@article{creamer_williams_chen_cheng_2008, title={Implications of urine-to-feces ratio in the thermophilic anaerobic digestion of swine waste}, volume={80}, ISSN={["1554-7531"]}, DOI={10.2175/106143007X184717}, abstractNote={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°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.}, number={3}, journal={WATER ENVIRONMENT RESEARCH}, author={Creamer, K. S. and Williams, C. M. and Chen, Y. and Cheng, J. J.}, year={2008}, month={Mar}, pages={267–275} }
 @misc{chen_cheng_creamer_2008, title={Inhibition of anaerobic digestion process: A review}, volume={99}, ISSN={["1873-2976"]}, DOI={10.1016/j.biortech.2007.01.057}, abstractNote={Anaerobic digestion is an attractive waste treatment practice in which both pollution control and energy recovery can be achieved. Many agricultural and industrial wastes are ideal candidates for anaerobic digestion because they contain high levels of easily biodegradable materials. Problems such as low methane yield and process instability are often encountered in anaerobic digestion, preventing this technique from being widely applied. A wide variety of inhibitory substances are the primary cause of anaerobic digester upset or failure since they are present in substantial concentrations in wastes. Considerable research efforts have been made to identify the mechanism and the controlling factors of inhibition. This review provides a detailed summary of the research conducted on the inhibition of anaerobic processes. The inhibitors commonly present in anaerobic digesters include ammonia, sulfide, light metal ions, heavy metals, and organics. Due to the difference in anaerobic inocula, waste composition, and experimental methods and conditions, literature results on inhibition caused by specific toxicants vary widely. Co-digestion with other waste, adaptation of microorganisms to inhibitory substances, and incorporation of methods to remove or counteract toxicants before anaerobic digestion can significantly improve the waste treatment efficiency.}, number={10}, journal={BIORESOURCE TECHNOLOGY}, author={Chen, Ye and Cheng, Jay J. and Creamer, Kurt S.}, year={2008}, month={Jul}, pages={4044–4064} }