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In this study, the membrane and the adsorption technologies approach are developed and used as a separation technique to separate carbon dioxide (CO 2 ) and hydrogen (H 2 ) gas mixture from biohydrogen dark fermentation. For a real application, the effect of CO 2 impurity in the H 2 fuel (i.e., the gas output from separation techniques) toward the PEM fuel cell performance was studied. Hence, a novel synthesized membrane made of glassy polymers, polyetherimide (PEI) coated bio-cellulose nanofibers and a coconut shell activated carbon (CAC) as adsorbents carriers were used. For the membrane separation technique, the bio-cellulose nanofiber is coated with PEI at varying concentration from 3 to 15 wt.%. The effect of PEI concentrations on the gas permeability and selectivity were observed. Meanwhile, for the adsorption separation technique, the performance of activated carbon was tested by using 0.6 L single column adsorber unit. The characterization of both developed membrane and adsorbent were analyzed including their morphologies and the physical properties. From the results, at 3 wt.% PEI coating, the CO 2 permeability was 16.72 Barrer and corresponding selectivity of CO 2 /H 2 was 0.15. Moreover, the adsorbents carriers showed a better adsorption capacity for CO 2 removal at which 77.17 mg of CO 2 /g of adsorbent in a lower flow rate of feed gas at 0.5 L/min. In the case of PEM fuel cell, the performance would decrease with the increase of CO 2 impurity in H 2 . Therefore, the results presented on this paper are the initial findings generated for the biohydrogen separation technology for the future portable power of PEM fuel cell application. [ABSTRACT FROM AUTHOR]

Concerns about the earth's sustainable management and the reduction of greenhouse gas emissions have become an important issue in the world. One of the alternative solutions is producing biofuels and biomaterial building blocks from biomass waste. Biomass wastes, which include solid waste of agricultural residues (rice straw, wet birch pulp), agro-industrial wastes (mushroom waste, cotton cellulose) and liquid waste of food and related industrial wastewater are abundant feedstock for renewable biohydrogen, biomethane and biochemicals productions etc. This technology of waste to energy and biochemicals includes the pretreatment of biomass, subsequently converted to sugars (hydrolyzate). Sugars are thereafter transformed into biofuels such as hydrogen, methane, ethanol, and the biomaterial building blocks such as volatile fatty acids: Lactic acid, Acetic acid, Propionic acid, and Butyric acid etc. This study proposes an integrated two-stage continuous system to produce biohydrogen and biomethane at higher yields, whilst removing more COD from the wastewater. [ABSTRACT FROM AUTHOR]

The biohydrogen production from rice straw hydrolyzate in a continuously external circulating bioreactor (CECBR) was carried out in this study. The rice straw hydrolyzate was obtained by a concentrated sulphuric acid pretreatment. The original hydrolyzate concentration was 40–50 g total sugar/L. The feeding concentration of hydrolyzate was adjusted to 20 g total sugar/L by tap water. The working volume of CECBR was 300 mL with a height of 22.5 and a width of 7.5 cm respectively. The positions of external circulating ports were 13 and 5 cm high of CECBR with volumetric circulating rate of 9.6 L/min. The average hydrogen production rates (HPR) of 5.52 L/L/d (hydrogen molar yield: 0.72 mol H 2 /mol hexose) and 16.32 L/L/d (hydrogen molar yield: 1.02 mol H 2 /mol hexose) were obtained at hydraulic retention time (HRT) 8 and 4 h respectively. The value of hydrogen production rate at HRT 4 h was three times more than that at HRT 8 h. The presence of bacteria Clostridium favors the hydrogen production from the acetic acid and butyric acid metabolic pathways which were determined by DGGE analysis. The biomass could not be maintained in the CECBR by washing out of the bacteria when the feeding rate was lowered to HRT 2 h. This phenomenon resulted in less hydrogen production and ineffective degradation of hydrolyzate. But the continuously external circulating bioreactor could be steady operated at HRT 4 h with an impressive hydrogen production rate by a rice straw hydrolyzate. [ABSTRACT FROM AUTHOR]

Abstract: The phenomenon of bacterial wash-out frequently occurs in the traditional continuous stirred tank reactor (CSTR) systems at low hydraulic retention time (HRT). In this study, the effect of different aspect ratios, height (H) to diameter (D) of 1:1, 3:1 and 5:1, of a CSTR with immobilized anaerobic sludge on hydrogen (H2) production were investigated. The pH, volatile suspended solids (VSS) and total solids (TS) concentrations of the seed sludge were 6.8, 33.3 and 65.1 g/L, respectively. Thermally treated sludge was immobilized by silicone gel entrapment approach. The entrapped-sludge system operated stably at a low HRT without suffering from cell wash-out. Hence, the hydrogen production rate (HPR) was enhanced by increasing organic loading rates. The immobilized sludge CSTRs were operated at 40 °C with sucrose (10, 20, 30 and 40 g COD/L) and Endo nutrient medium at different HRTs (4, 2, 1 and 0.5 h). It was found that the granule formation enhanced HPR. The maximum HPR and the H2 yield were found to be 15.36H2 L/h/L and 3.16 mol H2/mol sucrose, respectively, with the H2 content in the biogas above 44% for all tests runs. [Copyright &y& Elsevier]

Abstract: The research was carried out using a draft tube fluidized bed bioreactor (DTFBR) system with immobilized cell. The total working volume of the DTFBR including the buffer tank and pipe was 2.4 L. The pH, volatile suspended solid (VSS) and total solid (TS) concentrations of the seed sludge were 6.8, 33.3 and 65.1 g/L, respectively. The thermally treated sludge was used for immobilization. Immobilization of cell was essentially achieved by silicone gel (SC) entrapment approaches. The entrapped-cell system operated stably at a low HRT without any cell washout. Hence, the H2 production rate was enhanced via increasing organic loading rates. The system was fed with sucrose-based synthetic medium, and was examined for its H2 production performance under different influent sucrose concentrations, different solid volume volumetric content and hydraulic retention times. It was found that the optimal solid volume volumetric content was 7.5% (v/v) when the solid volume volumetric contents ranged from 5 to 15% in the DTFBR. The maximum H2 production rate of 2.59 H2 L/h/L with H2 volumetric content of 36.8% and sucrose conversion of 80.5% was obtained at initial substrate concentration of 20 g COD/L, 7.5% (v/v) of solid volume, and HRT 0.5 h. The features of well mixing, high H2-producing performance and stable operation imply that using DTFBR system is a feasible approach to continuous H2 production in reality. [Copyright &y& Elsevier]

