The aim of this study is to investigate the bio-H-2 production via dry anaerobic co-fermentation of organic fraction of municipal solid waste (OFMSW) with protein and calcium-rich substrates such as gelatin solid waste (GSW) and paperboard mill sludge (PMS). Co-fermentation of OFMSW/GSW/PMS significantly enhanced the H-2 production (HP) and H-2 yield (HY). The maximum HP of 1082.5 +/- 91.4 mL and HY of 144.9 +/- 9.8 mL/gVS(removed) were achieved at a volumetric ratio of 70% OFMSW: 20% GSW: 10% PMS. COD, carbohydrate, protein and lipids conversion efficiencies were 60.9 +/- 4.4%, 71.4 +/- 3.5%, 22.6 +/- 2.3% and 20.5 +/- 1.8% respectively. Co-fermentation process reduced the particle size distribution which is favorably utilized by hydrogen producing bacteria. The mean particle size diameters for feedstock and the digestate were 939.3 and 115.2 mu m, respectively with reduction value of 8.15-fold in the mixtures. The volumetric H-2 production increased from 4.5 +/- 0.3 to 7.2 +/- 0.6 LH2/L-substrate at increasing Ca+2 concentrations from 1.8 +/- 0.1 to 6.3 +/- 0.5 g/L respectively. (C) 2015 Elsevier Ltd. All rights reserved.