Simultaneous Biohydrogen Production Research Articles

Investigating the efficiency of a two-stage anaerobic-aerobic process for the treatment of confectionery industry wastewaters with simultaneous production of biohydrogen and polyhydroxyalkanoates.

The scope of the current study was to investigate the efficiency of a two-stage anaerobic-aerobic process for the simultaneous treatment and valorization of selective wastewater streams from a confectionary industry. The specific wastewater (confectionary industry wastewater, CIW) was a mixture of the rinsing eluting during washing of the cauldrons in which jellies and syrups were produced, and contained mainly readily fermentable sugars, being thus of high organic load. The first stage of the process was the dark fermentation (DF) of the CIW in continuous, attached-biomass systems, in which the effect on hydrogen yields and distribution of metabolites were studied for different packing materials (ceramic or plastic), hydraulic retention times, HRTs (12 h–30 h) and feed substrate concentration (20 g COD/L- 50 g COD/L). In the second stage, the effectiveness of the aerobic treatment of the DF effluents was evaluated in terms of the reduction of the organic load and the production of polyhydroxyalkanoates (PHAs) through an enriched mixed microbial culture (MMC). The MMC was developed in a continuous draw and fill system, in which the accumulation potential of PHAs was studied. It was shown that the hydrogen production rates decreased for increasing substrate concentration and HRTs, with a maximum of 12.70 ± 0.35 m3 H2/m3 initial CIW achieved for the lowest HRT and feed concentration and using ceramic beads as packing material. Butyrate, acetate and lactate were the main metabolites generated in all cases, in different ratios. The distribution of metabolites during DF was shown to highly affect the efficiency of the second process in terms of both the reduction of organic load and the PHAs yields. The highest removal of organic load achieved after 48 h of aerobic treatment was 84.0 ± 0.9 %, whereas the maximum PHAs yield was 21.46 ± 0.13 kg PHAs/m3 initial CIW.

Simultaneous Production of Biohydrogen (bioH2) and Poly-Hydroxy-Alkanoates (PHAs) by a Photoheterotrophic Consortium Bioaugmented with Syntrophomonas wolfei

Mixed cultures represent better alternatives to ferment organic waste and dark fermentation products in anerobic conditions because the microbial associations contribute to electron transfer mechanisms and combine metabolic possibilities. The understanding of the microbial interactions in natural and synthetic consortia and the strategies to improve the performance of the processes by bioaugmentation provide insight into the physiology and ecology of the mixed cultures used for biotechnological purposes. Here, synthetic microbial communities were built from three hydrogen (bioH2) and poly-hydroxy-alkanoates (PHA) producers, Clostridium pasteurianum, Rhodopseudomonas palustris and Syntrophomonas wolfei, and a photoheterotrophic mixed consortium C4, and their performance was evaluated during photofermentation. Higher hydrogen volumetric production rates (H2VPR) were determined with the consortia (28–40 mL/Lh) as compared with individual strains (20–27 mL/Lh). The designed consortia reached the highest bioH2 and PHA productions of 44.3 mmol and 50.46% and produced both metabolites simultaneously using dark fermentation effluents composed of a mixture of lactic, butyric, acetic, and propionic acids. When the mixed culture C4 was bioaugmented with S. wolfei, the bioH2 and PHA production reached 32 mmol and 50%, respectively. Overall, the consumption of organic acids was above 50%, which accounted up to 55% of total chemical oxygen demand (COD) removed. Increased bioH2 was observed in the condition when S. wolfei was added as the bioaugmentation agent, reaching up to 562 mL of H2 produced per gram of COD. The enhanced production of bioH2 and PHA can be explained by the metabolic interaction between the three selected strains, which likely include thermodynamic equilibrium, the assimilation of organic acids via beta-oxidation, and the production of bioH2 using a proton driving force derived from reduced menaquinone or via electron bifurcation.

