Performance of salt‐bridge microbial fuel cell (SB‐MFC) with various microorganism cultures on the generation of electricity from tofu wastewater

Microbial fuel cell (MFC) is a novel kind of fuel cells, it can convert chemical energy from organic pollutant to bioelectricity. In this paper, proton exchange membrane microbial fuel cell (PEMMFC)and salt bridge microbial fuel cell(SBMFC)were compared to examine open circuit voltage, volt-ampere characteristics and coulombic efficiency. Influence of environmental temperature on open circuit voltage of these two MFCs was analyzed. The results show that maximum open circuit voltage of PEMFC is higher than that of SBMFC; performance of PEMMFC is better than that of SBMFC; the coulombic efficiency of PEMFC is higher 36.36% than that of SBMFC. The results are very helpful to understand microbial fuel cells working principle and to increase microbial fuel cell performance.

The wastewater of tofu industries consists of organic compounds and in turn, may affect the environment; therefore, a proper wastewater treatment system is needed. Based on its characteristics, biological treatment is a good method to treat tofu wastewater. One of the biological treatment methods that can be used is Microbial Fuel Cell (MFC), which can reduce the pollutant and at the same time generating low-power electricity. This system utilizes microorganisms as a biocatalyst to degrade organic compounds in the wastewater. This study aimed to examine the performance of Single Chamber MFC (SCMFC) to decrease biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) of the tofu wastewater, as well as to generate electricity. Tofu wastewater was sterilized then filled into the reactor. Microbes that either have been acclimatized or not acclimatized were then added. Bacteria that were used were one of the three consortiums of native microbes of tofu wastewater, namely Escherichia coli, Saccharomycopsis fibuligera, and mixed culture of E. coli and S. fibuligera. Carbon (C) was used as both anode and cathode. We found that the acclimatized mixed culture of E. coli and S. fibuligera showed high BOD5, COD removal after 48 hours at 76.57 and 77.22 %, respectively. It also generated 5.49 mA of current, 757 mV of voltage, and the electrical energy produced was 9.216 x10− 5 kWh. The results suggest that using mixed microorganisms is one of the strategies to improve the electricity generation of MFC. The scale-up of the volume, selection of microorganism cultures, and immobilization could be other strategies for further studies.

<i>Harvesting Energy using Biocatalysts</i>

Tofu is one of the favorable food products that is produced from soybeans. It can be easily produced, contains high nutrition, is cheap, and its raw material is abundant. Unfortunately, a lot of wastewaters are generated during the tofu production process. Generally, tofu wastewater (TWW) contains high organic pollutants which can reduce the water quality when it is directly discharged into the river. This work tries to reduce the organic pollution levels in TWW by using a green technology of microbial fuel cell (MFC) system. The eficiency of TWW treatment was determined based on the reduction of chemical oxygen demand (COD) and biological oxygen demand (BOD) levels, decrement of total suspended solid (TSS) and pH changes. In addition, the amount of the electrical generated by MFC during the TWW treatment was investigated as a value added. The results showed that maximum COD and BOD removals were obtained 60.2 ± 2.0% and 61.5 ± 7.6%, respectively. Whereas, the decrement of TSS was observed at 42.7 ± 1.6%. Moreover, the electrical generation involves the current density the power and of MFC were obtained 389.9 ± 23.0 mA/m2 and 110.8 ± 9.1 mW/m2, respectively. These results indicate the MFC could be used to treat the TWW and generate the electrical power at the same time.

Effect of NaCl on electricity generation, COD removal, reduction in carbohydrate and starch content in dual chambered, salt bridge Microbial Fuel Cells (MFCs) employing raw sago-processing wastewater with an organic load of 14,400 mg COD/l as substrate was evaluated. Four dual chambered MFCs were constructed and the study aimed to find out the impact of addition of NaCl which is carried out for effective MFC performance. Isolation and identification of microbes from initial influent and final effluent was performed using serial dilution, spread plate and selective agar techniques. Interestingly, it was found that the MFC in which NaCl was added to its cathode chamber was best in performance compared to other three MFCs, with a maximum voltage of 603mV and current of 6.03mA. It also documented that the maximum COD removal efficiency of 83% with a total reduction of carbohydrate and starch content from the wastewater was obtained. Utilizing sago wastewater for the production of bioelectricity from MFC technique is considered as a feasible and sustainable process.

