For centuries, animal manure has been recognized as a soil “builder” because of its contributions to improving soil quality. Environmental benefits are possible from manure application if manure and manure nutrients are applied and timing and placement follows best management practices. When compared to more conventional fertilizer, manure properly applied to land has the potential to provide environmental benefits including:
Increased soil carbon and reduced atmospheric carbon levels
Reduced soil erosion and runoff
Reduced nitrate leaching
Reduced energy demands for natural gas-intensive nitrogen(N) fertilizers
Manure is comparable to commercial fertilizer as a plant food and, if applied according to a sound nutrient plan, has environmental benefits over commercial fertilizer. cc2.5 manure nutrient management group
Several long-term manure application studies have illustrated its ability to slow or reverse declining soil organic levels of cropland:
The ability of manure to maintain or build soil organic matter levels has a direct impact on enhancing the amount of carbon sequestration in cropped soils.Manure organic matter contributes to improved soil structure, resulting in improved water infiltration and greater water-holding capacity leading to decreased crop water stress, soil erosion, and increased nutrient retention. An extensive literature review of historical soil conservation experiment station data from 70 plot years at 7 locations around the United States suggested that manure produced substantial reductions in soil erosion (13%-77%) and runoff (1%-68%). Increased manure application rates produced greater reductions in soil erosion and runoff. Additional studies during years following manure application suggest a residual benefit of past manure application.
Overview of Manure Impacts on Soil (Mark Risse, University of Georgia). Visit the archived webinar for additional videos on carbon, fertility, and soil health.
Manure Effects on Soil Erosion
In addition, surface application of manure behaves similarly to crop residue. Crop residue significantly decreases soil erosion by reducing raindrop impact which detaches soil particles and allows them to move offsite with water runoff. Data has been published showing how manure can coat the soil surface and reduce raindrop impact in the same way as crop residue. Therefore, in the short-term, surface manure applications have the ability to decrease soil erosion leading to a positive impact on environmental protection.
Organic Nitrogen
In addition, organic N (manure N tied to organic compounds) is more stable than N applied as commercial fertilizer. A significant fraction of manure N is stored in an organic form that is slowly released as soils warm and as crops require N. Commercial fertilizer N is applied as either nitrate or an ammonium (easily converted to nitrate). Nitrate-N is soluble in water and mobile. These forms contribute to leaching during excess precipitation (e.g., spring rains prior to or early in growing season) or irrigation. Manure N’s slow transformation to nitrate is better timed to crop N needs, resulting in less leaching potential. In fact, manure N is a natural slow-release form of N.
Energy Benefits
Recycling of manure nutrients in a cropping system as opposed to manufacturing or mining of a new nutrient resource also provides energy benefits. Commercial nitrogen fertilizers consume significant energy as a feedstock and for processing resulting in greenhouse gas emissions. Anhydrous ammonia requires the equivalent of 3300 cubic feet of natural gas to supply the nitrogen requirements of an acre of corn (assuming 200 lb of N application). Phosphorus and potassium fertilizers also have energy requirements for mining and processing. Substituting manure for commercial fertilizers significantly reduces crop production energy costs
It is important to remember that the environmental benefits of manure outlined in this article are only beneficial when best management practices for reducing soil erosion are implemented in concert with proper levels of manure nutrient application and use.
Recommended Reading on Environmental Benefits of Manure
There’s more to worker safety than just bumps and bruises. This webinar discusseson-farm injuriesrelated to manure and mortality handling and application as well aspotential toxic gas exposuresand how to minimize risks of each. This presentation was originally broadcast on October 21, 2022. Continue reading “Worker Safety in Animal Production Systems”
CEAP uses natural resource and farmer survey data along with physical process modeling to estimate the environmental impacts of conservation practices on cultivated cropland. This presentation was originally broadcast on September 23, 2022. Continue reading “Changes in manure management between CEAP I & II”
This webinar highlights ManureDB, a database of manure samples informing “book values”. Having current manure test numbers will assist in more accurate nutrient management planning, manure storage design, manure land application, and serve agricultural modeling purposes. This presentation was originally broadcast on June 17, 2022. Continue reading “Manure nutrient trends and creating dynamic “book values” through ManureDB”
As a primarily mined material, the global reserve of phosphorus (P) is finite and running out. Consequently, inorganic, commercial fertilizers are becoming more expensive. Chemical engineering techniques have been developed and are being actively researched to recover P from wastewater sources in the form of struvite (MgNH4PO4 · 6H2O). Many wastewaters contain elements such as P and nitrogen (N) in various forms that could be recovered and beneficially recycled as fertilizer nutrients. Recovering nutrients, such as P, from wastewaters and/or treating wastewaters to the point they could be safely recycled back into the environment could have a tremendously positive impact on any agricultural activity as well as receiving waters.
