Dairy manure generated on concentrated animal feeding operations is of particular environmental concern due to potentially harmful effects long term storage and land application have on air, water, and soil quality. This project examines effectiveness of design innovations and reduction in capital costs of Anaerobic Digestion. OBJECTIVES: The Agri-environmental and Bioproducts Engineering Research Group, of Washington State University's Department of Biological Systems Engineering, led by Professor Shulin Chen, has conducted basic conceptual modeling and laboratory research on a novel approach to anaerobic digestion (AD) of dairy manure which could potentially reduce the capital cost and improve the technical performance of AD. The innovative approach to AD features co-production of biogas and high-quality, value-added fiber. WSU's approach focuses on addresing inefficiencies in current approaches by optimizing AD treatment of different aspects of the waste stream for both biogs production and additional value-added products. Laboratory and bench-scale studies suggest promising results, which warrant further research and development at pilot scale. Many previous efforts to improve current AD technology have shown promising results in the laboratory, but have not proven effective for commercial application, either due to technical difficulties or poor economic performance. The WSU Research Group believes that it has addressed many of the technical and economic failures of previous attempts to improve AD. APPROACH: Andgar plans to build out a pilot scale AD system to evaluate the "farm-level" technical and economic potential of this technology for commercialization on dairies. Two key novelties of within the design are: (1) the separate treatment of solid and liquid organic materials for multiple end products and (2) the development of a hydrolyzing solids reactor for high quality fiber production that works in consort with a high rate liquid digester for improved efficiency and biogas production. These design innovations will potentially reduce capital costs of AD, enhance efficiency of AD system operation, improve AD suitability for wastes with high solids contents, and improve revenue generation through increased biogas production and high quality fiber for value-added markets. PROGRESS: 2005/05 TO 2007/01 There were several significant findings discovered during the Phase I study of the novel anaerobic digester design. The system produced a means to provide bedding-quality fiber and potentially high-value nursery soil amendment within eight hours of manure flush; thus reducing the time required via composting or post-AD separation or both. Digestion of the entire flush manure flow (minus the fiber) created vector reductions of 90% VFA, 50% COD, 40% VS, and 30% TS. Digestion and corresponding vector reduction were accomplished at reduced hydraulic retention times that allow for at least a 50% reduction, if not considerably more, in overall system volume as compared to existing plug-flow flush designs. Experimental evidence has shown that the digester design will not be prone to clogging via solids or biomass which will result in lower operation and maintenance costs. One major concern is the overall biogas production and subsequent energy balance for the system. Although targets in regard to overall reactor volume and vector reduction were attained, the production of biogas from that vector reduction was lower than hoped for, which in turn resulted in energy balances that are suspect in regard to adequately supplying enough heat energy to run the system during the winter months and in its ability to supply saleable combined heat and power. Additional tests and studies will be performed during a Phase II study to improve the biogas production from the system. IMPACT: 2005/05 TO 2007/01 Reduction in capital costs of Anaerobic Digestion makes the technology more affordable for smaller farms and increases the financial return on the investment. The reduction in capital costs will be due to design innovations. PUBLICATIONS (not previously reported): 2005/05 TO 2007/01 No publications reported this period PROGRESS: 2005/05/15 TO 2006/05/14 In order to construct, run and evaluate the novel digester system, appropriate integration of the system within the existing farm manure system had to be accomplished. Andgar and WSU engineers together designed and engineered the pilot system based on earlier laboratory work accomplished by WSU and on the information culled from the farm mass and flow balances. Complete CAD drawings of each system component as well as the overall system were finalized with Dr. Shulin Chen, registered PE in the state of Washington, giving final professional authorization and stamping of the system design. With additional funds and construction work accomplished by both WSU Facilities and Operation and Andgar Engineering staff, the pilot digester system was integrated within the WSU Dairy Center. This step took much longer than anticipated and lead to the delays which required the earlier 12 month extension. On March 2006, the anaerobic digestion system with all necessary fabrication and installation was completed on-site and start-up was begun. On two separate occasions, during a month long test run of the system, problems with additional engineering and system complications were discovered and with the assistance of our partner, Andgar Corporation, appropriate adjustments were completed. Starting in the third week of May, a month long test run will be initiated again allowing for proper data collection and evaluation. IMPACT: 2005/05/15 TO 2006/05/14 Reduction in capital costs of Anaerobic Digestion makes the technology more affordable for smaller farms and increases the financial return on the investment. The reduction in capital costs will be due to design innovations
