Abstract
The U.S. dairy industry produces roughly 500 billion pounds of manure per year on a wet slurry mass basis, most of which is collected, stored, and applied to cropland. Biodegradation of this manure produces offensive odors and large quantities of methane, a potent greenhouse gas. Anaerobic digestion is a proven treatment method addressing both issues, but economic considerations have prevented its widespread implementation. In an effort to improve the profitability of this process, our research group at the University of Idaho is evaluating a variation of two-phase anaerobic digestion, in which a portion of the organic acids produced during fermentation are used to produce bioplastics, while the remaining material is anaerobically digested to generate methane. This research focused on optimization of the anaerobic digestion component of this system, and specifically on assessing the impact of mixing intensity on digester stability and the potential of a parallel digester configuration to increase methane production.