Hydrogen production from diluted and raw sugarcane vinasse under thermophilic anaerobic conditions

Two continuous anaerobic fluidized bed reactors (AFBRs) were operated under thermophilic (55 °C) temperature for 150 days to investigate the effect of dark H2 fermentation of diluted and raw sugarcane vinasse on H2 production using mixed seed sludge. Although effective H2 production (52.8% of H2; 0.80 L H2 h−1 L−1; 0.79 mmol gCODadded−1) was observed using an elevated substrate concentration (30,000 mg COD L−1), the optimal operational conditions were found for the AFBR1 (10,000 mg COD L−1) fed with diluted sugarcane vinasse (HRT 6 h; OLR 40 kg COD m−3 d−1), achieving a H2 yield of 2.86 mmol H2 g CODadded−1. H2 production was inhibited by elevated volatile fatty acid (VFA) concentrations (butyric and acetic acids = 3.7 and 3.0 g L−1, respectively) in the raw feedstock. Denaturing gradient gel electrophoresis (DGGE) analyses revealed changes in the bacterial population of the expanded clay biofilm as a function of the substrate concentration.