Biological hydrogen production from phenol-containing wastewater using Clostridium butyricum

Toxicity renders certain industrial effluents unfit for recovering its bioenergy content. An enriched single strain, Clostridium butyricum, was herein applied to fermentatively produce hydrogen from glucose in the presence of 200–1500 mg L⁻¹ of phenol. The enriched C. butyricum yielded hydrogen at approximately 1.4 mol H₂ mol⁻¹ glucose in the presence of 200–400 mg L⁻¹ phenol. Significant inhibition of cell metabolism was noted at phenol concentration >1000 mg L⁻¹. During glucose fermentation, phenol dosed at 200–400 mg L⁻¹ was partly co-degraded. Ethanol and acetate were the primary metabolites, whose yields increased with increasing phenol concentration. The present results revealed the potential to harvest hydrogen from a toxic (phenol-containing) wastewater.     

Oxygen- and hydrogen-permeation measurements on-mixed conducting SrFeCo0.5Oy ceramic membrane material

The SrFeCo_0.5O_y system combines high electronic/ionic conductivity with appreciable oxygen permeability at elevated temperatures. This system has potential use in high-temperature electrochemical applications such as solid oxide fuel cells, batteries, sensors, and oxygen separation membranes. Dense ceramic membranes of SrFeCo_0.5O_y are prepared by pressing a ceramic powder prepared by using a sol–gel combustion technique. Oxygen and hydrogen permeation at high temperature on this material are studied. Measurements are conducted using a time-dependent permeation method at the temperature in the range of 1073–1273 K with oxygen- and hydrogen-driving pressures in the range (3×10²)–(1×10⁵) Pa (300–1000 mbar). The maximum oxygen-permeated flux at 1273 K is 6.5×10⁻³ mol m⁻² s⁻¹. The activation energies for the O₂-permeation fluxes and diffusivities are 240 and 194 kJ/mol, respectively. Due to the high fragility, the high temperature for the measurements and the high oxygen permeation through such material, a special membrane holder, and compression sealing system have been designed and realized for the permeation apparatus.     

Imidazolium-based ionic liquid derivatives for application in electrochromic devices

Novel proton-conducting electrolytes were prepared from the sol–gel precursor 1-[3-(trimethoxy-λ⁴-silyl)propyl]imidazole with the addition of either trifluoroacetic or acetic acid. The presence of trimethoxysilyl groups enabled the solvolysis and condensation reactions of silsesquioxane species. IR spectroscopy revealed that more cube-like species formed in the electrolyte prepared from trifluoroacetic acid, while cube- and ladder-like silsesquioxanes were present in the electrolyte with acetic acid. This assignation was independently confirmed by ²⁹Si NMR analyses revealing the T³ signals of trisiloxane bonding. IR spectroscopy also pointed to the formation of hydrogen bonding in the latter electrolyte, since the frequencies of the observed bands at 1710, 1409, and 1272 cm⁻¹ approached those of acetic acid. In contrast, the IR bands at 1662, 1204, and 1130 cm⁻¹ confirmed the existence of trifluoroacetate anions in the case when the electrolyte was prepared from trifluoroacetic acid. The presence of free trifluoroacetate anions contributed to the moderately higher specific conductivity of this electrolyte (4.6×10⁻⁵ S/cm) compared to that of acetic acid (1.6×10⁻⁵ S/cm). The specific conductivity of the electrolytes could be further increased by the addition of a lithium salt. All electrolytes were employed in electrochromic devices with optically active WO₃ and various inorganic counter-electrodes (CeVO₄, V₂O₅, Ti/V-oxide). Photopic transmittance changes from 30% to 40% were achieved.     

Fermentative hydrogen production by two novel strains of Enterobacter aerogenes HGN-2 and HT 34 isolated from sea buried crude oil pipelines

Present study investigated fermentative hydrogen production of two novel isolates of Enterobacter aerogenes HGN-2 and HT 34 isolated from oil water mixtures. The two isolates were identified as novel strains of E. aerogenes based on 16S rRNA gene. The batch fermentations of two strains from glucose and xylose were carried out using economical culture medium under various conditions such as temperature, initial pH, NaCl, Ni⁺/Fe⁺⁺, substrate concentrations for enhanced fermentation process. Both the strains favoured wide range of pH (6.5–8.0) at 37 °C for optimum production (2.20–2.23 mol H₂/mol-glucose), which occurred through acetate/butyrate pathway. At 55 °C, both strains favoured 6.0–6.5 and acetate type fermentation was predominant in HT 34. Hydrogen production by HT 34 from xylose was highly pH dependant and optimum production was at pH 6.5 (circa 1.98 mol-H₂/mol-xylose) through acetate pathway. The efficiency of the strain HGN-2 at pH 6.5 was 1.92–1.94 mol-H₂/mol-xylose, and displayed both acetate and butyrate pathways. At 55 °C, very low hydrogen production was detected (less than 0.5 m mol/mol-xylose).     

