Abstract
Development of economical and environment-friendly Microbial Fuel Cells (MFCs) technology should be associated with waste management. However, current knowledge regarding microbiological bases of electricity production from complex waste substrates is insufficient. In the following study, microbial composition and electricity generation were investigated in MFCs powered with waste volatile fatty acids (VFAs) from anaerobic digestion of primary sludge. Two anode sizes were tested, resulting in organic loading rates (OLRs) of 69.12 and 36.21 mg chemical oxygen demand (COD)/(g MLSS∙d) in MFC1 and MFC2, respectively. Time of MFC operation affected the microbial structure and the use of waste VFAs promoted microbial diversity. High abundance of Deftia sp. and Methanobacterium sp. characterized start-up period in MFCs. During stable operation, higher OLR in MFC1 favored growth of exoelectrogens from Rhodopseudomonas sp. (13.2%) resulting in a higher and more stable electricity production in comparison with MFC2. At a lower OLR in MFC2, the percentage of exoelectrogens in biomass decreased, while the abundance of genera Leucobacter, Frigoribacterium and Phenylobacterium increased. In turn, this efficiently decomposed complex organic substances, favoring high and stable COD removal (over 85%). Independent of the anode size, Clostridium sp. and exoelectrogens belonging to genera Desulfobulbus and Acinetobacter were abundant in MFCs powered with waste VFAs.
Highlights
In view of the increasing demand for electricity, sustainable production of electricity from renewable sources by microorganisms is considered an alternative to the generation of energy based on fossil fuels
Independent of the anode size, Clostridium sp. and exoelectrogens belonging to genera Desulfobulbus and Acinetobacter were abundant in Microbial Fuel Cells (MFCs) powered with waste volatile fatty acids (VFAs)
The high share of Methanobacterium sp. reaching 12.7% in MFC2 was unfavorable because methanogenesis may consume up to 26% of all electrons generated in the cell [33]
Summary
In view of the increasing demand for electricity, sustainable production of electricity from renewable sources by microorganisms is considered an alternative to the generation of energy based on fossil fuels. One of the most attractive solutions are Microbial Fuel Cells (MFCs), which use the metabolism of microorganisms to produce electricity by oxidizing organic substances on the anode and transferring the produced electrons to the cathode without using mediators [1,2]. The use of pure acetic acid or its salt in the form of sodium acetate allows for the efficient production of electricity at a high coulombic efficiency [5,6]. To develop economical MFC technology, electricity production should be associated with waste management
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