Hydrothermal carbonization of unwanted biomass materials: Effect of process temperature and retention time on hydrochar and liquid fraction

Hydrothermal carbonization (HTC) was applied to examine the feasibility in converting coconut husk (CH) and rice husk (RH) to renewable fuel resource and valuable dissolved organic chemicals. HTC was conducted with varying process temperature (140–200 °C) and retention time (1–4 h). CH was a better feedstock to produce hydrochar as solid fuel than RH because of its compositions was significantly different. An increase in process temperature from 140 to 200 °C resulted in a decrease in hydrochar yield of CH from 77.1 to 67.8%, and corresponding decreases in O/C and H/C from 0.6 and 1.4 to 0.4 and 1.2, respectively, and this was associated to dehydration and decarboxylation reactions. Fuel ratio and HHV were in the range of 0.66–0.86 and 20.7–23.9 MJ/kg, respectively. Liquid fractions (LF) from both RH and CH were found to be abundant in dissolved organic chemicals which were regarded as valuable intermediate chemicals, including furfural, furfuryl alcohol, hydroxymethylfurfural (HMF), and low molecular-weight carboxylic acids (lactic acid, formic acid, acetic acid, levulinic acid, and propionic acid).     

Thermo-chemical conversion of waste rubber seed shell to produce fuel and value-added chemicals

Rubber seed shell (RSS), comprises of 96.67 wt% organic content and 38.6% crystallinity index, was used for the production of biofuel and value-added chemicals through semi-batch pyrolysis. Thermogravimetric analysis (TGA) of RSS at heating rate of 20 °C/min showed R50 value as 12.72%/min at 376.5 °C. The gaseous product evolved during the decomposition of RSS were analyzed through inline Fourier transform infrared (FT-IR) coupled with TGA instrument. The effects of pyrolysis temperatures (350°C-600 °C) and heating rates (10°C/min–40 °C/min) on the product distribution (liquid, gas and bio-char) were investigated. The maximum yield of liquid product (46.14 wt%) and the carbon-rich bio-char (31.92 wt%) were obtained at 550 °C temperature for heating rate of 30 °C/min. The fuel characteristics of produced bio-char such as higher calorific value (34.5 MJ/kg), higher fixed carbon (79.74 wt%), lower ash (1.87 wt%) and lower moisture content (2.11 wt%) suggested its potential to be used as solid fuel. Value-added organic compounds such as acetic acid, phenolic compounds, creosol, pilocarpine, benzene and levoglucosan were identified in the liquid product using gas chromatography. The pH values of liquid products (2.55–3.0) support the presence of organic acids and phenolic fraction. The presence of various functional groups was also identified using FT-IR spectroscopy. In depth analysis of physico-chemical-thermal properties of RSS and obtained products (liquid and bio-char) suggested that RSS can be considered as a suitable feedstock for the production of value added chemicals including fuel.     

Effects of process,operational and environmental variables on biohydrogen production using palm oil mill effluent (POME)

A batch study for biohydrogen production was conducted using raw palm oil mill effluent (POME) and POME sludge as a feed and inoculum respectively. Response Surface Methodology (RSM) was used to design the experiments. Experiments were conducted at different reaction temperatures (30–50 °C), inoculum size to substrate ratios (I:S) and reaction times (8–24 h). An optimum condition of biohydrogen production was achieved with COD removal efficiency of 21.95% with hydrogen yield of 28.47 ml H₂ g^?1 COD removed. The I:S ratio was 40:60, with reaction temperature of 50 °C at 8 h of reaction time. The study showed that a lower substrate concentration (less than 20 g L^?1) for biohydrogen production using pre-settled POME was achievable, with optimum HRT of 8 h under thermophilic condition (50 °C). This study also found that pre-settled POME is feasible to be used as a substrate for biohydrogen production under thermophilic condition.     