CaBr2 hydrolysis for HBr production using a direct sparging contactor

The calcium–bromine cycle being investigated is a novel continuous hybrid cycle for hydrogen production employing both heat and electricity. Calcium bromide (CaBr₂) hydrolysis generates hydrogen bromide (HBr) which is electrolyzed to produce hydrogen. The CaBr₂ hydrolysis at 1050 K (777 °C) is endothermic with the heat of reaction δG_T = 181.5 KJ/mol (43.38 kcal/mol) and the Gibbs free energy change is positive at 99.6 kJ/mol (23.81 kcal/mol). What makes this hydrolysis reaction attractive is both its rate and that well over half the thermodynamic requirements for water-splitting heat of reaction of δG_T = 285.8 KJ/mol (68.32 kcal/mol) are supplied at this stage using heat rather than electricity. Molten-phase calcium bromide reactors may overcome the technical barriers associated with earlier hydrolysis approaches using supported solid-phase calcium bromide studied in the Japanese UT-3 cycle. Before constructing the experiment two design concepts were evaluated using COMSOL™ multi-physics models; 1) the first involved sparging steam into a calcium-bromide melt, while 2) the second considered a “spray-dryer” contactor spraying molten calcium bromide counter-currently to upward-flowing steam. A recent paper describes this work [6]. These studies indicated that sparging steam into a calcium-bromide melt is more feasible than spraying molten calcium bromide droplets into steam. Hence, an experimental sparging hydrolysis reactor using a mullite tube (ID 70 mm) was constructed capable of holding 0.3–0.5 kg (1.5–2.5 × 10⁻³ kg mol) CaBr₂ forming a melt with a maximum 0.08 m (8 cm) depth. Sparging steam at a steam rate of 0.02 mol/mol of CaBr₂ per minute (1.2–2.3 × 10⁻⁵ kg/s), into this molten bath promptly yielded HBr in a stable operation that converted up to 25% of the calcium bromide. The kinetic constant derived from the experimental data was 2.17 × 10⁻¹² kmol s⁻¹ m⁻² MPa⁻¹ for the hydrolysis reaction. The conversion rate is highly dependent on melt depth and the design for steam sparging. This experimental data provides a basis for designing a larger-scale sparging hydrolysis reactor for the calcium bromide thermochemical cycle where the endothermic heat of reaction can be effectively supplied by heat transfer coils embedded in the melt.     

Pulsed laser deposition of W–V–O composite films: Preparation, characterization and gasochromic studies

Modified tungsten oxide films by vanadium oxide provide neutrally coloring electrochromic electrodes for smart windows technology. In this study W–V–O mixed oxide films were fabricated by Nd:YAG pulsed laser deposition (PLD), λ=1064 nm, from mixed pressed powders of (WO₃)_1−x(V₂O₅)_x, x=0, 0.09, 0.17, 0.23, 0.29 and 0.33, at 13.3 Pa oxygen partial pressure and 200 °C temperature on glass substrates. X-ray photoelectron spectroscopy (XPS) revealed V⁵⁺, V⁴⁺, W⁶⁺ and W⁵⁺ surface oxide states, where the ratio of W⁵⁺/W⁶⁺ enhances by the amount of vanadium in the films. Surface morphology was studied by scanning electron microscope (SEM) and optical properties by transmission-reflection spectra. Results showed that films with a low amount of vanadium oxide have better porosity and higher optical band gaps. The gasochromic response to hydrogen gas exposure was found better for x=0.09 in the sense of both deeper and faster coloring. Weak responses of samples with more vanadium oxide were attributed to higher amounts of W⁵⁺ in the films and also to lower porosity.     

