Bioelectricity production and xylene biodegradation through double chamber benthic microbial fuel cells fed with sugarcane waste as a substrate

Effective Exploitation of Sugarcane Byproducts and Industrial Effluents for Strategic Energy Applications: A Review on Recent Developments and Approaches with Special Reference to Microbial Fuel Cells

Apart from its role in agriculture, the contribution of the sugarcane industry and its related sectors toward the global economy is seemingly great. Hence, it is imperative to adopt the maximum possible ways to completely recover the stored chemical energy in sugarcane to generate additional revenue and thereby to ensure the sustainability of sugarcane-related industries by surmounting the regional/seasonal limitations associated with sugarcane cultivation. So, the present Review aims to highlight the importance of sugarcane crops in the global economy by comprehensively discussing the energy value of byproducts and industrial waste generated during the processing of sugarcane. The various possible strategies reported so far for the effective recovery of bioenergy from sugarcane components are discussed with a special emphasis on technologies capable of converting the stored chemical energy into electrical energy or fuel. As the fraction of waste components generated during the harvesting or processing of sugarcane is high, the bioenergy recovery strategies standing close to the "waste-to-energy" concept are the most rewarding ones, suitable for complete bioenergy recovery. Hence, the microbial fuel cell (MFC) technology that offers dual benefits in terms of waste management and power generation is receiving much attention. The status of technological developments in MFCs and the possibilities for developing hybrid technologies through their integration with existing sugar industry waste processing strategies, to further enhance the effective exploitation of the energy value of sugarcane byproducts, are discussed rigorously by focusing on their commercialization possibilities.

Degradation of resorcinol and oxidation of pineapple waste to improve the energy potential through microbial fuel cells

Microbial fuel cells (MFCs) offer a promising approach to remediate organic pollutants while generating energy. Despite significant advancements, generating electrons remains a major challenge for MFCs. This study addresses the electron production challenges in MFCs using pineapple waste as an organic substrate and resorcinol as a pollutant and carbon source. At a constant 1000 Ω external resistance, the maximum power density (PD) achieved was 2.69 mW/m2. Electrochemical studies, including cyclic voltammetry (CV), indicated efficient oxidation and reduction of the substrate, with a specific capacitance of 1.36 × 10⁻⁷ F/g, suggesting gradual biofilm formation. The electrochemical impedance spectroscopy (EIS) findings confirmed efficient electron transport and resorcinol biodegradation reached 84.66%. Bacterial identification revealed that Proteus vulgaris, Hafnia alvei, and Yersinia enterocolitica significantly contributed to resorcinol degradation and energy generation. Optimal MFC operation was observed at pH 7 and temperatures of 25-30 °C. Overall, pineapple substrates, with their polysaccharide composition, maintained stability for 40 days. The study concludes by highlighting future challenges and potential improvements.

Hydrocarbonoclastic Biofilm-Based Microbial Fuel Cells: Exploiting Biofilms at Water-Oil Interface for Renewable Energy and Wastewater Remediation

Microbial fuel cells (MFCs) represent a promising technology for sustainable energy generation, which leverages the metabolic activities of microorganisms to convert organic substrates into electrical energy. In oil spill scenarios, hydrocarbonoclastic biofilms naturally form at the water-oil interface, creating a distinct environment for microbial activity. In this work, we engineered a novel MFC that harnesses these biofilms by strategically positioning the positive electrode at this critical junction, integrating the biofilm's natural properties into the MFC design. These biofilms, composed of specialized hydrocarbon-degrading bacteria, are vital in supporting electron transfer, significantly enhancing the system's power generation. Next-generation sequencing and scanning electron microscopy were used to characterize the microbial community, revealing a significant enrichment of hydrocarbonoclastic Gammaproteobacteria within the biofilm. Notably, key genera such as Paenalcaligenes, Providencia, and Pseudomonas were identified as dominant members, each contributing to the degradation of complex hydrocarbons and supporting the electrogenic activity of the MFCs. An electrochemical analysis demonstrated that the MFC achieved a stable power output of 51.5 μW under static conditions, with an internal resistance of about 1.05 kΩ. The system showed remarkable long-term stability, which maintained consistent performance over a 5-day testing period, with an average daily energy storage of approximately 216 mJ. Additionally, the MFC effectively recovered after deep discharge cycles, sustaining power output for up to 7.5 h before requiring a recovery period. Overall, the study indicates that MFCs based on hydrocarbonoclastic biofilms provide a dual-functionality system, combining renewable energy generation with environmental remediation, particularly in wastewater treatment. Despite lower power output compared to other hydrocarbon-degrading MFCs, the results highlight the potential of this technology for autonomous sensor networks and other low-power applications, which required sustainable energy sources. Moreover, the hydrocarbonoclastic biofilm-based MFC presented here offer significant potential as a biosensor for real-time monitoring of hydrocarbons and other contaminants in water. The biofilm's electrogenic properties enable the detection of organic compound degradation, positioning this system as ideal for environmental biosensing applications.