Abstract: Hydrogen (H2) has become a promising energy source because it is clean and has high-energy potential. The aim of this research was to enhance the H2 production efficiency under anaerobic condition by addition of calcium ions (Ca2+) in a fluidized bed reactor (FBR) with immobilized cells. Ca2+ ions were added either in the form of Ca(OH)2 or CaCl2. Immobilized cells were prepared by physical adsorption with activated carbon (AC). The experiments were carried out in a FBR system. The H2 production performance of the FBR fed with sucrose-based synthetic medium, was evaluated under various influent Ca2+ concentrations [Ca2+] (50, 100 and 200 ppm) and hydraulic retention times (HRTs) (8, 6, 4 and 2 h). The peak value of 1.22 L/h-L was obtained at [Ca2+] 100 ppm, irrespective of the form of Ca2+ ion added, and at the HRT of 2 h. Although the results were similar for different forms of Ca2+ ions, the presence of Ca2+ ions enhanced the H2 producing bioprocess by 12–18%. [Copyright &y& Elsevier]

Abstract: The lignocellulosic material of mushroom farm waste was used as a feedstock owing to its quantity and availability in Taiwan. In the first stage, the lignocellulosic material of mushroom farm waste was converted into reduced sugars using concentrated sulfuric acid via hydrolysis with a one-step and/or a two-step process. The reduced sugars were then recovered by anion exchange resin. In the second stage, reduced sugars from the first stage were used as substrate to test the potential for biohydrogen production in a batch system. The effects of sulfuric acid concentrations, reaction temperature, particle size, and two-step hydrolysis were investigated at the first pretreatment stage (mushroom farm waste hydrolysis). The reduced sugar concentrations and the initial pH were investigated in the second stage (biohydrogen production). It was found that the maximum yield of reduced sugars in hydrolyzate (reduced sugar per soluble cellulose, wt%) from the first-step (40 °C for 20 min with 55.0% acid) and the second-step (40 °C for 20 min with 6.9% acid) were 74.49% and 96.79%, respectively. In the second stage, the best hydrogen production yield and the hydrogen production rate were 2.52 mol H2/g COD substrate and 4.38 L/L/d, respectively, were obtained initially with a pH 7.0, a temperature of 37 °C and initial reduced sugar concentration of 20 g of COD/L. [Copyright &y& Elsevier]

Abstract: The anaerobic fermentation using the condensed molasses fermentation solubles (CMS) as substrate in a continuously stirred anaerobic bioreactor (CSABR) was carried out for optimal hydrogen production performance of biohydrogen production rate and yield, where as two kinds of bioreactors used. One is a suspended sludge bioreactor (SSB) which used suspended seed sludge. The other bioreactor is an immobilized cell bioreactor (ICB) which used immobilized cells and mix the same seed sludge in the SSB as the source of the bacteria. It was found that the hydrogen production rate increased with a decrease in the hydraulic retention time (HRT), when substrate concentration was 40 g COD/L in an SSB as well as maximum hydrogen production rate of 14.04 ± 2.08 L/d/L obtained at HRT 0.5 h (ca. 5.78 times value of HRT 4 h) in the SSB system. The hydrogen production rate at low dilution rate (HRT > 4 h), in the ICB is better than SSB, meanwhile at a high dilution rate (HRT < 4 h), due to the presence of enriched granules in the SSB (12.30 g VSS/L), absent in the ICB (9.89 g VSS/L), the hydrogen production rate was 7.60 ± 1.05 L/d/L (ca. 1.23 times higher than HRT 4 h), which was lower than the rate in the SSB. Eventually, the hydrogen production rate increased by increasing the substrate concentrations from 40 to 60 g COD/L within the HRT range of 2–4 h in both the SSB as well as in ICB systems. [Copyright &y& Elsevier]

Abstract: A pilot-scale high-rate dark fermentative hydrogen production plant has been established in the campus of Feng Chia University to develop biohydrogen production pilot-plant technology. This pilot-plant system is composed of two feedstock storage tanks (0.75m3 each), a nutrient storage tank (0.75m3), a mixing tank (0.6m3), an agitated granular sludge bed fermentor (working volume 0.4m3), a gas–liquid–solid separator (0.4m3) and a control panel. The seed mixed microflora was obtained from a lab-scale agitated granular sludge bed bioreactor. This pilot-scale fermentor was operated for 67 days at 35°C, an organic loading rate (OLR) of 40–240kg COD/m3/d, and the influent sucrose concentration of 20 and 40kg COD/m3. Both biogas and hydrogen production rates increased with increasing OLR. However, the biomass concentration (volatile suspended solids, VSS) only increased with an increasing OLR at an OLR range of 40–120kg COD/m3/d, whereas it decreased when OLR was too high (i.e., 240kg COD/m3/d). The biogas consisted mainly of H2 and CO2 with a H2 content range of 23.2–37.8%. At an OLR of 240kg COD/m3/d, the hydrogen content in biogas reached its maximum value of 37% with a hydrogen production rate (HPR) of 15.59m3/m3/d and a hydrogen yield of 1.04mol H2/mol sucrose. This HPR value is much higher than 5.26m3/m3/d (fermented molasses substrate) and 1.56m3/m3/d (glucose substrate) reported by other pilot-scale systems. Moreover, HPR was also greatly affected by pH. At an optimal pH of 5.5, the bacterial community became simple, while the efficient hydrogen producer Clostridium pasteurianum was dominant. The factors of energy output compared with the energy input (E f) ranged from 13.65 to 28.68 on biohydrogen, which is higher than the E f value on corn ethanol, biodiesel and sugarcane ethanol but in the similar range of cellulosic ethanol. [Copyright &y& Elsevier]