Arkansas has a documented significant geographic nutrient imbalance, where the row-crop-dominated region of eastern Arkansas has a severe nutrient deficiency, particularly for P, which routinely requires commercial P applications to supply crop needs for optimum production. Thus, eastern Arkansas is an ideal setting for testing the effectiveness of recovered nutrients from wastewaters as fertilizer sources, especially P, for various row crops, namely rice, corn, and soybeans. A sustainable, wastewater-recovered source of P, in the form of the mineral struvite, would be a critical advancement in the long-term viability of P availability, P-source options, and use as a fertilizer in P-deficient soils used for crop production.
What Did We Do?
Figure 1. Image of the moist-soil, plant-less laboratory incubations with various soil and fertilizer-P treatment combinations.
Various studies were conducted to evaluate the behavior of struvite in different soils and crop response to struvite as compared to other commonly used, commercially available fertilizer-P sources [i.e., monoammonium phosphate (MAP), diammonium phosphate (DAP), triple superphosphate (TSP), and rock phosphate (RP)]. Two struvite materials were tested, a chemically precipitated struvite (CPST) created from real wastewater treatment plant effluent and an electrochemically precipitated struvite (ECST) created in the laboratory with an innovative electrochemical approach.
Figure 2. Image of the column-leaching experimental set-up with various soil and fertilizer-P treatment combinations.
In the laboratory, a series of plant-less soil incubation experiments were conducted in several different agricultural soils to evaluate the behavior of struvite and the other fertilizer-P sources as they solubilize. Soil pH, water-soluble and plant-available P, magnesium (Mg), calcium (Ca), iron (Fe), nitrate and ammonium concentrations were measured over a 4- to 9-month period in moist/aerobic and saturated/flooded/anaerobic soil conditions (Figure 1). A column study was also conducted to evaluate the effects of fertilizer-P source, including ECST and CPST, on P-leaching characteristics over time in multiple soils (Figure 2).
Figure 3. Image of the rainfall-runoff experimental set-up.
Additionally, a rainfall-runoff simulation experiment was conducted to evaluate the effects of water source (i.e., rainfall, groundwater, and struvite-removed wastewater) and fertilizer-P source on runoff water quality parameters (i.e., pH, electrical conductivity, and P, N, Mg, Ca, and Fe concentrations) in various soils (Figure 3).
Figure 4. Image of rice growing in the greenhouse in response to various fertilizer-P sources with chambers in the tubs to measure greenhouse gas emissions.
In the greenhouse, several potted-plant studies were conducted for 60-90 days evaluating above- and below-ground plant response to ECST, CPST, MAP, DAP, TSP, RP, and unamended controls in rice, corn, soybeans, and wheat. Studies were also conducted to evaluate the effects of fertilizer-P source (i.e., ECST, CPST, DAP, TSP, and an unamended control) on greenhouse gas emissions (i.e., CO2, CH4, and N2O) from flood- and simulated-furrow-irrigated rice (Figure 4).
In the field, two-year studies have been conducted in soil having low soil-test-P to evaluate the effects of fertilizer-P source (i.e., ECST, CPST, MAP, DAP, TSP, RP, and an unamended control) on above- and below-ground dry matter and tissue P, N, and Mg concentrations, aboveground tissue P, N, and Mg accumulations, and yields in rice, corn, and soybeans, as well as soil P concentrations in corn and soybeans (Figure 5).
Figure 5. Image of a field study with soybean and corn grown in response to various fertilizer-P sources.
What Have We Learned?
For the moist-soil incubations, averaged across fertilizer sources, differences in water-soluble soil P concentration [from their initial concentrations] differed among soils over time and, averaged across soils, among fertilizer sources over time. In addition, averaged across time, Mehlich-3-extractable soil P concentration differences from their initial concentrations differed among fertilizer sources within soils. For the flooded-soil incubations, averaged across fertilizer sources, the change in soil pH from the initial differed among soils over time. In addition, averaged across soils, the change in water-soluble soil P concentration from the initial differed among fertilizer sources over time. Results from the plant-less soil incubation experiments show that many elemental soil concentrations, namely P, and soil pH differed among soil-fertilizer-P-source combinations over time. However, in general, the two struvite materials (ECST and CPST) behaved similarly to one another and behaved similarly to at least one other commonly used, commercially available fertilizer-P source without any large, unexpected outcomes across several different agricultural soils with varying soil textures. Struvite appears to relatively similar soil behavior as other commercially available fertilizer-P sources.