Simultaneous production of renewable biohydrogen, biobutanol and biopolymer from phytogenic CoNPs-assisted Clostridial fermentation for sustainable energy and environment

Considering the environmental impacts, rapid fossil fuel depletion and production costs, sustainable production of clean biofuels from alternative sources is required to meet the increasing demand for energy while avoiding environmental pollution. In this study, phytogenic cobalt nanoparticles (CoNPs)-assisted dark fermentation process was developed for the simultaneous production of biohydrogen, biobutanol and biopolymer from glucose using Clostridium acetobutylicum NCIM 2337. The maximum biohydrogen yield of 2.89 mol H2/mol glucose was achieved at 1.5 mg of CoNPs, which is 1.6 folds higher than that of the control experiment. The high level of soluble metabolites, specifically acetate and butyrate, confirmed the production of biohydrogen through acetate/butyrate pathways. The modified Gompertz model fitted well with experimental results of CoNPs-assisted biohydrogen production. The CoNPs could act as an electron carrier in intracellular metabolism to enhance the activity of ferredoxin and hydrogenase enzymes, thus improving biohydrogen production. Furthermore, biobutanol and biopolymer yields of 975 ± 2.5 mg/L and 1182 ± 1.4 mg/L were achieved, with 2.0 mg and 2.5 mg of CoNP, respectively, which were 1.27 and 1.19 folds higher than the control values. Hence, the inclusion of CoNPs in the fermentation medium seems to be a promising technique for the enhanced simultaneous production of biohydrogen, biobutanol and biopolymer. The environmental perspectives of the obtained renewable biohydrogen, biobutanol and biopolymer are also discussed.

Simultaneous biohydrogen production from dark fermentation of duckweed and waste utilization for microalgal lipid production

A cost-effective and environmentally friendly method for biofuel production was developed, by utilizing duckweed as feedstock for biohydrogen production through dark fermentation and simultaneously using the fermentative waste to produce microalgal lipids. The results suggested that acid hydrolysis (1% H2SO4) was more suitable for the pretreatment of duckweed biomass. Maximum hydrogen production of 169.30 mL g−1 dry weight was determined under a temperature of 35 °C and an initial pH of 7.0. After the dark fermentation, the volatile fatty acids (VFAs) including acetate and butyrate, were detected in the waste, with concentration determined as 1.04 g L−1 and 1.52 g L−1, respectively. During the mixotrophic cultivation of Chlorella sacchrarophila FACHB-4 using waste as feedstock, the maximum microalgal biomass and the lipid productions were about 2.8 and 33 times higher with respect to the autotrophic growth. The simultaneous biohydrogen production and waste utilization method provided a green strategy for biofuel production.

Integrated dark-photo fermentative hydrogen production from synthetic gelatinaceous wastewater via cost-effective hybrid reactor at ambient temperature

The industrial application of anaerobic digestion to treat protein-rich wastewater (e.g., gelatin) is promising; however, inhibitory effects such as released excess ammonia on methanogens causes limitations. This study investigated the potential of sequential dark and photo-fermentation for wastewater treatment and simultaneous bio-hydrogen production (as energy source). To this end, a new configuration, namely dark-photo circular baffled reactor (DP-CBR) was introduced and operated at ambient temperature (21 ± 10 °C). The reactor was composed of four identical compartments, where fluorescent tubes were installed to the last two compartments, i.e., C1-C2 (dark) and C3-C4 (photo). The long-term impact of main operational parameters (i.e., hydraulic retention time [HRT] of 6, 12 and 24 h at initial pH of 5.5 and 6.5) was assessed. Maximum hydrogen yield (HY) of 0.4 L/gCOD, COD removal of 82%, and organic-N removal of 95% were obtained at HRT of 24 h and initial pH of 6.5. Increasing HRT was found to maintain the reactor efficiency at ambient temperature. Lowering initial pH to 5.5 deteriorated the dark-treatment at C1 and C2, resulting in lower local HY and ammonification efficiency. Further, the results confirmed that higher HY was achieved in the photo-fermentation, as the protein hydrolysis was mainly achieved in the dark-fermentation. The residual free ammonia (<0.36 mg/L), at all examined conditions, was below the inhibition limit of photosynthetic bacteria. The microbial community analysis revealed the development of purple non-sulfur bacterial family Rhodospirillaceae at C3. The economic efficiency of DP-CBR was also evaluated by considering the capital cost, annual costs (i.e., lightning, pumping, nutrients, and gas purification), and revenues (i.e., bio-hydrogen energy and removal add-value). Overall, the techno-economic assessment of DP-CBR performance emphasizes its feasibility in affordable removal of organics and bioenergy recovery when dealing with gelatin-rich wastewater.

