Continuous Biohydrogen Production Research Articles

Effects of arsenite and variation of microbial community on continuous bio-hydrogen production from molasses using a sequence batch reactor (SBR)

This study investigated the effects of various arsenite concentrations on bio-hydrogen production from molasses using a sequence batch reactor (SBR) operated in a series of three batch cycles. In the first batch cycle, hydrogen production was stimulated at arsenite concentrations lower than 2.0 mg/L, while inhibition occurred at arsenite concentration higher than 2.0 mg/L compared to the control. Hydrogen production decreased substantially during the second batch cycle, while no hydrogen was produced during the third batch cycle at all tested concentrations. The toxic density increased with respect to the increase in arsenite concentrations (6.0 > 1.6 > 1.0 > 0.5 mg/L) and operation cycles (third cycle > second cycle > first cycle). The presence of microorganisms such as Clostridium sp. MSTE9, Uncultured Dysgonomonas sp. clone MEC-4, Pseudomonas parafulva FS04, and Uncultured bacterium clone 584CL3e9 resulted in active stimulation of hydrogen production, however, it was unlikely that Enterobacter sp. sed221 was not related to hydrogen production. The tolerance of arsenite in hydrogen producing microorganisms decreased with the increase in induction time, which resulted in severing the inhibition of continuous hydrogen production.

Operational strategies for long-term biohydrogen production from sugarcane stillage in a continuous acidogenic packed-bed reactor

The use of packed-bed reactors for biohydrogen production often results in performance losses in the short term because of the negative effects of operational factors, such as biomass accumulation and inadequate pH conditions. Because packed-bed systems constitute a promising technology for biohydrogen production, studies on continuous hydrogen production over the long term must be carefully conducted by applying proper operational strategies. Therefore, this study assessed continuous biohydrogen production in a packed-bed reactor operated under thermophilic conditions (55 °C) using sugarcane stillage as the substrate. The results indicated that the acidogenic reactor presented a capacity for recovering from performance losses, regardless of their cause, and maintaining continuous hydrogen production rates under long-term operation (240 days). pH proved to be a key factor for obtaining continuous hydrogen production, and the optimal results were observed in a pH range from 5.1 to 5.2. Furthermore, an optimal specific organic loading rate of 6.3–6.4 g carbohydrates g−1 volatile suspended solids d−1 was observed, and this value is consistent with the results of previous studies focused on hydrogen production from fermentative systems.

Effect of Operating Parameters on Process Stability of Continuous Biohydrogen Production from Palm Oil Mill Effluent under Thermophilic Condition

Effect of organic loading rate (OLR), hydraulic retention time (HRT) and temperature variation on process stability of fermentative hydrogen production from palm oil mill effluent (POME) under thermophilic condition was investigated. High OLR (>70 gCOD/l/d) and low HRT (4 d) has significant affected on hydrogen productivity, process stability and microbial community. Hydrogen production at OLR of 55, 60, 65 and 70 gCOD/l/d was 2.4, 3.4, 4.9 and 3.7 L H2/L-POME, respectively. The decreasing in pH and alkalinity and increasing in total VFA could cause the instability of process. The microbial community was changed at OLR >70 gCOD/l/d, HRT 4 d and stop feeding. The dominant microbial community changed from Thermoanaerobacterim sp. to Clostridium sp., Thermoanaerobacterim sp. and Bacillus sp. Hydrogen production at HRT of 2, 4, stop feeding and 2 d was 2.7, 0.8, 0, and 2.6 L H2/L-POME, respectively. Hydrogen production, process stability and microbial community was not affected by variation of temperature. Hydrogen production before and after temperature variation was 2.5 and 2.45 L H2/L-POME.

Controlled continuous bio-hydrogen production using different biogas release strategies.

Dark fermentation for bio-hydrogen (bio-H2) production is an easily operated and environmentally friendly technology. However, low bio-H2 production yield has been reported as its main drawback. Two strategies have been followed in the past to improve this fact: genetic modifications and adjusting the reaction conditions. In this paper, the second one is followed to regulate the bio-H2 release from the reactor. This operating condition alters the metabolic pathways and increased the bio-H2 production twice. Gas release was forced in the continuous culture to study the equilibrium in the mass transfer between the gaseous and liquid phases. This equilibrium depends on the H2, CO2, and volatile fatty acids production. The effect of reducing the bio-H2 partial pressure (bio-H2 pp) to enhance bio-H2 production was evaluated in a 30 L continuous stirred tank reactor. Three bio-H2 release strategies were followed: uncontrolled, intermittent, and constant. In the so called uncontrolled fermentation, without bio-H2 pp control, a bio-H2 molar yield of 1.2 mol/mol glucose was obtained. A sustained low bio-H2 pp of 0.06 atm increased the bio-H2 production rate from 16.1 to 108 mL/L/h with a stable bio-H2 percentage of 55% (v/v) and a molar yield of 1.9 mol/mol glucose. Biogas release enhanced bio-H2 production because lower bio-H2 pp, CO2 concentration, and reduced volatile fatty acids accumulation prevented the associated inhibitions and bio-H2 consumption.

Development of a Novel Hybrid Immobilization Material (HY‐IM) for Fermentative Biohydrogen Production from Beverage Wastewater

AbstractA novel material (hybrid immobilization material, HY‐IM) was developed by the combination of calcium‐alginate, activated carbon (prepared from de‐oiled jatropha waste), wako gel (silica gel) and chitosan for immobilization of hydrogen‐producing bacteria. The stability of the prepared immobilized cells was evaluated by ten repetitive batch experimental runs; the cumulative hydrogen production from beverage wastewater during ten runs was in the range of 2865 to 3300 mL H2/L. The Scanning electron microscopy (SEM) images of the HY‐IM showed bacterial cells entrapment. The hydrogen production performance of the reactor with HY‐IM (1.12 ± 0.04 mol H2/mol hexoseutilized) was comparable to suspended cells reactor (1.07 ± 0.01 mol H2/mol hexoseutilized), and demonstrated repeated usage of same HY‐IM in the reactor with high stability. Experimental evidence suggests that HY‐IM can be applied in continuous biohydrogen production from industrial wastewaters with high efficiency and stability.

Continuous biohydrogen production from starch wastewater via sequential dark-photo fermentation with emphasize on maghemite nanoparticles

Hydrogen production from starch wastewater via sequential dark-photo fermentation process was investigated. Two anaerobic baffled reactors (ABRs) were operated in parallel at an OLR of 8.11±0.97g-COD/L/d, and a HRT of 15h. ABR-1 and ABR-2 was inoculated with pre-treated sludge and sludge immobilized on maghemite nanoparticles, respectively. Better hydrogen yield of 104.75±12.39mL-H2/g-COD-removed was achieved in ABR-2 as compared to 66.22±4.88mL-H2/g-COD-removed in ABR-1. The effluent of ABR-2 was used for further hydrogen production by photo fermentation in ABR-3. An overall hydrogen yield of 166.83±27.79mL-H2/g-COD-removed was achieved at a total HRT of 30h. 16S rRNA phylogeny showed that Clostridium and Rhodopseudomonas palustris species were dominant in ABR-1, ABR-2 and ABR-3, respectively.

Continuous Biohydrogen Production with CSTR Reactor under High Organic Loading Rate Condition

A continuous stirred-tank reactor (CSTR) was used to produce biohydrogen gas from organic wastewater. The hydrogen producing reactor was operated under high organic loading rate of 21 kgCOD/m3·d, and molasses wastewater was used as substrate. Hydrogen production rate, pH value, sugar utilizing rate and fermentative products in effluent were investigated in continuous fermentation. When Organic Loading Rate was controlled at 21 kgCOD/m3·d, the average concentrations of acetic acid, ethanol, propionic acid, butyric acid and valeric acid in liquid fermentative products were 833, 748, 482, 484 and 256mg/L respectively. There is not any fermentation product playing dominant role absolutely in hydrogen production fermentation. The pH value in effluent was about 4.7~4.9, the average utilizing rate of sugar reached 92.1%, most of the sugar in molasses wastewater was utilized. The biogas production rate in hydrogen producing fermentation was from 21.2 to 27.1L/d, and the average biogas production rate was about 25.1L/d. The hydrogen content was about 37%.

Continuous biohydrogen and biomethane production from whey permeate in a two‐stage fermentation process

This study focuses on the exploitation of the two‐stage continuous fermentation process for biohydrogen and biomethane production from whey permeate. Mesophilic fermentative biohydrogen production was investigated at a constant hydraulic retention time (HRT) of 24 h and organic loading rates (OLRs) of 20, 25, 30, and 35 kg COD/m3·d. The hydrogenogenic reactor was successfully operated at OLR of 30 kg COD/m3·d when the proportion of hydrogen in biogas, volumetric productionrsquo rate of hydrogen, and hydrogen yield reached the maximum values of 44.6 ± 0.8%, 5.26 ± 0.15 L H2/d, and 4.19 mol H2/kg CODremoved, respectively. The effluent from hydrogenogenic reactor was further digested to biogas in the second reactor operated at a HRT of 3 d and variable OLR in the range of 0.9–1.9 kg COD/m3·d. Maximum biogas production rate, volumetric production rate of methane and methane yield were 16.90 ± 0.6 L/d, 11.95 ± 0.6 L CH4/d, and 0.12 m3 CH4/kg CODadded. The total chemical oxygen demand elimination from whey permeate reached 98% in a two‐stage process. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 1411–1418, 2014

