Most agricultural waste is largely composed of polymers such as lignin and complex carbohydrates that are slowly or nearly completely non-degradable in anaerobic environments. An example of such a waste is chicken litter in which wood chips, rice hulls, straw and sawdust are commonly employed bedding materials. This makes chicken litter a poor candidate for anaerobic digestion because of inherently poor digestibility and, as a consequence, low gas production rates.
Previous studies, however, have shown that the addition of small amounts of air to anaerobic digestates can improve degradation rates and gas production. These studies were largely performed at laboratory-scale with no provision to keep the added air within the anaerobic sludge.
What Did We Do?
Four digesters were constructed out of 55 gallon sprayer tanks. The digestate was 132 L in volume with a dynamic headspace of 76 L. At the bottom of each tank a manifold was constructed from ½” PVC pipe in an “H” configuration and with a volume of approximately 230 mL. The bottom of the manifold had holes drilled in it to allow exchange with the sludge. Tanks were fed 400 g of used top dressing chicken litter (wood shaving bedding) obtained from a local producer (averaging 40% moisture and 15% ash) in 2 L of water through a port in the tank [labeled “1” in figure]. Two hundred mL of air were fed to the manifold through a flow meter [2] 0, 1, 4, or 10 times daily in 15-minute periods at widely spaced intervals by means of an air pump and rotary timer [4]. A gas port [3] at the top of the tank allowed for sampling and led to a wet tip flow meter (wettipflowmeters.com) to measure gas production. Digestate samples were taken out of a side port [5] for measurement of water quality and dissolved gases and overflow was discharged from the tank by means of a float switch wired in line with a ½” PVC electrically actuated ball valve.
Seven dried and weighed tulip poplar disks were added to each tank at the beginning of the experiment. At the end of the experiment, the disks were cleaned and dried for three days at 105 0C before re-weighing. Dissolved and headspace gases were measured on a gas chromatograph equipped with FID, ECD, and TCD detectors. Water quality was measured by standard APHA methods.
What Have We Learned?
Adding 800 mL of air daily increased biogas production by an average of 73.4% compared to strictly anaerobic digestate. While adding 200 mL of air daily slightly increased gas production, adding 2 L per day decreased gas production by 16.7%.
Aerating the sludge improved chemical oxygen demand (COD) with the greatest benefit occurring at 2,000 mL added air per day. As noted, however, this decreased gas production in the control indicating toxicity to the anaerobic sludge.
The experiment was stopped after 148 days. When the tanks were opened, there was widespread fungal growth both on the surface of the digestate and the wood disks in the aerated tanks [left], whereas non-aerated tanks showed little evidence of fungal growth [right]. While wood disks subjected to all treatments lost significant mass (t-test, α=0.05), disks in the anaerobic tank lost the least amount of weight on average (6.3 g) while all other treatments lost over 7 g weight on average.
Future Plans
Research on other feedstocks and aeration regimes are being conducted as are 16s and 18s community analyses.
Corresponding author (name, title, affiliation)
John Loughrin, Research Chemist, Food Animal Environmental Research Systems, USDA-ARS, 2413 Nashville Rd. B5, Bowling Green, KY 42104
The US EPA Chesapeake Bay Program assesses nutrient loading to the Chesapeake Bay. There is a need to determine the impact of manure treatment technologies on reducing the nitrogen and phosphorus loading from agriculture. Furthermore, many states within the Chesapeake Bay Watershed control nutrient discharges through watershed nutrient trading programs. Tables of standard nutrient removal efficiencies of various technologies will allow states to implement these programs.
What did we do?
An expert panel was convened by the EPA Chesapeake Bay Program to determine nutrient removal potential of manure treatment technologies. The following seven technology categories were reviewed: thermochemical processing, anaerobic digestion, composting, settling, mechanical solid-liquid separation, and wet chemical treatment. Within these categories, the panel defined 24 named technologies for detailed review. The scientific literature was reviewed to determine the ability of each technology to transfer volatile nitrogen to the atmosphere and transfer nutrients to a waste stream more likely to be used off-farm (or transported out of the Chesapeake Bay Watershed).
