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Improvement of Methane Fermentation Process Using Immobilized Methanogens on Bamboo Charcoal

Hayato Tokumoto1, Nishiguchi Kyoko2, Nobuaki Sakuda2, and Hiroyuki Yoshida2. (1) Department of Chemical Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka, Japan, (2) Department of Chemical Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka, Japan

The high speed and efficient methane fermentation process is attained using sub-critical water (Sub-CW) hydrolysis reaction as a pretreatment. However, the growth rate of aceticlastic methanogens was extremely low in methane fermentation process. Therefore, to reduce retention times and volumes of reactors, it is very important to keep the microorganisms and substrate of concentration high in the reactor. Methanogens were immobilized on carbon materials, such as bamboo charcoal, activated carbon, and charcoal. Activated carbon could adsorb 0.05 mmol acetic acid. Immobilized methanogens on activated carbon utilized 54% of 0.05 mmol acetic acid. In contrast, Bamboo charcoal 1 g adsorbed only 0.012 mmol acetic acid. However, immobilized methanogens on bamboo charcoal utilized 0.05 mmol acetic acid completely. Aceticlastic methanogens were counted by modified MPN method. Methane conversion per MPN was drastically increased using immobilized methanogens on bamboo charcoal. Methane formation rate per MPN was about 10-5-10-4 using the anaerobic sludge without support materials. Immobilized methanogens on bamboo charcoal increased methane formation rate per MPN to 10-3. Bamboo charcoal that prevents both methanogens and acetic acid was effective to high speed and efficient methane fermentation for excess sludge using Sub-CW hydrolysis as pretreatment.