To access and quantify the availability of inorganic soil phosphorous following the application of dried non-living Cyanobacteria biofertilizer (CBF) in oats within a greenhouse environment
What Did We Do?
This study examined the operational and environmental effects of integrating Cyanobacteria biofertilizer (CBF) production into livestock manure management systems. Using a combination of system modeling, laboratory analysis, and field trials, the research assessed the life cycle environmental impacts and practical viability of Cyanobacteria biofertilizer (CBF).
What Have We Learned?
This presentation will provide insights into system configuration and modeled environmental impacts, as well as data from ongoing lab and greenhouse experiments. Key findings indicate that genetically modified strains of cyanobacteria (mutants) are capable of increasing manure phosphorus uptake by 10 times compared to existing strains. The shift to mutant cyanobacteria with greater phosphorus uptake results in reduced greenhouse gas emissions, as identified through a partial life cycle assessment, and can serve as a phosphorus fertilizer, as determined in greenhouse trials. Greenhouse trials on oat production using cyanobacteria with typical phosphorus uptake levels and the mutant strains with a 10-fold increase in phosphorus uptake produced similar biomass yields to dairy manure and increased biomass compared to chemical/synthetic fertilizers. Further research will expand to field trials for existing cyanobacteria strains, additional greenhouse trials for mutant strains, and efforts to increase nitrogen uptake in alternative mutant strains. . This study underscores both the potential and challenges of adopting CBF as a sustainable solution in livestock-based cropping systems.
Future Plans
We will be taking learnings from our initial laboratory/greenhouse experiments and modeling to field trials in Spring/Summer of 2025.
Authors
Presenting author
Brian M. Langolf, Researcher, University of Wisconsin Madison
Corresponding author
Rebecca A Larson, Professor and Extension Specialist, University of Wisconsin Madison, rebecca.larson@wisc.edu
Additional authors
Juma Bukomba, Gradúate Research Assistant, University of Wisconsin Madison; Horacio A. Aguirre-Villegas, Scientist, University of Wisconsin Madison; Brenda Casino Loeza, Research Associate, University of Wisconsin Madison; Victor M. Zavala, Professor, University of Wisconsin Madison; Ted Chavkin, Postdoctoral, University of Wisconsin Madison; Brian Pfleger, Professor, University of Wisconsin Madison; Rebecca A Larson, Professor, University of Wisconsin Madison
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.
Livestock producers and meat processors are facing ever evolving challenges when it comes to waste management. Increasing levels of regulation continue to challenge producers, including Washington State’s recently established Organics Management law which sets Methane reduction goals for landfills. This has led many landfills in the state to begin turning away organic material like offal and animal carcasses. Meanwhile climate change is increasing the frequency and intensity of catastrophic animal mortality events, driving the urgent need for solutions to build resources and infrastructure to manage large animal losses.
The Awful Offal group serves as the primary inter-agency effort for addressing policy barriers and problem-solving acute and ongoing animal waste disposal scenarios. The group and its members also participate in state-wide catastrophic mortality preparedness planning. This presentation aims to engage participants with real-world examples of successes and challenges this group has faced through its inception.
What Did We Do?
The Awful Offal work group meets regularly to update members on specific cases or trends in their respective programs. Over years of collaboration, we have been able to identify gaps, provide training and create resources to address some of the largest challenges the state faces with animal carcass management. This has taken shape in the form of offal focused composting workshops, market studies, and countless hours providing resources and technical assistance to operators in need.
What Have We Learned?
We have learned much since this group’s inception, one thing that routinely comes up is that Washington’s diverse climate is going to require an equally diverse set of solutions for tackling this challenge. Composting is a viable and environmentally responsible option for many but also comes with its own unique needs and challenges. Many small meat processors have described the switch from sending material to landfill to composting onsite as “running a second business.” If you also consider many commercial composting operations do not accept this material, we must recognize that no single solution will solve this issue state-wide.
Future Plans
Through robust technical assistance and economic incentives, Washington State Department of Agriculture (WSDA) plans to lead a State-wide effort to promote adoption of on and off-farm composting as a waste management strategy. WSDA also intends to conduct an in-depth economic and market analysis to identify the specific regional needs and barriers so to further determine how the State can best support additional infrastructure, fund pilot projects and develop resources.
Authors
Presenting author
AJ Mulder, Nutrient Management Specialist, Washington State Department of Agriculture, aj.mulder@agr.wa.gov
Acknowledgements
I would like to acknowledge all the members of the Awful Offal work group, including my colleagues at Washington State Department of Agriculture, Department of Ecology, Washington State University, Department of Health, Department of Fish and Wildlife, USDA and all our industry partners whose input and cooperation this work would be impossible without.
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.
Conservation and recovery of nitrogen (N) and phosphorus (P) from livestock, industrial, and municipal effluents are important for economic and environmental reasons. Therefore, a need exists for improved systems and methods for N and P recovery from wastewater, especially by using fewer chemicals. A new method was developed using electrochemistry to enhance the gasification and rate of ammonia capture by a gas-permeable membrane and the solubilization and the rate of phosphate capture using P-precipitating compounds. The process was tested using liquid swine manure. It recovered 86% of the ammonia and more than 93% of the phosphorus contained in the manure.
