In the past, rubbish was taken to old quarries, burnt and then covered with soil. Many of these ‘tips’ were poorly designed with many problems, such as smells, air pollution, litter, vermin and contamination of ground water.
Modern day landfills in Australia are designed to overcome these problems and must comply with strict government regulations. These landfills are still situated in mainly old quarries, but they have many features to stop the problems of the past. They are used to dispose of rubbish collected from homes, shops, businesses, and in some cases, building sites. Special landfills are set aside for rubbish that is considered toxic or hazardous waste.
A typical landfill pit is lined with a layer of clay and sometimes a plastic liner as well. This prevents any liquid from seeping into the nearby soil and ground water.
In order to pack as much rubbish as possible in a landfill, the rubbish is compacted by heavy vehicles, excluding the air from the rubbish. In these airless conditions, the rubbish only breaks down slowly. The gases given off by the slowly rotting material are mainly a mixture of carbon dioxide and methane – called landfill gas. Some of this gas can be removed through special pipes and, in many cases, sent to a factory where it is used to generate electricity.
Any water that was in the rubbish or is formed during breakdown is squeezed out of the rubbish and soaks through the layers of rubbish and sand or soil to the bottom of the landfill where it is collected in special pipes and pumped to storage ponds. The contaminated water, which can be made up of many different chemicals, is either treated or disposed of to the sewers.