Synchronous removal of gaseous toluene and benzene and degradation process shifts in microbial fuel cell-biotrickling filter system

Illustrating the biodegradation processes of multi-component volatile organic compounds (VOCs) will expedite the implication of biotechnology in purifying industrial exhaust. Here, performance shifts of microbial fuel cell and biotrickling filter combined system (MFC-BTF) are investigated for removing single and dual components of toluene and benzene. Synchronous removal of toluene (95 %) and benzene (97 %) are achieved by MFC-BTF accompanied with the output current of 0.41 mA. Elevated content of extracellular polymeric substance facilitates the mass transfer of benzene with the presence of toluene. Strains of Bacteroidota, Proteobacteria and Chloroflexi contribute to the removal of dual components VOCs. Empty bed reaction time and the VOCs concentration are the important factors influencing their dissolution in the system. The biodegradation of toluene and benzene proceeds with 2-hydroxymuconic semialdehyde and o-hydroxybenzoic acid as the main intermediates. These results provide a comprehensive understanding of multi-component VOCs removal by MFC-BTF and guide the system design, optimization, and scale-up.

Stimulating bioelectric generation and recovery of toxic metals through benthic microbial fuel cell driven by local sago (Cycas revoluta) waste

Benthic microbial fuel cell (BMFC) is the most promising type of bioelectrochemical approach for producing electrons and protons from natural organic waste. In the present work, a single-chamber BMFC was used, containing sago (Cycas revoluta) waste as the organic feed for microorganisms. The local wastewater was supplemented with heavy metal ions (Pb2+, Cd2+, Cr3+, Ni2+, Co2+, Ag+, and Cu2+) and used as an inoculation source to evaluate the performance of BMFC against the toxic metal remediations. According to the experimental results, the maximum power density obtained was 42.55 mW/m2 within 25 days of the BMFC operation. The maximum remediation efficiency of the metal ion removal from the wastewater was found to be 99.30% (Ag+). The conductive pili-type bacteria species (Acinetobacter species, Leucobacter species, Bacillus species, Proteus species. and Klebsiella pneumoniae) were found in the present study during isolation and identification processes. This study's multiple parameter optimization revealed that pH 7 and room temperature is the best condition for optimal performance. Finally, this study included the mechanism, future recommendations, and concluding remarks.

Treatment of phenolic wastewater by anaerobic fluidized bed microbial fuel cell using carbon brush as anode: microbial community analysis and m-cresol degradation mechanism

Anaerobic fluidized bed microbial fuel cell (AFB-MFC) is a technology that combines fluidized bed reactor and microbial fuel cell to treat organic wastewater and generate electricity. The performance and the mechanism of treating m-cresol wastewater in AFB-MFC using carbon brush as biofilm anode were studied. After 48 h of operation, the m-cresol removal efficiency of AFB-MFC, MAR-AFB (fluidized bed bioreactor with acclimated anaerobic sludge), MAR-FB (ordinary fluidized bed reactor with only macroporous adsorptive resin) and AST (traditional anaerobic sludge treatment) were 95.29 ± 0.67%, 85.78 ± 1.81%, 71.24 ± 1.86% and 70.41 ± 0.32% respectively. The maximum output voltage and the maximum power density of AFB-MFC using carbon brush as biofilm anode were 679.7 mV and 166.6 mW/m2 respectively. The results of high-throughput sequencing analysis indicated the relative abundance of dominant electroactive bacteria, such as Trichococcus, Geobacter, and Pseudomonas, on the anode carbon brushes was higher than that of AST, and also identified such superior m-cresol-degrading bacteria as Bdellovibrio, Thermomonas, Hydrogenophaga, etc. Based on the determination of m-cresol metabolites detected by Gas Chromatography-Mass Spectrometry (GC-MS), the possible biodegradation pathway of m-cresol under anaerobic and aerobic conditions in AFB-MFC was speculated. The results showed that m-cresol was decomposed into formic acid-acetic anhydride and 3-methylpropionic acid under the action of electrochemistry, which is a simple degradation pathway without peripheral metabolism in AFB-MFC.