What have we learned?
Manure treatment technologies are used reduce to odors, solids, and organic matter from the manure stream, with only minor reductions in nutrient loading. The panel determined that Thermo-Chemical Processing and Composting have the potential to volatilize nitrogen, and all of the technologies have the ability to transfer nutrients into a more useful waste stream. The greatest effect of treatment technologies is the transformation of nutrients to more stable forms – such as precipitation of insoluble phosphorus from dissolved phosphorus.
Future Plans
The panel’s report is undergoing final authorization from the Chesapeake Bay Program for release to the public. Future panels may choose to revisit the issue of nutrient reduction from manure treatment technologies. The current panel recommends future panels expand the categories of technologies to include liquid aerobic treatment, and examine more named technologies as they become available within the Chesapeake Bay Watershed.
Corresponding author, title, and affiliation
Douglas W. Hamilton, Associate Professor Oklahoma State University
Keri Cantrell, KBC Consulting;John Chastain, Clemson University; Andrea Ludwig, University of Tennessee; Robert Meinen, Penn State University; Jactone Ogejo, Virginia Tech; Jeff Porter, USDA Natural Resource Conservation Service, Eastern Technology Suppor
Funding for this panel was provided by the US EPA Chesapeake Bay Program and Virginia Tech University through EPA Grant No. CB96326201
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. 2017. Title of presentation. Waste to Worth: Spreading Science and Solutions. Cary, NC. April 18-21, 2017. URL of this page. Accessed on: today’s date.
In a global context, the pork industry constitutes a huge economic sector but many producers operate on very thin margins. In addition, pork is one of the largest and most important agricultural industries in North Carolina and the United States but faces a number of challenges in regards to waste management and environmental impacts.On more local scales, swine producers face a number of additional constraints including land availability, waste management options (technical and regulatory), nutrient management costs, profits, risk, and return on investment. In the face of increasingly stringent environmental regulations, decreasing land availability, and higher costs for fertilizer, it is necessary to consider alternative technologies with the potential for improving environmental conditions and creating value added products. Technology assessments generally focus on technical performance as the measure of “utility” or usefulness. Primary physical performance measures such as efficiency, production rate, and capacity, while necessary may not be sufficient for capturing the overall value of a technology. A significant amount of research has evaluated the feasibility of technology adoption based on traditional economic measures but far less research has attempted to “value” environmental performance either at farm-scale or in the larger context (e.g. supply chain response to changes in technology or policy and regulation). Considering response over time, the extent to which environmental and economic policies and regulations positively or negatively affect technology innovation, emission and nutrient management, competitiveness, and productivity, remains largely unknown.
The purpose of this study is to evaluate the environmental and economic tradeoffs between current swine waste management practices in North Carolina and alternative scenarios for future on-farm decision making that include new technologies for waste removal, treatment, and nitrogen recovery. In addition, we begin to understand these economic and environmental tradeoffs in the context of various environmental policy and regulation scenarios for markets of carbon, electricity, and mineral fertilizer.
What did we do?
