Biological fuel cells are devices capable of directly transforming chemical to electrical energy via electrochemical reactions involving biochemical pathways. Among others, microbial fuel cells (MFCs) use bacterial metabolism at the anode to produce electricity from a wide range of organic substrate. While the idea of harvesting energy produced by MFCs is sprouting, two major issues need to be addressed: low power densities and high manufacturing cost. A typical 1 liter reactor produces no more than 10mW of electrical power, while the costs of the materials to manufacture it is above 30€. High price is caused by the use of nafion and platinum respectively in the membrane and the cathode. A lowcost (and low power density) MFC was built. Earthen membrane replaced nafion and biocathode replaced platinum cathode. Other more common works investigate single chamber air-cathode reactors where the membrane and the cathode are combined. Recent multidisciplinary works on reactor designs, electrodes, substrate and bacterial communities address price and performance issues altogether. In the near future, electrical engineers will contribute by designing adapted power management modules to capture and make use of the harvested energy. The way is long before MFCs can reach the present competitiveness of other renewable energy sources like photovoltaic modules. First applications of MFCs will most likely be to power micro-sensors in remote areas .