Simultaneous naphthalene degradation and electricity production in a biowaste-powered microbial fuel cell

Naphthalene is a very common and hazardous environmental pollutant, and its biodegradation has received serious attention. As demonstrated in this study, naphthalene-contaminated wastewater can be biodegraded using a microbial fuel cell (MFC). Furthermore, the potential of MFC for electricity generation appears to be a promising technology to meet energy demands other than those produced from fossil fuels. Nowadays, efforts are being made to improve the overall performance of MFC by integrating biowaste materials for anode fabrication. In this study, palm kernel shell waste was used to produce palm kernel shell-derived graphene oxide (PKS-GO) and palm kernel shell-derived reduced graphene oxide (PKS-rGO), which were then fabricated into anode electrodes to improve the system's electron mobilization and transport. The MFC configuration with the PKS-rGO anode demonstrated greater energy production potential, with a maximum power density of 35.11 mW/m2 and a current density of 101.76 mA/m2, compared to the PKS-GO anode, which achieved a maximum power density of 17.85 mW/m2 and a current density of 72.56 mA/m2. Furthermore, there is simultaneous naphthalene biodegradation with energy production, where the biodegradation efficiency of naphthalene with PKS-rGO and PKS-GO is 85.5%, and 79.7%, respectively. In addition, the specific capacitance determined from the cyclic voltammetry curve revealed a value for PKS-rGO of 2.23 × 10-4 F/g, which is also higher than the value for PKS-GO (1.57 × 10-4 F/g) on the last day of operation. Anodic microbial analysis shows that electrogens thrive in the MFC process. Finally, a comparison with previous literature and the future prospects of the study are also presented.

Bioenergy Generation and Phenol Degradation through Microbial Fuel Cells Energized by Domestic Organic Waste

Microbial fuel cells (MFCs) seem to have emerged in recent years to degrade the organic pollutants from wastewater. The current research also focused on phenol biodegradation using MFCs. According to the US Environmental Protection Agency (EPA), phenol is a priority pollutant to remediate due to its potential adverse effects on human health. At the same time, the present study focused on the weakness of MFCs, which is the low generation of electrons due to the organic substrate. The present study used rotten rice as an organic substrate to empower the MFC's functional capacity to degrade the phenol while simultaneously generating bioenergy. In 19 days of operation, the phenol degradation efficiency was 70% at a current density of 17.10 mA/m² and a voltage of 199 mV. The electrochemical analysis showed that the internal resistance was 312.58 Ω and the maximum specific capacitance value was 0.00020 F/g on day 30, which demonstrated mature biofilm production and its stability throughout the operation. The biofilm study and bacterial identification process revealed that the presence of conductive pili species (Bacillus genus) are the most dominant on the anode electrode. However, the present study also explained well the oxidation mechanism of rotten rice with phenol degradation. The most critical challenges for future recommendations are also enclosed in a separate section for the research community with concluding remarks.

Almukhlifi H, Ahmad A, Yaqoob AA. Dual Role of Sugarcane Waste in Benthic Microbial Fuel to Produce Energy with Degradation of Metals and Chemical Oxygen Demand

One of the most advanced systems of microbial fuel cells is the benthic microbial fuel cell (BMFC). Despite several developments, this strategy still has a number of significant flaws, such as instable organic substrate. Waste material (sugarcane) is used as a substrate in this work to address the organic substrate instability. The process was operated continuously for 70 days. A level of 300 mV was achieved after 33 days of operation, while the degradation efficiencies of Pb (II), Cd (II), and Cr (III) were more than 90%. More than 90% of the removed chemical oxygen demand (COD) was also recorded. The measured power density was 3.571 mW/m2 at 1000 external resistance with 458 internal resistance. This demonstrates that electrons are effectively transported throughout the operation. The Bacillus strains are the most dominant bacterial community on the surface of the anode. This research’s mechanism, which involves metal ion degradation, is also explained. Finally, parameter optimization indicated that pH 7 works efficiently. In addition to that, there are some future perspectives and concluding remarks enclosed.

