Biomass and biohydrogen production during dark fermentation of Escherichia coli using office paper waste and cardboard

Growth properties, oxidation-reduction potential kinetics and hydrogen production of Escherichia coli BW25113 parental strain (PS) and hydrogenase (Hyd)-negative mutants were investigated after fermentative growth using office paper waste and cardboard (PW) hydrolysate (PWH). PWH was obtained by using dilute acid method in a steam sterilizer for 1 h, 121 °C. Optimal conditions for bacterial growth and H₂ production were identified (PWH concentrations, pH 7.5). Recording of redox potential using a platinum electrode revealed a drop to −500 ± 10 mV, with a H₂ yield of ~1.45 mmol H₂ L⁻¹ after 4 h of growth using PWH resulted in the formation of 0.20 ± 0.02 g bacterial cell dry weight L⁻¹. Bacterial biomass formation was stimulated ~3-fold upon addition of 0.5% yeast extract, and H₂ production started early - at the beginning of the exponential phase. Moreover, mutants lacking Hyd-1 and Hyd-2 significantly enhanced H₂ production. The findings would be beneficial for the development of H₂ production biotechnology using cheap solid waste materials.     

Hydrogen production by Escherichia coli growing in different nutrient media with glycerol: Effects of formate,pH, production kinetics and hydrogenases involved

The Escherichia coli BW25113 or MC4100 wild type parental strains growth and H₂ production kinetics was studied in batch cultures of minimal salt medium (MSM) and peptone medium (PM) at pH of 5.5–7.5 upon glycerol (10 g L^?1) fermentation and formate (0.68 g L^?1) supplementation. The role of formate alone or with glycerol on growth and H₂ production via hydrogenases (Hyd) was investigated in double hyaB hybC (lacking large subunits of Hyd 1 and 2), triple hyaB hybC hycE (lacking large subunits of Hyds 1-3) and sole selC (lacking formate dehydrogenase H) mutants during 24 h bacterial growth. H₂ production was delayed and observed after 24 h bacterial wild type strains growth on MSM. Moreover, it reached the maximal values after 72 h growth at the pH 6.5 and pH 7.5. Biomass formation of the mutants used was inhibited ～3.5 fold compared with wild type, and H₂ production was absent in hyaB hybC hycE and selC mutants upon glycerol utilization on MSM at pHs of 5.5–7.5. Formate inhibited bacterial growth on MSM with glycerol, but enhanced and recovered H₂ production by hybC mutant at pH 7.5. H₂ evolution was delayed at pH 7.5 in PM, but observed and stimulated at pH 6.5 upon glycerol and formate utilization in hyaB hybC mutant. H₂ production was absent in hyaB hybC hycE and selC mutants upon glycerol, formate alone or with glycerol fermentation at pH 6.5 and pH 7.5; formate supplementation had no effect. The results point out E. coli ability to grow and utilize glycerol in MSM with comparably high H₂ yield: as well as they suggest the key role of Hyd-3 at both pH 6.5 and pH 7.5 and the role of Hyd-2 and Hyd-4 at pH 7.5 in H₂ production by E. coli during glycerol fermentation with formate supplementation. The results obtained are novel and might be useful in H₂ production biotechnology development using different nutrient media and glycerol and formate as feedstock.     

Hydrogen production by Escherichia coli during anaerobic utilization of mixture of lactose and glycerol: Enhanced rate and yield,prolonged production

