Efficient Methane Fermentation System with Thermal Treatment for Cow Manure

概要

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A highly-efficient methane fermentation system for screw-pressed cow manure was studied. The system consists of thermal pretreatment, mesophilic methane fermentation, oxidation ditch treatment, and dewatering. In this study, the effect of the thermal pretreatment was first examined by the biogas production rate increase in a bench scale test. Second, a field pilot scale system was built to investigate the entire system efficiency including the post-treatment. The experiment resulted in biogas production of 0.20-0.25 Nm3 CH4/VSkg in the controlled system and 0.26-0.33 Nm3 CH4/VSkg in the thermal system. This suggests that the thermal treatment increased the biogas production by 1.3 times the controlled system. Compared with treatment at 180°C for 30 minutes, thermal pretreatment of cow manure at 160-170°C for 30 minutes suppressed color increase in the treated effluent and helped to suppress dewatering polymer addition. In addition, the system directly treats the methane treatment effluent with the oxidation ditch process, increasing the total nitrogen removal rate.