Abstract: The kinetics of cotton cellulose hydrolysis using concentrated sulfuric acid and the performance of fermentative hydrogen production from the hydrolysate in the batch system was carried out in this study. Effects of sulfuric acid concentrations, cotton cellulose concentrations and operating temperatures on the cotton cellulose hydrolysis were investigated. It was found that cotton cellulose can dissolve completely in sulfuric acid concentration above 55% (by volume) at room temperature. The reduced sugar yields were varied from 64.3 to 73.9% (g R-sugar/g cotton cellulose) with the initial cotton cellulose concentrations of 30–70 g/L at a temperature of 40 °C. The reduced sugar concentrations and the initial pH of biohydrogen production were investigated at 37 °C. It was found that the optimal values of the hydrogen yield and substrate utilization were 0.95 mol H2/mol R-sugar and 98% with an initial pH of 8.2, when substrate concentration was fixed at 20 g R-sugar/L. The maximum hydrogen yield was 0.99 mol H2/mol R-sugar at a substrate concentration of 15 g R-sugar/L. Using the Gompertz Equation Model simulation, the maximum hydrogen production rate was 253 mL H2/h/L at a substrate of 30 g/L and initial pH of 8.4. [Copyright &y& Elsevier]

Abstract: Phase holdups play an important role in high-rate hydrogen production in an anaerobic fermentative reactor, especially in understanding biomass content, biogas flow and distribution that significantly affect the flow regimes change in the reactor. In the present study three-phase hydrogen producing reactor with different configurations were tested to investigate the phase holdups phenomenon and microbial community. It was found that the major fatty acids produced from the reactors were acetate and butyrate (HBu), accounting for 74.4–93.5% of total soluble microbial products (SMP). When the HRT was shortened from 8 to 1 h, the HBu was the dominant acid product among the soluble metabolites and the ratio of Ethanol/SMP was lower than 15.1. Moreover, the gas holdup (ɛg ) and solid holdup (ɛs ) increased but liquid holdup (ɛl ) decreased when the HRT was shortened. When the HRT was down to 1 h an increase in gas and solid holdups were noted. The gas holdups (ɛg ) increased in the range of 0.30–0.34, and the solid holdups (ɛs ) increased in the range of 0.32–0.34, which mean that the values of liquid holdups in high-rate fermentative hydrogen bioreactors could be decreased in the range of 0.38–0.32. Moreover, the empirical correlations of this study were satisfactory to predict the phase holdups in a dark-fermentation biohydrogen system. PCR-DGGE analysis revealed that bioreactor hydrodynamics under different HRTs significantly affects the occurrence of Streptococcus sp. and Bacillus sp. which mainly promotes granulation and retains high yielding hydrogen producing Clostridium sp. through their exopolysaccharides production. SEM results showed three dominant bacterial species namely Clostridium pasteurianum, Streptococcus sp. and Propionibacterium sp. in the bioreactors. [Copyright &y& Elsevier]

Abstract: A high-rate hydrogen production process able to produce H2 at a maximum rate of 15 L/L/h was successfully developed by the Feng Chia University (FCU) biohydrogen research team. This highly efficient hydrogen fermentation system includes a 400 L pilot-scale system constructed for determining scale-up operation parameters for commercializing the bioH2 production technology. The pilot-scale system is composed of a feedstock tank, mixing system, fermentor, gas/liquid separator and automatic control system. The fermentor is fed with sucrose (20 g COD/L) and operated at 35 °C. A batch strategy is used for system start-up. The fermentor was first operated in a batch mode for two days and then switched to a continuous-feeding mode (HRT 12 h) for one month. During the continuous operation, pH notably affected H2 production efficiency and bacterial community. For the first 14-day operation, the H2 production rate increased from 0.017 to 0.256 L/L/h with a pH variation from 5.0 to 7.0. The DGGE results indicate the presence of two Clostridium species (namely, Clostridium butyricum and Clostridium pasteurianum) in the fermenter. Stable hydrogen production rate was obtained at pH 5.5–6.0 when C. pasteurianum became dominant in the mixed culture. [ABSTRACT FROM AUTHOR]

Ethylene–vinyl acetate (EVA) copolymer was used to immobilize H2-producing sewage sludge for H2 production in a three-phase fluidized bed reactor (FBR). The FBR with an immobilized cell packing ratio of 10% (v/v) and a liquid recycle rate of 5l/min (23% bed expansion) was optimal for dark H2 fermentation. The performance of the FBR reactor fed with sucrose-based synthetic medium was examined under various sucrose concentration (C so) and hydraulic retention time (HRT). The best volumetric H2 production rate of 1.80±0.02 H2 l/h/l occurred at C so =40g COD/l and 2h HRT, while the optimal H2 yield (4.26±0.04mol H2/mol sucrose) was obtained at C so =20g COD/l and 6h HRT. The H2 content in the biogas was stably maintained at 40% or above. The primary soluble metabolites were butyric acid and acetic acid, as both products together accounted for 74–83% of total soluble microbial products formed during dark H2 fermentation. [Copyright &y& Elsevier]

Abstract: Fermentative H2 production was operated at different hydraulic retention time using a continuously stirred tank reactor (CSTR) containing suspended H2-producing sludge. The H2 production rate (HPR) increased with a decrease of HRT from 12 to 6h, giving an optimal HPR of 0.6l/h/l at for CSTR operation. However, when the HRT was further shortened to 4h, both HPR and H2 yield decreased significantly. The poor H2-producing performance at 4h HRT is mainly attributed to the marked decrease in biomass content in the reactor due to severe cell washout, as the biomass concentration decreased to a low level of 1.63gVSS/l (volatile suspended solid, VSS). Bioreactor design strategies were applied to improve cell retention under a high substrate feeding rate. Silicone-immobilized cells (immobilized-cell-seeded anaerobic bioreactor (ICSAB system)) or powered activated carbon carriers (AGSB system) were added into the reactor to either maintain stable biomass concentration in the reactor or enhance biomass content by stimulating sludge granulation. Both ICSAB and agitated granular sludge bed (AGSB) showed improvement in biomass retention while operating at a HRT of 4h. In particular, the biomass concentration in AGSB system went up to 10.3VSS/l, leading to a drastic enhancement in H2 producing-performance (0.97l/h/l and 1.54molH2/mol glucose) Bacterial community analysis by denatured gradient gel electrophoresis (DGGE) indicates a transition in bacterial composition in CSTR under different HRT operation. Moreover, under the same HRT (4h) the major bacterial populations in AGSB and ICSAB reactors were very different from those observed in CSTR, indicating that the performance of H2 production seemed to be in close connection with the bacterial community structure. Several Clostridium species known as H2 producers were also detected in the sludge samples by DGGE and 16S rDNA sequence matching, revealing the effectiveness of the H2-producing sludge used in this study. [Copyright &y& Elsevier]