Heterotrophic anodic denitrification coupled with cathodic metals recovery from on-site smelting wastewater with a bioelectrochemical system inoculated with mixed Castellaniella species

Although Castellaniella species are crucial for denitrification, there is no report on their capacity to carry out denitrification and anode respiration simultaneously in a bioelectrochemical system (BES). Herein, the ability of a mixed inoculum of electricigenic Castellaniella species to perform simultaneous denitrification and anode respiration coupled with cathodic metals recovery was investigated in a BES. Results showed that 500 mg/L NO₃^--N significantly decreased power generation, whereas 100 and 250 mg/L NO₃^--N had a lesser impact. The single-chamber MFCs (SCMFCs) fed with 100 and 250 mg/L NO₃^--N concentrations achieved a removal efficiency higher than 90% in all cycles. In contrast, the removal efficiency in the SCMFCs declined dramatically at 500 mg/L NO₃^--N, which might be attributable to decreased microbial viability as revealed by SEM and CLSM. EPS protein content and enzymatic activities of the biofilms decreased significantly at this concentration. Cyclic voltammetry results revealed that the 500 mg/L NO₃^--N concentration decreased the redox activities of anodic biofilms, while electrochemical impedance spectroscopy showed that the internal resistance of the SCMFCs at this concentration increased significantly. In addition, BES inoculated with the Castellaniella species was able to simultaneously perform heterotrophic anodic denitrification and cathodic metals recovery from real wastewater. The BES attained Cu²⁺, Hg²⁺, Pb²⁺, and Zn²⁺ removal efficiencies of 99.86 ± 0.10%, 99.98 ± 0.014%, 99.98 ± 0.01%, and 99.17 ± 0.30%, respectively, from the real wastewater. Cu²⁺ was bio-electrochemically reduced to Cu⁰ and Cu₂O, whereas Hg⁰ and HgO constituted the Hg species recovered via bioelectrochemical reduction and chemical deposition, respectively. Furthermore, Pb²⁺ and Zn²⁺ were bio-electrochemically reduced to Pb⁰ and Zn⁰, respectively. Over 89% of NO₃^--N was removed from the BES anolyte during the recovery of the metals. This research reveals promising denitrifying exoelectrogens for enhanced power generation, NO₃^--N removal, and heavy metals recovery in BES.

Degradation of Hydroquinone Coupled with Energy Generation through Microbial Fuel Cells Energized by Organic Waste

Microbial fuel cell (MFC) technology has captured the scientific community’s attention in recent years owing to its ability to directly transform organic waste into electricity through electrochemical processes. Currently, MFC systems faces a number of barriers, with one of the most significant being the lack of organic substrate to provide enough energy for bacterial growth and activity. In the current work, rotten rice was utilized as an organic substrate to boost bacterial activity to produce more energy and break down the organic pollutant hydroquinone in an effort to improve the performance of MFCs. There are only a few studies that considered the waste as an organic substrate and simultaneously degraded the organic pollutant vis-à-vis MFCs. The oxidation of glucose derived from rotten rice generated electrons that were transported to the anode surface and subsequently flowed through an external circuit to the cathode, where they were used to degrade the organic pollutant hydroquinone. The results were consistent with the MFC operation, where the 168-mV voltage was generated over the course of 29 days with a 1000 Ω external resistance. The maximum power and current densities were 1.068 mW/m2 and 123.684 mA/m2, respectively. The hydroquinone degradation was of 68%. For the degradation of organic pollutants and the production of energy, conductive pili-type bacteria such as Lacticaseibacillus, Pediococcus acidilactici and Secundilactobacillus silagincola species were identified during biological characterization. Future recommendations and concluding remarks are also included.

Effect of nickel (II) on the performance of anodic electroactive biofilms in bioelectrochemical systems

The impact of nickel (Ni²⁺) on the performance of anodic electroactive biofilms (EABs) in the bioelectrochemical system (BES) was investigated in this study. Although it has been reported that Ni²⁺ influences microorganisms in a number of ways, it is unknown how its presence in the anode of a BES affects extracellular electron transfer (EET) of EABs, microbial viability, and the bacterial community. Results revealed that the addition of Ni²⁺ decreased power output from 673.24 ± 12.40 mW/m² at 0 mg/L to 179.26 ± 9.05 mW/m² at 80 mg/L. The metal and chemical oxygen demand removal efficiencies of the microbial fuel cells (MFCs) declined as Ni²⁺ concentration increased, which could be attributed to decreased microbial viability as revealed by SEM and CLSM. FTIR analysis revealed the involvement of various microbial biofilm functional groups, including hydroxyl, amides, methyl, amine, and carboxyl, in the uptake of Ni²⁺. The presence of Ni²⁺ on the anodic biofilms was confirmed by SEM-EDS and XPS analyses. CV demonstrated that the electron transfer performance of the anodic biofilms was negatively correlated with the various Ni²⁺ concentrations. EIS showed that the internal resistance of the MFCs increased with increasing Ni²⁺ concentration, resulting in a decrease in power output. High-throughput sequencing results revealed a decrease in Geobacter and an increase in Desulfovibrio in response to Ni²⁺ concentrations of 10, 20, 40, and 80 mg/L. Furthermore, the various Ni²⁺ concentrations decreased the expression of EET-related genes. The Ni²⁺-fed MFCs had a higher abundance of the nikR gene than the control group, which was important for Ni²⁺ resistance. This work advances our understanding of Ni²⁺ inhibition on EABs, as well as the concurrent removal of organic matter and Ni²⁺ from wastewater.

