Thermophilic H-2 production from glucose was studied at 55-64 degreesC for 234 days using a continuous trickling biofilter reactor (TBR) packed with a fibrous support matrix. Important parameters investigated included pH, temperature, hydraulic retention time (HRT), and glucose concentration in the feed. The optimal pH and temperature were 5.5 and 60 degreesC, respectively. With decreasing HRT or increasing inlet glucose concentration, volumetric H-2 production rate increased but the H-2 production yield to glucose decreased gradually. The biogas composition was almost constant at 53 +/- 4% (v/v) of H-2 and 47 4% (v/v) of CO2. No appreciable CH4 was detected when the reactor was under a normal operation. The carbon mass balance showed that, in addition to cell mass, lactate, n-butyrate, CO2, and acetate were major products that comprised more than 85% of the carbon consumed. The maximal volumetric H-2 production rate and H-2 yield to glucose were 1,050 +/- 63 mmol H-2/l(.)d and 1.11 +/- 0.12 mol H-2/mol glucose, respectively. These results indicate that the thermophilic TBR is superior to most suspended or immobilized reactor systems reported thus far. This is the first report on continuous H-2 production by a thermophilic TBR system. (C) 2004 Wiley Periodicals, Inc.