Discarded bottles begin their long road to decomposition.
Discarded bottles begin their long road to decomposition.

We really don’t know exactly how long it takes a glass bottle to decompose in a landfill, but we do know that it can break into smaller pieces eventually. Decomposition occurs when something breaks down into small parts or parts that are simpler in composition. In a landfill, where there are not many forces like wind and water that erode materials or specific chemicals that can weaken glass, it is likely to take a million years or more for glass to degrade.

The Chemical Structure of Glass and Increased Brittleness

The main ingredient in glass is silica, which is one of the hardest and most stable minerals on the Earth. Silica is the major component of sand, and glass is made of silica sand, lime and soda. If glass is immersed in such substances as high alkaline chemicals, its structure can be weakened slightly due to increased crystallization, which causes brittleness (Reference 1). It is highly unlikely that glass in a landfill would be exposed to the amount of chemicals necessary to cause this increased brittleness.

Glass Can Last a Very Long Time

There are glass pieces in museums that date back to 2000 B.C. In addition, glass has been found at meteor impact sites. It is believed that the incredible heat generated from the force of the impact created glass, and some of these impacts are estimated to have occurred 15 million years ago. These glass samples still exist today, indicating that glass can remain in virtually its same form for thousands to millions of years.

Amount of Glass in Landfills

Glass can possibly take a million or more years to break down and we have a lot in the nation's landfills and across the world. According to the Clean Air Council, a nonprofit environmental organization, in 2008, only 23.1 percent of glass discarded was recycled. Even though our Earth's crust is made mostly of silica, this is not in the form of glass. Now, with landfills across the planet, glass is fast becoming a major ingredient in pockets of Earth's crust and it will not decompose anytime soon.

Recycling of Glass, a Melting Pot

Glass can last millions of years, but it also can be recycled and made into various products virtually endlessly. It is recycled by heating to temperatures as high as approximately 2,800 degrees Fahrenheit; when glass melts, it can be molded into new shapes. However, different colors of glass have different ingredients with varying melting points. For this reason, glass is sorted by color to make the recycling effort more efficient. Recycling can limit the amount of space taken up in landfills by everlasting glass.