| Project: COL00696 |
Department: Civil & Environmental Engineering |
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PIs: Sharvelle, SE |
| Title: Development of a Two-Stage Anaerobic Digester for Generation of Energy from Dairy and Feedlot Wastes in Colorado |
| Begin Date: 07/01/2009 |
Term Date: 06/30/2011
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Most recent project status:
Revised
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| Objectives: Dr. Sharvelle's research group has conducted several feasibility studies for installation of anaerobic digesters at dairy facilities in the state of Colorado through funds previously received by AES (2008) and Colorado Governors Energy office. A major barrier has been identified through these studies which is unique to Colorado and the arid west. Due to limited water supply, dairy producers do not typically flush barns to remove waste. Therefore, the waste generated by typical dairy operations in Colorado has very high solids content and is not suitable for classic anaerobic digestion technologies. One promising concept for digestion of low moisture waste materials is a two-stage digester. However, this technology has not yet been applied to animal manure. The primary objective of this work is to develop a two-stage anaerobic digestion process capable of generating methane from dairy and feedlot wastes. This digester process will be developed through a set of laboratory scale tests and a demonstration project at Colorado Corrections Industry (CCI) located in Canon City, CO. Results from lab-scale reactor operations will provide guidance on the design of the proposed two-stage anaerobic digester. Success will be demonstrated through operation of the pilot scale unit at CCI. Guidance for design of the two-stage digester will be generated from laboratory and pilot scale testing and will apply broadly to the design and operation of two-stage digestion of dry livestock wastes. |
| Approach: This project will consist of three components; preliminary lab-scale experiments, a pilot scale demonstration project, and process optimization through laboratory and pilot scale reactors. The goal of the first component of the project, laboratory scale experiments, is to optimize the organic content of leachate collected from the first stage of the system. One problem encountered with the leachate bed when manure is the substrate is inefficient water flow and distribution throughout the system. Other researchers4 were able to overcome this problem by the addition of pistachio hulls. Here, agricultural waste products readily available in Colorado will be examined as additives to the manure to improve the efficiency of the hydrolysis stage. Several waste combinations will be evaluated. Scraped dairy manure and feedlot manure will each be evaluated alone and each will be combined with hay, corn stalks, and waste straw to evaluate leachate production potential. The required duration to achieve optimal leachate strength will also be determined. Parameters to be evaluated include leachate chemical oxygen demand (COD) and biochemical methane potential. The leachate bed material will be evaluated for COD, total solids, and volatile solids. Lab-scale operations will provide guidance on optimal design for a pilot-scale system to be located at CCI. Several wastes are generated at this site including diary manure, horse manure, and aquaculture waste. Colorado GEO has provided funding for all materials for the pilot scale system which will be constructed this summer. Funds from AES will enable sampling and analysis of performance on the demonstration system. Influent and effluent quality will be monitored in addition to quantity and composition of biogas generated. The pilot-scale system will be constructed in a modular fashion so that it can easily be upscaled to a full size energy generation system. Process optimization will also be required for successful implementation of the proposed two-stage system. This will be achieved through both lab-scale and pilot-scale studies. Methods will be evaluated to maximize water reuse potential through removal of ammonia from digested wastewater. In addition, methods to effective compost spent solids materials after leachate collection will be evaluated. |
| Keywords: dry digestion,
anaerobic digester,
animal waste management,
greenhouse gas reduction,
methane generation,
waste to energy,
renewable energy |
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