NOVELTY - An electrochemical fuel cell comprises an electrochemical reactor (1) and an oxidation reactor (6). The electrochemical reactor consists of a cathode (2), an anode (4), and an ionically-conducting electrolyte (3). The oxidation reactor consists of an inlet (7) for dissolved oxygen, a bed (8) or slurry of solid carbonaceous substrate, an outlet (11) for removing oxidized carbon species, and an outlet (10) for re-introducing the deplenished liquid to the electrochemical reactor.    USE - Electrochemical fuel cell is used for generating electricity (claimed).    ADVANTAGE - The electrochemical fuel cell allows the use of carbonaceous substrates comprising hetero atoms, and facilitates subsequent treatment of resulting carbon-dioxide product by sequestration and sulfur removal. The formation of solid metal oxide in the oxidation reactor rather than in the electrochemical reactor prevents voltage losses and other problems. The carbonaceous substrate can be provided continuously while the fuel cell is in use or in a batch wise manner. The fuel cell provides improved efficiency compared with electrical power generation by fossil fuel combustion. The generation of electricity from coal and/or waste carbon product improves security and reliability of energy conversion. The fuel cell eliminates the need for gasification and gaseous fuel purification.    DETAILED DESCRIPTION - An electrochemical fuel cell comprises an electrochemical reactor and an oxidation reactor. The electrochemical reactor consists of a cathode for forming oxygen ions from an oxygen source, an anode for facilitating the dissolution of oxygen into a liquid, and an ionically-conducting electrolyte for transporting the oxygen ions to the anode. The oxidation reactor consists of an inlet for introducing dissolved oxygen from the electrochemical reactor, a bed or slurry of solid carbonaceous substrate, an outlet for removing oxidized carbon species generated by oxidation of the carbonaceous substrate by dissolved oxygen, and an outlet for re-introducing the deplenished liquid to the electrochemical reactor. The electrolyte is zirconia-yttria, yttrium-stabilized zirconia, and/or cerium-gadolinium oxide (Ce0.9Gd0.1O1.95). The cathode is lanthanum-strontium-cobalt-iron oxide (La0.6Sr0.4Co0.2Fe0.8O3) or lanthanum-strontium-manganese oxide (La0.6Sr0.4MnO3). The solid carbonaceous substrate is coal, petroleum derived fuel, petroleum coke, natural gas, naphtha, low-sulfur fuel oil, hydrocarbons including long-chain hydrocarbon, acetylene black, furnace black, carbon black, carbon aerogel, graphite, charcoal, carbon-based polymers including plastic, pitch, tar, asphalt, wood, biomass, and/or waste carbon product.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the fuel cell.    Electrochemical reactor (1)    Cathode (2)    Electrolyte (3)    Anode (4)    Oxidation reactor (6)    Inlet for dissolved oxygen (7)    Bed (8)    Outlet for re-introducing the deplenished liquid to electrochemical reactor (10)    Outlet for removing oxidized carbon species (11)