For the greenhouse study, no differences were identified in soybean plant properties. However, corn plant properties and corn and soybean elemental tissue concentrations differed (P < 0.05) among fertilizer amendments. Total corn dry matter from ECST did not differ from that from RP and TSP and was 1.2 times greater than that from CPST Belowground corn dry matter from ECST was 1.9 times greater than that from CPST, TSP, DAP, and the unamended control treatments Corn cob-plus-husk dry matter from CPST and ECST were similar. Corn belowground tissue P concentration from CPST did not differ from that from DAP, TSP, and MAP and was 1.4 times larger than that from ECST. Corn cob-plus-husk tissue P concentration from ECST was similar to that from MAP and DAP and was 1.2 times larger than that from CG. Corn stem-plus-leaves tissue P concentration from ECST differed from that from all other treatments and was 1.8 times greater than that from the unamended control. Struvite appears to be a viable, alternative fertilizer-P source.
For the 2019 rice field study, neither above- or belowground P, Mg, and N tissue concentrations differed among fertilizer sources. For the 2019 corn field study, neither above- or below-ground P, Mg, and N tissue concentrations differed among fertilizer sources. For the 2019 soybean field study, neither aboveground Mg or N nor belowground P, Mg, and N tissue concentrations differed among fertilizer sources. However, aboveground tissue P concentration was greater from ECST than from RP and the unamended control. For the 2020 rice field study, aboveground dry matter and aboveground dry matter P, N, Mg concentrations did not differ among fertilizer sources. However, rice grain yield from ECST was similar to that from CPST, but both were lower than from TSP. Aboveground Mg uptake from ECST was greater than that from CPST. For the 2020 corn field study, total aboveground, cob/husk, and stalk/leaves dry matter, aboveground P, N, and Mg concentrations and uptake, and belowground P and N concentrations did not differ among fertilizer sources. However, corn yield was larger from ECST than from all other fertilizer treatments, which did not differ among themselves. Belowground Mg concentration was numerically largest from ECST among all fertilizer-P treatments and was significantly greater than that from MAP, DAP, and TSP. For the 2020 soybean field study, neither aboveground dry matter nor yield differed among fertilizer sources. Similar to greenhouse results, struvite appears to be a viable, alternative fertilizer-P source for multiple agronomic crops, including rice, corn, and soybean.
Results from a greenhouse trial in 2021 showed that, across 13 sample dates over a nearly 4-month period evaluating the effects of fertilizer-P source on greenhouse gas fluxes and emissions from flood-irrigated rice, CO2 fluxes were unaffected by fertilizer-P source, but differed over time, while both CH4 and N2O fluxes differed among fertilizer-P treatments over time. Furthermore, results showed generally lower CO2, CH4, and N2O fluxes from ECST than from the other fertilizer-P sources and numerically lower CO2 and N2O season-long emissions from ECST than from the other fertilizer-P sources, while CH4 emissions from ECST were numerically lower than from CPST in flood-irrigated rice. Electrochemically precipitated struvite may have potential to reduce greenhouse gas emissions from flood-irrigated rice.
Future Plans
Future plans include additional laboratory rainfall-runoff simulation experiments, greenhouse potted-plant trials, and field studies to evaluate the effects of real-wastewater-derived struvite compared to other commonly used, commercially available fertilizer-P sources on soil and plant response as well as greenhouse gas emissions.
Authors
Presenting author
Lauren F. Greenlee, Associate Professor, Pennsylvania State University
Corresponding author
Kristofor R. Brye, University Professor, University of Arkansas
Corresponding author email address
kbrye@uark.edu
Additional authors
Lauren F. Greenlee, Associate Professor, Pennsylvania State University
Niyi Omidire, Post-doctoral Research Associate, University of Arkansas
Tatum Simms, Graduate Research Assistant, University of Arkansas
Diego Della Lunga, Graduate Research Assistant, University of Arkansas
Ryder Anderson, former Graduate Research Assistant, University of Arkansas
Shane Ylagan, Graduate Research Assistant, University of Arkansas
Machaela Morrison, Graduate Research Assistant, University of Arkansas
Chandler Arel, Graduate Research Assistant, University of Arkansas
Additional Information
Anderson, R., K.R. Brye, L. Greenlee, and E. Gbur. 2020. Chemically precipitated struvite dissolution dynamics over time in various soil textures. Agricultural Sciences 11:567-591.
Ylagan, S.R., K.R. Brye, and L. Greenlee. 2020. Corn and soybean response to wastewater-recovered and other common phosphorus fertilizers. Agrosystems, Geosciences & Environment 3:e20086.
