it is used.

To implement these strategies, we built a website that serves as a hub for sustainability research, providing easy access to summaries, case studies, and media. Additionally, we launched The Clever Cow Podcast, where industry experts, researchers, and farmers discuss sustainability, innovation, and best practices. A structured social media strategy further expands our outreach, allowing us to engage farmers through Facebook, Instagram, and YouTube. Recognizing the role of selective exposure and confirmation bias in how farmers consume information, we have designed our content to align with existing beliefs while also introducing new sustainability concepts in an engaging and relatable manner. To ensure our approach remains farmer-focused, we will conduct focus groups and surveys this summer to gather direct feedback, refine our outreach efforts, and develop communication strategies that effectively bridge the gap between researchers and the dairy community.

What Have We Learned?

Initial research and discussions suggest that farmers value concise, visually engaging content over lengthy technical reports. Social media and digital platforms, especially Facebook and YouTube, have emerged as preferred tools for accessing sustainability information. Farmers have also emphasized the importance of seeing practical examples of sustainability in action, such as case studies of dairy producers who have successfully incorporated sustainable practices. Additionally, partnerships with trusted organizations like local extension offices strengthen credibility and ensure that information is regionally relevant.

This informational card was used to share information with dairy producers about biodegradable plastic made from dairy manure.
This informational card was used to share information with dairy producers about biodegradable plastic made from dairy manure.

Our research also highlights the need to consider cognitive biases in message design. Confirmation bias and selective exposure influence the way farmers engage with agricultural information, meaning that they are more likely to interact with content that aligns with their existing beliefs. By strategically framing sustainability messages in ways that resonate with their values—such as economic benefits, operational efficiency, and long-term resilience—we can increase engagement and encourage the adoption of sustainable practices. These findings highlight the importance of tailoring communication strategies to respect farmers’ time while making complex sustainability research easier to understand and apply.

Future Plans

In summer 2025, we will conduct two focus groups (12 farmers each) and distribute a statewide survey targeting over 100 Southern Idaho dairy producers. These efforts will gather direct input on preferred communication channels, trusted sources of information, and barriers to engaging with sustainability research. Using this feedback, we will refine and test outreach tools such as short-form videos, podcast episodes, social media graphics, and research-backed infographics. The insights gained will inform the development of a flexible, scalable communication model that can be customized for other agricultural communities across the U.S.

Authors

Presenting author

Savanah Nunes Carpenter, M.S. Graduate Student, Media and Communications Director, ISAID Grant, University of Idaho

Corresponding author

Dr. Mireille Chahine, Acting Head and Professor, Department of Animal Veterinary and Food Sciences, University of Idaho, mchahine@uidaho.edu

Additional Information

To learn more, visit the ISAID Grant website: www.uidahoisaid.com

Follow us on social media:

This video explains my research in four minutes: https://youtu.be/_3JWGDQgf0Y?si=Hpu233CQXFb1Dk8R

 

Acknowledgements

This research was funded by the USDA Sustainable Agricultural Systems Initiative through the Idaho Sustainable Agriculture Initiative for Dairy (ISAID) grant (Award No. 2020-69012-31871).

Special thanks to the ISAID Grant research team, the University of Idaho Extension, and the Southern Idaho dairy farmers who will participate in the upcoming focus groups and surveys.

 

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. 2025. Title of presentation. Waste to Worth. Boise, ID. April 7-11, 2025. URL of this page. Accessed on: today’s date.

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Decades of advancement in the practice of manure storage and toward continued future success

Purpose

The history and development of the practice of manure storage over time in the US is told to educate new stakeholders, illustrate collective industry advancements and failures that have shaped course, and urge support for future success using rational design approaches, especially for concrete liners.

What Did We Do?

From literature and research interviews we layout a narrative for how the practice of manure storage design has changed over time. Change in the practice is traced by examining the development and use of the four major lining materials of earth, steel, plastic and concrete against the larger backdrops of consolidation and increasing environmental caution. Special focus is given to concrete, a lining material with relatively high durability and low permeability but limited rational design methodology.

What Have We Learned?

The practice of manure storage is shown to have advanced over the decades resulting in lower permitted seepage obtained for longer lifespans. This advancement has occurred under pressures for larger storages that are held to higher environmental standards.  This advancement has been made possible by the development of existing and new materials, including significant technical support behind them developed by governmental agencies, industries that supply the materials, and engineers who utilize them on farms. In the area of concrete liners there is room for significant advancement to develop near zero seepage liners at feasible cost, through the use of frameworks that are rational (mechanistic-empirical) and quantifiable.

Future Plans

Complete stage gate analysis for obtaining design seepage rates for concrete liners used in manure storage, that are mechanistic based and quantifiable.

Authors

Presenting & corresponding author

Mike Krcmarik, Professional Engineer, mikekrcmarik@gmail.com

Email corresponding author for a copy of the presentation and all collected references.

Acknowledgements

The author would like to acknowledge employees of the USDA’s Natural Resources Conservation Service, private consulting engineers designing manure storages, state regulators supporting manure storages, and material industry representatives for providing perspectives and resources used in assembling this presentation.

 

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. 2025. Title of presentation. Waste to Worth. Boise, ID. April 7-11, 2025. URL of this page. Accessed on: today’s date.

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Sustainable Approach to Agriculture Education: Making the Most of Dairy Waste Byproducts

Purpose

The purpose of the project has been to develop a scientifically grounded, curriculum-ready educational framework that equips educators, especially those in Idaho, with the knowledge and instructional tools necessary to introduce students to the dairy industry and specifically, the environmental and economic benefits of dairy waste by-products. This project aimed to bridge the gap between industry practices and secondary agricultural education by highlighting sustainable waste management strategies within the dairy sector, including manure management, organic fertilizer production, methane gas utilization for renewable energy, and innovative by-product applications.

