Poly iron sulfate flocculant as an effective additive for improving the performance of microbial fuel cells

Bioaugmentation of microbial electrolysis cells with Geobacter sulfurreducens YM18 for enhanced hydrogen production from starch

Double-chamber microbial electrolysis cells (MECs) were operated using starch-based medium as the anolyte and rice paddy-field soil as the anode inoculum, and hydrogen production from the cathode chamber was examined. In order to enhance current generation and hydrogen production, the anode chamber was bioaugmented with Geobacter sulfurreducens strain YM18, and its effects were evaluated based on the performances of non-bioaugmented controls. Results show that the bioaugmented MEC generated threefold greater current during one-month operation and produced sixfold greater amounts of hydrogen than those of the non-bioaugmented control. Quantitative PCR and metabarcoding analyses confirmed successful colonization of anode surfaces with YM18, suggesting the utility of bioaugmentation with YM18 for enhancing the performance of bioelectrochemical systems, including MECs treating biomass wastes.

Removal of microcystin (MC-LR) in constructed wetlands integrated with microbial fuel cells: Efficiency, bioelectricity generation and microbial response

Microcystins (MCs) pollution caused by cyanobacteria harmful blooms (CHBs) has posed short- and long-term risks to aquatic ecosystems and public health. Constructed wetlands (CWs) have been verified as an effective technology for eutrophication but the removal performance for MCs did not achieve an acceptable level. CWs integrated with microbial fuel cell (MFC-CWs) were developed to intensify the nutrient and Microcystin-LR (MC-LR) removal efficiencies in this study. The results indicated that closed-circuit MFC-CWs (T1) exhibited a better NO₃^--N, NH₄⁺-N, TP and MC-LR removal efficiency compared to that of open-circuit MFC-CWs (CK, i.e., traditional CWs). Therein, a MC-LR removal efficiency of greater than 95% was observed in both trials in T1. The addition of sponge iron to the anode layer of MFC-CWs (T2) improved only the NO₃^--N removal and efficiency bioelectricity generation performance compared to T1, and the average effluent MC-LR concentration of T2 (1.14 μg/L) was still higher than the provisional limit concentration (1.0 μg/L). The microbial community diversity of T1 and T2 was simplified compared to CK. The relative abundance of Sphingomonadaceae possessing the degradation capability for MCs increased in T1, which contributed to the higher MC-LR removal efficiency compared to CK and T2. While the relative abundance of electrochemically active bacteria (EAB) (i.e., Desulfuromonadaceae and Desulfomicrobiaceae) in the anode of T2 was promoted by the addition of sponge iron. Overall, this study suggests that integrating MFC into CWs provides a feasible intensification strategy for eutrophication and MCs pollution control.

Enhancing microbial fuel cell performance using anode modified with Fe3O4 nanoparticles

Low electricity generation efficiency is one of the key issues that must be addressed for the practical application of microbial fuel cells (MFCs). Modification of microbial electrode materials is an effective method to enhance electron transfer. In this study, magnetite (Fe₃O₄) nanoparticles synthesized by co-precipitation were added to anode chambers in different doses to explore its effect on the performance of MFCs. The maximum power density of the MFCs doped with 4.5 g/L Fe₃O₄ (391.11 ± 9.4 mW/m²) was significantly increased compared to that of the undoped MFCs (255.15 ± 24.8 mW/m²). The COD removal efficiency of the MFCs increased from 85.8 ± 2.8% to 95.0 ± 2.1%. Electrochemical impedance spectroscopy and cyclic voltammetry tests revealed that the addition of Fe₃O₄ nanoparticles enhanced the biocatalytic activity of the anode. High-throughput sequencing results indicated that 4.5 g/L Fe₃O₄ modified anodes enriched the exoelectrogen Geobacter (31.5%), while control MFCs had less Geobacter (17.4%). Magnetite is widely distributed worldwide, which provides an inexpensive means to improve the electrochemical performance of MFCs.

Electricity generation from rice bran in microbial fuel cells

Background

Rice bran is a by-product of the rice milling process and mostly discarded in Japan. Although many studies have shown that microbial fuel cells (MFCs) are able to generate electricity from organic wastes, limited studies have examined MFCs for generating electricity from rice bran.

Findings

Laboratory-scale single-chamber MFCs were inoculated with paddy field soil and supplied with rice bran for examining electricity generation. Power outputs and microbiome compositions were compared between MFCs containing pure water as the liquid phase (MFC-W) and those containing mineral solution (MFC-M). Polarization analyses showed that both MFCs successfully generated electricity with the maximum power densities of 360 and 520 mW m⁻² (based on the projected area of anode) for MFC-W and MFC-M, respectively. Amplicon-sequencing analyses revealed that Trichococcus and Geobacter specifically occurred in anode biofilms in MFC-W and MFC-M, respectively.

Conclusions

The results suggest that rice bran is a feasible fuel by itself for generating electricity in MFCs.