Soil Microbial Fuel Cells Research Articles

Microbial Electrochemical-based Biofuel Cell System for Remediation of Oil Contaminated Soil

With the growing problem of oil seepage from gas stations around the world, remediation of oil-contaminated soils is receiving increased attention. Microbial electrochemical techniques have been shown to remove hydrocarbons from soil. Microbial fuel cells (MFC) show a strong potential to immobilize and dissipate contaminants using microorganisms. In this context, this review briefly introduces the conventional methods for remediation of petroleum soil contamination, focusing on the effects of different factors and configurations on the effectiveness of MFC remediation. Compared to traditional remediation methods, applying MFC to petroleum leaks in gas stations has better environmental and economic benefits. It does not require the application of chemicals or ex situ remediation of the soil, which largely reduces the cost and does not cause secondary pollution to the surrounding environment such as soil or atmosphere. In the long term, this technology has a good potential to enhance the remediation effect by changing the applied electric field, soil texture, and petroleum degrading bacteria. In addition, making soil MFC simultaneously achieve combined remediation of petroleum hydrocarbons and other contaminants remains to be studied. Finally, this paper emphasizes that there are few practical applications about MFC site remediation and there is a need to conduct site tests with large scale. If the pilot-scale tests are similar to the laboratory-scale treatment results, the technology will gain more popularity.

In situ degradation of organic pollutants by novel solar cell equipped soil microbial fuel cell.

The soil microbial fuel cell (SMFC) has been widely used for soil remediation for its low cost and being eco-friendly. But low degradation efficiency and high mass transfer resistance limit its performance. This study constructed a solar cell-soil microbial fuel cell (SC-SMFC) with different voltages, which use clean energy to improve system performance. At different voltages, 2.0-V system showed the best performance and the maximum output power increased by 330% compared with SMFC. Moreover, 2.0-V SC-SMFC showed the fastest phenol degradation rate of 14μg·mL-1·d-1 at the concentration of 80μg/mL, which was twice of SMFC. Further increasing the concentration to 320μg/mL, the system showed extremely high concentration limit and degraded 90% within 19days. Under this condition, SC-SMFC still showed excellent cycle stability, with the third-round degrading 90% phenol in 13days. Finally, electrochemical impedance spectroscopy (EIS) mechanism study showed that solar cells can accelerate microbial metabolic process and reduce the internal resistance, in which the 2.0-V system was only 87% of SMFC. In conclusion, SC-SMFC provides a green, low-cost, and convenient method for in situ soil remediation in the future.

Advance in remediated of heavy metals by soil microbial fuel cells: Mechanism and application.

In the past decade, studies on the remediation of heavy metals contaminated soil by microbial fuel cells (MFCs) have attracted broad attention because of the self-generated power and their multifield principles such as the extracellular electron transfer (EET) reduction, electromigration for heavy metals removal. However, given the bio electro-motive power from soil MFCs is weak and fluctuated during the remediation, we need to comprehensively understand the origination of driving force in MFC based on the analysis of the fundamental rationale of ion moving in cells and improve the performance via the appropriate configurations and operations. In this review, we first described the structures of soil MFCs for heavy metals remediation and compared the advantages of different types of configurations. Then, based on the theoretical models of heavy metal migration, enrichment, and reduction in soil MFCs, the optimization of soil MFCs including the length of the remediation area, soil conductivity, control of electrode reaction, and modification of electrodes were proposed. Accordingly, this review contributes to the application of bioelectrochemistry to efficiently remove heavy metals from soils.

Effects of arsenic on bioelectricity output and anode microbial community of soil microbial fuel cells in arsenic–petroleum hydrocarbon‐contaminated soils

