Continuous hydrogen production from cofermentation of sugarcane vinasse and cheese whey in a thermophilic anaerobic fluidized bed reactor

The co-fermentation of vinasse and cheese whey (CW) was evaluated in this study by using two thermophilic (55° C) anaerobic fluidized bed reactors (AFBRs). In AFBR using vinasse and CW (AFBR-V-CW), the CW was added in increasing proportions (2, 4, 6, 8, and 10 g COD.L^?1) to vinasse (10 g COD.L^?1) to assess the advantage of adding CW to vinasse. By decreasing the hydraulic retention time (HRT) from 8 h to 1 h in AFBR-V, maximum hydrogen yield (HY), production rate (HPR), and H₂ content (H₂%) of 1.01 ± 0.06 mmol H₂.g COD^?1, 2.54 ± 0.39 L H₂.d^?1.L^?1, and 47.3 ± 2.9%, respectively, were observed at an HRT of 6 h. The increase in CW concentration to values over 2 g COD.L^?1 in AFBR-V-CW decreased the HY, PVH, and H₂%, with observed maximum values of 0.82 ± 0.07 mmol H₂.g COD^?1, 1.41 ± 0.24 L H₂.d^?1.L^?1, and 55.5 ± 3.7%, respectively, at an HRT of 8 h. The comparison of AFBR-V-CW and AFBR-V showed that the co-fermentation of vinasse with 2 g COD.L^?1 of CW increased the HPR, H₂%, and HY by 117%, 68%, and 82%, respectively.     

Effect of hydraulic retention time on a continuous biohydrogen production in a packed bed biofilm reactor with recirculation flow of the liquid phase

The present paper reports on results obtained from experiments carried out in a laboratory-scale anaerobic packed bed biofilm reactor (APBR), with recirculation of the liquid phase, for continuously biohydrogen production via dark fermentation. The reactor was filled with Kaldnes^® biofilm carrier and inoculated with an anaerobic mesophilic sludge from a urban wastewater treatment plant (WWTP). The APBR was operated at a temperature of 37 °C, without pH buffering. The effect of theoretical hydraulic retention time (HRT) from 1 to 5 h on hydrogen yield (HY), hydrogen production rate (HPR), substrate conversion and metabolic pathways was investigated. This study indicates the possibility of enhancing hydrogen production by using APBR with recirculation flow. Among respondents values of HRT the highest average values of HY (2.35 mol H₂/mol substrate) and HPR (0.085 L h^?1L^?1) have been obtained at HRT equal to 2 h.     

Biohydrogen production in anaerobic fluidized bed reactors: Effect of support material and hydraulic retention time

This study evaluated two different support materials (polystyrene and expanded clay) for biohydrogen production in an anaerobic fluidized bed reactor (AFBR) treating synthetic wastewater containing glucose (4000 mg L⁻¹). The AFBRs contained either polystyrene (R1) or expanded clay (R2) as support materials were inoculated with thermally pre-treated anaerobic sludge and operated at a temperature of 30 °C and a pH of approximately 5.5. The AFBRs were operated with a range of hydraulic retention times (HRTs) between 1 and 8 h. For R1 with an HRT of 2 h, the maximum hydrogen yield (HY) was 1.90 mol H₂ mol⁻¹ glucose, with 0.805 mg of biomass (as total volatile solids, or TVS) attached to each g of polystyrene. For R2 operated at an HRT of 2 h, the maximum HY was 2.59 mol H₂ mol⁻¹ glucose, with 1.100 mg of attached biomass (as TVS) g⁻¹ expanded clay. The highest hydrogen production rates (HPR) were 0.95 and 1.21 L h⁻¹ L⁻¹ for R1 and R2, respectively, using an HRT of 1 h. The H₂ content increased from 16–47% for R1 and from 22–51% for R2. No methane was detected in the biogas produced throughout the period of AFBR operation. These results show that the values of HY, HPR, H₂ content, and g of attached biomass g⁻¹ support material were all higher for AFBRs containing expanded clay than for reactors containing polystyrene.     

