Electricity Generation In Microbial Fuel Cells Research Articles

Improved energy recovery from dark fermented cane molasses using microbial fuel cells

A major limitation associated with fermentative hydrogen production is the low substrate conversion efficiency. This limitation can be overcome by integrating the process with a microbial fuel cell (MFC) which converts the residual energy of the substrate to electricity. Studies were carried out to check the feasibility of this integration. Biohydrogen was produced from the fermentation of cane molasses in both batch and continuous modes. A maximum yield of about 8.23 mol H2/kg CODremoved was observed in the batch process compared to 11.6 mol H2/kg CODremoved in the continuous process. The spent fermentation media was then used as a substrate in an MFC for electricity generation. The MFC parameters such as the initial anolyte pH, the substrate concentration and the effect of pre-treatment were studied and optimized to maximize coulombic efficiency. Reductions in COD and total carbohydrates were about 85% and 88% respectively. A power output of 3.02 W/m3 was obtained with an anolyte pH of 7.5 using alkali pre-treated spent media. The results show that integrating a MFC with dark fermentation is a promising way to utilize the substrate energy.

The significance of the initiation process parameters and reactor design for maximizing the efficiency of microbial fuel cells

Microbial fuel cells (MFCs) can be used for electricity generation via bioconversion of wastewater and organic waste substrates. MFCs also hold potential for production of certain chemicals, such as H2 and H2O2. The studies of electricity generation in MFCs have mainly focused on the microbial community formation, substrate effect on the anode reaction, and the cathode's catalytic properties. To improve the performance of MFCs, the initiation process requires more investigation because of its significant effect on the anodic biofilm formation. This review explores the factors which affect the initiation process, including inoculum, substrate, and reactor configuration. The key messages are that optimal performance of MFCs for electricity production requires (1) understanding of the electrogenic bacterial biofilm formation, (2) proper substrates at the initiation stage, (3) focus on operational conditions affecting initial biofilm formation, and (4) attention to the reactor configuration.

Simultaneous sulfide removal and electricity generation with corn stover biomass as co-substrate in microbial fuel cells

Microbial fuel cells (MFCs), representing a promising method to treat combined pollutants with energy recovery, were utilized to remove sulfide and recover power with corn stover filtrate (CSF) as the co-substrate in present study. A maximum power density of 744 mW/m(2) was achieved with sulfide removal of 91% during 72 h operation when the CSF concentrations (mg-COD/l) and the electrolyte conductivity were set at 800 mg/l and 10.06 mS/cm, respectively, while almost 52% COD was removed due to the microbial degradation of CSF to the volatile organic carbons. CSF concentrations and electrolyte conductivities had significant effects on the performance of the MFCs. Simultaneous removals of inorganic pollutant and complex organic compounds with electricity generation in MFCs are reported for the first time. These results provide a good reference for multiple contaminations treatment especially sulfide containing wastewaters based on the MFC technology.

Influence of Cathodal Performance on Electricity Generation of Microbial Fuel Cell with Refinery Oil Wastewater as Fuel

A double-chambered microbial fuel cell (MFC) was constructed to investigate the feasibility of electricity generation using microbial fuel cell with refinery oil wastewater as its fuel and the influence of cathodal performance. Results indicated that refinery oil wastewater could be used as fuel in MFCs to generate electricity; catholyte type could influence the electricity generation of MFCs directly and Fe (Ⅲ)-EDTA was the best choice, voltage generation and stable operational period of which were highest and longest; voltage generation increased following with catholyte concentration linear but had little relation to cathode areas.

Layer-by-layer assembled gold nanoparticles modified anode and its application in microbial fuel cells

Microbial fuel cells (MFCs) as one type of “green” energy source are drawing great attention among researchers. Anode performance is an important factor limiting the power output of MFCs for practical application. In this paper, the gold nanoparticles (Au NPs) modified carbon paper electrode was successfully constructed by layer-by-layer assembly technique for the first time. UV–vis spectroscopy was used to monitor the regular layer growth of the {PEI/Au}10 multilayer. The results of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in Fe(CN)63−/4− solution demonstrated that the Au NPs modified carbon paper electrode exhibited better electrochemical behavior than the bare carbon paper electrode, including relatively high electroactive surface areas, increased electron transfer rate and decreased interfacial electron transfer resistance. A two-chambered MFC equipped with the modified anode achieved a maximum power density of 346mWm−2 and a start-time for the initial maximum stable voltage of 175h, which were respectively 50% higher and 36% shorter than the corresponding values of the MFC with the unmodified anode. All the results indicated that the LBL assembly Au NPs-based modification on the anode was a simple but efficient method to incorporate Au NPs onto carbon paper electrodes and promoted the electricity generation of MFCs.