In this work, a dark H2 fermentation process was integrated with a proton-exchange-membrane fuel-cell (PEMFC) system for on-line electricity generation. The H2 producing system was a continuously stirred anaerobic bioreactor (CSABR) seeded with silicone-immobilized sludge. The CSABR system, using sucrose as the sole carbon substrate, was able to continuously and stably produce H2 for over 300 days at a hydraulic retention time (HRT) of 6h and an influent sucrose concentration of 30g COD/l. The maximum H2 production rate and the optimal H2 yield were and sucrose, respectively. The H2 produced from the CSABR system was purified via a CO2 absorber and a silica-gel desiccator, and then the pure H2 was fed into a PEMFC system at a rate of 1.72l/h, generating electricity with a stable electromotive force of . The output power was ca. 0.87W (at ), and the output voltage and current were stably maintained at 2.28V and 0.38A, respectively, when connected to a small light emission diode (LED) panel. [Copyright &y& Elsevier]

Abstract: A draft tube fluidized bed reactor (DTFBR) containing immobilized cell particles was designed to produce H2 continuously. A synthetic polymer (silicone gel; SC) was used as the primary material to immobilize acclimated anaerobic sludge for H2 production in DTFBR with a working volume of 8L. The DTFBR system was operated at a hydraulic retention time (HRT) of 2.2–8.9h and an influent sucrose concentration ( of 5–40g COD/l. The results show that in general decreasing HRT or increasing sucrose concentration led to a marked increase in the volumetric H2 production rate (, but a gradual decrease in the H2 yield (. The best () occurred at COD/l and , whereas the highest ( H2/mol sucrose) was obtained at COD/l and . The correlation between the production rate and the organic loading rate (OLR) can be satisfactorily described by Monod-type models. There was no universal trend of the dependence between the H2 yield and OLR. The H2 content in the biogas was stably maintained at over 40%. The major soluble products were butyric acid and acetic acid, as they accounted for 62–73% and 16–22% of total soluble microbial products (SMPs), respectively. The H2-producing performance in the DTFBR system can be stably maintained and reproducible in long-term operations, while unstable operations can be quickly recovered via proper thermal treatment at 70–80°C. [Copyright &y& Elsevier]

Abstract: A novel synthetic polymer (ethylene-vinyl acetate copolymer; EVA) was used to immobilize acclimated sewage sludge for H2 production under anaerobic conditions. Using sucrose as the sole carbon substrate, the resulting EVA-immobilized cells achieved an optimal H2 production rate () of 488mlH2/gVSS and the best substrate-based yield () of 1.74molH2/mol sucrose. Operation at a temperature of 40°C resulted in the most efficient H2 production. Acclimation of the sewage sludge allowed up to 3-fold enhancement on the performance of H2 production. Kinetic studies show that a Monod-type model is able to describe the dependence of specific H2 production rate on sucrose concentration. The immobilized cells maintained stable and efficient H2 production during 15 repeated runs, indicating excellent durability and stability of the immobilized-cell system. The composition of soluble metabolites was found to be a reliable indicator for the efficiency of biohydrogenation. [Copyright &y& Elsevier]

Compared with plant-derived cellulose, developing biocellulose nanofibers (bio-CNFs) as a functional membrane material is of great interest in membrane filtration for the effective separation of emulsified oily wastewater due to its low cost, renewability, high water-holding capacity and anti-oil-fouling properties. In this work, a bio-CNF membrane was produced by cultured Gluconacetobacter xylinus through a simple biosynthetic process followed by a purification step involving alkali treatment. Herein, the bio-CNF membrane treated with 0.75 M NaOH solution formed a unique, porous nanonetwork structure with good hydrophilicity and ultralow-oil-adhesion properties, and this was successfully applied for the separation of surfactant-stabilized oil/water emulsions. The superhydrophilic and superoleophobic bio-CNF membranes exhibited superior performance for separating surfactant-stabilized oil/water emulsions, showing a separation efficiency of ~99% and a high permeate flux recovery ratio (above 94%) for long-term separation processes. The bio-CNF membrane, which showed good hydrophilicity and a nanonetwork structure, exhibited not only an excellent oil rejection rate but also a high permeate flux recovery ratio. Image 1 • Biocellulose nanofibers (bio-CNFs) as a membrane material for oil-in-water separation. • The bio-CNF membranes possess a nanonetwork structure and are superhydrophilic. • The bio-CNF membranes are well suited for treating the nanoemulsions. • The 0.75 M-treated bio-CNF membrane maintains a uniform structure and properties. • The bio-CNF membranes exhibit good stability for multiple filtration cycles. [ABSTRACT FROM AUTHOR]

With the use of biotechnology, hydrogen can be produced from wastewater rich in short-chain fatty acids. A previous study revealed the ability of Rhodobacter sphaeroides KKU-PS1 to produce biohydrogen from substrates mimicking succinate fermentation effluent. However, the process still requires optimization. Before illumination optimization, due to high concentration of the effluent, various effluent dilution factors ranging from 10 to 100 were compared, and the optimal dilution factor was determined to be 50. Light-emitting diode (LED) setups consisting of bands and tubes were compared, and various illuminated surface-to-volume ratios (S/V) were obtained. LED tubes were subsequently used for light intensity optimization in the range of 5–23 klux, revealing optimum light intensity at 15 klux, yielding 2202 mL H 2 /L and 13.8 mL H 2 /L/h as the cumulative hydrogen and maximum output rate, respectively. The lighting protocol at 15 klux and with a 6h–6h light-dark cycle improved the total light conversion efficiency by up to 3.1%. The study successfully optimized the process, with results rivalling those of a previous study using malate. [Display omitted] • Photofermentation can convert acidic fermentation effluents to hydrogen energy. • Dilution factor of 50 produced H 2 profile that was comparable to higher dilutions. • Cumulative H 2 peaked at 2202 mL H 2 /L at maximum rate of 13.8 mL H 2 /L/h with 15 klux. • Light saturation point was observed at 15–23 klux with similar H 2 productivity. • 6h–6h light-dark cycle achieved the highest light conversion efficiency of 3.1% at 240 h. [ABSTRACT FROM AUTHOR]

