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Recommended grade level: 4 – 8
Presentation time: 50 minutes
A dump is a large, unprotected hole in the ground that was once open for public dumping of any waste materials. Chemicals from the trash deposited in dumps soaked into the ground, thus contaminating groundwater. Simultaneously, hazardous materials and other chemicals were possible environmental and health threats to humans and ecosystems. Due to the risks and hazards associated with old dumps, federal legislation now requires that all solid waste be placed in sanitary landfills, which are regulated and designed by engineers. Using Federal EPA regulations, landfills in Saint Louis County are inspected and monitored by the Missouri Department of Natural Resources and the Saint Louis County Department of Health. Dumps are now illegal.
Landfills are required to have layers of protective material between the ground and the area where solid waste is deposited. Protective materials consist of a layer of clay on top of the soil, at least one synthetic plastic liner, a cushion of sand or gravel and a system of pipes to collect the liquid, or leachate, from decomposing trash. When landfills close, more clay and protective lining material is placed on top of the solid waste so the entire area of trash is enclosed. To insure that no waste escapes into the groundwater below or the environment above, the landfilled material is in an enormous “bubble”. This area may be turned into greenspace, such as ball fields, bike paths, ski slopes or parks. Buildings and houses are never constructed atop landfills because laying the foundation would require digging into the landfill.
Due to entrapment of the solid waste and the absence of natural elements necessary for decomposition, landfilled garbage does not decompose quickly. Methane gas is created, however, by the microorganisms which break down the trash. This gas, which is flammable and combustible, must be extracted from the landfill. Another system of collection pipes is built into the landfill to collect the methane gas. Landfills can then do one of two things: burn off the gas into the atmosphere or use it as fuel for generating electricity for heating buildings and homes. Methane is a significant greenhouse gas.
- Class handouts for each student
- Landfill Box (a box with layers simulating a landfill, including percentages of trash, as printed later in this lesson)
- Container of fruit cocktail tinted brown with food coloring
- Clear plastic tub
- Food Strainer
- Plastic wrap
- Towel/sponge to wipe off tabletop
1. Student Drawing Activity
- Without mentioning the words dump or landfill, instruct students to draw where their trash ends up when it’s taken away. Allow ten minutes for this activity. If students finish while others are still working, ask them to fill out the chart on the back of their sheet. Instruct them to list items they have thrown away in the last 24 hours.
- When all students are finished with their drawings, ask a few students to briefly describe where “away” is.
2. Landfill Simulation
- Most likely, pictures will be of old dumps. By using fruit cocktail and various containers, you can demonstrate the difference between a dump and a landfill. Tell students the fruit cocktail represents their trash, the strainer is the dump and the tub is the ground. With the tub under the strainer, pour the fruit cocktail in the strainer (this represents what happened to trash in old dumps), allowing the liquid to flow into the tub. Ask them what’s happening (the ground is being contaminated). Write leachate on the blackboard and define it as the liquid waste runoff from trash in landfills. Refer back to the demonstration and ask what’s under the ground that we use every day and could not live without (groundwater). Aquifers hold water, and if that water is contaminated with our trash, it becomes dangerous to drink. At this point, put the fruit cocktail into its original container so you can do the experiment again.
- Ask students to think of ways to prevent the leachate from contaminating the groundwater. (Don’t let it run into the ground.) When they suggest a liner, place the plastic wrap in the strainer. Repeat the experiment with the plastic wrap in place (this represents what happens in a modern landfill with a synthetic liner). Ask the students what the difference is between the two procedures and how this could explain the difference between dumps and landfills. Ask them how to collect the leachate from the container. (In landfills, pipes are used like vacuums to suck up leachate and it is transported to a water treatment facility; the straw should be inserted into the tub to represent this.)
3. Examining the Landfill
- Uncover the landfill box and allow students to observe the arrangement of layers and the trash inside. Point out the leachate and methane collection pipes on top of the clay and plastic liner. Explain that this first layer of garbage in a landfill is called “Fluff lift” and includes all household waste—items small enough that they will not damage the underlying structure of the landfill liner and piping systems.
- Allow them to ask questions and internalize the visual representation of the structure.
- Ask students what they think will happen to the trash in the landfill over time; will it break down? Ask students what elements must be present for decomposition to occur (sun, water, air, microorganisms). Explain that little decomposition occurs due to lack of necessary elements, but it does happen at a very slow rate. Ask what is responsible for helping trash decompose in the landfill. (Anaerobic microorganisms.) Using analogies, perhaps to moldy food in the refrigerator, help students to understand how decomposition happens in an enclosed area. They may have noticed a food container expanding as mold grows on the food; this is analogous of methane gas being created in a landfill. Ask what would happen if that gas were left in the landfill and why it’s necessary to remove it. (It could explode!) Using the information provided in the background section, explain what landfills do with the methane gas produced.
4. Our Garbage
- Direct students back to their picture. Did they draw any trash? If not, ask students to refer back to the pre-activity and the items they threw away. List the following categories of trash on the board with the percentages in another column (out of order). Tell students they’ll play a matching game to determine what percent matched with each category. Paper (34%), plastic (17%), glass (5%), metal (6%), organic (32%),non-organic (4%) and special waste (2%). (2007 Missouri Solid Waste Composition Study).
- Have students test their landfill knowledge by designing their very own sanitary landfill (Landfill structure design worksheet). They can answer related question on the back.
- Referring to categories and percents, discuss what other options we have than landfilling our garbage. Can the items listed be used for another purpose? Explain that recycling makes better use of our resources (by giving new life to items that still have value) and saves landfill space. Are students already recycling at home and school?
- Time permitting, review a few items students wrote on their charts and the various resources used to produce each item. Evaluate items according to the columns listed, discussing whether the item could have been reduced. If this item is not compostable or recyclable, are there any other alternatives that could have been used that are more environmentally friendly?
- Visit a local landfill. Talk to the manager or technician about EPA regulations, procedures, daily activity and how they control and use the leachate and methane gas.
- Conduct a waste inventory of your school. Are there any items being discarded that could be reduced, reused or recycled?
- Is your school currently recycling paper? Aluminum cans? Cardboard? Composting food waste? Determine if there are any projects your class can undertake.
For additional worksheets, please see the links below: