NOVELTY - The apparatus has a stage separation unit being in communication with a reactor (620) to receive a solid product, a liquid product and water (632). The stage separation unit separates out the reacted solid product, the water and the reacted liquid product. Another reactor (600) is in communication with the separation unit to receive the reacted liquid product. The latter reactor subjects the reacted liquid product to an increased pressure and an increased temperature for converting the reacted liquid product to a useful material.    USE - Apparatus for converting a carbon-containing feedstock e.g. municipal sewage sludge, rubber materials and mixed plastics, into a useful material e.g. carbon solids material and mixture of carboxylic oil or hydrocarbons/fuel oil (all claimed), for manufacture of tires in vehicles e.g. automobiles, buses, lorries, aircraft and military vehicles, and for manufacture of animal and plant products and turkey/fish/chicken/pig/cattle-processing and husbandry wastes. Can also be used for converting offal, animal manures and tires into a useful material.    ADVANTAGE - The apparatus occurs degassing in a feed storage tank, so that unwanted gaseous impurities are removed at an early stage. The apparatus floats the material that is lighter than the water introduced to a raw feed to assist with floating heavier than water organic materials, thus facilitating separation of organic from inorganic materials. The apparatus redirects fuel gas from a mixture of hydrocarbons and gases back to heater and burned to maintain the temperature in the heater, thus promoting efficiency of a process.    DETAILED DESCRIPTION - The useful material is carbon solids (142) and a mixture of carboxylic oil or hydrocarbons/fuel oil (all claimed).    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of an apparatus for converting a carbon-containing feedstock into a useful material.    Carbon solids (142)    Reactors (600, 620)    Fluid-solid separator (624)    Water (632)    Bucket lift (654)