Fermentative hydrogen production from starch using natural mixed cultures

Batch and continuous tests were conducted to evaluate fermentative hydrogen production from starch (at a concentration of chemical oxygen demand (COD) 20 g/L) at 35 °C by a natural mixed culture of paper mill wastewater treatment sludge. The optimal initial cultivation pH (tested range 5–7) and substrate concentration (tested range 5–60-gCOD/L) were evaluated by batch reactors while the effects of hydraulic retention time (HRT) on hydrogen production, as expressed by hydrogen yield (HY) and hydrogen production rate (HPR), were evaluated by continuous tests. The experimental results indicate that the initial cultivation pH markedly affected HY, maximum HPR, liquid fermentation product concentration and distribution, butyrate/acetate concentration ratio and metabolic pathway. The optimal initial cultivation pH was 5.5 with peak values of HY 1.1 mol-H₂/mol-hexose maximum HPR 10.4 mmol-H₂/L/h and butyrate concentration 7700 mg-COD/L. In continuous hydrogen fermentation, the optimal HRT was 4 h with peak HY of 1.5 mol-H₂/mol-hexose, peak HPR of 450 mmol-H₂/L/d and lowest butyrate concentration of 3000 mg-COD/L. The HPR obtained was 280% higher than reported values. A shift in dominant hydrogen-producing microbial population along with HRT variation was observed with Clostridium butyricum, C. pasteurianum, Klebshilla pneumoniae, Streptococcus sp., and Pseudomonas sp. being present at efficient hydrogen production at the HRTs of 4–6 h. Strategies based on the experimental results for optimal hydrogen production from starch are proposed.     

Synergistic effects and optimization of photo-fermentative hydrogen production of Rhodobacter sphaeroides DSM 158

The synergistic effects and optimization of pH, carbon-to-nitrogen ratio (C/N), and light intensity (I) on the photo-fermentative hydrogen production of Rhodobacter sphaeroides 158 DSM and light conversion efficiency have been investigated under different conditions of pH (6.5–8); C/N (15–35); and light intensity (35–185 W m^?2). Response surface methodology (RSM) and Box-Behnken experimental design (BBD) were used to identify the optimum values of the three key parameters of pH, C/N, and I, based on the impact on hydrogen production potential (HPP), hydrogen production rate (HPR), and light conversion efficiency $\eta$. With desirability value of 0.91, the optimum values of 7.4, 27.5, and 126 W m^?2 were identified for pH, C/N, and I respectively, with HPP, HPR and $\eta$ reaching 960 mL L^?1, 41.74 mL L^?1 h^?1, and 0.31 respectively. Regression analysis indicated a good fit between experimental and model data. The study showed that both C/N ratio and I have crucial and significant effect on the HPP, HPR and $\eta$, followed by pH, the synergistic effect of pH–I and C/NI on the light conversion efficiency ($\eta$) was significant while pH C/N was insignificant. The results and analysis obtained could be very useful for better optimizing the photo-fermentative hydrogen production.     

Thermophilic versus mesophilic dark fermentation in xylose-fed fluidised bed reactors: Biohydrogen production and active microbial community

Dark fermentative biohydrogen production in a thermophilic, xylose-fed (50 mM) fluidised bed reactor (FBR) was evaluated in the temperature range 55–70 °C with 5-degree increments and compared with a mesophilic FBR operated constantly at 37 °C. A significantly higher (p = 0.05) H₂ yield was obtained in the thermophilic FBR, which stabilised at about 1.2 mol H₂ mol^?1 xylose (36% of the theoretical maximum) at 55 and 70 °C, and at 0.8 mol H₂ mol^?1 xylose at 60 and 65 °C, compared to the mesophilic FBR (0.5 mol H₂ mol^?1 xylose). High-throughput sequencing of the reverse-transcribed 16S rRNA, done for the first time on biohydrogen producing reactors, indicated that Thermoanaerobacterium was the prevalent active microorganism in the thermophilic FBR, regardless of the operating temperature. The active microbial community in the mesophilic FBR was mainly composed of Clostridium and Ruminiclostridium at 37 °C. Thermophilic dark fermentation was shown to be suitable for treatment of high temperature, xylose-containing wastewaters, as it resulted in a higher energy output compared to the mesophilic counterpart.     

