In a properly engineered landfill, no bag whether it is cotton, paper, plastic or reusable will decompose.
Landfills are highly engineered to deter decay; essentially to mummify the contents. Landfills are designed to provide a sealed, oxygen-free environment.
A garbage study sponsored by the University of Arizona and published in “Rubbish: The Archeology of Garbage (2001)” by Dr. William Rathje confirmed the dynamics of landfills as low-oxygen environments that preserve contents. The study of a Phoenix landfill found that “almost all the organic material” from the 1950s “remained readily identifiable: Pages from colouring books were still clearly that, onion parings were onion parings, carrot tops were carrot tops.”
Because of the lack of oxygen, bacteria in the waste produces carbon dioxide and methane gas, which is highly flammable and dangerous if allowed to collect underground. When a landfill is closed, they are often reclaimed and turned into parks.
How Landfills Work
- There is considerable misinformation on how landfills work. Landfills are not bio-reactors, meaning they are not meant to break materials down to nothing so we can continue to refill. They are designed to entomb or mummify waste.
- Landfills are engineered to create low-oxygen environments so that the waste will not decay. They are lined with clay and thick plastic liners to contain fluids and gases created by anerobic decomposition. The waste is compacted and covered with soil daily, and at the end of their life, they are capped to prevent leakage, in or out.3
- Today’s modern landfills are composed of four main elements: a bottom liner (which can be made from clay, plastic or a composite material), a leachate collection system, layers of sand and soil, and a cover.
The biggest problem with landfills is greenhouse gas emissions. Organic matter, often 30% of a landfill, will degrade, albeit very slowly. Even with strong preventative measures in place, fugitive emissions from landfills are a concern. In Canada, according to Environment Canada, landfills are still responsible for 20% of national methane emissions.
Methane is a greenhouse gas that is more harmful than carbon dioxide in terms of its global warming potential because it traps 21 times more heat than a molecule of carbon dioxide.1
COLUMN ONE : The Rotten Truth About Garbage : Stuff in landfills is not biodegrading as fast you think, says an archeologist who digs for pop-top cans instead of pottery shards.