What Did We Do?
This work aimed to develop new technology for simultaneous N and P recovery that eliminates alkali chemicals used to increase pH for quick N capture using gas-permeable membranes (Vanotti and Szogi, 2015), and also eliminates acid chemicals used to solubilize the P in the manure before precipitation with P-precipitating agents (Szogi et al., 2018). The new N and P recovery system used in this example is described by Vanotti et al., 2024. It has a cathode chamber, an anode chamber, a stripping acid solution tank, and a phosphorus recovery tank (Fig. 1). The cathode chamber is fitted with a gas-permeable membrane manifold. The cathode chamber is fitted with a gas-permeable membrane manifold and contains a salt solution. The wastewater containing ammonia and phosphorus is pumped into the anode chamber. The ammonium (NH4) in the anode chamber permeates into the cathode chamber through a cation exchange membrane placed between chambers. The cathode increases the pH of the liquid and accelerates the rate of passage of ammonia through the gas-permeable membrane into an acid-stripping solution contained in a stripping tank/ reservoir and recirculated through the membrane manifold in a closed loop. The wastewater in the anode chamber is acidified by H+ released by electrolysis in the anode. The anode chamber effluent, with most of the P solubilized, is passed through a centrifuge or filter to separate suspended solids without phosphorus and liquid filtrate/centrate with phosphate. Phosphorus precipitating compounds used were MgCl2 and Ca(OH)2. After rapid mixing, the phosphorus precipitates as a solid. This precipitation proceeds quickly as a result of the previous removal of the carbonate alkalinity in the anode chamber, which interferes with phosphate precipitation.
Figure 1. Schematic diagram of an embodiment of a nitrogen (N) and phosphorus (P) recovery system using electrochemistry (Vanotti et al., 2024).
What Have We Learned?
In tests with liquid swine manure, the pH in the cathode chamber was increased due to the electrochemical production of OH-, from 5.8 to 12.5 (Fig. 2). The wastewater’s ammonia was removed from the anode chamber and recovered in the stripping acid solution with 86% recovery efficiency (Fig. 3).
Figure 2. pH in anode chamber, cathode chamber, and stripping acid tank.Figure 3. Ammonia-N mass removal in anode chamber and ammonia-N mass recovery in cathode chamber and stripping acid tank.
The wastewater pH in the anode dropped from 7.9 to 3.5, and carbonate alkalinity dropped from 10750 mg/L to 0 mg/L (Figures 2 & 4). The acid was produced by oxidation at the anode (2 H2O → O2 + 4 H+). These conditions transformed the P from manure particles into soluble phosphates that were efficiently recovered in the phosphorus recovery tank. For example, using the P-precipitating compound Ca(OH)2, the process recovered 93% of the total P in a P precipitate solid compared to only 4.6% in a control without electrochemical treatment (Fig. 5). Using the P-precipitating compound MgCl2, the process recovered 95% of the total P in a P precipitate solid compared to only 6% P recovery in a control without electrochemical treatment (Fig. 5).
Figure 4. Reduction of carbonate alkalinity concentration occurring in the anode chamber.Figure 5. Phosphorus is recovered in the solid precipitate using P-precipitating compounds Ca(OH)2 or MgCl2. A) with a previous electrochemical step, and B) without an electrochemical step.
Future Plans
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
M.B. Vanotti, A.A. Szogi, P.W. Brigman, and S. Rawal, United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Coastal Plains Soil, Water and Plant Research Center, Florence, South Carolina.
Additional Information
Szogi A.A., Vanotti, M.B., Shumaker, P.D. 2018. Economic recovery of calcium phosphates from swine lagoon sludge using Quick Wash process and geotextile filtration. Frontiers in Sustainable Food Systems 2, 37, https://doi.org/10.3389/fsufs.2018.00037.
Vanotti, M.B., and Szogi, A.A. 2015. Systems and methods for reducing ammonia emissions from liquid effluents and recovering ammonia. U.S. Patent 9,005,333 B1. U.S. Patent and Trademark Office.
Vanotti, M.B., Szogi, A.A., Brigman, P.W., and Rawal, S. 2024. Systems for treating wastewater using electrochemistry. U.S. Patent Appl. 18/808,123. U.S. Patent and Trademark Office
Acknowledgements
This research was part of USDA-ARS National Program 212, ARS Project 6082-12630-001-00D. 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.
