In the modern landfill, the primary concern is hygiene. The drive towards a hygienic way
to dispose of waste created the push for a landfill that isolated the trash from the external
environment. The modern landfill is now lined with either plastic or bentonite clay so that
toxic fluids do not leach from the landfill into the ground water and each layer is covered
with impermeable clay. These conditions create an isolated area which has very little or no
oxygen. This type of low oxygen area is perfect for the anaerobic breakdown of garbage.
This anaerobic respiration by bacteria produces methane gas deep within the landfill. This
landfill gas is then vented out of the core of the landfill with pipes in order to avoid the
danger of fire or explosion which the methane brings about.
The above diagram shows the setup of an example modern landfill.