Anderson, R., K.R. Brye, L. Greenlee, T.L. Roberts, and E. Gbur. 2021. Wastewater-recovered struvite effects on total extractable phosphorus compared with other phosphorus sources. Agrosystems, Geosciences & Environment 4:e20154.
Anderson, R., K.R. Brye, L. Kekedy-Nagy, L. Greenlee, E. Gbur, and T.L. Roberts. 2021. Total extractable phosphorus in flooded soil as affected by struvite and other fertilizer-P sources. Soil Science Society of America Journal 85:1157–1173.
Anderson, R., K.R. Brye, L. Kekedy-Nagy, L. Greenlee, E. Gbur, and T.L. Roberts. 2021. Electrochemically precipitated struvite effects on extractable nutrients compared to other fertilizer-P sources. Agrosystems, Geosciences & Environment 4:e20183.
Omidire, N.S., K.R. Brye, T.L. Roberts, L. Kekedy-Nagy, L. Greenlee, E.E. Gbur, and L.A. Mozzoni. 2021. Evaluation of electrochemically precipitated struvite as a fertilizer-phosphorus source in flood-irrigated rice. Agronomy Journal 114:739–755. DOI: 10.1002/agj2.20917
Brye, K.R., and L.F. Greenlee. 2022. What is struvite and how is it used? Blog post for Soil Science Society of America’s “Soils Matter” blog (https://soilsmatter.wordpress.com/).
Acknowledgements
The authors acknowledge funding from the USDA NIFA AFRI Water for Food Production Systems program, grant #2018-68011-28691 and funding from the National Science Foundation, grant #1739473.
The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.
Anaerobic digestion (AD) is commonly used in agriculture to break down livestock manure and produce a sustainable source of energy by producing biogas, which is predominantly methane. Digestion of livestock manure can be supplemented with additional agricultural or industrial organic waste, potentially adding sources of revenue to the farm or digestion facility through tipping fees and additional biogas production. However, quantifying the anticipated impact on digester performance and operation is challenging, particularly as some potential feedstocks have not been studied previously. Understanding how a feedstock might impact a digester’s performance is critical, as digester upsets can lead to loss of revenue or even digester failure.
What Did We Do?
We conducted a set of mono-digestion biomethane potential experiments of several feedstocks currently in use at an agricultural AD facility that accepts mixed industrial waste streams in addition to digesting beef manure. The mono-digestion studies used triplicate 1-L working volume batch digesters which ran for 30-38 days. We tested beef manure, off-spec starch from food manufacturing, slaughterhouse wastewater treatment sludge, waste activated sludge from a corn processing facility, soap stock from glycerin refining, filter press slurry from a food grade water treatment facility, and food waste dissolved air flotation sludge. We also included a treatment for the effluent from the digester’s ammonia recovery system and a mixture of all the feedstocks at the same time. A blank (inoculum only) and positive control (cellulose with inoculum) digester were included as controls. This set of studies is described here as Experiment 1 (E1).
We then conducted a set of co-digestion biomethane potential tests combining the manure pairwise with some of the industrial feedstocks, specifically starch, slaughterhouse waste, soap stock, and filter press slurry (Experiment 2 or E2). These combinations were made at two different ratios of the two feedstocks. The first set of treatments combined the manure and an additional substrate at a 1:1 ratio on a volatile solids basis. The second set of treatments combined the feedstocks proportional to the amounts commonly used in the AD facility providing the materials. A final treatment pairing starch and soap stock at a 3:1 ratio was also included. These co-digestion treatments were conducted in triplicate alongside a single mono-digestion treatment of each feedstock for comparison. Finally, we examined the potential synergistic or antagonistic impacts of these combinations on methane yield and production rate. This was done by comparing the measured methane production at each time point compared to the expected methane production if the feedstocks each contributed additively to the methane production.
What Have We Learned?
Figure 1 shows the cumulative specific biogas production on a volatile solids basis for the mono-digestion experiment (E1). Some feedstocks, such as soap stock and slaughterhouse waste, experienced a substantial lag phase at the beginning of the experiment, which may have been due to the high levels of lipids and proteins.
Figure 1: Average biogas production of all treatments during mono-digestion experiment (Experiment 1).
During the co-digestion experiment (E2), we observed both total yield and kinetic synergy in all treatments. Only two digesters (one of the replicates from the starch and manure proportional treatment and one from the starch and soap stock treatment) produced substantially less (<30%) methane than would be expected for an additive effect for more than one day. This effect can be seen in Figure 2, which shows the cumulative methane curves (corrected for inoculum contribution and averaged over the three replicates) of the mono-digestion digesters for manure and starch individually and the curves for both co-digestion treatments using both manure and starch. Figure 3 shows the same curves for the co-digestion of manure and slaughterhouse waste. These co-digestion treatments show that combining the feedstocks causes an increase in methane production at a faster rate. They also show that co-digestion alleviates the lag phase experienced by the slaughterhouse waste.