Evaluation of continuous biohydrogen production from enzymatically treated cornstalk hydrolysate

Enzymatically treated cornstalk hydrolysate was tested as substrate for H2 production by Thermoanaerobacterium thermosaccharolyticum W16 in a continuous stirred tank reactor. The performance of strain W16 to ferment the main components of hydrolysate, mixture of glucose and xylose, in continuous culture was conducted at first, and then T. thermosaccharolyticum W16 was evaluated to ferment fully enzymatically hydrolysed cornstalk to produce H2 in continuous operation mode. At the dilution rate of 0.020 h−1, the H2 yield and production rate reached a maximum of 1.9 mol H2 mol−1 sugars and 8.4 mmol H2 L−1 h−1, respectively, accompanied with the maximum glucose and xylose utilizations of 86.3% and 77.6%. Continuous H2 production from enzymatically treated cornstalk hydrolysate in this research provides a new direction for economic, efficient, and harmless H2 production.

Continuous biohydrogen production from fruit wastewater at low pH conditions

Biohydrogen production from a simulated fruit wastewater (soluble COD = 3.17 ± 0.10 g L⁻¹) was carried out in a continuous stirred tank reactor (CSTR) of 2 L operational volume without biomass inoculation, heat pre-treatment or pH adjustment, resulting in a low operational pH (3.75 ± 0.09). The hydraulic retention time (HRT) varied from 15 to 5 h. A strong negative correlation (p < 0.01) between the biogas production rate and the HRT was observed. Biogas production rates were higher at 30 °C than at 25 °C (p < 0.01), when the CSTR was operated under the same HRT. The biogas hydrogen content was estimated as high as 55.8 ± 2.3 % and 55.4 ± 2.5 % at 25 and 30 °C, respectively. The main fermentation end products were acetic and butyric acids, followed by ethanol. Significant differences (p < 0.01) during the operation of the CSTR at 25 or 30 °C were identified for butyric acid at almost all HRTs examined. Simulation of the acidogenesis process in the CSTR (based on COD and carbon balances) indicated the possible metabolic compounds produced at 25 and 30 °C reactions and provided an adequate fit of the experimental data.

Continuous hydrogen production by immobilized cultures of Thermotoga neapolitana on an acrylic hydrogel with pH-buffering properties

This communication reports on the continuous biohydrogen production by Thermotoga neapolitana cells immobilized on a stable cationic hydrogel bearing amine groups. This hydrogel was designed to perform two functional activities: to promote adhesion of T. neapolitana cells, and to buffer pH changes in the bacterial cultures. Repeated fed-batch cultures showed an average hydrogen production rate and yield of 50.6 mL L−1 h−1 and 3.3 mol H2/mol glucose, respectively. To the best of our knowledge, this is the first report detailing the immobilization of this bacterial strain on a polymeric support.

Continuous biohydrogen production in immobilized biofilm system versus suspended cell culture

In this study, the performance of a new cell immobilization material, namely ceramic ball, was examined for continuous biohydrogen production in comparison to suspended cell culture system (CSTR). Production of biohydrogen in both systems was assessed under thermophilic conditions. Both systems were operated at varying hydraulic retention times (HRT) by shortening HRT values from 24 to 1.5 h at an influent sucrose concentration of 10 g/l. The immobilized bioreactor configuration outcompeted the CSTR bioreactor in terms of both volumetric hydrogen production (2.7 l H2/l/day for immobilized system @ HRT = 3 h and 0.5 l H2/l/day for CSTR @ HRT = 24 h) and resistance to cell-washout (CSTR reactor lost significant amount of biomass at short HRT values). It was concluded that immobilized bioreactor configuration is much more robust than CSTR against high organic loading rates and 5 fold more volumetric hydrogen production was achieved in 8 fold smaller immobilized bioreactor.

