P-Rich Solids and Ammonia Sulfate Fertilizer as Co-Products from Anaerobic Digestion

1. Fiber #4 Fiber #3 Fiber #2 Fiber #1 Peat Control P-Rich Solids and Ammonia Sulfate Fertilizer as Co-Products from Anaerobic Digestion Anping Jiang, Tianxi Zhang, Jason Steubel, Hal Collins, Eric Jessup, Ken Casavant, Craig Frear, Shulin Chen WSU, in cooperation with Vander Haak Dairy and Andgar Corporation was awarded a BIOAg Integrated Grant to pilot-test, evaluate the fertilizer potential, and assess the economic and business potential of a patent-pending nutrient recovery process that works in series with an anaerobic digester. Introduction Manure management on dairies is an important concern. Air, water and climate issues as well as odor are important parameters that are potentially impacted by handling and processing of manure on dairies. Another important issue is the build-up of nutrients on the farm, often resulting in too much nutrients to land-apply to limited land resources. Thus, beyond installing anaerobic digesters on farms, producers must also look into installing nutrient recovery units that simultaneously allow for added-value and removal of excess nutrients from the farm gate. The Vander Haak Dairy Digester, Lynden, WA The Process In the process, effluent from the digester is first sent through a screen separator to remove the course fibrous solids from the stream. These fibrous solids are treated with a WSU patented system to yield a peat-replacement product and bedding-replacement. The remaining effluent is further treated through a series of screens and flocculants to further reduce the solids in the waste stream. WSU studies have shown that these smaller solids represent the vast majority of phosphorous and as result can be sold as P-rich solids. The remaining liquid stream is then sent through a closed-loop ammonia stripping and recovery unit to remove the ammonia from the liquid stream and concentrate it as ammonia sulfate fertilizer. The process requires acid and base inputs to accomplish the process, and the pH is eventually returned to neutral for long-term storage of the liquid until field-application through a biogas-scrubbing process that yields a higher value, and engine-friendly biogas more rich in methane and removed of harsh acidic compounds such as hydrogen sulfide. Value-Added Fiber Digested Dairy Fiber with WSU patented amendments Digested Dairy Fiber with no amendments Flow Chart of Entire Nutrient Process Nutrient Optimization and On-going Work As of October 15, the entire pilot-system is operational. Optimization and testing of the pilot-process is scheduled to proceed through February 1 of 2009 with product samples being analyzed in the laboratory and greenhouse level testing of fertilizer value occurring through the Winter. Field testing of the optimized fertilizer will begin in February-March at the Prosser Research Fields. Economic Science professors will collect all available inputs and generate a techno-economic report and business plan regarding the viability of the process for market entry. The project should be complete in the Summer of 2009.