Figure 2: Cumulative specific methane production for manure (F1) and starch (F2). F1 + F2 Eq = 1:1 ratio of VS; F1 + F2 Pr = ratio of VS is proportional to what full-scale digester receives.Figure 3: Cumulative specific methane production for manure (F1) and slaughterhouse waste (F3). F1 + F3 Eq = 1:1 ratio of VS; F1 + F3 Pr = ratio of VS is proportional to what full-scale digester receives.
Future Plans
We plan to continue exploring the impact of co-digestion on methane yield and production rate by using additional combinations of these feedstocks and exploring the impact of macromolecular composition (percentages of carbohydrates, proteins, and lipids) on synergistic effects. These results will help inform current or future agricultural AD operators regarding the use of co-digestion feedstocks for optimal energy production and best practices in selecting new feedstocks for co-digestion.
Authors
Jennifer Rackliffe, Graduate Research Fellow, Purdue University
This material is based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under agreement number 2020-38640-31522 through the North Central Region SARE program under project number GNC21-334. USDA is an equal opportunity employer and service provider. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture. We also thank Purdue’s Institute for Climate, Environment and Sustainability for supporting the dissemination of this work. Finally, we acknowledge the assistance of Gabrielle Koel, Kyra Keenan, Amanda Pisarczyk, and Emily McGlothlin in conducting the laboratory work.
The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.
The purpose of this study was to develop and analyze potential recipes for composting swine lagoon sludge. Composting is a simple treatment; it is widely adopted on farms, generates a stable value-added stackable product, and conserves organic matter and nutrients. All these benefits along with an affordable cost and lower environmental emissions make it a potential candidate for the management of lagoon sludge, a byproduct of swine operations in southeast US.
Sludge accumulation in lagoons can result in increased odor from lagoons, impact animal productivity, increase risk of environmental and social consequences and lead to operation non-compliance. Developing affordable sludge management alternatives is important because current practices (land application post dredging and dewatering using organic polymers and geo-bags) are not widely adoptable, cost-prohibitive and non-sustainable (Owusu-Twum and Sharara, 2020, Soil facts) and current farm nutrient management plans do not consider management of sludge nutrients.
What Did We Do?
We developed two recipes by mixing different sludge amounts with locally available low-cost amendments: poultry litter, Bermuda hay, yard debris and lagoon liquid. We composted these recipes in triplicates using 13-cubic feet in-vessel composters and recorded changes in temperatures, weight loss, volume, moisture, and organic matter. We also recorded greenhouse gases emitted from the piles at regular intervals. Forced, intermittent aeration was maintained during composting for replicates to ensure adequate oxygen supply and avoid prematurely drying mixtures. Finally, we analyzed the final compost to determine its suitability as a soil amendment.
We used the observations from the experiments to evaluate if proposed recipes resulted in successful compost and determine whether sludge inclusion significantly impacts composting process and product quality. We also analyzed which factors influence weight and organic matter losses in the piles and if the proposed recipes have comparable cumulative GHG and NH3 emissions to previous observations.
What Have We Learned?
We learned that sludge can be composted at both 10% and 20% inclusion rates using the above ingredients, as the process met time and temperatures for pathogen reduction (15A NCAC, 13B.1406) and the final product were stable (TMECC, US Composting council). For 100 lbs. of an initial wet mixture (60.8 to 61.4% moisture) both recipes experienced a total weight loss of 33.8-35.2 lbs. with 24.5 to 25.4 lbs. being lost as moisture and 8.8 to 9.7 lbs. lost as organic matter during the active phase of composting (31 days). Post-screening the recipes resulted in 42.3 to 48.6 lbs. of the stable final product (45 to 47% moisture) that can be directly land applied.
We learned that the composting process generated similar GHG, and ammonia emissions as reported in the previous studies however, most of the methane (CH4) and nitrous oxide (N2O) were generated in the later stages of composting, which can be potentially reduced by proper management of the composting process. Another observation was larger losses in ammonia in the earlier stages of composting which on reduction; using certain additives, changes in recipe or management practices, can result in optimal utilization of nitrogen, increase product value, and reduce environmental impacts.
Future Plans
We plan to further analyze the impact of the composting process on total nutrients and water-extractable fractions, this will provide information on land use rate and potential losses in runoffs. This information is critical for swine lagoon sludge-derived products due to the high concentration of P, Zn, and Cu in sludge as losses can lead to eutrophication in surface and marine waters and potential toxicity in soils.
