Enhancement of biohydrogen production from brewers’ spent grain by calcined-red mud pretreatment

• Brewers’ spent grain (BSG) had a suitable C/N ratio for hydrogen (H2) production.
• BSG solubilization increased with the increasing calcined-red mud (CRM) load.
• Higher CRM concentration could cause Maillard reaction and alkaline pH in broth.
• The highest H2 yield was 198.62 ml/g-VS for the 10 g/L of CRM pretreating BSG.
• Modified Gompertz model showed better fit to the data than the first-order model.

This paper investigated the utilization of calcined-red mud (CRM) pretreatment to enhance fermentative hydrogen yields from brewers’ spent grain (BSG). The BSG samples were treated with different concentrations (0.0–20 g/L) of CRM at 55 °C for 48 h, before the biohydrogen process with heat-treated anaerobic sludge inoculum. The highest specific hydrogen production of 198.62 ml/g-VS was obtained from the BSG treated with 10 g/L CRM, with the corresponding lag time of 10.60 h. Hydrogen yield increments increased by 67.74%, compared to the control tests without CRM. The results demonstrated that the CRM could hydrolyze more cellulose and further provided adequate broth and suitable pH value for efficient fermentative hydrogen. The model-based analysis showed that the modified Gompertz model presented a better fit for the experimental data than the first-order model.