矩形微生物燃料电池性能的分析

测试阳极液和阴极液的pH值和电导率的变化情况, 分析微生物燃料电池(MFC)的产电过程和能量利用情况, 为改善MFC的性能提供理论依据。试验结果表明: 随着MFC的运行, 阳极液的pH值和电导率呈现下降的趋势, 阴极液的pH值和电导率呈现上升的趋势, 阴极液的pH值比阳极液的pH值大约高0.30?0.50, 阳极液和阴极液的平均电导率变化不大。MFC稳定运行时, 欧姆内阻为29.69 Ω, 极限电流为2.69 mA, 最大输出功率约为0.8 mW, 对应的内阻约为95.72 Ω。铁氰化钾的质量传输是极限电流的限制性因素。能量分析发现, MFC阳极液中91.1%的葡萄糖被其他微生物消耗, 仅有8.9%的葡萄糖用来发电; 而用来发电的葡萄糖的88.5%的能量转化为其他形式的能量, 仅有11.5%的能量转化为电能。     

Long-term performance of a plant microbial fuel cell with Spartina anglica

The plant microbial fuel cell is a sustainable and renewable way of electricity production. The plant is integrated in the anode of the microbial fuel cell which consists of a bed of graphite granules. In the anode, organic compounds deposited by plant roots are oxidized by electrochemically active bacteria. In this research, salt marsh species Spartina anglica generated current for up to 119 days in a plant microbial fuel cell. Maximum power production was 100 mW m⁻² geometric anode area, highest reported power output for a plant microbial fuel cell. Cathode overpotential was the main potential loss in the period of oxygen reduction due to slow oxygen reduction kinetics at the cathode. Ferricyanide reduction improved the kinetics at the cathode and increased current generation with a maximum of 254%. In the period of ferricyanide reduction, the main potential loss was transport loss. This research shows potential application of microbial fuel cell technology in salt marshes for bio-energy production with the plant microbial fuel cell.     

Electricity generation from synthesis gas by microbial processes: CO fermentation and microbial fuel cell technology

A microbiological process was established to harvest electricity from the carbon monoxide (CO). A CO fermenter was enriched with CO as the sole carbon source. The DGGE/DNA sequencing results showed that Acetobacterium spp. were enriched from the anaerobic digester fluid. After the fermenter was operated under continuous mode, the products were then continuously fed to the microbial fuel cell (MFC) to generate electricity. Even though the conversion yield was quite low, this study proved that synthesis gas (syn-gas) can be converted to electricity with the aid of microbes that do not possess the drawbacks of metal catalysts of conventional methods.     

Long-term performance and microbial community analysis of a full-scale synthesis gas fed reactor treating sulfate- and zinc-rich wastewater

The performance of a full-scale (500 m³) sulfidogenic synthesis gas fed gas-lift reactor treating metal- and sulfate-rich wastewater was investigated over a period of 128 weeks. After startup, the reactor had a high methanogenic activity of 46 Nm³·h⁻¹. Lowering the carbon dioxide feed rate during the first 6 weeks gradually lowered the methane production rate. Between weeks 8 and 93, less than 1% of the hydrogen supplied was used for methanogenesis. Denaturing gradient gel electrophoresis analysis of polymerase chain reaction-amplified 16S rRNA gene fragments showed that the archaeal community decreased in diversity but did not disappear completely. After the carbon dioxide feed rate increased in week 88, the methane production rate also increased, confirming that methane production was carbon dioxide limited. Even though lowering the carbon dioxide feed appeared to affect part of the sulfate-reducing community, it did not prevent achieving the desired rates of sulfate reduction. The average sulfate conversion rate was 181 kg∙h⁻¹ for the first 92 weeks. After 92 weeks, the sulfate input rate was increased and from week 94 to 128, the average weekly sulfate conversion rate was 295 kg·h⁻¹ (SD ± 87). Even higher sulfate conversion rates of up to 400 kg·h⁻¹ could be sustained for weeks 120–128. The long-term performance and stability together with the ability to control methanogenesis demonstrates that synthesis gas fed reactor can be used successfully at full scale to treat metal and sulfate-rich wastewater.     