Producing hydrogen from the fermentation of cheese whey and glycerol as cosubstrates in an anaerobic fluidized bed reactor

This study aimed to evaluate the effect of the organic loading rate (OLR) (60, 90, and 120 g Chemical Oxygen Demand (COD). L^?1. d^?1) on hydrogen production from cheese whey and glycerol fermentation as cosubstrates (50% cheese whey and 50% glycerol on a COD basis) in a thermophilic fluidized bed reactor (55 °C). The increase in the OLR to 90 gCOD.L^?1. d^?1 favored the hydrogen production rate (HPR) (3.9 L H₂. L^?1. d^?1) and hydrogen yield (HY) (1.7 mmol H₂. gCOD^?1_app) concomitant with the production of butyric and acetic acids. Employing 16S rRNA gene sequencing, the highest hydrogen production was related to the detection of Thermoanaerobacterium (34.9%), Pseudomonas (14.5%), and Clostridium (4.7%). Conversely, at 120 gCOD.L^?1. d^?1, HPR and HY decreased to 2.5 L H₂. L^?1. d^?1 and 0.8 mmol H₂. gCOD^?1_app, respectively, due to lactic acid production that was related to the genera Thermoanaerobacterium (50.91%) and Tumebacillus (23.56%). Cofermentation favored hydrogen production at higher OLRs than cheese whey single fermentation.     

Biohydrogen production from crude glycerol by immobilized Klebsiella sp. TR17 in a UASB reactor and bacterial quantification under non-sterile conditions

Biohydrogen production from crude glycerol by immobilized Klebsiella sp. TR17 was investigated in an up-flow anaerobic sludge blanket (UASB) reactor. The reactor was operated under non-sterile conditions at 40^○C and initial pH 8.0 at different hydraulic retention times (HRTs) (2–12 h) and glycerol concentrations (10–30 g/L). Decreasing the HRT led to an increase in hydrogen production rate (HPR) and hydrogen yield (HY). The highest HPR of 242.15 mmol H₂/L/d and HY of 44.27 mmol H₂/g glycerol consumed were achieved at 4 h HRT and glycerol concentrations of 30 and 10 g/L, respectively. The main soluble metabolite was 1,3-propanediol, which implies that Klebsiella sp. was dominant among other microorganisms. Fluorescence in situ hybridization (FISH) revealed that the microbial community was dominated by Klebsiella sp. with 56.96, 59.45, and 63.47% of total DAPI binding cells, at glycerol concentrations of 10, 20, and 30 g/L, respectively.     

Evaluation of semi-continuous hydrogen production from enzymatic hydrolysates of Agave tequilana bagasse: Insight into the enzymatic cocktail effect over the co-production of methane

This work addresses the hydrogen production from enzymatic hydrolysates of Agave tequilana bagasse and the valorization of the acidogenic effluent for methane production in anaerobic sequencing batch reactors (ASBRs). Regarding hydrogen production, the ASBR was operated at four organic loading rates (OLRs), which were modified by decreasing the cycle time (from 24 to 12 h) and increasing the COD concentration (from 8 to 12 and 16 g L^?1). Results showed that the highest OLR promoted the highest hydrogen production rate of 25.2 ± 2.1 NmL L^?1 h^?1. Conversely, the hydrogen molar yield remained constant, obtaining similar values to the highest reported for lignocellulosic hydrolysates in continuous reactors (1.6H₂-mol mol_{consumed sugar}^?1). Regarding methane production from the acidogenic effluent, an unexpected methane suppression was observed during the first 5 cycles of the ASBR operation. Such event was attributed to the disaggregation of the granular sludge due to the remaining hydrolytic activity of the enzymatic cocktail used for the hydrolysates production. This was corroborated by feeding acetate to an ASBR (positive control) and supplying the enzymatic cocktail. Overall, even though the ASBR configuration demonstrated its suitability for hydrogen production, further studies are needed to coupling the methanogenic phase in different reactor configurations.     

Synergistic effect of TiF3@ graphene on the hydrogen storage properties of Mg–Al alloy

Mg–Al alloy was prepared by sintering and mechanical alloying, and the effects of graphene (Gp), TiF₃ and Gp/titanium (III) fluoride (TiF₃) on the hydrogen storage properties of the Mg–Al alloy were studied. The results show that Gp and TiF₃ could improve the hydrogen storage properties of Mg–Al alloy. In particular, Gp and TiF₃ showed good synergistic effect for enhancing the hydrogen storage properties of Mg–Al alloy. For example, when 1.0 wt% of H₂ was absorbed/desorbed, the hydrogen adsorption/desorption temperature of the Mg–Al alloy and Mg–Al-M (M = Gp, TiF₃, and TiF₃@Gp) composites were 241/343 °C, 185/310 °C, 229/292 °C and 159/280 °C, respectively. For the Mg–Al alloy, the apparent activation energy was 176.5 kJ mol^?1, and it decreased to 139.8 kJ mol^?1, 171.6 kJ mol^?1, and 94.3 kJ mol^?1, with the addition of Gp, TiF₃ and TiF₃@Gp composites, respectively. Evidently, the comprehensive hydrogen storage properties of Mg–Al alloy were improved remarkably under the synergistic effect of Gp and TiF₃.     