Using waste samples from swine finishing farms in southeastern NC, laboratory and bench scale experiments were conducted to determine the quantity and quality of biogas generation from anaerobic digestion and nitrogen recovery from an ammonia air stripping column. Based on these data as well as information from literature, six trial life cycle assessment scenarios were created to simulate alternatives for annual manure waste management for one finishing barn (3080 head) on the farm. Materials, energy, and emissions were included as available for all system components and processes including but not limited to waste removal from barns (flushing or scraping), treatment (open air lagoon or covered lagoon digester), nitrogen recovery (ammonia air stripping column), and land application (irrigation). A description of the scenarios as well as processes that are included/excluded for each can be found in Table 1. All scenarios were modeled over a one year operational period using a “gate to gate” approach where the mass and energy balance begins and ends on the farm (i.e. production of feed is not included and manure is fully utilized on the farm). It was assumed that each scenario included an existing anaerobic treatment lagoon with manure flushing system (baseline, representative of NC swine farms). In the remaining scenarios, the farm had an option of covering the lagoon and using it as a digester to produce biogas (offsetting natural gas); covering the digester and ammonia air stripping column for nitrogen recovery (offsetting mineral ammonium sulfate); installing a mechanical scraper system in the barn (replaces flushing); and/or different combinations of these. Open LCA, an open source life cycle and sustainability assessment software, was used for inventory analysis and the Tool for Reduction and Assessment of Chemicals and Other Environmental Impacts (TRACI 2.0) was used to characterize environmental impacts to air, water, and land. From Table 2 preliminary results indicate that all scenarios had a similar pattern in terms of impact for the assessed categories. The open air lagoon had the highest overall environmental impact followed by scraping manure with digestion and recovery and scraped slurry digestion with no nutrient recovery. Flushed manure to the digester with nutrient recovery had the lowest overall environmental impact, followed closely by scraped whole slurry to the digester with nutrient recovery.
Using energy and emissions data from the initial life cycle assessment on alternative scenarios for swine waste management systems we have started to characterize the environmental and economic outcomes arising from selected on farm technologies. More specifically we began to examine the regulatory, institutional, and market barriers associated with technology adoption within the swine industry. We provide a theoretical model to support quantification of the change in revenues and expenses that result from changes in three major markets connected to swine production – carbon, electricity, and fertilizer. We examine some of the economic characteristics of environmental benefits associated with changes to farm practices. Finally, we discuss implications for innovation in technology and policy.
What have we learned?
Preliminary results are somewhat mixed and further research is needed to see how sensitive the life cycle assessment inputs and outputs are to system components. While there is a clear indication that covering lagoons, with or without additional nutrient recovery, reduces environmental impact – farm scale systems can be quite expensive and no further determination can be made until a full economic analysis has been conducted. Modeling secondary effects, such as increased ammonia emissions in barns from flush water recirculated from digesters, remains to be included. Besides farm level cost and returns, review of literature has pointed to additional barriers to adoption of reduced environmental impact technologies. Examples of barriers include deficient or non-existent markets for environmental benefits, and various state and federal regulations and policies related to renewable energy, carbon offsets, new farm waste management technology, etc. Solutions such as better cooperation between energy firms, regulatory agencies, and farmers as well as increased financial incentives such as carbon credits, renewable energy credits, net metering options, and enabling delivery of biogas to natural gas pipelines can greatly increase the profitability and implementation of this technology on NC hog farms.
Future Plans
As this is an ongoing multi-disciplinary project, future plans include the expansion of existing data to form a more comprehensive life cycle inventory with options for both new and existing swine farms, which include additional options for waste treatment, nutrient recovery, and land application/fertilizer methods, etc. Energy and emissions data from the life cycle model will continue to be utilized as inputs into a more fully integrated model capable of reflecting the true “cost” and “values” associated with waste management treatment systems. In addition, it is expected that the integrated model will include the flexibility to simulate overall costs and returns for various sizes of operations within the county, region, and if possible state-wide.
Corresponding author, title, and affiliation
Shannon Banner, Graduate Student, North Carolina State University
Dr. John Classen, Dr. Prince Dugba, Mr. Mark Rice, Dr. Kelly Zering
Acknowledgements
Funding for this project was provided by a grant from Smithfield Swine Production Group
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. 2017. Title of presentation. Waste to Worth: Spreading Science and Solutions. Cary, NC. April 18-21, 2017. URL of this page. Accessed on: today’s date.
Improving the economic feasibility of anaerobic digestion projects for processing dairy manure.
What did we do?
We completed a study that evaluated the economics of dairy manure granulation as means to export phosphorus from P-sensitive watersheds. To achieve this goal we developed a techno-economic optimization model that considers all dairy farms within the watershed simultaneously to determine the minimum break-even price for the granulated manure.