Optical and electrical properties of semiconducting WS2 thin films: From macroscopic to local probe measurements

Photosensitive WS₂ thin films are obtained by annealing in presence of a crystallization promoter like Ni or Co. Conventional optical and electrical measurements (conductivity, Hall effect, photoconductivity) are completed by various local probe investigations like scanning tunneling microscopy (STM) and conductive atomic force microscopy (AFM). This thorough study clarifies the respective role of the crystallites and the grain boundaries in the macroscopic measurements and gives information on the properties and on the photovoltaic prospect of the films. The optical properties of the thin films are comparable to those of WS₂ single crystals, with absorption excitonic peaks of same intensity at 1.94 and 2.36 eV. The films show a p-type behavior with a carrier concentration of p10²³ m⁻³ and a Hall mobility of μ_H10×10⁻⁴ m² V⁻¹ s⁻¹ at room temperature. The Hall mobility is thermally activated with an activation energy of 60–90 meV. The photoconductivity spectra show the first indirect transition at 1.35 eV and a decrease of the quantum efficiency at the excitonic-transitions energies. The transport in the film plane is mainly governed by the potential barriers at the grain boundaries. Using a conducting AFM, the crystallite edges are shown to be degenerate semiconductors, while STM current–voltage (I–V) spectroscopy indicates that the flat WS₂ crystallites have a low density of surface states on the basal planes. Submicron solid-state junctions are fabricated on the film by depositing gold electrodes on single WS₂ crystallites (with an electrode surface of 0.2 μm²). Under illumination the p-WS₂/Au micro-junctions show open circuit-voltages of up to 520 mV. The collection of photo-generated carriers is limited by recombination at the grain boundaries.     

p-doped μc-Si:H window layers prepared by hot-wire CVD for amorphous solar cell application

We report on boron-doped μc-Si:H films prepared by hot-wire chemical vapor deposition (HWCVD) using silane as a source gas and trimethylboron (TMB) as a dopant gas and their incorporation into all-HW amorphous silicon solar cells. The dark conductivity of these films was in the range of 1–10 (Ω cm)⁻¹. The open circuit voltage V_oc of the solar cells was found to decrease from 840 mV at low hydrogen dilution H-dil=91% to 770 mV at high H-dil =97% during p-layer deposition which can be attributed to the increased crystallinity at higher H-dil and to subsequent band edge discontinuity between μc-Si:H p- and amorphous i-layer. The short circuit current density J_sc and the fill factor FF show an optimum at an intermediate H-dil and decrease for the highest H-dil. To improve the conversion efficiency and the reproducibility of the solar cells, an amorphous-like seed layer was incorporated between TCO and the bulk p-layer. The results obtained until now for amorphous solar cells with and without the seed layer are presented. The I–V parameters for the best p–i–n solar cell obtained so far are J_sc=13.95 mA/cm², V_oc=834 mV, FF=65% and η=7.6%, where the p-layers were prepared with 2% TMB. High open circuit voltages up to 847 mV could be achieved at higher TMB concentrations.     

La0.84Sr0.16MnO3−δ cathodes impregnated with Bi1.4Er0.6O3 for intermediate-temperature solid oxide fuel cells

La_0.84Sr_0.16MnO_3−δ–Bi_1.4Er_0.6O₃ (LSM–ESB) composite cathodes are fabricated by impregnating LSM electronic conducting matrix with the ion-conducting ESB for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The performance of LSM–ESB cathodes is investigated at temperatures below 750 °C by AC impedance spectroscopy. The ion-impregnation of ESB significantly enhances the electrocatalytic activity of the LSM electrodes for the oxygen reduction reactions, and the ion-impregnated LSM–ESB composite cathodes show excellent performance. At 750 °C, the value of the cathode polarization resistance (R_p) is only 0.11 Ω cm² for an ion-impregnated LSM–ESB cathode, which also shows high stability during a period of 200 h. For the performance testing of single cells, the maximum power density is 0.74 W cm⁻² at 700 °C for a cell with the LSM–ESB cathode. The results demonstrate the ion-impregnated LSM–ESB is one of the promising cathode materials for intermediate-temperature solid oxide fuel cells.     

Characterization of Pr1−xSrxCo0.8Fe0.2O3−δ (0.2 ≤ x ≤ 0.6) cathode materials for intermediate-temperature solid oxide fuel cells

Cathode materials consisting of Pr_1−xSr_xCo_0.8Fe_0.2O_3−δ (x = 0.2–0.6) were prepared by the sol–gel process for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The samples had an orthorhombic perovskite structure. The electrical conductivities were all higher than 279 S cm⁻¹. The highest conductivity, 1040 S cm⁻¹, was found at 300 °C for the composition x = 0.4. Symmetrical cathodes made of Pr_0.6Sr_0.4Co_0.8Fe_0.2O_3−δ (PSCF)–Ce_0.85Gd_0.15O_1.925 (50:50 by weight) composite powders were screen-printed on GDC electrolyte pellets. The area specific resistance value for the PSCF–GDC cathode was as low as 0.046 Ω cm² at 800 °C. The maximum power densities of a cell using the PSCF–GDC cathode were 520 mW cm⁻², 435 mW cm⁻² and 303 mW cm⁻² at 800 °C, 750 °C and 700 °C, respectively.     