Dual-tuning the thermodynamics and kinetics: Magnesium-naphthalocyanine nanocomposite for low temperature hydrogen cycling

2,11,20,29-Tetra-tert-butyl-2,3-naphthalocyanine (TTBNc) was used as an alternative host to support magnesium (Mg) nanoparticles. After deposition and decomposition of dibutylmagnesium on TTBNc, Mg nanoparticles of around 4 nm supported on TTBNc were observed by TEM. These TTBNc stabilized Mg nanoparticles were found to absorb hydrogen at 100 °C and release hydrogen from 75 °C. The Mg-TTBNc material showed good hydrogen cycling properties and structural stability. Kinetic measurements showed fast hydrogen absorption within 2 min at 150 °C. The hydrogen desorption kinetics were slower at the same temperature but faster at 250 °C with 80% of the hydrogen desorbed within 1 h. Enthalpy and entropy for hydrogen uptake and release in Mg-TTBNc determined from PCT measurements were found to be of 52.7 ± 4.9 kJ mol^?1 H₂ and 107.8 ± 9.4 J K^?1 mol^?1 H_2, respectively. These values are much lower than those of bulk Mg.     

Catalytic effects of V and V2O5 on hydrogen storage property of Mg17Al12 alloy

A Mg₁₇Al₁₂ alloy was synthesized via sintering, and the catalytic effects of V and V₂O₅ on the hydrogen (H₂)-storage properties of this alloy were investigated. The results revealed that the hydrogenation/dehydrogenation temperature of Mg₁₇Al₁₂ decreased markedly and the reversible hydrogen storage properties improved with the addition of V or V₂O₅. For example, at 250 °C, the Mg₁₇Al₁₂ alloy underwent hydrogenation only and a hydrogen absorption capacity of 2.22 wt.% was realized. However, with the addition of V and V₂O₅, (i) reversible hydrogen absorption/desorption occurred, (ii) the hydrogen absorption capacity increased to 2.95 wt.% and 3.35 wt.%, and (iii) the hydrogenation/dehydrogenation enthalpy of the Mg₁₇Al₁₂alloy decreased from 65.7/83.1 kJ·mol^?1 to 62.6/69.3 kJ·mol^?1 and 59.9/68.1 kJ·mol^?1, respectively.     

Single-stage photo-fermentative hydrogen production from hydrolyzed straw biomass using Rhodobacter sphaeroides

The hydrogen production utilizing photosynthetic and anaerobic bacteria in two-stage approach has many drawbacks, such as shortage of raw materials and complexity of operations. Accordingly, we aimed to develop a simple one-stage H₂ production protocol using the depolymerization of maize straw cellulose as a cheap carbon source. R. sphaeroides HY01 and its mutant (Hup^?) were studied regarding their H₂ production under different culture conditions. Further study using two model sugars, their combination, and straw hydrolysate as carbon sources was conducted to determine the effects of substrate on H₂ production. When using the straw hydrolysate as carbon source, the pH remained in a range of 7.1–7.6, whereas it dropped to 5.4–7.4 when using the model sugars, and the former biomass value was greater. The H₂ production performance of the mutant was significantly better than that of HY01. One-step photo-fermentative H₂ production was superior when using straw hydrolysate as opposed to the simple model sugars, and its yield was up to 4.62 mol H₂·mol^?1 reducing sugar.     

