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Construction, Start-Up, and Operation of a Plug Flow Anaerobic Digester on the Michigan State University Dairy Farm

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  2012 Dallas, Texas, July 29 - August 1, 2012  121337182.(doi:10.13031/2013.42141)
Authors:   Louis L Faivor, Dana M Kirk, David E Holzwart
Keywords:   Anaerobic Digestion, Plug-Flow, Biogas Production, Methane, Co-Digestion

In September of 2011, construction was completed on a 225,000 gallon plug flow anaerobic digester at the Michigan State University Dairy Teaching and Research Farm. The anaerobic digester is part of an integrated research complex intended to advance waste to resource projects. Start-up of the digester commenced in late September 2011 with the system utilizing dairy manure mixed with wood shavings as bedding. In November the feedstock blend was expanded to include cafeteria food waste as well as other agricultural waste products (poultry eggs). Biogas was scrubbed of hydrogen sulfide and then utilized to fuel a boiler that supplied the operation with the necessary heat to maintain the digester at mesophillic temperatures. New feedstock is preheated by passing through a heat exchanger prior to entering the digester. This digester was built with a limited amount of monitoring equipment resulting in the need for frequent manual observations to ensure successful operation. Topics addressed in this paper include start-up of the digester, modifications to the system, and how a combination of lab analysis, engineering calculations, and visual observations were used to manage the digester. Lab analysis consisted of regular pH, electrical conductivity (EC), alkalinity, volatile fatty acid (VFA), as well as total and volatile solid measurements. Gas chromatography (GC) was also conducted on a regular basis to ensure an adequate methane concentration for boiler operation, detect changes in system stability, and verify that hydrogen sulfide levels did not become excessive. The result of this research will be the development of a protocol for the start-up and operation of an anaerobic digester especially in situations where automated data collection is limited.

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