NOVELTY - A gas generator (10) includes a structure defining conduit(s) (18) where solid fuel descends. The gas generator has walls defining chambers and interspaces connecting with the conduit(s). The chambers and interspaces have aperture(s) (19) where hot gases are introduced from user machine exhausts or cooling systems. The hot gases allow at least a partial energy recovery.    USE - For producing methane gas and carbon oxide from solid refuse, domestic and/or industrial, from low-cost solid products, e.g. wood chips, wood discards, solid biomasses, e.g. peat, lignite, and carbon fossils.    ADVANTAGE - The inventive gas generator produces methane and carbon oxide with high calorific power, and with minimal production of water gas, and free hydrogen. It has improved gasification process in terms of yield or efficiency.    DETAILED DESCRIPTION - A gas generator includes a structure defining conduit(s) where solid fuel descends. The structure comprises an upper part (10a) cooperating with a loading device (12) and a lower part (10b) defining a hearth (30). The upper part performs dry distillation of the fuel. Oxidizing and reducing combustion, and gasification of the fuel occur at the hearth. A produced combustible gas is fed to user machine(s), e.g. motor or boiler. The gas generator has walls defining chambers and interspaces connecting with the conduit(s). The chambers and interspaces have aperture(s) where hot gases are introduced from user machine exhausts or cooling systems. The hot gases allow at least a partial energy recovery. A conduit (28) is included to convey volatile part(s) from the fuel distillation, which is useful as comburent to reduce a quantity of new comburent air taken from outside.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a gas generator.    Gas generator (10)    Lower part (10b)    Loading device (12)    Interspace (16)    Conduit(s) (18)    Aperture(s) (19)    Aperture (20)    Conduit (28)    Conduits (29, 50, 52)    Hearth (30)    Burner (31)    Interspaces (37, 38)    Wall (44)    Cooling device (51)    Inner and outer finned tubes (53, 56)