Utilizing acid-rich effluents of fermentative hydrogen production process as substrate for harnessing bioelectricity: An integrative approach

Lower substrate degradation is one of the limiting factors associated with fermentative hydrogen production process. To overcome this, an attempt was made to integrate microbial fuel cell (MFC) as a secondary energy generating process with the fermentative hydrogen (H₂) production. The acid-rich effluents generated from the acidogenic sequential batch biofilm reactor (AcSBBR) producing H₂ by fermenting vegetable waste was subsequently used as substrate for bioelectricity generation in single chambered MFC (air cathode; non-catalyzed electrodes). AcSBBR was operated at 70.4 kg COD/m³-day and the outlet was fed to the MFC at three variable organic loading rates. The final outlet from AcSBBR was composed of fermentative soluble acid intermediates along with residual carbon source. Experimental data illustrated the feasibility of utilizing acid-rich effluents by MFC for both additional energy generation and wastewater treatment. Higher power output (111.76 mW/m²) was observed at lower substrate loading condition. MFC also illustrated its function as wastewater treatment unit by removing COD (80%), volatile fatty acids (79%), carbohydrates (78%) and turbidity (65.38%) effectively. Fermented form of vegetable wastewater exhibited higher improvement (94%) in power compared to unfermented wastewater. The performance of MFC was characterized with respect to polarization behavior, cell potentials, cyclic voltammetry and sustainable power. This integration approach enhanced wastewater treatment efficiency (COD removal, 84.6%) along with additional energy generation demonstrating both environmental and economic sustainability of the process.     

Which determines power generation of microbial fuel cell based on carbon anode,surface morphology or oxygen-containing group?

To clarify the role of carbon surface nature in the power generation of microbial fuel cell (MFC) based on carbon anode, three carbon felt samples, obtained by simple water cleaning (CCF), heating (HCF) and oxidation with ammonium persulfate (ACF), were characterized with SEM, BET, FTIR, cyclic voltammetry and acid titration, and their performances as anode of MFC were investigated with polarization curve measurement, chronoamperometry and chronopotentiometry. It is found that the power output of MFC depends on the morphology rather than the oxygen-containing group concentration of the carbon felt surface. CCF, HCF and ACF have their surface oxygen-containing groups of 1.52, 0.8 and 0.45 mM m⁻² and specific surface areas of 0.33, 0.65 and 1.19 m² g⁻¹, but yield their maximal power densities of 606, 858 and 990 mW m⁻², respectively. This study suggests that intensive attention should be paid to the design of surface morphology in order to improve power generation of MFC.     

Facile preparation of binder-free NiO/MnO2-carbon felt anode to enhance electricity generation and dye wastewater degradation performances of microbial fuel cell

Binder-free NiO/MnO₂-carbon felt electrode is prepared with a facile two-step hydrothermal method. The NiO self-grown on the carbon felt is used as the skeleton structure to support the in-situ growth of MnO₂. Both the core and shell materials are excellent pseudocapacitance materials. The compositing of such pseudocapacitance metal oxides can produce synergistic effects, so that the modified electrode has a high capacitance. NiO/MnO₂-carbon felt electrode also possesses a high specific surface area, super hydrophilicity and good biocompatibility, which are conducive to the enrichment of typical exoelectrogen Geobacter. As the anode, NiO/MnO₂-carbon felt electrode can effectively improve the electricity generation and methyl orange (MO) wastewater degradation performances of microbial fuel cell (MFC). The highest output voltage and the maximum power density of MFC with NiO/MnO₂-carbon felt anode are respectively 652 mV and 628 mW m^?2, which are much higher than those of MFC with MnO₂-carbon felt anode (613 mV, 544 mW m^?2), NiO-carbon felt anode (504 mV, 197 mW m^?2) and unmodified carbon felt anode (423 mV, 162 mW m^?2). The decolourization efficiency and the chemical oxygen demand (COD) removal rate of MO for MFC with NiO/MnO₂-carbon felt anode are respectively 92.5% and 58.2% at 48 h.     

