Organic loading rate impact on biohydrogen production and microbial communities at anaerobic fluidized thermophilic bed reactors treating sugarcane stillage

This study aimed to evaluate the effect of high organic loading rates (OLR) (60.0-480.00 kg COD m−3 d−1) on biohydrogen production at 55 °C, from sugarcane stillage for 15,000 and 20,000 mg COD L−1, in two anaerobic fluidized bed reactors (AFBR1 and AFBR2). It was obtained, for H2 yield and content, a decreasing trend by increasing the OLR. The maximum H2 yield was observed in AFBR1 (2.23 mmol g CODadded-1). The volumetric H2 production was proportionally related to the applied hydraulic retention time (HRT) of 6, 4, 2 and 1 h and verified in AFBR1 the highest value (1.49 L H2 h−1 L−1). Among the organic acids obtained, there was a predominance of lactic acid (7.5-22.5%) and butyric acid (9.4-23.8%). The microbial population was set with hydrogen-producing fermenters (Megasphaera sp.) and other organisms (Lactobacillus sp.).