Effect of aluminium sulphate-catalysed hydrolysis process on furfural yield and cellulose degradation of Cannabis sativa L. shives

Commercially, furfural is produced from pentosan-rich biomass using mineral acids as homogeneous catalysts. This study investigated a novel hydrolysis method that allows to obtain furfural from hemp shives with high yield and also to preserve the cellulose in the remaining biomass for other bioconversion processes. To date, hemp shives have not been investigated for furfural production. Cannabis sativa L. (“Bialobrzeskie” variety) shives were used as a feedstock due to the high content of pentosan (17.6% of oven-dried biomass). It means that the theoretically possible amount of furfural was 12.8% of oven-dried hemp shives. The effect of temperature (140–180 °C), the amount of catalyst (3–7% of oven-dried biomass) and the treatment time (10–90 min) on the furfural formation were studied. Whereas, the effect of the same temperature and the amount of catalyst on the changes of lignocellulose were studied after 90 min treatment time. Al₂(SO₄)₃*18H₂O was used as a catalyst for the conversion of C5-sugars to furfural. To show the catalytic properties of Al₂(SO₄)₃*18H₂O, autocatalysis was performed as a reference process using the same parameters. The highest yield of furfural, 73.7% of the theoretical yield, was obtained at 180 °C, 5% Al₂(SO₄)₃*18H₂O of oven-dried mass and 90 min. From the biorefinery perspective, the optimal hydrolysis parameters were 160 °C, 5% Al₂(SO₄)₃*18H₂O of oven-dried mass and 90 min. With these parameters, the yield of furfural was 62.7% of the theoretical yield, 99.2% of hemicelluloses were removed and 95.8% of cellulose was preserved and slightly depolymerized.     

Impact of furfural on biological hydrogen production kinetics from synthetic lignocellulosic hydrolysate using mesophilic and thermophilic mixed cultures

The impact of furfural on hydrogen production and microbial growth kinetics was assessed using mixed anaerobic cultures at mesophilic and thermophilic conditions. Mesophilic experiments showed a hydrogen yield of 1.6 mol H₂/mol initial sugars at 1 g/L furfural which is a 45% enhancement from the control (0 g/L furfural) at a substrate-to-biomass ratio (S°/X°) of 4 gCOD/gVSS. On the other hand, thermophilic experiments showed no enhancement at 1 g/L furfural but rather a 53% decrease in hydrogen yield from its control. Furfural inhibition threshold limit was observed to be greater than 1 g/L for mesophilic experiments and less than 1 g/L for thermophilic experiments. In both cases, 4 g/L was the most recalcitrant furfural concentration, with propionate and lactate the most predominant soluble metabolites in the mesophilic and thermophilic experiments respectively. It was also noted that in the presence of furfural, hydrogen-producers in both mesophilic and thermophilic mixed cultures were inactivated as no hydrogen was produced until furfural was completely degraded irrespective of sugars degradation. This study also presents the kinetics of microbial growth and substrate degradation obtained using the Monod model on MATLAB^®, ignoring an inhibition term. IC₅₀ of the mesophilic and thermophilic experiments were 1.03 g/L and 0.5 g/L respectively indicating that the thermophilic hydrogen producers were more strongly affected by furfural than the mesophilic cultures.     

Biohydrogen production from Imperata cylindrica bio-oil using non-stoichiometric and thermodynamic model

This paper presents a non-stoichiometric and thermodynamic model for steam reforming of Imperata cylindrica bio-oil for biohydrogen production. Thermodynamic analyses of major bio-oil components such as formic acid, propanoic acid, oleic acid, hexadecanoic acid and octanol produced from fast pyrolysis of I. cylindrica was examined. Sensitivity analyses of the operating conditions; temperature (100–1000 °C), pressure (1–10 atm) and steam to fuel ratio (1–10) were determined. The results showed an increase in biohydrogen yield with increasing temperature although the effect of pressure was negligible. Furthermore, increase in steam to fuel ratio favoured biohydrogen production. Maximum yield of 60 ± 10% at 500–810 °C temperature range and steam to fuel ratio 5–9 was obtained for formic acid, propanoic acid and octanol. The heavier components hexadecanoic and oleic acid maximum hydrogen yield are 40% (740 °C and S/F = 9) and 43% (810 °C and S/F = 8) respectively. However, the effect of pressure on biohydrogen yield at the selected reforming temperatures was negligible. Overall, the results of the study demonstrate that the non-stoichiometry and thermodynamic model can successfully predict biohydrogen yield as well as the composition of gas mixtures from the gasification and steam reforming of bio-oil from biomass resources. This will serve as a useful guide for further experimental works and process development.     

