The relative effectiveness of pH control and heat treatment for enhancing biohydrogen gas production.
15 Nov 2003-Environmental Science & Technology (American Chemical Society)-Vol. 37, Iss: 22, pp 5186-5190
TL;DR: Results show that low pH was, without heat treatment, sufficient to control hydrogen losses to methanogens in mixed batch cultures and suggest that methods will need to be found to limit acetogenesis in order to increase hydrogen gas yields by batch cultures.
Abstract: Hydrogen gas can be recovered from the microbial fermentation of organic substrates at high concentrations when interspecies hydrogen transfer to methanogens is prevented. Two techniques that have been used to limit methanogenesis in mixed cultures are heat treatment, to remove nonsporeforming methanogens from an inoculum, and low pH during culture growth. We found that high hydrogen gas concentrations (57-72%) were produced in all tests and that heat treatment (HT) of the inoculum (pH 6.2 or 7.5) produced greater hydrogen yields than low pH (6.2) conditions with a nonheat-treated inoculum (NHT). Conversion efficiencies of glucose to hydrogen (based on a theoretical yield of 4 mol-H2/mol-glucose) were as follows: 24.2% (HT, pH = 6.2), 18.5% (HT, pH = 7.5), 14.9% (NHT, pH = 6.2), and 12.1% (NHT, pH = 7.5). The main products of glucose (3 g-COD/L) utilization (> or = 99%) in batch tests were acetate (3.4-24.1%), butyrate (6.4-29.4%), propionate (0.3-12.8%), ethanol (15.4-28.8%), and hydrogen (4.0-8.1%), with lesser amounts of acetone, propanol, and butanol (COD basis). Hydrogen gas phase concentrations in all batch cultures reached a maximum of 57-72% after 30 h but thereafter rapidly declined to nondetectable levels within 80 h. Separate experiments showed substantial hydrogen losses could occur via acetogenesis and that heat treatment did not prevent acetogenesis. Heat treatment consistently eliminated the production of measurable concentrations of methane. The disappearance of ethanol produced during hydrogen production was likely due to acetic acid production as thermodynamic calculations show that this reaction is spontaneous once hydrogen is depleted. Overall, these results show that low pH was, without heat treatment, sufficient to control hydrogen losses to methanogens in mixed batch cultures and suggest that methods will need to be found to limit acetogenesis in order to increase hydrogen gas yields by batch cultures.
Citations
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TL;DR: There are several biological processing strategies that produce bioenergy or biochemicals while treating industrial and agricultural wastewater, including methanogenic anaerobic digestion, biological hydrogen production, microbial fuel cells and fermentation for production of valuable products, but there are also scientific and technical barriers to the implementation of these strategies.
1,122 citations
Cites methods from "The relative effectiveness of pH co..."
...... I in Box 1, group d). Inhibition is commonly accomplished by heat treatment of the inoculum to kill all microorganisms except for spore-forming fermenting bacteria (for example, species from the families Clostridiaceae, Streptococcaceae, Sporolactobacillaceae, Lachnospiraceae, and Thermoanaerobacteriacea [15‐17] )( seeFigure I ai n Box 1). Other methods that have been used include the operationofreactorsathighdilutionrates[18]orlowpH[ 19 ]....
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TL;DR: The materials, architectures, performance, and energy efficiencies of these MEC systems that show promise as a method for renewable and sustainable energy production, and wastewater treatment are reviewed.
Abstract: The use of electrochemically active bacteria to break down organic matter, combined with the addition of a small voltage (>0.2 V in practice) in specially designed microbial electrolysis cells (MECs), can result in a high yield of hydrogen gas. While microbial electrolysis was invented only a few years ago, rapid developments have led to hydrogen yields approaching 100%, energy yields based on electrical energy input many times greater than that possible by water electrolysis, and increased gas production rates. MECs used to make hydrogen gas are similar in design to microbial fuel cells (MFCs) that produce electricity, but there are important differences in architecture and analytical methods used to evaluate performance. We review here the materials, architectures, performance, and energy efficiencies of these MEC systems that show promise as a method for renewable and sustainable energy production, and wastewater treatment.