Treatability study of using low frequency ultrasonic pretreatment to augment continuous biohydrogen production

Low frequency ultrasonic treatment was investigated to enhance hydrogen production by bacteria under both batch and continuous operation. Optimal ultrasonic time and intensity as examined in batch experiments were found to be 10 s and 100 W, respectively. Hydrogen production was increased by 20% while ultrasonic treatment could effectively shorten batch test reaction times. Using these optimized conditions, continuous experiments were conducted in two parallel expanded granular sludge bed (EGSB) reactors. The ultrasonic treated EGSB reactor obtained a specific hydrogen production rate of 4.38 L/g VSS·d, which was 32% higher than that in the control reactor. Ethanol-type fermentation was achieved at a faster rate and with a 72.7% shorter startup time using ultrasonic treatment. Microbial activity under ultrasonic treatment was shown to resist lower pH and to maintain satisfactory hydrogen production.

Extreme-thermophilic biohydrogen production from lignocellulosic bioethanol distillery wastewater with community analysis of hydrogen-producing microflora

Extreme-thermophilic biohydrogen production from distillery wastewater was investigated in batch and continuous-mode operation. Hydrogen-producing mixed culture was enriched by repeated batch cultivations. Effect of temperature and pH on biohydrogen yield was investigated in batch experiments. The highest hydrogen yield of 196. mL/g-volatile solids addded (VS added) was obtained at 70 °C and pH 7.0 in batch culture. Continuous biohydrogen production was performed in CSTR reactor with yield of 172.0 mL/g-VS added at HRT (hydraulic retention time) of 4 days. The main metabolic products were acetate, lactate, and ethanol. Community structure of hydrogen-producing microflora was investigated by 16S rRNA gene sequence analysis. The microorganisms involved in both batch and continuous-mode operation were similar and hydrogen production was carried out by a group of extreme-thermophilic bacterial species related to Thermotoga, Coprothermobacter, Caldanaerobacter, Thermobrachium, and Caldicellulosiruptor.

Continuous biohydrogen production from diluted molasses in an anaerobic contact reactor

An anaerobic contact reactor (ACR) system comprising a continuous flow stirred tank reactor (CSTR) with settler to decouple the hydraulic retention time (HRT) from solids retention time (SRT) was developed for fermentative hydrogen production from diluted molasses by mixed microbial cultures. The ACR was operated at various volumetric loading rates (VLRs) of 20–44 kgCOD·m−3·d−1 with constant HRT of 6 h under mesophilic conditions of 35°C. The SRT was maintained at about 46–50 h in the system. At the initial VLR of 20 kgCOD·m−3·d−1, the hydrogen production rate dropped from 22.6 to 1.58 L·d−1 as the hydrogen was consumed by the hydrogentrophic methanogen. After increasing the VLR to 28 kgCOD·m−3·d−1 and discharging the sludge for 6 consecutive times, the hydrogentrophic methanogens were eliminated, and the hydrogen content reached 36.4%. As the VLR was increased to 44 kgCOD·m−3·d−1, the hydrogen production rate and hydrogen yield increased to 42.1 L·d−1 and 1.40 mol H2·molglucose-consumed-1, respectively. The results showed that a stable ethanoltype fermentation that favored hydrogen production in the reactor was thus established with the sludge loading rate (SLR) of 2.0–2.5 kgCOD·kgMLVSS−1·d−1. It was found that the ethanol increased more than other liquid fermentation products, and the ethanol/acetic acid (mol/mol) ratio increased from 1.27 to 2.45 when the VLR increased from 28 to 44 kgCOD·m−3·d−1, whereas the hydrogen composition decreased from 40.4% to 36.4%. The results suggested that the anaerobic contact reactor was a promising bioprocess for fermentative hydrogen production.

Effect of pH on continuous biohydrogen production from liquid swine manure with glucose supplement using an anaerobic sequencing batch reactor

pH is considered as one of the most important factors governing the hydrogen fermentation process. In this project, five pH levels, ranging from 4.4 to 5.6 at 0.3 increments, were tested to evaluate the pH effect on hydrogen production from swine manure supplemented with glucose in an anaerobic sequencing batch reactor system with 16 h of hydraulic retention time (HRT). The optimal hydrogen yield (1.50 mol H 2/mol glucose) was achieved at pH 5.0 when the maximum production rate of 2.25 L/d/L was obtained. Continuous hydrogen production was achieved for over 3 weeks for pH 5.0, 4.7, and 4.4, with no significant methane produced. However, as pH increased to 5.3 and 5.6, methane production was observed in the biogas with concurrent reductions in hydrogen production, indicating that methanogens could become increasingly activated for pH 5.3 or higher. Acetate, propionate, butyrate, valerate, and ethanol were the main aqueous products whose distribution was significantly affected by pH as well.