By integrating interdisciplinary concepts in agricultural science, environmental sustainability, and economics, we have worked to enhance students’ understanding of circular bioeconomy principles, real-world waste management challenges, and the importance of dairy sustainability in mitigating environmental impact while generating economic value. The ultimate goal is to foster a new generation of agriculturally literate students who can critically evaluate and contribute to sustainable innovations in the dairy industry.

What Did We Do?

We are presenting a comprehensive, two-week educational curriculum designed to equip Idaho educators with a resource on the state’s dairy industry. The curriculum encompasses foundational topics, including an introduction to dairy cattle, dairy nutrition, production facilities, and the processes involved in milk and cheese production. However, its primary emphasis is on the sustainable management of dairy by-products, addressing key environmental challenges associated with dairy operations.

The above figure is an of the instructional framework for the dairy unit, illustrating the progression of concepts in the unit and the layout of including daily objectives and alignment to state and national academic standards.
The above figure is an of the instructional framework for the dairy unit, illustrating the progression of concepts in the unit and the layout of including daily objectives and alignment to state and national academic standards.

This interdisciplinary curriculum explores advanced dairy waste management strategies, including manure management, biochemical conversion into organic fertilizers, and anaerobic digestion for methane gas production. Through hands-on learning and real-world case studies, the curriculum connects industry practices with secondary agricultural education, fostering a deeper understanding of the ecological and economic impacts of sustainable dairy waste repurposing.

What Have We Learned?

Our findings indicate that students are both prepared and capable of engaging with new scientific and industry-specific information when presented through differentiated and interactive instructional methods. A pre-unit assessment was administered on 2/25/2025 prior to introducing the first-time curriculum, with students averaging 59% on the assessment. Following the conclusion of the unit on 3/14/2025, the average score on the same material rose to 89%. We believe even in the initial rollout of curriculum, this significant increase reflects meaningful learning gains, especially when considering the variability in student learning styles and attendance. The incorporation of varied learning modalities—ranging from hands-on applications to case-based discussions—provided sufficient cognitive engagement, contributing to sustained student interest and improved comprehension throughout the unit.

Furthermore, this approach facilitates exposure to specialized aspects of the dairy industry that may otherwise remain unexplored, even by students residing in regions with high dairy production. By integrating diverse educational strategies, the curriculum broadens students’ conceptual understanding of sustainable dairy waste management, reinforcing the applicability of these practices within both local and global agricultural contexts.

Future Plans

Moving forward, the curriculum will be made available to agricultural educators across Idaho and the broader Northwest region, providing a flexible instructional resource that can be implemented in whole or adapted to meet specific classroom needs. By offering the curriculum in a digital format, accessible from anywhere, educators will have the ability to customize content to align with their students’ learning objectives while maintaining the integrity of the scientific and industry-relevant information presented.

This resource serves as a readily accessible tool for high school instruction, facilitating an in-depth exploration of the dairy industry, milk and cheese processing, and the complex sustainability challenges faced by modern dairy operations. By emphasizing the innovative repurposing of dairy by-products into value-added commodities, the curriculum equips students with a critical understanding of the environmental and economic imperatives driving sustainability within the dairy sector.

Authors

Presenting & corresponding author

Melissa A. Renfrow, University of Idaho, renfrow@uidaho.edu

Additional author

Dr. Kattlyn Wolf, Professor, Department of Agricultural Education, Leadership and Communication, University of Idaho

Additional Information

Acknowledgements

This Idaho Sustainable Agriculture Initiative for Dairy project is supported by USDA-NIFA SAS award #2020-69012-31.

 

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. 2025. Title of presentation. Waste to Worth. Boise, ID. April 7-11, 2025. URL of this page. Accessed on: today’s date.

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Co-recovery of phosphorus from manure using acid precursors contained in other wastes.

Purpose

A new approach for recovering nutrients and value-added products from waste is to search for a synergistic effect by combining two or more wastes.  This work improved the recovery of phosphorus and proteins/amino acids abundant in swine manure by adding a second waste or product rich in sugars, such as molasses, fruit waste, or lactose waste.  The second waste rich in sugars acted as a natural acid generator that replaced purchased acids and lowered the overall recovery cost.

What Did We Do?

A new approach was developed to separate and recover concentrated phosphorus and proteins from animal waste (Vanotti and Szogi, 2019).  It was improved by adding a second waste or product containing sugars, such as molasses and fruit waste (Vanotti et al., 2020).  They could be used as a natural acid precursor that replaces purchased acids and lowers the overall cost of phosphorus and protein recovery.  In this study, the two model wastes were swine manure solids (source of extractable phosphorus and proteins) and peach waste (source of acid precursors).

What Have We Learned?

On a dry-weight basis, the swine manure solids contained high amounts of proteins (15.2%) and phosphorus (2.9%) available for extraction. It was shown that waste peaches, an abundant waste in the Southeastern USA with no cost except transportation, contain about 8% total sugars and can be used as an acid precursor to effectively extract phosphorus and proteins from swine manure (waste peaches were peaches that were too soft, had bad spots, or did otherwise not meet the grade at the Processing Plant for sale as fresh fruit). The waste peaches (Brix 7.7 deg) were added to the manure, and the combo received rapid fermentation (24-h) after adding an inoculum (Vanotti et al., 2020).  Adding fruit waste to the manure and rapid fermentation produced abundant natural acids – lactic acid, citric acid, and malic acid – that effectively solubilized the phosphorus in the manure (Fig. 1).  Further, the peach fermentation did not adversely affect the protein recovery from the manure.  A pH of about five or less is a valuable target to optimize the phosphorus and protein recovery from manure.  The target was successfully met using a variety of natural acid precursors (fructose, molasses, peaches, lactose). The phosphorus was precipitated with calcium or magnesium compounds, obtaining concentrated phosphate products with > 90% plant-available phosphorus. The proteins/amino acids in the manure were quantitatively recovered. Other fruits, vegetables, and food waste products also contain significant amounts of sugar, so this is not limited to only wasted peaches. It is contemplated that other sugar-containing agricultural by-products could be used in this process for the same purpose with minor adjustments for amounts depending on the sugar concentration and initial pH of the fruit or vegetable.

