In this work, a dark H-2 fermentation process was integrated with a proton-exchange-membrane fuel-cell (PEMFC) system for on-line electricity generation. The H-2 producing system was a continuously stirred anaerobic bioreactor (CSABR) seeded with silicone-immobilized sludge. The CSABR system, using sucrose as the sole carbon substrate, was able to continuously and stably produce H2 for over 300 days at a hydraulic retention time (HRT) of 6 h and an influent sucrose concentration of 30 g COD/l. The maximum H-2 production rate and the optimal H-2 yield were 1.15 +/- 0.08 l/h/l and 3.71 +/- 0.18 mol H-2/mol sucrose, respectively. The H-2 produced from the CSABR system was purified via a CO2 absorber and a silica-gel desiccator, and then the > 99% pure H-2 was fed into a PEMFC system at a rate of 1.72 l/h, generating electricity with a stable electromotive force of 3.30 +/- 0.04 V. The output power was ca. 0.87 W (at 25 degrees C), and the output voltage and current were stably maintained at 2.28 V and 0.38 A, respectively, when connected to a small light emission diode (LED) panel. (c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.