Greenhouse gas emissions from rice microcosms amended with a plant microbial fuel cell

Methane (CH₄) release from wetlands is an important source of greenhouse gas emissions. Gas exchange occurs mainly through the aerenchyma of plants, and production of greenhouse gases is heavily dependent on rhizosphere biogeochemical conditions (i.e. substrate availability and redox potential). It is hypothesized that by introducing a biocatalyzed anode electrode in the rhizosphere of wetland plants, a competition for carbon and electrons can be invoked between electrical current-generating bacteria and methanogenic Archaea. The anode electrode is part of a bioelectrochemical system (BES) capable of harvesting electrical current from microbial metabolism. In this work, the anode of a BES was introduced in the rhizosphere of rice plants (Oryza sativa), and the impact on methane emissions was monitored. Microbial current generation was able to outcompete methanogenic processes when the bulk matrix contained low concentrations of organic carbon, provided that the electrical circuit with the effective electroactive microorganisms was in place. When interrupting the electrical circuit or supplying an excess of organic carbon, methanogenic metabolism was able to outcompete current generating metabolism. The qPCR results showed hydrogenotrophic methanogens were the most abundant methanogenic group present, while mixotrophic or acetoclastic methanogens were hardly detected in the bulk rhizosphere or on the electrodes. Competition for electron donor and acceptor were likely the main drivers to lower methane emissions. Overall, electrical current generation with BESs is an interesting option to control CH₄ emissions from wetlands but needs to be applied in combination with other mitigation strategies to be successful and feasible in practice.     

Electricity production in membrane-less microbial fuel cell fed with livestock organic solid waste

Two different MFC configurations designed for handling solid wastes as a feedstock were evaluated in batch mode: a single compartment combined membrane-electrodes (SCME) design; and a twin-compartment brush-type anode electrodes (TBE) design (reversed T-shape MFC with two-air cathode) without a proton exchange membrane (PEM). Cattle manure was tested as a model livestock organic solid waste feedstock. Under steady conditions, voltage of 0.38 V was recorded with an external resistance of 470 Ω. When digested anaerobic sludge was used as the seed in the SCME design, a maximum power density of 36.6 mW/m² was recorded. When hydrogen-generating bacteria (HGB) were used as the seed used in the TBE design, a higher power density of 67 mW/m² was recorded.     

High shear enrichment improves the performance of the anodophilic microbial consortium in a microbial fuel cell

In many microbial bioreactors, high shear rates result in strong attachment of microbes and dense biofilms. In this study, high shear rates were applied to enrich an anodophilic microbial consortium in a microbial fuel cell (MFC). Enrichment at a shear rate of about 120 s^?1 resulted in the production of a current and power output two to three times higher than those in the case of low shear rates (around 0.3 s^?1). Biomass and biofilm analyses showed that the anodic biofilm from the MFC enriched under high shear rate conditions, in comparison with that under low shear rate conditions, had a doubled average thickness and the biomass density increased with a factor 5. The microbial community of the former, as analysed by DGGE, was significantly different from that of the latter. The results showed that enrichment by applying high shear rates in an MFC can result in a specific electrochemically active biofilm that is thicker and denser and attaches better, and hence has a better performance.     

Application of biocathode in microbial fuel cells: cell performance and microbial community