AbstractBackgroundHydrocarbon production is a potential emission source of arsenic. Sites contaminated by arsenic and hydrocarbons are common but have received little attention. This study selects soil polluted by petroleum hydrocarbons and arsenic as a matrix to construct soil microbial fuel cells (SMFCs), investigates the effect of arsenic on the performance of the SMFCs, so as to provide basic data for the remediation design of such sites, and thus provides a new technical option for the remediation of organic–inorganic‐contaminated sites.ResultsFive groups of SMFCs were tested under different soil arsenic concentrations. When soil arsenic concentration increased from 4.72 to 842.12 mg kg−1, the maximum power density of the SMFCs decreased from 11.3 to 1.8 mW m−2, while the internal resistance increased from 871.4 to 1322.1 Ω. The anode microbial community of the SMFCs aggregated arsenic‐resistant and electric adaptive microbes due to increased arsenic stress, resulting in a decrease in community abundance but an increase in community evenness, which accordingly contributed to the observed change in bioelectricity output. SMFCs did drive the migration of arsenic in soil to the cathode, and this effect decreased with increasing soil arsenic concentration.ConclusionsWith an increase of arsenic, the bioelectricity output of SMFCs was significantly inhibited and the abundance of anode microbial communities decreased. SMFCs did have a cathodic driving effect on arsenic in the soil. This study has practical significance for improving SMFCs in metal/metalloid‐polluted sites, which can provide an optional process for the remediation of organic–metal/metalloid‐polluted sites. © 2022 Society of Chemical Industry (SCI).

Digestate of Fecal Sludge Enhances the Tetracycline Removal in Soil Microbial Fuel Cells

The soil pollution of agricultural lands is increasingly being caused by the widely used antibiotic tetracycline (TC) in the animal husbandry industry. Soil microbial fuel cells (SMFCs) provide a promising strategy for the bioremediation of contaminated soil. However, our current understanding of the bioremediation of TC-contaminated soil by SMFC is still limited. Here, we investigated the influence of fecal sludge (FS) digestate on TC biodegradation efficiency and extracellular electron transfer in SMFCs. The addition of FS digestate was beneficial to electricity generation by SMFC, and thus enhanced the removal efficiency of TC in the SMFC. After 25 days, the SMFC with fecal sludge digestate showed a TC removal efficiency of 64.5%, compared to values of 25.2% and 21.4% observed for a SMFC and an open-circuit SMFC operating without the addition of fecal sludge digestate, respectively. Moreover, the addition of FS digestate was favorable for electricity generation by SMFCs, and the average current density and the maximum power density of the SMFC with fecal sludge digestate were 0.054 A/m3 and 8.85 W/m3, respectively. The enrichment of Desulfuromonas and Pseudomonas in the electrode biofilms might account for their high TC removal efficiency and electricity generation. The SMFC with fecal sludge digestate provides a promising approach for the simultaneous disposal of fecal sludge digestate and the bioremediation of antibiotics-contaminated-soil.

Recent advances in soil microbial fuel cells based self-powered biosensor.

The soil microbial fuel cell (SMFC) is a new device that was originally designed to generate electricity from organic matter in soil using microorganisms. Currently, SMFC based biosensors are emerging as a new and promising research direction for real-time and rapid monitoring of soil quality or soil pollution. Compared to conventional biosensors, SMFC based biosensors exhibit advantages such as low-cost, simple design, in-situ, and long-term self-powering monitoring, which makes it become attractive devices for in-situ long-term soil quality or soil pollution monitoring. Thus, this review aims to provide a comprehensive overview of SMFC based biosensors. In this review, different prototypes of SMFC based biosensors developed in recent years are introduced, the biosensing mechanisms and the roles of SMFC are highlighted, and the emerging applications of these SMFC based biosensors are discussed. Since the SMFC based biosensors are applied in open-air conditions, the effects of different environmental factors on the biosensing response are also summarized. Finally, to further expand the understanding and boost the practical application of the SMFC based biosensors, future perspectives including fundamental mechanism exploration and investigation of the full-scale application are proposed.

Self-contained and integral microbial fuel cells as portable and sustainable energy sources for low-power field devices

