A pyrolyzer has a heated inner housing that includes first and second conveyors. Preferred conveyors have independent or at least potentially independent flows of material to be pyrolyzed. All suitable conveyors are contemplated, including especially screw conveyors, or combination of screw and paddle conveyors. Both first and second conveyors can be disposed within a common lumen, with a partial divider between them. An alternative divider is also contemplated that more or less divides the inner housing into two lumens. Thus, the lumens can be entirely distinct, or can have cross-flow of gases and/or material being pyrolyzed. Heat transfer fins can be advantageously attached, extend from, or be otherwise coupled to the inner housing to assist in transfer of heat into the lumen(s) of the inner housing.