There are two ways to bury trash:
- Dump - an open hole in the ground where trash is buried and that has various animals (rats, mice, birds) swarming around. (This is most people's idea of a landfill!)
- Landfill - carefully designed structure built into or on top of the ground in which trash is isolated from the surrounding environment (groundwater, air, rain). This isolation is accomplished with a bottom liner and daily covering of soil. A sanitary landfill uses a clay liner to isolate the trash from the environment. A municipal solid waste (MSW) landfill uses a synthetic (plastic) liner to isolate the trash from the environment
The purpose of a landfill is to bury the trash in such a way that it will be isolated from groundwater, will be kept dry and will not be in contact with air. Under these conditions, trash will not decompose much. A landfill is not like a compost pile, where the purpose is to bury trash in such a way that it will decompose quickly.