Instead of the utilization of artificial redox mediators or other catalysts, a biocathode has been applied in a two-chamber microbial fuel cell in this study, and the cell performance and microbial community were analyzed. After a 2-month startup, the microorganisms of each compartment in microbial fuel cell were well developed, and the output of microbial fuel cell increased and became stable gradually, in terms of electricity generation. At 20 ml/min flow rate of the cathodic influent, the maximum power density reached 19.53 W/m3, while the corresponding current and cell voltage were 15.36 mA and 223 mV at an external resistor of 14.9 Omega, respectively. With the development of microorganisms in both compartments, the internal resistance decreased from initial 40.2 to 14.0 Omega, too. Microbial community analysis demonstrated that five major groups of the clones were categorized among those 26 clone types derived from the cathode microorganisms. Betaproteobacteria was the most abundant division with 50.0% (37 of 74) of the sequenced clones in the cathode compartment, followed by 21.6% (16 of 74) Bacteroidetes, 9.5% (7 of 74) Alphaproteobacteria, 8.1% (6 of 74) Chlorobi, 4.1% (3 of 74) Deltaproteobacteria, 4.1% (3 of 74) Actinobacteria, and 2.6% (2 of 74) Gammaproteobacteria.     

Long-term cathode performance and the microbial communities that develop in microbial fuel cells fed different fermentation endproducts

To better understand how cathode performance and substrates affected communities that evolved in these reactors over long periods of time, microbial fuel cells were operated for more than 1 year with individual endproducts of lignocellulose fermentation (acetic acid, formic acid, lactic acid, succinic acid, or ethanol). Large variations in reactor performance were primarily due to the specific substrates, with power densities ranging from 835 ± 21 to 62 ± 1 mW/m³. Cathodes performance degraded over time, as shown by an increase in power of up to 26% when the cathode biofilm was removed, and 118% using new cathodes. Communities that developed on the anodes included exoelectrogenic families, such as Rhodobacteraceae, Geobacteraceae, and Peptococcaceae, with the Deltaproteobacteria dominating most reactors. Pelobacter propionicus was the predominant member in reactors fed acetic acid, and it was abundant in several other MFCs. These results provide valuable insights into the effects of long-term MFC operation on reactor performance.     

Improvement of a microbial fuel cell performance as a BOD sensor using respiratory inhibitors

Studies were made to improve the performance of a microbial fuel cell (MFC) as a biochemical oxygen demand (BOD) sensor. The signal from MFCs decreased in the presence of electron acceptors of higher redox potential such as nitrate and oxygen. The addition of azide and cyanide did not change the signal in the absence of the electron acceptors. The respiratory inhibitors eliminated the inhibitory effects of the electron acceptors on the current generation from MFCs. Similar results were obtained using oligotrophic MFCs fed with an environmental sample that contained nitrate. The use of the respiratory inhibitors is therefore recommended for the accurate BOD measurement of environmental samples containing nitrate and/or oxygen with an MFC-type BOD sensor.     

Modelling of a microbial fuel cell process

Summary An electrochemical model for a microbial fuel cell process is proposed here. The model was set up on the basis of the experimental results and analysis of biochemical and electrochemical processes. Simulation of the process shows that the model describes the process reasonably well. The analysis of model simulation illustrates how the current output depends on the substrate concentration, mediator concentration and other main variables. The relationship between the current output and over-voltage is revealed from the modelling study.     

Development of a solar-powered microbial fuel cell

Aims: To understand factors that impact solar‐powered electricity generation by Rhodobacter sphaeroides in a single‐chamber microbial fuel cell (MFC). Methods and Results: The MFC used submerged platinum‐coated carbon paper anodes and cathodes of the same material, in contact with atmospheric oxygen. Power was measured by monitoring voltage drop across an external resistance. Biohydrogen production and in situ hydrogen oxidation were identified as the main mechanisms for electron transfer to the MFC circuit. The nitrogen source affected MFC performance, with glutamate and nitrate‐enhancing power production over ammonium. Conclusions: Power generation depended on the nature of the nitrogen source and on the availability of light. With light, the maximum point power density was 790 mW m^?2 (2·9 W m^?3). In the dark, power output was less than 0·5 mW m^?2 (0·008 W m^?3). Also, sustainable electrochemical activity was possible in cultures that did not receive a nitrogen source. Significance and Impact of the Study: We show conditions at which solar energy can serve as an alternative energy source for MFC operation. Power densities obtained with these one‐chamber solar‐driven MFC were comparable with densities reported in nonphotosynthetic MFC and sustainable for longer times than with previous work on two‐chamber systems using photosynthetic bacteria.     

