Design, fabrication, and testing of a jacketed anaerobic digester for biogas production through the Co-digestion of rice straw and goat manure / Keith Mark S. Sol, Laurence Taroma, Harold M. Viernes

UTHESIS (Bachelor of Science in Chemical Engineering)

Bibliography: leaves 65-71

This study investigated the performance of the designed and fabricated jacketed anaerobic digester for the co-digestion of rice straw and goat manure to produce biogas, which comprised mainly of methane (CH4) and carbon dioxide (CO2). The process operated at mesophilic conditions where methanogens break down the organic matter and convert it into methane-rich gas in an oxygen-free environment. The biodigester, designed to fit a 20 L volume of feedstock with a safety volume of 10%, incorporated a jacket for temperature control and utilized a 6 flat blade disc impeller for substrate mixing. The results of the co-digestion of 1:1 rice straw to goat manure showed an average of 72,691.7 ml of biogas for a 20-day cycle. Results also indicate a consistent peak in biogas production on the 7th day of fermentation. Methane and carbon dioxide contents in the biogas were determined using a syringe test. Methane production exhibited an exponential increase from Day 3 to Day 7, followed by a stationary phase, while carbon dioxide showed a similar trend. The results of the study yielded methane amounts of 39200.61 ml, 39767.99 ml, and 40050.3 ml, respectively for the three trials and carbon dioxide amounts of 32,461.39 ml, 32,915.01 ml,33,679.7 ml, respectively. The average efficiency of the biodigester was computed as 71.82%. Thus, the study revealed that the co-digestion of rice straw and goat manure were potential sources for biogas production. These findings also provide valuable insights into the design and operation of jacketed anaerobic biodigesters for sustainable biogas production from agricultural waste.