Animal manure is frequently applied to crop fields to supplement manufactured fertilizers, as manure is rich in many of the nutrients required for plant growth. Most nutrients in manure exist in organic forms, which must first be mineralized to inorganic forms before they can be used by plants. Direct land application of manure relies on in situ mineralization of nutrients by soil microorganisms, which is a slow and difficult-to-control process. In anticipation of limited immediate nutrient availability, manure is often applied to fields in excess of actual agronomic nutrient need. The excess nutrients can leach into water sources, causing accelerated eutrophication and threatening human and ecosystem health. As such, it is advantageous to investigate technologies designed to recover manure nutrients in inorganic forms, which can then be more easily regulated and applied to suit specific agricultural demand. Bioelectrochemical systems (BES) are a novel treatment option employing electrogenic microorganisms to drive operation and recover mineralized nutrients, making them an advantageous resource recovery mechanism.
What Did We Do?
This study investigated a BES for organic nitrogen mineralization and ammonia recovery from synthetic (e.g. prepared solution of organic nitrogen and acetate) and real dairy manure. The BES was custom fabricated and followed a two-chamber design as outlined in Burns and Qin (2023). Briefly, a cation exchange membrane separated a biological anode and chemical cathode in respective chambers. Electrodes were connected via a 10 Ohm resistor to allow for current flow, and synthetic or real dairy manure was fed to the biological anode depending on the experimental condition under investigation. The BES was operated in both fuel cell and electrolysis cell (applied voltage = 0.8 V) modes.
Figure 1. Schematic of the bioelectrochemical system used to treat dairy manure and produce ammonia fertilizer.
System performance was evaluated for organics removal (measured as chemical oxygen demand or COD), nitrogen removal, and total ammoniacal nitrogen production. We also calculate the nitrogen removal efficiency, RN, which measures how current is partitioned to drive nitrogen transport (as NH4+) across the cation exchange membrane. We modeled full-scale implementation of this technology on a theoretical Wisconsin dairy farm based on the experimental results obtained when treating real dairy manure. Results from the model (functional unit: tonne of manure treated, allocation: kg fat-and-protein-corrected milk (FPCM)) were used to investigate environmental impacts including greenhouse gas (GHG) emissions (in kg CO2eq tonne-1 manure), ammonia losses (in kg NH3 tonne-1 manure), and eutrophication potential (kg PO42- tonne-1 manure).
What Have We Learned?
In synthetic manure experiments, the BES consistently achieved excellent organics removal, exhibiting COD removal efficiencies well above 90%. Furthermore, total nitrogen removal efficiency averaged around 40% in electrolysis cell operation, and was seen to reach as high as 60% for some experiments. In fuel cell operation, nitrogen removal efficiency was decreased, averaging around 23%, indicating a slight advantage for nitrogen removal in electrolysis operation. RN exhibited interesting trends before, during, and after electrolysis cell operation. For the same system operational parameters, RN in fuel cell mode was around 1 mol N mol-1 electrons before electrolysis cell operation. However, during electrolysis operation and when the system returned to fuel cell operation after electrolysis cell operation, RN was and remained elevated at nearly 3 mol N mol-1 electrons with much more variability. This variability suggests that the microbial community was less tolerant to applied voltage conditions, and that there was perhaps some significant change during electrolysis operation that was difficult to recover from upon return to fuel cell operation. When treating real dairy manure, the system achieved average removals of 60% of total nitrogen and 58% of organic matter (Burns et al., 2024). The system exhibited similar nitrogen removal across multiple dairy manure feedstocks, however, a decrease in RN was observed with more complex dairy manure feedstock, likely due to the presence of competing ions (Burns et al., 2024).
Figure 2. Radar plots showing greenhouse gas emissions, ammonia losses, and eutrophication potential of three manure treatment scenarios: no processing/direct land application, solids-liquids separation (SLS), and microbial fuel cell (MFC) treatment for both surface and injection application of products. Results are reported per tonne of manure treated with an allocation of fat and protein corrected milk (FPCM).
We also investigated the environmental impacts of BES manure treatment when scaled up to a ~730 cow dairy farm. Impacts on greenhouse gas emissions, ammonia losses, and eutrophication potential were compared for surface and injection application of three manure treatment scenarios: (1) no manure treatment or processing, (2) solids-liquids separation (SLS) manure processing, and (3) BES manure treatment. Preliminary results from the model reported that BES manure treatment decreased impacts in all three categories when compared to the no treatment scenarios, and resulted in less ammonia loss when compared to the SLS treatment scenarios (Figure 2). For GHG emissions, BES manure treatment had slightly increased emissions when compared to SLS, mostly due to the added energy and freshwater inputs. However, BES manure treatment received more credits for P and N-based fertilizers than SLS treatment. For eutrophication potential, BES manure treatment had slightly less impact when compared to SLS treatment, despite the added impacts of freshwater, energy, and supplemental chemicals required for the treatment. Based on these results and those from experimental data, BES manure treatment is concluded to be a promising and competitive technology worthy of further development.