Fig. 1. Adding an acid precursor to the manure and rapid fermentation increased acidity and the phosphorus recovery from the manure, up to a plateau recovery (Vanotti et al., 2023).
Fig. 1. Adding an acid precursor to the manure and rapid fermentation increased acidity and the phosphorus recovery from the manure, up to a plateau recovery (Vanotti et al., 2023).

Future Plans

Research will be presented showing consistent phosphorus extraction results obtained with swine manure and sugar beet molasses as the acid precursor, and with dairy manure and lactose waste as the acid precursor. USDA-ARS seeks a commercial partner to bring this technology to market.  For more information on commercialization, contact: Mrs. Tanaga Boozer, Technology Transfer Coordinator, USDA-ARS, OTT Southeast Area, tanaga.boozer@usda.gov

Authors

Presenting & corresponding author

Matias Vanotti, USDA-ARS, Matias.vanotti@usda.gov

Additional authors

Vanotti, M.B, Szogi, A.A., and Brigman, P.W.  USDA-ARS, Florence, SC

Moral, R. Miguel Hernandez University, Orihuela, Spain

Additional Information

Vanotti, M.B., Szogi, A.A. 2019. Extraction of amino acids and phosphorus from biological materials. US Patent 10,150,711. US Patent & Trademark Office.

Vanotti, M.B., Szogi, A.A., Moral, R. 2020. Extraction of amino acids and phosphorus from biological materials using sugars (acid precursors). US Patent 10,710,937. US Patent & Trademark Office.

Vanotti, M., Szogi, A., Moral, R., & Brigman, W. 2023 (November). Recovery of Value-Added Products from Swine Manure and Waste Peaches. In National Conference on Next-Generation Sustainable Technologies for Small-Scale Producers (NGST 2022) (pp. 38-42). Atlantis Press.

Acknowledgements

This research was part of USDA-ARS National Program 212, ARS Project 6082-12630-001-00D. Support by Mitsubishi Chemical Corporation, Japan, through ARS Project 58-6082-7-006-F, is also acknowledged.  Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. 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. 2025. Title of presentation. Waste to Worth. Boise, ID. April 7-11, 2025. URL of this page. Accessed on: today’s date.

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From Waste to Worth; Creating an educational opportunity from a disaster

Purpose

North Dakota was impacted by the 2022 Highly Pathogenic Avian Influenza (HPAI) outbreak. Responders to the HPAI outbreak included the North Dakota Department of Agriculture, North Dakota Department of Environmental Quality, USDA Animal and Plant Health Inspection Service (APHIS), North Dakota State University (NDSU) Veterinary Diagnostic Laboratory, NDSU Extension, county emergency managers and veterinarians. Many responders were new employees and were not involved in response efforts during the 2015 HPAI outbreak, including 62% of county Extension agents. The lack of experience and knowledge resulted in a significant amount of time and effort spent determining the appropriate agencies to contact, defining agency roles, developing educational resources, and creating an awareness of biosecurity and procedures used in active cases. Additionally, limited attention was given to stress management or mental health and well-being during this period of heightened stress for personnel involved in response.

What Did We Do?

NDSU Extension received a 2023 USDA APHIS National Animal Disease Preparedness and Response Program grant to train professionals on how to safely respond to an animal disease outbreak or mass livestock mortalities. Training topics included:

    • An overview of animal diseases
    • Continuity of business planning
    • Personal protective equipment and decontamination
    • Incident command systems, local response roles and impact assessment
    • Humane endings
    • Carcass disposal site selection and methods
    • Stress management and responding to stressed people
    • Effective communication in high stress situations
    • A response simulation exercise.

The curriculum was developed over a 5-month period and was previewed by 25 attendees during the North Dakota Veterinary Medical Association’s Annual Winter Conference. A total of 11 attendees responded to a survey of which 100% agreed the training increased their confidence in responding to a foreign animal disease (FAD), while 91% indicated the materials presented were appropriate for those responding to an animal disease outbreak at the local level. All topic areas were rated as either moderately useful or very useful. Suggested improvements to the curriculum were made over the next 4 months until the first full training.

The one and a half day training events were held in person at the NDSU Carrington Research Extension Center (CREC) in June and September 2024. The training format included classroom, group work, demonstrations and hands-on activities. Each participant received a kit which contained personal protective equipment. A table-top exercise at the end of the training tied in all topics presented and provided time for groups to share experiences with response efforts.

 

Participants of the Emergency Response Preparedness for Foreign Animal Diseases and Mass Livestock Mortalities in North Dakota training viewed a non-disease mortality compost site. NDSU photo.

 

Emergency Response Preparedness for Foreign Animal Diseases and Mass Livestock Mortalities in North Dakota training participants practice donning PPE during hands-on portion of training. NDSU photo.

Participants of the Emergency Response Preparedness for Foreign Animal Diseases and Mass Livestock Mortalities in North Dakota training received Glo-Germ on their gloves as they exited the people movers to doff PPE. They rubbed it on their hands and then up and down their PPE. The Glo-Germ was used as a tool to aid in visual “contamination”. A black light was used after doffing was complete to spot any signs of “contamination”. NDSU photo. The NDSU Extension does not endorse commercial products or companies even though reference may be made to tradenames, trademarks or service names.

What Have We Learned?

In post-event evaluations of training participants, all respondents (57) indicated that the training increased their confidence and ability in responding to an animal disease or mass livestock mortality event. Additionally, 96% of respondents indicated they planned to make changes to be better prepared and better able to respond to animal diseases or mass livestock mortalities because of their participation in the training. Responses also indicated 93% improved their ability to provide support to individuals in high stress situations.

