9This work compares the performance of four microbial fuel cells (MFCs) equipped with 10 different cheap electrodic materials during two-month long tests, in which they were 11 operated under the same operating conditions. Despite using sp 2 carbon materials (carbon 12 felt, foam and cloth) as anode in the four MFCs, results demonstrates that there are 13 important differences in the performance, pointing out the relevance of the surface area 14 and other physical characteristics on the efficiency of MFCs. Differences were found not 15 only in the production of electricity but also in the consumption of fuel (acetate) and even 16 in the cathodic consumption of oxygen. Carbon felt was found to be the most efficient 17 anode material whereas the worst results were obtained with carbon cloth. Performance 18 seems to be in direct relationship with the specific area of the anode materials. In 19 comparing the performance of the MFC equipped with carbon felt and stainless steel as 20 cathodes, the later shows the worst performance, which clearly indicates how the cathodic 21 process may become the bottleneck of the MFC performance.22 23 Keywords 24 Microbial fuel cells; anode material; cathode material; carbonaceous materials 25 26 *to whom all correspondence should be addressed: manuel.rodrigo@uclm.es 27 28 29 30 Microbial fuel cells (MFC) are energy conversion devices widely studied over the last 31 decades [1, 2]. Hundreds of papers have been published recently, pointing out the 32 relevance of the topic for the scientific community [3]. Harvesting energy directly from 33 organic matter as electricity is a promising concept, with very interesting results at small 34 scales which, unfortunately, become difficult to be extrapolated in large facilities[4]. The 35 clarification of the mechanisms involved, with a deeper understanding of the complex 36interactions between electrochemistry and biotechnology, is the more important handicap 37 to be overcome in the near future and it justifies the research portfolios related to MFC 38 currently carried out by many research groups [5]. 39 In using mixed cultures in MFC, the microbial culture composition is expected to change 40 and acclimate to the operation conditions applied [6, 7]. In addition to the carbon source 41 and nutrient composition (fuel of the MFC) [8, 9], the values of the solid retention time 42 and temperature [10] are known to be very important, as well as the organic loading rate 43 used[11]. Initially, the electrochemical parameters are expected to show a lower relevance 44 on the performance of the device and almost nil in the microbial composition. In fact, the 45 most important electrochemical input is the choice of the electrode materials[12], because 46 the electrocatalytic properties of these materials influence on the transfer of electrons 47 required to harvest electricity from organic matter and their electric resistance on the 48 voltage vs intensity performance[10]. Obviously, a cheap material exhibiting microbial-49 compatibility and suitabl...

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Four two-compartment microbial fuel cells (MFCs), equipped with the same components except for the membranes, were operated for two months within the same operation conditions, in order to evaluate the effects of the ion exchange membranes (IEM) and the hydraulic retention time (HRT). Results obtained point out that a MFC equipped with Nafion-117 achieves higher current and power densities (829 mA m-2 and 268.37 mW m-2 , respectively) than when the same type of MFC is equipped the cationic exchange membrane Neosepta CMX or the anionic exchange membrane Neosepta AMX, despite both membranes have higher ion exchange capacities. However, no significant differences were found in the wastewater treatment capacities of the different MFCs. In addition, hydraulic retention time (HRT) was found to play an important role in the output energy generation, because low values contributes to minimize the biofouling and, hence, to produce higher current densities.

Three thermally-treated chlorella vulgaris algal suspensions were fed to twocompartment microbial fuel cells (MFCs) for more than three months and performance was monitored in order to determine whether this type of fuel is suitable for MFC and if the thermal treatment of the algae attains any improvement in the efficiency of the system.The algal suspensions were divided into three portions and conditioned thermally at 25, 55 and 95 ºC, before being introduced in each MFCs. Results obtained by the three MFCs

Experimental work carried out in this work has investigated the scale-up of microbial fuel cell (MFC) technology by studying the stacking of single microbial fuel cells, paying attention to the electric and hydraulic connections between each unit. To do this, the performance of three stacks (which were set up with different configurations) was studied for more than three months. The first stack (two hydraulically non-connected cells) was operated for 80 days without any electric connection between them, in order to determine the reproducibility of the performance of a single MFC, and then it was electrically connected in parallel for 20 days to determine if the electricity produced by each single cell was added when they were joined in the stack. The other two stacks (with five and ten cells, hydraulically connected) were connected electrically in series during the first 80 days and in parallel during the last 20 days. The results confirmed that connection in parallel allows higher current intensities and power to be obtained, and that the total electrode surface area attained with the stack is directly related to the production of electricity and to the removal of COD, although not in a linear way.