Effect of pre-treating vinasse and inoculum on bio-hydrogen production and production capacity of its co-products in Khuzestan

Vinasse, the effluent of alcohol distilleries, is a highly polluting waste. The high volume of vinasse and its unpleasant odor, along with its acidic properties and high pollution load, has made it one of the most important environmental challenges in Khuzestan. The use of dark fermentation to treat this wastewater is one of the cheapest and most environmentally friendly methods. Hydrogen is a clean fuel and considered as a carrier of renewable energy, if produced biologically. In the present study, the batch production of bio-hydrogen from vinasse by dark fermentation was studied. The effect of inoculum pretreatment (anaerobic digested sludge) and substrate pretreatment (vinasse) on hydrogen production yield were also investigated. The results showed that the use of chloroform as an inoculum pretreatment had increased hydrogen yield very significantly which lead to a yield of 47.8 ± 3.6 Nml/g of initial volatile solids (VS). Also, sodium hydroxide application had a significant effect on vinasse sugars hydrolysis, and the hydrogen production efficiency was increased up to 100 percent by 99.5 ± 0.1 Nml/ g of initial VS. In all treatments, acetic acid and butyric acid were identified as the dominant organic acids in the final fermentation broth. Finally, according to laboratory results and available field information, the production potential of bio-hydrogen, acetic and butyric acid from. vinasse produced in Khouzestan in 2021 was calculated to be 0.003, 0.153 and 0.132 km3, respectively. The results showed that the production of bio-hydrogen from vinasse by dark fermentation is a very efficient method due to the high potential of this gas production.