The effect of initial pH, metal oxide and concentration of nanoparticles (NP) on hydrogen production were investigated in batch assays using glucose-fed anaerobic mixed bacteria in thermophilic condition of 60 °C. Two type of metal oxide nanoparticles, iron (II) oxide and nickel oxide, were tested and both metal capable of increasing the hydrogen yield about 34.38% and 5.47% higher than the control test. The experiments on the effect of initial pH were done without adding the nanoparticles to determine the optimum pH for maximum hydrogen production, in which at pH 5.5, the maximum hydrogen yield has reached about 1.78 mol H 2 /mol glucose. However, at pH 5.5 and the optimal iron (II) oxide concentration of 50 mg/L, the maximum hydrogen yield has reached to 1.92 mol H 2 /mol glucose, and the hydrogen content was 51%. Furthermore, the analysis of metabolites has indicated that the hydrogen production follows the acetic acid pathway. In all experiments with metal oxide nanoparticles, the metal NP was not consumed by the microbes, and the amount of it at the end of the fermentation was similar to the starting amount, which can be concluded that it was acting as an enhancer to the system to improve the hydrogen production. These results suggest that the addition of iron (II) oxide nanoparticles in the system is the vital factor to enhance the hydrogen production. [ABSTRACT FROM AUTHOR]

The major hurdle to produce bioenergy from rice straw is the low yield of fermentable sugars. This study was carried out to evaluate the effect of pretreatment conditions (rice straw concentration, particle size, hydrolysis time, acid concentration, FeCl 3 and enzyme additions) that can yield the maximum sugar monomers for simultaneous production of hydrogen and ethanol by mixed culture fermentation. The results of the evaluation showed that 0.8–1.0 M hydrochloric acid could give the maximum total sugar yield of 52.9%, 2.8 g/L glucose, 14.5 g/L xylose, and 38.6 g/L total reducing sugar from 100 g/L rice straw with particle size 0.15 mm, hydrolysis time 20 min. FeCl 3 addition did not enhance the sugar yield but enzymatic hydrolysis increased the reducing sugar yield to 49.8 g/L. High volumetric hydrogen production of 771 mL/L and ethanol production of 1776 mg COD/L was obtained from the pretreated rice straw hydrolyzate. And the total energy from simultaneous hydrogen and ethanol production was highest at 355 J/g polysaccharides. [ABSTRACT FROM AUTHOR]

In this study, anaerobic fermentation continuous system was carried out for hydrogen production by low concentration of beverage manufacture process wastewater, the most of the food industry wastewaters are in a relative low sugar concentration. The used substrate concentration of cultivation was 10 g total sugar/L, and hydraulic retention time (HRT) was 1 h for cultivation. Then the substrate concentration of experiments was lowered to 5 g total sugar/L, and HRT 1 h after the cultivation was completed. As a result, hydrogen production rate (HPR) was 11.39 ± 1.39 L/L/d, and yield was 0.30 ± 0.06 mol H 2 /mol hexose at HRT 1 h. The results showed that the hydrogen dark fermentation production in a continuous system is feasible at low concentrations for food industry wastewater. The sustainable biohydrogen production technology not only treat wastewater but also generate electricity from hydrogen via PEMFC. The SO 3 2 − on biohydrogen production, increased with increasing of sulfate concentration can inhibit microbial growth at excess concentration. Sulfate-reducing bacteria (SRB) will cause hydrogen gas converting hydrogen sulfide become poor hydrogen production efficiency. [ABSTRACT FROM AUTHOR]

The biohydrogen production is promising for the alternative green hydrogen. The two-stage of the dark and photo-fermentation system increases the hydrogen production yield. In this study, the experiments carried out the cell immobilizations on dark and photo bacteria; and liquid suspended photo bacteria for those two-stage batch systems. The optimized parameters obtained, such as materials for immobilized cells, different substrates, and the substrate concentrations for hydrogen fermentation. The experiment results showed pure substrate glucose could produce a higher amount of hydrogen in the photo immobilized cells, the hydrogen concentration was up to about 40%, the utilization rate of glucose was as high as 99.41%, the accumulated hydrogen volume was 169.13 mL, and the hydrogen yield, HY, was 0.63 mol H 2 /mol glucose. In addition, the activated immobilized cells are used for two-stage fermentation to generate hydrogen, HY 1.75 mol H 2 /mol substrate. The two-stage batch fermentations for producing hydrogen, used the Gompertz equation model to obtain the cumulative hydrogen volume and hydrogen production rate (HPR). When the ratio of dark immobilized cells (DIMC) to photo suspended liquids (PSL) is 1.0:5.0, the hydrogen production shows well performance. Moreover, an advanced molecular biological technique, next-generation sequencing (NGS) with ultra-high-throughput DNA output, was applied to perform microbial communities in a different stage of hydrogen fermentation. The NGS help to understand the detailed microbial community change in such fermentation processes and provide better biological efficacy via clarifying the role of microorganisms and their interactions. After the experiments, the Clostridia increased to 28%, and the Enterobacter also increased to 15%, therefore the Rhodobacter and Bosea were reduced from 55% to 17%. Understand the detailed composition of microbial populations in stages of such bio-system will provide the useful information via clarify the biological role of microorganisms and its interactions. [Display omitted] • The study successfully made the immobilized cells of photosynthetic bacteria in batch reactors. • Photo-immobilized cells obtained the best hydrogen production of 169.13 mL H 2 /100 mL. • The microbial community of photo-immobilized cells changed significantly before and after the experiments. • The next-generation sequencing technique provides the relations of microbial and H 2 production. • Immobilized cells applied to two-stage of dark/photo H 2 productions obtained good outcomes. [ABSTRACT FROM AUTHOR]

