Hands-on Activity Design, Build and Test Your Own Landfill

Learning Objectives

After this activity, students should be able to:

• Describe a landfill and its purpose.
• Explain the alternatives to dumping human-made garbage in landfills and ways to decrease the amount of waste that ends up in landfills.
• Describe how landfills can be hazardous for the environment if they are not well engineered.
• Describe the kinds of materials make good liner systems for landfills.
• Explain what it means to optimize something.

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

NGSS: Next Generation Science Standards - Science

Common Core State Standards - Math

International Technology and Engineering Educators Association - Technology

State Standards

Materials List

Each group needs:

• clear plastic tub (~12-in long × 6-in wide × 5-in deep) (~30-cm x 15-cm x 13-cm) with about 1 inch (2.54 cm) of sand in the bottom
• clay (~750 cm³), this clay does not need to be the high-quality type used for modeling; clayey or silty soil from your backyard works fine
• sand (~1500 cm³) (available at home and garden stores)
• gravel (~100 cm³) (available at home and garden stores)
• ~15 cotton balls
• (optional) tiny houses and buildings (such as Monopoly game houses and hotels), or any other simple representation to simulate the presence of a town sitting on the sand base
• Roles and Optimization Worksheet
• Budget Worksheet

Note: The amounts of clay, gravel and sand are approximate (based on experience with teaching the activity), but because students can choose how much of each type of material they want to use, it is helpful to have a bit extra on hand.

For the entire class to share:

• food coloring
• clear plastic tub in which to mix together food coloring, water and cotton balls ("garbage")
• (optional) gloves or spoon to "mix" the garbage
• strips of plastic garbage bags, to simulate geosynthetics used in landfills
• toothpicks
• straws
• popsicle sticks
• small, paper "Dixie" cups (~85 ml size), to measure and distribute clay, gravel and sand
• access to water
• watering can, water bottle or other "rain storm" device
• (optional) electric fan, to simulate the erosion force of wind
• (optional) graph paper

Worksheets and Attachments

Pre-Req Knowledge

A basic understanding of what water (and, hence, leachate) does and does not flow through. Specifically, water flows very slowly through clay so clay is a good material for a landfill liner system.

Introduction/Motivation

The people living in the US make about 250 million tons of trash every single year! (EPA, 2009) And, about 300 million people live in the US. So, that works out to about 4½ pounds of trash generated per person — every single day!

How much of this garbage do you think gets recycled and composted? Only about one-third of this trash gets recycled or composted, which means that on average, you make three pounds of trash every day that we have to put somewhere (and the US makes 470 tons of trash every day).

Where do you think we should put this trash? Can we just dump it out in a field? Why not? What if the dump or landfill is near a lake or a river? Groundwater that is stored in aquifers is always flowing. People use wells to bring groundwater up from the aquifers to drink. We must keep dirty water that comes from the landfill (leachate) from getting into the groundwater, otherwise we can make people sick.

So what should be put underneath all the trash in the landfill? How about once the landfill is finished? Should we cover the landfill or leave it open to the air? What should we cover it with? Erosion can affect your landfill if you are not careful. Landfills must be designed well enough to withstand erosion from rain, wind or even earthquakes. Let's make some models and learn what works best.

Procedure

Before the Activity

• Gather materials and make copies of the Roles and Optimization Worksheet and Budget Worksheet.
• Prepare for each group a tub with a bottom sand layer to serve as a landscape upon which to build a landfill (see Figure 1). Set up a town using small houses (or other materials) to represent a population using the groundwater (for drinking, cooking, cleaning, gardening, recreation, etc.).
• Prepare the "garbage" by mixing cotton balls, food coloring and water (see Figure 1).

With the Students: Create Model Landfills

1. Divide the class into groups of four students each. Hand out the Roles and Optimization Worksheets.
2. Assign each group member one of four team roles (or let the students decide amongst themselves). Have them indicate on their worksheets who is responsible for each role.