Post-training evaluation respondent comments included:

    • “One of the best trainings I’ve ever attended. Please make sure new ANR [agriculture and natural resources] agents attend this in the future.
    • “This was a great training and appreciate all the work put into it! It was good to understand the chain of command and know that many other offices would be working with a producer in a situation involving a FAD.”
    • “I appreciated the number of different professions represented at this meeting and their unique perspectives for this type of emergency response.”
    • “It was a great learning experience. The information was very useful and will be put to use if an event occurs. We EM’s [emergency managers] don’t normally deal directly with the emotional responses but we are resources for finding avenues for emotional support, which is great to know that there are people to reach out to in the animal industry. Overall, it was great to network with others and have more tools in the toolbox for when the situation occurs. GREAT JOB to everyone involved!!”

Six-month follow-up evaluation data from the first training session indicated that 91% of respondents (12) felt their community is better prepared for and able to respond to an animal disease or mass livestock mortality. Of these respondents, 45% took action to be more prepared for an animal disease or mass livestock mortality. Additionally, the training was successful in building relationships between responders in the state with 55% collaborating with individuals they connected with at the training to better prepare their communities to respond to an animal disease or mass livestock mortality. The six-month follow-up evaluation for the second training session will be administered in March 2025 and these proceedings will be updated with the information.

As part of the six-month evaluation, respondents were asked if they had taken actions to prepare for an animal disease or mass livestock mortality. Comments to date included:

    • “Put together a list of resources, working on a response plan, informed stakeholders on the process and procedures involved.”
    • “Monitoring of animal diseases in state and working with local producers and County Extension Agent.”
    • “I have been more diligent about collecting names of producers or contacts needed if any outbreak would occur.”

Future Plans

Based on feedback from participants, an online discussion and a one-day table-top training are being planned. A follow-up one-hour online discussion session for all training participants will occur in February 2025. A day-long tabletop training is being planned for September 2025. This training will be for Extension agents and emergency managers. The goal of this training is to continue to increase preparedness and response capacity at the local level through the development of skills and relationships.

Authors

Presenting & corresponding author

Mary A. Keena, Extension Specialist, North Dakota State University, mary.keena@ndsu.edu

Additional authors

Miranda Meehan, Ph.D., Associate Professor, Livestock Environmental Stewardship Specialist and Disaster Education Coordinator, North Dakota State University; Carolyn Hammer, DVM, Ph.D., Professor, Associate Dean of College of Agriculture, Food Systems and Natural Resources, North Dakota State University;  Heidi Pecoraro, DVM, Ph.D., DACVP, Director, Veterinary Diagnostic Laboratory, North Dakota State University; Sean Brotherson, Ph.D.,  Professor and Family Science Specialist, North Dakota State University; Ethan Andress, DVM, State Veterinarian, ND Department of Agriculture; Jodi Bruns, M. Ed., Leadership and Civic Engagement Specialist, North Dakota State University; Adriana Drusini, Extension Program Coordinator, Farm and Ranch Stress, North Dakota State University; Marty Haroldson, Program Manager, Division of Water Quality, ND Department of Environmental Quality; Angela Johnson, Farm and Ranch Safety Coordinator, North Dakota State University; Margo Kunz, DVM, Assistant State Veterinarian, ND Department of Agriculture;  Julianne Racine, Extension Agent, Agriculture and Natural Resources, LaMoure County, North Dakota State University; Karl Rockeman, P.E., Director, Division of Water Quality, ND Department of Environmental Quality; Jan Stankiewicz, MS, MPH cert., Community Health and Nutrition Specialist & Tribal Liaison, North Dakota State University;  Rachel Strommen, Environmental Scientist, ND Department of Environmental Quality; and Kent Theurer, Emergency Management Specialist, ND Department of Agriculture.

Additional Information

Twenty-one new Extension publications in either English or Spanish will be created from this project. Completed to-date include:

Acknowledgements

The USDA Animal and Plant Health Inspection Service National Animal Disease Preparedness and Response Program funded this project. Project ID: ND01.22.

Special thank you to our support staff members, Myrna Friedt, Linda Schuster, Stephanie Sculthorp-Skrei and Lynne Voglewede as well as the NDSU Agriculture Communications department for all of the time and effort you put into these trainings and materials.

 

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. 2025. Title of presentation. Waste to Worth. Boise, ID. April 7-11, 2025. URL of this page. Accessed on: today’s date.

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Sustainability of the Dairy Industry in the United States

Purpose

The U.S. dairy industry recognizes its environmental impact and has committed to achieving carbon neutrality by 2050, aiming to significantly reduce greenhouse gas (GHG) emissions while maintaining production efficiency. The primary sources of dairy-related emissions include enteric methane from cows, manure management, feed production, and energy use on farms.

Improvements in feed efficiency and manure management have already led to reductions in emissions per unit of milk produced. For instance, Idaho has successfully reduced enteric methane emissions per unit of milk by 25% since 1990, and methane emissions from manure per unit of milk have declined by about 20% (O’Hara, 2022). However, the total emissions from manure have increased by 20% due to herd growth in Idaho. These figures highlight the challenge of balancing productivity with environmental stewardship. Despite these difficulties, advancements in animal nutrition, manure management, and emerging technologies provide a promising path toward sustainability.

What Did We Do?

Over the past several decades, remarkable advancements in dairy farming have significantly improved milk production efficiency. Since the 1940s, the industry has nearly quadrupled milk output per cow through genetic improvements, optimized nutrition, and better overall management. This increase in productivity has allowed farmers to produce more milk with fewer cows, reducing the environmental footprint of each unit of dairy produced. Beyond improvements in feed efficiency, nutritional interventions such as adding feed additives like 3-NOP (3-nitrooxypropanol), seaweed, and oilseeds have been shown to reduce enteric methane emissions by altering rumen microbial activity. Research suggests that 3-NOP, for instance, can reduce methane emissions by up to 30% without negatively affecting milk yield or composition (Hristov, 2021).

