Step 1: Concept Analysis:
Determine the thermal waste treatment method that involves heating without any oxygen.
Step 3: Detailed Analysis:
\[\begin{array}{rl} \bullet & \text{(A) Incineration: Waste combustion requiring sufficient oxygen.} \\ \bullet & \text{(B) Pyrolysis: Thermal decomposition of organic matter at high temperatures in a completely oxygen-absent environment, yielding solid, liquid, and gaseous byproducts.} \\ \bullet & \text{(C) Gasification: Conversion of carbonaceous materials to synthesis gas at high temperatures with a controlled, limited oxygen/steam supply; not oxygen-free.} \\ \bullet & \text{(D) Composting: Aerobic biological decomposition of organic waste by microorganisms.} \\ \end{array}\]
Step 4: Conclusion:
Pyrolysis is the thermal decomposition of waste in an oxygen-free environment.