Electricity generation using p-nitrophenol as substrate in microbial fuel cell

The cell voltage and degradation rate of p-nitrophenol (PNP) were monitored in a two-chambered microbial fuel cell (MFC) system. Degradation metabolites in the anode solution of MFC were analyzed by gas chromatography–mass spectrometry (GC–MS). PNP was used as substrate by the MFC that was inoculated with anaerobic sludge. The results showed that electricity output increased with the PNP concentration increased, the MFC displayed a maximum power density of 1.778 mW m−2 and a maximum PNP degradation rate of 64.69% when PNP was used as a sole substrate. However, the cell voltage and the PNP degradation rate with sodium acetate (402.3 mV and 95.96%) were higher than those fed with glucose (341.9 mV and 83.51%) when glucose and sodium acetate were used as a substrate, respectively. Furthermore, GC–MS analysis showed that the PNP was biodegraded completely after 142 h in the MFC. These results demonstrate that PNP can be used for electricity generation in MFC for practical applications of wastewater treatment.

Bioelectricity production using a new electrode in a microbial fuel cell

Electrode materials play a key role in enhancing the electricity generation in the microbial fuel cell (MFC). In this study, a new material (Ti-TiO(2)) was used as an anode electrode and compared with a graphite electrode for electricity generation. Current densities were 476.6 and 31 mA/m(2) for Ti-TiO(2) and graphite electrodes, respectively. The PCR-DGGE analysis of enriched microbial communities from estuary revealed that MFC reactors were dominated by Shewanella haliotis, Enterococcus sp., and Enterobacter sp. Bioelectrochemical kinetic works in the MFC with Ti-TiO(2) electrode revealed that the parameters by non-linear curve fitting with the confidence bounds of 95% gave good fit with the kinetic constants of η (difference between the anode potential and anode potential giving one-half of the maximum current density) = 0.35 V, K (s) (Half-saturation constant) = 2.93 mM and J (max) = 0.39 A/m(2) for T = 298 K and F = 96.485 C/mol-e(-). From the results observed, it is clear that Ti-TiO(2) electrode is a promising candidate for electricity generation in MFC.

Crumpled graphene particles for microbial fuel cell electrodes

Graphene has a promising role in electrode fabrication/modification for microbial fuel cell (MFC) applications but there is a lack of research on graphene in MFCs. This study has systematically investigated two types of graphene materials with very different morphologies, namely regular graphene (like flat sheets of paper) and crumpled particles (like crumpled paper balls), respectively, to modify anode and cathode electrodes in MFCs. The higher electricity generation with the crumpled graphene particles is attributed to their higher electrical conductivity in the thickness direction, their larger surface area, catalytic activities of oxygen reduction, and the open structure they pack into that facilitates mass transfer of the fuels and ions. The crumpled graphene-modified anode electrode produces the highest maximum power density (3.6Wm−3), twice that of the activated carbon-modified anode electrode (1.7Wm−3). The maximum power densities with the crumpled graphene- and flat graphene-modified cathode electrodes are 3.3Wm−3 and 2.5Wm−3, significantly higher than 0.3Wm−3 with the unmodified carbon cloth, although still lower than a platinum cathode electrode. These results have demonstrated that graphene-based materials, especially the crumpled graphene particles, can be effective electrode modifying materials for improving electricity generation in MFCs.

Evaluation of full-strength paper mill effluent for electricity generation in mediator-less microbial fuel cells

In the search for renewable, sustainable and affordable energy sources, microbial fuel cells (MFCs) offer the advantage of a biological oxidation of pollutants to the direct generation of electricity by microorganisms. We thus examined the biodegradability and suitability of unamended paper mill effluent for power production in MFCs. In addition, an investigation of the response from indigenous waste microbes upon introduction of an exogenous Enterobacter cloacae culture was performed. Unamended effluent alone reached a substrate degradation rate (SDR) of 0.112 kg COD/m 3 day and 29.4 ± 2.4% total chemical oxygen demand (tCOD) removal, the power density peaked at 24 ± 3 mW/m 2 and 47.7% glucose increase at the termination of the reactor cycle after 12 ± 3 days. The introduction of E. cloacae in separate setups lowered electricity generation, but benefited remediation, power density decreased to 13 ± 2 mW/m 2 whereas the SDR increased to 0.257 kg COD/m 3 day. Also, there was 44.1% glucose removal in the presence of E. cloacae . It was concluded that unamended paper mill effluent can fuel electricity generation in MFCs with its concomitant remediation. The addition of E. cloacae to live paper mill effluent may be antagonistic in terms of electricity generation. Key words: Microbial fuel cells, paper mill effluent, bioremediation, substrate degradation rate, wastewater, renewable energy, electricity.

