Hydrogen production from sludge of poultry slaughterhouse wastewater treatment plant pretreated with microwave

This study aims to produce hydrogen from sludge of poultry slaughterhouse wastewater treatment plant (5% total solid) by anaerobic batch fermentation with Enterobactor aerogenes or mixed cultures from hot spring sediment as the inoculums. Sludge was heated in microwave at 850 W for 3 min. Results indicated that a soluble chemical oxygen demand (sCOD) of pretreated sludge was higher than that of raw sludge. Pretreated sludge inoculated with E. aerogenes and supplemented with the Endo nutrient had a higher hydrogen yield (12.77 mL H₂/g tCOD) than the raw sludge (0.18 mL H₂/g tCOD). When considered the hydrogen yield, the optimum initial pH for hydrogen production from microwave pretreated sludge was 5.5 giving the maximum value of 12.77 mL H₂/g tCOD. However, when considered the hydrogen production rate (R_m), the optimum pH for hydrogen production would be 9.0 with the maximum R_m of 22.80 mL H₂/L sludge·h.     

Performance of batch solid state fermentation for hydrogen production using ground wheat residue

Ground wheat (21 g) was subjected to batch solid state dark fermentation for bio-hydrogen production. Clostridium acetobutylicum (B-527) was used as the culture of dark fermentation bacteria at mesophilic conditions. Effects of moisture content on the rate and yield of bio-hydrogen formation were investigated. The highest CHF (1222 ml), hydrogen yield (63 ml H₂ g^?1 starch), formation rate (10.64 ml H₂ g^?1 starch h^?1) and specific hydrogen formation rate (0.28 ml H₂ g^?1 biomass h^?1) were obtained with a moisture content of 80%. Nearly complete starch hydrolysis and glucose fermentation were achieved with more than 80% moisture content and the highest substrate conversion rate (21.9 mg L^?1 h^?1) was obtained with 90% moisture content at batch solid state fermentation producing volatile fatty acids (VFA) and H₂.     

微生物发酵制备油脂的研究

综述了国内外微生物油脂发展和研究的现状,分析了碳源、氮源、温度、pH值、培养时间、通气量等对菌体生长及油脂积累的影响,阐述了微生物油脂生产工艺中的一些关键环节,包括菌体的预处理、微生物油脂的提取、微生物油脂的精炼和分析等,展望了微生物油脂未来的发展方向和在生物柴油制备中的应用前景.     

Effluents with soluble metabolites generated from acidogenic and methanogenic processes as substrate for additional hydrogen production through photo-biological process

The feasibility of utilizing effluents generated from acidogenic [producing biohydrogen (H₂)] and methanogenic [producing methane] processes was studied for additional H₂ production by terminally integrating with photo-biological process employing enriched mixed culture. Experimental data has depicted enhanced process efficiency with respect to additional H₂ production and substrate degradation through photo-biological process. However, the efficiency was found to depend on the process used in the first stage along with nature and composition of the substrate. Acidogenic process in the first stage had more positive influence on photo-biological H₂ production [synthetic wastewater – 14.40 mol/Kg COD_R and 15.16 mol/Kg COD_R (with vitamins); dairy wastewater – 13.29 mol/Kg COD_R and 13.70 mol/Kg COD_R (with vitamins)] over the corresponding methanogenic process. Effluent generated from acidogenic treatment of dairy wastewater yielded high substrate degradation rate (SDR) [1.20 Kg COD/m³ day and 1.34 Kg COD/m³ day (vitamins)] followed by synthetic wastewater [0.92 Kg COD/m³ day and 1.05 Kg COD/m³ day (vitamins)]. Among the studied experimental variations chemical wastewater evidenced poor H₂ production and SDR. Vitamin solution showed positive influence on both H₂ production and wastewater treatment irrespective of the experimental variations studied.     

Electricity production by integration of acidogenic fermentation of fruit juice wastewater and fuel cells

In this work, the potential application of bio-hydrogen in a fuel cell was studied. To do that an activated sludge was acclimatized to an acidogenic culture producing bio-hydrogen. Once reached the steady state, several batch experiments were carried out by feeding a synthetic fruit juice industry wastewater to the acidogenic culture. The bio-hydrogen yield obtained when this synthetic fruit juice industry wastewater was fed was 1403 mol H₂/mol hexose and the hydrogen percent in gas phase was 57%. In an average size fruit juice industry, this bio-hydrogen yield corresponds to a bio-hydrogen production of about 6000 mol H₂/d. In the subsequent stage, a synthetic bio-hydrogen stream with the same composition of the cleaned bio-hydrogen obtained in the acidogenic fermentation was fed as fuel in a Fuel Cell, obtaining very similar power and polarization curves than that obtained when feeding pure hydrogen, differences lower than 10%. These results showed that the hydrogen stream obtained by the acidogenic fermentation could be used to produce electricity in a high temperature PEMFC.     