Escherichia coli wild type has the ability to utilize lactose or the mixture of lactose and glycerol producing bio-hydrogen (H₂) at different pH values. At pH 7.5 in hyaB (lacking large subunit of hydrogenase (Hyd)-1) and hybC (lacking large subunit of Hyd-2) single mutants fermenting lactose (1 g L⁻¹) H₂ yield was ∼7- and 5-fold more, respectively, compared to the wild type. During the fermentation of lactose (1 g L⁻¹) and glycerol (10 g L⁻¹) mixture H₂ yield in wild type increased ∼3-fold, compared to fermenting lactose only. H₂ generation in wild type was monitored in batch cultures during 168 h of growth when utilizing the mixture of lactose and glycerol in all combinations of different concentration. In hyaB but not in hybC mutant H₂ evolution was detected till 240 h in the mixture of 5 g L⁻¹ lactose and 10 g L⁻¹ glycerol. The highest H₂ production rate of 21.94 mL L⁻¹ h⁻¹ was detected in hyaB mutant at pH 7.5 when 1 g L⁻¹ lactose was applied. The results showed optimized H₂ production using different mutants, lactose and its mixture with glycerol. They can be applied for renewable energy, especially bio-H₂ production.     

Different role of focA and focB encoding formate channels for hydrogen production by Escherichia coli during glucose or glycerol fermentation

The dependence of H₂ production on the formate channels, FocA and FocB, by Escherichia coli at pH 5.5, 6.5 and 7.5 was shown using focA and focB mutants and comparing with the wild type. Moreover, effect of exogenous addition of formate (10 mM) on H₂ production was allotted. The results acquired propose that during glucose fermentation formate import can occur through FocB at different pHs; external formate drives FocA to import direction. However, during glycerol fermentation formate might be imported through FocB, whereas formate is exported preferentially through FocA at pH 7.5.     

Enhancement of Escherichia coli bacterial biomass and hydrogen production by some heavy metal ions and their mixtures during glycerol vs glucose fermentation at a relatively wide range of pH

Escherichia coli growth and H₂ production were followed in the presence of heavy metal ions and their mixtures during glycerol or glucose fermentation at pH 5.5–7.5. Ni²⁺ (50 μM) with Fe²⁺ (50 μM) but not sole metals stimulated bacterial biomass during glycerol fermentation at pH 6.5. Ni²⁺+Fe³⁺ (50 μM), Ni² +Fe³⁺+Mo⁶⁺ (20 μM) and Fe³⁺+Mo⁶⁺ (20 μM) but not sole metals enhanced up to 3-fold H₂ yield but Cu⁺ or Cu²⁺ (100 μM) inhibited it. At pH 7.5 stimulating effect on biomass was observed by Ni²⁺+Fe²⁺+Mo⁶⁺. H₂ production was enhanced 2.7 fold particularly by Ni²⁺+Fe³⁺+Mo⁶⁺ at the late stationary growth phase. Whereas at pH 5.5 increased biomass was when Fe²⁺+Mo⁶⁺ or Mo⁶⁺ were added. H₂ yield was decreased compared with that at pH 6.5, but metal ions again enhanced it. During glucose fermentation at pH 6.5 biomass was increased by the mixtures of metal ions, and 1.2 fold increased H₂ yield was observed. At pH 7.5 Ni²⁺+Fe²⁺ increased biomass but Cu⁺ or Cu²⁺ had suppressing effect; Fe³⁺+Mo⁶⁺ stimulated H₂ production. At pH 5.5 biomass also was raised by Ni²⁺+Fe²⁺+Mo⁶⁺; H₂ yield was increased upon Mo⁶⁺ and Mo⁶⁺+Fe²⁺ or Mo⁶⁺+Fe³⁺ additions. The results point out the importance of Ni²⁺, Fe²⁺, Fe³⁺ and Mo⁶⁺ and some of their combinations for E. coli bacterial growth and H₂ production mostly during glycerol but not glucose fermentation and at acidic conditions (pH 5.5 and 6.5). They can be used for optimizing fermentation processes on glycerol, controlling bacterial biomass and developing H₂ production biotechnology.     

