A method and apparatus for treating waste materials comprising, particulating the waste materials into discrete particles, heating and drying the particles in a non-oxidizing atmosphere in a drier at a temperature in the range of 800° to 860° C. for carbonizing the particles, crushing the carbonized particles and leaching the crushed carbonized particles in an acid solution for dissolution of heavy metals into the solution, separating the leach solution containing heavy metal from the carbonized particles, adding to the carbonized particles particulate sodium hydroxide, silica, feldspar and limestone in a ratio of 100:0.3-0.5:8-12:2-4, mixing said particles with 15 to 18% by weight water to form a wet mixture and continuously extruding the wet mixture to form an elongated continuous extrusion, severing the elongated extrusion into blocks or planks of predetermined length, drying the blocks or planks and heating the dried blocks or planks in a kiln at a temperature in the range of 1200° to 1300° C. for a time sufficient in an oxygen deficient atmosphere to sinter the blocks or planks and to form carbides, and separating and recovering CO2 gas from combustion gases in the kiln.