A second study was developed to assess the economics of anaerobic digestion using a techno-economic optimization model. We incorporated different revenue sources (power sale, methane destruction credits, renewable energy certificates (RECs) and tipping fee (if co-substrate is available). The model evaluated the project feasibility over ranges of values for technical and economic parameters to quantify the project resilience to uncertainty in process conditions.
What have we learned?
The results from the first study indicated that multi-farm participation can significantly improve feasibility and overall economics of manure granulation. Herd sizes were found to be a critical parameter in deciding whether a farm can economically participate in coordinated management. For manure granulation projects, liquid-solid separation followed by transportation of separated solids was always more economical than transporting raw manure from satellite farm to central processing facility. In the second study, electricity sale price was found to be the key parameter that determines the feasibility of anaerobic digesters. The hub-spoke configuration, where a large central farm hosts the digester and smaller surrounding farms contribute to it was found to be the most favorable arrangement. The size of the hub farm was critical to the feasibility of the project. Similarly, transportation distance was a critical factor that constrained the extent of cooperative digesters.
Future Plans
The information generated from these studies is being written into peer-review publications and factsheets to share insights of collaborative manure management with a wider audience.We are currently expanding the model by adding the option for manure transportation via pipelines. Furthermore, we are also incorporating additional biogas utilization technologies,i.e., natural gas sale over pipelines and also the utilization of power/heat on-site in manure upgrading and processing.
Corresponding author, title, and affiliation
Troy M. Runge, Associate Professor, University of Wisconsin-Madison
2. Sharara, Mahmoud, Apoorva Sampat, Laura W. Good, Amanda S. Smith, Pamela Porter, Victor M. Zavala, Rebecca Larson, and Troy Runge. “Spatially explicit methodology for coordinated manure management in shared watersheds.” Journal of Environmental Management 192 (2017): 48-56.
3. Sharara, Mahmoud, Qiang Yang, Thomas L. Cox, and Troy Runge. “Techno-economic assessment of dairy manure granulation.” In 2016 ASABE Annual International Meeting, p. 1. American Society of Agricultural and Biological Engineers, 2016.
Acknowledgements
This work is based on research supported by the USDA National Institute of Food and Agriculture for its financial support (USDANIFABRDI Grant No. 2012-10006-19423) and funding from Dane County, Wisconsin under Award Number 12486.
People in developing countries regularly lack access to energy or their energy source is not reliable. Low cost anaerobic digestion systems have the potential to provide methane to be used in a variety of end uses. Unfortunately, many low cost systems are not evaluated and it is unclear if they are living up to the expectations of the end users or those that are promoting or financially supporting their installation.
What did we do?
We have evaluated multiple small scale anaerobic digestion systems in Uganda and Bolivia to assess their energy production potential, impact of digestate as a fertilizer (using plot studies), pathogen reduction through the digester, and impact to kitchen air quality when biogas stoves replace firewood. Based on feedback we have also designed, tested and implemented a low cost separation system for handling digestate to recycle separated liquids and improve handling of solids. We have also modified an absorption chiller to run on biogas and are in the process of wider spread adoption and evaluation.
What have we learned?
Throughout this assessment we have learned that many institutional level digestion systems in developing countries are not meeting the biogas demands of the end users. While they like the improved cooking time and reduced air quality impacts in the kitchen, only small households are producing enough gas to realize many of these benefits. Biogas poses a reduction in PM2.5 (fine particulates) within kitchens when compared to firewood stoves. However, when any amount of firewood is used in the kitchens (when there is not enough biogas), much of this benefit is lost. Therefore it is critical to improve the biogas production of these systems.
Maize plot trials show that compared to control plots digestate applied in any form (slurry or separated solids) significantly improves yields. When compared to inorganic fertilizer applications the grain yields are statistically similar but the stover yields increase significantly. End users show a preference for using the separated solids and the reduction in water needed to operate the systems. While these benefits seem appealing, there may be concern for the risks associated with pathogens in the digestate when applied to food crops. While digesters showed a significant reduction in pathogen related to the system retention time, pathogen remained in the effluent and must be handled properly to limit transfer to food and the human health risks after ingestion.
Increasing the end use of biogas beyond cooking to chillers has shown great potential for implementation and has high demand for end users. Systems have been able to provide cooling at multiple locations for extended periods with low biogas demands. Additional materials are needed to provide end users with guidance on troubleshooting and operation.
Future Plans
Based on the results of these studies we are moving forward with farmer trials of the digestate to assess end user issues and motivations. In addition, we are currently designing a low cost heating system to improve biogas production efficiency in order to meet end user needs or decrease the size of digesters. Finally we are working on an evaluation of chiller biogas needs and providing training on all aspects of the digestion systems.
Corresponding author, title, and affiliation
Rebecca Larson, Assistant Professor at the University of Wisconsin-Madison
McCord, A.I., S.A. Stefanos, V. Tumwesige, D. Lsoto, A. Meding, A. Adong, J.J. Schauer, and R.A. Larson. 2017. Biogas and the impacts of fuel choice on institutional kitchen air quality in Kampala, Uganda. Indoor Air. In Review, revisions requested.
McCord, A.I., S.A. Stefanos, V. Tumwesige, D.T. Lsoto, M. Kawala, J. Mutebi, I. Nansubuga, and R.A. Larson. 2017. Anaerobic digestion and public sanitation in Kampala: risks and opportunities. In Review.
Even when antibiotics are used judiciously, antibiotic residues, antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARG) can accumulate in human waste and manure and contribute to the spread of antibiotic resistance. Modern U.S. dairy farms use antibiotics for disease treatment and prevention according to the guidance of veterinary physicians. While dairy manure handling and treatment systems may effectively mitigate antibiotic resistance, the fate of antibiotic residues, ARB and ARG through these systems has not been adequately investigated.
What did we do?
Working cooperatively with 11 dairies in 3 states (NY, PA, MD) our multi-institutional (U. Buffalo, Cornell, U. Maryland, U. Michigan), interdisciplinary team is investigating the effect different manure management practices (e.g. long-term storage, composting, anaerobic digestion, etc.) have on antibiotic residue levels, ARB and ARG. Every 6 weeks for 2 years manure is being collected pre- and post- each treatment step of the various manure handling systems used by each farm. All samples are being characterized and tested for select antibiotic residues (tetracyclines, macrolides, sulfonamides, penicillins and ceftiofurs), with select samples also analyzed for ARB and ARG. To guide these efforts, antibiotic usage and manure treatment system operational data are also being collected for each farm.
What have we learned?
A year of samples has been collected with analysis of antibiotic residues, ARB and ARG on-going. Based on the preliminary data, antibiotic residues are detectable at low-concentrations (< 200 mg/L) in each farm’s manure. Antibiotic residue levels are generally lower in treated manure compared to levels in raw manure, though mitigation efficacy is variable. Early findings show some composting systems have the capacity to lower antibiotic residue levels. Antibiotic residue levels are also lower in separated manure solids, with evidence for partitioning of soluble antibiotic residues into separated manure liquids. At this time, the effects of anaerobic digestion and long-term anaerobic manure storage on antibiotic residue levels remain unclear. Select samples are currently being analyzed for ARB and ARG.
Future Plans
We are entering our second year of field monitoring and ARB and ARG analysis is on-going. Laboratory efforts are also beginning to test the effectiveness of specific anaerobic digester operational parameters at mitigating antimicrobial resistance. Extension/outreach meetings with stakeholder groups are also being planned. The ultimately project goals are to discern the fate of antibiotic residues, ARB and ARG as they move through dairy manure handling systems, identify the efficacy of different manure treatment systems at mitigating antibiotic resistance and extending this knowledge to dairy operators.
Corresponding author, title, and affiliation
Jason Oliver, Postdoctoral Associate at Dept. of Animal Science, Cornell University
This material is based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number 2016-68003-24601. 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.