Superior hydrogen generation from sodium borohydride hydrolysis catalyzed by the bimetallic Co–Ru/C nanocomposite

Sodium borohydride has been widely regarded as a promising hydrogen carrier owing to its greatly hydrogen storing capability (10.8 wt%), high weight density and excellent stability in alkaline solutions. Herein, we first design and synthesize a series of bimetallic M-Ru/C nanocomposites (including Fe–Ru/C, Co–Ru/C, Ni–Ru/C and Cu–Ru/C), via simply alloying of commercial Ru/C with nonprecious metal, for superior H₂ evolution from the NaBH₄ hydrolysis. The result exhibits that H₂ generation is synergetically improved by alloying Ru/C with Co or Ni, while it is hindered by alloying Ru/C with Fe or Cu. Indeed, Co–Ru/C presents the highest efficient catalytic activity for H₂ generation, with the TOF of 117.69 mol(H₂)·mol_Ru^?1·min^?1, whereas Ru/C is only 57.08 mol(H₂)·mol_Ru^?1·min^?1. In addition, the TOF of Co–Ru/C reaches to 436.51 mol(H₂)·mol_Ru^?1·min^?1 (96.7 L(H₂)·g_Ru^?1·min^?1) in the presence of NaOH.     

Investigation on structure and hydrogen storage performance of as-milled and cast Mg90Al10 alloys

The as-milled (20 h) and cast Mg₉₀Al₁₀ alloys were prepared by mechanical milling and vacuum induction melting, respectively. The differences in the phase composition, apparent morphology and microstructure of the alloys were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM) and high resolution transmission microscope (HRTEM). The activation performance, hydrogen absorption/desorption rate and pressure-composition-isotherm (P-C-T) curves of the pure Mg, as-milled (20 h) and cast Mg₉₀Al₁₀ alloys were tested using a Sieverts apparatus. The results show that the alloys both are nanocrystalline structure and consisted of the main phase of Mg phase and the second phase of Al phase or Mg₁₇Al₁₂ phase. Compared to pure Mg, the thermodynamics and kinetics of the as-milled (20 h) and cast Mg₉₀Al₁₀ alloys are improved in different degree. The hydrogen desorption enthalpy (ΔH_de) of the as-milled (20 h) and cast Mg₉₀Al₁₀ alloys are 75.43 and 72.76 kJ mol^?1 H₂, which are smaller than 100.67 kJ mol^?1 H₂ of pure Mg. And the dehydrogenation activation energy (E^de(a)) decreases from 172.61 kJ mol^?1 H₂ of pure Mg to 163.59 and 157.65 kJ mol^?1 H₂ of the as-milled (20 h) and cast Mg₉₀Al₁₀ alloys, respectively. However, the activation performance and the hydrogen absorption capacity have the varying degree to drop.     

Production and stability of low amount fraction of formaldehyde in hydrogen gas standards

Formaldehyde is an intermediate of the steam methane reforming process for hydrogen production. According to International Standard ISO 14687-2 the amount fraction level of formaldehyde present in hydrogen supplied to fuel cell electric vehicles (FCEV) must not exceed 10 nmol mol^?1. The development of formaldehyde standards in hydrogen is crucial to validate the analytical results and ensure measurement reliability for the FCEV industry. NPL demonstrated that these standards can be gravimetrically prepared and validated at 10 μmol mol^?1 with a shelf-life of 8 weeks (stability uncertainty <10%; k = 1), but that formaldehyde degrades into methanol and dimethoxymethane, as measured by FTIR, GC-MS and SIFT-MS. The degradation kinetics is more rapid than predicted by thermodynamics, this may be due to the internal gas cylinder surface acting as a catalyst. The identification of by-products (methanol and dimethoxymethane) requires further investigation to establish any potential undesirable impacts to the FCEV.     

Continuous biogenic hydrogen production from dilute acid pretreated algal hydrolysate using hybrid immobilized mixed consortia

This study investigated the bioconversion of dilute acid (2% H₂SO₄) pretreated red algae (Gelidium amansii) hydrolysate into H₂ by anaerobic fermentation in a continuous stirred tank reactor under mesophilic conditions using hybrid immobilized cells as microbial catalyst. Two different hydraulic retention times (HRT) of 24 h and 16 h with a feed concentration of 15 g/L hexose equivalent have been investigated over 85 days of operation to evaluate H₂ production performance and stability of the continuous system. The highest hydrogen production rate (HPR) and hydrogen yield (HY) of 2.7 L/L/d and 1.3 mol/mol substrate hexose_added was achieved at 24 h HRT, while further operation at 16 h HRT led to a significant drop in the hydrogen production with a HPR and HY values of 1.8 L/L/d and 0.7 mol/mol substrate hexose_added, respectively. The bacterial community analysis characterized by 454 pyrosequencing revealed that the changes in HRT significantly influence the composition of the dominant microflora. At longer HRT (24 h), the phyla Firmicutes was abundant over 98%, whereas at shorter HRT (16 h), Proteobacteria being the dominant populations with 84%. These outcomes suggested that controlling appropriate HRT is prerequisite for efficient hydrogen production.     