Simultaneous biohydrogen production with distillery wastewater treatment using modified microbial electrolysis cell

The objective of the present study was to construct a compact retrofit design of Microbial Electrolysis Cell (MEC) within an anaerobic digester. In this design, the cathode chamber is inserted in the anodic chamber for compactness, improved hydrogen production and wastewater treatment efficiency. The performance of the new design is compared with that of a conventional (dual chamber) MEC. A cumulative hydrogen of 40.05 ± 0.5 mL and 30.12 ± 0.5 mL were produced at the current density of 811.7 ± 20 and 908.3 ± 25 mA/m2 respectively for conventional and modified MEC system. The cathodic hydrogen recovery (CHR) defined as the recovery of electrons as hydrogen which was observed a maximum of 46.5 ± 0.8 and 38.8 ± 0.5% in conventional and modified MEC. The Coulombic efficiency (CE) defined as the recovery of total electrons in acetate as current was observed as 17.25 ± 0.15 and 16.82 ± 0.1% for conventional and modified MEC. In addition, the wastewater COD removal efficiency was observed to be 77.5 ± 1.0% and 75.6 ± 1.5 in 70 h for conventional and modified MEC designs. As shown in the work below, the modified compact design worked effectively to produce hydrogen under different COD concentrations; anolyte and catholyte concentrations; and applied potentials. Thus the modified compact MEC which is also a retrofit to an existing anaerobic digester can extend the use of anaerobic digesters and improve their economics in waste water treatment.

Phytofabrication of bimetallic Co–Ni nanoparticles using Boerhavia diffusa leaf extract: analysis of phytocompounds and application for simultaneous production of biohydrogen and bioethanol

Boerhavia diffusa mediated synthesis of bimetallic cobalt—nickel nanoparticles (Co–Ni NPs) was developed using optimized process parameters including pH, precursor (mixture of Co and Ni salts) concentration (mM) and volume ratio of precursor solution to leaf extract. Foureir Transform Infra Red spectroscopy (FTIR) studies revealed that the protein, phenolic and alcoholic compounds were mainly accountable for the formation and stabilization of Co–Ni NPs. Gas Chromatograpgy—Mass Spectrometric (GC-MS) results showed that the presence of alcoholic (1,3-dioxolane-2-methanol), phenolic (phenol,2-(1,1-dimethylethyl)-4-(1-methyl-1-phenylethyl)-, ketone (4H-1-benzopyran-4-one, 2-(2, 6-dimethoxyphenyl)-5, 6-dimethoxy-), ester (9-octadecenoic acid, (2-phenyl-1,3-dioxolan-4-yl) methyl ester, cis-) and oxygenated monoterpenes (1-(2-methoxyethoxy)-2-methyl-2-propanol, methyl ether) were mainly responded for the formation and stabilization of bimetallic Co–Ni NPs. High Resolution—Transmission Electron Microscopic (HR-TEM) images exhibit that the size of the Co–Ni NPs was observed to be less than 10 nm. The effect of the Co–Ni NPs as cofactor on simultaneous production of biohydrogen and bioethanol from glucose using Citrobacter freundii NCIM No. 2489 was investigated at different concentrations from 250 to 1250 μg l−1. The yields of biohydrogen and bioethanol were 0.26 mol H2/mol glucose and 3307 ± 238 mg l−1, respectively at 1000 μg l−1 Co–Ni NPs. The Co–Ni NPs supplemented fermentation system yielded high production of bioethanol and low production of biohydrogen. The volatile fatty acids (VFAs) in the Co–Ni NPs supplemented system were also noticed in the following order: propionate > butyrate > acetate.

Pretreatments Testing of High Biodiversity Inocula with Simultaneous Biohydrogen Production and Wastewater Treatment

Hydrogen represents a renewable energy resource and it is an ideal alternative to fossil fuels since it does not contribute to the greenhouse effect. In the present study it has been proposed to develop an experimental model to test and compare fermentative capacity of waste water with biohydrogen production for two high biodiversity heterotrophic microbial inocula. All the pretreatment methods tested yielded good results, but heat and acid pretreatment had the best results. These observations open the way for the development and application of new technologies using microbial consortia specially developed to serve the dual role of biological waste water treatment and the production of a renewable energy in the form of biohydrogen.