Future work proposed also involves techno-economic evaluation of this process to determine the cost of treatment, and fair price of the final product. We also plan to conduct a cradle to gate life cycle assessment of the process to determine global warming potential, eutrophication, acidification, and particulate matter generation for farm and large-scale systems. These efforts will help guide further research to improve the technology and provide knowledge to stakeholders and producers on alternative sludge management options.
Figure 1. Swine lagoon sludge composting process and products.
References
Owusu-Twum, M. Y., & Sharara, M. A. (2020). Sludge management in anaerobic swine lagoons: A review. Journal of Environmental Management, 271, 110949.
Soil Facts, Karl A. Shaffer, Dianna Deanna L. Osmond, Sanjay B. Shah, Phosphorus Management for Land Application of Biosolids and Animal Waste, North Carolina Cooperative extension.
Stephanie Kulesza, Assistant Professor, Crop & Soil Sciences, North Carolina State University
Sanjay Shah, Professor and Extension specialist, Bio&Ag. Eng. North Carolina State University
John Classen, Associate Professor, Bio&Ag. Eng. North Carolina State University
Additional Information
Publication is in progress currently so best resource is the corresponding author.
Acknowledgements
We would like to acknowledge the support from Joseph Stuckey and Chris Hopkins (Poultry, livestock, and animal waste management facility, NCSU).
Funding sources
Bioenergy Research Initiative (BRI) – Contract No #17-072-4015, North Carolina Department of Agriculture & Consumer Services
National Institute of Food and Agriculture (NIFA) – Critical Agricultural Research and Extension (CARE) – Award No. 2019-68008-29894, 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. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.
The decision-support tool (DST) being developed facilitates the selection of manure treatment technology based on farm needs and nutrient balance requirements. A life cycle assessment (LCA) approach is used to determine and allocate among sources the whole-farm greenhouse gas (GHG) emissions and environmental impact of different manure management systems (MMS) to facilitate decision-making. The purpose of the tool is to help users identify the suite of technologies that could be used, given the farm’s unique set of preferences and constraints. The tool asks for an initial set of farm details and these values are cross-checked with predefined conditions before starting the simulation. This tool helps in the rapid quantification and assessment of treatment technology feasibility, GHG emissions, environmental, and economic impacts during the manure management decision-making process (Fig. 1). The decision algorithm operates based on user input for weightage priorities of criteria and sub-criteria related to environmental, economic, and technical components.
Figure 1. Graphical abstract
What Did We Do?
The DST is a Microsoft Excel-based tool with precalculated mass balance for a selected number of MMS alternatives representing current and emerging treatment technologies and practices. The MMS considered for the tool includes various handling systems, aerobic and anaerobic treatment systems, solid-liquid separation techniques, chemical processing units, etc. Modules were developed based on mass and energy balances, equipment capital & operating costs, unit process, and technology performance, respectively. The tool utilizes data specific to the country/region/farm where feasible and default values to calculate the overall economic and environmental performance of different MMS, providing results unitized per animal/day or per year.
Then, an LCA approach is used to evaluate the potential environmental footprints of each MMS considered. A life cycle impact assessment (LCIA) is comprised of detailed quantification of inputs and outputs of material flows in a specific treatment and/or conversion process. At the output level, it also defines and quantifies the main product, co-products, and emissions. The major focus on the treatment methods is quantifying the raw materials (manure, wash-water, bedding, etc.) that are to be handled in each MMS, thereby characterizing the properties of effluents (nutrients, gas emissions, etc.). The results include carbon, energy, water, land, nitrogen, and phosphorus footprints along with the effluent nitrogen, phosphorous, and potassium concentrations.
What Have We Learned?
Systematic selection of appropriate technology can provide environmental and economic benefits. Manure management systems vary in their design, due to individual farm settings, geography, and end-use applications of manure. However, the benefits of technological advancements in MMS provide manure management efficiencies and co-production of valuable products such as recycled water, fiber, sand bedding, and nutrient-rich bio-solids, among others. The handling efficiencies and environmental benefits provided by manure treatment technologies come with additional costs, however, so the tradeoffs between environmental benefits and implementation costs also need evaluation.
Future Plans
The next steps are to finalize the dairy module. We are refining the tool’s user interface and demonstrating to stakeholders to gather information regarding key assumptions, outputs, and the functionality of the tool. Further, we also plan to complete the swine module.