Future Plans
The results of this research prove bioelectrochemical systems to be a viable manure treatment alternative to current technologies. Our future work will involve investigating the organic nitrogen degradation kinetics in the BES treating dairy manure. Our goal is to determine reaction rate orders and calculate kinetic constants for degradation of COD, TN, and organic N within the cell, which can be used to develop more accurate full-scale models of the process. This analysis can be extended to investigate differing compositions of dairy manure based on the dairy’s variable feed compositions throughout the year. Additionally, we plan to expand the environmental impact analysis to include two other comparison scenarios which would be realistic at the industrial scale: (1) minimizing freshwater inputs for manure dilution and (2) harvesting electricity produced by the BES towards meeting pumping and aeration demands. Based on the model, BES manure treatment would require approximately 1,700 kWh of electricity per week to meet pumping an aeration demands, some of which can be provided by the microbially-generated electric current in the system. Furthermore, due to reactor size constraints at the lab scale, there is currently a large amount of freshwater used to dilute the manure prior to treatment with the MFC. This work will help to contextualize BES within existing manure treatment frameworks and will help both researchers and practitioners make informed decisions regarding manure treatment options.
Authors
Presenting author
McKenzie Burns, PhD Candidate, the University of Wisconsin—Madison
Corresponding author
Dr. Mohan Qin, Assistant Professor, the University of Wisconsin—Madison, mohan.qin@wisc.edu
Additional authors
Dr. Horacio Aguirre-Villegas, Scientist III, the Nelson Institute for Environmental Studies at the University of Wisconsin—Madison
Dr. Rebecca Larson, Associate Professor, the University of Wisconsin—Madison
Additional Information
Published journal articles (these are also the citations for this conference proceeding):
The authors would like to thank the support from National Science Foundation CBET 2219089. In addition, the authors would like to thank the startup fund from the Department of Civil and Environmental Engineering, College of Engineering, the Office of the Vice-Chancellor for Research and Graduate Education (OVCRGE) at the University of Wisconsin–Madison, and the Wisconsin Alumni Research Foundation (WARF) for the support of this study. The authors gratefully acknowledge support from Jackie Cooper of the Environmental Engineering Core Facility at the University of Wisconsin–Madison for use of facilities and equipment. Finally, the authors thank Andrew Beaudet, Ethan Napierala, Katie Mangus, and David Xiong for their contributions as undergraduate researchers on this project.
The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2025. Title of presentation. Waste to Worth. Boise, ID. April 7–11, 2025. URL of this page. Accessed on: today’s date.
Bio-based biodegradable plastics led by polylactic acid (PLA) are becoming increasingly popular as a sustainable alternative to traditional plastics. Although bioplastics are designed to break down easily, many do not fully degrade in the natural environment as intended. Anaerobic digestion (AD) is a promising solution for decomposing bioplastics alongside food waste, turning them into biogas for energy and digestate, rich in nutrients, that can be used as fertilizer. However, studies have shown that bioplastics, particularly PLA, does not degrade fully in AD systems. The byproducts left over from AD raise serious problems, especially if residual microplastics could still be present in the digestate and affect the quality of the soil and water. While existing research predominantly focuses on enhancing methane production and biodegradation efficiency during AD, the quality of digestate after the digestion process has been overlooked. This significant research gap was highlighted in this review, emphasizing the need for comprehensive studies that evaluate digestate composition alongside biogas production.
What Did We Do?
A systematic review of peer-reviewed studies was conducted using databases such as Scopus, ScienceDirect and Google Scholar to assess research on bioplastic degradation in anaerobic digestion. The literature search was performed using the keywords ‘bioplastic degradation’, ‘pretreatment methods,’ ‘Anaerobic digestion,’ ‘biodegradation,’ ‘biogas production’ and ‘digestate quality’. Search filters were applied to prioritize recent studies (2010-present), peer-reviewed journal articles, and experimental studies analyzing bioplastic degradation and digestate quality. The initial search yielded 172 papers, which were then screened for relevance based on their focus on bioplastic degradation, biogas production, and digestate analysis. After filtering out studies that were not directly related, 42 papers were selected for detailed analysis. A significant portion of the literature examined the effectiveness of different pretreatment methods in improving bioplastic degradation. These methods included but not limited to thermal pretreatment, where the plastics are exposed to elevated temperatures to increase its hydrolysis potential; alkaline pretreatment, which involves chemical treatments to enhance polymer degradation; and thermo-alkaline pretreatment, a combination of heat and chemical treatment to increase its susceptibility to decomposition. This allowed us to assess the extent to which bioplastic degradation has been addressed and the incomplete degradation persisting, highlighting the need for more comprehensive studies into the digestate quality.
What Have We Learned?
Studies consistently showed that bioplastic, especially PLA, degradation in AD remains incomplete in most cases, leading to concerns about the accumulation of microplastics residues in digestate. While pretreatment methods have been effective, with thermo-alkaline pretreatment yielding the highest methane outputs across most studies. The variability in methane yields across different pretreatment conditions suggests that degradation efficiency is highly dependent on factors such as temperature, retention time, microbial communities, and chemical additives. However, very few studies have explicitly analyzed whether residual bioplastic particles persist in the digestate post-AD. Given that AD is promoted as a promising solution for sustainable plastic waste solution, failing to assess digestate composition may lead to unintended environmental consequences. The implications of these findings are significant, particularly for large-scale implementation. If AD-derived digestate is to be used in agriculture or soil restoration, it must be free of persistent microplastics. Without comprehensive digestate analysis, the environmental benefits of AD for bioplastic waste management remain uncertain.
