Energy, Climate, Environment

Where Does the Trash Go?

When the trash is put on the garbage truck and taken out of the community, where does it go? There are two main areas that trash is brought to be disposed of, landfills and incinerators also called combustion facilities. A landfill is typically a hole in the ground where trash is brought and buried. Historically, it was called a midden. A landfill is one of the oldest forms of waste treatment. It is also one of the most common forms of waste treatment still in use today. Landfills have evolved over the years. They had to. In many cases, as items began to decompose the toxicity levels began to rise. Rain water would mix in and create a substance called leachate. Leachate has been known to migrate from the landfill and contaminate wells, lakes, rivers, as well neighboring soil. Current landfills are chosen carefully based on proximity to the street, and the type of land it will be treated on. The landfill site has to pass very strict legal, environmental, and engineering tests. This process can take some time. It can easily take five years before a landfill is ready to use and the cost can be anywhere from $ 2 to $ 4 million dollars.

The modern landfill is no longer just a hole in the ground to dump trash in. A newer landfill is able to use the properties of a landfill to the advantage of the people. New landfills have four basic components. First, all modern landfills must be set in geologic location that has clay deposits and other natural land features that will help in preventing contamination from the landfill to the natural environment around it. Second, the bottom and sides of a modern landfill must have a liner that is made of clay or plastic. The purpose of the liner is to prevent leachate from escaping and contaminating the natural environment around it. The third thing a modern landfill must have is a leachate collection system. Leachate is collected by a series of drains that are networked throughout the landfill, and the leachate is pumped to the surface and sent to a wastewater treatment plant for treatment. The fourth and final element essential for modern landfills is a cover. The cover is usually several sloped layers of clay, soil, or membrane liner. This is to keep rain from entering the landfill and forming new leachate. A topsoil often overlays the landfill so that vegetation can root and stabilize the underlying layers of the cover. The cover has to be maintained. If it is not maintained, the leachate can build up to a point that it overflows the landfill and contaminates the surrounding environment. Covers are vulnerable to the natural environment around them. They can erode, vegetation grows on them thus bringing in burrowing soil-dwelling mammals, as well as reptiles, insects, and worms. Sunlight can even be a problem for covers, they are susceptible to cave-ins and even rubber tires which somehow tend to float upward in a landfill causing a possible breach. Modern landfills may also have additional components to them. They may have a well to monitor the methane gas that is created from the decomposing waste. Other landfills have a way to harness the methane gas where it can be used as a fuel for vehicles or power plants. This is very important for our planet. Methane gas is a gas that tributes to the greenhouse effect. The greenhouse effect is causing our planet to heat up at an unnatural rate.

Landfills are the most common way to dispose of waste in this country. Surprisingly, the number of landfills have decreased in the United States. In 1988, there were 7,924 across the country, by 2007 there were only 1,754. ⁵ The bar graph below illustrates the decline. This graph comes courtesy of the EPA's Guide for Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figures for 2007.

Although the number of landfills in the United States has declined, the size of the average landfill has increased. Zerowasteamerica.org has described a landfill as a big bathtub. The liner works to hold everything in but sometimes there are problems. The state of the art liners are made of a tough polyethylene plastic (HDPE) that is only 1/10 of an inch thick and whether it is clay or plastic can become brittle and crack due to the common household chemicals that can degrade it such as mothballs, margarine, vinegar, ethyl alcohol, shoe polish, and even peppermint oil. When cracks form in the liner, leachate and other contaminates can leak into the ground and surface water. Studies have shown that a ten acre landfill that has a leaking liner can have a leak rate somewhere between 0.2 and 10 gallons per day. ⁶ Another potential problem is that the landfill can fill up with leachate and overflow, polluting and contaminating the surrounding area. This can happen when the pipes that carry the leachate to the wastewater system get clogged, deteriorate, or are crushed from the weight of the waste.

In 1989 Dr. William Rathje, a professor at the Univesity of Arizona, did a very surprising study. He wanted to find out what was in America's landfills, so he formed a group called the Garbage Project. What the group found astonished him! Items that were thought to degrade quickly were found in the landfill in relatively good shape. The Garbage Project found newspapers from 1952 that could still be read perfectly, grass clippings that were still green, hot dogs that looked good enough to eat, a banana that was still yellow, and an ear of corn that had the husks and all, mixed in with material that was dated from 1971. Newspaper in a laboratory degrades very quickly. Sometimes it degrades within a day. The items that Dr. Rathje expected to find like plastic, foam packaging, and disposable diapers were there, but they were in much smaller amounts than the experts had predicted.

Another place trash goes is to an incinerator or combustion facility. An alternative to landfills, incinerators are more expensive but tend to be a safer method of waste disposal. An incinerator is simply a type of furnace that is used for burning waste. Modern incinerators are built and designed to destroy at least 99.9% of the organic waste material that they handle. ⁷ There are a number of thermal processes that recover energy from solid waste. Some companies will burn in-plant wastes in conventional incinerators so that they can produce steam. Most of the incinerators used in this country incorporate the recovery of an energy product, usually steam or electricity. There is a benefit to doing this, the energy that is produced reduces the amount of energy needed from other sources. The sale of the energy generated helps to offset the cost of operating the facility. Early on, the sole purpose of incinerators was to reduce the sheer volume of waste. It was not until the 1980's that the recovery of energy became more prevalent. The total number of incinerators in the United States that recovered energy from combustion was 87 in 2007, that's down from 102 in 2000. ⁸ These facilities in 2007 were processing 94,721 tons per day (tpd). ⁹ The EPA reports that the Northeast region had the most facilities that recovered energy from combustion. The following table from the EPA's Municipal Solid Waste In The United States: 2007 Facts and Figures Guide, shows how the municipal waste-to-energy facilities are distributed throughout the country:

There is a stark contrast between the Northeast and the West. There is a small, but growing number of facilities that are separating specific waste, particularly rubber tires which have been used as fuel in cement kilns, utility boilers, pulp and paper mills, industrial boilers, and dedicated scrap tire-to-energy facilities. ^{1 0} There is also combustion of wood wastes and some paper and plastic wastes. These are usually incinerated in boilers that already burn some other type of solid fuel. The EPA in its 2007 report estimated that about 3.1 million tons of waste was incinerated in this manner with tires contributing the majority of the total. ¹¹

When waste comes in it must be sorted for not all materials can be incinerated. A process of chemical decomposition, called pyrolysis, produces a variety of gases and inert ash. If the wrong material is incinerated, it could release toxic fumes and ash that could harm the workers and the environment. In the past, waste that has been burned in incinerators has poisoned the air, soil, and water. For this reason, many communities object to being near incinerators for fear of possible toxic emissions.

A third way of disposing waste is to compost. Composting is a biological process that occurs when tiny microscopic organisms break down organic waste which is plant and animal based waste. ¹² The microscopic organisms recycle the organic waste and turn it into a new rich, healthy, and fertile soil that can be used for a garden. The combination of the oxygen, heat and moisture helps to break down the organic waste. The second largest portion of American trash is yard trimmings. Composting is a specialized type of recycling that recycles yard waste as well as kitchen waste. Some cities have a separate compost area where they will take yard waste. The great thing about composting is that it can be done at home or at school. Composting at home can save time, energy and money needed for transporting yard and home waste from a home to a landfill or recycle center.

There is another seldom used method for waste disposal. The hazardous waste is pumped into deep wells in the earth. There is very strong opposition to this method. There have been explosions and even earthquakes that have resulted from this technique of injecting waste deep into the earth.