Abstract: Conifer and birch pulp fermentation to hydrogen and methane was studied using dry and wet pulps with a compost enrichment culture at a pH range from 6 to 9. Hydrogen was produced at each pH, whilst methane was produced at all other pH values except pH 6 with dry conifer pulp and pH 9. Hydrogen and methane yields were generally higher with birch than with conifer pulp and the overall energy yields were higher with wet than dry pulp. The highest hydrogen and methane yields were 560mL H2/g TS with wet birch pulp at pH 6 and 4800mL CH4/g TS with wet conifer pulp at pH 7, respectively. Fermentation of dry pulps at pH 6 resulted in 160mL H2/g TS. Hydrogenic bacteria belonging to phyla Bacteroidetes, Firmicutes and Proteobacteria were present in the cultures. Hydrogen was also produced from chemically hydrolyzed pulps. The highest hydrogen yield from dry conifer pulp hydrolysate was 63mLH2/g TS. In summary, hydrogen and energy (calculated as H2) yields were higher with direct fermentation than from chemically hydrolyzed pulps. However, chemical hydrolysis followed by hydrogen production required less than 10days compared to 28days required for direct pulp fermentation to hydrogen. [Copyright &y& Elsevier]

Abstract: In this study, grass silage was used both as a source of bacteria and as a substrate for dark fermentative hydrogen production. Silage is produced by lactic acid fermentation controlled by end point pH (<4.0). In this study, the fermentation of silage was successfully continued and directed to hydrogen production by neutralizing the pH. Highest hydrogen yield of 37.8 ± 5.8 mL H2/g silage was obtained at 25 g/L of silage. The main soluble metabolites were acetate and butyrate with the final concentrations of 1.5 ± 0.2 and 0.5 ± 0.0 g/L, respectively. Bacteria present (at 25 g silage/L) included Ruminobacillus xylanolyticum, Acetanaerobacterium elongatum and Clostridium populeti and were involved in silage fermentation to hydrogen. In summary, this work demonstrates that grass silage becomes amenable to hydrogen fermentation by indigenous silage bacteria through pH neutralization. [Copyright &y& Elsevier]

Abstract: In this study, the yield of hydrogen production was investigated under different feedstock pretreatment conditions. The feedstock for dark fermentative hydrogen production was textile wastewater which was obtained from the de-sizing process in a textile factory, located in northern Taiwan. The wastewater was pretreated with activated carbon, cation exchange resin or was not pretreated before being fed into the batch bottles. Biohydrogen production was carried out in a batch reactor with the sludge of mixed-culture using the feedstock from the pretreated wastewater. The sludge was obtained from the Taichung municipal wastewater treatment plant. The yield of hydrogen production using the two pretreatment methods or non – treatment were compared. Results showed that the textile wastewater could remove bio-toxic inhibitors by using activated carbon. The best hydrogen yield was 1.37 mol H2/mol reducing sugar with an initial pH 7.0, as substrate concentration was fixed at 20 g total sugar/L. Using textile wastewater as feedstock for biohydrogen production was successful, in removing bio-toxic inhibitors from wastewater with activated carbon pretreatment. [Copyright &y& Elsevier]

Photofermentation seems to be an attractive mode of generating biohydrogen from fermentation effluent. Use of succinate fermentation effluent, however, has not been reported. Rhodobacter sphaeroides KKU-PS1 and Rhodopseudomonas palustris were acclimatised in succinate. It was determined that the KKU-PS1 was superior with respect to hydrogen productivity and was selected for further experiments. Photofermentation in succinate by the KKU-PS1 validated, generating 1217 mL H 2 /L of cumulative hydrogen at a maximum rate of 6.7 mL H 2 /L/h. Photofermentation from each single carbon sources that are components of effluent was performed and it was determined that acetate and succinate promoted the fastest growth of KKU-PS1 and hydrogen evolution, respectively. Photofermentation by the strain using mixed substrates mimicking diluted bio-succinate effluent produced yielded 1005 mL H 2 /L cumulative hydrogen at a maximum rate of 4.1 mL H 2 /L/h. The study highlighted potential of utilizing bio-succinate fermentation effluent for biohydrogen production, with further optimization required. Image 1 • R. sphaeroides KKU-PS1 yielded 0.9–1.2 L H 2 /L, more than 2-fold H 2 by R. palustris. • KKU-PS1 biomass peaked at around 1 g/L, indicating better growth than R. palustris. • KKU-PS1 yielded 1.2 L H 2 /L from succinate, which was comparable to malate. • KKU-PS1 generated 1.0 L H 2 /L from mixed substrates based on bio-succinate effluent. • Sugar metabolism sustained H 2 production by KKU-PS1 during stationary growth phase. [ABSTRACT FROM AUTHOR]

Photo-fermentation seems to be an attractive hydrogen production pathway. However, the light conversion efficiency and photo-hydrogen production of purple non-sulphur bacteria (PNSB) are very low, and hence, various biotechnological approaches are investigated to improve biohydrogen production. This article presents an overview of the advanced biotechnological approaches to enhance the photo-fermentative biohydrogen production. The advancements reviewed include optimisation of the medium, abiotic factors, the lighting regime, immobilisation techniques, application of photoluminating nanomaterials, genetic engineering, and other strategies. These approaches show positive results in the enhancement of photo-hydrogen production by PNSB. Some recommendations are suggested for further studies in the enhancement of photo-hydrogen production, such as green nanomaterials application, integrated dark- and photo-fermentation, genetic manipulation, and the application of the non-technological analysis approaches. • Various biotechnological approaches applied on photo-fermentation are reviewed. • H 2 yield improved by optimisation on medium, abiotic factors and lighting regime. • Novel photoluminating nanomaterials is promising to increase H 2 yield. • Additional H 2 enhancement strategies are recommended for further research. [ABSTRACT FROM AUTHOR]

