Biohydrogen production from crude glycerol by two stage of dark and photo fermentation

•5 Times dilution of the dark fermentation effluent was suitable for hydrogen production in photo fermentation.•Supplementation with 2 mM glutamate gave the highest hydrogen production in photo fermentation.•The total hydrogen yield in the two-stage processes was 6.42 mmol H2/g COD consumed.

Hydrogen production from crude glycerol by two-stage processes of dark fermentation using Klebsiella sp. TR17 and photo fermentation using Rhodopseudomonas palustris TN1 (Rps. palustris TN1) was investigated in batch experiments. In dark fermentation, the cumulative hydrogen production and hydrogen yield was 64.24 mmol H2/L and 5.74 mmol H2/g COD consumed, respectively with 80.21% of glycerol conversion rate. The dark fermentation effluent (DFE) was employed for photo fermentation. Effect of DFE concentrations (0–5 times dilution), with and without supplementation of yeast extract (2.3 g/L) + NaHCO3 (0.63 g/L), and glutamate (2–8 mM) were optimized. The optimal conditions for hydrogen production from Rps. palustris TN1 were 5 times dilution of DFE without the supplement of yeast extract + NaHCO3, and 2 mM glutamate. Under the optimum conditions, the cumulative hydrogen production of 3.12 mmol H2/L and hydrogen yield of 0.68 mmol H2/g COD consumed was obtained. The total hydrogen yield of two-stage processes was estimated to be 6.42 mmol H2/g COD consumed which was 10.4% of the theoretical yield.