Definition of Landfill
What Is a Landfill?
Unlike backyard trash pits, a landfill is usually a carefully designed and managed structure that is created to dispose of household and industrial waste in an isolated manner. Starting with a depression in the ground, engineers will line the bottom of the structure with a liner to prevent the waste from infiltration groundwater, soil, and air. These are the general components of a landfill:
- Bottom liner– could be made of clay or plastic (polyethylene or polyvinylchloride (PVC))
- Geotextile mat – to prevent tearing of a synthetic liner
- Leachate collection system– collect liquids that drain through the landfill
- Methane collection system – for collecting methane gas as it forms during waste decomposition
- Cells– chambers where waste is deposited and compacted to conserve as much space as possible
- Soil layer – added after trash is compacted, after which it is compacted again
- Stormwater drainage– for diverting rain as it falls on the landfill
- Landfill cover or cap – to seal in the solid waste, usually composed of more soil, but sometimes consists of tarps or recycled paper or newsprint
A dump, as apposed to a landfill, is an open hold that is not lined or designed to prevent the spread of pollution, though this is what people often envision when they think of a landfill.
Lechate is a serious environmental problem for landfills. Because no system can completely prevent water from going through it, water will slowly percolate through the solid waste much like making tea, collecting organic substances, chemicals, heavy metals, biological waste, and so on. The liquid that results, which is often highly toxic and acidic, is called leachate.
Another major environmental challenge for landfills is the production of methane gas and other greenhouse gases such as carbon dioxide. Because landfills are sealed up tightly, the waste will break down in an anaerobic or oxygen-deprived environment, which results in the byproduct methane. Many older landfills simply flare off this gas. But in some landfills, engineers have designed methods for collecting this greenhouse gas, a renewable resource, which is 20+ times more potent than carbon dioxide when it comes to its impact on climate change. By incorporating an extraction system for the landfill gas, methane is siphoned off and either used to produce electricity onsite or compressed and sold as a fuel for vehicles and buildings.