Modeling,optimization, and control of microbial electrolysis cells in a fed‐batch reactor for production of renewable biohydrogen gas

An integrated modeling, optimization, and control approach for the design of a microbial electrolysis cell (MEC) was studied in this paper. Initially, this study describes the improvement of the mathematical MEC model for hydrogen production from wastewater in a fed‐batch reactor. The model, which was modified from an already existing model, is based on material balance with the integration of bioelectrochemical reactions describing the steady‐state behavior of biomass growth, consumption of substrates, hydrogen production, and the effect of applied voltage on the performance of the MEC fed‐batch reactor. Another goal of this work is to implement a suitable control strategy to optimize the production of biohydrogen gas by selecting the optimal current and applied voltage to the MEC. Various simulation tests involving multiple set‐point changes, disturbance rejection, and noise effects were performed to evaluate the performance where the proposed proportional–integral–derivative control system was tuned with an adaptive gain technique and compared with the Ziegler–Nichols method. The simulation results show that optimal tuning can provide better control effect on the MEC system, where optimal H₂ gas production for the system was achieved. Copyright © 2014 John Wiley & Sons, Ltd.     

Cost-effective policy instruments for greenhouse gas emission reduction and fossil fuel substitution through bioenergy production in Austria

Climate change mitigation and security of energy supply are important targets of Austrian energy policy. Bioenergy production based on resources from agriculture and forestry is an important option for attaining these targets. To increase the share of bioenergy in the energy supply, supporting policy instruments are necessary. The cost-effectiveness of these instruments in attaining policy targets depends on the availability of bioenergy technologies. Advanced technologies such as second-generation biofuels, biomass gasification for power production, and bioenergy with carbon capture and storage (BECCS) will likely change the performance of policy instruments. This article assesses the cost-effectiveness of energy policy instruments, considering new bioenergy technologies for the year 2030, with respect to greenhouse gas emission (GHG) reduction and fossil fuel substitution. Instruments that directly subsidize bioenergy are compared with instruments that aim at reducing GHG emissions. A spatially explicit modeling approach is used to account for biomass supply and energy distribution costs in Austria. Results indicate that a carbon tax performs cost-effectively with respect to both policy targets if BECCS is not available. However, the availability of BECCS creates a trade-off between GHG emission reduction and fossil fuel substitution. Biofuel blending obligations are costly in terms of attaining the policy targets.     

Simultaneous biohydrogen production and starch wastewater treatment in an acidogenic expanded granular sludge bed reactor by mixed culture for long-term operation

The biofilm-based expanded granular sludge bed (EGSB) reactor was developed to treat starch-containing wastewater and simultaneously recovery hydrogen by mixed microbial culture. Granular activated carbon (GAC) was used as the support media. Operating at the temperature of 30 °C for over 400 days (data not shown), the EGSB reactor presented high efficiency in hydrogen production and COD removal ability. The maximum hydrogen production rate (HPR) was found to be 1.64 L/L.d under the organic loading rate (OLR) of 1.0 g-starch/L.d, pH of 4.42 and HRT of 4 h. The hydrogen yield (HY) peaked at 0.11 L/g-COD, under the OLR of 0.5 g-starch/L.d, pH of 3.95 and HRT of 8 h. Hydrogen volume content was estimated to be 35–65% of the total biogas. The average COD removal rate was 31.1% under the OLR of 0.125 g-starch/L.d and HRT of 24 h. The main dissolved fermentation products were ethanol, acetate and butyrate. The average attached biofilm concentration was estimated to be 8.26 g/L, which favored hydrogen production and COD removal. It is speculated that the low pH operation in the present system would contribute significantly to lower the cost of alkaline amount required for pH control in the continuous operation, especially in the scale-up biohydrogen producing system. A model, built on the back propagation neural network (BPNN) theory and linear regression techniques, was developed for the simulation of EGSB system performance in the biodegradation of starch synthesis-based wastewater and simultaneous hydrogen production. The model well fitted the laboratory data, and could well simulate the removal of COD and the production of hydrogen in the EGSB reactor.     

