Anode The bacteria live in the anode and convert substrate to carbon dioxide, water, and energy. Various things like glucose and acetate can be used. The bacteria are kept in an oxygen- less environment to promote the flow of electrons through the anode.
Electrical Circuit After leaving the anode, the electrons travel through the circuit. These electrons power the load. The voltage multiplied by the current shows the power.
Exchange Membrane The protons that the bacteria separated from the electrons flows through the exchange membrane. They recombine on the other side. Can be a proton or cation exchange membrane.
Cathode The electrons and protons recombine at the cathode. Oxygen is reduced to water. A platinum catalyst is used so the oxygen is sufficiently reduced.
BEAMR Utilizes electrohydrogenesis, which uses an anaerobic environment to produce pure hydrogen. It uses about one ninth of the energy required by normal electrolysis. It has many different names: Bioelectrochemically assisted microbial reactor Biocatalyzed electrolysis cells Microbial electrolysis cells
Hydrogen Evolution Reaction The bacteria in the anode separate the protons and electrons. This reaction occurs at the cathode, where they recombine to form hydrogen gas.
History M.C. Potter first performed work on the concept in 1911 with E. coli at the University of Durham In 1976 the current design was came into existence by the work of Suzuki
Operating Conditions Function well in mild conditions Operate at 70-100°F
Uses Beer breweries produce biodegradable wastewater, which MFCs clean. Desalinating water Creating fertilizer
Environmental Impact If the variety of substrates is increased, waste can be used to create more energy. Instead of big factory manufacturing, fertilizer for farmers can be created with MFCs and common materials. MFCs can be used to desalinate seawater without burning fossil fuels, although not very efficiently yet.
Efficiency The efficiency varies based on the substrate used, but it can reach very high efficiencies. 91% efficiency has been reached.
Cost Power density = 150 mW/m2 Volume (MFC): 28 x 10^-6 m3 A/V-ratio: 25 m2/m3 Anode surface area (single chamber) = 7 x 10^-4 m2 Power = 0.165 mW Cost of single-chamber fuel cell: (lab-scale) Toray paper (10x10 cm): $ 11 XC-72 (10x10 cm): $65 Others (perspex, glue, wire): $ 25 Total = $ 100 Cost per Watt = $ 600/mW
Future More types of substrate Ammonia-treated anodes
Substrate Currently there is a limit to what can be used as a substrate for the bacteria. Scientists hope to increase these fuel types to include things like sewage and manure.
Ammonia-Treated Anodes Anodes of MFCs are naturally negative in charge. The anodes can be changed to a positive charge by being treated with ammonia. This will make the anode more receptive to the electron transfer from the bacteria. The energy trade-off to produce this might not be worth the increase in production.