Change in electrogenic activity of the microbial fuel cell (MFC) with the function of biocathode microenvironment as terminal electron accepting condition: Influence on overpotentials and bio-electro kinetics S. Srikanth, S. Venkata Mohan ⇑ Bioengineering and Environmental Centre (BEEC), CSIR-Indian Institute of Chemical Technology (CSIR-IICT), Hyderabad 500 607, India highlights " Influence of terminal electron acceptor on the electrogenesis of BES was evaluated. " Strong electron acceptor conditions facilitated stable and gradual proton reduction. " Aerobic metabolism at cathode showed higher electrogenesis for longer periods. " Electron transfer resistances were reduced with aerobic metabolism at cathode. " Biocathode application helps in effective utilization of reducing equivalents. article info Article history: Received 28 March 2012 Received in revised form 7 May 2012 Accepted 11 May 2012 Available online 30 May 2012 Keywords: Bio-electrochemical system (BES) Wastewater treatment Mixed consortia Electron discharge Activation overpotential abstract Influence of biocathode microenvironment as terminal electron accepting process (TEAP) on the electro- genic activity of the microbial fuel cell (MFC)/bio-electrochemical system (BES) was evaluated in concur- rence with the internal losses and bio-electro kinetics. Aerobic metabolism as TEAP showed power output (37.5 ± 2.7 mW/m 2 ) for extended time (240 h) over abiotic (42.5 ± 1.5 mW/m 2 ) electron accepting pro- cess. On the contrary, anaerobic metabolism as TEAP showed negligible power output in spite of increased retention time due to the absence of electron acceptor. Presence of strong electron acceptor conditions in aerobic metabolism facilitated gradual and stable reduction of electrons which helped to overcome the activation over potential and other potential losses. Voltammetric and amperometric analysis witnessed higher and sustainable electron discharge against the aerobic metabolism at cathode. Bio-electro kinetic analysis also showed lower Tafel slope and electron transfer co-efficient indicating the positive impact of aerobic metabolism at cathode in decreasing the internal losses. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction The advent of new century has witnessed an unchecked and over exploited use of fossil fuels as well as their depletion which consequently resulted in the alarming environmental pollution with resultant rise in global warming, causing an unusual increase in surface temperature. This has necessitated, more than ever rapid development of bioenergy to solve the looming energy crisis as well as to save the planet from the brink of an environmental catastrophe. Biofuels present an exciting and sustainable alterna- tive to the fossil fuels which can defend the worldwide energy cri- sis and environmental pollution problems. Recently, microbial fuel cell (MFC)/bio-electrochemical system (BES) technology is repre- senting a new and promising biological process for bioenergy generation (Rabaey et al., 2005; Lovley, 2006; Huang et al., 2011). Utilization of wastewater as anodic fuel for electricity gen- eration through the action of biocatalyst makes MFC as a sustain- able technology for energy generation as well as waste management. The concept of MFC has already been well estab- lished in the direction of utilizing wastewater as anodic fuel (Kim et al., 2008; Fornero et al., 2010; Oh et al., 2010; Zhong et al., 2011). However, there still remain certain limitations to overcome for this technology to become an alternative for tradi- tional energy production processes. Potential losses both at cath- ode and anode, non-sustainable power generation for longer periods of time, electron (e  ) discharge (ED) and dynamics of envi- ronmental factors are some of the major concerns which will lead to low e  transfer efficiency (Velvizhi and Venkata Mohan, 2012). Potential losses will decrease the e  transfer (current flow) be- tween the anode and cathode which in turn impend the MFC per- formance. Apart from anode, potential losses also occur at cathode surface due to the overpotentials especially when biocatalyst was 0960-8524/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biortech.2012.05.097 ⇑ Corresponding author. Tel./fax: +91 40 27163159. E-mail address: vmohan_s@yahoo.com (S. Venkata Mohan). Bioresource Technology 119 (2012) 241–251 Contents lists available at SciVerse ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech