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 a polymer. 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 including managing 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.