Exoelectrogenic bacteria that power microbial fuel cells. Implantable, miniaturized microbial fuel cell - The Regents of the University of California. This invention was made with Government support under Grant (contract) No. F30602-00-2-0566 awarded by DARPA. The Government has certain rights to this invention. 1. Field of Invention This invention relates generally to the field of microbial fuel cells and, more particularly, to miniaturized microbial fuel cells suitable for bioimplantation as well as to components and microfabrication techniques related thereto. 2. The use of biochemical activity of microorganisms to generate electricity has been studied by several groups of investigators. Other approaches to microbial electricity generation have included the use of isolated enzymes, typically immobilized on an electrode, rather than living microbes as the source of electromotive force.
The miniature fuel cells operating on chemical fuels without the intervention of a microbe typically require replenishment or reactants and/or catalysts after a shorter interval than would be desirable for an implantable device. Microbe Preparation. Microbial fuel cell. A device that helps generate electricity from human faeces -- researchers from us-based Pennsylvania State University have developed an electricity generator that is fuelled by human waste. The device, the microbial fuel cell (mfc), could prove useful in developing countries. Many of these nations need large-scale waste-processing plants, but find them prohibitively expensive, largely because of the high power requirement. Offsetting this cost by producing electricity while treating waste, could make all the difference, says Bruce Logan, the lead researcher. Human waste mainly contains undigested food comprising organic matter such as carbohydrates, proteins and lipids.
Bacteria in some conventional sewage treatment systems use enzymes to oxidise the organic matter; in this process, electrons (particles that are primary carriers of electricity in solids) are released. The team's device is the first mfc that has been designed to produce electricity by processing human waste. Www.microbialfuelcell.org - Factors limiting the electrical energy generation in MFCs. The microbial conversion of substrates is a key process to generate electricity in BESs. Despite, the microbial nature of the process, it is affected by electrochemical laws and principles which generally results in a lowering of the attainable voltage.
The main electrical principles and the processes governing these losses are briefly described. Subsequently, the various conversions efficiencies are discussed. Due to the positive potential difference (ΔE) between the poles of the MFC, the flow of electrons (I) generates a useful power (P) according to: P = I x ΔE The ratio between the voltage and the current is determined by the external resistance (Rext) according to Ohms law: ΔE = I x Rext When the external resistance is infinite (open circuit conditions) no current flows and the open circuit voltage (OCV) is obtained.
Alternatively, the relation between the cell voltage and the current (density) can be visualized by a polarization curve (Figure I). Benziger, J. He, Z., Minteer, S. Www.microbialfuelcell.org - Anode process: microbial oxidation of substrate. To date, many organic substrates have been investigated as possible energy sources to generate electricity using MFCs. Below, an overview is given of the substrates which have been used to fuel MFCs. The substrates used in MFCs range from carbohydrates (glucose, sucrose, cellulose, starch), volatile fatty acids (formate, acetate, butyrate), alcohols (ethanol, methanol), amino acids, proteins and even inorganic components such as sulfides or acid mine drainages (Cheng et al., 2007, Clauwaert et al., 2008c, He et al., 2005, Heilmann and Logan, 2006, Ishii et al., 2008, Liu et al., 2005b, Logan et al., 2005, Min and Logan, 2004, Rabaey et al., 2003, Rabaey et al., 2006). In order to benchmark new MFC components, reactor designs or operational conditions, acetate is commonly used as a substrate because of its inertness towards alternative microbial conversions (fermentations and methanogensis) at room temperature.
Aelterman, P., Rabaey, K., Clauwaert, P. & Verstraete, W. (2006). Huang, L. Generating Electricity from Wastewater Using a Microbial Fuel Cell. Revised version.doc.