Simultaneous biohydrogen production and purification in a double-membrane bioreactor system

In this work the establishment of a double-membrane bioreactor was aimed. Initially, a continuous hydrogen fermenter was coupled with a commercial Kubota® microfiltration membrane module and the production performance of the cell-retentive design was evaluated under various hydraulic retention times. As a result, it has been observed that altering HRT influenced the rejection feature of the microfiltration module while had an inverse effect on hydrogen productivity and yield, since shortened HRTs were accompanied by gradually decreasing H2 yields (HY) and progressively increasing volumetric H2 production rates (HPR). The highest HY and HPR were achieved as 1.13 mol H2/mol glucose and 0.24 mol H2/L-d, respectively. Furthermore, a Permselect® (PDMS) gas separation membrane was installed to the anaerobic membrane bioreactor and its ability to separate hydrogen from the raw fermentation gaseous mixture was assessed. The highest purity hydrogen obtained in one-step purification by the PDMS module was 67.3 vol.%, which exceeds 30% enrichment efficiency considering 51.3 vol.% H2 in the feed gas. Hence, it could be concluded that the poly(dimethyl siloxane) membrane has potential to attractively concentrate biohydrogen from fermenter off-gas and may be used for in-situ product recovery.

Malt plant wastewater treatment and biohydrogen production

The developed technology of treatment of wastewater of malt factory from phosphates in the system of anaerobic-aerobic bioreactors with simultaneous biohydrogen production in bioelectrochemical system is given in the paper.The biotechnological scheme contains the wastewater treatment blocks for the reduction of concentration of suspended substances, COD (chemical oxygen demand), phosphates and other environmental pollutants, and also the bioelectrochemical system of biohydrogen production.The biotechnology, developed and approved in actual production conditions, provides high efficiency of wastewater treatment of malt factory from organic pollutants according to COD - 94-95 % at the values of COD indicator at the input up to 2000 mg/dm3, from phosphates up to 90 % at the initial concentration of 25 mg/dm3.The application of bioelectrochemical method of hydrogen synthesis allows obtaining biogas consisting of 70 % of molecular hydrogen, and also provides the removal of organic pollution from wastewaters with the efficiency up to 98 %.

Simultaneous production of bio-hydrogen and methane from soybean protein processing wastewater treatment using anaerobic baffled reactor (ABR)

Bio-hydrogen (H2) and methane (CH4) co-production from soybean protein processing wastewater (SPPW) was examined using a four-compartment anaerobic baffled reactor (ABR) with the active reactor volume (34 L) under continuous flow condition in this present study. At steady state, the ABR achieved H2 yields of 25.67 L/d, specific hydrogen production rate of anaerobic activated sludge was 0.28 L/g MLVSS d, CH4 yields of 13.89 L/d, and chemical oxygen demand (COD) removal of 95% when operated at the organic loading rate of 1.9–2.6 kg COD/m3 d, hydraulic retention time of 48 h, and temperature of (35 ± 1) °C, respectively. The results showed that the niches of the bio-hydrogen-producing phase and the methane-producing phase in the ABR are different. A high alkalinity in the methanogenic compartment of the ABR was able to secure the pH neutral and methane generation. In general, the ABR proved to be a stable, reliable, and effective process for energy recovery and stabilization treatment of SPPW.

Simultaneous biohydrogen production and wastewater treatment based on the selective enrichment of the fermentation ecosystem

Biohydrogen production from synthetic wastewater as substrate was studied in anaerobic small scale batch reactors. Enriched anaerobic mixed consortia sampled from various environments were used as parent inocula to start the bioreactors. Selective enrichments were achieved by various physical and chemical pretreatments and changes in the microbial communities were monitored by metagenomic and molecular diagnostics approaches. Experimental data showed the feasibility of biohydrogen production using synthetic wastewater as substrate. The hydrogen generation capability of the different mixed consortia is clearly dependent on the pretreatment methods. The described approach opens the possibility for an alternative way towards simultaneous wastewater treatment and renewable energy generation.

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.

Integration of acidogenic and methanogenic processes for simultaneous production of biohydrogen and methane from wastewater treatment

