Biological hydrogen production by anaerobic fermentation

Abstract

Considering the energy security and the global environment, there is a pressing need to develop non-polluting and renewable energy sources. Alternatively, hydrogen is a clean energy carrier, producing water as its only by-product when it burns. Anaerobic bioconversion of organic wastes to hydrogen gas is an attractive option that not only stabilizes the waste/wastewater, but also generates a benign renewable energy carrier. The purposes of this study were to determine the kinetics of hydrogen production using different characteristics of substrates and to evaluate hydrogen production potential from different operating conditions in continuous operation. The growth kinetics of hydrogen-producing bacteria using three different substrates including sucrose, non-fat dry milk (NFDM), and food waste were investigated through a series of batch experiments. The results demonstrated that hydrogen production potential and hydrogen production rate increased with an increasing substrate concentration. The maximum hydrogen yields from sucrose, NFDM, and food waste were 234, 119, and 101 mL/g COD, respectively. The low pH (pH < 4) inhibited hydrogen production and resulted in lower carbohydrate fermentation at high substrate concentrations. The Michaelis-Menten equation was employed to model the hydrogen production rate at different substrate concentrations. The equation gave a good approximation of the maximum hydrogen production rate and the half saturation constant (KS) with correlation coefficient (R ) over 0.85. The values of half saturation constant (KS) for sucrose, NFDM, and food waste were 1.4, 6.6, and 8.7 g COD/L, respectively. Based on the Ks values, the substrate affinity of the enriched hydrogen-producing culture