A method for converting fuel may include reducing at least one metal oxide in a first reactor with a fuel to produce a reduced metal or a reduced metal oxide, transporting the reduced metal or reduced metal oxide from the first reactor to a second reactor, oxidizing at least a portion of the reduced metal or reduced metal oxide from the first reactor in the second reactor to produce a metal oxide intermediate, transporting the metal oxide intermediate from the second reactor to a third reactor, removing ash, char, or unwanted materials with a separation unit from the metal oxide intermediate transported from the second reactor to the third reactor, regenerating the at least one metal oxide, and transporting the regenerated metal oxide from the third reactor to the first reactor.