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

Abstract

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.

Applications of Emerging Bioelectrochemical Technologies in Agricultural Systems: A Current Review

“…As hybrid systems of microbiology and electrochemistry, BESs are able to produce electrical energy or various value-added chemicals via different microorganism-catalyzing redox reactions [8]. Like in other types of electrochemical systems (e.g., batteries), electricity is automatically generated when the redox potential of the reduction half-reaction on the cathode is larger than that of the oxidation half-reaction on the anode.…”

“…[7]. In spite of the various differences, BESs are usually classified according to their application purposes ( Figure 1) and can be divided into microbial fuel cells (MFCs), microbial electrolysis cells (MECs), microbial electrosynthesis (MESs), microbial desalination cells (MDCs), microbial solar cells (MSCs), and enzymatic biofuel cells (EFCs) [8]. The components, mechanisms and applications of these different types of BESs are briefly discussed in the next section.…”

“…In MFCs, the organics in the anode compartment serve as electron donors when they are consumed by exoelectrogens, which produce extracellular electrons that can be collected from the anode. Through an external circuit, the electrons flow to the cathode, thus forming an electric current that can be harnessed for immediate usage or stored for later [8]. The development of air-cathode MFCs has made this technology more feasible to treat wastewater and harvest electricity in practice [13].…”

“…Adapted from MFCs, MECs are capable of producing hydrogen gas (H 2 ), methane (CH 4 ) or other value-added chemicals for indirect energy usage and storage [8]. Theoretically, MECs are able to produce any value-added chemicals regardless of the redox potential differences on the electrodes [18].…”

“…Each type of BESs can be stacked for enhanced overall performance. In addition, MFCs can be used to supply the external electric power required for other BESs such as MECs and MESs [8], thus reducing the energy demand for waste and wastewater treatment while diversifying the added values from resource recovery.…”