The Effect of Different Pretreatment of Chicken Manure for Electricity Generation in Membrane-Less Microbial Fuel Cell

The need for energy resources is growing all the time, which means that more fossil fuels are needed to provide them. People prefer to consume chicken as a source of protein, and this creates an abundance of waste. Thus, microbial fuel cells represent a new technological approach with the potential to generate electricity through the action of electrogenic bacteria toward chicken manure, while reducing the abundance of chicken manure. This study investigated the effect of different pretreatment (thermal, alkaline, and sonication pretreatment) of chicken manure to improve the performance of a membrane-less microbial fuel cell (ML-MFC). Statistical response surface methodology (RSM) through a central composite design (CCD) under a quadratic model was conducted for optimization of the ML-MFC performance focusing on the COD removal efficiency (R2 = 0.8917), biomass (R2 = 0.9101), and power density response (R2 = 0.8794). The study demonstrated that the highest COD removal (80.68%), biomass (7.8539 mg/L), and power density (220 mW/m2) were obtained when the pretreatment conditions were 140 °C, 20 kHz, and pH 10. The polarization curve of the best condition of ML-MFC was plotted to classify the behavior of the ML-MFC. The kinetic growth of Bacillus subtillis (BS) showed that, in treated chicken manure, the specific growth rate µ = 0.20 h−1 and doubling time Td = 3.43 h, whereas, in untreated chicken manure, µ = 0.11 h−1 and Td = 6.08.

Local fruit wastes driven benthic microbial fuel cell: a sustainable approach to toxic metal removal and bioelectricity generation

The present work focused on the utilization of three local wastes, i.e., rambutan (Nephelium lappaceum), langsat (Lansium parasiticum), and mango (Mangifera indica) wastes, as organic substrates in a benthic microbial fuel cell (BMFC) to reduce the cadmium and lead concentrations from synthetic water. Out of the three wastes, the mango waste promoted a maximum current density (87.71 mA/m²) along with 78% and 80% removal efficiencies for Cd²⁺ and Pb²⁺, respectively. The bacterial identification proved that Klebsiella pneumoniae, Enterobacter, and Citrobacter were responsible for metal removal and energy generation. In the present work, the BMFC mechanism, current challenges, and future recommendations are also enclosed.

Utilizing Biomass-Based Graphene Oxide-Polyaniline-Ag Electrodes in Microbial Fuel Cells to Boost Energy Generation and Heavy Metal Removal

Although regarded as environmentally stable, bioelectrochemical fuel cells or, microbial fuel cells (MFCs) continue to face challenges with sustaining electron transport. In response, we examined the performance of two graphene composite-based anode electrodes—graphene oxide (GO) and GO–polymer–metal oxide (GO–PANI–Ag)—prepared from biomass and used in MFCs. Over 7 days of operation, GO energy efficiency peaked at 1.022 mW/m² and GO–PANI–Ag at 2.09 mW/m². We also tested how well the MFCs could remove heavy metal ions from synthetic wastewater, a secondary application of MFCs that offers considerable benefits. Overall, GO–PANI–Ag had a higher removal rate than GO, with 78.10% removal of Pb(II) and 80.25% removal of Cd(II). Material characterizations, electrochemical testing, and microbial testing conducted to validate the anodes performance confirmed that using new materials as electrodes in MFCs can be an attractive approach to improve the electron transportation. When used with a natural organic substrate (e.g., sugar cane juice), they also present fewer challenges. We also optimized different parameters to confirm the efficiency of the MFCs under various operating conditions. Considering those results, we discuss some lingering challenges and potential possibilities for MFCs.