Renewable and Sustainable Energy Reviews xxx (xxxx) xxx Please cite this article as: Vitor Cano, Renewable and Sustainable Energy Reviews, https://doi.org/10.1016/j.rser.2020.110590 1364-0321/© 2020 Published by Elsevier Ltd. Electricity generation infuenced by nitrogen transformations in a microbial fuel cell: assessment of temperature and external resistance Vitor Cano, Julio Cano, Sabrina C. Nunes, Marcelo A. Nolasco * University of S˜ ao Paulo, School of Arts, Sciences and Humanities, Av. Arlindo B´ ettio, 1000, Sao Paulo, SP, 03828-000, Brazil A R T I C L E INFO Keywords: Bioelectrochemical system Wastewater treatment Granular activated carbon Nitrifcation Thermophilic Sugarcane vinasse ABSTRACT Microbial fuel cells (MFC) generate clean energy from organic wastes. This study reports the development and application of novel lab-scale MFC with granular activated carbon-modifed electrode fed with synthetic sug- arcane vinasse. Biological activity involving nitrogen in the cathode chamber was assessed as a strategy to improve cathode performance under different temperatures (~25, 35 and 55 ◦ C) and external resistance (13 and 300 Ω). High organic matter removal (>90%) was obtained regardless of the condition applied. Nitrifcation occurred in the cathode chamber at temperature up to 35 ◦ C; this resulted in a decrease in pH to <7, which favored the cathode performance. The anode, applied at 35 ◦ C and 55 ◦ C, presented lower internal resistance and more negative potentials; this shows that the temperature reduced the anode overpotentials. The application of 13 Ω external resistance promoted higher electrogen activity, which resulted in coulombic effciency up to 12.6 ± 2.4% against 1.9 ± 0.2% at 300 Ω. The combination of the proposed confguration, operation and electrode materials yielded maximum power density of 41.3 W m 3 , which is higher than values reported by other studies with similar electrode materials, reactor confguration (not stacked) and substrate composition (diversifed). The fndings contribute to the development of scalable renewable energy generation systems based on combination of biochemical and bioelectrochemical processes in wastewater treatment. 1. Introduction Bioelectrochemical systems (BES) are novel technologies that can convert the chemical energy from organic and inorganic wastes into valuable resources [1,2] such as hydrogen [3], metals [4], nutrients [5], methane [6], multi-carbon organic compounds [7], carbon dioxide sequestration [8], and electricity [9]. Microbial fuel cell (MFC) is a BES which uses enzymes and micro- organisms that act as biocatalysts transferring electrons generated in their respiration to an external solid electron acceptor, to convert the chemical energy of a biodegradable substrate directly into electrical energy [10–12]. A typical MFC consists of the following: (i) an anaerobic anode where biochemical reactions are catalyzed by bacteria, producing protons and electrons from the degradation of organic substrates; (ii) an aerated cathode separated by a proton transfer system [13,14]. Using glucose as substrate, the following bioelectrochemical reactions char- acterize the operational mechanism of MFC [15]: Anode: C 6 H 12 O 6 + 6H 2 O → 6CO 2 + 24H + + 24e  E ◦ ’ =0.43 V vs. SHE at pH 7 (1) Cathode: O 2 + 4H + + 4e  → 2H 2 O E ◦ ’ = 0.82 V vs. SHE at pH 7 (2) Over the past decades, several studies reported in the literature have investigated the application of MFCs in a wide range of processes including biosensing, soil bioremediation, water desalination, and wastewater treatment [10,11,16–18]. As the MFC system is capable of using several compounds as fuel, from small organic molecules to polymers, its application for energy extraction in wastewater treatment has drawn considerable attention and interests among researchers in the feld [11,19]. High-strength wastewater generated from industrial and agro- industrial activities is commonly characterized by a high content of organic matter, which may reach between 2000 up to 30,000 mgCOD L 1 [20–23]. Essentially, this means that a great quantity of chemical energy, which would otherwise be lost in conventional wastewater treatment, can potentially be treated and converted into electricity in a MFC system. In this sense, a MFC system has key advantages over techniques traditionally used for wastewater treatment [11,14,24]: (i) it can directly convert organic substrates into electricity, avoiding energy * Corresponding author. E-mail address: mnolasco@usp.br (M.A. Nolasco). Contents lists available at ScienceDirect Renewable and Sustainable Energy Reviews journal homepage: http://www.elsevier.com/locate/rser https://doi.org/10.1016/j.rser.2020.110590 Received 7 April 2020; Received in revised form 23 August 2020; Accepted 18 November 2020