Characteristics of hydrochar and liquid fraction from hydrothermal carbonization of cassava rhizome

Hydrothermal carbonization (HTC) of cassava rhizome (CR) was performed to investigate the effect of process parameters including temperature, time, and biomass to water ratio (BTW) on characteristics of hydrochar and liquid fraction products. The effect of temperature was two-fold. First, an increase in reaction temperature from 160 to 180 °C decreased hydrochar yield from 54 to 51%, however, a further increase of temperature from 180 to 200 °C saw an increase in the hydrochar yield to 58%. This was associated to degradation, polymerization, and condensation reactions during HTC. The hydrogen/carbon and oxygen/carbon atomic ratios decreased from 1.4 and 0.6 at 160 °C to 1.2 and 0.4 at 200 °C, respectively. The liquid fraction contained various valuable chemical species including, glucose, furan compounds, (furfural, furfuryl alcohol, hydroxymethylfurfural), volatile fatty acid (succinic acid, lactic acid, formic acid, acetic acid, levulinic acid, and propionic acid) with their highest yields (wt.% dry raw material) of 4.5, 18.5, and 24.3, respectively.     

Influence of torrefaction on properties of activated carbon obtained from physical activation of pyrolysis char

In this paper, the method of ‘torrefaction–fast pyrolysis–physical activation’ was conducted to investigate the impact of torrefaction on the properties of activated carbon through CO₂ activation. It was found that torrefaction had a significantly positive influence on the quality of activated carbon and 280°C was the optimal torrefaction temperature. The activated carbon obtained under the recommended condition had a higher yield (13.0 ± 0.3% based on dried rice husk) and most developed pore structure (specific surface area of 1090.7 m²/g). The results may be helpful for the potential utilization of high ash content biomass like rice husk.     

Optimization of biohydrogen production by the novel psychrophilic strain N92 collected from the Antarctica

In this study, the response surface methodology (RSM) with central composite design (CCD) was employed to improve the hydrogen production by the psychrophilic N92 strain (EU636058) isolated from Antarctica, which is closely related to Pseudorhodobacter sp. (KT163920). The influence of operational conditions such as temperature (4.7–55.2 °C), initial pH (3.44–10.16), and initial glucose concentration (4.7–55.23 g/dm³), as well as the initial concentrations of (NH₄)₂SO₄ (0.05–3.98 g/dm³), FeSO₄ (0.02–1.33 g/dm³) and NaHCO₃ (0.02–3.95 g/dm³) was evaluated. The linear effect of glucose concentration, along with the quadratic effect of all the six factors were the most significant terms affecting the biohydrogen yield by N92 strain. The optimum conditions for the maximum hydrogen yield of 1.7 mol H₂/mol glucose were initial pH of 6.86, glucose concentration of 28.4 g/dm³, temperature 29 °C and initial concentration of (NH₄)₂SO₄, FeSO₄ and NaHCO₃ of 0.53, 1.55 and 1.64 g/dm³ respectively. Analysis of the metabolites produced under the optimum conditions showed that the most abundant were acetic acid (0.8 g/dm³), butyric acid (0.7 g/dm³) and ethanol (2.1 g/dm³). We suggest that the bioprocess established in this study using the strain N92 could be an alternative for hydrogen production with the advantages of constituting low energy costs in fermentation.     

Study of chemical looping co-gasification (CLCG) of coal and rice husk with an iron-based oxygen carrier via solid–solid reactions

The chemical looping gasification (CLG) is a promising gasification technology for syngas production. It reduces the demand for pure oxygen and heat from outside by the cycle of oxygen carriers. The lattice oxygen is transferred by oxygen carrier like Fe₂O₃ in CLG. Considering the synergy between lignite and rice husk, the chemical looping co-gasification (CLCG) of lignite and rice husk with Fe₂O₃ as oxygen carrier was studied in this work. The mass loss of lignite increased by about 3% with the help of rice husk. Due to the synergetic effect, rice husk developed the pyrolysis of coal in the co-gasification. It is found that the most contributing reaction at around 800 °C–1000 °C in CLG is the gasification of char with Fe₂O₃via solid-solid reactions. The kinetic fitting was used to explore the reaction mechanism of CLCG. The modified random pore model (MRPM) fitted the experimental data well, which confirmed the solid-solid reactions between char and Fe₂O₃, and the synergy between lignite and rice husk in CLCG. Finally, the gas analysis was conducted in a fixed bed system with gas analyzers. It is found that Fe₂O₃ enhanced the concentration of CO and CO₂ in CLG process.     