Authors
Sudharsan Varma Vempalli, Research Associate, University of Arkansas
Sudharsan Varma Vempalli, Research Associate, University of Arkansas
Erin Scott, PhD Graduate Assistant, University of Arkansas
Jacob Allen Hickman, Project Staff, University of Arkansas
Timothy Canter, Extension Specialist, University of Missouri
Richard Stowell, Professor, University of Nebraska-Lincoln
Teng-Teeh Lim, Extension Professor, University of Missouri
Lauren Greenlee, Associate Professor, The Pennsylvania State University
Jennie Popp, Professor, University of Arkansas
Greg Thoma, Professor, University of Arkansas
Additional Information
Detailed economic impacts and tradeoffs expected with the implementation of certain MMS related to this tool is presented during the conference by Erin Scott et al., on the topic “Evaluating Costs and Benefits of Manure Management Systems for a Decision-Support Tool”.
Varma, V.S., Parajuli, R., Scott, E., Canter, T., Lim, T.T., Popp, J. and Thoma, G., 2021. Dairy and swine manure management–Challenges and perspectives for sustainable treatment technology. Science of The Total Environment, 778, p.146319. https://www.sciencedirect.com/science/article/pii/S0048969721013875
Acknowledgements
We acknowledge funding support from the United States Department of Agriculture (USDA) National Institute of Food and Agriculture (NIFA) grant award (# 2018-68011-28691). We would also like to thank our full project team and outside experts for their guidance 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. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.
The purpose of the decision-support tool is to help livestock producers understand the costs of implementing new technology and the potential benefits associated with nutrient and water recovery, and how these compare across systems. Livestock agriculture is under increased scrutiny to better manage manure and mitigate negative impacts on the environment. At the same time, the nutrients and water present in manure management systems hold potential economic value as crop fertilizer and irrigation water. While technologies are available that allow for recovery and/or recycling of solids, nutrients and water, appropriate decision-support tools are needed to help farmers evaluate the practicality, costs, and benefits of implementing these systems on their unique farms.
What Did We Do?
In designing and refining the tool, we consider which economic components are important in driving the decision algorithm, as well as what is the most valuable economic output information for the user. We developed several “scenarios” defined by the unit processes used in the capture, treatment, storage, and usage of dairy manure. The costs and benefits related to each unit process were evaluated and aggregated for each scenario. Unit processes included flush/scrape activities, reception pit, sand recovery, solids separation, anaerobic digestion, composting, pond/lagoon storage, and tanker/drag hose land application.
Economic information was gathered from published literature, government documents, extension tools, and communication with academic, industry, and extension experts. We evaluated capital costs as an annual capital recovery value; operational costs including labor, energy, and repair and maintenance; cost savings resulting from sand/organic bedding and water reuse; fertilizer value of manure for use on-farm; revenue potential including the sale of treated manure nutrients and energy from anaerobic digestion; and the combined net costs or net benefits. Economic results are integrated into the multi-criteria decision algorithm. Results also elucidate economic tradeoffs across manure management systems (MMS), which can be used by farmers to assist in their decision-making.
What Have We Learned?
Economics is often about evaluating trade-offs between different choices or decisions. When evaluating results from the tool, we see that an increase in capital spending may lead to decreases in operational costs relative to capital costs, depending on farm size. This is due to a general reduction in labor and fuel costs associated with automated or additional manure treatment (e.g. increased spending on an MMS). For example, additional manure treatment can reduce land application expenses and increase cost savings from recovered sand or organic bedding. However, this larger capital outlay may or may not be possible based on the farm’s financial circumstances.
Future Plans
The next steps are to complete the economic analyses of a total of 60 MMS and integrate these into the decision-support tool. We plan to demonstrate this tool to extension specialists and producers to refine the user interface, key assumptions, functioning of the decision algorithm, and the usability of the results.
Authors
Erin E. Scott, PhD Graduate Assistant, University of Arkansas
We acknowledge funding support from the United States Department of Agriculture (USDA) National Institute of Food and Agriculture (NIFA) grant award (# 2018-68011-28691). We would also like to thank our full project team and outside experts for their guidance 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. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.
Our recent work has focused on developing approaches to nutrient management and recovery, with a particular focus on using electrochemical and membrane technologies to control the chemistry of the recovered nutrient products. We are interested in being able to recover both ammonia and phosphate, and our goal is to create recycled fertilizer products that can allow the agricultural community to control the ratio of nitrogen to phosphorus in the recycled fertilizer products and to control whether those fertilizer products are in liquid form or in solid form. With the electrochemical technology focus, we see benefits that include no required chemical dosing, scalable reactor design, and the ability to couple to renewable energy sources. Our engineering research on nutrient recovery technology is conducted within a team that includes life cycle assessment, economic analysis, agronomic greenhouse and row crop studies, agricultural sector outreach, and the development of a decision-support tool to help farmers understand technology options for water and nutrient management.