Microbial fuel cells for bioelectricity generation through reduction of hexavalent chromium in wastewater: A review

The study proposes the use of microbial fuel cell (MFC) technology to reduce toxic Cr(VI) present in industrial wastewater to less toxic trivalent chromium [Cr(III)], while generating electricity through a bioelectrochemical oxidation-reduction process. Factors influencing the treatment process and electricity generation include the concentration of Cr(VI) in wastewater, substrate types used for anodes, types of microorganisms involved, types of cathode and anode, surface area of the cathode and anode, and pH and temperature of cathodic and anodic solutions. While other heavy metals in wastewater may be removed by MFC technology, Cr(VI) removal is more efficient in terms of electricity generation. Previous research indicated that the maximum electrical power generated by Cr(VI) removal through the use of MFCs is 1600 mW/m², which is expected to increase as the factors affecting this process are optimized. Based on current data, MFC-based electricity generation along with Cr(VI) removal is a potential future source of sustainable energy. However, research priorities need to focus on reducing the cost of MFC technology by using economical and effective materials and increasing electricity production.     

Canteen based composite food waste as potential anodic fuel for bioelectricity generation in single chambered microbial fuel cell (MFC): Bio-electrochemical evaluation under increasing substrate loading condition

Canteen based composite food waste, which is rich in organic constituents was evaluated as anodic fuel (substrate) in single chambered microbial fuel cell (MFC; mediator less; non-catalyzed graphite electrodes; open-air cathode) to harness electrical energy via anaerobic treatment. The performance of MFC was evaluated with anaerobic consortia as anodic biocatalyst under various increasing organic loading rates (OLR1, 1.01 kg COD/m³-day; OLR2, 1.74 kg COD/m³-day; OLR3, 2.61 kg COD/m³-day). The experimental results illustrated the feasibility of bioelectricity generation from food waste along with treatment but depend on the applied organic load. The maximum power output was observed at OLR2 (295 mV; 390 mA/m²), followed by OLR3 (250 mV; 311 mA/m²) and OLR1 (188 mV; 211 mA/m²). The variation in substrate degradation has also showed a relation with organic load applied (OLR1, 44.28% (0.47 kg COD/m³-day); OLR2, 64.83% (1.13 kg COD/m³-day); OLR3, 46.28% (1.39 kg COD/m³-day)). The increase in loading from OLR1 to OLR2, the catalytic ability of biocatalyst increased from 7.5 mA (24 h) to 11.22 mA (24 h) along with the increase in power generation from 39.38 mW/m² to 107.89 mW/m². At the higher OLR (OLR3), the bioelectrocatalytic current decreased to 5.3 mA (24 h) along with decrement in power to 78.92 mW/m². The optimum organic load (OLR2) showed maximal catalytic activity and power output. Fuel cell behavior with respect to polarization, anode potential and bio-electrochemical behavior supported the higher performance of MFC at OLR2. Specific power yield was also observed to be higher at OLR2 (0.320 W/kg COD_R) indicating the combined process efficiency. Volatile fatty acids generation and pH profiles also correlated well with the observed results.     

Electrochemical hydrogen storage behavior of Ni-Ceria impregnated carbon micro-nanofibers

A hierarchical porous structured carbon micro-nanofiber containing the bimetallic configuration of the nickel (Ni) and ceria (CeO₂) nanoparticles (NPs) was synthesized and tested for the electrochemical hydrogen (H₂) storage capacity. The electrode exhibited a high H₂ storage capacity of 498 mA h/g or 1.858% (w/w) at the charge-discharge current density of 500 mA/g. A mechanistic insight showcased the combined contributions of the high surface area containing activated carbon microfiber (ACF) substrate, the graphitic carbon nanofibers (CNFs), and the Ni and CeO₂ NPs, towards the augmented electrochemical H₂ storage capacity and cyclic stability of the fabricated Ni–CeO₂–CNF/ACF electrode. Ni served as the catalyst for growing the CNFs via chemical vapor deposition as well as for storing H₂ via spillover mechanism, while CeO₂ created the charge carrier vacancies in the material. The measured cycle retention capacity of 99% and charge-discharge efficiency of 97.6% confirm the electrochemically stable characteristics of Ni–CeO₂–CNF/ACF, and clearly indicate it to be an economically viable and efficient H₂-storage material.     