Temperature-hydrogen pressure phase boundaries and corresponding thermodynamics for ZrCoH system

The thermodynamically and kinetically stable regions of the temperature–H₂ pressure phase boundaries for the ZrCoH system were established using the Temperature-Concentration-Isobar (TCI) method. Based on this, the enthalpy change and entropy change values of dehydrogenation and disproportionation reactions were successfully obtained. The average enthalpy change (ΔH) and entropy change (ΔS) estimated from the phase boundaries for dehydrogenation of ZrCoH₃ to ZrCo are respectively 103.07 kJ mol^?1H₂ and 148.85 J mol^?1 H₂ K^?1, which are well agreement with the data reported in literature. The average ΔH and ΔS were estimated to be ?120.91 kJ mol^?1H₂ and -149.32 J mol^?1 H₂ K^?1 for the disproportionation of ZrCoH₃, whereas the ΔH and ΔS were calculated to be ?84.6 kJ mol^?1H₂ and -92.29 J mol^?1 H₂ K^?1 for disproportionation of ZrCo. In addition, it was found from the established phase boundaries that the anti-disproportionation property of ZrCo alloy can be enhanced if the phase boundaries of hydrogenation/dehydrogenation are far away from the phase boundaries of disproportionation by adjusting the thermodynamics. Meanwhile, it is possible to keep ZrCo away from disproportionation even at high temperature of 650 °C under hydrogen atmosphere, if the temperature-H₂ pressure trajectory is carefully controlled without crossing the phase boundaries of disproportionation. Therefore, the established phase boundaries can be used as a guide to the eye avoiding disproportionation and improving the anti-disproportionation property of ZrCo alloy.     

Assessment of the adequacy of different Mediterranean waste biomass types for fermentative hydrogen production and the particular advantage of carob (Ceratonia siliqua L.) pulp

The conversion of agro-industrial byproducts, residues and microalgae, which are representative or adapted to the Mediterranean climate, to hydrogen (H₂) by C. butyricum was compared. Five biomass types were selected: brewery’s spent grain (BSG), corn cobs (CC), carob pulp (CP), Spirogyra sp. (SP) and wheat straw (WS). The biomasses were delignified and/or saccharified, except for CP which was simply submitted to aqueous extraction, to obtain fermentable solutions with 56.2–168.4 g total sugars L^?1. In small-scale comparative assays, the H₂ production from SP, WS, CC, BSG and CP reached 37.3, 82.6, 126.5, 175.7 and 215.8 mL (g biomass)^?1, respectively. The best fermentable substrate (CP) was tested in a pH-controlled batch fermentation. The H₂ production rate was 204 mL (L h)^?1 and a cumulative value of 3.9 L H₂ L^?1 was achieved, corresponding to a H₂ production yield of 70.0 mL (g biomass)^?1 or 1.6 mol (mol of glucose equivalents)^?1_. The experimental data were used to foresight a potential energy generation of 2.4 GWh per year in Portugal, from the use of CP as substrate for H₂ production.     

Biological hydrogen production from sugar beet molasses by agar immobilized R. capsulatus in a panel photobioreactor

Biohydrogen production from sugar beet molasses was investigated by using agar immobilized R. capsulatus YO3. A panel photobioreactor (1.4 L) was employed for a long-term hydrogen production in both indoor and outdoor conditions. The impact of several initial molasses concentrations on hydrogen production, yield and productivity were assessed. Indoor studies revealed that initial sucrose concentration in molasses should be kept below 20 mM to prevent inhibition of hydrogen production. The highest hydrogen productivity of 0.64 ± 0.06 mmol H₂ L^?1 h^?1 and yield of 12.2 ± 1.5 mol H₂/mol sucrose were obtained in indoors throughout 20 days of operation. For outdoors, hydrogen production continued for 40 days including consecutive 10 rounds under natural outdoor conditions. In outdoor conditions, the maximum hydrogen productivity and yield were 0.79 ± 0.04 mmol H₂ L^?1 h^?1 and 5.2 ± 0.4 mol H₂/mol sucrose respectively. These results indicate that the proposed system is promising for biohydrogen production from molasses at large-scale natural conditions.