In present work our objective was to find out the potential substrates for fermentative hydrogen production using microbial culture of Bacillus firmus NMBL-03 isolated from municipal sludge. A wide variety of substrates (glucose, xylose, arabinose, lactose, sucrose, and starch) and carbohydrate rich waste products (bagasse hydrolysate, molasses, potato peel and cyanobacterial mass) have been used for dark fermentative hydrogen production. All studies were done at optimized physico-chemical conditions. Among all substrates glucose, arabinose, lactose, starch, molasses and bagasse hydrolysate were found to be the favorable substrates for hydrogen production. The highest VHPR i.e. 177.5 +/- 7.07 ml/L.h (7.95 +/- 0.29 mmol H-2/L.h) and maximum H-2 production (22.58 +/- 2.65 mmol H-2/L) was achieved using starch as the substrate. The maximum yield 1.29 +/- 0.11 mol H-2/mol reducing sugar was obtained from bagasse hydrolysate as substrate. Butyrate and acetate were detected as the end product in all the cases while lactate was also detected from glucose and cyanobacterial hydrolysate. Since considerable amount of H-2 also evolved when cyanobacterial mass was used, therefore this microbe can be exploited for hydrogen production through a three stage integrated system. Residual carbohydrate containing biomass left after cyanobacterial H-2 production can be utilized in dark fermentative H-2 production. Spent media obtained after dark fermentative H-2 production contain considerable amount of volatile fatty acids that can be potential substrate for photo fermentative H-2 production. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.