A device for continuous dry methanation in a fermenter having a closed tank having at least one compartment to ferment the slurry comprising at least 17% dry matter. An injector to inject pressurized gas close to the bottom of the compartment via at least one chimney that descends through the compartment. The injected gas rising through the slurry creates a convective movement in the slurry around the chimney to stir the matter at the bottom of the compartment. The tank can include a first compartment into which the slurry is introduced and a second compartment into which the hydrolyzed slurry flows after hydrolysis and acidogenesis in the first compartment. Methanogenesis takes place in the second compartment.