SciTech

How Things Work: Landfills

Trucks like these compact trash to create space for more waste. Landfills can contain millions of tons of trash that need to be stored or processed. Some landfills also work in conjunction with recycling plants, and some turn waste into energy that can be used to power homes. (credit: Courtesy of Wikimedia Commons) Trucks like these compact trash to create space for more waste. Landfills can contain millions of tons of trash that need to be stored or processed. Some landfills also work in conjunction with recycling plants, and some turn waste into energy that can be used to power homes. (credit: Courtesy of Wikimedia Commons)

On average, Americans produce 1,600 pounds of garbage every year, according to the Environmental Protection Agency (EPA). The amount of trash produced in America annually can fill up enough garbage trucks, lined up end to end, to reach the moon. Luckily, landfills have been created and designed specifically to contain and process waste material. Without these indispensable filling grounds, America would quickly turn into a wasteland.

According to reports by the EPA, 55 percent of trash is found in landfills, while 28 percent is recycled and 22 percent is incinerated.

Landfill sites are picked where the natural setting will contribute to the needs of the landfill. Man-made structures are built to keep wastes from escaping, but the structure of the soil under the landfill is also important. According to www.ejnet.org, the ground should be watertight, and if any leakage occurs, it should be easy to predict where the leakage will collect so it can be removed.

Landfills are often seen as places where trash is dumped and ignored, but many more processes are involved in waste disposal. According to www.scdhec.gov, a landfill has different parts with specific functions. The bottom liner system keeps the waste isolated from the environment and is composed of layers of clay, sand, and plastic. Cells are the site of trash compaction. In order to prevent rainwater from touching trash, a storm water drainage system channels water away to a collection pond. However, water that has come into contact with waste must be collected by the leachate collection system and treated to remove contaminants. Finally, the decomposition of trash produces flammable gases that must be collected by the methane collection system to prevent combustion of the waste.

There are potential problems with the layers in a landfill. Clay liners can be fractured, and chemicals can diffuse, or seep, through layers of clay. In addition, some chemicals can degrade the clay liners.
Plastic liners can also be degraded easily by common household chemicals, including vinegar and mothballs. Leachate collection systems can clog for various reasons, including mud buildup, microorganisms, collection of minerals, and chemical degradation.

In a landfill, trash that is dumped does not decompose readily. Oxygen and moisture are necessary for decomposition, and these requirements are rare under millions of pounds of compacted trash. Likewise, the Air and Waste Management Association explains that plastics thrown away in landfills, even if marked as biodegradable, usually cannot decompose because they are hidden under layers of trash. The degradation process requires sunlight to occur. According to www.howstuffworks.com, landfills are meant to store trash, not decompose it, as is done with a compost pile. When landfills reach their capacity and close, the trash is buried, but the site is still monitored for decades. In fact, the John F. Kennedy and La Guardia airports in New York City were constructed over closed landfills.

Landfills are an essential part of the waste management system, but even with current technology they use large amounts of space. To become more efficient, some landfills work with recycling plants, while others turn methane gas and other byproducts of the decomposition of waste into energy that nearby residents can use. While trash may always be present in our lives, the amount we create can be reduced through simple means like recycling, reusing old containers, and using organic wastes as compost to help fertilize lawns.