Manure management is another critical area of focus. Technologies such as anaerobic digesters, composting systems, and improved storage techniques have been implemented to mitigate methane emissions from manure. Anaerobic digesters convert manure into biogas, which can be used as a renewable energy source, reducing the reliance on fossil fuels and lowering overall carbon emissions. Other strategies, such as mechanical separators and compost-bedded pack barns, have also been explored as effective methods for reducing methane release from stored manure.

What Have We Learned?

Several key strategies have emerged as effective pathways for improving dairy sustainability. The first is continued advancements in genetics, which allow farmers to breed more productive cows that require fewer resources per unit of milk produced. Selective breeding programs targeting low-methane-emitting cows could further contribute to sustainability efforts. Precision feeding techniques, which ensure cows receive the optimal balance of nutrients without overfeeding, are also crucial for reducing emissions. Feed additives such as tanniferous forages, alternative electron sinks like nitrates, and certain types of fats have shown potential in mitigating enteric methane production. However, long-term research is still needed to assess their effectiveness and potential side effects on animal health and productivity.

Another significant finding is the role of manure management systems in influencing overall farm emissions. Studies indicate that farms implementing covered liquid slurry storage and anaerobic digesters experience lower methane emissions compared to traditional open-lagoon systems. Additionally, manure treatment systems that integrate composting or separation techniques have been identified as key factors in reducing GHG emissions. Beyond farm-level practices, the industry has recognized the importance of collaboration across the supply chain. Processors, retailers, and policymakers must work together to promote sustainable practices, invest in research, and provide incentives for farmers to adopt new technologies.

Future Plans

Moving forward, the dairy industry will continue to focus on increasing milk production efficiency as a means of reducing emissions per unit of milk produced. Advances in genetics, feed optimization, and herd management will further contribute to sustainability efforts. Additionally, manure management will play a pivotal role in achieving sustainability goals. Expanding the use of anaerobic digesters and nutrient recycling technologies will help reduce emissions while providing renewable energy and valuable soil amendments.

Investment in research and innovation will be essential for identifying new strategies and improving existing ones. Research into alternative feed additives, precision agriculture, and digital monitoring tools will enable farmers to make data-driven decisions that enhance both productivity and environmental sustainability. Policy support and financial incentives will also be critical in accelerating the adoption of sustainable practices. Government programs and industry initiatives should continue to provide funding for technology adoption, carbon offset programs, and educational resources for farmers. Ultimately, the U.S. dairy industry is well-positioned to make significant strides toward its sustainability goals. By leveraging innovation, research, and collaboration, the industry can continue to provide essential nutrition while reducing its environmental footprint and working toward carbon neutrality by 2050.

Authors

Presenting & corresponding author

Mark A. McGuire, University Distinguished Professor, Department of Animal, Veterinary and Food Sciences, University of Idaho, mmcguire@uidaho.edu

Additional Information

Capper, J. L., Cady, R. A., & Bauman, D. E. (2009). The environmental impact of dairy production: 1944 compared with 2007. Journal of Animal Science, 87(6), 2160–2167. https://doi.org/10.2527/jas.2009-1781

El Mashad, H. M., Barzee, T. J., Franco, R. B., Zhang, R., Kaffka, S., & Mitloehner, F. (2023). Anaerobic digestion and alternative manure management technologies for methane emissions mitigation on Californian dairies. Atmosphere, 14(1), 120. https://doi.org/10.3390/atmos14010120

Godber, O. F., Czymmek, K. J., van Amburgh, M. E., & Ketterings, Q. M. (2024). Farm-gate greenhouse gas emission intensity for medium to large New York dairy farms. Journal of Dairy Science. https://doi.org/10.3168/jds.2024-25874

Hristov, A. N., Melgar, A., Wasson, D., & Arndt, C. (2021). Symposium review: Effective nutritional strategies to mitigate enteric methane in dairy cattle. Journal of Dairy Science, 105(10), 8543–8557. https://doi.org/10.3168/jds.2021-21398

Innovation Center for U.S. Dairy. (2022). U.S. Dairy Sustainability Report 2021-2022. Retrieved from https://www.usdairy.com/about-us/innovation-center

Kreuzer, M. (2024). Feed additives for methane mitigation: Introduction—Special issue on technical guidelines to develop feed additives to reduce enteric methane. Journal of Dairy Science.

Nguyen, B. T., Briggs, K. R., & Nydam, D. V. (2023). Dairy production sustainability through a one-health lens. Journal of the American Veterinary Medical Association, 261(1). https://doi.org/10.2460/javma.22.09.0429

O’Hara, J. K. (2022). State-level trends in the greenhouse gas emission intensity of U.S. milk production. Journal of Dairy Science, 106(10), 5474–5484. https://doi.org/10.3168/jds.2022-22741

Rotz, C. A. (2017). Modeling greenhouse gas emissions from dairy farms. Journal of Dairy Science, 101(7), 6675–6690. https://doi.org/10.3168/jds.2017-13272

U.S. Farmers & Ranchers in Action (USFRA). (2024). Potential for U.S. Agriculture to Be Greenhouse Gas Negative. Retrieved from https://www.usfraonline.org

Acknowledgements

Supported by USDA-NIFA SAS 2020-69012-31871

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Can Cover Crops Help Nutrient Management in Idaho Dairy Systems?

Purpose


This research aims to determine the effectiveness of cover crops (CCs) to improving nutrient uptake and soil health in a corn silage-cover crop system. Nutrient accumulation in soils from years of dairy manure or compost applications has increased the level of soil nutrients, creating environmental concerns. The study tests the feasibility and performance of different management strategies using CCs to mine nutrients from agricultural soils and reduce the negative environmental impact of manure or compost application.

What Did We Do?

