NOVELTY - A gasifier (10) comprises a processing chamber (11) having a material inlet (19) at an upper part of the chamber and an opening which is at a lower part of the chamber and in direct communication with a reduction zone of the chamber; a screw auger (57) contained within a horizontal tube (56) having an inlet opening (55) communicating with the bottom of the chamber, and a discharge opening (62) remote from the inlet opening; a motor drive to rotate the auger; and an inclined further screw auger to transfer the ash to a suitable receptacle.    USE - For the generation of producer gas by burning combustible materials; and useful for processing various kinds of waste organic substances, such as dried sewage sludge and vehicle tires.    ADVANTAGE - The gasifier does not use a grate, as such, for supporting the column of material to be processed within the gasifier and allowing the separation of ash and other waste solid products of combustion. The gasifier utilizes a screw-auger arrangement to remove ash and waste products from the bottom of the combustion chamber, that auger serving directly to support the column of material to be processed. The design of gasifier is very much less prone to blockages caused by gasifying materials including significant solid content or chemicals which will solidify into large lumps of slag. In turn, this leads to the possibility of operating the gasifier for longer periods between shutdowns than is currently possible with a gasifier having a complex grate assembly. The advantage of use of screw-auger is that the material within the auger will serve to effect a seal to containing tube for the auger. In this way, the entry of air to the gasifier through the removal means for the burnt material will be restricted. A valve arrangement provided at the outlet of the screw-auger, prevents air moving along the auger and then entering the combustion chamber. An airlock arrangement with two valves provided at the discharge opening from the screw auger, maintains the integrity of the airtight seal provided by the valve arrangement and prevents the ingress of air when combustible matter is fed into the processing chamber.    DESCRIPTION OF DRAWING(S) - The figure shows a diagrammatic side view, in section, of the gasifier.    gasifier (10)    processing chamber (11)    material inlet (19)    inlet opening (55)    horizontal tube (56)    screw auger (57)    discharge opening. (62)