Future Plans
We are currently conducting an experimental study to evaluate the degradation of PLA in AD under different pretreatment conditions – thermal, alkaline, and thermo-alkaline treatments – to enhance PLA degradation and improve methane yields. More importantly, we aim to go beyond methane production by analyzing the resulting digestate for microplastic residues and overall chemical composition. Future studies will involve optimizing pretreatment strategies to minimize microplastic residues and investigating the long-term impacts of digestate when applied to soil systems.
Authors
Presenting & corresponding author
Nadia Bawa Fio Bekoe, Graduate Research Assistant, Biosystems and Agricultural Engineering Department, Oklahoma State University, nbekoe@okstate.edu
Additional author
Douglas W. Hamilton, PhD, P.E., Associate Professor and Extension Waste Management Specialist, Biosystems and Agricultural Engineering, Oklahoma State University
Acknowledgements
South Central Sun Grant Program Fellowship
Livestock & Poultry Environmental Learning Community (LPELC) Professional Development Grants
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.
The overall objectives of this research are to describe the current linkages among participants in the dairy manure compost supply chains in the Pacific Northwest (PNW) states of ID, OR, and WA and to provide analytical insights into the challenges and opportunities for enhancing manure compost marketability and usage in the different regions. Obtaining an enhanced understanding of these market dynamics is necessary for explaining why and how dairy compost quality varies and for identifying strategies for establishing and/or strengthening linkages among market participants. Improving dairy compost quality and increasing usage among crop producers is important for achieving sustainable environmental quality and agricultural business profitability in all PNW states.
What Did We Do?
Our analysis builds on the underlying concept that is outlined in Extension bulletins and other references from universities in the PNW (e.g., Chen et al. 2011), which emphasize that developing good quality dairy manure-based compost requires achieving a proper Carbon (C) to Nitrogen (N) ratio (C:N) of about 30:1. It is common that supplemental C is needed to increase the C:N balance in dairy manure-based compost to that magnitude. There are various sources of supplemental C used by PNW compost producers, but the most common are cereals (barley and wheat) straw, corn stalks/silage, sawdust, and wood chips.
We created Figure 1 to describe, with several assumptions, the major participants in the PNW dairy compost supply chains and the nature of their typical interactions with each other. The main participants include dairies, compost businesses, logging businesses, cereals farms, laboratory testers, and silage farmers. We next implemented data-driven analyses to determine if and the extent to which the linkages among the dairy compost supply chain participants differ across PNW states, based on the structure of the dairy and other aligned industries (e.g., logging) in each state. The principal objective of the analyses was to quantify the relative spatial concentration of the dairy industries, which has implications for business profitability and policy-driven incentives for implementing the composting process. We used a couple of different measures of dairy market concentration for comparison. The first is the Herfindahl-Hirschman Index (HHI), which is a statistical measure of industry concentration (Rhoades, 1993). We applied the calculation of the HHI in a manner that is different than is typically done such that the obtained values represent differences in the spatial concentration of the dairy industries in ID, OR, and WA. We supplemented the HHI values with calculations of the ratios of dairy cow inventories to cropland acreage. Lastly, to obtain insights about the relative strengths of linkages among potential dairy compost supply chain entities, we estimated the correlation between county level dairy cow inventories, cropland acreage, and the numbers of other entities (e.g., logging businesses) for each state.
Figure 1. Diagram of major PNW dairy compost supply chain linkages (Source: Authors)
What Have We Learned?
The estimated HHI values in our context could range from close to about 100, which would reflect an even distribution of dairy cows among all counties in a state, to 10,000, which would imply that all dairy cows are in a single county. Our estimated HHI values based on 2022 data from the USDA Census of Agriculture were 1,378 for ID, 2,307 for OR, and 2,082 for WA. Thus, by the HHI measure, the dairy industries in OR and WA are more spatially concentrated than that in ID. However, by the ratio of dairy cow inventory to cropland acreage measure, all states have counties with relatively high concentrations of dairy cows, but to different extents across states. Additionally, estimates from the correlation analysis at the county level show a positive relationship between dairy cow inventories and cropland acreage for all states (statistically significant at the 5% confidence level for OR). A negative, but not statistically significant, relationship was found between the number of logging businesses and dairy cows in all states, but the magnitude was largest in ID. Thus, it is more common that counties have both dairy cows and logging businesses in a county in OR and WA than in ID. These relationships help explain why wood-based amendments with higher C are likely more commonly used in the composting process in OR and WA than in ID, as well as how the associated compost qualities differ across states.
Future Plans
The analyses we have implemented so far are at the county level. We plan to implement additional analyses that include identifying larger multi-county dairy producing regions and compiling more data on the existing supply chain participants, including cropland acreage for other crops (i.e., non-grain and silage) in such regions. This expanded analysis will provide more regionally specific assessments of the differences in dairy compost components/quality among the major dairy producing regions in the PNW.