Improved cyclability by tungsten addition in electrochromic NiO thin films

Aiming at improving the electrochromic properties of NiO thin films, well-known as anodic counter electrodes, the effect of tungsten addition was investigated. Ni–W–O thin films were deposited by pulsed laser deposition in optimized conditions, namely a 10⁻¹ mbar oxygen pressure and a room temperature substrate. The presence of W led to a progressive film amorphization. An increase in cyclability for Ni–W–O (5%_t WO₃) electrode, cycled in KOH 1 M electrolyte, was associated with a limited dissolution of the oxidized phases with tungsten addition. HRTEM investigations of cycled films revealed that the stabilization is correlated to the existence of an α(II) hydroxide phase.     

Investigation of pulsed non-melt laser annealing on the film properties and performance of Cu(In,Ga)Se2 solar cells

Pulsed non-melt laser annealing (NLA) has been used for the first time to modify near-surface defects and related junction properties in Cu(In,Ga)Se₂ (CIGS) solar cells. CIGS films deposited on Mo/glass substrates were annealed using a 25 ns pulsed 248 nm laser beam at selected laser energy density in the range 20–60 mJ/cm² and pulse number in the range 5–20 pulses. XRD peak narrowing and SEM surface feature size increase suggest near-surface structure changes. Dual-beam optical modulation (DBOM) and Hall-effect measurements indicate NLA treatment increases the effective carrier lifetime and mobility along with the sheet resistance. In addition, several annealed CdS/CIGS films processed by NLA were fabricated into solar cells and characterized by photo- and dark-J–V and quantum efficiency (QE) measurements. The results show significant improvement in the overall cell performance when compared to unannealed cells. The results suggest that an optimal NLA energy density and pulse number for a 25 ns pulse width are approximately 30 mJ/cm² and 5 pulses, respectively. The NLA results reveal that overall cell efficiency of a cell processed from an unannealed film increased from 7.69% to 13.41% and 12.22% after annealing 2 different samples at the best condition prior to device processing.     

Optimization and microbial community analysis for production of biohydrogen from palm oil mill effluent by thermophilic fermentative process

The optimum values of hydraulic retention time (HRT) and organic loading rate (OLR) of an anaerobic sequencing batch reactor (ASBR) for biohydrogen production from palm oil mill effluent (POME) under thermophilic conditions (60 °C) were investigated in order to achieve the maximum process stability. Microbial community structure dynamics in the ASBR was studied by denaturing gradient gel electrophoresis (DGGE) aiming at improved insight into the hydrogen fermentation microorganisms. The optimum values of 2-d HRT with an OLR of 60 gCOD l⁻¹ d⁻¹ gave a maximum hydrogen yield of 0.27 l H₂ g COD⁻¹ with a volumetric hydrogen production rate of 9.1 l H₂ l⁻¹ d⁻¹ (16.9 mmol l⁻¹ h⁻¹). The hydrogen content, total carbohydrate consumption, COD (chemical oxygen demand) removal and suspended solids removal were 55 ± 3.5%, 92 ± 3%, 57 ± 2.5% and 78 ± 2%, respectively. Acetic acid and butyric acid were the major soluble end-products. The microbial community structure was strongly dependent on the HRT and OLR. DGGE profiling illustrated that Thermoanaerobacterium spp., such as Thermoanaerobacterium thermosaccharolyticum and Thermoanaerobacterium bryantii, were dominant and probably played an important role in hydrogen production under the optimum conditions. The shift in the microbial community from a dominance of T. thermosaccharolyticum to a community where also Caloramator proteoclasticus constituted a major component occurred at suboptimal HRT (1 d) and OLR (80 gCOD l⁻¹ d⁻¹) conditions. The results showed that the hydrogen production performance was closely correlated with the bacterial community structure. This is the first report of a successful ASBR operation achieving a high hydrogen production rate from real wastewater (POME).     