The Effect of pH on Continuous Biohydrogen Production from Swine Wastewater Supplemented with Glucose

The effect of pH on hydrogen production from liquid swine manure supplemented with glucose by a mixed culture of fermentative bacteria in an anaerobic sequencing batch reactor was evaluated in this study. At 37 +/- 1 degrees C, five pH values ranging from 4.7 to 5.9 at an increment of 0.3 were tested at a hydraulic retention time (HRT) of 16 h. The results showed that at this HRT, the optimal pH for hydrogen production was 5.0, under which the biogas comprised 33.57 +/- 5.65% of hydrogen with a production rate of 8.88 +/- 2.94 L-H(2)/day and a yield of 1.48 +/- 0.49 L-H(2)/L liquid swine manure. The highest biomass concentration, highest butyric acid to acetic acid ratio, lowest propionic acid concentration, and the best stability were all found at pH 5.0, while the highest CH(4) productivity was found at pH 5.9. For efficient hydrogen production, oxygen content should be controlled under 2%, beyond which an inverse linear relationship (R(2) = 0.986) was observed.

Critical assessment of anaerobic processes for continuous biohydrogen production from organic wastewater

Production of biohydrogen using dark fermentation has received much attention owing to the fact that hydrogen can be generated from renewable organics including waste materials. The key to successful application of anaerobic fermentation is to uncouple the liquid retention time and the biomass retention time in the reactor system. Various reactor designs based on biomass retention within the reactor system have been developed. This paper presents our research work on bioreactor designs and operation for biohydrogen production. Comparisons between immobilized-cell systems and suspended-cell systems based on biomass growth in the forms of granule, biofilm and flocs were made. Reactor configurations including column- and tank-based reactors were also assessed. Experimental results indicated that formation of granules or biofilms substantially enhanced biomass retention which was found to be proportional to the hydrogen production rate. Rapid hydrogen-producing culture growth and high organic loading rate might limit the application of biofilm biohydrogen production, since excessive growth of fermentative biomass would result in washout of support carrier. It follows that column-based granular sludge process is a preferred choice of process for continuous biohydrogen production from organic wastewater, indicating maximum hydrogen yield of 1.7 mol-H 2/mol-glucose and hydrogen production rate of 6.8 L-H 2/L-reactor h.

Thermophilic biohydrogen production from palm oil mill effluent (POME) using suspended mixed culture

Abstract A batch study was conducted to determine the fate of carbohydrate and oil that are present in palm oil mill effluent (POME) during the biohydrogen fermentation process. Sucrose and crude palm oil (CPO) were chosen as substrates and the kinetic profile indicated that mainly sucrose was metabolised by the mixed sludge. The hydrogen yield based on the COD of sucrose added was 146 cm3 g−1 which is equivalent to a hydrogen to hexose mole ratio of 2.5. The free fatty acids from hydrolysed CPO were not metabolised further which render insignificant generation of hydrogen and volatile fatty acids from oil-based substrate. The average continuous biohydrogen production rate (HPR) from a unit volume of POME under thermophilic condition at 55 °C was 2.64 m3 m−3 d−1 at a hydraulic retention time (HRT) of 4 days. Hydrogen constitutes up to 52% of the total biogas and methane was not detected over the 60 day continuous operation. The hydrogen yield (i.e. based on mole ratio of hydrogen to hexose) was 1.72 with an average carbohydrate conversion efficiency of 58%. These limit the potential of recovering more hydrogen energy from POME under current operating conditions.

Sequencing batch reactor enhances bacterial hydrolysis of starch promoting continuous bio-hydrogen production from starch feedstock

Bio-hydrogen production from starch was carried out using a two-stage process combining thermophillic starch hydrolysis and dark H 2 fermentation. In the first stage, starch was hydrolyzed by Caldimonas taiwanensis On1 using sequencing batch reactor (SBR). In the second stage, Clostridium butyricum CGS2 was used to produce H 2 from hydrolyzed starch via continuous dark hydrogen fermentation. Starch hydrolysis with C. taiwanensis On1 was operated in SBR under pH 7.0 and 55 °C. With a 90% discharge volume, the reducing sugar (RS) production from SBR reactor reached 13.94 g RS/L, while the reducing sugar production rate and starch hydrolysis rate was 0.92 g RS/h/L and 1.86 g starch/h/L, respectively, which are higher than using other discharge volumes. For continuous H 2 production with the starch hydrolysate, the highest H 2 production rate and yield was 0.52 L/h/L and 13.2 mmol H 2/g total sugar, respectively, under a hydraulic retention time (HRT) of 12 h. The best feeding nitrogen source (NH 4HCO 3) concentration was 2.62 g/L, attaining a good H 2 production efficiency along with a low residual ammonia concentration (0.14 g/L), which would be favorable to follow-up photo H 2 fermentation while using dark fermentation effluents as the substrate.