Hydrogen gas production from waste ground wheat by dark and light fermentations

Bio-hydrogen gas production from waste ground wheat powder solution was investigated using batch and continuous dark and light fermentation systems. Continuous experiments were conducted at optimum operation conditions that were determined during batch experiments. Hydrogen production yield and specific hydrogen production rate were considered as the criteria for performance comparison. Combined fermentation experiments were conducted after completing dark and light fermentation experiments.In dark fermentation experiments heat pre-treated anaerobic sludge was found to be the most effective bacterial culture compared to pure cultures. Effects of sludge pre-treatment method, medium composition and initial wheat powder and biomass concentrations on hydrogen production rate and yield were investigated.Hydrogen production by light fermentation using volatile fatty acid containing dark fermentation effluent was investigated under different conditions. Hydrogen production performances of pure Rhodobacter sphaeroides species and their combinations were compared and the mixed culture was found to be the most efficient culture for light fermentation. The optimum initial total volatile fatty acid, ammonium nitrogen and biomass concentrations and the most suitable light source and intensity were determined.In combined dark and light fermentations of wheat powder solution, the optimum light to dark biomass ratio, initial biomass and waste wheat powder concentrations were determined. Effects of light source, light intensity and lighting regime on hydrogen production rate and yield were investigated.Finally continuous experiments of combined dark and light fermentation were performed using a hybrid annular bio-reactor in order to investigate the effects of hydraulic residence time (HRT) on hydrogen production rate and yield.