Assessment of the availability of agricultural and forest residues for bioenergy production in Romania

This paper provides a resource-based assessment of availability of biomass resources for energy production in Romania, at NUTS-3 level. The estimation of available biomass includes the residues generated from crop production, pruning of vineyards and orchards, forestry operations and wood processing. The estimation of crop residue availability considers several site-specific factors such as crop yields, multi-annual yield variation, environmental constraints and competitive uses. The evaluation of agricultural residues was based on specific residue to product ratios, depending on crop type and crop yield. An estimate of pruning residues is proposed, based on current orchard and vineyard areas and specific ratios of residues. Woody biomass considers forest and forestry residues (including firewood) and wood processing by-products, taking into account the type and share of the unused part of the tree biomass and technical and economic aspects, including availability and competitive use. The amount of agricultural and forest residues available for bioenergy in Romania was estimated at 228.1 PJ on average, of which 137.1 PJ was from annual crop residues, 17.3 PJ residues from permanent crops and 73.7 PJ/year from forestry residues, firewood and wood processing by-products. The biomass availability shows large annual and spatial variations, between 135.6 and 320.0 PJ, due to the variation in crop production and forestry operations. This variation, which is even larger at the NUTS-3 level, if not properly considered may result in shortages in biomass supply in some years, when biomass is available in a lower amount than the average.     

Defining the roles of the hydrogenase 3 and 4 subunits in hydrogen production during glucose fermentation: A new model of a H2-producing hydrogenase complex

Hydrogen (H₂)-producing hydrogenase (Hyd) activity of E. coli wild type and mutants with defects in subunits of Hyd-3 or Hyd-4 during fermentation at different glucose concentrations and pHs was studied. Hyd-3 was mainly responsible for H₂ production but a significant contribution by Hyd-4 to total H₂ production depended on the glucose concentration and pH. Surprisingly, not all Hyd-3 or Hyd-4 subunits contributed towards H₂ production. Hyd-4 mainly exhibited H₂-oxidizing activity in cells growing on 0.2% glucose at pH 7.5, while at pH 5.5 it had a significant impact on H₂ production. Importantly, a hyfG mutant (lacking the large subunit of Hyd-4) had a ~2.2 fold decrease in H₂ production when cells were grown with 0.2% glucose. A similar role of Hyd-4 was shown at pH 6.5 grown with 0.8% glucose. This study provides new information to allow improvements in H₂ production yield and in our general understanding of H₂ metabolism.     

National strategies for stimulating the use of bioenergy: policy instruments in Sweden

This study examines strategies of national energy policy, focusing on measures taken from the 1970s onwards for increasing the use of bioenergy in the Swedish energy system. Emphasis is given to analyses of how administrative policy instruments such as the Building Act, which regulates the use of natural resources, and the Wood Fibre Act have affected the woodfuel market for the district heating sector. The government can influence changes in three principal areas of the energy system: energy use, industrial structure, and energy production. The tools the government may use to exert its influence are: support to research and development, support to demonstration and information dissemination, administrative policy measures, and economic incentives. These instruments may be applied separately or in combination. Knowledge about how these instruments affect the development of the energy sector is fragmentary; it derives more from empirical observation than from analysis. A systematic evaluation of the separate and combined instruments that have been used would increase the possibility of correctly assessing the national energy policy. Nevertheless, practical experience and the analyses that do exist indicate that: (1) research and development are necessary prerequisites for developing the energy system even though results can not always be achieved in time to meet the need for fast results; (2) economic policy measures are comparatively easy to administer, and energy taxation has largely met its goals. With investment support, markets can be skewed and development can be hindered if existing technology is subsidised; (3) administrative policy instruments are cumbersome to administer and frequently do not achieve their purpose.     