What Did We Do?
We have investigated an electrochemical cell design that includes a magnesium metal anode and a stainless-steel cathode. The corrosion of the magnesium anode results in the release of magnesium cations into solution, and these magnesium cations promote the precipitation of struvite, otherwise known as magnesium ammonium phosphate hexahydrate (Figure 1). We have investigated how operating conditions of the electrochemical cell, including voltage, residence time, batch vs flow, and membrane separation of the two electrodes, affect nutrient recovery efficiency and the overall chemistry of the recovered precipitate. Our studies have included control experiments on synthetic wastewater compositions relevant to hog and dairy farm wastewaters, while we have also conducted laboratory-scale studies on natural wastewater samples from both agricultural and municipal sources. To demonstrate initial scale-up of an electrochemical reactor, we have designed a bench-scale reactor (Figure 2) that is capable of producing kilogram-level batches of struvite.
Figure 2. (a) Bench-scale batch reactor demonstration for kg-level struvite precipitation. (b) One engineering challenge is the precipitation of struvite on the electrode surface.
What Have We Learned?
The production of struvite from an electrochemical reactor can be controlled by the applied voltage and residence time of the wastewater in the reactor. Changes in reactor design, including the inclusion of a membrane to separate the anode and cathode and operation in batch vs flow mode, can change the composition of the struvite precipitate and can cause a change in the balance of struvite formed vs hydrogen gas formed from the electrochemical cell. We are also able to produce K-struvite, a potassium-based alternative to conventional struvite, that includes potassium rather than ammonium, and the production of K-struvite allows the recovery of the phosphate in a particulate fertilizer while also allowing the separation and recovery of ammonia in a separate liquid stream. We have learned that one of the primary challenges to the electrochemical reactor operation is fouling of the electrodes by the struvite precipitate (Figure 2), and we have developed a dynamic voltage control approach that enables minimal electrode fouling and therefore increases struvite recovery and decreases energy consumption. Our energy consumption values are similar to that of chemical precipitation processes that have been developed for nutrient recovery.
Future Plans
Future plans include further development and optimization of the dynamic voltage control approach to electrochemical reactor operation, which will allow us to control electrode fouling. We also plan to continue working with natural wastewater samples and further develop flow cell reactor design to understand how to translate our batch reactor studies to a flow reactor environment. Studies on K-struvite will focus on understanding the kinetics of K-struvite precipitation and the competing reactions (e.g., calcium precipitation and struvite precipitation) that might impact K-struvite recovery.
Authors
Lauren F. Greenlee, Associate Professor, Pennsylvania State University
Corresponding author email address
greenlee@psu.edu
Additional authors
Laszlo Kekedy-Nagy, Postdoctoral Fellow, Concordia University
Ruhi Sultana, Graduate Research Assistant, Pennsylvania State University
Amir Akbari, Graduate Research Assistant, Pennsylvania State University
Ivy Wu, Graduate Research Assistant, Colorado School of Mines
Andrew Herring, Professor, Colorado School of Mines
Additional Information
Kekedy-Nagy, Z. Anari, M. Abolhassani, B.G. Pollet, L.F. Greenlee. Electrochemical Nutrient Removal from Natural Wastewater Sources and its Impact on Water Quality. Water Research (2022), 210, 118001, DOI: 10.1016/j.watres.2021.118001.
Kékedy-Nagy, M. Abolhassani, R. Sultana, Z. Anari, K.R. Brye, B.G. Pollet, L. F. Greenlee. The Effect of Anode Degradation on Energy Demand and Production Efficiency of Electrochemically Precipitated Struvite, Journal of Applied Electrochemistry (2021), DOI: 0.1007/s10800-021-01637-y.
Kékedy-Nagy, M. Abolhassani, S.I. Perez Bakovic, J.P. Moore II, B.G. Pollet, L.F. Greenlee. Electroless Production of Fertilizer (Struvite) and Hydrogen from Synthetic Agricultural Wastewaters, Journal of the American Chemical Society (2020), 142(44), 18844-18858. DOI: /10.1021/jacs.0c07916.
Wu, A. Teymouri, R. Park, L.F. Greenlee, and A.M. Herring. Simultaneous Electrochemical Nutrient Recovery and Hydrogen Generation from Model Wastewater Using a Sacrificial Magnesium Anode, Journal of the Electrochemical Society (2019), 166(16), E576-E583. DOI: 10.1149/2.0561916jes.
Acknowledgements
The authors acknowledge funding from the USDA NIFA AFRI Water for Food Production Systems program, grant #2018-68011-28691 and funding from the National Science Foundation, grant #1739473.
The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.
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