Question

In which of the following methods solid wastes are broken down through process of destructive distillation in an oxygen-free atmosphere into gases?

• A. Incineration
• B. Pyrolysis
• C. Composting
• D. Burning in multiple hearth furnaces

Hint:

Oxygen present = Incineration; Oxygen absent = Pyrolysis.

Answer 1

The Correct Option is B

Concept: Waste management involves various thermal and biological processes to reduce waste volume and recover energy. Thermal processes are differentiated by the presence or absence of oxygen.

Step 1: Defining Pyrolysis.
Pyrolysis is the thermochemical decomposition of organic material at elevated temperatures in the absolute absence of oxygen. It involves the simultaneous change of chemical composition and physical phase, often referred to as "destructive distillation."

Step 2: Understanding the Output.
In a pyrolysis reactor, organic waste is converted into three main components:
• Syngas: A mixture of combustible gases like hydrogen, carbon monoxide, and methane.
• Bio-oil: A liquid fraction.
• Char: A solid carbon-rich residue.

Step 3: Differentiating from Incineration.
Unlike Incineration, which is a combustion process occurring in the presence of excess oxygen (resulting in CO$_2$ and heat), Pyrolysis is endothermic and avoids the direct burning of the waste, making it a "cleaner" alternative for energy recovery.