In one study, two CC mixes (low height or tall) were inter-seeded (dual cropping) with corn silage at two different dates, near the corn planting date and later in the vegetative development. Two post-harvesting management strategies were used by either keeping the CC during the next season or terminating the CC in the spring, before the next corn silage planting. The control had no CC, only the corn silage. In an additional study, a fall CC mix was planted after corn silage harvest (double cropping). Different management strategies were used, including harvesting the CC, simulated grazing, green manuring the CC, and control with no CC. Both studies received the same amount of dairy manure compost annually, plus synthetic fertilizers. All other parameters, including corn planting and harvesting times and irrigation, were the same for both studies and all treatments. Weed management was adjusted using mowing as a method on plots with CCs, and herbicide on plots with no CCs.

What Have We Learned?

This study will continue for two more years. The first year of data collection was 2021. The inter-seeding (dual cropping) study results show very few significant differences in soil analysis comparing CC treatments. There were, however, statistically significant differences between some treatments and the control. This situation indicates that having an actively growing CC influences the soil nutrients and nutrient uptake compared to not having any CC when growing corn silage. The short CC mixes, either planted near the corn planting date or later during the corn vegetative development, tend to have the highest increase in soil OM, especially under reduced or no-till conditions, and reducing soil nitrates, ammonium, and total nitrogen. This can be explained by the better growth of the low mixes that continued growing after the corn silage harvest, compared with the high mixes that were harvested with the corn and rarely regrew after harvesting. CC establishment and growth was a challenge each year due to the corn silage shade. The low CC mix was the only one that was not terminated and continued to grow until after planting the corn silage the following spring. This treatment has proven challenging due to the aggressive CC regrowth and low growth of the corn with the CC competition, even when using strip tillage.

In most years, the previous season CC needed to be terminated to allow for the corn to grow and to reduce weed pressure before replanting the CC again. Soil phosphorous (P) did not show significant differences across treatments and control on the surface level. Phosphorus levels kept increasing during the study, indicating that the application rate far exceeded the crop uptake. In the case of nitrogen, even when CC showed increased nitrogen (N) uptake for all N species, nitrates have accumulated in soils, especially at lower depths, indicating leaching processes in all treatments and much more in the control (Figure 1). Cover crops can uptake some of the excess nitrogen, especially on the soil top layer, reducing the impact of N leaching (Figure 2). Under nutrient overapplication conditions, CCs that have not developed to their full potential cannot handle all the nutrients’ load, thus leaching can still occur. Overall, inter-seeding CC may have a positive impact on nutrient management when managed properly. This positive effect may be complex to quantify when comparing different CC practices with lower-than-ideal CC growth and under nutrient-overapplication conditions.

The second trial with double cropping with a single fall CC mix after harvesting the corn silage was more successful in most years in growing much more CC mass than the inter-seeding CC. The greatest differential was present only for a short period in spring before harvesting or terminating the CC for corn planting. Weed management during the corn growing season was simplified in the double (fall) cropping system. Results on the impact of fall CC and the different treatments compared to the control have not been fully analyzed.

Figure 1. Soil NO3-N estimated marginal means at 0-30 cm, 30-60 cm, 60-90 cm, and 90-100 cm depths across all sampling points in an inter-seeding corn silage-cove crop system receiving annual applications of dairy compost and synthetic fertilizer.
Figure 1. Soil NO3-N estimated marginal means at 0-30 cm, 30-60 cm, 60-90 cm, and 90-100 cm depths across all sampling points in an inter-seeding corn silage-cove crop system receiving annual applications of dairy compost and synthetic fertilizer.

Figure 2. Estimated marginal means of soil nitrate at 0-30 cm depth by CC planting timing, CC height, and CC vs control in an inter-seeding corn silage-cove crop system receiving annual applications of dairy compost and synthetic fertilizer.

Figure 2. Estimated marginal means of soil nitrate at 0-30 cm depth by CC planting timing, CC height, and CC vs control in an inter-seeding corn silage-cove crop system receiving annual applications of dairy compost and synthetic fertilizer.

Future Plans

There is additional data to analyze in both studies, including other soil chemical parameters, corn silage and CC yields, and feed quality. In the last year, moisture sensors were installed in some plots, measuring and recording soil moisture and temperature at different depths up to three feet. This moisture data at various depths could be correlated with nitrate values and other soil chemical parameters data to determine nutrient leaching, irrigation efficiency, and what role CC may play. Two additional seasons of data will be included to the dataset.

Authors

Presenting & corresponding author

Mario E. de Haro-Martí, Professor and Extension Educator, University of Idaho, mdeharo@uidaho.edu

Additional authors

Linda Schott, Assistant Professor, Extension Specialist, University of Idaho

Miguel Mena, MS Graduate Student, SWS Department, University of Idaho

Steven Hines, Professor and Extension Educator, University of Idaho

Anthony S. Simerlink, Assistant Professor and Extension Educator, University of Idaho

Clarence Robison, Research Support Scientist, University of Idaho

Additional Information

Idaho Sustainable Agriculture Initiative for Dairy website: https://www.uidahoisaid.com/

Acknowledgements  

The research team thanks the USDA-ARS Kimberly, ID personnel for their support with machinery and assistance with this project.

Funding for this project was provided by a USDA-NIFA Sustainable Agriculture Systems (SAS) grant #2020-69012-31871.

 

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. 2025. Title of presentation. Waste to Worth. Boise, ID. April 7-11, 2025. URL of this page. Accessed on: today’s date.

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Enhancing Phosphorus Recovery from Anaerobically Digested Dairy Effluent Using Biochar and FeCl₃ in a Rotary Belt Filter System

Purpose

This work aims to conduct pilot-scale trials using a rotary belt filter (RBF) with biochar to recover nutrients at a dairy anaerobic digestor and produce an upcycled bioproduct for soil amendment (Figure 1). Anaerobically digested (AD) effluents contain large quantities of phosphorus (P), nitrogen (N), and organic carbon, while biochar is a reactive material that has potential for use to recover nutrients and prevent nutrient loss. Biochar was used as a strategy to enhance phosphorus (P) recovery by improving total suspended solids (TSS) removal efficiency in the RBF system. This approach was further extended to include iron chloride (FeCl3) as a flocculant, which has potential to efficiently remove suspended solids as well as soluble phosphorus from wastewater.