An alkaline direct NaBH4–H2O2 fuel cell with high power density

A high performance alkaline direct borohydride–hydrogen peroxide fuel cell with Pt–Ru catalyzed nickel foam as anode and Pd–Ir catalyzed nickel foam as cathode is reported. The electrodes were prepared by electrodeposition of the catalyst components on nickel foam. Their morphology and composition were analyzed by SEM–EDX. The effects of concentrations of NaBH₄ and H₂O₂ as well as operation temperature on the cell performance were investigated. The cell exhibited an open circuit voltage of about 1.0 V and a peak power density of 198 mW cm⁻² at a current density of 397 mA cm⁻² and a cell voltage of 0.5 V using 0.2 mol dm⁻³ NaBH₄ as fuel and 0.4 mol dm⁻³ H₂O₂ as oxidant operating at room temperature. Electrooxidation of NaBH₄ on Pt–Ru nanoparticles was studied using a rotating disk electrode and complete 8e⁻ oxidation was observed in 2 mol dm⁻³ NaOH solution containing 0.01 mol dm⁻³ NaBH₄.     

Photocatalytic H2 production from water splitting under visible light irradiation using Eosin Y-sensitized mesoporous-assembled Pt/TiO2 nanocrystal photocatalyst

Sensitized photocatalytic production of hydrogen from water splitting is investigated under visible light irradiation over mesoporous-assembled titanium dioxide (TiO₂) nanocrystal photocatalysts, without and with Pt loading. The photocatalysts are synthesized by a sol–gel process with the aid of a structure-directing surfactant and are characterized by N₂ adsorption–desorption analysis, X-ray diffraction, UV–vis spectroscopy, scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray analysis. The dependence of hydrogen production on the type of TiO₂ photocatalyst (synthesized mesoporous-assembled and commercial non-mesoporous-assembled TiO₂ without and with Pt loading), the calcination temperature of the synthesized photocatalyst, the sensitizer (Eosin Y) concentration, the electron donor (diethanolamine) concentration, the photocatalyst dosage and the initial solution pH is systematically studied. The results show that in the presence of the Eosin Y sensitizer, the Pt-loaded mesoporous-assembled TiO₂ synthesized by a single-step sol–gel process and calcined at 500 °C exhibits the highest photocatalytic activity for hydrogen production from a 30 vol.% diethanolamine aqueous solution with dissolved 2 mM Eosin Y. Moreover, the optimum photocatalyst dosage and initial solution pH for the maximum photocatalytic activity for hydrogen production are 3.33 g dm⁻³ and 11.5, respectively.     

Study of silicon solar cell at different intensities of illumination and wavelengths using impedance spectroscopy

The electrical properties of an n⁺–p–p⁺ structure-based single-crystalline silicon solar cell were studied by impedance spectroscopy, I–V and spectral response. The impedance spectrum is measured in dark, under different intensities (14, 43, 57, 71, 86, 100 mW/cm²) of illumination and wavelengths (400–1050 nm) of light. Under dark and at low intensities of illumination (<50 mW/cm²) the impedance spectra show perfect semicircles but at high intensities the semicircles are distorted at low frequencies. It is found that illumination provides an additional virtual R₁C₁ network parallel to the initial bulk R_pC_p network observed under dark conditions. The value of virtual resistance R₁ depends on the illumination wavelength and shows an inverse relationship with the spectral response of the device.     

Hydrogen energy in changing environmental scenario: Indian context

This paper deals with how the Hydrogen Energy may play a crucial role in taking care of the environmental scenario/climate change. The R&D efforts, at the Hydrogen Energy Center, Banaras Hindu University have been described and discussed to elucidate that hydrogen is the best option for taking care of the environmental/climate changes. All three important ingredients for hydrogen economy, i.e., production, storage and application of hydrogen have been dealt with. As regards hydrogen production, solar routes consisting of photoelectrochemical electrolysis of water have been described and discussed. Nanostructured TiO₂ films used as photoanodes have been synthesized through hydrolysis of Ti[OCH(CH₃)₂]₄. Modular designs of TiO₂ photoelectrode-based PEC cells have been fabricated to get high hydrogen production rate (10.35 lh⁻¹ m⁻²). However, hydrogen storage is a key issue in the success and realization of hydrogen technology and economy. Metal hydrides are the promising candidates due to their safety advantage with high volume efficient storage capacity for on-board applications. As regards storage, we have discussed the storage of hydrogen in intermetallics as well as lightweight complex hydride systems. For intermetallic systems, we have dealt with material tailoring of LaNi₅ through Fe substitution. The La(Ni_l − xFe_x)₅ (x = 0.16) has been found to yield a high storage capacity of 2.40 wt%. We have also discussed how CNT admixing helps to improve the hydrogen desorption rate of NaAlH₄. CNT (8 mol%) admixed NaAlH₄ is found to be optimum for faster desorption (3.3 wt% H₂ within 2 h). From an applications point of view, we have focused on the use of hydrogen (stored in intermetallic La–Ni–Fe system) as fuel for Internal Combustion (IC) engine-based vehicular transport, particularly two and three-wheelers. It is shown that hydrogen used as a fuel is the most effective alternative fuel for circumventing climate change.     