1,062 citations
TL;DR: The results demonstrate that high hydrogen recovery and production rates are possible in a single chamber MEC without a membrane, potentially reducing the costs of these systems and allowing for new and simpler designs.
Abstract: Hydrogen gas can be produced by electrohydrogenesis in microbial electrolysis cells (MECs) at greater yields than fermentation and at greater energy efficiencies than water electrolysis. It has been assumed that a membrane is needed in an MEC to avoid hydrogen losses due to bacterial consumption of the product gas. However, high cathodic hydrogen recoveries (78 ± 1% to 96 ± 1%) were achieved in an MEC despite the absence of a membrane between the electrodes (applied voltages of 0.3 < Eap < 0.8 V; 7.5 mS/cm solution conductivity). Through the use of a membrane-less system, a graphite fiber brush anode, and close electrode spacing, hydrogen production rates reached a maximum of 3.12 ± 0.02 m3 H2/m3 reactor per day (292 ± 1 A/m3) at an applied voltage of Eap = 0.8 V. This production rate is more than double that obtained in previous MEC studies. The energy efficiency relative to the electrical input decreased with applied voltage from 406 ± 6% (Eap = 0.3 V) to 194 ± 2% (Eap = 0.8 V). Overall energy efficienc...
778 citations
TL;DR: In this paper, over 160 publications related to fermentative hydrogen production from wastewater and solid wastes by mixed cultures are compiled and analyzed, including pre-treatment conditions for screening hydrogen-producing bacteria from anaerobic sludge or soil, and the process and performance parameters for (2) single substrates in synthetic wastewaters, (3) actual wastewater, and (4) solid wastes.
Abstract: Over 160 publications related to fermentative hydrogen production from wastewater and solid wastes by mixed cultures are compiled and analyzed. Of the 98 reported cases, 57 used single substrates (mainly carbohydrates), 8 used actual wastewater, and 33 used solid wastes for hydrogen conversion. The key information is compiled in four tables: (1) pretreatment conditions for screening hydrogen-producing bacteria from anaerobic sludge or soil, and the process and performance parameters for (2) single substrates in synthetic wastewaters, (3) actual wastewaters, and (4) solid wastes. Process parameters discussed include pH, temperature, hydraulic retention time, seed sludge, nutrients, inhibitors, reactor design, and the means used for lowering hydrogen partial pressure. Performance parameters discussed include hydrogen yield, maximum volumetric production rate, maximum specific production rate, and conversion efficiency. The outlook for this new technology is discussed at the end.
758 citations
Cites background from "The relative effectiveness of pH co..."
...Treating an anaerobic sludge under harsh conditions, Clostridium would have a better chance to survive than the non-spore-forming bacteria, many of which hydrogen consumers ( Lay, 2001 ; Oh et al, 2003a )....
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...Treating an anaerobic sludge under harsh conditions, Clostridium would have a better chance to survive than the non-spore-forming bacteria, many of which hydrogen consumers (Lay, 2001; Oh et al., 2003a)....
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...V.B. Phosphate A few studies found that phosphate was needed in hydrogen production for its nutritious value as well as buffering capacity (Oh et al., 2002, 2003b; Lin and Lay, 2004b)....
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...On the other hand, some reported that heat treatment could not inhibit the activity of all hydrogen-consuming bacteria (Oh et al., 2003a)....
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TL;DR: In this article, the authors focus on dark fermentation as a key technology for producing hydrogen from crop residues, livestock waste and food waste, considering that such wastes are complex substrates and can be degraded biologically by complex microbial ecosystems.
706 citations
Cites background from "The relative effectiveness of pH co..."
...Unfortunately, the pretreatment of the inoculum by heating to select spore-forming bacteria is not suitable for inhibiting of homoacetogenic bacteria since some of them belong to the same genus Clostridium [110]....
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...[110] Oh S, Van Ginkel S, Logan BE....
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References
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TL;DR: In this article, a method was developed to determine submicro amounts of sugars and related substances using a phenol-sulfuric acid reaction, which is useful for the determination of the composition of polysaccharides and their methyl derivatives.
