Methods and apparatus provide for: producing a plasma plume within a plasma containment vessel from a source of plasma gas; feeding an elongate feedstock material having a longitudinal axis into the plasma containment vessel such that at least a distal end of the feedstock material is heated within the plasma plume; and spinning the feedstock material about the longitudinal axis as the distal end of the feedstock material advances into the plasma plume, where the feedstock material is a mixture of compounds that have been mixed, formed into the elongate shape, and at least partially sintered.