Investigating microbial fuel cell bioanode performance under different cathode conditions

A compact, three‐in‐one, flow‐through, porous, electrode design with minimal electrode spacing and minimal dead volume was implemented to develop a microbial fuel cell (MFC) with improved anode performance. A biofilm‐dominated anode consortium enriched under a multimode, continuous‐flow regime was used. The increase in the power density of the MFC was investigated by changing the cathode (type, as well as catholyte strength) to determine whether anode was limiting. The power density obtained with an air‐breathing cathode was 56 W/m³ of net anode volume (590 mW/m²) and 203 W/m³ (2160 mW/m²) with a 50‐mM ferricyanide‐based cathode. Increasing the ferricyanide concentration and ionic strength further increased the power density, reaching 304 W/m³ (3220 mW/m², with 200 mM ferricyanide and 200 mM buffer concentration). The increasing trend in the power density indicated that the anode was not limiting and that higher power densities could be obtained using cathodes capable of higher rates of oxidation. The internal solution resistance for the MFC was 5–6 Ω, which supported the improved performance of the anode design. A new parameter defined as the ratio of projected surface area to total anode volume is suggested as a design parameter to relate volumetric and area‐based power densities and to enable comparison of various MFC configurations. Published 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Dynamic changes in the microbial community composition in microbial fuel cells fed with sucrose

The performance and dynamics of the bacterial communities in the biofilm and suspended culture in the anode chamber of sucrose-fed microbial fuel cells (MFCs) were studied by using denaturing gradient gel electrophoresis (DGGE) of PCR-amplified partial 16S rRNA genes followed by species identification by sequencing. The power density of MFCs was correlated to the relative proportions of species obtained from DGGE analysis in order to detect bacterial species or taxonomic classes with important functional role in electricity production. Although replicate MFCs showed similarity in performance, cluster analysis of DGGE profiles revealed differences in the evolution of bacterial communities between replicate MFCs. No correlation was found between the proportion trends of specific species and the enhancement of power output. However, in all MFCs, putative exoelectrogenic denitrifiers and sulphate-reducers accounted for approximately 24% of the bacterial biofilm community at the end of the study. Pareto–Lorenz evenness distribution curves extracted from the DGGE patterns obtained from time course samples indicated community structures where shifts between functionally similar species occur, as observed within the predominant fermentative bacteria. These results suggest the presence of functional redundancy within the anodic communities, a probable indication that stable MFC performance can be maintained in changing environmental conditions. The capability of bacteria to adapt to electricity generation might be present among a wide range of bacteria.     

Study of operational performance and electrical response on mediator-less microbial fuel cells fed with carbon- and protein-rich substrates

The inducement of electroactive consortia was carried out in dual-chamber MFCs using acetate-based substrate- and a protein-rich synthetic wastewater in fed-batch mode. The characteristics of these MFCs were then compared. MFCs based on acetate-induced consortia (MFC_Ace) achieved more than twice higher maximum power, and one half of optimal external resistance in comparison to MFCs based on consortia (MFC_Pro) induced by a protein-rich wastewater. Furthermore, these MFCs exhibited various electrical responses even identical substrate being applied. MFC_Ace preferred carbon-neutral substrates, whereas MFC_Pro exhibited better performance on nitrogen rich feedstock. In particular, for glucose–glutamic acid solution with gradually decreased glucose/glutamic acid ratio, MFC_Pro exhibited increasing electrical responses than MFC_Ace. These results suggest that it is possible to optimize the behavior and characteristics of MFC through proper selection of feeding substrate.     

