Trash Sticks Around

Photo courtesy of National Geographic.

Reusing is important because it helps keep waste out of landfills. In 250,000,000 Tons of Trash From 1 Country In 1 Year, you read about the astounding quantity of trash that ended up in United States' landfills in 2010. What happens to all of that trash? It biodegrades. Eventually. Some trash biodegrades fairly quickly. Most takes months or even years to decompose if it is an environment suitable for biodegradation. According to Measuring biodegradability, an article featured on The Science Learning Hub, "a study of waste conducted by a group at the University of Arizona, USA. [. . .] unearthed from landfill hot dogs, corn cobs and grapes that were 25 years old and still recognisable, as well as newspapers dating back to 1952 that were still easily readable!"

Biodegradation

Biodegradation is the process by which trash trash decomposes. The United States Geological Survey defines it as "the transformation of a substance into new compounds through biochemical reactions or the actions of microorganisms such as bacteria." Trash in landfills takes a long time to decompose because it is not a suitable environment for biodegradation. An example given in Measuring biodegradability is that "many products that are biodegradable in soil [. . .] will not biodegrade when we place them in landfills, because the artificial landfill environment lacks the light, water and bacterial activity required for the decay process to begin."

Determining Biodegradability

Scientists perform laboratory experiments to determine how fast and under what process different things decompose. For things that are biodegraded by microorganisms, scientists perform experiments to measure how much carbon dioxide microorganisms release while consuming something over a set amount of time. Unfortunately, measuring the biodegradation rate of things is not always that easy. An example of this is scientists' uncertainty about the biodegradation rate of plastic bags. It is written in Measuring biodegradability that

"when exposed to ultraviolet radiation from sunlight, polyethylene's polymer chains [the components of plastic bags] become brittle and start to crack. This suggest that plastic bags will eventually fragment into microscopic granules. As of yet, however, scientists aren't sure how many centuries it takes for the sun to work its magic."

Biodegradation Rates

Below is a chart from Measuring biodegradability that lists some different waste materials and their estimated biodegradation rate.

Vegetables	5 days –1 month
Paper	2–5 months
Cotton T-shirt	6 months
Orange peels	6 months
Tree leaves	1 year
Wool socks	1–5 years
Plastic-coated paper milk cartons	5 years
Leather shoes	25–40 years
Nylon fabric	30–40 years
Tin cans	50–100 years
Aluminium cans	80–100 years
Glass bottles	1 million years
Styrofoam cup	500 years to forever
Plastic bags	500 years to forever

About

The Science Learning Hub

The Science Learning Hub is a teaching resource geared towards teachers of younger children. According to its About us page, "The Science Learning Hub is developed by educators and teachers in collaboration with New Zealand scientists. The project is funded by the Ministry of Business, Innovation and Employment (MBIE), and managed by the University of Waikato."

The United States Geological Survey

The United States Geological Survey is an organization that employs experts who study the Earth and environment. According to the About USGS page, it "is a science organization that provides impartial information on the health of our ecosystems and environment, the natural hazards that threaten us, the natural resources we rely on, the impacts of climate and land-use change, and the core science systems that help us provide timely, relevant, and useable information."

Critique

Though information presented in Measuring biodegradability is incomplete and mostly uncited, it being a teaching aid backed by a university means the information it does give can be trusted. I use the United States Geological Survey to define biodegradation because its definition is more complete and from a definitively objective source.