Development of electric pretreatment method for enhancement of dark fermentative hydrogen production

Abstract

As alternative renewable energy sources of fossil fuels, hydrogen (H2) is considered a promising energy. In particular, dark fermentative H2 production (DFHP) from biomass has gained recognition as an environmental friendly approach, because of its ability to play a dual role in waste degradation and energy production. Among the various affecting factors, pretreatment procedure, such as inoculum preparation for the screening H2-producing bacteria and feedstock pretreatment for the enhancement of biodegradability, is fundamental and essential step. Up to date, numerous methods including chemical and heat pretreatment or combined pretreatment are mainly used in mixed culture and feedstock to obtain inocula and hydrolysis, respectively. However, from the economic and practical points of view, the development of the more easily applicable pretreatment should be required. Upon this research background, the aim of this work is development of a novel pretreatment method for inoculum and feedstock using electricity. Firstly, electricity was newly adopted as a pretreatment method for inoculum preparation in DFHP. Various voltages (5-20 V for 10 min) were applied, and the feasibility and efficiency of this method were compared with those of heat pretreatment (90 oC for 20 min). Both the highest H2 yield, 1.43 mol H2/mol hexoseadded, and the highest production rate, 101.4 mL H2/L/h, were observed at 10 V. While RNA concentration of above 100 mg/L was maintained up to 10 V, it was decreased at an applied voltage of 20 V, where the worst performance was observed. Microbial analysis results confirmed that only H2 producing bacteria (HPB) were detected with electric pretreatment, while non-HPB coexist with heat and electric (5 V) pretreatment. Then, electric pretreatment conditions (applied voltage, reaction time, and distance of electrode) were optimized using response surface methodology (RSM) with a Box-Behnken Design (BBD). The significant factors for electric pretreatm...