Microbial communities and electrochemical performance of titanium-based anodic electrodes in a microbial fuel cell

Four types of titanium (Ti)-based electrodes were tested in the same microbial fuel cell (MFC) anodic compartment. Their electrochemical performances and the dominant microbial communities of the electrode biofilms were compared. The electrodes were identical in shape, macroscopic surface area, and core material but differed in either surface coating (Pt- or Ta-coated metal composites) or surface texture (smooth or rough). The MFC was inoculated with electrochemically active, neutrophilic microorganisms that had been enriched in the anodic compartments of acetate-fed MFCs over a period of 4 years. The original inoculum consisted of bioreactor sludge samples amended with Geobacter sulfurreducens strain PCA. Overall, the Pt- and Ta-coated Ti bioanodes (electrode-biofilm association) showed higher current production than the uncoated Ti bioanodes. Analyses of extracted DNA of the anodic liquid and the Pt- and Ta-coated Ti electrode biofilms indicated differences in the dominant bacterial communities. Biofilm formation on the uncoated electrodes was poor and insufficient for further analyses. Bioanode samples from the Pt- and Ta-coated Ti electrodes incubated with Fe(III) and acetate showed several Fe(III)-reducing bacteria, of which selected species were dominant, on the surface of the electrodes. In contrast, nitrate-enriched samples showed less diversity, and the enriched strains were not dominant on the electrode surface. Isolated Fe(III)-reducing strains were phylogenetically related, but not all identical, to Geobacter sulfurreducens strain PCA. Other bacterial species were also detected in the system, such as a Propionicimonas-related species that was dominant in the anodic liquid and Pseudomonas-, Clostridium-, Desulfovibrio-, Azospira-, and Aeromonas-related species.     

Effect of nitrogen addition on the performance of microbial fuel cell anodes

Carbon cloth anodes were modified with 4(N,N-dimethylamino)benzene diazonium tetrafluoroborate to increase nitrogen-containing functional groups at the anode surface in order to test whether the performance of microbial fuel cells (MFCs) could be improved by controllably modifying the anode surface chemistry. Anodes with the lowest extent of functionalization, based on a nitrogen/carbon ratio of 0.7 as measured by XPS, achieved the highest power density of 938 mW/m². This power density was 24% greater than an untreated anode, and similar to that obtained with an ammonia gas treatment previously shown to increase power. Increasing the nitrogen/carbon ratio to 3.8, however, decreased the power density to 707 mW/m². These results demonstrate that a small amount of nitrogen functionalization on the carbon cloth material is sufficient to enhance MFC performance, likely as a result of promoting bacterial adhesion to the surface without adversely affecting microbial viability or electron transfer to the surface.     

Microbial community structure elucidates performance of Glyceria maxima plant microbial fuel cell

The plant microbial fuel cell (PMFC) is a technology in which living plant roots provide electron donor, via rhizodeposition, to a mixed microbial community to generate electricity in a microbial fuel cell. Analysis and localisation of the microbial community is necessary for gaining insight into the competition for electron donor in a PMFC. This paper characterises the anode–rhizosphere bacterial community of a Glyceria maxima (reed mannagrass) PMFC. Electrochemically active bacteria (EAB) were located on the root surfaces, but they were more abundant colonising the graphite granular electrode. Anaerobic cellulolytic bacteria dominated the area where most of the EAB were found, indicating that the current was probably generated via the hydrolysis of cellulose. Due to the presence of oxygen and nitrate, short-chain fatty acid-utilising denitrifiers were the major competitors for the electron donor. Acetate-utilising methanogens played a minor role in the competition for electron donor, probably due to the availability of graphite granules as electron acceptors.     

Electricity generation in a microbial fuel cell with a microbially catalyzed cathode

A microbial fuel cell using aerobic microorganisms as the cathodic catalysts is described. By using anaerobic sludge in the anode and aerobic sludge in the cathode as inocula, the microbial fuel cell could be started up after a short lag time of 9 days, generating a stable voltage of 0.324 V (R (ex) = 500 Omega). At an aeration rate of 300 ml min(-1) in the cathode, a maximum volumetric power density of up to 24.7 W m(-3) (117.2 A m(-3)) was reached. This research demonstrates an economic system for recovering electrical energy from organic compounds.