Abstract Palm oil mill effluent (POME), an agro-industrial wastewater with high solids content, was subject to hydrolysis by 1% (w/v) nitric acid in order to increase its solubility and the fermentable sugar content from its cellulosic component. POME hydrolysate was then evaluated in an up-flow anaerobic sludge blanket (UASB) bioreactor for the production of biohydrogen gas via mixed culture under thermophilic conditions. The bioreactor was fed with pre-treated POME under varied hydraulic retention time (HRT) between 48 and 3 h at constant cycle length of 24 h to test the productivity of H 2 and the stability of UASB; no washout of biomass occurred at any cycle and the system managed to recover its H 2 production rate (HPR) after initial fluctuations. In this study, H 2 -producing granules (HPGs) were formed shortly after the start-up period, and were analysed by FESEM, FTIR, SEM-EDX, and their extracellular polymeric substances (EPS) content. The maximum HY and HPR achieved were 2.45 mol-H 2 /mol-sugar and 11.75 L H2 /L POME d−1, respectively, at HRT 6 h. Acetic acid was found to be the major by-product at all HRTs, followed by butyric acid, while Clostridium spp. was found to be the most dominant H 2 -producing bacteria in the system. Results suggest that UASB has a good potential for stable H 2 production with high POME digestion rate. Graphical abstract Image Highlights • Raw POME was pre-treated using dilute nitric acid. • H 2 -producing granules from POME were produced in UASB. • Optimum biohydrogen yield achieved was 2.45 mol H2 /mol sugar. • Bacterial community in H 2 producing sludge was dominated by Clostridium spp. [ABSTRACT FROM AUTHOR]

[Display omitted] • Light spectra vary the biomass and bio-H 2 production via photo-fermentation process. • Red light spectrum is more beneficial for bacterial growth and biomass accumulation. • Green light spectrum has the largest effect on photo-fermentative bio-H 2 production. • LCE under green light illumination is 2-folds of that under control white light. • Bacteriochlorophyll and carotenoid absorb red and green light in photo-fermentation. Purple non-sulphur bacteria can only capture up to 10 % light spectra and only 1–5 % of light is converted efficiently for biohydrogen production. To enhance light capture and conversion efficiencies, it is necessary to understand the impact of various light spectra on light harvesting pigments. During photo-fermentation, Rhodobacter sphaeroides KKU-PS1 cultivated at 30 °C and 150 rpm under different light spectra has been investigated. Results revealed that red light is more beneficial for biomass accumulation, whereas green light showed the greatest impact on photo-fermentative biohydrogen production. Light conversion efficiency by green light is 2-folds of that under control white light, hence photo-hydrogen productivity is ranked as green > red > orange > violet > blue > yellow. These experimental data demonstrated that green and red lights are essential for photo-hydrogen and biomass productions of R. sphaeroides and a clearer understanding that possibly pave the way for further photosynthetic enhancement research. [ABSTRACT FROM AUTHOR]

Abstract Major sugar constituents in young coconut husk were found to be glucans (0.30 g/g husk), while xylans were 0.10 g/g husk. Pre-treatments were carried out using phosphoric acid with dried coconut husk powder under steam heating. The effect of phosphoric acid on coconut husk hydrolysis was observed using acid concentrations of 0%, 1%, 5% and 10% (v/v). Soluble sugar concentration in hydrolysate was increasing proportional to acid concentration, as the total recovered solid decreases. FTIR and XRD analysis showed that acid hydrolysis led to the disruption of internal chemical bonds, causing coconut husk structural sugars to be released into the hydrolysate. Highest soluble sugar concentration, 29.9 g/L with a total suspended solid of 75.1 g/L, was obtained when the coconut husk was pre-treated with 10% phosphoric acid, and can be utilised for biohydrogen fermentation. Biotoxicity testing of the hydrolysates shows that half-maximal inhibition concentration of phosphoric acid was around 4.41% for a 24-h incubation and 3.80% for a 96-h incubation. Graphical abstract Image 1 Highlights • Coconut husk sugar yield increases 18.3 g/L for 0% H 3 PO 4 to 29.9 g/L for 10% H 3 PO 4. • Biohydrogen yield of 0.68 mol H 2 /mol sugar is obtained with 1% H 3 PO 4 hydrolysate. • The half-maximal inhibition concentration of H 3 PO 4 is 4.41% for 24-h incubation. • The decrease order of biotoxicity is 10% H 3 PO 4 > 5% H 3 PO 4 > 1% H 3 PO 4 > 0% H 3 PO 4. [ABSTRACT FROM AUTHOR]

The excessive burning of fossil fuels is one of the main sources of emissions of carbon dioxide (CO 2 ) which causes the greenhouse effect. The effect could be resulted in climate changes and disorder of our ecosystem. Thus, bioenergy developments will play important roles to help decreasing CO 2 emission for better global environment in the future. In the domain of biohydrogen production, biomass including: cellulose, wastewater and agricultural waste are the main resources to maintain feedstock demand. Developing sustainable energy with sustainable feedstock sources like sugary wastewater by using two-stage biomass-derived gas production system might bring great economic profits to business. In this study, the system will be chosen to testify its sustainability when producing the sugary wastewater to renewable source energy. The commercial potential analysis is derived from the internal rate of return (IRR). The novelty finding of this study, as the result showed, found out that the energy recovery is 1.12 times higher than single stage. According to the IRR analysis with the calculated years of 15 years, the IRR is 32.47% that means the system can payback within 3.19 years. Therefore, the feasibility of commercialization potential of biomass-derived gas production system can be verified. [ABSTRACT FROM AUTHOR]

Abstract: Nowadays, the design of waste treatment needs to be environmentally-friendly. Due to the fact that the concern of global warming is getting critical, the reuse of waste treatment can be beneficial in reducing carbon dioxide emission. Microbial electrolysis cell (MEC) is a device that can reduce the organic materials and produce the green energy, biohydrogen. Therefore, MEC provides an alternative path for waste degradation. In this study, MEC was analyzed with TRIZ that aims to eliminate contradiction matrix from the analysis in order to improve the MEC efficiency. The study approach is based on the following steps: classifying patents and paper, determining engineering parameters; solving the contradictory problems with 40 innovative principles, and finding the solutions. The results were verified by the currently researches. [Copyright &y& Elsevier]