Figure 1. Rotary belt filter removal of biochar and solids in anaerobic digest effluent.
Figure 1. Rotary belt filter removal of biochar and solids in anaerobic digest effluent.

To optimize P recovery, laboratory-scale experiments were conducted to evaluate biochar and iron chloride dosing rates. These experiments aimed to better understand the system’s performance and provide insights for pilot scale studies. The goal was to develop a lab setup that accurately represents field conditions and to identify cost-effective, practical solutions for large-scale applications.

What Did We Do?

Biochar dosing experiments were conducted using a jar test, in which 30 mL of AD dairy effluent was mixed with biochar (Biochar Now LLC., Loveland, Colorado) for 20 minutes at 200 rpm, with dosing rates of 1, 2, 4, 6, and 8 g/L. For the iron chloride dosing experiments, 6 g/L of biochar was mixed with the effluent for 20 minutes at 200 rpm, followed by the addition of iron chloride to achieve final concentrations of 0.25, 0.5, 1.0, and 2.5 g/L. The Fe-biochar mixtures were then stirred for 1 minute at 200 rpm and subsequently for 20 minutes at 40 rpm. After mixing, the samples were vacuum filtered using the same mesh of the rotating belt filter (112 mesh or 149 μm) on a 2” Buchner ceramic funnel. Since sedimentation time introduces variability to the flocculation process, a filtration setup was designed to allow simultaneous filtration of replicates. All experiments were performed in triplicate.

The solids retained on the mesh were collected, air-dried overnight, and digested using a modified dry ash method. Part of the filtrate was used for total suspended solids (TSS) analysis, while another portion was digested following the acid digestion method for sediments, sludges, and soils (EPA 3025B). The digested solid and filtrate samples were filtered through a 0.45 μm PES syringe filter and analyzed for elemental composition using an ICP spectrometer.

What Have We Learned?

The TSS of the AD dairy effluent can vary seasonally. In our experiments, the batch used contained approximately 25,000 mg/L of SS. The filtration system retains up to 15% of the SS when no biochar or Fe are amended to the AD.  The addition of 4 to 6 g/L of biochar increased TSS removal by 5%. However, higher biochar doses did not further enhance TSS removal efficiency.

Results indicated that most of the P in the AD dairy effluent is not in the soluble reactive form, which means that P removal in the rotary belt filter should be proportional to the TSS removal. Figure 2 shows the P concentration in the filtered effluent from the biochar dosing experiments, indicating that with biochar additions ranging from 2 to 8 g/L, the P concentration in the filtrate remains similar. Figure 3 shows that the P concentration in the solids decreased as the biochar dose increased. This is because the total mass of solids retained on the filter increased with the addition of biochar. These results showed that biochar has a dilution effect on P concentration because the phosphorus removal capacity of biochar during filtration is limited.

Figure 2. Total P concentration in the filtered effluent after biochar dosing experiments.
Figure 2. Total P concentration in the filtered effluent after biochar dosing experiments.
Figure 3. Total P concentration on solids retaining by filtration from the biochar dosing experiments.
Figure 3. Total P concentration on solids retaining by filtration from the biochar dosing experiments.

Figure 4 shows the P concentration on solids at different doses of FeCl3 added to 6 g/L of biochar. The results show that higher FeCl3 doses lead to higher P concentrations in the solids. Table 1 shows the relationship between FeCl₃ dosing rates and the estimated volume of iron chloride solution needed in a pilot scale field trial. With 6 g/L of biochar, achieving an increase in P concentration from ~3300 mg/L to 5000 mg/L would require 6 L/m³ of FeCl3 solution. pH adjustments would optimize iron promoted flocculation and significantly reduce the amount of iron dosing required, and thus process costs. However, due to the high buffering capacity of the AD effluent, large amounts of acid would be required, which would offset cost savings from the reduced iron amendment.

 

Figure 4. Total P concentration on solids retained by filtration from the FeCl3 dosing and 6 g/L biochar dosing experiments.
Figure 4. Total P concentration on solids retained by filtration from the FeCl3 dosing and 6 g/L biochar dosing experiments.
Table 1 – FeCl₃ dose and corresponding solution volume required in the field
Field scale
FeCl3 dose (g/L) FeCl3 (L/m3)
0 0
0.1 0.24
0.25 0.60
0.50 1.21
1.00 2.41
2.50 6.03

Future Plans

The next steps of this research are divided into two main topics. The first focuses on evaluating the effect of organic flocculants, such as chitosan and alginate, on TSS and phosphorus removal from the effluent. This includes analyzing their advantages and disadvantages compared to iron chloride. The second topic explores the oxidation of the effluent with ozone before flocculant addition. This approach aims to determine whether pre-oxidation can reduce the required flocculant dose per mg of TSS removed.

Authors

Presenting & corresponding author

Mariana C. Santoro, Postdoctoral researcher, Department of Soil and Water Systems, University of Idaho, marianacoelho@uidaho.edu

Additional authors

Daniel G. Strawn, Professor, Department of Soil and Water Systems, University of Idaho

Martin C. Baker, Research Engineer, Department of Soil and Water Systems, University of Idaho

Alex Crump, Research Scientist, Department of Soil and Water Systems, University of Idaho

Gregory Möller, Professor, Department of Soil and Water Systems, University of Idaho

 

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. 2025. Title of presentation. Waste to Worth. Boise, ID. April 7-11, 2025. URL of this page. Accessed on: today’s date.

