Appts. for producing methane-rich fuel gas from biomass material feed, comprises: (a) cylindrical vessel (10) with input (11) and output (12) ends permitting gravity-driven travel of the feed through the vessel from input to output end; (b) axially extending box beam in vessel, including: - vanes (16), with first (19) and second (20) portions, welded together to form a hollow, central rotor shaft (18) defined by first portion of the vanes, mixing elements (16), formed by second portion of vanes for tumbling feed as seed feed travels along vessel, conduits (17), mounted to mixing elements for conducting gas produced from the feed and for heating the feed to provide a continuously increasing temperature profile along vessel from input to output end; (c) rotating the rotor (15); (d) feeding system mounted to vessel at input end for introducing feed to vessel, feeding system having: hopper (28) with lower end (29), above vessel for containing feed - first vertical pipe (30) with upper end coupled to lower end of hopper having lower end, first slide valve (32) at upper end of first vertical pipe for closing to contain feed in hopper - second slide valve (34), at lower end of first vertical pipe for closing to contain feed as feed is conducted into the first vertical pipe while first slide valve is open - inclined cylinder (36) with upper end coupled to lower end of first vertical pipe at first opening (37) having lower end, second vertical pipe (40) with upper end coupled to lower end of inclined cylinder at second opening (38) and lower end coupled to input end of vessel, first piston (42) sliding along inclined cylinder near cylinder upper end to seal first opening, second piston (44) sliding along inclined cylinder near cylinder lower end to seal second opening.    USE -   Production of methane-rich fuel gas from biomass material feed where the feeding system indicates a fixed volume of feed to the vessel without leakage.    ADVANTAGE -   Provides an improved rotor and intake and exhaust manifolds and the discharge system removes solid residue from the kiln without leakage.