BACKGROUND: Electricity can be generated directly from sewage sludge with a microbial fuel cell (MFC), combining degradation of organic matter. This study constructed a novel insert-type air-cathode microbial fuel cell (ITAC-MFC) as an alternative to a sediment-type MFC and a two-chambered MFC for the generation of bioelectricity and the degradation of sewage sludge organic matter. Meanwhile, a pH adjustment was carried out to enhance substrate bioavailability of sludge and to suppress methane production in the MFC. RESULTS: A maximum power density of 73 +/- 5 mW m(-2) was obtained at sludge pH 10.0, much higher than those of 33 +/- 3 and 4 +/- 0.5 mW m(-2) obtained at pH 8.0 and 6.0, respectively. It was observed that the soluble chemical oxygen demand (SCOD) of sewage sludge at pH 10.0 was almost three times greater than that at pH 6.0. At the same time, the total chemical oxygen demand (TCOD) removal and coulombic efficiency (CE) at pH 10.0 were also much higher than at the other two conditions. CONCLUSIONS: The results demonstrated that improved electricity production and organic degradation could be achieved by maintaining the sludge pH at 10.0 in an MFC. ITAC-MFC offers an attractive alternative for the environmentally-friendly removal of organic matter in sewage sludge. (C) 2011 Society of Chemical Industry