Treatment of fruit waste leachate using microbial fuel cell: Preservation of agricultural environment

Abstract

A microbial fuel cell (MFC) was conceived to low electric power production in parallel to valorization of industrial wastes and environment preservation. It consisted of two compartments separated by polymer Nafion membrane, platinum grid as cathode catalyst and graphite rod inoculated with fruit leachate as bio-anode. Owing to its bio-compatibity with bacterial inoculum and chemical stability, Graphite Carbon (GC) was tested as carrier of biofilm using fruit waste inoculum. The maximum power density harvested with this electrode was about 20 mW.m−2 much greater than that obtained previously with a garden compost inoculum (i.e. 7 mW.m−2). The difference between the two values may be attributed to the bacterial nature of inoculum utilized. Impressively, upon the addition of 6 mL of fuel (sucrose), the soft porous graphite felt GF yielded voltage (260 mV) which was significantly higher than that of the hard smooth solid GC (i.e. 140 mV). This result makes in evidence the effect of adsorption of the electro-active biofilm onto the surface of the electrode. We ascribe therefore the enhanced power density to a more uniform spread out of the electro-active biofilm within the GF matrix, as verified by higher conductivity obtained with four probe method. The results reported herein highlight the importance of assessing the bio-catalytic activity towards the oxidation of the organic substrate to yield renewable low energy. The experimental data and the differences between the bio-anodes GC and GF were discussed in term of electrochemical techniques such as cyclic voltammetry, impedance spectroscopy and four-probe conductivity. Whatever the nature of the bio-anodes, the overall bacterial colonization still yields low values of clean electric energy compared to highly polluted energy obtained with an alkaline fuel cell.