<p>This study aimed at evaluating H₂ production and value-added products during the co-digestion process of cassava processing wastewater (CW) and glycerol (50% CW and 50% glycerol on a COD basis) in an anaerobic fluidized bed reactor (AFBR) under mesophilic conditions (30 ± 1&#xa0;°C), at a hydraulic retention time (HRT) of 4&#xa0;h, and an organic loading rate (OLR) ranging from 6 to 75&#xa0;g chemical oxygen demand (COD).L^− 1.d^− 1. The acidogenic reactor exhibited optimal performance at OLR 45 gCOD.L^− 1.d^− 1, with a H₂ yield (HY) corresponding to 1.13 mmol H₂.g^− 1COD and H₂ production rate (HPR) of 1.21&#xa0;L H₂.L^− 1.d^− 1, as well as the production of ethanol and propionic acid. By means of the 16&#xa0;S rRNA sequencing, a similar microbial profile was observed between different OLRs (45 gCOD.L^− 1.d^− 1 and 75 gCOD.L^− 1.d^− 1), effectively enriching H₂-producing bacteria from the seed sludge, and a high relative abundance of <i>Lactobacillus</i> was identified in both conditions. The butyric acid (HBu) and acetic acid (HAc) production pathways, highly related to H₂ production, were possibly favored, especially due to the activity of the inferred enzyme acetate CoA-transferase and short-chain acyl-CoA dehydrogenase for HBu generation and pyruvate synthase, acetaldehyde dehydrogenase and acetate-CoA ligase in the generation of HAc.</p> Graphic Abstract <p></p>