What is landfill gas?

• A. Methane produced by decomposing waste; flammable greenhouse gas
• B. A toxic liquid formed when water passes through waste and carries pollutants
• C. A type of soil
• D. A policy measure

Answer: (A)

Landfill gas forms when organic waste within a landfill decomposes in an oxygen-poor (anaerobic) environment. The main component is methane, produced by microbes breaking down the waste, along with carbon dioxide and small amounts of other gases. Because methane is highly flammable and a potent greenhouse gas, landfill gas poses both safety (explosion risk) and climate concerns if released untreated. That’s why capturing it for energy or flaring is a common practice.

Leachate, by contrast, is a toxic liquid formed when water percolates through waste and picks up dissolved pollutants; it’s a liquid, not a gas. A type of soil and a policy measure don’t describe landfill gas.