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Anaerobic Digestion in Colorado
Due to the arid climate in Colorado, animal wastes as collected can have a very high solids content. While dairy waste has a solids content of 10-14% as excreted, solids content has been measured as high as 90% on dry lots in Colorado. For wastes containing more than 13% solids, substantial quantities of water may be required for anaerobic digestion. This can add to the cost of operating the digester. In addition, it can result in contamination of previously clean water when groundwater is utilized. Dilution of waste with water is most practical when there is an available source of wastewater to utilize.
Dairies are typically thought to be a very good fit for installation of anaerobic digestion technology. However, waste management methods applied at Colorado dairies differ from other parts of the United States. Because water is so scarce in Colorado, water is not utilized to flush dairy barns as is typically done elsewhere. Instead, manure is often scraped from concrete or dry lots. The result is dry waste with high inorganic content consisting of rocks and sand, particularly when cattle are kept on dry lots. The rocks and sand cause major operational problems for anaerobic digesters and must be removed before the waste is processed. This adds to the complexity, capital cost, and maintenance of an anaerobic digestion system.
While Colorado conditions and typical management practices do create challenges for installation of anaerobic digestion technology, there are technologies that can be a good fit. Plug flow systems in particular work well with the high solids content found in typical Colorado animal waste.
Updated Thursday, May 17, 2012