Electricity generation using membrane and salt bridge microbial fuel cells

Research on the acquisition of electric energy from waste water industry has been known using the so called salt bridge microbial fuel cell (SBMFC) method. MFC system (microbial fuel cell) is applied to tofu liquid waste management industry which generates two benefits that is reducing contamination of organic material and producing electricity. This study focused on the dual-chamber MFC system that comes as a salt bridge proton exchanger. Variation of the concentration of KMnO 4 as an electrolyte solution is done to observe the effects on the acquisition of electrical energy. Changes in pH, COD, and BOD were also conducted to determine the effectiveness of the MFC in degrading wastewater of tofu. The results obtained in the form of electrical energy with a maximum power density of 11,941 mW/cm 2 at concentration of 0.10 M. The pH value increase of KMnO 4 occurred from 3.5 to 4.0 at concentration of 0.05 M KMnO4. Meanwhile the greatest decreases in COD values are 42.86% and 71.27%, respectively, at KMnO 4 concentration of 0.10 M. Key words: microbial fuel cell, dual-chamber, power density, electrical energy

One major problem of two chamber salt bridge microbial fuel cells (MFCs) is the high resistance offered by the salt bridge to anion flow. Many researchers who have studied and optimized various parameters related to salt bridge MFC, have not shed much light on the effect of salt bridge dimensional parameters on the MFC performance. Therefore, the main objective of this research is to investigate the effect of length and cross sectional area of salt bridge and the effect of solar radiation and atmospheric temperature on MFC current output. An experiment has been designed using Taguchi L9 orthogonal array, taking length and cross sectional area of salt bridge as factors having three levels. Nine MFCs were fabricated as per the nine trial conditions. Trials were conducted for 3 days and output current of each of the MFCs along with solar insolation and atmospheric temperature were recorded. Analysis of variance shows that salt bridge length has significant effect both on mean (with 53.90% contribution at 95% CL) and variance (with 56.46% contribution at 87% CL), whereas the effect of cross sectional area of the salt bridge and the interaction of these two factors is significant on mean only (with 95% CL). Optimum combination was found at 260 mm salt bridge length and 506.7 mm2 cross sectional area with 4.75 mA of mean output current. The temperature and solar insolation data when correlated with each of the MFCs average output current, revealed that both external factors have significant impact on MFC current output but the correlation coefficient varies from MFC to MFC depending on salt bridge dimensional parameters.

Currently, tofu wastewater (TWW) is one of the major environmental issues that must be addressed. When discharged untreated TWW into natural water bodies or soil, it poses a serious threat to the environment. Therefore, effective treatment of TWW is crucial before to disposal. As an advanced bio-electrochemical technology, the microbial fuel cell (MFC) offers a promising approach to reduce pollutants while simultaneously generating electricity. However, the choice of cathode material is crucial for enhancing MFC performance. This study aims to evaluate the performance of an MFC using an SSM-304 cathode with TWW as the target substrate. Several characteristics of TWW including pH, chemical oxygen demand (COD), biological oxygen demand (BOD), total solids (TS), total dissolved solids (TDS), and total suspended solids (TSS), were analyzed before and after MFC treatment. Additionally, the performance of the MFC system was further evaluated based on voltage output (V), current density (J), coulombic efficiency (CE), and MFC efficiency (?MFC). The results show that COD and BOD were reduced by 69.56% and 64.00%, while TS, TDS, and TSS increased by 48.79%, 32.24%, and 45.15%, respectively. The MFC system with SSM-304 produced a voltage of 167 mV, a current density of 267.2 mA/m², a coulombic efficiency of 3.35%, power density of 27.89 mW, and MFC efficiency of 10.43%. Overall, this study demonstrated the potential of MFCs for simultaneous wastewater treatment and energy recovery.

