11  EP 2 000 000 A1 12  Embodiments of the present invention Figure 1. schematic diagram of the MFC [0065] Figure 2. Schematic diagram of the cathode cham- ber shown in Figure 1 Figure 3. Schematic diagram of the combined elec- trode Figure 6 Illustrate voltage generation. Figure 7. Illustrate cell voltage Figure 8. Illustrate cell voltage Figure 1 illustrate a MFC composed of an anode electrode and a cathode chamber which is sub- mersed into an anaerobic environment, such as a glass reactor. The reactor may be covered by a rub- ber stopper for maintaining the medium in anaerobic condition. The MFC may be warped up in another larger container in which warm water flows from the bottom to the top for controlling the solution temper- ature of the MFC. In an embodiment of the present invention the anode electrode may comprise a 4 cm x 4 cm piece of not wetproofed plain carbon paper and thecathode electrode may comprise a 5 % wet proofed carbon paper (4 cm by 4 cm) whereinone side of the electrode may comprise Pt catalysts. The Pt coated side may be hot pressed with a electrolyte permeable membrane, providing a membrane cath- ode assembly. All metal parts may be covered using e.g. silicon glue. Preferably the distance of the anode and cathode electrode may be approximately 3 cm in the reactor. The magnetic stirring bar may be placed at the bottom of the reactor for mixing the solution. Airmay be provided to the cathode chamber as an oxidant. The electric current between two elec- trodes may be measured by a multimeter with a fixed resistance. Figure 2 illustrate a cathode chamber which may comprise a one nonconductive polycarbonate plate having a square hole of total volume of approximate- ly 16 cm$^{3}$.There are two holes on the top of the cham- ber for e.g. air flow and electrical outlet. Two mem- brane cathode assemblies may be placed on both sides of the cathode chamber, and then the chamber may be sealed with a rubber gasket and stainless steel bolts and nuts. Figure 3 illustrate a MFC as illustrated in Figure 1. In the present figure the anode is in contact with the membrane cathode assembly, forming a combined electrode. Figure 4 illustrate a cathode chamber as illustrated in Figure 2. In the present figure the anode is in con- tact with the membrane cathode assembly. Figure 4. Schematic diagram of the cathode cham- ber shown in Figure 3 Figure 5. Illustrate a situation wherein several MFC’s or combined electrodes are submersed into the same environment. Figure 5 illustrate a number of MFC are to be sub- mersed into a naturally occurring or artificially gen- erated anaerobic environment to generate electrical energy from organic or inorganic matters. Figure 6 Illustrate voltage generation from the mod- ified wastewater containing acetate (1.6 g/L; SCOD = 1694  GLYPH<25> 20 mg/L) with a 470   resistor in the SMFC. No air flow to the cathode chamber between 5 and 12 hr. Figure 7 illustrate cell voltage as a function of time, with a cathode electrode used for several runs of the SCP, SCOD ( ), cell voltage (•) and two electrode potentials (anode:  H ; cathode: K ). Figure 8 illustrate cell voltage as a function of time, after drying out the cathode used in figure 7, SCOD ( ), cell voltage (•) and two electrode potentials (an- ode:  H ; cathode: K ). EXAMPLES Materials and methods Exam configuration and voltage generation Anaerobic environment: [0066] Domestic wastewater was collected after a fine screen process of the Lundtofte Wastewater Treatment Plant (Lyngby, Denmark). The wastewater contained in a glass bottle was first sparged with nitrogen gas and then was placed in a temperature- controlled room at 4 °C prior to being used. Wastewater was used as the anaerobic environment for power generation in the MFC without any additions of nutrients, a phosphate buffer, vitamins, and minerals. For the startup period, acetate was added to wastewater as a fuel at a final concentration of 1.6 g/L. In some tests, wastewater was mixed with a different amount of acetate in order to prepare various chemical oxygen demands (CODs). MFC configuration: [0067] The MFC was composed of an anode electrode and a rectangular cathode chamber placed in a glass reactor (total volume= 600mL, liquid volume= 550 mL), wherein the glass reactor act as an anode electrode chamber. (Figure 6). The reactor containing a medium along with an anode electrode and a cathode chamber was covered by a rubber stopper having several open- ings for liquid and gas samples, air supply to a cathode chamber, a thermometer, and an anode electrode. The 7