Ground waste wheat was subjected to combined dark and light batch fermentation for hydrogen production. The dark to light biomass ratio (D/L) was changed between 1/2 and 1/10 in order to determine the optimum D/L ratio yielding the highest hydrogen formation rate and the yield. Hydrogen production by only dark and light fermentation bacteria was also realized along with the combined fermentations. The highest cumulative hydrogen formation (CHF = 76 ml), hydrogen yield (176 ml H(2) g(-1) starch) and formation rate (12.2 ml H(2) g(-1) biomass h(-1)) were obtained with the D/L ratio of 1/7 while the lowest CHF was obtained with the D/L ratio of 1/2. Dark-light combined fermentation with D/L ratio of 1/7 was faster as compared to the dark and light fermentations alone yielding high hydrogen productivity and reduced fermentation time. Dark and light fermentations alone also yielded considerable cumulative hydrogen, but slower than the combined fermentation. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved