The Influence of Energy Harvesting Strategies on Performance and Microbial Community for Sediment Microbial Fuel Cells

Abstract

Sediment microbial fuel cells (SMFCs) are being developed as potential energy sources where remote sensing and monitoring would be useful. Several energy harvesting techniques for SMFCs have emerged, but effects of these different strategies on startup, performance, and microbial community are not well understood. We investigated these effects by comparing a continuous energy harvesting (CEH) strategy with an intermittent energy harvesting (IEH) strategy. During startup, IEH systems immediately produced higher power and were cathode limited. CEH systems exhibited a gradual power increase and were anode-limited during startup. Both system types produced similar amounts of steady-state power, 1.5 mW ft −2 (16 mW m −2 ) when optimized. However, an IEH system using unoptimized settings could not be subsequently switched to optimal settings and produce expected power levels. The choice of energy harvester did not appear to significantly affect steady-state community structure. Anodes were dominated by γ-and δ-proteobacteria while α-and γ-proteobacteria dominated cathodes. The results suggest performance and community structure are unaffected by energy harvesting strategy, but that startup conditions influence the initial amount of harvested energy and steady-state performance, suggesting future investigations into optimizing startup of these systems are critical for rapidly generating maximum power. Sediment microbial fuel cells (SMFCs) are currently being explored as persistent energy sources for remote sensors and communications in various environments. [1][2][3][4][5][6][7][8] SMFCs are able to generate electrical current from chemical redox gradients at the sediment-water interface. Specifically, they utilize biologically catalyzed chemical reactions to oxidize organic carbon at the anode in the sediment. [9][10][11] This is typically coupled with oxygen reduction in the water column at a cathode. By putting an electronic load between the anode and cathode, useful energy can be derived to power different payloads.In order to maximize the power output of SMFCs, it is presumed that both microbial community and the energy harvesting systems need to be performing optimally. Several energy harvesting strategies have emerged in literature. Two predominant strategies involve either a potentiostatic operation 12-17 or a capacitor charging operation. 5,7,[18][19][20][21] In SMFC applications, the cell potential -the difference between cathode and anode potentials-can be kept constant manually adjusting the external load or automatically by using electronic feedback control. This potentiostatic method may cause potential oscillations as the correct external load is determined by the feedback control circuit, but generally these can be avoided because the current response of the MFC to load change is quite slow in comparison. The net effect here is that the SMFC cell potentials are considered constant and current is continuously flowing in one direction. Thus, we call this type of strategy "continuous energy harvesting" (CE...

Boosting Microbial Fuel Cell Performance by Combining with an External Supercapacitor: An Electrochemical Study

“…This was not novel since it was shown in different previous works in which MFCs were combined with external SCs. [41][42][43][44][45][46][47][48][49][50][51][52][53] The novelty of this work stays into measuring the parameters of interests such as ESR and capacitance of the single component and the combined systems. These measurements allow understanding that a proper parallel connection enables a synergic interaction between MFC and SC with improved current and pulse energy performance with respect to those of the separate units.…”

“…A successful example of a combination of MFCs with batteries and supercapacitors comes from the robotic field with Gastrobot and EcoBots family . Other practical applications through a combination of supercapacitors and MFCs have also been reported . The different possible combinations of MFC and power management systems are described in detail in a recent review .…”

“…[41][42][43][44] Other practical applications through a combination of supercapacitors and MFCs have also been reported. [45][46][47][48][49][50][51][52][53] The different possible combinations of MFC and power management systems are described in detail in a recent review. [54] Recently, also the capacitive features of MFCs anode [55][56][57][58] and cathode [59][60][61][62][63][64][65][66] electrodes have been explored considering the MFCs electrodes as the electrodes of an internal supercapacitor.…”

Scale up of Microbial Fuel Cell Stack System for Residential Wastewater Treatment in Continuous Mode Operation

“…It is important to remember that the power source of the EHS are living organisms; for this reason the energy quantity that can be harvested and the frequency with which it must be done has to be taken into consideration. The EHS used in this work was a capacitor-based system operated in an intermittent energy harvest (IEH) mode because it has been reported that it is possible to harvest twice as much energy compared to the continuous energy harvest (CEH) mode [7,[40][41][42][43] and prevent voltage reversal in the cells.…”

Bioremediation and Electricity Generation by Using Open and Closed Sediment Microbial Fuel Cells

“…Recently, it was found that toxic metals ions acted as electron acceptors of cathode reduction reaction to enhance power production by being reduced to metallic ionic forms (Li et al, 2017). The high efficiency of SMFC with toxic metals ions reducing cathode was linked with the higher over-potential of oxygen than that of toxic metals ions (Hsu et al, 2017). In the SMFC, toxic metals ions are easily transport to the both sides of cathode and anode, revealing that the impact of toxic metals ions on the SMFC efficiency become more complex due to the abrupt balance among biological effect of toxic metals on the microbes of anode and it’s works as an electron acceptor at the cathode (Chen et al, 2016).…”