Power recovery with multi-anode/cathode microbial fuel cells suitable for future large-scale applications

Multi-anode/cathode microbial fuel cells (MFCs) incorporate multiple MFCs into a single unit, which maintain high power generation at a low cost and small space occupation for the scale-up MFC systems. The power production of multi-anode/cathode MFCs was similar to the total power production of multiple single-anode/cathode MFCs. The power density of a 4-anode/cathode MFC was 1184 mW/m³, which was 3.2 times as that of a single-anode/cathode MFC (350 mW/m³). The effect of chemical oxygen demand (COD) was studied as the preliminary factor affecting the MFC performance. The power density of MFCs increased with COD concentrations. Multi-anode/cathode MFCs exhibited higher power generation efficiencies than single-anode/cathode MFCs at high CODs. The power output of the 4-anode/cathode MFCs kept increasing from 200 mW/m³ to 1200 mW/m³ as COD increased from 500 mg/L to 3000 mg/L, while the single-anode/cathode MFC showed no increase in the power output at CODs above 1000 mg/L. In addition, the internal resistance (R_in) exhibited strong dependence on COD and electrode distance. The R_in decreased at high CODs and short electrode distances. The tests indicated that the multi-anode/cathode configuration efficiently enhanced the power generation.     

Microbial photoelectrochemical cell for improved hydrogen evolution using nickel ferrite incorporated WO3 under visible light irradiation

The production of renewable and sustainable bioenergy has gained much more attention to contribute the society by reducing the impact of global warming. Additionally, biomass sources are highly desired due to its carbon-neutral property. In the current article, hydrogen evolution was studied by using a microbial electrolysis cell (MEC) system, composed of bio-photoelectrochemical cell (BPEC) and a microbial fuel cell (MFC). In this system, hydrogen generation was carried out under the illumination of visible light on BPEC photocathode and electrolysis voltage was supplied by MFC. The highest current density to be found as 0.74 A m⁻⁻² with average rate of H₂ evolution 1.46 ± 0.25 mL h⁻⁻¹. The photogenerated electrons emitted from MFC anode were transported to the photocathode of BPEC by an external circuit. Further, the holes have the ability to capture few electrons generated from MFC anode under visible light irradiation. This kind of situation inhibits the recombination rate of charge carrier's, make it possible the availability of more electrons/holes for H₂ production reactions. Additionally, it facilitates the leaving photogenerated electrons from MFC anode to contribute in the hydrogen generation reactions. It is firmed believed that the current study will provide an efficient strategy to rationally design a cost-competitive, ecofriendly and facile-fabrication for material and method for proficient hydrogen evolution.     

Photoelectrochemical characteristics of electrodeposited cuprous oxide with protective over layers for hydrogen evolution reactions

Cuprous oxide is one of the inexpensive options of highly efficient visible light-based photocathode for hydrogen generation in photoelectrochemical cells. Highly photoactive cuprous oxide (Cu₂O) films are obtained by cathodic electrodeposition using lactate stabilized copper sulphate precursor exhibiting a photo-current density of ~1 mA/cm² at ?0.1 V vs. RHE. Although Cu₂O is a decent choice for photoelectrochemical applications, including hydrogen evolution reaction (HER), it faces serious issues related to photodegradation and instability. To address this issue, a comparative study of two types of thin films, Al (2%)-doped ZnO (AZO) and NiO_x (usually, x > 2 at low T to x→1 at high T annealing) as photo-corrosion protective overlayers is made. The improved stability of the protected photoelectrodes is observed as noted from the photocurrent degradation of 3.5%, 0.16% and 0.03% in Cu₂O (bare), Cu₂O/AZO, and Cu₂O/NiO_x photocathodes, respectively. Furthermore, the electrochemical impedance spectroscopy reveals that electrode protected with NiO_x exhibit faster charge transfer kinetics and minimum photocurrent degradation as compare to the Cu₂O/AZO and Cu₂O(bare) photoelectrodes, proving its potential in HER kinetics.     

Electrophoretic deposition of graphene oxide on carbon brush as bioanode for microbial fuel cell operated with real wastewater

Microbial fuel cell (MFC) is a promising technology for simultaneous wastewater treatment and energy harvesting. The properties of the anode material play a critical role in the performance of the MFC. In this study, graphene oxide was prepared by a modified hummer's method. A thin layer of graphene oxide was incorporated on the carbon brush using an electrophoretic technique. The deoxygenated graphene oxide formed on the surface of the carbon brush (RGO-CB) was investigated as a bio-anode in MFC operated with real wastewater. The performance of the MFC using the RGO-CB was compared with that using plain carbon brush anode (PCB). Results showed that electrophoretic deposition of graphene oxide on the surface of carbon brush significantly enhanced the performance of the MFC, where the power density increased more than 10 times (from 33 mWm^?2 to 381 mWm^?2). Although the COD removal was nearly similar for the two MFCs, i.e., with PCB and RGO-CB; the columbic efficiency significantly increased in the case of RGO-CB anode. The improved performance in the case of the modified electrode was related to the role of the graphene in improving the electron transfer from the microorganism to the anode surface, as confirmed from the electrochemical impedance spectroscopy measurements.     