Influence of pH, temperature and volatile fatty acids on hydrogen production by acidogenic fermentation

The aim of this work was to study the influence of pH and temperature on acidogenic fermentation and bio-hydrogen production. A centered factorial design was generated with respect to pH (4-6 units) and temperature (26-40 °C), and these conditions were used in batch experiments. Biomass cultivation was conducted in a sequential batch reactor (SBR). A mixed-acidogenic culture enriched from activated sludge and fed with a 9 g/l glucose solution was used in the experiments. At low pH values, hydrogen production was favored when the temperatures were low, a result contrary to those described in literature. Working at higher temperatures reduced the length of the lag phase. Additionally, the hydrogen production rate was increased at these temperatures. These opposite trends indicated that an inhibition effect occurred during the experiment. Hydrogen production was studied by using a response surface methodology, being the highest hydrogen production occurred at pH 5.4 and 26 °C. Regarding to the relationship between the hydrogen and acid production, the hydrogen produced per unit of acetate produced increased as the pH increased. On the other hand, hydrogen produced from other acids was constant and similar to theoretical yields. These values of hydrogen produced per unit of acid produced allowed to estimate the experimental hydrogen production. This result indicated that pH was the most important factor in acidogenic fermentation.     

A sequential process of anaerobic solid-state fermentation followed by dark fermentation for bio-hydrogen production from Chlorella sp.

Microalgal biomass has recently been one of the most widely studied feedstocks for bio-hydrogen production, owing to its richness in fermentable components, e.g. polysaccharides and proteins, and high biomass productivity. In this study, biomass of microalga Chlorella sp. TISTR 8411 was converted to hydrogen through a sequential process consisting of an anaerobic solid-state fermentation (ASSF) followed by a dark fermentation. The microalga was grown photoautothrophically in 80-L rectangular glass tanks and then scaled-up to a 240-L open pond for the production of biomass. The highest biomass concentration attained was 4.45 g L⁻¹. The biomass was harvested with over 90% flocculation efficiency at pH 11.5 and a biomass concentration of 2.6 g/L. The sequential process gave a total hydrogen yield (HY) of 16.2 mL/g-volatile-solid (VS), of which 11.6 mL/g-VS was from ASSF. The high HY obtained from the ASSF indicated that it was effective and could be integrated with a conventional hydrogen production process to improve energy recovery from biomass.     

Light fermentation of dark fermentation effluent for bio-hydrogen production by different Rhodobacter species at different initial volatile fatty acid (VFA) concentrations

Three different Rhodobacter sphaeroides (RS) strains (RS–NRRL, RS–DSMZ and RS–RV) and their combinations were used for light fermentation of dark fermentation effluent of ground wheat containing volatile fatty acids (VFA). In terms of cumulative hydrogen formation, RS–NRRL performed better than the other two strains producing 48 ml H₂ in 180 h. However, RS–RV resulted in the highest hydrogen yield of 250 ml H₂ g⁻¹ TVFA. Specific hydrogen production rate (SHPR) with the RS–NRRL was also better in comparison to the others (13.8 ml H₂ g⁻¹ biomass h⁻¹). When combinations of those three strains were used, RS–RV + RS–DSMZ resulted in the highest cumulative hydrogen formation (90 ml H₂ in 330 h). However, hydrogen yield (693 ml H₂ g⁻¹ TVFA) and SHPR (12.1 ml H₂ g⁻¹ biomass h⁻¹) were higher with the combination of the three different strains. On the basis of Gompertz equation coefficients mixed culture of the three different strains gave the highest cumulative hydrogen and formation rate probably due to synergistic interaction among the strains. The effects of initial TVFA and NH₄–N concentrations on hydrogen formation were investigated for the mixed culture of the three strains. The optimum TVFA and NH₄–N concentrations maximizing the hydrogen formation were determined as 2350 and 47 mg L⁻¹, respectively.     

柠檬酸盐对有机污水厌氧发酵产沼气的影响

将污水接种活性污泥后在厌氧、中温(37℃)和120 r/min条件下进行批培养,添加浓度为1.0 g/l柠檬酸钠时的产气量和产沼气对所消耗的葡萄糖的得率系数分别比对照提高38.5%和61.9%;但是糖平均消耗速率和最终pH值分别比对照下降了12.5%和7.1%.厌氧培养过程中的挥发性脂肪酸(VFA)变化趋势差异明显,对照VFA浓度在24 h达到最大值,此时其浓度是添加柠檬酸钠组VFA浓度的82%,之后逐渐降低.但是,添加组VFA含量随着培养的进行逐渐增大,VFA的平均积累速率和VFA对葡萄糖的得率系数分别比对照增加了232%和279%.柠檬酸钠的添加促进了葡萄糖向VFA的代谢合成,为甲烷合成提供了充足的底物,提高了葡萄糖转化甲烷的效率和沼气总量.     

Effect of fermentation conditions on biohydrogen production from lipid-rich food material

Among the basic components of organic materials, such as carbohydrate, protein, and lipid, the hydrogen yield of carbohydrate fermentation has been reported to be significantly higher than that of lipid. This study used lard as a model organic matter for lipid and investigated its H₂ production potential in batch anaerobic fermentation experiments under various combinations of stirring and CO₂-scavenging conditions. A significant increase in the hydrogen yield was observed in both CO₂-scavenging and stirring conditions; the CO₂-scavenging condition yield was 2.9 times higher than the stirring condition (116.7 and 40.3 mL H₂/g volatile solid [VS], respectively), which was much greater than reported previously. A maximal hydrogen yield of 185.8 mL H₂/g VS was obtained in the presence of both CO₂-scavenging and stirring, and the H₂ content of the total biogas was as high as 99% (v/v). In addition, there was less H₂ and more CH₄ production in the absence of CO₂-scavenging and/or stirring, which suggests that the consumption of H₂ and CO₂ for methanogenesis was the major mechanism of the poor hydrogen yield from lipid. The volatile fatty acids in all the tests consisted primarily of valeric (47.2–54.9%) and propionic acids (26.6–30.3%), and higher concentrations of these acids remained in the fermentation liquid without CO₂ removal. These results suggest that lipid-rich food waste is a potential source for H₂ production if the fermentation process is optimized to minimize the partial pressure of CO₂ and H₂ and restrain the activities of H₂-consuming bacteria.     

Assessing the impact of palmitic,myristic and lauric acids on hydrogen production from glucose fermentation by mixed anaerobic granular cultures

The effects of lauric (LUA), myristic (MA), palmitic (PA), and a mixture of myristic:palmitic (MA:PA) acids on hydrogen (H₂) production from glucose degradation using anaerobic mixed cultures were assessed at 37 °C with an initial pH set at 5.0 and 7.131 mM of each acid. The maximum H₂ yield (2.53 ± 0.18 mol mol⁻¹ glucose) was observed in cultures treated with PA. A principal component analysis (PCA) of the by-products and the microbial population data sets detected similarities between the controls and PA treated cultures; however, differences were observed between the controls and PA treated cultures in comparison to the MA and LUA treated cultures. The flux balance analysis (FBA) showed that PA decreased the quantity of H₂ consumed via homoacetogenesis compared to the other LCFAs. The control culture was dominated by Thermoanaerovibrio acidaminovorans (60%), Geobacillus sp. and Eubacterium sp. (28%), while Clostridium sp. was less than 1%. Treatment with PA, MA, MA:PA, or LUA increased the H₂ producers (Clostridium sp. and Bacillus sp.) population by approximately 48, 67, 86, and 86%, respectively.     

Kinetic and performance study of a batch two-phase anaerobic digestion of fruit and vegetable wastes

Anaerobic digestion of a simulated organic fraction of the waste of a central market selling fruit and vegetables was carried out in two-phase digesters in the mesophilic range of temperatures. Batch digestion was prolonged until no biogas was produced (33 days). With digested pig manure as inoculum, maximum biogas production was obtained around day 10, and within 3 weeks the digestion was almost complete. A kinetic analysis was carried out using first-order, Monod and Chen-Hashimoto models. The Chen-Hashimoto model represents the best fit, whereas a first-order model was not consistent with the experimental results.     