Ammonia inhibition of electricity generation in single-chambered microbial fuel cells

Batch experiments are conducted at various concentrations of initial total ammonia nitrogen (TAN) with acetate as an electron donor to examine the effects of free ammonia (NH 3) inhibition on electricity production in single-chambered microbial fuel cells (MFCs). This research demonstrates that initial TAN concentrations of over 500 mg N L −1 significantly inhibit electricity generation in MFCs. The maximum power density of 4240 mW m −3 at 500 mg N L −1 drastically decreases to 1700 mW m −3 as the initial TAN increases up to 4000 mg N L −1. Nitrite and nitrate analysis confirms that nitrification after complete acetate removal consumes some TAN. Ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) are also inhibited by increasing the initial TAN concentrations. Another batch experiment verifies the strong inhibitory effect of TAN with only small differences between the half-maximum effective concentration (EC 50) for TAN (894 mg N L −1 equivalent to 10 mg N L −1 as NH 3) and optimum TAN conditions; it requires careful monitoring of the TAN for MFCs. In addition, abiotic control experiments reveal that granular activated carbon, which is used as an auxiliary anode material, adsorbs a significant amount of ammonia at each TAN concentration in batch MFCs.

In situ Fenton-enhanced cathodic reaction for sustainable increased electricity generation in microbial fuel cells

This study reports that Fenton's reaction is capable of facilitating cathodic reaction and thus increasing the current output in microbial fuel cells (MFCs). The hydroxyl radicals ( OH) produced via Fenton's reaction are demonstrated to be vital to the enhancement of electricity generation in MFCs. In a two-chamber MFC employing expanded polytetrafluoroethylene (e-PTFE) laminated cloth as a separator, the power output is enhanced approximately four times with Fenton's reaction. However, the enhancement lasts only a short time period due to the rapid consumption of Fenton's reagents. To overcome this problem, a Fe@Fe 2O 3/carbon felt (CF) composite cathode is made, which results in a greater and, more importantly, sustainable power output. In the composite cathode, Fe@Fe 2O 3 functions as a controllably releasing Fenton iron reagent and CF functions as an air-fed cathode to electro-generate H 2O 2. This newly developed MFC with a Fenton system can ensure a continuous high power output, and also provides a potential solution to the simultaneous electricity generation and degradation of recalcitrant contaminants.

Production of Electricity from Acetate or Butyrate Using a Single-Chamber Microbial Fuel Cell

Hydrogen can be recovered by fermentation of organic material rich in carbohydrates, but much of the organic matter remains in the form of acetate and butyrate. An alternative to methane production from this organic matter is the direct generation of electricity in a microbial fuel cell (MFC). Electricity generation using a single-chambered MFC was examined using acetate or butyrate. Power generated with acetate (800 mg/L) (506 mW/m2 or 12.7 mW/ L) was up to 66% higher than that fed with butyrate (1000 mg/L) (305 mW/m2 or 7.6 mW/L), demonstrating that acetate is a preferred aqueous substrate for electricity generation in MFCs. Power output as a function of substrate concentration was well described by saturation kinetics, although maximum power densities varied with the circuit load. Maximum power densities and half-saturation constants were Pmax = 661 mW/m2 and Ks = 141 mg/L for acetate (218 ohms) and Pmax = 349 mW/m2 and Ks = 93 mg/L for butyrate (1000 ohms). Similar open circuit potentials were obtained in using acetate (798 mV) or butyrate (795 mV). Current densities measured for stable power outputwere higher for acetate (2.2 A/m2) than those measured in MFCs using butyrate (0.77 A/m2). Cyclic voltammograms suggested that the main mechanism of power production in these batch tests was by direct transfer of electrons to the electrode by bacteria growing on the electrode and not by bacteria-produced mediators. Coulombic efficiencies and overall energy recovery were 10-31 and 3-7% for acetate and 8-15 and 2-5% for butyrate, indicating substantial electron and energy losses to processes other than electricity generation. These results demonstrate that electricity generation is possible from soluble fermentation end products such as acetate and butyrate, but energy recoveries should be increased to improve the overall process performance.