Escherichia coli hydrogenase 4 (hyf) and hydrogenase 2 (hyb) contribution in H2 production during mixed carbon (glucose and glycerol) fermentation at pH 7.5 and pH 5.5

Molecular hydrogen (H₂) production by Escherichia coli was studied during mixed carbon sources (glucose and glycerol) fermentation at pH 7.5 and pH 5.5. H₂ production rate (V_H2) by bacterial cells grown on mixed carbon was assayed with either adding glucose (glucose assay) or glycerol (glycerol assay) and compared with the cells grown on sole carbon (glucose or glycerol only) and appropriately assayed. Wild type cells grown on mixed carbon, in the assays with adding glucose, produced H₂ at pH 7.5 with the same level as in the cells grown on glucose only. At pH 7.5 V_H2 in fhlA single and fhlA hyfG double mutants decreased ∼6.5 and ∼7.9 fold, respectively. In wild type cells grown on mixed carbon V_H2 at pH 5.5 was lowered ∼2 fold, compared to the cells grown on glucose only. But in hyfG and hybC single mutants V_H2 was decreased ∼2 and ∼1.6 fold, respectively. However, at pH 7.5, in the assays with glycerol, V_H2 was low, when compared to the cells grown on glycerol only. At pH 5.5 in the assays with glycerol V_H2 was absent. Moreover, V_H2 in wild type cells was inhibited by 0.3 mM N,N^′-dicyclohexylcarbodiimide (DCCD), an inhibitor of the F₀F₁-ATPase, in a pH dependent manner. At pH 7.5 in wild type cells V_H2 was decreased ∼3 fold but at pH 5.5 the inhibition was ∼1.7 fold. At both pHs in fhlA mutant V_H2 was totally inhibited by DCCD. Taken together, the results obtained indicate that at pH 7.5, in the presence of glucose, glycerol can also be fermented. They point out that Hyd-4 mainly and Hyd-2 to some extent contribute in H₂ production by E. coli during mixed carbon fermentation at pH 5.5 whereas Hyd-1 is only responsible for H₂ oxidation.     

Improvement of biohydrogen production from brewery wastewater: Evaluation of inocula,support and reactor

This work explores the production of biohydrogen from brewery wastewater using as inoculum a culture produced by natural fermentation of synthetic wastewater and Klebsiella pneumoniae isolated from the environment. Klebsiella pneumoniae showed good performance as inoculum, as evaluated using assays of between 9 and 16 cycles, with durations of 12 and 24 h, carbohydrate concentrations from 2.79 to 7.22 g L⁻¹, and applied volumetric organic loads from 2.6 to 12.6 g carbohydrate L⁻¹ day⁻¹. The best results were achieved with applied volumetric organic loads of 12.6 g carbohydrate L⁻¹ day⁻¹ and cycle length of 12 h, resulting in mean volumetric productivity of 0.88 L H₂ L⁻¹ day⁻¹, maximum molar flow of 10.80 mmol H₂ h⁻¹, and mean yield of 0.70 mol H₂ mol⁻¹ glucose consumed. The biogas H₂ content was between 18 and 42%, while the mean organic compounds removal and carbohydrate conversion efficiencies were 23 and 81%, respectively. The inoculum produced by natural fermentation was not viable.     

京能热电4号机组循环水余热利用工程综述

介绍了循环水余热利用实施的背景,描述了工程项目的各个组成系统以及增热型热泵工作原理,并对项目实施前后热网运行方式不同进行了比较,分析了项目投运后的运行工况和经济效益。     

A liquefied energy chain for transport and utilization of natural gas for power production with CO2 capture and storage – Part 4: Sensitivity analysis of transport pressures and benchmarking with conventional technology for gas transport

A novel energy and cost effective transport chain for stranded natural gas utilized for power production with CO₂ capture and storage is developed. It includes an offshore section, a combined gas carrier and an integrated receiving terminal. In the offshore section, natural gas (NG) is liquefied to LNG by liquid carbon dioxide (LCO₂) and liquid inert nitrogen (LIN), which are used as cold carriers. In the onshore process, the cryogenic exergy in the LNG is utilized to cool and liquefy the cold carriers, LCO₂ and LIN. The transport pressures for LNG, LIN and LCO₂ will influence the thermodynamic efficiency as well as the ship utilization; hence sensitivity analyses are performed, showing that the ship utilization for the payload will vary between 58% and 80%, and the transport chain exergy efficiency between 48% and 52%. A thermodynamically optimized process requires 319 kWh/tonne LNG. The NG lost due to power generation needed to operate the LEC processes is roughly one third of the requirement in a conventional transport chain for stranded NG gas with CO₂ capture and sequestration (CCS).     