The photoinduced evolution of O2 and H2 from a WO3 aqueous suspension in the presence of Ce/Ce

This is a report on the production of O₂ and H₂ from photocatalytic and photochemical processes in the WO₃–H₂O–Ce⁴⁺_aq–hν system. The photoproduction of O₂ and H₂ was studied over the range of WO₃ concentrations from 2 to 8 g dm⁻³, and conduction band electron scavenger concentrations 1–20 mM Ce_aq⁴⁺. Medium and high concentrations of the electron scavenger gave mainly O₂ as the main product. Dilute solutions of [Ce_aq⁴⁺]< 2 mM initially produced dioxygen, and then hydrogen after an induction period of 3–4 h. Yields of 140–250 μmol O₂  h⁻¹ and 1–7 μmol H₂ h⁻¹ were obtained and were found to depend on the physical properties and content of WO₃, the concentration of the electron scavenger, illumination period and wavelength, and the radiation geometry. The photoactivity of the suspension was correlated to the level of crystallinity of WO₃ powders. The studied system utilizes WO₃ to accomplish the initial light absorption, charge separation, and production of O₂ and H⁺ from the interaction of water molecules with photogenerated WO₃ valence band holes, in the presence of Ce⁴⁺_aq species as a scavenger of conduction band electrons. This is followed by the evolution of H₂ from a homogeneous photochemical reduction of H⁺ and/or H₂O by photoexcited Ce³⁺_aq, formed from the earlier reduction of Ce⁴⁺_aq. The obtained results show that, with an appropriate design, tungsten trioxide is a promising material that can be used as a photoactive component in energy conversion systems or in environmental photocatalysis, using artificial or solar light.     

Performance and emission comparison of a supercharged dual-fuel engine fueled by producer gases with varying hydrogen content

This study investigated the effect of hydrogen content in producer gas on the performance and exhaust emissions of a supercharged producer gas–diesel dual-fuel engine. Two types of producer gases were used in this study, one with low hydrogen content (H₂ = 13.7%) and the other with high hydrogen content (H₂ = 20%). The engine was tested for use as a co-generation engine, so power output while maintaining a reasonable thermal efficiency was important. Experiments were carried out at a constant injection pressure and injection quantity for different fuel–air equivalence ratios and at various injection timings. The experimental strategy was to optimize the injection timing to maximize engine power at different fuel–air equivalence ratios without knocking and within the limit of the maximum cylinder pressure. Two-stage combustion was obtained; this is an indicator of maximum power output conditions and a precursor of knocking combustion. Better combustion, engine performance, and exhaust emissions (except NO_x) were obtained with the high H₂-content producer gas than with the low H₂-content producer gas, especially under leaner conditions. Moreover, a broader window of fuel–air equivalence ratio was found with highest thermal efficiencies for the high H₂-content producer gas.     

Acid hydrolysis of corn stover for biohydrogen production using Thermoanaerobacterium thermosaccharolyticum W16

Lignocellulosic biomass, if properly hydrolyzed, can be an ideal feedstock for fermentative hydrogen production. This work considered the pretreatment of corn stover (CS) using a dilute acid hydrolysis process and studied its fermentability for hydrogen production by the strain Thermoanaerobacterium thermosaccharolyticum W16. The effects of sulfuric acid concentration and reaction time in the hydrolysis stage of the process were determined based on a 2² central composite experimental design with respect to maximum hydrogen productivity. The optimal hydrolysis conditions to yield the maximum quantity of hydrogen by W16 were 1.69% sulfuric acid and 117 min reaction time. At these conditions, the hydrogen yield was shown to be 3305 ml H₂ L⁻¹ medium, which corresponds to 2.24 mol H₂ mol⁻¹ sugar. The present results indicate the potential of using T. thermosaccharolyticum W16 for high-yield conversion of CS hemicellulose into bio-H₂ integrated with acid hydrolysis.