Abstract: Simple sugars, oligosaccharides, polysaccharides, and their derivatives, including the methyl ethers with free or potentially free reducing groups, give an orangeyellow color w-hen treated with phenol and concentrated sulfuric acid. The reaction is sensitive and the color is stable. By use of this phenol-sulfuric acid reaction, a method has been developed to determine submicro amounts of sugars and related substances. In conjunction with paper partition chromatography the method is useful for the determination of the composition of polysaccharides and their methyl derivatives.
45,381 citations
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TL;DR: Biology of microorganisms, Biology of micro organisms, مرکز فناوری اطلاعات و اصاع رسانی, کδاوρزی
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2,240 citations
TL;DR: The biological production of hydrogen from the fermentation of different substrates was examined in batch tests using heat-shocked mixed cultures with two techniques: an intermittent pressure release method (Owen method) and a continuous gas release method using a bubble measurement device (respirometric method).
Abstract: The biological production of hydrogen from the fermentation of different substrates was examined in batch tests using heat-shocked mixed cultures with two techniques: an intermittent pressure release method (Owen method) and a continuous gas release method using a bubble measurement device (respirometric method). Under otherwise identical conditions, the respirometric method resulted in the production of 43% more hydrogen gas from glucose than the Owen method. The lower conversion of glucose to hydrogen using the Owen protocol may have been produced by repression of hydrogenase activity from high partial pressures in the gastight bottles, but this could not be proven using a thermodynamic/rate inhibition analysis. In the respirometric method, total pressure in the headspace never exceeded ambient pressure, and hydrogen typically composed as much as 62% of the headspace gas. High conversion efficiencies were consistently obtained with heat-shocked soils taken at different times and those stored for up to a month. Hydrogen gas composition was consistently in the range of 60-64% for glucose-grown cultures during logarithmic growth but declined in stationary cultures. Overall, hydrogen conversion efficiencies for glucose cultures were 23% based on the assumption of a maximum of 4 mol of hydrogen/ mol of glucose. Hydrogen conversion efficiencies were similar for sucrose (23%) and somewhat lower for molasses (15%) but were much lower for lactate (0.50%) and cellulose (0.075%).
538 citations
TL;DR: Whether one considers the “light side” or the ‘dark side’ of hydrogen production, significant progress is being made, according to a new report from the European Commission.
Abstract: Whether one considers the “light side” or the “dark side” of hydrogen production, significant progress is being made.
463 citations
TL;DR: The tolerance of C. pasteurianum to Glycerol was remarkably high; growth was not inhibited by glycerol concentrations up to 17% (wt/vol), and increasing glycerl concentrations favored the production of 1,3-propanediol.
Abstract: The effect of pH, growth rate, phosphate and iron limitation, carbon monoxide, and carbon source on product formation by Clostridium pasteurianum was determined. Under phosphate limitation, glucose was fermented almost exclusively to acetate and butyrate independently of the pH and growth rate. Iron limitation caused lactate production (38 mol/100 mol) from glucose in batch and continuous culture. At 15% (vol/vol) carbon monoxide in the atmosphere, glucose was fermented to ethanol (24 mol/100 mol), lactate (32 mol/100 mol), and butanol (36 mol/100 mol) in addition to the usual products, acetate (38 mol/100 mol) and butyrate (17 mol/100 mol). During glycerol fermentation, a completely different product pattern was found. In continuous culture under phosphate limitation, acetate and butyrate were produced only in trace amounts, whereas ethanol (30 mol/100 mol), butanol (18 mol/100 mol), and 1,3-propanediol (18 mol/100 mol) were the major products. Under iron limitation, the ratio of these products could be changed in favor of 1,3-propanediol (34 mol/100 mol). In addition, lactate was produced in significant amounts (25 mol/100 mol). The tolerance of C. pasteurianum to glycerol was remarkably high; growth was not inhibited by glycerol concentrations up to 17% (wt/vol). Increasing glycerol concentrations favored the production of 1,3-propanediol.
441 citations