Factors Affecting the Effectiveness of Bioelectrochemical System Applications: Data Synthesis and Meta-Analysis

Simeng Li,Gang Chen

doi:10.3390/batteries4030034

Abstract

Microbial fuel cells (MFCs) and microbial electrolysis cells (MECs) are promising bioelectrochemical systems (BESs) for simultaneous wastewater treatment and energy/resource recovery. Unlike conventional fuel cells that are based on stable chemical reactions, these BESs are sensitive to environmental and operating conditions, such as temperature, pH, external resistance, etc. Substrate type, electrode material, and reactor configuration are also important factors affecting power generation in MFCs and hydrogen production in MECs. In order to discuss the influence of these above factors on the performance of MFCs and MECs, this study analyzes published data via data synthesis and meta-analysis. The results revealed that domestic wastewater would be more suitable for treatment using MFCs or MECs, due to their lower toxicity for anode biofilms compared to swine wastewater and landfill leachate. The optimal temperature was 25–35 °C, optimal pH was 6–7, and optimal external resistance was 100–1000 Ω. Although systems using carbon cloth as the electrodes demonstrated better performance (due to carbon cloth’s large surface area for microbial growth), the high prices of this material and other existing carbonaceous materials make it inappropriate for practical applications. To scale up and commercialize MFCs and MECs in the future, enhanced system performance and stability are needed, and could be possibly achieved with improved system designs.

Highlights

Bioelectrochemical systems (BESs) are emerging hybrid systems of biotechnology and electrochemistry that are able to sustainably generate chemical or electrical energy through redox reactions catalyzed by microorganisms [1]
Depending on the mode of applications (Figure 1), BESs can be divided into microbial fuel cells (MFCs), microbial electrolysis cells (MECs), microbial electrosynthesis (MESs), microbial desalination cells (MDCs), and microbial solar cells (MSCs), among which MFCs and MECs are the most studied in the recent years [2]
Like many other anaerobic reactors, MFCs and MECs are sensitive to temperature (Figure 2)

Summary

Introduction

Bioelectrochemical systems (BESs) are emerging hybrid systems of biotechnology and electrochemistry that are able to sustainably generate chemical or electrical energy through redox reactions catalyzed by microorganisms [1]. Like other types of electrochemical cells (e.g., batteries), both MFCs and MECs consist of two electrodes (i.e., an anode and a cathode) that are connected with a conductive wire to form a closed electrical circuit (Figure 1). When the redox potential of the cathode reduction half-reaction (Ecat ) is higher than that of the anode oxidation half-reaction (Ean ), electricity is generated, due to a positive cell potential (Ecell = Ecat − Ean ). External power (i.e., electrolysis) is needed to propel the redox reactions. The biological and electrochemical processes in both types of BESs are uniquely

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