Implications of urine-to-feces ratio in the thermophilic anaerobic digestion of swine waste.

K S Creamer, C M Williams, Y Chen, J J Cheng

Animal and Poultry Waste Management Center, North Carolina State University, Raleigh, North Carolina 27695-7608, USA. kurt_creamer@ncsu.edu

Water environment research : a research publication of the Water Environment Federation 2008 Mar

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Thermophilic anaerobic digestion of swine manure represents a potential waste treatment technology to address environmental concerns, such as odor emissions and removal of pathogenic microorganisms. However, there are concerns relative to the stability of this process when swine manure is the sole substrate. In this study, the potential of biogas production from swine manure as the sole substrate under thermophilic (50 degrees C) conditions was investigated in the laboratory, to determine whether separation of urine and feces as part of the waste collection process would benefit anaerobic digestion. Effluent from a continuously stirred tank reactor was used as the inoculum for batch tests, in which the substrate contained three different concentrations of urine (urine-free, as-excreted urine-to-feces ratio and double the as-excreted urine-to-feces ratio). Inocula were acclimated to these same urine-to-feces ratios to determine methane production. Results show that both urine-free and as-excreted substrates were not inhibitory to anaerobic inocula. Anaerobic microorganisms can be readily acclimated to substrate with double the as-excreted urine concentration, which contained nitrogen concentrations up to 7.20 g/L. Cumulative methane production reached similar levels in the batch tests, regardless of the substrate urine concentration.

Citation

K S Creamer, C M Williams, Y Chen, J J Cheng. Implications of urine-to-feces ratio in the thermophilic anaerobic digestion of swine waste. Water environment research : a research publication of the Water Environment Federation. 2008 Mar;80(3):267-75