Biophysicochemical evaluation and micropropagation study of Jatropha curcas L. collections for biodiesel production

Jatropha curcas, a member of the Euphorbiaceae family, is an upcoming energy source, which promises to mitigate the energy crisis and environmental pollution. Jatropha curcas oil is looked up in terms of availability and cost and also has several applications and enormous economic benefits. The seed oils of five Jatropha curcas biotypes were screened and evaluated for their physiochemical parameters, viz. oil content (20–43%), biodiesel yield (48–66%), density (.866–.969 g/cm³), viscosity (50.12–93.79 mm³/s), iodine value (232.738–457.16 mg/g), free fatty acid (18.847–7.614 mg/g), saponification value (59.29–93.79 mg/g), flash point (125–220°C), fire point (155–260°C) and ash content (.19–.399%), which were estimated for selection of the elite Jatropha curcas biotype. The best shoot regeneration (60%) was observed in Murashige and Skoog (MS) medium supplemented with naphthalene acetic acid (0.5 ppm) and benzyl amino purine (2.0 ppm). Root induction (90%) was successfully obtained in plain MS. Acclimatisation and hardening was quite successful with survival rate of 70%.     

Enhanced hydrogen and volatile fatty acid production from sweet sorghum stalks by two-steps dark fermentation with dilute acid treatment in between

This study investigated the potential of hydrogen and volatile fatty acid coproduction from two steps dark fermentation with dilute acid treatments of the residual slurry after 1st step fermentation. Sweet sorghum stalks (SS) was used as substrate along with Clostridium thermosaccharolyticum as production microbe. Residual lignocelluloses after 1st step fermentation were treated for 1 h by sulfuric acid concentration of 0.25, 0.5, 1.0, 1.5, 2.0 and 2.5% (w/v) with different reaction temperature of 120, 90 and 60 °C were studied. The optimum severity conditions for the highest yield of products found from the treatment acid concentration of 1.5% (w/v) at 120 °C for 10 g/L of substrate concentration. Experimental data showed that two-step fermentation increased 76% hydrogen, 84% acetic acid and 113% of butyric acid production from single step. Maximum yields of hydrogen, acetic acid and butyric acid were 5.77 mmol/g-substrate, 2.17 g/L and 2.07 g/L respectively. This two-step fermentation for hydrogen and VFA production using the whole slurry would be a promising approach to SS biorefinery.     

Selection of metabolic pathways for continuous hydrogen production under thermophilic and mesophilic temperature conditions in anaerobic fluidized bed reactors

This study evaluated the influence of hydraulic retention time (HRT) on hydrogen (H₂) production in anaerobic fluidized bed reactors at mesophilic (30 °C, AFBR-M) and thermophilic (55 °C, AFBR-T) temperatures. Reactors were fed sucrose-based synthetic wastewater (5000 mg chemical oxygen demand·L^?1) in the HRT of 8, 6, 4, 2, or 1 h. H₂ production rate increased from 67.8 ± 14.8 to 194.9 ± 57.0 ml H₂·h^?1 L^?1 (AFBR-T) and from 72.0 ± 10.0 to 344.4 ± 74.0 mL H₂·h^?1·l^?1 (AFBR-M) when HRT decreased from 8 to 1 h. Maximum H₂ yields for AFBR-T and AFBR-M were 1.93 ± 0.21 and 2.68 ± 0.48 mol H₂·mol^?1 sucrose, respectively. The main metabolites were acetic acid (31.3%–41.5%) and butyric acid (10.2%–20.7%) (AFBR-M) and acetate (20.1%–39.3%) and ethanol (14.3%–29.9%) (AFBR-T). Denaturing gradient gel electrophoresis profiles revealed selective enrichment of microbial populations responsible for H₂ production by the aceto-butyric route (AFBR-M) and ethanol-type fermentation (AFBR-T).     

Hydrogen,alcohols and volatile fatty acids from the co-digestion of coffee waste (coffee pulp,husk, and processing wastewater) by applying autochthonous microorganisms

The objective of this study was to screen the factors that affect H₂, organic acids and alcohols production from coffee waste pretreated in a hydrothermal reactor applying consortium of bacteria and fungi (indigenous from coffee waste) with hydrolytic and fermentative activity. The effects of pH (4.0–7.0), temperature (30–50 °C), agitation (0–180 rpm), headspace (50–70%), percentage of bioaugmentation (without microbial consortium to 20%), concentration of coffee pulp and husk (2–6 g/L), coffee processing wastewater (7-30 gCOD/L) and yeast extract (0–2 g/L) were evaluated using a Plackett-Burman design. The highest H₂ production potential (82 ml H₂) was obtained under the following conditions: 30 °C, 180 rpm, 50% headspace, without bioaugmentation, 2 g/L pulp and husk coffee, 30 gCOD/L coffee processing wastewater and 2 g/L yeast extract. The main soluble products were acetic acid (1956 mg/L), lactic acid (786 mg/L) and ethanol (816 mg/L). Lactobacillus sp., Clostridium sp., Saccharomyces sp. and Kazachstania sp. were the main autochthonous microorganisms identified. Through metagenome functional analysis, enzymes related to lignin, phenol, cellulose, lignocellulose, and pectin degradation were identified, as well as acidogenesis, and H₂ production.     

