Effects of pH and hydraulic retention time on hydrogen production versus methanogenesis during anaerobic fermentation of organic household solid waste under extreme‐thermophilic temperature (70°C)

Abstract

Two continuously stirred tank reactors were operated with household solid waste at 70 degrees C, for hydrogen and methane production. The individual effect of hydraulic retention time (HRT as 1, 2, 3, 4, and 6 days) at pH 7 or pH (5, 5.5, 6, 6.5, 7) at 3-day HRT was investigated on the hydrogen production versus methanogenesis. It was found that at pH 7, the maximum hydrogen yield was 107 mL-H(2)/g VS(added) (volatile solid added) but no stable hydrogen production was obtained as after some time methanogenesis was initiated at all tested HRTs. This demonstrated that sludge retention time alone was not enough for washing out the methanogens at pH 7 under extreme-thermophilic conditions. Oppositely, we showed that keeping the pH level at 5.5 was enough to inhibit methane and produce hydrogen stably at 3-day HRT. However, the maximum stable hydrogen yield was low at 21 mL-H(2)/g VS(added).

Biohydrogen production from wheat straw hydrolysate by dark fermentation using extreme thermophilic mixed culture

“…During steady state period (days 32-39), acetate concentration was increased, while lactate concentration was significantly decreased, which resulted in higher hydrogen production with a yield of 178.0 AE 10.1 mL-H 2 / g-sugars. Similar tendencies reported in the literature, moderate-to high hydrogen yields (78.0-414.0 mL-H 2 /gsugars) were achieved when acetate was the dominant metabolic pathway Kotsopoulos et al, 2006;Yokoyama et al, 2009;Zheng et al, 2008), while lower hydrogen yields of 21.2 and 52.3 mL-H 2 /g-sugars, respectively, were associated with higher lactate concentration and coincident with unstable or overloading conditions (Koskinen et al, 2008;Liu et al, 2008a). Lignocellulosic biofuel production is not yet economically competitive with fossil fuels, therefore, a successful utilization of all sugars is important for improving the overall economy (Hallenbeck et al, 2009).…”

Factors influencing the degradation of garbage in methanogenic bioreactors and impacts on biogas formation

“…Methane fermentation is carried out at various temperature ranges: generally under mesophilic (around 35°C) and thermophilic (around 55°C) conditions and additionally under a psychrophilic (4-20°C) or an extreme thermophilic (70°C) condition for the hydrolytic process (Sekiguchi et al 2001;Liu et al 2008). In methanogenic bioreactors, a neutral pH (6.6-7.6) is usually maintained because this is the preferred pH range of methanogenic archaea.…”

Hydrogen production and anaerobic decolorization of wastewater containing Reactive Blue 4 by a bacterial consortium of Salmonella subterranea and Paenibacillus polymyxa

“…Since fermentative hydrogen production is affected by pH, temperature as well as the nature of the microorganisms. pH is crucial due to its effects on hydrogenase activity, metabolism pathways (Lay 2000;Jun et al 2008;Liu et al 2008) and microbial communities (Fang and Liu 2002). In general, the dominant metabolism in a mixed acidogenic culture depends strongly on pH of the microbial culture and hydrogen production is suppressed by both low and high pH (Chen et al 2002).…”