Consolidated bioprocessing is a one-step process that allows the direct microbial conversion of cellulosic substrates to ethanol and hydrogen. The fermentation was initially performed in batch cultures, in a pH and temperature controlled reactor using Clostridium thermocellum ATCC 27405. With an objective of increasing the production of ethanol and hydrogen, various types of fed-batch fermentations were investigated: variable volume (VV) fed-batch, fixed volume (FV) fed-batch, and semi-continuous fermentation. Semi-continuous processes were carried out at low (10-15 g/L) and high (20-25 g/L) cellulose concentrations. The maximum ethanol production obtained in batch, VV, FV, semi-continuous with low concentrations and high concentrations were 554 mmol, 336 mmol, 477 mmol, 695 mmol and 741 mmol respectively. In the same order, the total hydrogen production was 288 mmol, 364 mmol, 231 mmol, 434 mmol, and 387 mmol. Overall, the semi-continuous fermentation showed more promise in terms of large-scale deployment compared to batch, VV, and FV fed-batch.