Abstract
Bio-hydrogen (H2) production in a thermophilic anaerobic bioreactor with carbon dioxide (CO2) utilization at the headspace was investigated at different ratio of Biomass substrate to Microorganism (B/M). A 3 mL volume of 80% NaOH (m/v) solution was continuously hung at the headspace of the bioreactors to capture carbon dioxide. The utilization of CO2 at its headspace, proved to enhance bio H2 production. The highest Cumulative Biohydrogen Yield (CHY) of 131.81±3.47 mL-H2/gVS was measured at the ratio of 8.10 parts of biomass to 0.90 parts of Acclimatized Seed Sludge (ASS), B/M 9, while 4.17 parts of similar biomass to 0.83 parts of ASS (B/M 5) had a biohydrogen production of 90.70±16.67 mL-H2/gVS. The B/M of 6.12 parts of biomass to 0.88 parts of ASS (B/M 7) produced a CHY of 84.72±18.35 mL-H2/gVS while the control bioreactors without CO2 utilization (without and with biomass substrate) yielded a 0.06±0.035 mL-H2/gVS and a 3.27±0.78 mL-H2/gVS respectively. The mechanism of the biofermentation in this anaerobic reaction produced two possible resulting reaction; the acetogenesis of CO2 with H2 and the hydrogenotrophic methanogenesis. These reactions consumes hydrogen in the process to produce methane or acids. The presence of 80% (m/v) NaOH solution at the headspace inside the bioreactors, utilizes the CO2 producing a hydrogen-rich region in space: The highest average H2 yield of 51.83 mL-H2 after 49.1 h with B/M 9 without methane was due to carbon dioxide utilization in the bioreactors. A univariate ANOVA and Pair-wise Tukey HSD statistical analysis revealed that the CHY of B/M9 was significantly higher than the other B/Ms. The highest yield, 55.85 mL-H2/gVS obtained with the bioreactor of B/M 9 was optimum for H2 production. The results concluded that H2 production is also enhanced by CO2 utilization at the headspace.
Highlights
Hydrogen (H2) is a promising alternative to fossil fuels due to its clean and high energy yield (122 kJ/g) and produces only water on combustion, It is environmentally friendly and is extensively used in a wide range of energy and industrial applications (Mizuno et al, 2000; Rifkin, 2002)
Results showed that growth activity phase of the Yongin Sewage Sludge (YSS) starts after a day of acclimation and the optimum potential for hydrogen production is at least 2 days
The Biomass substrate to Microorganism (B/M) ratio of 9 with continuous CO2 capture method using 80% (w/v) NaOH solution provided an enriched H2 region in the atmosphere, which enhanced its generation. The result of this investigation concluded that capturing CO2, with 80%(w/v) NaOH solution in the atmosphere of bioreactors in an anaerobic fermentation favors an enhanced production of H2 and providing a mechanism for H2-rich atmosphere preventing further hydrogenotrophic methanogenesis and acetogenesis in the reaction especially for Biomass to Microorganism (B/M) ratio of 9
Summary
Hydrogen (H2) is a promising alternative to fossil fuels due to its clean and high energy yield (122 kJ/g) and produces only water on combustion, It is environmentally friendly and is extensively used in a wide range of energy and industrial applications (Mizuno et al, 2000; Rifkin, 2002). Most of the studies on H2 production are carbohydrate-based (Bai et al, 2004; Ding et al, 2008; Lin and Lay, 2004; Roychaudhury et al, 1988; Zhang et al, 2003) since these materials can be improved by inhibition of the activity of H2-quenching pathways or by reduction of H2 and CO2 partial pressure (Nath and Das, 2004; Ewan and Allen, 2005; Kim et al, 2008; Nandi and Sengupta, 1998; Hallenbeck and Benemann, 2002; Bai et al, 2004; Ding et al, 2008; Lin and Lay, 2004; Roychaudhury et al, 1988; Zhang et al, 2003; Das and Veziroglu, 2001; Lamed et al, 1988; Oh et al, 2003; Park et al, 2005; Kim et al, 2004)
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