The energy sector in the U.S. has been pushing for policies such as the Renewable Portfolio Standard (RPS) to mitigate the impacts of GHG emissions. Biogas from anaerobic digesters is a viable form of renewable energy, due to its CH4 composition, it can be used as a replacement for power and heat generation or upgraded and sold as biomethane. This study analyzed the effects of temperature in biogas quality and quantity of dairy cow manure in order to compare two main systems, a CSTR and a covered lagoon. A biochemical methane potential (BMP) test was performed to determine material biodegradability of dairy cow manure with respect to temperature. The results show that all samples are anaerobically biodegradable with samples yielding 86, 168, 440, 475 and 448 L biogas per kg initial VS for 15°C, non-mixed; 20°C, non-mixed; 30°C, non-mixed; 39°C, non-mixed; and 39°C, mixed, respectively. The BMP results demonstrated so significant difference between 30°C, non-mixed; 39°C, non-mixed; and 39°C, mixed, respectively. In addition, the effects of psychrophilic, unregulated, and mesophilic conditions were tested in small scale lab pilot digesters. Results show that mesophilic condition yielded the highest cumulative biogas production, while the psychrophilic and unregulated conditions presented higher methane yield. A life cycle analysis was performed to compare two popular anaerobic digestion systems, a CTSR and a covered lagoon, versus current manure management systems for dairy cow manure. The LCA revealed that both systems have less environmental burdens when compared to current waste management systems and a CSTR has less environmental burdens than a covered lagoon.
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