Which process is used for high-volume reduction of municipal solid waste by heating in the absence of oxygen?

Which process is used for high-volume reduction of municipal solid waste by heating in the absence of oxygen?

• A. Pyrolysis
• B. Hydrolysis
• C. Fermentation
• D. Gasification

Answer: (A)

The key idea is heating waste in an environment with no oxygen to cause it to thermally decompose rather than burn. When MSW is heated without oxygen, the long, complex molecules break apart into smaller volatile compounds, liquids, and a solid char. This changes the material into lighter gases and liquids plus a reduced-volume solid residue, achieving significant volume reduction without combustion. That combination—high temperature, absence of oxygen, and decomposition rather than burning—defines pyrolysis. Gasification also involves heating to produce gases, but it uses limited oxygen, not a strictly oxygen-free environment, so it’s not the same exact process. Hydrolysis is a chemical reaction with water, not a heating-in-inert-atmosphere process. Fermentation is a biological process involving microorganisms. So the method that fits heating in the absence of oxygen to reduce volume is pyrolysis.

The key idea is heating waste in an environment with no oxygen to cause it to thermally decompose rather than burn. When MSW is heated without oxygen, the long, complex molecules break apart into smaller volatile compounds, liquids, and a solid char. This changes the material into lighter gases and liquids plus a reduced-volume solid residue, achieving significant volume reduction without combustion. That combination—high temperature, absence of oxygen, and decomposition rather than burning—defines pyrolysis.

Gasification also involves heating to produce gases, but it uses limited oxygen, not a strictly oxygen-free environment, so it’s not the same exact process. Hydrolysis is a chemical reaction with water, not a heating-in-inert-atmosphere process. Fermentation is a biological process involving microorganisms. So the method that fits heating in the absence of oxygen to reduce volume is pyrolysis.