• Project engineer: The project engineer is the project leader. This person is in charge of final decisions. S/he listens to all of the engineers and helps to decide the best idea. S/he makes sure the landfill gets built on schedule.
• Design engineer: The design engineer plans how the landfill will work and look. This person is in charge of picking materials and deciding how the landfill should be built. S/he works with the budget office (when picking materials) and construction engineer (when deciding how to build the landfill).
• Construction engineer: The construction engineer builds the landfill. This person gets the plans about how to build the landfill from the design engineer. If the landfill design must be fixed, s/he talks to the budget office about getting more or different materials.
• Budget office: The budget office makes sure that the project spends the least amount of money possible. This person helps the design engineer pick materials. S/he is in charge of filling out the budget worksheet, doing the calculations, and keeping track of how much money has been spent. You cannot go over budget!!

3. Introduce the project objectives to the students: Each group must design a landfill that 1) can hold the most garbage, 2) minimizes the cost, while making sure that, 3) the landfill is able to contain the waste during a rainstorm without allowing leachate to get to the town. As you do this, just like engineers, you will be following the steps of the engineering design process: understand the need, brainstorm different designs, select a design, plan, create, test, analyze and improve.
4. Hand out the budget worksheets to the "budget office" students in each group and talk with them about the different materials.
5. Have the "design engineer" students draw out his/her team's landfill design and complete the budget worksheet. If time permits, have the "design engineer" calculate the volume of the plastic bin and compare this to the volumes of materials (e.g., sand, clay, etc) they are using. Note: 1 cup ≈ 15 in³.
6. Sign-off on the engineering landfill designs and budget worksheets for each group.
7. Have students bring both their approved (signed) designs and completed budgets to the "supply shop" to get their supplies.

8. Have students construct the base liner systems for their model landfills (see Figure 2). The goal is to keep water from getting out of the landfill. Therefore, materials such as clay and geosynthetics are good choices, because water cannot flow through them easily. (Basically, the liner should look like a clay bowl or box. Of course, not all teams will choose this path — so you may see Popsicle sticks, toothpicks, etc., at this stage. The word "system" is used because students can use a combination of materials to make base liners [however, because of the budget constraint, they cannot afford to buy many things].) Remember to save some funds to purchase materials to build your top cap (to put on after the garbage is inserted). A landfill without a top is no good for anybody!
9. Fill the landfill with "garbage" (see Figure 2) making sure not to let the food coloring seep out into the area around the landfill before construction is completed. Count how many cotton balls you put in. Have the Project Engineer tell you how many to put in.
10. Have students record the quantity of garbage cotton balls that their landfills can hold on the worksheet.
11. Give students time to finish constructing the top cap liner systems for their landfills (see Figure 3). The purpose of the top cap is to keep the rain out of the landfill. Therefore, like the bottom liner system, it should be made of materials water cannot flow through. Additionally, some protection (such as gravel) can be placed on top to keep rainwater and sunlight from eroding away the liner.

With the Students: Test Landfill Performance

1. Create "rainstorms" by pouring water on the model landfills (see Figure 3).
2. Use a pencil or Popsicle stick to dig into the sand outside of the landfill and near the town to look for any seeping food coloring (leachate) (see Figure 4). Make multiple soils tests.
3. Repeat the rainstorm, if desired.
4. (optional) Apply other erosion forces to the model landfill, such as wind or earthquakes.

5. Have students document on their worksheets the performance of their landfills (how much garbage it held, how much it cost and whether or not it leaked).
6. Once students have recorded the garbage capacity, cost and performance, have them present their designs to the class. See the embedded assessment "Design Presentations" questions in the Assessment section.

With the Students: Design Comparison

1. Create a table that compiles data (amount of garbage, cost and performance) from each group.
2. Present the data on large, colorful posters.

• Make a line graph of the amount of garbage each landfill held.
• Make a line graph of the cost of each landfill.
• Make a line graph of the performance of each landfill (rate as pass/fail or on a 1-to-5 scale).

3. Discuss the differences between presenting data in graphs as opposed to tables.
4. Lead a class discussion that compares and analyzes all group data. Analyze similarities and differences among the several design solutions to identify the best characteristics of each that can be combined into a new solution to better meet the criteria for success. Explore the concept of optimization. Use the post-activity assessment questions provided in the Assessment section. Determine which landfill is most optimal.

