We often hear
that it takes 500 years or more for plastic bags to decay in a landfill.
But is that bad news? It’s certainly reported that way. People react with horror when they hear that plastic lasts a thousand years.
Actually, it's very good news.
The following table is extracted from the Friends of the Earth website:
| GREENHOUSE GASES
| Carbon Dioxide (CO2)
| Methane (CH4)
| Chlorofluorocarbons (CFCs)
| Nitrous Oxide (N2O)
As we can see, methane is a major contributor to the greenhouse effect.
What happens to paper bags in a landfill? The EPN report states (at page v):
If paper is landfilled rather than recycled, it decomposes and produces methane, a greenhouse gas with 23 times the heat-trapping power of carbon dioxide. More than one-third of municipal solid waste is paper, and municipal landfills account for 34 percent of human related methane emissions to the atmosphere, making landfills the single largest source of such emissions. The U.S. Environmental Protection Agency has identified the decomposition of paper as among the most significant sources of landfill methane.
An article in the Ecocycle Times states:
Methane is produced in a landfill when the organic materials like paper, yard debris, wood, and food waste undergo anaerobic decomposition—a process that shouldn’t be confused with the oxygen-dependent aerobic process that breaks downs the fruit rinds and leaves in your backyard composter. As a result of anaerobic decomposition, the methane gas seeps to the surface, enters the lower atmosphere, and in concert with carbon dioxide and other gases, creates a warming blanket that retains solar infrared radiation and warms the earth.
The best material to put in a landfill is ordinary non-degradable polyethylene, which is used to make plastic bags. It does not produce greenhouse gases in a landfill.