Evaluation of hydrogen and methane production from sugarcane vinasse in an anaerobic fluidized bed reactor

•Mixture of vinasse:glucose (1:3) resulted in a hydrogen yield of 3.07 mmol H2 g COD−1added.•Longer hydraulic retention time was more suitable for H2 production from vinasse.•CH4 was co-produced along with H2 despite low pH and low hydraulic retention time.•Unusual culture mixture was found for H2 production: Prevotella sp. and Megasphaera sp.

This study evaluated the hydrogen and methane production from sugarcane vinasse in an anaerobic fluidized bed reactor. Two reactors were operated with two different substrate concentrations: R5 (5 g COD L−1) and R10 (10 g COD L−1). During the first stage, glucose was used as the primary carbon source; vinasse was then added from 0% to 100% of the organic source in hydraulic retention time (HRT) of 6 h. Later, HRT was changed to 4, 2 and 1 h.The best hydrogen production rate was 0.57 L h−1 L−1 (R5, HRT = 1 h, 100% vinasse). The best hydrogen yield was 3.07 mmol H2 g−1 CODadded (R5, HRT = 6 h, vinasse:glucose = 1:3). Main metabolites were ethanol, butyric acid, propionic acid and methanol. Denaturing gradient gel electrophoresis analysis identified Prevotella sp. and Megasphaera sp. belonging to the Bacteria domain and Methanobacterium sp. and Methanosphaera sp. belonging to the Archaea domain.