Authors
Presenting & corresponding author
Patrick Hatzenbuehler, Associate Professor and Extension Specialist – Crop Economics, University of Idaho, phatzenbuehler@uidaho.edu
Additional authors
Srijan Budhathoki, Graduate Student, Washington State University
Mario de Haro-Martí, Extension Educator – Gooding County, University of Idaho
Anthony Simerlink, Extension Educator – Power County, University of Idaho
Research funding was provided by USDA-NIFA Sustainable Agricultural Systems Grant No. 2020-69012-31871 and the Idaho Agricultural Experiment Station.
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.
Advanced manure processing technologies offer the potential to enhance the sustainability of these systems by separating manure into various streams for more efficient post-processing management. This presentation will synthesize findings from multiple full-scale studies on manure processing systems, focusing on separation technologies. It will also include recent evaluations of systems designed to treat manure to a quality suitable for discharge into surface waters. The data presented will cover separation efficiencies of key components, system performance, operational challenges, barriers to adoption, and the results of life cycle assessments of the environmental impacts when integrated into dairy facilities. These insights can provide valuable guidance for producers and stakeholders on how to integrate these systems effectively to achieve targeted environmental and operational outcomes.
What Did We Do?
A number of full-scale manure separation systems were analyzed over time to assess the nutrient separation efficiency of each component. This included systems from previously published data as well as two new sites analyzed in 2024-2025.
Site 1. A total of 45 manure samples were collected over 37 weeks from the Aqua Innovations treatment system located in Middleton, WI. Samples were collected from the (1) influent manure (following digestion), the (2) separated solid (screw press)and (3) liquids from the separator (screw press), (4) separated solid (centrifuge), (5) liquids from separator (centrifuge), (6) ultrafiltration (UF) concentrate and, (7) UF treated liquid, and the (8) reverse osmosis concentrate, and (9) clean water discharged.
Site 2. Samples were also collected from a dairy with a Livestock Water Recycling system located in Kiel, WI. Similarly, samples were collected over 45 sampling events from (1) liquid influent entering the inclined screen/roller press (raw manure), (2) liquid effluent following the inclined screen/roller press, (3) solids following the polymer assisted inclined screen/roller press, (4) liquid effluent following polymer assisted inclined screen/roller press, (5) outflow from clarifier, (6) liquid effluent following reverse osmosis (“clean” water), and (7) nutrient concentrate following reverse osmosis.
Samples were collected and shipped to Great Lakes Labs after each week of sampling and manure analyzed for manure total solids (or dry matter), total phosphorus, total nitrogen, ammoniacal nitrogen, potassium among many other sample parameters. Nutrient separation efficiencies were then compared for the entire system and each system component to previously collected data and data reported in literature.
What Have We Learned?
Separation efficiencies vary significantly for each nutrient through the system. Mutiple separation systems in series reduce variability in separation efficiency. Manure nitrogen is primarily removed from advanced treatment components, ultrafiltration and reverse osmosis, while solids and phosphorus are primarily removed in the initial separation stages.
Future Plans
Data will be further analyzed and published in a peer-reviewed journal. The data will also be integrated into a partial life cycle assessment to determine the impact to various environmental impact categories. This will be useful in aiding farmers in selecting processing systems for targeted outcomes in terms of nutrient separation and environmental outcomes.
Authors
Presenting & corresponding author
Rebecca A. Larson, Professor, Nelson Institute for Environmental Studies, University of Wisconsin-Madison, rebecca.larson@wisc.edu
Additional author(s)
Tyler Liskow, Engineer, Nelson Institute for Environmental Studies, University of Wisconsin-Madison; Brian Langolf, Researcher, Nelson Institute for Environmental Studies, University of Wisconsin-Madison; and Horacio Aguirre-Villegas, Scientist, Nelson Institute for Environmental Studies, University of Wisconsin-Madison
Newtrient and the USDA NRCS Conservation Innovation Grants for the funding to complete system sampling.
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.
The purpose of the ManureTech Decision-Support Tools (DST) for Dairy and for Swine is to assist farmers, consultants, and others in the dairy/swine industry in optimizing the management of manure from collection to land application. By providing data-driven recommendations based upon customizable inputs and priorities, the ManureTech DST help users make informed decisions about manure management systems in consideration of the economic, environmental, and operational needs of farm management.
What Did We Do?
A multi-state team has developed Excel-based decision-support tools for selecting technology and systems for managing manure on dairy and swine operations as part of a USDA NIFA-funded project.
During this workshop, participants will be introduced to the ManureTech DST for Dairy and the ManureTech DST for Swine and will be provided with hands-on training in using the decision-support tool for dairy. Major aspects of the tools that will be addressed in the workshop include an introduction to the user interface; entering primary inputs; prioritization of economic, environmental, and operational metrics; and reporting of results, including the ranking of manure system scenarios.
What Have We Learned?