Vocabulary/Definitions

anthropogenic: Created by people or caused by human activity.

aquifer: An underground layer of permeable rock, sand, gravel or soil that contains or conducts groundwater. The pore spaces in aquifers are filled with water and are interconnected, so that water flows through them. Source of water for springs and wells.

geosynthetic: Human-made materials for earth systems (such as landfills, dams, roads and retaining walls).

impermeable: A material characteristic that does not allow a fluid (such as water) to flow through it.

landfill: An engineered site used to dispose of garbage by burying it.

leachate: Contaminated water that seeps out of landfills. Often contains high amounts of organic matter and toxic chemicals.

liner system: The technical term for the layers of materials (such as clay and geosynthetics) that protect landfills from erosion, and keep trash and leachate from escaping from landfills.

optimize: To make a system as good or functional as possible.

requirement: What a particular product, system or service should do. A necessary attribute, capability, characteristic, quality or limitation. In engineering, sets of requirements are inputs into the design stages of product development.

Assessment

Pre-Activity Assessment

Brainstorming: Engage the students in open discussion as a class. Remind them that no idea or suggestion is "silly." All ideas should be respectfully heard. Ask the students:

• What can we do with garbage that does not get recycled or composted? (Answer: Put it in landfills.)
• How might we decrease the amount of trash that gets put in landfills? (Possible answers: Do a better job recycling, use less packaging, reuse more things, do more composting, burn our waste, use fewer things [buy fewer clothes, toys, products, etc.].)
• What materials do we want to use to use to keep garbage "juice" (leachate) from flowing out of our landfills? (Possible answers: Impermeable materials, low-permeability materials, clay.)

Activity Embedded Assessment

Activity Worksheets: Have student teams complete the Roles and Optimization Worksheet and Budget Worksheet. Gauge their understanding of the subject matter by observing their use of the worksheets.

Design Presentations: Have groups present descriptions of the model landfills they designed and created, addressing the following questions:

• Did your landfill keep the town safe? Why or why not?
• What was the most effective part of your design?
• What was the least effective part of your design?
• How did the different materials perform?

Post-Activity Assessment

Optimization Discussion: Lead a class discussion asking students the following questions:

• What does optimization mean? (Answer: For any given engineering challenge, many possible design solutions exist. In engineering, optimization means finding the best solution, which is usually a compromise among several often conflicting requirements [such as cost, capacity, performance, etc.].)
• Which group had the most optimal design (most garbage, least cost and best performance)?
• What were some characteristics of good vs. bad designs?

Safety Issues

• If using a fan to simulate wind, watch that students are not too near to the landfill model that dirt blows into their eyes.

Activity Extensions

Give students more time and different project constraints to redesign and rebuild their landfill models. For example, change the price of the materials and see how that affects the landfill designs. Or, require each landfill to hold at least a certain amount of trash (cotton balls). Or, have the class collectively make a new design that incorporates the best aspects of all the designs, as well as improvements suggested through testing.

Activity Scaling

• For lower grades, give a far more specific design with more constraints. For example, only allow the use of clay. See which group can use the least amount of clay to hold the most trash. Walk the students through the activity step-by-step. Build the bottom liner as a class. Help each group to make sure they are successful.
• For upper grades, put a tracer in the "garbage" and do chemical testing of the water seeping out of the landfill. For example, one simple tracer to measure for is pH. Lemon juice has a low pH and can be measured with litmus paper. Then have students discuss how to clean up the acidic leak (such as by adding a material with a higher pH, such a baking soda).
• Vary the activity to suit the class and available supplies. Perhaps leave the material choices more open ended, and/or add the idea of removing leachate from the landfill (using straws, turkey basters, etc.). Have teams design and build the best model landfill possible.

Additional Multimedia Support

Look online for example diagrams of how engineers have designed landfills. Examples:

https://www.mackinac.org/media/images/2007/ms2007-01-12a.jpg

http://www.pollutionissues.com/images/paz_02_img0144.jpg

Review the steps of the engineering design process at https://www.teachengineering.org/engrdesignprocess.php

References

Copyright

Contributors

Supporting Program

Acknowledgements

The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.