**4.1.2 IRSOFC operating on biogas**

The SOFC testing system and automatic gas chromatograph were connected to the methane fermentation reactor placed in Tosu Kankyo Kaihatsu Ltd. as shown in Fig. 8 (Shiratori et al., 2010a). Garbage collected in Tosu-city of Saga prefecture was mixed with water resulting in waste slurry. After materials unsuitable for anaerobic fermentation were filtered out, cattle manure was added to the slurry followed by the treatment with acid and methane fermentation processes to produce biogas (mixture of CH4 and CO2) containing 790 ppm H2S. The raw biogas was passed through a desulfurizer packed with FeO pellets 20 cm3 in size. The typical composition of desulfurized biogas sampled from the fermentation reactor is listed in Table 4. The concentration of H2S was less than 0.5 ppm. The concentrations of the other fuel impurities, CH3SH, Cl2, HCl, NH3 and siloxane, were below the detection limits (2 ppb, 60 ppb, 0.4 ppm, 0.6 ppm and 10 ppb, respectively), indicating that this gas can be fed directly into a SOFC (Haga et al., 2008). In any case, 1 ppm level H2S contamination must be taken into account even after desulfurization treatment. The experimental setup for testing IRSOFC operating on biogas has been described elsewhere (Shiratori et al., 2010a). The pressure controlled real biogas (0.1 MPa) was directly distributed to the SOFC at 800 oC and the gas chromatograph with flow rates of 25 and 140 ml min-1, respectively, in order to evaluate the electrochemical performance with simultaneous monitoring of biogas composition. In this experiment, water vapor in the real biogas was removed by a cold trap thermostated at 0 oC. Dry air was supplied to the cathode side with a flow rate of 50 ml min-1

Fig. 8. Connection of SOFC test system and gas chromatograph with the methane fermentation reactor in Tosu-city, Japan (Shiratori et al., 2010a, 2010b).


Table 4. Typical composition of the actual desulfurixed biogas (Shiratori et al., 2010a).
