In this study, mesophilic acidogenic fermentation, thermophilic acidogenic fermentation, and thermal hydrolysis process (THP) were compared to generate sludge liquors for bio-energy recovery with microbial electrolysis cells (MECs). The results showed that THP at 170 degrees C was the most effective for hydrolysis of particulate organics in sewage sludge, while fermentation under thermophilic temperature led to the highest accumulation of volatile fatty acids (VFAs) in sludge liquor. However, THP yielded the highest percentage of acetate in VFAs, which resulted in superior MEC performance compared to fermented sludge liquors in terms of current density (2.7 vs. similar to 1.3 A/m(2)), coulombic efficiency (50% vs. 31-34%), bio-H-2 potential (1114 vs. 839-881 mL), and H-2 production rate (50.3 mL/d vs. 28-32 mL/d). The utilization sequence of the VFAs was found to be acetate > butyrate > propionate. Overall, our results show that generating sludge liquors through THP could provide a feasible solution to produce bio-H-2 from sewage sludge; however, coulombic efficiencies should be further improved before practical application. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.