In the past 10–15 years, the microbial fuel cell (MFC) technology has captured the attention of the scientific community for the possibility of transforming organic waste directly into electricity through microbially catalyzed anodic, and microbial/enzymatic/abiotic cathodic electrochemical reactions. In this review, several aspects of the technology are considered. Firstly, a brief history of abiotic to biological fuel cells and subsequently, microbial fuel cells is presented. Secondly, the development of the concept of microbial fuel cell into a wider range of derivative technologies, called bioelectrochemical systems, is described introducing briefly microbial electrolysis cells, microbial desalination cells and microbial electrosynthesis cells. The focus is then shifted to electroactive biofilms and electron transfer mechanisms involved with solid electrodes. Carbonaceous and metallic anode materials are then introduced, followed by an explanation of the electro catalysis of the oxygen reduction reaction and its behavior in neutral media, from recent studies. Cathode catalysts based on carbonaceous, platinum-group metal and platinum-group-metal-free materials are presented, along with membrane materials with a view to future directions. Finally, microbial fuel cell practical implementation, through the utilization of energy output for practical applications, is described.

The aim of this study was to compare the performance of three different sizes of microbial fuel cell (MFC) when operated under continuous flow conditions using acetate as the fuel substrate and show how small‐scale multiple units may be best configured to optimize power output. Polarization curve experiments were carried out for individual MFCs of each size, and also for stacks of multiple small‐scale MFCs, in series, parallel and series–parallel configurations. Of the three combinations, the series–parallel proved to be the more efficient one, stepping up both the voltage and current of the system, collectively. Optimum resistor loads determined for each MFC size during the polarization experiments were then used to determine the long‐term mean power output. In terms of power density expressed as per unit of electrode surface area and as per unit of anode volume, the small‐sized MFC was superior to both the medium‐ and large‐scale MFCs by a factor of 1.5 and 3.5, respectively. Based on measured power output from 10 small units, a theoretical projection for 80 small units (giving the same equivalent anodic volume as one large 500 mL unit) gave a projected output of 10 W m⁻³, which is approximately 50 times higher than the recorded output produced by the large MFC. The results from this study suggest that MFC scale‐up may be better achieved by connecting multiple small‐sized units together rather than increasing the size of an individual unit. Copyright © 2008 John Wiley & Sons, Ltd.

The heavy use of chemicals for agricultural, industrial and domestic purposes has increased the risk of freshwater contamination worldwide. Consequently, the demand for efficient new analytical tools for on-line and on-site water quality monitoring has become particularly urgent. In this study, a small-scale single chamber air-cathode microbial fuel cell (SCMFC), fabricated by rapid prototyping layer-by-layer 3D printing, was tested as a biosensor for continuous water quality monitoring. When acetate was fed as the rate-limiting substrate, the SCMFC acted as a sensor for chemical oxygen demand (COD) in water. The linear detection range was 3-164 ppm, with a sensitivity of 0.05 μA mM(-1) cm(-2) with respect to the anode total surface area. The response time was as fast as 2.8 min. At saturating acetate concentrations (COD>164 ppm), the miniature SCMFC could rapidly detect the presence of cadmium in water with high sensitivity (0.2 μg l(-1) cm(-2)) and a lower detection limit of only 1 μg l(-1). The biosensor dynamic range was 1-25 μg l(-1). Within this range of concentrations, cadmium affected only temporarily the electroactive biofilm at the anode. When the SCMFCs were again fed with fresh wastewater and no pollutant, the initial steady-state current was recovered within 12 min.

This communication reports for the first time the direct utilisation of urine in MFCs for the production of electricity. Different conversion efficiencies were recorded, depending on the amount treated. Elements such as N, P, K can be locked into new biomass, thus removed from solution, resulting in recycling without environmental pollution.