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Hydrogen Production Rate (hydrogen + production_rate)
Selected AbstractsAcclimation Strategy of a Biohydrogen Producing Population in a Continuous-Flow Reactor with Carbohydrate FermentationENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 4 2006Q. Ren Abstract Poor startup of biological hydrogen production systems can cause an ineffective hydrogen production rate and poor biomass growth at a high hydraulic retention time (HRT), or cause a prolonged period of acclimation. In this paper a new startup strategy was developed in order to improve the enrichment of the hydrogen-producing population and the efficiency of hydrogen production. A continuously-stirred tank reactor (CSTR) and molasses were used to evaluate the hydrogen productivity of the sewage sludge microflora at a temperature of 35,°C. The experimental results indicated that the feed to microorganism ratio (F/M ratio) was a key parameter for the enrichment of hydrogen producing sludge in a continuous-flow reactor. When the initial biomass was inoculated with 6.24,g of volatile suspended solids (VSS)/L, an HRT of 6,h, an initial organic loading rate (OLR) of 7.0,kg chemical oxygen demand (COD)/(m3,×,d) and an feed to microorganism ratio (F/M) ratio of about 2,3,g COD/(g of volatile suspended solids (VSS) per day) were maintained during startup. Under these conditions, a hydrogen producing population at an equilibrium state could be established within 30,days. The main liquid fermentation products were acetate and ethanol. Biogas was composed of H2 and CO2. The hydrogen content in the biogas amounted to 47.5,%. The average hydrogen yield was 2.01,mol/mol hexose consumed. It was also observed that a special hydrogen producing population was formed when this startup strategy was used. It is supposed that the population may have had some special metabolic pathways to produce hydrogen along with ethanol as the main fermentation products. [source] Bio-hydrogen production from acetic acid steam-exploded corn straws by simultaneous saccharification and fermentation with Ethanoligenens harbinense B49INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 5 2010Ji-Fei Xu Abstract Bio-hydrogen produced from acetic acid steam-exploded corn straw (ASCS) by simultaneous saccharification and fermentation (SSF) with Ethanoligenes harbinense 49. The effects of acetic acid concentration and enzyme loading were investigated with respect to the maximum specific hydrogen production rate and hydrogen productivity. The hydrogen yield increased with increasing of acetic acid concentration, increased and then decreased with increasing of enzyme loading. The effect of enzyme loading for hydrogen production was more crucial than that of the acetic acid concentration. At acetic acid concentration of 16% and enzyme loading of 120 and 180,U/g, the maximum hydrogen yield and maximum specific hydrogen production rate was 72,ml/g ASCS and 103,ml/g VSS·d, respectively. Copyright © 2009 John Wiley & Sons, Ltd. [source] Exploration of the hydrogen producing potential of Rhodobacter capsulatus chemostat cultures: The application of deceleration-stat and gradient-stat methodologyBIOTECHNOLOGY PROGRESS, Issue 5 2009Sebastiaan Hoekema Abstract In this work, the dependency of the volumetric hydrogen production rate of ammonium-limited Rhodobacter capsulatus chemostat cultures on their imposed biomass concentration and dilution rate was investigated. A deceleration-stat experiment was performed by lowering the dilution rate from 1.0 d,1 to zero aimed at a constant biomass concentration of 4.0 g L,1 at constant incident light intensity. The results displayed a maximal volumetric hydrogen production rate of 0.6 mmol m,3 s,1, well below model predictions. Possibly the high cell density limited the average light availability, resulting in a sub-optimal specific hydrogen production rate. To investigate this hypothesis, a gradient-stat experiment was conducted at constant dilution rate of 0.4 d,1 at constant incident light intensity. The biomass concentration was increased from 0.7 to 4.0 g L,1 by increasing the influent ammonium concentration. Up to a biomass concentration of 1.5 g L,1, the volumetric hydrogen production rate of the system increased according to model predictions, after which it started to decline. The results obtained provide strong evidence that the observed decline in volumetric hydrogen production rate at higher biomass concentrations was at least partly caused by a decrease in light availability. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Modeling and Optimization of Photosynthetic Hydrogen Gas Production by Green Alga Chlamydomonas reinhardtii in Sulfur-Deprived CircumstanceBIOTECHNOLOGY PROGRESS, Issue 2 2006Ji Hye Jo Biological hydrogen production by the green alga Chlamydomonas reinhardtii under sulfur-deprived conditions has attracted great interest due to the fundamental and practical importance of the process. The photosynthetic hydrogen production rate is dependent on various factors such as strain type, nutrient composition, temperature, pH, and light intensity. In this study, physicochemical factors affecting biological hydrogen production by C. reinhardtii were evaluated with response surface methodology (RSM). First, the maximum specific growth rate of the alga associated with simultaneous changes of ammonium, phosphate, and sulfate concentrations in the culture medium were investigated. The optimum conditions were determined as NH4+ 8.00 mM, PO43, 1.11 mM, and SO42, 0.79 mM in Tris-acetate-phosphate (TAP) medium. The maximum specific growth rate with the optimum nutrient concentrations was 0.0373 h,1. Then, the hydrogen production rate of C. reinhardtii under sulfur-deprivation conditions was investigated by simultaneously changing two nutrient concentrations and pH in the medium. The maximum hydrogen production was 2.152 mL of H2 for a 10-mL culture of alga with density of 6 × 106 cells mL,1 for 96 h under conditions of NH4+ 9.20 mM, PO43, 2.09 mM, and pH 7.00. The obtained hydrogen production rate was approximately 1.55 times higher than that with the typical TAP medium under sulfur deficiency. [source] Microbial Hydrogen Production with Immobilized Sewage SludgeBIOTECHNOLOGY PROGRESS, Issue 5 2002Shu-Yii Wu Municipal sewage sludge was immobilized to produce hydrogen gas under anaerobic conditions. Cell immobilization was essentially achieved by gel entrapment approaches, which were physically or chemically modified by addition of activated carbon (AC), polyurethane (PU), and acrylic latex plus silicone (ALSC). The performance of hydrogen fermentation with a variety of immobilized-cell systems was assessed to identify the optimal type of immobilized cells for practical uses. With sucrose as the limiting carbon source, hydrogen production was more efficient with the immobilized-cell system than with the suspended-cell system, and in both cases the predominant soluble metabolites were butyric acid and acetic acid. Addition of activated carbon into alginate gel (denoted as CA/AC cells) enhanced the hydrogen production rate ( vH2) and substrate-based yield ( YH2/sucrose) by 70% and 52%, respectively, over the conventional alginate-immobilized cells. Further supplementation of polyurethane or acrylic latex/silicone increased the mechanical strength and operation stability of the immobilized cells but caused a decrease in the hydrogen production rate. Kinetic studies show that the dependence of specific hydrogen production rates on the concentration of limiting substrate (sucrose) can be described by Michaelis-Menten model with good agreement. The kinetic analysis suggests that CA/AC cells may contain higher concentration of active biocatalysts for hydrogen production, while PU and ALSC cells had better affinity to the substrate. Acclimation of the immobilized cells led to a remarkable enhancement in vH2 with a 25-fold increase for CA/AC and ca. 10- to 15-fold increases for PU and ALSC cells. However, the ALSC cells were found to have better durability than PU and CA/AC cells as they allowed stable hydrogen production for over 24 repeated runs. [source] | ||||||||||