BackgroundWith a smaller environmental footprint and longer operation times, Microbial Fuel Cells (MFCs) are now preferred over other renewable technologies for powering small electronic devices in the field. Although with excellent performance in the laboratory, most of MFCs fail for not considering the real field conditions. The purpose of this study is the development of a compact, portable, and self-sustaining format of energy production based on MFC technologies. For this, three MFC configurations, soil MFC, plant MFC and a hybrid-MFC, where a plant and a soil MFC are combined, are assembled in portable power devices and compared. ResultsPlant MFCs provided lower performances (maximum power of 0.6 ± 0.4 µW·cm−2) resulting from a fast and sharp decrease in the anode potential by the flowing of oxygen from the aerenchyma of the plant roots. The performance of soil MFCs was much better (maximum power of 2.0 ± 0.02 µW·cm−2), but not sustained over time (20 days) by the depletion of organic matter. The combination of a soil MFC and a plant in separate compartments of a single container results in a hybrid-MFC with a good performance (maximum power of 2.7 µW·cm−2) which sustained over time for more than 1 month. ConclusionsTherefore, the hybrid self-containing MFCs appears as an ideal alternative for the long-term power supply of low-power field electronic devices, from meteorological sensors or LED lights.How to cite: Uria-Molto N, Costa RD, Nunziata C, et al. Self-contained and integral microbial fuel cells as portable and sustainable energy sources for low-power field devices. Electron J Biotechnol 2022;57. https://doi.org/10.1016/j.ejbt.2022.04.004

Enhanced removal of antibiotics and antibiotic resistance genes in a soil microbial fuel cell via in situ remediation of agricultural soils with multiple antibiotics

Soil microbial fuel cells (MFCs) have been applied for the in situ remediation of soils polluted by single antibiotics. However, the investigation of only single antibiotic pollution has hindered MFC application in real-world soil remediation, where the effects of multiple antibiotics with similar chemical structures on the fate of antibiotics and their corresponding antibiotic resistance genes (ARGs) remain unknown. In this study, antibiotic removal rates, microbial community compositions, metabolite compositions, and ARG abundances were investigated in soil MFCs by adding two commonly used antibiotics (sulfadiazine, SDZ, and sulfamethoxazole, SMX), and comparing them with the addition of only a single antibiotic (SDZ). The antibiotic removal rate was higher in the soil MFC with addition of mixed antibiotics compared to the single antibiotic due to enhanced biodegradation efficiency in both the upper (57.24% of the initial antibiotic concentration) and lower layers (57.07% of the initial concentration) of the antibiotic-polluted soils. Bacterial community diversity in the mixed antibiotic conditions increased, and this likely resulted from the decreased toxicity of intermediates produced during antibiotic biodegradation. Moreover, the addition of mixed antibiotics led to lower risks of ARG release into soil environments, as reflected by higher abundances of host bacteria in the single antibiotic treatment. These results encourage the further development of soil MFC technology for in situ remediation of antibiotic-polluted soils.

Influence of electrode spacing and fed-batch operation on the maximum performance trend of a soil microbial fuel cell

The effect of electrode spacing on a soil microbial fuel cell (MFC) performance under fed-batch treatment with synthetic urine medium (SUM) was investigated at 2, 5, and 8 cm electrode spacing. The electrodes consisted of stainless-steel mesh with coarse layers of carbon-black. The MFCs were fed with SUM when the natural substrate of the medium was exhausted. Initial feeding resulted in 79.6, 108.7, and 103.1% increase in OCV with a proportional percentage increase in power at 2, 5, and 8 cm electrode spacing. Six days after the first feeding, the power was 189.9, 150.7, and 108. 5 mW/m 2 in ascending order of electrode spacing. With more extended treatment, the overall maximum power was obtained at 8 cm spacing. In ascending order of electrode spacing, the highest power (207.92, 263.38, and 271.1 mW/m 2 ) was obtained on days 39, 42, and 93, respectively. The study shows that a larger anode-to-cathode distance requires a longer time for the soil MFC to achieve stable and maximum performance in fed-batch operation. • Soil MFC is optimized for efficient substrate utilization and long-term sustainable power generation. • The effect of long-term fed-batch operation on the MFC performance with varying electrode spacing is investigated. • Soil MFC performance stability is time dependent on electrode spacing under fed-batch operation. • Smaller electrode spacing results in initially better performance due to lower internal resistance. • Larger electrode spacing takes a longer time for the MFC to reach stable and maximum performance.

Electrochemical evaluation of different polymer binders for the production of carbon-modified stainless-steel electrodes for sustainable power generation using a soil microbial fuel cell

In this study, four different polymeric binders - polytetrafluoroethylene (PTFE), two-component epoxy (epoxy), polyvinyl alcohol (PVA), and polyvinylidene fluoride (PVDF) - were used to fabricate a surface-modified stainless-steel electrode. The polymeric binders were used to bond highly conductive carbon-black to a stainless-steel support using a simple fabrication method. The performance of the electrodes in terms of sustainable power generation was tested in a soil microbial fuel cell (SMFC). PTFE showed the fastest and best initial response in no-load operation, reaching a voltage of 370 mV after 7 days, compared to epoxy, PVA, and PVDF, which had 163, 151.7, and -26.7 mV, respectively. Electrochemical measurements showed that epoxy and PVDF have similar redox potential when operated as anode and cathode in an SMFC. Electrochemical evaluation of the long-term performance of the binders showed that epoxy gave 2.2-, 3.4-, and 4.9-fold higher performance than PVDF, PTFE, and PVA, respectively, under intermittent polarization. Although PVDF did not perform well in open circuits, it produced the highest current density in continuous operation with external loads. The most sustained performance was obtained with epoxy. This study has shown that epoxy can be a suitable and eco-friendly substitute for other binders using a simple fabrication method to produce high-performance anodes and cathodes for sustainable bioelectricity generation with a SMFC.

A compact, membrane-less, easy-to-use soil microbial fuel cell: Generating electricity from household rice washing wastewater

The soil microbial fuel cell (SMFC) is a potential technology for bioelectricity generation. An SMFC can convert chemical energy from organic compounds to electrical energy by utilizing exoelectrogenic bacteria existing in the soil. However, the conventional SMFC configuration is hard to set up and inconvenient to use. In addition, rice is one of the main staple foods worldwide, especially in Asia. Rice washing wastewater (RWW) contains various organic compounds with starch, minerals, and vitamins. In this study, a new design of a compact, portable, membrane-less SMFC is proposed. The SMFC is low-cost, easy-to-use, and can generate bioelectricity from abundant household RWW. The SMFC with double carbon-based anode and cathode electrodes was evaluated in muddy soil (total carbon (TC): 85,200 mg/kg, pH: 4.5, and electrical conductivity (EC): 1.36 dS/m) and sandy soil (TC: 1970 mg/kg, pH: 6.6, and EC: 0.01 dS/m) in an incubator at 30 ± 2 ℃. Household RWW was used as a carbon source to feed bacteria in the soil to power the SMFC. For comparison, a control experiment was also conducted, where only water was added to maintain the soil humidity. 15 mL of RWW or water was added to the SMFCs every 48 h. The result showed that when muddy soil was used, the maximum power density of the SMFC with RWW supplied was 485.2 mW/m2, which was 2.4 times higher than the controlled SMFC (202.9 mW/m2). When sandy soil was used, the SMFC with RWW supplied generated the maximum power density of 112 mW/m2, while that of the controlled SMFC was almost zero. These results imply that the proposed SMFC can operate in different types of soil and effectively generate bioelectricity from RWW.

Towards cost-effective soil microbial fuel cell designs

Soil microbial fuel cell (SMFC) is a carbon-neutral energy harvesting technology that exploits the use of electroactive bacteria naturally present in soil to directly generate electricity from organic compounds. Given the simplicity of the system design, SMFCs have great potential to be used for decentralised solutions, especially in areas where access to conventional energy sources is limited. Yet, the high cost to power ratio severely limits the translation of this technology into the market. With the aim of reducing the capital cost, in this study we explore the effect of decreasing the amounts of current collector (CC) on the performance. The results demonstrate that increasing the amount of current collector per surface area of the electrode is not a feasible way of enhancing power densities, as to increase the performance by 20% and 35%, the amount of current collector would have to be increased by 150% and 300%, respectively. This highlights the importance of economic evaluations when optimising the design of a SMFC.