In terms of learning, this effort has provided the project team with a fuller grasp of the complex nature of manure management! In terms of accomplishments, the team has assembled a tool that considers the multi-faceted benefits and challenges of various manure management systems and presents users with a ranked list of systems for consideration, which should help expedite and enhance system selection. Users of the ManureTech DST can provide farm-specific weight to economic, environmental, and operational criteria which allows ManureTech DST to rank alternative manure management scenarios in close alignment with individual priorities.
This visual illustrates what a user of the ManureTech Decision-Support Tool sees when weighing economic, environmental, and operational priorities of a farm, so that the rankings of the manure management systems reflect these farm priorities. In the illustrated case, the user preferences favor economic priorities over others.
Future Plans
Future plans include completing beta testing / pilot-testing of the ManureTech DST and conducting additional training on using the tool. Over a longer-range timeframe, the team would like to add some additional specialized capabilities and functionality, as a phase II effort.
Authors
Presenting authors
Erin Scott, Project/Program Manager, University of Arkansas
Varma Vempalli, Wastewater Treatment Specialist, City of Meridian (ID)
Jacob Hickman, Systems Analyst, University of Arkansas
Rick Stowell, Extension Specialist in Animal Environment, University of Nebraska-Lincoln
Teng Lim, Extension Professor and Engineer, University of Missouri
Corresponding author
Rick Stowell, Extension Specialist in Animal Environment, University of Nebraska-Lincoln, Richard.Stowell@unl.edu
Additional authors
Erin Scott, Project/Program Manager, University of Arkansas
Jacob Hickman, Systems Analyst, University of Arkansas
Jennie Popp, Associate Dean and Professor, University of Arkansas
Varma Vempalli, Wastewater Treatment Specialist, City of Meridian (ID)
Greg Thoma, Director of Agricultural Modeling and Lifecycle Assessment, Colorado State University
Teng Lim, Extension Professor and Engineer, University of Missouri
The authors acknowledge funding from the USDA NIFA AFRI Water for Food Production Systems program, grant #2018-68011-28691.
The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2025. Title of presentation. Waste to Worth. Boise, ID. April 7–11, 2025. URL of this page. Accessed on: today’s date.
This study assesses the economic and air quality benefits of using chipped apple orchard wood as a carbon source in a vermifiltration wastewater system. Instead of burning orchard debris, which releases harmful pollutants, the Perca system repurposes it as a substrate for earthworm-microbial wastewater treatment. The study also compares apple wood chips to traditional conifer chips, evaluating their effectiveness and the broader environmental and economic advantages of diverting orchard waste.
What Did We Do?
Image 1. Chipping process of apple orchard tear-out debris using Morbark, Eeger Beever, 1621” x 18”x 20.5” feeder throat with 140 horsepower motor.
Apple orchard tear-out debris from a local orchard was collected, chipped, and transported for installation as a substrate for the Perca vermifiltration system. Debris was screened to remove foreign materials, chipped to less than ½ inch size, and weighed to calculate tons of usable wood per ton of orchard debris. Data from processing, including chipping costs and labor requirements, were used to assess economic feasibility and air quality impact. In addition, a bench-scale test was conducted to evaluate the efficacy of wastewater treatment by apple orchard chips when compared to the standard conifer chips used in the Perca vermifiltration system. Removal efficiencies of total suspended solids (TSS), biological oxygen demand (BOD), and polychlorinated biphenyls (PCBs) were measured for both substrates.
Image 2. Example of foreign objects (wire) embedded in apple wood pieces.
Market projections for Perca’s vermifiltration system show a compound annual growth rate (CAGR) of 113.45%, reaching 9.57% of the market over the next five years. Calculated market projection estimates over 16,000 tons of orchard debris could be converted into a value-added substrate product rather than burning. This shift could eliminate more than 500 tons of emissions between 2025 and 2029. Economic analysis shows that while chipping costs and wood size restrictions pose challenges for trellised orchards, non-trellised orchards offer better yields and lower costs, with market trends and technology advancements pointing toward broader economic feasibility. Bench-scale tests showed that both apple wood and conifer substrates effectively reduced TSS, BOD, and PCBs by more than 80% in all categories with no significant difference in performance, confirming apple debris works as well as conifer media. These findings demonstrate that apple orchard debris provides an environmentally sustainable alternative to burning, thus contributing to improved air quality, while also an efficient, cost-effective vermifiltration substrate for wastewater treatment.
Image 3. Pine media and apple orchard tear-out fines.Image 4. Rapid Assay Vermifiltration System (RAVS) used to test wastewater contaminant removal capability in traditional (pine) media and apple orchard tear-out fines.
Future Plans
Ongoing efforts focus on refining the use of apple orchard debris to create a cost-effective, reliable wood chip that matches or exceeds current substrates in reducing conventional and nonconventional wastewater pollutants, while offering an economic alternative to burning. Additionally, strategies are being developed to integrate vermifiltration into regenerative agriculture and circular bioeconomy practices by repurposing spent substrate as a nutrient-rich soil amendment or for soil remediation. This approach transforms agricultural waste into multiple value-added resources, supporting both environmental sustainability and economic viability through continued innovation, collaboration, and stakeholder engagement.