Feasibility of integrating acidogenic and methanogenic processes for simultaneous production of biohydrogen (H 2) and methane (CH 4) was studied in two separate biofilm reactors from wastewater treatment. Acidogenic bioreactor (acidogenic sequencing batch biofilm reactor, AcSBBR) was operated with designed synthetic wastewater [organic loading rate (OLR) 4.75 kg COD/m 3-day] under acidophilic conditions (pH 6.0) using selectively enriched acidogenic mixed consortia. The resultant outlet from AcSBBR composed of fermentative soluble intermediates (with residual carbon source), was used as feed for subsequent methanogenic bioreactor (methanogenic/anaerobic sequencing batch biofilm reactor, AnSBBR, pH 7.0) to generate additional biogas (CH 4) utilizing residual organic composition employing anaerobic mixed consortia. During the stabilized phase of operation (after 60 days) AcSBBR showed H 2 production of 16.91 mmol/day in association with COD removal efficiency of 36.56% (SDR A—1.736 kg COD/m 3-day). AnSBBR showed additional COD removal efficiency of 54.44% (SDR M—1.071 kg COD/m 3-day) along with CH 4 generation. Integration of the acidogenic and methanogenic processes enhanced substrate degradation efficiency (SDR T—4.01 kg COD/m 3-day) along with generation of both H 2 and CH 4 indicating sustainability of the process.

Simultaneous biohydrogen production and wastewater treatment in biofilm configured anaerobic periodic discontinuous batch reactor using distillery wastewater

Biohydrogen (H 2) production with simultaneous wastewater treatment was studied in anaerobic sequencing batch biofilm reactor (AnSBBR) using distillery wastewater as substrate at two operating pH values. Selectively enriched anaerobic mixed consortia sequentially pretreated with repeated heat-shock (100 °C; 2 h) and acid (pH - 3.0 ; 24 h) methods, was used as parent inoculum to startup the bioreactor. The reactor was operated at ambient temperature ( 28 ± 2 ∘ C ) with detention time of 24 h in periodic discontinuous batch mode. Experimental data showed the feasibility of hydrogen production along with substrate degradation with distillery wastewater as substrate. The performance of the reactor was found to be dependent on the operating pH. Adopted acidophilic microenvironment (pH 6.0) favored H 2 production (H 2 production rate—26 mmol H 2/day; specific H 2 production—6.98 mol H 2/kg COD R-day) over neutral microenvironment (H 2 production rate—7 mmol H 2/day; specific H 2 production—1.63 mol H 2/kg COD R-day). However, COD removal efficiency was found to be effective in operated neutral microenvironment (pH 7—69.68%; pH 6.0—56.25%). The described process documented the dual benefit of renewable energy generation in the form of H 2 with simultaneous wastewater treatment utilizing it as substrate.

Simultaneous production of biohydrogen and bioethanol with fluidized-bed and packed-bed bioreactors containing immobilized anaerobic sludge

Hydrogen and ethanol are promising biofuels and of great potential to become alternatives to fossil fuels. In this work, two bioreactor systems, namely fluidized-bed (FBR) and packed-bed (PBR), were developed to produce H 2 and ethanol simultaneously from dark fermentation of carbohydrate substrates using polyethylene–octane elastomer immobilized anaerobic sludge as the biocatalyst. The H 2 and ethanol production in FBR essentially increased with increasing upflow velocity ( v up ), as sucrose and fructose was better substrate for the yield of H 2 and ethanol, respectively. With FBR operated at v up = 0.91 cm s − 1 , sucrose gave the highest H 2 production rate (59 mmol h −1 l −1) among the three sugar substrates (sucrose, glucose, and fructose) tested, but the best H 2 yield (1.04 mol mol hexose −1) was obtained with glucose at v up = 0.55 cm s − 1 . For ethanol production in FBR, fructose was the favorable substrate, resulting in maximum ethanol production rate and yield of 378 mmol h −1 l −1 and 0.65 mol mol hexose −1, respectively, when operating at v up = 0.91 cm s − 1 . At a hydraulic retention time of 4 h, the PBR system produced H 2 and ethanol at a slower rate of 16 and 6 mmol h −1 l −1, respectively, by using glucose. However, the yields of H 2 and ethanol were comparable to those for FBR. The soluble metabolites were dominated by ethanol, accounting for 43–65% of total soluble microbial products. The production of acetate and butyrate was less significant when compared to cultures optimized for H 2 production. Comparison of the yield of H 2 and ethanol shows that production of H 2 and ethanol was reversely correlated. The total energy generation based on the heat values of H 2 and ethanol was calculated to assess the overall efficiency of energy production. In FBR, the energy generation rate was higher when a faster upflow velocity was used. The best energy generation rate and yield was 526 kJ h −1 l −1 and 1048 kJ mol hexose −1, respectively, both occurred with fructose-feeding FBR operated at v up = 0.91 cm s − 1 . The PBR system displayed a lower energy generation rate, whereas the energy yield was comparable or even higher than those for FBR.