Behavior of single chambered mediatorless microbial fuel cell (MFC) at acidophilic, neutral and alkaline microenvironments during chemical wastewater treatment

Single chamber mediatorless microbial fuel cell (MFC; non-catalyzed graphite electrodes; open air cathode) behaviour was evaluated under different pH microenvironments [acidophilic (pH 6), neutral (pH 7) and alkaline (pH 8)] during chemical wastewater treatment employing anaerobic mixed consortia as anodic biocatalyst at room temperature (29 ± 2 °C). The performance was found to depend on the feed pH used. Higher current density was observed at acidophilic conditions [pH 6; 186.34 mA/m²; 100 Ω] compared to neutral [pH 7; 146.00 mA/m²; 100 Ω] and alkaline [pH 8; 135.23 mA/m²; 100 Ω]. On the contrary, substrate degradation was found to be effective at neutral pH conditions (ξ_COD – 58.98%; SDR – 0.67 kg COD/m³-day) followed by alkaline (ξ_COD – 55.76%; SDR – 0.62 kg COD/m³-day) and acidophilic (ξ_COD of 47.80%; SDR 0.58 kg COD/m³-day) conditions studied. However, relatively higher specific power yield was observed at acidophilic microenvironment (46 mW/kg COD_R) compared to neutral (35 mW/kg COD_R) and alkaline (34 mW/kg COD_R) conditions. The behaviour of the MFC was also evaluated employing electron discharge, cyclic voltammetry, cell potentials, Coulombic efficiency and sustainable power analysis. Acidophilic operation showed higher Coulombic efficiency and effective electron discharge at relatively higher resistance compared to neutral and alkaline conditions studied.     

Microbial fuel cell performance with non-Pt cathode catalysts

Various cathode catalysts prepared from metal porphyrines and phthalocyanines were examined for their oxygen reduction activity in neutral pH media. Electrochemical studies were carried out with metal tetramethoxyphenylporphyrin (TMPP), CoTMPP and FeCoTMPP, and metal phthalocyanine (Pc), FePc, CoPc and FeCuPc, supported on Ketjenblack (KJB) carbon. Iron phthalocyanine supported on KJB (FePc-KJB) carbon demonstrated higher activity towards oxygen reduction than Pt in neutral media. The effect of carbon substrate was investigated by evaluating FePc on Vulcan XC carbon (FePcVC) versus Ketjenblack carbon. FePc-KJB showed higher activity than FePcVC suggesting the catalyst activity could be improved by using carbon substrate with a higher surface area. With FePc-KJB as the MFC cathode catalyst, a power density of 634 mW m⁻² was achieved in 50 mM phosphate buffer medium at pH 7, which was higher than that obtained using the precious-metal Pt cathode (593 mW m⁻²). Under optimum operating conditions (i.e. using a high surface area carbon brush anode and 200 mM PBM as the supporting electrolyte with 1 g L⁻¹ acetate as the substrate), the power density was increased to 2011 mW m⁻². This high power output indicates that MFCs with low cost metal macrocycles catalysts is promising in further practical applications.     

Effect of recirculation on bioelectricity generation using microbial fuel cell with food waste leachate as substrate

Recirculation is one of the effective techniques used to upsurge the output of anaerobic reactors. The present study investigates the effect of recirculation of anolyte on bioelectricity generation using food waste leachate in two chamber Microbial Fuel Cell (MFC) with carbon electrodes and Ultrex as proton exchange membrane (PEM). The MFCs are operated in fed-batch mode at varying COD concentrations of 500–1250 mg/L with the hydraulic retention time of 17 h for recirculation. Maximum current density, power density and columbic efficiencies of 100.34 mA/m², 14.42 mW/m² and 10.25% respectively for MFC without recirculation and 150.30 mA/m², 29.23 mW/m² and 14.22% respectively for MFC provided with recirculation are obtained at COD of 1250 mg/L. Comparative performance analysis of the cells indicates that recirculation enhances the bioelectricity production in MFC. Scanning Electron Microscope (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) analyses are also done to find the changes in PEM.     