Optimal integration of a biomass-based polygeneration system in an iron production plant for negative carbon emissions

The iron industry is an energy-intensive sector and a major contributor to global carbon dioxide emissions. With the projected increase in the demand for iron as raw material, the industry seeks ways to improve sustainability. The incorporation of a biomass-based polygeneration system (BBPS) is a sustainable approach to generate the needed utilities of the iron plant. Biomass can be converted thermochemically into fuel gas for use in the plant, while the resulting biochar can be utilized for carbon sequestration. A multiobjective optimization model using fuzzy linear programming (FLP) is developed to seamlessly integrate a BBPS in an iron plant while obtaining negative carbon emissions. The FLP model simultaneously satisfied the product demands while maximizing the annual profit and minimizing the carbon footprint of the iron manufacturing plant. A sensitivity study is performed to gauge the effects of uncertainties of the prices of product streams and capital costs together. The best configuration of the integrated BBPS and the iron production plant are determined using this approach, resulting in 2.7 million tons CO₂ y⁻¹ of negative carbon emission. The reduction of the carbon footprint upper threshold target by 80% has shown a 34.15% improvement on the negative carbon footprint and 1.81% enhancement on the annualized capital cost of the plant. The change in the biomass price had a significant effect on the Pareto frontier of the level of satisfaction compared with the change in the coal and iron ore prices. The varied capital cost of the gasification had a relatively significant influence to the annualized profit of the plant compared with the varied capital cost of the other polygeneration processes.     

Optimizing feedstock selection for biofuel production in Hawaii: CuO oxidative lignin products in C4 grasses

Global interest in renewable fuels is rapidly growing with particular emphasis on local energy growth and creating new energy feedstocks, specifically liquid fuel sources. However, the interactive effect of plant species/variety and growth environment on plant structural components, which may influence conversion efficiency and thus play an important role in optimizing the production of biofuels, is not fully understood. In this study cupric oxide (CuO) extractable lignin, which extracts and quantifies lignin-derived monomers, was determined for 25 cultivated and naturalized tropical perennial C₄ grass varieties of napiergrass and Guinea grass that were under assessment for suitability as feedstocks for liquid fuel generation. Principal component analysis of CuO extractable lignin-derived monomers showed differences in composition between napiergrass and Guinea grass, as well as environmental differences within many, but not all napiergrass varieties. Among the samples tested, the greatest differences in lignin composition occurred specifically in vanillyl lignin structures. A wide range (1–2.5) in the ratio of cinnamyl to vanillyl structures (C/V), which often relates to enzymatic degradability in natural systems, was also found. It is expected that the observed CuO lignin differences representing the structure and bonding of lignin will relate to ease of chemical and enzymatic conversion and the effectiveness of pretreatment and conversion in biofuel application. We hypothesize that the C/V ratio of feedstock will positively relate to conversion efficiency and if supported, then compositional lignin metrics such as the C/V ratio could be a predictor to select for more easily degradable biomass for biofuel production.     

Hydrogen production by methane pyrolysis in molten binary copper alloys

The utilization of hydrogen as an energy carrier and reduction agent in important industrial sectors is considered a key parameter on the way to a sustainable future. Steam reforming of methane is currently the most industrially used process to produce hydrogen. One major drawback of this method is the simultaneous generation of carbon dioxide. Methane pyrolysis represents a viable alternative as the basic reaction produces no CO₂ but solid carbon besides hydrogen. The aim of this study is the investigation of different molten copper alloys regarding their efficiency as catalytic media for the pyrolysis of methane in an inductively heated bubble column reactor. The conducted experiments demonstrate a strong influence of the catalyst in use on the one hand on the conversion rate of methane and on the other hand on the properties of the produced carbon. Optimization of these parameters is of crucial importance to achieve the economic competitiveness of the process.