Acid treated rice straw hydrolysate was used as a substrate hydrogen production. Concentrated sulphuric acid (55%) was used to completely dissolve the rice straw cellulose at temperature of 40 °C. After hydrolysis of rice straw cellulose, calcium hydroxide was used to remove sulphate ions. Biohydrogen production was evaluated under different initial pH and substrate concentration conditions at a temperature of 37 °C in a batch mode. The maximum values of hydrogen yield and accumulation of hydrogen were 0.44 mol H2/mol T-sugar and 97.30 ± 0.17 mL with substrate utilization of 81.55% in a batch mode. A mixture of food industry wastewater with rice straw hydrolysate was used as substrate in a continuous mode for the biohydrogen production potential test in this study. The average hydrogen production yield of 0.69 mol H2/mol T-sugar was 1.5 times higher than that in the batch mode while the hydrogen production rate was 10 ± 1.17 L/d/L. The presence of bacteria Clostridium pasteurianum which favours the production of hydrogen from of acetic acid and butyric acid was determined by DGGE. [ABSTRACT FROM AUTHOR]

Abstract: The world is facing serious climate change caused in part by human consumption of fossil fuel. Therefore, developing a clean and environmentally friendly energy resource is necessary given the depletion of fossil fuels, the preservation of the earth''s ecosystem and self-preservation of human life. Biological hydrogen production, using dark fermentation is being developed as a promising alternative and renewable energy source, using biomass feedstock. In this study, beverage wastewater and agricultural waste were examined as substrates for dark fermentation to produce clean biohydrogen energy. A reference model including all major process steps was computed using the Aspen Plus software program and model valuations were based on the data obtained in our lab and/or a pilot scale process unit. A beverage company in northern Taipei was the source of wastewater used in the production of biological hydrogen, whereby the use of our hydrogen producing system resulted in a maximum annual profit with an annual return rate of approximately 81% with a working volume of 100 m3 from wastewater and 30% with a working volume of 400 m3 from agricultural waste using local price evaluation and approximately 60% with working volume of 200 m3 from wastewater and 39% with working volume of 300 m3 from agricultural waste. The optimal sizes of the commercial biohydrogen fermenters of wastewater and agriculture waste were 52.51 and 300.57 m3, respectively which were simulated by local price. These results were derived from the Aspen Plus simulation, proving it''s economic feasibility. [Copyright &y& Elsevier]

Abstract: The present study developed a low-CO methanol processor for the online supply of hydrogen to a proton exchange membrane fuel cell (PEMFC) composed of a steam reformer, a catalytic combustor and a reactor for the removal of CO. Commercial Cu/ZnO/Al2O3- and Pt/Al2O3-based catalysts were used in the methanol steam reforming and the preferential oxidation (PROX) reactor, respectively. The steam reformer was successfully heated with a catalytic combustor at room temperature without any additional electrical power supply. Hydrogen gas was obtained at a flow rate of 43.0Lh−1 using a feed flow rate of 39.5mlh−1 (S/C=1.1) and an operation temperature of 250°C, corresponding to a power output of 59We. The CO concentration could be maintained at 4–5ppm for stable operation. [Copyright &y& Elsevier]

Abstract: The Bed Pressure Fluctuation Analysis (PFA) and dual electrical resistivity probe methods were used to investigate the hydrodynamic properties in a bioreactor. It was found that the dominant frequency and side frequency signals were not obvious from Hydraulic Retention Time (HRT) 4 to 0.5 h on the power spectrum diagram when using condensed molasses fermentation soluble (CMS) as the substrate in a biohydrogen production reactor. The start-up testing and online monitoring of the bed pressure fluctuation in a pilot system with HRT 12 h was also investigated. The pressure fluctuation analysis method established a hydrodynamic behavior diagram that was effective in determining flow regime of biogas in large-scale bioreactors. Finally, the study found that a mathematical model built using MATLAB to calculate and simulate the dynamic behavior of bubbles in a biological hydrogen production reactor satisfactorily. The bubble rise velocity and bubble size increased from 0.7 to 1.5 cm/s and 0.2 to 1.9 × 10−6 cm respectively when the biogas production rate was increased from 30 to 70 mL/min in the biohydrogen production reactor. [Copyright &y& Elsevier]

Abstract: Our recent work showed the feasibility of using a 400 L pilot-scale bioreactor for hydrogen production via dark fermentation. However, the H2 production performance of the pilot system was unsatisfactory when compared with that of lab-scale fermentors under the same conditions. This study applied engineering approaches to enhance the hydrogen production performance of the pilot bioreactor. First, a higher agitation rate was used to promote mass transfer efficiency. Next, the pilot system was operated under different combinations of hydraulic retention time (HRT) and substrate concentration (CS) that gives different sets of organic loading rate (OLR) to improve bioH2 production efficiency. With 25–30 rpm agitation rate and a OLR of 60 g COD/L/d (from combination of 8 h HRT and 20 g COD/L CS), the H2 production rate (HPR) of the pilot system reached 0.55 mol/L/d (13.4 m3/m3/d), which is 3.1 fold of that obtained from using a lower agitate rate (10–15 rpm). When operating at HRT = 6 h and C S = 30 g COD/L (i.e., OLR = 120 g COD/L/d), the pilot system obtained the highest HPR, hydrogen yield and overall hydrogen production efficiency of 1.18 mol/L/d, 3.84 mol H2/mol sucrose and 47.2%, respectively. This performance is similar to that obtained from the lab-scale system and is significantly higher than that from the original pilot tests prior to process optimization. [Copyright &y& Elsevier]

Abstract: The need of developing renewable energy to reduce the impact on the global environment and climate change of the increasing industrial development has fostered the use of biological processes to produce biofuel from biohydrogen. The present work made a patent analysis of advanced hydrogen production techniques comparing it with similar prior art in China, Japan, the Republic of Korea, the European Union and the United States (U.S.) The aims were to find the scope, competitiveness of prior art, as well as the technology trend on biohydrogen production methods. The patents value was assessed its geographic scope and competitiveness indicators such as green image, low cost, energy efficiency and equipment design. It was found that most of the hydrogen production methods and associated technologies are developed by academic institutions, however their patents are reduced to a local level, and few are patented at international level, which reduces their competitiveness. The China (P.R.C.) is the biggest patent contributor worldwide in terms of hydrogen production methods by academic institutions. Japan is a huge patent contributor, in terms of methods aiming rear-end products application of hydrogen by private companies. The biggest amount of prior art found that the most popular methods of pre-treatment and dark fermentation produced coincide with the time of energetic crisis and the green movement to find alternative fuels. Finally, patent analysis of this study can help to discern the current technology trend and to develop the next generation of biohydrogen processes and associated technologies. [Copyright &y& Elsevier]