Co-generation of hydrogen and electricity from biodiesel process effluents

In this study, we apply a short-term voltage (0.2–0.8 V) to both crude glycerol (CG) and an anaerobic digestion (AD) effluent in a single-chamber microbial fuel cell (MFC) for power production. This improves the bioelectrogenesis in both CG (in MFC-1) and the AD effluent (in MFC-2), but higher power generation is attained in MFC-2. The use of domestic and synthetic wastewaters in the AD process leads to the generation of 195 and 350 mL H₂/L-medium, respectively. MFC-2 performs better than MFC-1 in terms of both voltage generation and chemical oxygen demand (COD) reduction. The application of 0.8 V yields a power density of 311 mW/m² (1.94 times higher than that of the control (160 mW/m²)). In addition, MFC-2 exhibits a 70% COD removal at 0.8 V, which decreases to 56% at 0.2 V. Thus, the application of a short-term voltage in MFC can stimulate both bioelectrogenesis and COD removal.     

Facile fabrication of visible light driven tin oxide photoanode and its photoelectrochemical water splitting properties

Photoelectrochemical water splitting is a promise way to transfer solar energy to hydrogen as chemical energy carrier. In this paper, visible light driven tin oxide based photoelectrodes were obtained through dipping SnCl₂·2H₂O EtOH solution on FTO or metal Ti substrate and with further heat treatment process. Photoelectrochemical measurements with three electrodes configuration revealed that this obtained photoelectrode showed n-type responsive properties and the photocurrent density reached mA/cm² level without any modification under visible light irradiation (λ > 420 nm). XRD, UV–Vis spectrum and control experimental results proposed that the visible light driven mechanism for the tin oxide based photoanode maybe ascribed to Sn⁴⁺/Sn²⁺ transformation and surface oxygen deficiency, and the tin oxide can be denoted as SnO_2−x.     

Electrospun zeolitic imidazolate framework‐derived nitrogen‐doped carbon nanofibers with high performance for lithium‐sulfur batteries

Three‐dimensional (3D) nitrogen‐doped carbon nanofibers (N‐CNFs) which were originating from nitrogen‐containing zeolitic imidazolate framework‐8 (ZIF‐8) were obtained by a combined electrospinning/carbonization technique. The pores uniformly distributed in N‐CNFs result in the improvement of electrical conductivity, increasing of BET surface area (142.82 m² g^?1), and high porosity. The as‐synthesized 3D free‐standing N‐CNFs membrane was applied as the current collector and binder free containing Li₂S₆ catholyte for lithium‐sulfur batteries. As a novel composite cathode, the free‐standing N‐CNFs/Li₂S₆ membrane shows more stable electrochemical behavior than the CNFs/Li₂S₆ membrane, exhibiting a high first‐cycle discharge specific capacity of 1175 mAh g^?1at 0.1 C and keeping discharge specific capacity of 702 mAh g^?1 at higher rate. More importantly, as the sulfur mass in cathodes was increased at 7.11 mg, the N‐CNFs/Li₂S₆ membrane delivered 467 mAh g^?1after 150 cycles at 0.2 C. The excellent electrochemical properties of N‐CNFs/Li₂S₆ membrane can be ascribed to synergistic effects of high porosity and nitrogen‐doping in N‐CNFs from carbonized ZIF‐8, illustrating collective effects of physisorption and chemisorption for lithium polysulfides in discharge‐charge processes.     

Microbial fuel cell performance of multiwall carbon nanotubes on carbon cloth as electrodes

Microbial fuel cell (MFC), which can produce electricity during treatment of wastewater, has become one of the emerging technologies in the field of environmental protection and energy recovery. Of all parts of MFC, the electrode materials play a crucial role in the electricity generation. In this study, we investigate the performance of carbon nanotube (CNT) modified carbon cloth electrodes in single-chamber MFC. The MFC is first inoculated with bacteria in wastewater and then its capability of using acetate sodium as fuel is examined. The results show that the MFC with CNT coated onto carbon cloth electrode improves the power density. In this study, the obtained maximum power density is 65 mW m⁻², the highest chemical oxygen demand (COD) removal efficiency is 95%, and the maximum Coulombic efficiency is 67%. Compared with other reported studies, the CNT/carbon cloth composite electrode has demonstrated high potential for the use of MFC.     

