Wastewater biosolids are abundant renewable resources that are rich in organic matter and offer a low cost potential feedstock for biohydrogen production. Relevant literature indicates that biosolids conversion rates are relatively low and therefore this option is not considered feasible. This study showed that hyperthermophilic bacteria Caldicellulosiruptor bescii could efficiently utilize biosolids as the sole carbon source and produce hydrogen (H-2) for the first time in the literature. Degradability assessment studies were performed in 60 mL serum bottles at 78 +/- 2 degrees C and the results of this study are very promising indeed. Owing to superior H-2 production characteristics of C. bescii, a H-2 yield of 86 mL per gram dry solids was achieved and this is the highest dark fermentative H-2 yield obtained from biosolids so far. Various chromatographic methods were employed to identify the other major fermentation end products and acetic acid was found as the only major fermentation product in the biosolids reactors. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.