NOVELTY - An anode compartment (30) contains an inoculum of soil containing a population of anaerobic microorganisms able to oxidize a fuel comprising biomass. The anode compartment and a cathode compartment (20) are separated by a nonpolymeric proton exchange interface (40). The anode compartment is hermetically sealed, and in gaseous communication with the atmosphere via a conduit (47) and in gaseous communication with the cathode compartment via the nonpolymeric proton exchange interface.    USE - Fuel cell using microorganisms to oxidize fuel.    ADVANTAGE - Converts fuel to electrical energy without combustion of fuel. Attains higher microbial metabolism or efficiency, and higher power output by using thermal insulators for management or retention of heat within the fuel cell.    DETAILED DESCRIPTION - The microorganisms oxidize a fuel when the microorganisms are exposed to temperature of at least 50 degrees Celsius. The nonpolymeric proton exchange interface comprises particles which comprise quartz and/or silica. The biomass, which is continuously fed to the fuel cell (10), comprises animal waste, arises from a compost pile, or arises from a manure pile. A compartment within the fuel cell containing the microorganisms comprises fertilizer which comprises equal parts of nitrogen, phosphorus, and potassium, and further comprises lime, electrically conductive substance, and charcoal. An electrode comprises a non-conductive material and a conductive coating partially surrounding the non-conductive material. The conductive coating comprises graphite, graphite-containing paint, or graphite-containing powder. The non-conductive material comprises cloth, ceramic, non-conducting polymer, polyvinyl chloride, or glass. INDEPENDENT CLAIMS are also included for the following:    (1) a method of oxidizing fuel in fuel cell using microorganisms;    (2) an energy management apparatus for microbial fuel cell; and    (3) a power management method for microbial fuel cell.    DESCRIPTION OF DRAWING(S) - The drawing shows a microbial fuel cell.    Fuel cell (10)    Cathode compartment (20)    Anode compartment (30)    Nonpolymeric proton exchange interface (40)    Conduit (47)