Investigation of Energy Recovery System from Raw Garbage by Thermophilic Methane Fermentation with Fuel Cell

A thermophilic methane fermentation system for garbage combined with a fuel cell has been developed and evaluated for the feasibility in a NEDO (the New Energy and Industrial Technology Development Organization, Japan) project. The daily average of 140kg of garbage collected from a shopping mall was treated in the down-flow anaerobic packed-bed reactor operated at 55°C.Based on the results, it was shown that the methane fermentor could maintain stable production of biogas containing 60–70% of methane, on the average of 233Nm3-biogas from 1,000 kg of garbage, in spite of fluctuations in organic loading to the reactor (operated at the organic loading between 10 – 30 kg T-CODcr/m3/day). The removal efficiencies of T-CODcr, SS and n-hexane extractable in the bioreactor were 87%, 90% and 96%, respectively. Corrosive gas components such as hydrogen sulfide and ammonia were successfully removed to below the detectable limits using a dry gas purifier packed with iron oxide pellets and granular activated carbon.When the biogas with average methane content varying between 67 and 93% was supplied instead of town gas, no apparent problems for practical application of the system were experienced during the project, though the efficiency of the fuel cell decreased by approx 2%.