Minimalistic soil microbial fuel cells for bioremediation of recalcitrant pollutants

Increased human, agricultural and industrial activities along with improper waste disposal leads to high levels of soil contamination and accumulation of recalcitrant contaminants in the environment. This global issue demands the use of green and sustainable technologies and soil microbial fuel cells (SMFC) can be a potential solution. We adopted minimalistic designs, based on low-cost carbon materials without any expensive catalyst and membrane, which makes the SMFCs suitable for in-field applications. We investigated the ability of the indigenous microbial population of the soil to use organic contaminants as the source of carbon and the enrichment of the electroactive consortium was monitored over time onto the electrode surface of the SMFCs. We tested performance in soil contaminated with pesticide and soil contaminated with hydrocarbons and compare the microbial enrichment process with respect to the case of non-contaminated soil.

Assessing the effect of the electrode orientation on the performance of soil microbial fuel cells

Soil microbial fuel cells (SMFCs) are a sub-class of the microbial fuel cells family, in which the soil acts as the electrolyte, and as the source of microorganisms and organic fuel. Given the great simplicity of the system design, SMFCs show a promising avenue for energy generation in remote areas. In this study, we investigate the influence that geometrical factors, such as the electrode orientation, have on the electrochemical performance of SMFCs. Two types of electrode orientations: horizontal and vertical, were tested. Additionally, the influence of anode and cathode immersion in soil was explored too. Our results demonstrate that vertical positioning of the cathode in soil is not a viable option. The increase in cathodic immersion leads to a more rapid performance decay, attributed to more anaerobic conditions along soil’s depth. The increase in anode immersion has a positive effect on the evolution of the negative electrode potential. However, with the increase in electrode spacing, the performance drops due to a greater internal resistance.

Towards effective energy harvesting from stacks of soil microbial fuel cells

The 2050 net-zero carbon target can only be achieved with renewable energy solutions that can drastically reduce carbon emissions. Soil microbial fuel cells (SMFCs) have significant potential as a low-cost and carbon-neutral energy conversion technology. Finding the most practical and energy efficient strategy to operate SMFCs is crucial for transitioning this technology from the lab to field implementations. In this study, an innovative self-sustaining and model-based energy harvesting strategy was developed and tested for the first time on SMFC stacks. The model, based on a first-order equivalent electrical circuit (EEC), enables real-time and continuous maximum power point tracking, without the need for offline analysis of electrochemical parameters. Power extraction from the SMFCs to fully charge a 3.6 V NiMH battery, was carried out for 24 h: the longest test duration reported so far on biological fuel cells for such energy harvesting strategy. A novel second-order EEC was also proposed to better describe the electrical dynamics of the SMFC. Our results provide important advances on both accurate model-based electrochemical parameter identification techniques and maximum power point tracking algorithms, for optimal energy extraction from SMFCs. Consequently, this study paves the way for successful implementations of SMFCs towards viable green energy solutions. • Self-sustaining, model-based energy harvesting strategy for SMFC stacks. • Tailored equivalent electrical circuit for real-time maximum power point tracking. • Performance demonstrated over continuous operation.

Anode materials for soil microbial fuel cells: Recent advances and future perspectives

The employment of soil microbial fuel cells (SMFCs) has become popular recently due to it's dual properties of energy production and soil pollutants treatments. In SMFCs, the main problem is to attract the exoelectrogens to the anode in solid medium rather than in aqueous medium of MFCs. So, the subsequent research should focus on developing anode materials that can not only promote the aggregation of exoelectrogens, but also cost-effective, and so as to facilitate the removal of pollutants from contaminated soils and the power generation for low energy accessories. Recent studies have reported that the modification of traditional anode materials makes the SMFCs to obtain excellent performance, especially the use of renewable raw materials. This review summarizes the advancements of biochar, metals, graphene (Gr), carbon nanotubes (CNTs) and their derivatives as anode materials in SMFCs. Furthermore, the performance improvements of SMFCs by using the novel or possible future anode materials in the removal of pollutants and shifting of bacterial community were described. Finally, the future trends of anode materials for SMFCs were prospected. Novelty statement The short of comprehensive review on the anodic materials limited the research and application of SMFCs. This work not just summarized the current used anodic materials, but also highlighted the possible future anodic materials, which should be helpful for comprehensive understanding and be beneficial to advance future research on SMFCs.