Comparison of bio-hydrogen production from hydrolyzed wheat starch by mesophilic and thermophilic dark fermentation

Hydrogen gas production potentials of acid-hydrolyzed and boiled ground wheat were compared in batch dark fermentations under mesophilic (37 °C) and thermophilic (55 °C) conditions. Heat-treated anaerobic sludge was used as the inoculum and the hydrolyzed ground wheat was supplemented by other nutrients. The highest cumulative hydrogen gas production (752 ml) was obtained from the acid-hydrolyzed ground wheat starch at 55 °C and the lowest (112 ml) was with the boiled wheat starch within 10 days. The highest rate of hydrogen gas formation (7.42 ml H₂ h⁻¹) was obtained with the acid-hydrolyzed and the lowest (1.12 ml H₂ h⁻¹) with the boiled wheat at 55 °C. The highest hydrogen gas yield (333 ml H₂ g⁻¹ total sugar or 2.40 mol H₂ mol⁻¹ glucose) and final total volatile fatty acid (TVFA) concentration (10.08 g L⁻¹) were also obtained with the acid-hydrolyzed wheat under thermophilic conditions (55 °C). Dark fermentation of acid-hydrolyzed ground wheat under thermophilic conditions (55 °C) was proven to be more beneficial as compared to mesophilic or thermophilic fermentation of boiled (partially hydrolyzed) wheat starch.     

Expression of different types of [FeFe]-hydrogenase genes in bacteria isolated from a population of a bio-hydrogen pilot-scale plant

[FeFe]-hydrogenases are the enzymes responsible for high yield H₂ production during dark fermentation in bio-hydrogen production plants. The culturable bacterial population present in a pilot-scale plant efficiently producing H₂ from waste materials was isolated, classified and identified by means of 16S rDNA gene analysis. The culturable part of the mixed population consists of nine bacterial species that include non-hydrogen producers (Lactobacillus, Enterococcus and Staphylococcus) and several Clostridium that are directly responsible for H₂ production.     

Simultaneous saccharification and fermentation of cellulose for bio-hydrogen production by anaerobic mixed cultures in elephant dung

The objective of this study was to optimize the culture conditions for simultaneous saccharification and fermentation (SSF) of cellulose for bio-hydrogen production by anaerobic mixed cultures in elephant dung under thermophilic temperature. Carboxymethyl cellulose (CMC) was used as the model substrate. The investigated parameters included initial pH, temperature and substrate concentration. The experimental results showed that maximum hydrogen yield (HY) and hydrogen production rate (HPR) of 7.22 ± 0.62 mmol H₂/g CMC_added and 73.4 ± 3.8 mL H₂/L h, respectively, were achieved at an initial pH of 7.0, temperature of 55 °C and CMC concentration of 0.25 g/L. The optimum conditions were then used to produce hydrogen from the cellulose fraction of sugarcane bagasse (SCB) at a concentration of 0.40 g/L (equivalent to 0.25 g/L cellulose) in which an HY of 7.10 ± 3.22 mmol H₂/g cellulose_added. The pre-dominant hydrogen producers analyzed by polymerase chain reaction-denaturing gel gradient electrophoresis (PCR-DGGE) were Thermoanaerobacterium thermosaccharolyticum and Clostridium sp. The lower HY obtained when the cellulose fraction of SCB was used as the substrate might be due to the presence of lignin in the SCB as well as the presence of Lactobacillus parabuchneri and Lactobacillus rhamnosus in the hydrogen fermentation broth.     

Dark fermentative hydrogen production from sucrose and molasses

There are many factors affecting the dark fermentative hydrogen production. The interaction of these factors, that is, their combined effects, should be investigated for better design of the systems with stable and higher hydrogen yields. This study aimed to investigate the combined effects of initial substrate, pH, and biomass (or initial substrate to biomass) values on hydrogen production from sucrose and sugar‐beet molasses. Therefore, optimum initial chemical oxygen demand (COD), pH, and volatile suspended solids (VSS) or initial substrate to biomass (VSS) ratio (S/X_o) values leading to the highest dark fermentative hydrogen production were investigated in batch reactors. An experimental design approach (response surface methodology) was used. Results revealed that when sucrose was the substrate, maximum hydrogen production yield (HY) of 2.3 mol H₂/mol sucrose_added was obtained at initial pH of 7 and COD of 10 g/L. Initial S/X_o values studied (4–20 g COD/g VSS) had no effect on HY, while the initial pH was found as the parameter mostly affecting both HY and hydrogen production rate (HPR). When substrate was molasses, initial COD concentration was the only variable affecting HY and HPR. Maximum of both was achieved at 10 g/L initial COD. Initial VSS values studied (2.5–7.5 g/L) had no effect on HPR and HY. This study also indicated that molasses leads to homoacetogenesis for potentially containing intrinsic microorganism and/or natural constituents; thus, sucrose is more advantageous for hydrogen production via fermentation. Homoacetogenesis should be prevented for effective optimization via response surface methodology, if substrate is a natural carbon source potential to have intrinsic microorganisms. Copyright © 2017 John Wiley & Sons, Ltd.     

Transesterification of oil extracted from freshwater algae for biodiesel production

Currently, energy crisis is a burning issue throughout the world, particularly in underdeveloped countries like Pakistan where the demand of conventional fuels has been increasing day by day. The main objective of this project was the production of biodiesel from Algae. Samples of freshwater were collected. The Chlorella species produced 6.26 g oil from 38.23 g of dry weight and the Oedogonium species produced 8.07 g of oil from 38.23 g of dried weight. The biomass obtained after oil extraction was 31.97 g from chlorella species and 30.16 g from Oedogonium species. The fatty acids that were displayed by a gas chromatographic machine in chlorella species were capric acid, nanoic acid, arachidonic acid, behenic acid, and erucic acid and in oedogonium species they were capric acid, butyric acid, behenic acid, luric acid, tridecanoic acid, and arachidonic acid.     

Green hythane production from food waste: Integration of dark-fermentation and methanogenic process towards biogas up-gradation

This study presents an integration of acidogenesis (dark-fermentation) and methanogenesis for green hythane/biohythane production from food waste in two stages (S–I and S-II) and phases (P–I and P-II) of operational variations. The regulatory influence of biocatalyst and redox environment on anaerobic fermentation was evaluated  through a rapid protocol in the context of biogas up-gradation with reference to bio-hydrogen (bio-H₂), biomethane (CH₄), bio-hythane (H₂+CH₄) and their composition (H₂/(H₂+CH₄)) as major markers. Bioreactors with two different parent cultures (heat-shock pretreated and untreated) were operated at pH 6 and 7 in two phases to overcome the impediment of single-phase operation aiming for maximum energy recovery from the untreated substrate of P–I. Integration of S–I with S-II was beneficial to achieve 1.22 times higher cumulative bio-hythane production (4.25 L) compared to S–I (3.47 L) condition alone. The bio-hythane composition mimics the H₂ enriched CNG (H-CNG) and showed the potential to be implemented for biogas up-gradation as a tool.     

Biohydrogen and biomethane production from cassava wastewater in a two-stage anaerobic sequencing batch biofilm reactor

The objective of the present study was to determine the energetic potential from cassava starch wastewater in a two-stage system (BioH₂ + BioCH₄) composed by anaerobic sequencing batch biofilm reactors (AnSBBR). Included in this general objective, the behavior of the methanogenic AnSBBR regarding organic matter removal and biomethane production will be investigated. The acidogenic AnSBBR was operated with organic loading rate (OLR) of 14 gCarb.L⁻¹.d⁻¹, influent concentration of 5 gCarb.L⁻¹ and cycle time of 4 h. The methanogenic AnSBBR was submitted to OLR increase (3.7–12 gCOD.L⁻¹.d⁻¹), provided by arrangements between influent concentration (2.8; 4.0 and 6.0 gCOD.L⁻¹) and cycle time (6; 8 and 12 h). For the evaluated condition, the acidogenic reactor presented productivity of 0.7 LH₂.L⁻¹.d⁻¹ and yield of 1.1 molH₂.kg⁻¹Carb. The methanogenic reactor presented stable methane production (%CH₄ > 78) during the 260-days operating period. The maximum methane productivity (2.71 LCH₄.L⁻¹.d⁻¹) and yield (0.263 LCH₄.g⁻¹COD) were obtained at OLR of 12 gCOD.L⁻¹.d⁻¹ and cycle time of 6 h. The estimated energy production rate in the two-stage system (BioH₂ + BioCH₄) was 105.2 kJ.L⁻¹.d⁻¹.