Optimisation of sepiolite clay with phosphoric acid treatment as support material for CoB catalyst and application to produce hydrogen from the NaBH4 hydrolysis

Herein, the CoB catalyst supported on the sepiolite clay treated with phosphoric acid was utilized to produce hydrogen from the NaBH₄ hydrolysis. In order to analyse the performance of the phosphoric acid treated sepiolite clay supported-CoB catalyst, the NaBH₄ concentration effect, phosphoric acid concentration effect, phosphoric acid impregnation time effect, CoB catalyst percentage effect, and temperature effect were studied. In addition, XRD, XPS, SEM, TEM, BET, and FTIR analysis were performed for characterization of Co–B catalyst supported on the acid-treated sepiolite. The completion time of this hydrolysis reaction with Co–B (20%) catalyst supported on the sepiolite treated by 5 M phosphoric acid was approximately 80 min, whereas the completion time of this hydrolysis reaction with acid-free sepiolite-supported Co–B (20%) catalyst was approximately 260 min. There is a five-fold increase in the maximum production rate. The maximum hydrogen production rates of this hydrolysis reaction at 30 and 60 °C were found as 1486 and 5025 ml min⁻¹g⁻¹_catalyst, respectively. Activation energy was found as 21.4 kJ/mol. This result indicates that the acid treatment on sepiolite is quite successful. The re-usability of NaBH₄ hydrolysis reaction by CoB catalyst supported on sepiolite treated phosphoric acid for successive five cycles of NaBH₄ at 30 °C was investigated.     

Lignin yield maximization of mixed biorefinery feedstocks by organosolv fractionation using Taguchi Robust Product Design

Lignin, isolated from switchgrass (Panicum virgatum) and tulip poplar (Liriodendron tulipifera) using organosolv fractionation is currently being explored for its potential use in the production of value-added chemicals and bio-based polymers. Taguchi Robust Product Design (TRPD) was applied to maximize lignin yield from the fractionation process. The following four controllable design factors were used in the TRPD: process temperature (120 °C, 140 °C and 160 °C), fractionation time (56 and 90 min), sulfuric acid concentration (0.025 M, 0.05 M and 0.1 M), and feedstock type (switchgrass/tulip poplar chip ratios of 10/90, 50/50 and 90/10). Process noise was induced in the experiment by using either the mass- or volume-based feedstock charges of switchgrass and tulip poplar chips. A maximum mean lignin yield of 78.63 wt% and signal-to-noise ratio of 37.90 was found at a 90 min runtime, a process temperature of 160 °C, a sulfuric acid concentration of 0.1 M, and a feedstock composition of 10% switchgrass and 90% tulip poplar. Process temperature was the most significant factor that influenced lignin yield. This study may provide a pathway for industrialists and researchers interested in maximizing lignin yield in the organosolv fractionation process.     

Repeated batch fermentation for photo-hydrogen and lipid production from wastewater of a sugar manufacturing plant

Hydrogen and lipid production from sugar manufacturing plant wastewater (SMW) by Rhodobacter sp. KKU-PS1 were investigated. Aji-L (i.e., a waste from the process of crystallizing monosodium glutamate) was used as nitrogen source. Batch fermentation was conducted in 300 mL serum bottles with the working volume of 180 mL to investigate the optimal inoculum size by varying the initial inoculum concentration from 0.23 to 0.92 g_CDW/L. The photo-fermentation was conducted at an initial pH 7.0 and 25.6 °C with continuously light illumination at 7500 lux. The optimal inoculum size of 0.77 g_CDW/L gave the hydrogen production rate (R_m) and lipid production of 5.24 mL H₂/L.h and 407 mg lipid/L, respectively. The hydrogen production from SMW was further examined in 1.7-L photo-bioreactor with the working volume of 1.2-L using the optimal condition from batch experiment. A photo-bioreactor yielded 1.73 times higher R_m than that obtained from the fermentation in serum bottles with a greater lipid production of 424 mg lipid/L. Hydrogen production from SMW in the repeated-batch fermentation was further studied by varying the medium replacement ratios of 25, 50–75%. A maximum biomass and lipid concentration of 2.83 g_CDW/L and 685 mg lipid/L, respectively were achieved at a medium replacement ratio of 75%. C18:1 (51.2%), C18:0 (24.9%) and C16:0 (9.1%) were found as the major free fatty acid. Lactic acid followed by propionic, acetic and butyric acids containing in SMW were the suitable carbon source for biomass production of KKU-PS1.     