Simultaneous removal of copper and biodegradation of BDE-209 with soil microbial fuel cells

The microbial fuel cells (MFCs) were developed in the present study to remove copper (Cu) and decabromodiphenyl ether (BDE-209) from an artificially contaminated soil. The performance of electricity generation, BDE-209 degradation and Cu removal were investigated. Soil enzyme activity, BDE-209 mineralization and microbial community structures were analyzed. Experimental results showed that the removal of BDE-209 and Cu was effectively enhanced by the application of soil MFCs. After 60-day MFC operation, total Cu was removed by 69.2%, 66.4% and 62.5% for an initial Cu content of 250, 500 and 1000 mg/kg, respectively. More than 80% Cu removed was transformed to pure copper and deposited on the cathode plates. Soil enzyme activity and BDE-209 removal (85.5%) were both highest in the case of 500 mg/kg Cu. Genomic sequencing results indicates that electrogenic and debromination bacteria survived together in the soil MFCs. The MFC operation promoted the growth and reproduction of electrogenic bacteria. These results demonstrate that the soil MFCs can be employed as a durable and effective approach for detoxicating organic-metal co-contaminated soil.

Organic matter composition, BaP biodegradation and microbial communities at sites near and far from the bioanode in a soil microbial fuel cell

Bioanodes in a soil microbial fuel cell (SMFC) can serve as sustainable electron acceptors in microbial metabolism processes; thus, SMFCs are considered a promising in situ bioremediation technology. Most related studies have focused on the removal efficiency of contaminants. Relatively few efforts have been made to comprehensively investigate the organic matter composition and biodegradation metabolites of organic contaminants and microbial communities at various distances from the bioanode. In this study, the level and composition of dissolved organic matter (DOM), biodegradation metabolites of benzo[a]pyrene (BaP), and microbial communities at two sites with different distances (S1cm and S11cm) to the bioanode were investigated in an SMFC. The consumption efficiency of dissolved organic carbon (RDOC) and removal efficiency of BaP (RBaP) at S1cm were slightly higher than those at S11cm after 100 days (RDOC 47.82 ± 5.77% at S1cm and 44.98 ± 10.76% at S11cm; RBaP 72.52 ± 1.88% at S1cm and 68.50 ± 4.34% at S11cm). More fulvic acid-like components and more low-molecular-weight metabolites (indicating a higher biodegradation degree) of BaP were generated at S1cm than at S11cm. The microbial community structures were similar at the two sites. Electroactive bacteria (EAB) and some polycyclic aromatic hydrocarbon degraders were both enriched at the bioanode. Energy metabolism at the bioanode could be upregulated to generate more adenosine triphosphate (ATP). In conclusion, the bioanode could modulate the metabolic pathways in the adjacent soil by strengthening the contact between the EAB and BaP degraders, and providing more ATP to the BaP degraders.

A Novel Design Portable Plugged-Type Soil Microbial Fuel Cell for Bioelectricity Generation

Soil microbial fuel cells (SMFCs) are a promising cost-effective power source for on-demand electricity generation applications. So far, reported SMFC configurations are usually bulky and hard to setup. In this study, a low-cost portable plugged-type SMFC (PSMFC) was designed and fabricated for on-demand micropower generation. The PSMFC can be activated just by plugging into natural wet soil, which is easy to access in the natural condition. The PSMFC uses carbon-based electrodes for cost-effectiveness. After setting the PSMFC into the soil to activate, it started to produce electricity after 1 h and reached the power density of 7.3 mW/m2 after 48 h. The proposed PSMFC can potentially generate electricity for remote sensors or soil sensing systems.

Microbial fuel cells for a soil-based green energy conversion system

This paper presents technological aspects, operating principle and scientific applications of microbial fuel cells (MFCs) for a soil-based green energy conversion system. MFC provides a likely low cost, a highly efficient and renewable energy-producing alternative to conventional energy resources. Only a few biosensors MFC have been used practically, providing current for low power devices. To further improve the MFC technology, an understanding of the limitations and microbiology of these systems are required. Some researchers are uncovering that the importance of the MFC technology is not only the production of electricity but the ability of electrode associated microbes to degrade wastes and toxic chemicals. This paper provides a platform to explore the possibilities of generating renewable power using biomass and the working principle of the MFC technology with its applications. The soil microbial fuel cell (SMFC) technology is also implemented in the soil for green electricity generation.