A process for disposing of sewage sludge by heating and shearing an aqueous mixture of sewage sludge in a tubular-shaped processing means containing a plurality of rotating agitators to produce a pumpable aqueous slurry of sewage sludge. The aqueous slurry of sewage sludge is mixed with solid carbonaceous fuel or an aqueous slurry of solid carbonaceous fuel to produce a pumpable aqueous slurry of sewage sludge and solid carbonaceous fuel. The aqueous slurry of sewage sludge and solid carbonaceous fuel is heated in a first steam jacketed rotary disc mixing-heating means. Alternately, first and second hoppers are filled with said heated aqueous slurry of sewage sludge and solid carbonaceous fuel and cycled between a second steam jacketed rotary disc mixing-heating means; wherein while one hopper is being filled the contents in the other hopper are being dewatered. The thickened pumpable slurry is burned in a partial oxidation gasifier, furnace, boiler, or incinerator to produce a hot effluent gas steam. By this process, noxious sewage sludge may be disposed of without contaminating the environment. By-product synthesis gas, reducing gas, or fuel gas may be produced.