A method of concurrently retorting dissimilar hydrocarbonaceous resource streams comprising at least two rotary kilns arranged in a series and closely coupled in an air-tight continuous process flow configuration so as to create a virtual singular rotary kiln yet having distinct residence times and temperature differentials and material processing zones also having continuous thermal coupling and process efficiency achieved by passing along from the first rotary kiln all of the hot spent inorganic waste materials between and into the at least second rotary kiln to then have other dissimilar hydrocarbonaceous matter added therein and differentially heated until the hot inorganic waste materials are released from the at least the second rotary kiln and the increasing residual waste matter volume generated in the combined serial process is ultimately discharged into a secondary heat recovery system.