Date Published: March 13, 2013
Author(s): Daisuke Sasaki, Kengo Sasaki, Atsushi Watanabe, Masahiko Morita, Yasuo Igarashi, Naoya Ohmura.
A cylindrical bioelectrochemical reactor (BER) containing carbon fiber textiles (CFT; BER + CFT) has characteristics of bioelectrochemical and packed-bed systems. In this study, utility of a cylindrical BER + CFT for degradation of a garbage slurry and recovery of biogas was investigated by applying 10% dog food slurry. The working electrode potential was electrochemically regulated at −0.8 V (vs. Ag/AgCl). Stable methane production of 9.37 L-CH4 · L−1 · day−1 and dichromate chemical oxygen demand (CODcr) removal of 62.5% were observed, even at a high organic loading rate (OLR) of 89.3 g-CODcr · L−1 · day−1. Given energy as methane (372.6 kJ · L−1 · day−1) was much higher than input electric energy to the working electrode (0.6 kJ · L−1 · day−1) at this OLR. Methanogens were highly retained in CFT by direct attachment to the cathodic working electrodes (52.3%; ratio of methanogens to prokaryotes), compared with the suspended fraction (31.2%), probably contributing to the acceleration of organic material degradation and removal of organic acids. These results provide insight into the application of cylindrical BER + CFT in efficient methane production from garbage waste including a high percentage of solid fraction.
Recycling of the huge organic fraction in municipal solid wastes such as garbage and waste from the food industry has been long-awaited (Haruta et al. 2005). Anaerobic digestion using methane fermentation is an effective technology for recovering methane gas as a renewable energy source. It is a low-cost process and produces little residual sludge (Ahring 2003; Forster-Carneiro et al. 2008). Various processes have been exploited to increase the efficiency of methane fermentation. Thermophilic packed-bed systems have been reported to be one of the high-performance reactor designs (Sasaki et al. 2007; Ueno et al. 2007). In the packed-bed system, supporting materials were packed to retain microorganisms and thereby enable operation at a high organic loading rate (OLR) and short hydraulic retention time (HRT; Sasaki et al. 2010a). In our previous study, carbon fiber textiles (CFT) that have surface hydrophobicity and porous structure for better retention of microorganisms were used as supporting materials (Sasaki et al. 2010a).
The authors declare that they have no competing interests.