Which process allows for 95 percent or more volume reduction of municipal solid wastes?

• A. Pyrolysis
• B. Maceration
• C. Aeration
• D. Fermentation

Answer: (A)

High volume reduction comes from heating waste in the absence of oxygen so it thermally decomposes rather than burns. This process, pyrolysis, drives off moisture and organic components as gases and liquids and leaves behind a small, carbon-rich solid residue. Because oxidation is avoided, most of the original volume is eliminated rather than converted to ash, yielding 95 percent or more reduction under the right conditions. Maceration only grinds waste into smaller pieces and doesn’t greatly decrease mass or volume. Aeration speeds up decomposition in composting or digestion but typically doesn’t achieve such extreme volume reduction. Fermentation (anaerobic digestion) converts organics to biogas and leaves digestate that still occupies substantial volume.