Microbial fuel cell (MFC) technology is a renewable energy solution that offers multiple benefits, including environmental friendliness, direct electricity generation, and wastewater treatment. In wastewater treatment, MFCs convert organic matter into electricity while simultaneously treating wastewater. This study investigated a double-chamber MFC using tofu wastewater and palm oil mill effluent (POME) as substrates. A carbon-based material served as the electrode in a membrane electrode assembly (MEA). The results revealed that the MFC generated voltages of 546 mV and 876 mV for tofu wastewater and POME, respectively. The highest power and current densities measured were 12.45 mW/m² and 25.87 mA/m² for tofu wastewater, and 25.22 mW/m² and 52.8 mA/m² for POME. Furthermore, the chemical oxygen demand (COD) removal efficiencies were 52.7% for tofu wastewater and 56.7% for POME. These findings demonstrate the potential of MFC technology for power generation using tofu wastewater and POME, making it a promising approach for sustainable energy and wastewater treatment.

This research was to determine the genus of bacteria can produce electricity energy used microbial fuel cell series in waste water of tofu and develop module in enviromental mikrobiology concept in basic microbiology among December 2015- May 2016. This research did by 2 phases : isolate microbial fuel cell bakteria in waste water of tofu and development of the module. This research is descriptive, sampling did by purposive sampling, with pick sample in 3 spot there are 2 m,4 m dan 6 m in river bank from source discharges,with considering the existence of tofu waste clumps in the river source waste disposal. Parameter in this research there are test electrical energy, isolate bacteria of microbial fuel cell, and develop the module of basic microbiology. The highest electricity energy in this research observed on the 40 th hour of 67,2 mV,kind of bacteria in microbial fuel cell series in tofu waste water are Entrobacter,Desulfomaculum,Sulfobacterium. Result of this research beused for unit module in enviroment microbiology concept in basic microbiology course. Key words: Microbial Fuel Cell bacteria, tofu waste water,electricity energy, module

Agri‐food waste valorisation

Developing nanocomposite materials based on conducting polymers (CPs) and metal-oxide nanoparticles, which combine redox electrochemistry of CPs with intrinsic properties of nano-scale semiconducting materials, may offer improved microbial fuel cells (MFCs) performances. Polypyrrole (PPY) based nanocomposites were synthesized by chemical oxidative polymerization method and were further used as an anode modifier in salt bridge MFCs. The PPY-based nanocomposites were characterized by X-ray diffraction, Fourier-Transform Infrared (FTIR) spectroscopy, and Scanning Electron Microscopy (SEM). The maximum power density of 16.7 mW/m2, 20.1 mW/m2, and 22.5 mW/m2 were obtained for MFC2-PPY, MFC3-PPY/TiO2 and MFC4-PPY/WO3 respectively, suggesting that modification of the anode with PPY- based nanocomposites is beneficial in the electricity generation of the MFC, and have superior performance as compared to the controller MFC1-CC (11.6 mW/m2).

Currently, acrylic acid is produced at a low yield by the resting cells of Clostridium propionicum with the supplement of extra electron acceptors. As an alternative way, acrylic acid production coupled with electricity generation was achieved by C. propionicum‐based microbial fuel cells (MFCs). Electricity was generated in the salt‐bridge MFCs with cysteine and resazurin in the anode chamber as mediators, and K3Fe(CN)6 as the cathode electron acceptor. Power generation was 21.78 mW/m2 with an internal resistance of 9809 Ω. Cyclic voltammograms indicated the main mechanism of power production was the electron transfer facilitated by mediators in the system. In the salt‐bridge MFC system, 0.694 mM acrylic acid was produced together with electricity generation.

