Effect of simple interventions on the performance of a miniature MFC fed with fresh urine.

The aim of the present study is to enhance the performance of a microbial fuel cell (MFC) design by making simple interventions. Specifically, terracotta "t" and mullite "m" ceramics are tested as membranes while carbon veil and carbon cloth are used as electrodes. In the case of "m" cylinders different dimensions are examined (m: ID 30 mm x height 11.5 mm; sm: ID 18 mm x height 18 mm). The units operated continuously with urine as the feedstock. The best performing is the sm type (60-100 µW), followed by the t type (40-80 µW) and the m type (20-40 µW). Polarisation experiments indicated that activated carbon on the anode enhances the power output (t: 423 µW, sm: 288 µW). Similarly, the increase of the surface area and the addition of stainless steel mesh on the cathode improves the power performance for the "sm" and the "t" units. Furthermore, it is shown that the design with the smaller internal diameter, performs better and is more stable through time.

Comparative Study of Different Operation Modes of Microbial Fuel Cells Treating Food Residue Biomass.

Four multiple air-cathode microbial fuel cells (MFCs) were developed under the scope of using extracts from fermentable household food waste (FORBI) for the production of bioelectricity. The operation of the MFCs was assessed in batch mode, considering each cell individually. Τhe chemical oxygen demand (COD) efficiency was relatively high in all cases (>85% for all batch cycles) while the electricity yield was 20 mJ/gCOD/L of extract solution. The four units were then electrically connected as a stack, both in series and in parallel, and were operated continuously. Approximately 62% COD consumption was obtained in continuous stack operation operated in series and 67% when operated in parallel. The electricity yield of the stack was 2.6 mJ/gCOD/L of extract solution when operated continuously in series and 0.7 mJ/gCOD/L when operated continuously in parallel.

Investigation of ceramic MFC stacks for urine energy extraction.

Two ceramic stacks, terracotta (t-stack) and mullite (m-stack), were developed to produce energy when fed with neat undiluted urine. Each stack consisted of twelve identical microbial fuel cells (MFCs) which were arranged in cascades and tested under different electrical configurations. Despite voltage reversal, the m-stack produced a maximum power of 800 µW whereas the t-stack produced a maximum of 520 µW after 62.6 h of operation. Moreover, during the operation, both systems were subject to blockage possibly due to struvite. To the Authors' best knowledge, this is the first time that such a phenomenon in ceramic MFC membranes is shown to be the direct result of sub-optimal performance, which confirms the hypothesis that ceramic membranes can continue operating long-term, if the MFCs produce maximum power (high rate of e- transfer). Furthermore, it is shown that once the ceramic membrane is blocked, it may prove difficult to recover in-situ.

Operation and characterization of a microbial fuel cell fed with pretreated cheese whey at different organic loads.

Electricity production from filter sterilized cheese whey at different organic loads (0.35, 0.7, 1.5, 2.7 and 6.7gCOD/L respectively) was investigated in a two-chamber microbial fuel cell (MFC). The best performance of the cell was observed at the highest concentration of the pretreated (filter sterilized) cheese whey (6.7gCOD/L) corresponding to a maximum power density of approximately 46mW/m(2). Experiments using glucose (0.35gCOD/L) were also performed for comparison reasons. The study of the open-circuit impedance characteristics of the MFC and of the individual electrodes revealed that the open-circuit impedance of the MFC depended to practically the same extent on both the ohmic resistance between the anode and cathode and the overall polarization resistance. The polarization resistance of the MFC decreased significantly under closed-circuit conditions, which in turn implies that the ohmic overpotential is the main contribution to the energy losses in two-chamber MFCs.