Earth Awareness: What Happens in a Landfill?
Do you take the trash out? Even if you don’t, have you ever really smelled this stuff? The kitchen produces a lot of organic waste and that type of refuse can turn on the odors: onions, old potatoes, orange rinds, an empty can of beans, moldy cheese, brown slimy heads of lettuce—ick, it really is smelly.
Now take this trash scenario a step further. Think about the trucks that run through your neighborhood picking up everyone’s trash. Are you curious about where it’s going? Sometimes things that are thrown away are harmful or unpleasant to keep. If trash is not removed, it can cause real problems. Trash draws animals and insects because it is like their own McTrash Meal; they can consequently become disease-carrying pests. Let’s examine more of this "throwaway story" and see what happens at the end for refuse, the landfill.
The average person generates more than four pounds of waste per day. To get a better idea of what that is, strap a four or five-pound weight around your ankle. It is heavy.
United States citizens create over half of the total millions of tons of waste (a ton is two-thousand pounds), 220 million tons in a year. It all lands in one of 3,500 landfills. That's not including commercial and industrial waste!
While we have don’t have the distinction of being the worst offenders (Mexico produces 30 percent more garbage), it’s not as if anyone is winning.
Truck It Away
Generally, a new garbage truck can cost $100,000 dollars or more and they have to be kept in good repair because of all the hard work they do. There are different models like the roll-offs. These trucks are the size of semitrailers and have huge metal boxes left behind at a site and when loaded, they are picked up with a forklift. Construction crews or factories primarily use these vehicles, which start at $130,000.00.
The rear loader or front-end loader is the type you probably see in your neighborhood. It picks up household waste and paper and maybe yard waste too. Dumpster models that actually hook a dumpster and roll it onto the opening of the truck with a machine lift start in price at $225,000.00. These expensive machines are not the only truck cost either, because most of them have compactors. Machines that compress the garbage down do some powerful squeezing; no one wants spillover and if the packers are super powerful, trucks can haul bigger loads.
Rubbish haulers work hard. Aside from picking up the trash, they must wash the trucks inside and out to prevent odors.
Where do the trucks align? At the landfill. The Environmental Protection Agency (EPA) of the federal government has authority over landfills. They are engineered facilities with location restrictions, operating practices, and designs to protect not only the surrounding environment but also water tables.
When your neighborhood garbage is hauled off, it most likely goes to a municipal facility and there are hundreds of restrictions for those special areas.
A landfill looks like a football stadium-sized hole in the ground although, in most instances, it is a hole that has been carefully planned. The goal is to contain the waste and have it decompose without ruining the surrounding environment, having it reach any groundwater and becoming viable land again.
In order for the landfill to be secured, it needs some layers:
- A bottom liner
- A leachate collection system
- And a natural hydrogeological setting
- A cover
The trucks drive their trash into the hole and each layer is covered with dirt, which keeps away birds, animals and insects. Eventually, the hole becomes level with the ground and then creates a hill. The layers must constantly be graded –leveled—and packed down so the trucks can drive over the landfill. Next is the hydrogeology goal: the layers and what needs to happen.
Hydrogeologic means the effect the landfill has on groundwater; it must be evaluated for contamination and a “hydrogeologic investigation” detects, corrects or prevents contamination.
The environment is checked to prevent waste from escaping and stopping any seepage into water tables so surrounding farm wells, lakes, mines, quarries and other water sources are not polluted. In order to do this, the landfill is constructed in layers, in connection with the rocks or materials already present.
To begin at the bottom, the soil underneath the landfill is prepared (called a “subgrade”). A bottom liner is fitted in made of compacted clay, which kind of acts like a bathtub. A thick plastic layer—polyethylene or HDPE—is next, it’s called a geomembrane and protects against leaking and gas escaping. Leaking of liquids from soluble material as it breaks down is called leachate. Even benign things such as mothballs can break down the plastic as well as your everyday margarine, vinegar, ethyl alcohol, shoe polish and peppermint oil.
Leachate collection is next and is accomplished with a series of pipes. Pipes with holes in them are buried between layers of gravel. The pipes are attached to sumps, which have pumps inside (often referred to sump-pumps). When the wastewater is driven to the low area sumps, it is then transported by pumping action thorough the pipes to another facility for treatment or disposal. (Sometimes it goes into special ponds where bacteria render it useful again.)
Geotextile is a fabric that comes in several types such as mailbag sacking, felt or felt with holes. It is normally placed on top of the collection pipe system because it separates solids; the liquid goes through the holes in the weave and prevents the pipes from clogging.
This fabric then has a layer of sand over it, gravel if available, or even a plastic mesh called “geonet.” It is just another way to drain the leaching fluids that will eventually be sent to the pipe system.
There will be trucks, huge bulldozers and giant graders continually covering the waste with six to twelve inches of soil. Referred to as the “daily cover”—it is reducing odors and keeping litter in place. (Not to mention, it deters the birds, rodents and other scavengers who are nearby looking for food.)
On top of the whole shebang will be cover vegetation in areas that are full. Generally, this means native grasses and growing shrubs, plants that to help maintain the soil coverage. Just as a farmer plants “cover” crops to give the soil nutrients and keep the land from blowing away, so is cover vegetation in a landfill.
When a landfill begins to swell with three million tons of garbage, a phenomenon begins: the decomposing products turn into methane or natural gas. Methane is a fast-burning fuel and creates pockets. Some landfills have learned to tap into that and the subsequent gas is used as an energy resource. A landfill containing three million tons of garbage could produce enough gas to fuel 18,000 homes for 15 years!
That’s our tour of a landfill and we have not even talked about hazardous materials, recycling or mass burn—but that’s for another day.