Electrochemical performance assessment of low-temperature solid oxide fuel cell with YSZ-based and SDC-based electrolytes

In this work, solid oxide fuel cells (SOFCs) based on different electrolytes, i.e., the yttria-stabilized zirconia (YSZ) and the samaria-doped ceria (SDC), were investigated to study their performances at low-temperature operation. The predicted performance of both SOFCs was validated with the experimental results. The verified models were implemented to study the impact of operating conditions, i.e., cell temperature, pressure, thicknesses of cathode, anode, and electrolyte, on their performances. The decrease in the operating temperature from intermediate range (800–900 °C) to low range (550–650 °C) has a considerable effect on the performance of the YSZ-based SOFC as conventional type, which dropped from 0.67–1.40 W/cm² to 0.027–0.13 W/cm². Under the low operating temperature range, the performance of SDC-based SOFC was superior to that of the YSZ-based SOFC, due to the lower ohmic loss. Nevertheless, the SDC-based SOFC has higher concentration overpotentials than the YSZ-based SOFC. The concentration overpotentials of the SDC-based SOFC can be reduced by the thinner anode and cathode thicknesses. In addition, the SDC-based SOFC at low operating temperature with the pressurized operation could significantly improve its power density, about 20% at 2 bar, which was close to that of YSZ-based SOFC at intermediate temperature of 800 °C.     

Sequential fermentation of hydrogen and methane from steam-exploded sugarcane bagasse hydrolysate

The goal of this study was to sequential fermentation of hydrogen and methane from sugarcane bagasse (SCB). Steam explosion conditions for pretreating SCB were optimum at 195 °C and 1.5 min, which yielded 36.35 g/L of total sugar and 2.35 g/L of total inhibitors. Under these conditions (all in g/L): glucose, 11.33; xylose, 24.41; arabinose, 0.61; acetic acid, 2.33; and furfural, 0.02 were obtained. The resulting hydrolysate was used to produce hydrogen by anaerobic mixed cultures. A maximum hydrogen production rate of 396.50 mL H₂/L day was achieved at an initial pH of 6 and an initial total sugar concentration of 10 g/L. The effluent from the hydrogen fermentation process was further used to produce methane. Response surface methodology with central composite design was used to obtain the suitable conditions for maximizing methane production rate (MPR). An MPR of 185.73 mL/L day was achieved at initial pH, Ni and Fe concentrations of 7.59, 3.61 mg/L and 8.44 mg/L, respectively. Total energy of 304.11 kJ/L-substrate was obtained from a sequential fermentation of hydrogen and methane. This approach will not only add value to SCB, in the form of safe and clean energy, but also provide a solution for making use of this abundant waste.     

Hydrogen evolution in microbial electrolysis cells treating landfill leachate: Dynamics of anodic biofilm

This study investigates the potential opportunities of hydrogen evolution treating landfill leachate in a set of two microbial electrolysis cells (MEC-1 and 2) under 30 °C and 17 ± 3 °C temperatures, respectively. The system achieved a projected current density of 1000–1200 mA m^?2 (MEC-1) and 530–755 mA m^?2 (MEC-2) coupled with low cost hydrogen production rate of 0.148 L La^?1 d^?1 (MEC-1) and 0.04 L La^?1 d^?1 (MEC-2) at an applied voltage of 1.0 V. Current generation led to a maximum COD oxidation of 73 ± 8% (MEC-1) and 65 ± 7% (MEC-2) with ≥100% energy recovery. The system also exhibited a high hydrogen recovery (66–95%), pure hydrogen yield (98%) and tremendous working stability during two months of operation. Electroactive microbes such as Pseudomonadaceae, Geobacteraceae and Comamonadaceae were found in anodophilic biofim, along with Rhodospirillaceae and Rhodocyclaceae, which could be involved in hydrogen production. These results demonstrated an energy-efficient approach for hydrogen production coupled with pollutants removal.