A landfill is a carefully designed place where garbage and trash get buried in the ground. When the garbage truck picks up your family's trash each week, it usually ends up at a landfill, where workers spread it out in layers and cover it with soil.

Modern landfills are engineered facilities with important safety features. Engineers build them with thick plastic liners at the bottom to prevent chemicals from leaking into groundwater. They install pipes to collect gases that form as trash decomposes, and they can even use these gases to generate electricity. Workers use heavy machinery to compact the garbage, making it take up less space, then cover each day's trash with clean dirt.

The word can also describe the actual pile of buried trash itself. You might hear someone say, “that old landfill is full” when there's no more room for additional garbage.

Landfills solve an immediate problem (where to put all our trash), but they create long-term challenges. A plastic bottle buried in a landfill might sit there for 450 years before it breaks down. That's why many communities encourage recycling and composting: the less we send to landfills, the better. Some trash, like apple cores and grass clippings, belongs in a compost pile where it can become rich soil instead of taking up space underground for decades.