Geração de energia a partir da degradação de óleos residuais de fritura por Shewanella putrefaciens em célula a combustível microbiano

Abstract

Microbial fuel cells (MFC) are electrochemical devices that exploit the ability of some species of microorganisms to use electrodes as final acceptors of electrons in their metabolism. The interest in this technology is associated with the possibility of using different compounds, including domestic and industrial effluents, in the generation of electric energy. In this context, the study of MFC that use residual frying oils (RFO) as substrate gains attention by bringing an alternative both from an environmental and an energetic point of view. The objective of this work was to model the best conditions for the simultaneous degradation of these RFO and electric current generation of a microbial fuel cell inoculated with Shewanella putrefaciens. For this purpose, a factorial and central compound planning (CCP) design was used, in which microbial metabolism was studied under the effects of pH, temperature, medium agitation, oil concentration and time. The experimental data were obtained in a two-chamber MFC, an anode and a cathode, separated by a proton exchange membrane. The anode was inoculated with S. putrefaciens under anaerobic conditions and fed with RFO, while the cathode was fed with tap water and salinized tap water. In the anode, an electrode was used as a graphite cloth with a polypropylene mesh and an aluminum heatsink on the cathode. Both were connected externally by an electrical resistance. During the operation of the system, the anode compartment was operated in batch mode. The results show that in less than two days of operation the current generation had reached a stable value, proving the exoelectrogenic capacity of the bacteria. It was observed that S. putrefaciens did not develop a biofilm on the surface of the electrodes with samples from the University Restaurant (UR), but adhered to the electrode with domestic oil as a substrate, demonstrating a direct mechanism of extracellular electron transfer to establish the electrical contact with The electrode. In general, the mathematical modeling of the degradation of the oils for the simultaneous generation of electric current was possible, requiring further studies of the chemical composition of the oils for the evaluation of the efficiency of the MFC with the chemical parameters, since it was only possible to analyze from the point of electrical parameters. In addition, it was possible to verify that the amount of bacterial colonies does not interfere in the generation of tension, being this one generated of stable form with small cellular concentrations.