Project collaborators include: (PD) Diana Aga, University of Buffalo, Dept. of Chemistry (Co-PI); her students Mitch Mayville and Jarod Hurst; (Co-PD) Lauren Sassoubre , University of Buffalo, Dept. of Civil, Structural & Environmental Engineering; (Co-PDs) Stephanie Lansing and Gary Felton, Associate Professors at University of Maryland, Dept. of Environmental Science & Technology; their student Jenna Schueler; (Co-PD) Krista Wigginton, Assistant Professor at University of Michigan, Dept. of Civil & Environmental Engineering; Lutgarde Raskin, Professor at University of Michigan, Dept. of Civil & Environmental Engineering; and their student Emily Crossette.
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. 2017. Title of presentation. Waste to Worth: Spreading Science and Solutions. Cary, NC. April 18-21, 2017. URL of this page. Accessed on: today’s date.
AgSTAR is a collaborative voluntary program of the Environmental Protection Agency (EPA) and United States Department of Agriculture (USDA). AgSTAR promotes the use of anaerobic digestion (AD) systems to advance economically and environmentally sound livestock manure management. AgSTAR has strong ties to industry, government, non-profit and university stakeholders and assists those who enable, purchase or implement anaerobic digesters by identifying project benefits, risks, options and opportunities.
Anaerobic digestion (AD) continues to be a sustainable manure management opportunity with growing interest in innovative business models for project development. AD systems provide a number of benefits, including improved nutrient management, locally sourced renewable energy, and diversified revenue streams for farmers. As energy prices remain low across the country, and interest grows in managing food waste and organics outside of landfills, new business models have been implemented to make these on-farm AD projects viable. This presentation will provide a national overview of the livestock AD sector, explore new AD projects across the U.S., and highlight successful projects with innovative business models.
The presentation will cover several case studies of AD projects on topics including:
Third-party ownership and development of projects;
Food waste collection and boosting project profitability through tip fees and increased biogas production;
Eco-market products from dairy manure fibers; manure-based alternatives to peat moss for the horticulture industry; and
Biogas to vehicle fuel; opportunities and financial considerations.
With only 244 operating on-farm AD projects across the U.S., there exists a great opportunity for market share growth at the approximately 8,000 farms that could support a project. This, coupled with the desire for alternative management of organic waste streams, provides a unique opportunity for this sector to grow in the near future.
A multiple staged digestion system capable of digesting drylot manures is currently under development. The system is currently being validated at the pilot scale with three 1.5 cubic meter batch reactors. The system shows promise with various animal manure wastes as well as other common waste products. The first stage of the process is a dry digestion leachbed process in which the hydrolysis of solid waste products is optimized. The liquid leachate produced by the first stage is then transferred to a storage tank where the leachate is accumulated before use in the last stage. The last stage is optimized for methanogenesis and consists of a high rate methane reactor.
What Have We Learned?
This configuration of system components lends itself to a variety of potential advantages for regional digestion of animal wastes. Wastes of various solids contents can be segregated into the appropriate reactors, with high solids wastes placed in the first stage, moderate solids in the second stage, and primarily soluble wastes can be sent straight to the last stage. This inherent substrate flexibility could enable the construction of regional digesters capable of treating a wide array of wastes. As the solid wastes are dry digested dewatering at the end of the process is less challenging and leads the production of a high nutrient content soil amendment.
Future Plans
Plans are currently in the works to begin scaling this pilot system to build a 100-500kw on farm digester system.
The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.
While EPA AGSTAR has long supported the adoption of anaerobic digestion on dairies and swine farms, they have not historically focused on the use of anaerobic digestion on egg laying and other poultry facilities. This has been because the high solids and ammonia concentrations within the manure make anaerobic digestion in a slurry-based system problematic. Development of enhanced downstream ammonia and solids recovery systems is now allowing for effective digestion without ammonia toxicity. The process also generates dilution water, avoiding the need for fresh water consumption, and eliminating unwanted effluent that needs to be stored or disposed of to fields. The system produces high-value bio-based fertilizers. In this presentation, a commercial system located in Fort Recovery Ohio will be used to detail the process flow, its technologies, and the co-products sold.
Why Examine Anaerobic Digestion on Poultry Farms?
The purpose of this presentation is to supply a case study on a commercial poultry digestion project for production of combined heat and power as well as value-added organic nutrients on a 1M egg-layer facility in Ohio.
What did we do?
In this study we used commercial farm information to demonstrate that poultry digestion is feasible in regard to overcoming ammonia inhibition while fitting well into an existing egg-layer manure management system. Importantly, during the treatment process a significant portion of nutrients within the manure are concentrated for value-added sales, ammonia losses to the environment are reduced, and wastewater production is minimized due to recycle of effluent as dilution water.
What have we learned?
In this study, commercial data shows that ammonia and solids/salts levels that are potentially inhibitory to the biology of the digestion process can be controlled. The control is through a post-digestion treatment that includes ammonia stripping and recovery as ammonium sulfate as well as fine solids separation using a dissolved air flotation process with the addition of apolymer. The resulting treated effluent is sent back to the front of the digester as dilution water for the high solids poultry manure. The separated fine solids and the ammonium sulfate solution are dried using waste engine heat to produce a nutrient-rich fertilizer for off-farm sales. The stable anaerobic digestion process resulting from the control of potential inhibitors that might accumulate in the return water, if no post-treatment occurred, leads to production of a significant supply of electrical power for sales to the grid.
Demonstration at commercial scale shows the promise anaerobic digestion with post-digestion treatment and effluent recycle can play in a more sustainable poultry manure treatment system includingmanaging nutrients for export out of impacted watersheds.
Future Plans
Future plans include continued work with industry in developing and/or providing extension capabilities around novel digestion and post-treatment processes for a variety of manures and on-farm situations. Expansion of such processes to poultry and other on-farm business plans will allow for improved reductions in wastewater production, concentrate nutrients for export out of impacted watersheds and do so within a positive economic business plan.
Authors
Craig Frear, Assistant Professor at Washington State University cfrear@wsu.edu
Quanbao Zhao, Project Engineer DVO Incorporated, Steve Dvorak, President DVO Incorporated
Additional information
Additional information about the corresponding author can be found at http://www.csanr.wsu.edu while information about the poultry project and the industry developer can be found at http://www.dvoinc.net. Numerous articles related to anaerobic digestion, nutrient recovery and separation technologies for climate, air, water and human health improvements can be found at the WSU website using their searchable articles function.
Acknowledgements
This research was supported by funding from USDA National Institute of Food and Agriculture, Contract #2012-6800219814; National Resources Conservation Service, Conservation Innovation Grants #69-3A75-10-152; and Biomass Research Funds from the WSU Agricultural Research Center.
The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.
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Four digesters were constructed out of 55 gallon sprayer tanks. The digestate was 132 L in volume with a dynamic headspace of 76 L. At the bottom of each tank a manifold was constructed from ½” PVC pipe in an “H” configuration and with a volume of approximately 230 mL. The bottom of the manifold had holes drilled in it to allow exchange with the sludge. Tanks were fed 400 g of used top dressing chicken litter (wood shaving bedding) obtained from a local producer (averaging 40% moisture and 15% ash) in 2 L of water through a port in the tank [labeled “1” in figure]. Two hundred mL of air were fed to the manifold through a flow meter [2] 0, 1, 4, or 10 times daily in 15-minute periods at widely spaced intervals by means of an air pump and rotary timer [4]. A gas port [3] at the top of the tank allowed for sampling and led to a wet tip flow meter (wettipflowmeters.com) to measure gas production. Digestate samples were taken out of a side port [5] for measurement of water quality and dissolved gases and overflow was discharged from the tank by means of a float switch wired in line with a ½” PVC electrically actuated ball valve.