Optimizing energy harvest in wastewater treatment by combining anaerobic hydrogen producing biofermentor (HPB) and microbial fuel cell (MFC)

This study focused on the optimization of energy harvest from wastewater treatment by integrating two novel biotechnologies: anaerobic hydrogen production and microbial fuel cell (MFC). The simultaneous production of hydrogen and electricity from wastewater was examined at continuous flow at different organic loading rates (OLR) by changing chemical oxygen demand (COD) and hydraulic retention time (HRT). The experimental results showed that the specific hydrogen yield (SHY, mole H₂/mole glucose) increased with the decrease in OLR, and reached at the maximum value of 2.72 mol H₂/mole glucose at the lowest OLR of 4 g/L.d. The effluent from hydrogen producing biofermentor (HPB) was fed to a single chamber MFC (SCMFC), obtaining the highest power density and coulombic efficiency (CE) of 4200 mW/m³ and 5.3%, respectively. The energy conversion efficiency (ECE) increased with OLR and reached the peak value of 4.24% at the OLR of 2.35 g/L.d, but decreased with higher OLR. It was demonstrated that the combination of HPB and MFC improved the ECE and COD removal with the maximum total ECE of 29% and COD removal of 71%. The kinetic analysis was conducted for the HPB-MFC hybrid system. The maximum hydrogen production was projected to be 2.85 mol H₂/mole glucose. The maximum energy recovery and COD removal efficiency from MFC were projected to be 559 J/L and 97%, respectively.     

Innovative multi‐processed N‐doped carbon and Fe3O4 cathode for enhanced bioelectro‐Fenton microbial fuel cell performance

A novel bioelectro‐Fenton microbial fuel cell (BEF‐MFC) cathode has been fabricated by modification of electrode using multi‐processing of nitrogen‐doped carbon (NDC)/nano‐Fe₃O₄ method with the aims of cost‐effectiveness, high oxygen reduction reaction (ORR) efficiency, and power performance enhancement. In this study, BEF‐MFC with carbon cloth (CC) cathode pyrolyzed with NDC‐M100/Fe₃O₄ at 700°C achieved higher ORR activity compared with the commercial Pt/C under same operational conditions. It also exhibited excellent crystalline structure according to high‐resolution transmission electron microscope (HRTEM) analysis. Moreover, using NDCN/Fe₃O₄ can facilitate further Fenton‐like reaction for the treatment of wastewater. Chemical oxygen demand (COD) removal efficiency of the reactor was 78% with maximum power density of 1.57 W/m³ in 216 hours. Thus, an innovative multi‐processing method with feasibility for enhanced wastewater treatment and improved power performance of the MFC was investigated. This can be effectively applied in related alternative energy production techniques and bio‐electrochemical systems in the future.     

Ultrasonic pretreatment of palm oil mill effluent: Impact on biohydrogen production,bioelectricity generation,and underlying microbial communities

Substrate bioavailabity is one of the critical factors that determine the relative biohydrogen (bioH₂) yield in fermentative hydrogen production and bioelectricity output in a microbial fuel cell (MFC). In the present undertaking, batch bioH₂ production and MFC-based biolectricity generation from ultrasonically pretreated palm oil mill effluent (POME) were investigated using heat-pretreated anaerobic sludge as seed inoculum. Maximum bioH₂ production (0.7 mmol H₂/g COD) and COD removal (65%) was achieved at pH 7, for POME which was ultrasonically pretreated at a dose of 195 J/mL. Maximum value for bioH₂ productivity and COD removal at this sonication dose was higher by 38% and 20%, respectively, than unsonicated treatments. In batch MFC experiments, the same ultrasound dose led to reduced lag-time in bioelectricity generation with concomitant 25% increase in bioelectricity output (18.3 W/m³) and an increase of COD removal from 30% to 54%, as compared to controls. Quantitative polymerase chain reaction (qPCR) tests on sludge samples from batch bioH₂ production reflected an abundance of gene fragments coding for both clostridial and thermoanaerobacterial [FeFe]-hydrogenase. Fluorescence in situ hybridization (FISH) tests on sludge from MFC experiments showed Clostridium spp. and Thermoanaerobacterium spp. as the dominant microflora. Results suggest the potential of ultrasonicated POME as sustainable feedstock for dark fermentation-based bioH₂ production and MFC-based bioelectricity generation.