Where is ‘away’ and how does the non-fanciful place really affect us? These are pretty forward questions which I hope to answer with the three posts. How they affect our land, how they effect our water, and how they effect our air.
The space that is dedicated to landfills results in odor and loss of habitat. In addition, landfills are expensive to build and maintain. Americans spend $7 billion a year on trash disposal. In the U.S. it is estimated that 4.6 pounds of trash is thrown away by each person (I have a hard time believing it’s not more than that) which translates to 251 million tons per year. This is almost twice as much trash per person as most other major countries. About 32.5 percent of the trash is recycled or composed, 12.5 percent is burned and 55 percent is buried in landfills. The amount of trash produced has nearly tripled and the amount of trash buried in landfill has nearly doubled since 1960.
The United States ranks about in the middle of the major countries (United Kingdom, Canada, Germany, France and Japan) in landfill disposal. The United Kingdom ranks highest, burying about 90 percent of its solid waste in landfills.
So what are we actually throwing ‘away’?
And this per person.
And then there is the question of what ‘away’ really is.
The purpose of a landfill is to bury the trash in such a way that it will be isolated from groundwater, will be kept dry and will not be in contact with air. Under these conditions, trash will not decompose much. When old landfills have been excavated or sampled, 40-year-old newspapers have been found with easily readable print. Landfills are not designed to break down trash, merely to bury it. When a landfill closes, the site, especially the groundwater, must be monitored and maintained for up to 30 years! A landfill is not like a compost pile, where the purpose is to bury trash in such a way that it will decompose quickly.
There are two ways to bury trash:
- Dump – an open hole in the ground where trash is buried and that has various animals (rats, mice, birds) swarming around.
- Landfill – carefully designed structure built into or on top of the ground in which trash is isolated from the surrounding environment (groundwater, air, rain). This isolation is accomplished with a bottom liner and daily covering of soil. A sanitary landfill uses a clay liner to isolate the trash from the environment. A municipal solid waste (MSW) landfill uses a plastic liner to isolate the trash from the environment
There are different types of landfills, each designed to handle particular waste streams. A RCRA Subtitle C landfill contains mostly hazardous waste. Municipal solid waste can be placed into a RCRA Subtitle D landfill. There are also, construction and demolition landfills and industrial landfills which contain non hazardous waste. It is estimated that 78,000,000 tons of trash is under Industrial Waste. Each landfill is permitted or licensed for particular kinds of waste and generally cannot accept waste that falls outside the scope of its permit. The owner or operator does not have to accept any waste even if it falls among things that are permitted there. Some wastes may need to be treated before being disposed of in a landfill. It is important to note that treatment options may generate their own wastes, which may also be disposed of in landfills, when appropriate. More information on landfills can be found on EPA’s Landfills/Land Disposal web page.
Bottom Liner System
A landfill’s major purpose and one of its biggest challenges is to contain the trash so that the trash doesn’t cause problems in the environment. The bottom liner prevents the trash from coming in contact with the outside soil, particularly the groundwater. In MSW landfills, the liner is usually some type of durable, puncture-resistant synthetic plastic (polyethylene, high-density polyethylene, polyvinylchloride). It is usually 30-100 mils thick. The plastic liner may be also combined with compacted clay soils as an additional liner. The plastic liner may also be surrounded on either side by a fabric mat (geotextile mat) that will help to keep the plastic liner from tearing or puncturing from the nearby rock and gravel layers.
When a section of the landfill is finished, it is covered permanently with a polyethylene cap (40 mil). The cap is then covered with a 2-foot layer of compacted soil. The soil is then planted with vegetation to prevent erosion of the soil by rainfall and wind. The vegetation consists of grass and kudzu. No trees, shrubs or plants with deep penetrating roots are used so that the plant roots do not contact the underlying trash and allow leachate out of the landfill.
Cells (Old and New)
Perhaps, the most precious commodity and overriding problem in a landfill is air space. The amount of space is directly related to the capacity and usable life of the landfill. If you can increase the air space, then you can extend the usable life of the landfill. To do this, trash is compacted into areas, called cells that contain only one day’s trash. In the North Wake County Landfill, a cell is approximately 50 feet long by 50 feet wide by 14 feet high. The amount of trash within the cell is 2,500 tons and is compressed at 1,500 pounds per cubic yard! This compression is done by heavy equipment that go over the mound of trash several times. Once the cell is made, it is covered with six inches of soil and compacted further. Cells are arranged in rows and layers of adjoining cells (lifts).