Authors
Presenting & Corresponding author
Sierra J. Smith, Director of Research and Development, Perca, Inc., sierrasmith@perca.net
Additional authors
Joseph S. Neibergs, Professor Extension Economist and Director Western Center for Risk Management Education, Washington State University
George A. Damoff, Chief Science Officer, Perca, Inc.
David A. Elmenhurst, Chief Financial Officer, Perca, Inc.
Washington State Department of Ecology for funding and support
Washington State Agricultural Burning Practices & Research Task Force, under direction of the Department of Ecology, for funding and support
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.
Dairy farms employing flushing systems often encounter significant challenges in managing substantial volumes of recycled water, which can have environmental, economic, and operational implications. This study aims to evaluate a multi-stage process designed to improve solid/nutrient extraction from flushed water already treated by a pull-plug sediment basin system.
What Did We Do?
We implemented a three-stage sequential treatment process comprising coagulation, Fenton oxidation, and membrane filtration. In the first stage, coagulation was performed using aluminum sulfate (Al₂(SO₄)₃) to remove colloidal solids from the treated barn flushing water. The optimal alum dosage (500–7,000 mg/L) was determined based on turbidity, total solids, and chemical oxygen demand (COD) removal.
The second stage involved Fenton oxidation, where hydroxyl radicals generated from hydrogen peroxide (H₂O₂) and an iron catalyst (Fe²⁺) further degraded organic pollutants. Utilizing response surface methodology (RSM), we optimized the concentrations of H₂O₂ (500–1,800 mg/L), FeCl₃ (250–950 mg/L), and reaction time (15–50 min) to achieve a balance between treatment effectiveness and cost efficiency.
In the final stage, ultrafiltration and reverse osmosis were employed to remove dissolved ions, ensuring compliance with discharge standards.
What Have We Learned?
Fig. 1. Removals of turbidity (a), total solid (b), COD (c), and impacts on pH (d) at various alum treatment concentrations.
The results indicated that turbidity removal peaked at a dosage of 5,000 mg/L of Al₂(SO₄)₃, while total solids and COD removal stabilized at 4,000 and 5,000 mg/L, respectively. Although turbidity initially increased following the coagulant addition, the formation of aluminum hydroxide flocs facilitated effective pollutant removal. To balance reagent costs and treatment efficiency, a dosage of 4,000 mg/L alum was selected. After coagulation, the coagulated supernatant underwent fenton oxidation.
Turbidity removal (%)
Fig. 2. The removal of turbidity (%) at the interactions between H2O2 and FeCl3 (a), between H2O2 and time (b), and between FeCl3 and time (c).
Response surface analysis confirmed that optimal turbidity removal was achieved with H₂O₂ concentrations of 1,280-1,800 mg/L and FeCl₃ concentrations of 550-950 mg/L. Furthermore, a minimum mixing of 36 minutes was necessary to attain maximum efficiency.
Total solid removal (%)
Fig. 3. The removal of total solid (%) at the interactions between H2O2 and FeCl3 (a), between H2O2 and time (b), and between FeCl3 and time (c).
For total solids removal, effective interaction was observed at H₂O₂ levels of 500–1,240 mg/L and FeCl₃ concentrations of 250–450 mg/L. Mixing times exceeding 43 minutes were found to reduce removal efficiency.
COD removal (%)
Fig. 4. The removal of COD (%) at the interactions between H2O2 and FeCl3 (a), between H2O2 and time (b), and between FeCl3 and time (c).
COD removal was most effective within the H₂O₂ range of 500–760 mg/L and FeCl₃ concentrations of 450–950 mg/L, while mixing time had minimal impact.
Cost ($)
Fig. 5. The treatment cost ($) at the interactions between H2O2 and FeCl3 (a), between H2O2 and time (b), and between FeCl3 and time (c).
Regarding treatment cost, H₂O₂ was identified as the most influential cost factor due to its higher price. To balance removal efficiency and cost, the optimized conditions were determined as 563.3 mg/L H₂O₂, 568.4 mg/L FeCl₃, and a 33-minute reaction time, according to the calculations of RSM model. This setup achieved 86.4% turbidity removal, 18.7% total solids removal, and 81.5% COD removal at a treatment cost of $0.03 per liter of wastewater.
Future Plans
The next phase of the study will focus on membrane filtration experiments to further remove dissolved ions and ensure compliance with discharge standards. Additionally, a systematic economic analysis will assess cost-effectiveness, scalability, and operational feasibility for large-scale dairy farm applications.
Authors
Presenting author
Moh Moh Thant Zin, Post-doctoral researcher, University of Missouri-Columbia
Corresponding author
Teng-Teeh Lim, Extension Professor, University of Missouri-Columbia, limt@missouri.edu
Acknowledgements
Funding is provided by USDA-NIFA, grant award (2018-68011-28691) and University of Missouri Extension.
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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