One of the most important challenges for our society is providing powerful devices for renewable energy production. Many technologies based on renewable energy sources have been developed, which represent a clean energy sources that have a much lower environmental impact than conventional energy technologies. Nowadays, many researches focus their attention on the development of renewable energy from solar, water, organic matter and biomass, which represent abundant and renewable energy sources. This research is mainly focused on the development of promising electrode materials and their potential application on emerging technologies such as artificial photosynthesis and microbial fuel cell (MFC). According to desired proprieties of functional materials, this research was focused on two main materials: (1) TiO2 for the development of electrodes for the water splitting reaction due to its demonstrated application potential as photocatalyst material and (2) carbon-based materials for the development of electrodes for MFC. In the first part of the investigation, different TiO2 nanostructures have been studied including: synthesis, characterization and test of TiO2-based materials with the aim of improving the limiting factors of the photocatalytic reaction: charge recombination and separation/migration processes. The photo-catalytic properties of different TiO2 nanostructures were evaluated including: TiO2 nanoparticles (NPs) film, TiO2 nanotubes (NTs) and ZnO@TiO2 core-shell structures. Photo-electrochemical activity measurements and electrochemical impedance spectroscopy analysis showed an improvement in charge collection efficiency of 1D-nanostructures, related to a more efficient electron transport in the materials. The efficient application of both the TiO2 NTs and the ZnO@TiO2 core-shell photoanodes opens important perspectives, not only in the water splitting application field, but also for other photo-catalytic applications (e.g. photovoltaic cells, degradation of organic substances), due to their chemical stability, easiness of preparation and improved transport properties. Additionally, in order to improve the photo-catalytic activity of TiO2 NPs, PANI/TiO2 composite film was synthesized. PANI/TiO2 composite film was successfully applied as anode material for the PEC water splitting reaction showing a significant increase in the photocatalytic activity of TiO2 NPs composite film essentially attributed to the efficient separation of the generated electron and hole pairs. To date, no cost-effective materials system satisfies all of the technical requirements for practical hydrogen production under zero-bias conditions. For this propose, to promote the sustainability of the process, the bias require to conduct PEC water splitting reaction could be powered by MFC systems in which many efforts have been done to improve power and electricity generation as is explained below. In this work, different strategies were also applied in order to improve the performance of anode materials for MFCs. The investigation of commercial carbon-based materials demonstrated that these materials, normally used for other ends are suitable electrodes for MFC and their use could reduce MFC costs and improve the energy sustainability of the process. In addition, to enhance power generation in MFC by using low-cost and commercial carbon-based materials, nitric acid activation (C-HNO3) and PANI deposition (C-PANI) were performed on commercial carbon felt (C-FELT) in order to increase the performance of MFC. Electrochemical determinations performed in batch-mode MFC reveled a strong reduction of the activation losses contribution and an important decrease of the internal resistance of the cell using C-HNO3 and C-PANI of about 2.3 and 4.4 times, respectively, with respect to C-FELT. Additionally, with the aim of solvent different MFC operational problems such as: biofouling, low surface area and large-scale MFC, an innovative three-dimensional material effectively developed and used as anode electrode. The conductive carbon-coated Berl saddles (C-SADDLES) were successfully used as anode electrode in batch-mode MFC. Electrochemical results suggested that C-SADDLES offer a low-cost solution to satisfy either electrical or bioreactor requirements, increasing the reliability of the MFC processes, and seems to be a valid candidate for scaled-up systems and for continuous mode application of MFC technology. In addition, the electrochemical performance and continuous energy production of the most promising materials obtained during this work were evaluated under continuous operation MFC in a long-term evaluation test. Remarkable results were obtained for continuous MFCs systems operated with three different anode materials: C-FELT, C-PANI and C-SADDLES. From polarization curves, the maximum power generation was obtained using C-SADDLES (102 mW•m-2) with respect to C-FELT (93 mW•m-2) and C-PANI (65 mW•m-2) after three months of operation. The highest amount of electrical energy was produced by C-PANI (1803 J) with respect to C-FELT (1664 J) and C-SADDLES (1674 J). However, it is worth to note that PANI activity was reduced during time by the operating conditions inside the anode chamber. In order to demonstrate the wide application potential MFC, this work reports on merging heterogeneous contributions and combining the advantages from three separate fields in a system which enables the ultra-low-power monitoring of a microbial fuel cell voltage status and enables pressure monitoring features of the internal conditions of a cell. The solution is conceived to provide an efficient energy source, harvesting wastewater, integrating energy management and health monitoring capabilities to sensor nodes which are not connected to the energy grid. Finally, this work presented a general concept of the integration of both devices into a hybrid device by interfacing PEC and MFC devices (denoted as PEC-MFC), which is proposed to generate electricity and hydrogen using as external bias the potential produce by microbial fuel cell