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Impacts of Swine Carcass Preparation and Carbon Material on Effectiveness of Shallow Burial with Carbon (SBC)

Purpose

This project was conducted to increase our knowledge of the implications of using low-quality carbon feedstocks as the carbon layer within a Shallow Burial with Carbon (SBC) system. This system is also known as theTrench Composting and Above Ground Burial. SBC requires a 1-foot layer of carbon material in the bottom of the trench.  This carbon material serves three purposes: 1) absorbs and temporarily traps leachate released from the decomposing carcasses, 2) provides elemental carbon to the microorganisms that the system fosters to decompose carcasses, and 3) temporarily traps oxygen in the system.  To date, most applications of the SBC system have utilized wood products such as shavings, wood chips, and mulch. These products are generally effective at all 3 functions. While these carbon materials are successful feedstock for SBC, wood products are not widely available in parts of the country.

Regions with few woody carbon sources often have ready access to crop residues such as corn stover, rice hulls, straw, or hay.  These carbon feedstocks generally have a significantly lower carbon-to-nitrogen ratio than woody carbon sources.  For example, wood shavings typically have a C:N ratio of around 550:1 while the C:N ratio of straw is 100:1 or less. Materials with a higher C:N ratio may have more elemental carbon available for the metabolic activities of the microorganisms.  Crop residues tend to have a waxy cuticle layer that decreases their capacity to absorb leachate compared to woody materials.  Finally, crop residues tend to compress under the weight of the carcasses and the SBC system’s soil cover. This compression decreases the amount of oxygen trapped in the pore spaces between particles.  The degree to which these differences in the physical and chemical properties of woody products compared to crop residues impact their effectiveness as a carbon source in an SBC system has been unknown.

What Did We Do?

The study was conducted at the Horticulture Crops Research Station in North Carolina (Address: 2450 Faison Hwy, Clinton, NC 28328). This station is affiliated with NC Department of Agriculture and Consumer Services (NCDA&CS) and North Carolina State University (NCSU) is in the coastal plains region of North Carolina. The project site contained a weather station belonging to the state climate office (ECONET Station ID: CLIN) with continuous monitoring of primary weather variables such as air temperature, precipitation, wind speed, in addition to soil temperature, soil moisture content, and evapotranspiration.

Individual trenches were excavated for each treatment, ensuring each treatment combination (carbon material and carcass condition) was isolated to prevent cross-contamination. The placement of treatments was randomized to minimize bias and allow for a more rigorous comparison of outcomes. A total of 72 pigs of similar size were used, divided between whole and ground carcass treatments. Figure 1 below illustrates the site preparation.

Figure 1. Experimental site after excavating the individual plots and before carbon material placement
Figure 1. Experimental site after excavating the individual plots and before carbon material placement
Figure 2. (A) Carbon material after placement in plots: (1) hardwood mulch, (2) corn stover, (3) wheat straw, and (4) fescue hay;
Figure 2. (A) Carbon material after placement in plots: (1) hardwood mulch, (2) corn stover, (3) wheat straw, and (4) fescue hay;

Carcass decomposition was assessed using a five-point scale developed by Brown (2007), as adapted by Lochner et al. (2022) (Table 1). Observers scoring the decomposition were all trained and experienced carcass management subject matter experts, ensuring consistent and reliable assessments of carcass breakdown across all treatments.

Score Criteria
1 Large amounts of flesh, hide and hair present. Internal fluid is still visible. Carcass is still discernible.
2 Flesh, hide and hair are present in smaller amounts. Carcass is no longer discernible. No internal fluid visible.
3 Slight amounts of hair and hide present. Numerous large and small bones are present.
4 No hide present. Minimal hair visible. Flesh completely degraded and only large bones were present.
5 No flesh, hide, or hair present. Few to no large brittle bones present.

What Have We Learned?

Precipitation was analyzed in relation to evapotranspiration on a day-by-day basis. This was conducted by running a daily tally of precipitation less evapotranspiration for the entire study period; a positive value indicated a net water surplus (accumulation) while a negative value suggested deficit (or drying). Throughout the study period, the volumetric water content (VWC) fell between 25% and 35% which is close to the field capacity (FC) value for the site soil types. Collectively, these observations indicate the site soils experienced near-saturation conditions during the study period. Observers during each excavation activity reported noticeable soil wetness in the burial areas; but no pooled water.

Over the burial period, whole carcass decomposition was shown to gradually transition from a relatively low to higher decomposition score. Since these scores are ordinal but not continuous variables, we opted to avoid averaging them  avoiding confusion in interpretation.

The data indicates that all four carbon sources in this study (hardwood mulch, wheat straw, corn fodder, and fescue hay) provided an acceptable level of decomposition of whole swine carcasses after twelve months.  This trial used finishing hogs.  If larger breeding stock had been used the results may have been different.

Future Plans

Data analysis is ongoing to assess statistical significance in decomposition extent and ranking by observers. Also, downward movement associated with different treatments (different carbons, whole vs ground carcass) is currently being analyzed. Results provide guidance for site selection, carbon source screening, and relevant protective measures for water quality at the site. Future evaluation of the shallow burial with carbon (SBC) technology are planned in other sites/regions with results to be compared to this evaluation.

Authors

Presenting & corresponding author

Mahmoud Sharara, Associate Professor and Extension Specialist, Biological and Agricultural Engineering Department, North Carolina State University, Raleigh, North Carolina, msharar@ncsu.edu

Additional authors

Gary Flory, G.A. Flory Consulting LLC President, Director of Operations

Bobby Clark, Senior Extension Agent, Shenandoah County Office

Bob Peer, Agricultural Program Coordinator, Virginia Department of Environmental Quality

Mark Hutchinson, Professor Emeritus of Sustainable Agriculture, University of Maine Cooperative Extension

Acknowledgements

The authors would like to acknowledge Smithfield Foods for providing deadstock used in conducting this study. The authors also would like to acknowledge Hunter Barrier, Superintendent for the Horticultural Crops Research Station in Clinton, NC for providing space and resources needed for this work. The authors also would like to acknowledge Research Station crew for their timely support during project activities.

 

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. 2025. Title of presentation. Waste to Worth. Boise, ID. April 7-11, 2025. URL of this page. Accessed on: today’s date.

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