Lesson: Solid Waste Takes Over

Contributed by: Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder

A colorful photograph of a garbage landfill showing acres of trash. Vultures are hovering over the trash, picking up anything edible.
Figure 1. A typical garbage landfill.
Copyright © Microsoft Corporation 1983-2001.


In this lesson, students explore solid waste and its effects on the environment. They will collect classroom trash for analysis and build model landfills in order to understand the process and impact of solid waste management. Students will understand the role of engineers in solid waste management.

Engineering Connection

Engineers have quite a challenge to find better ways to get rid of our everyday garbage. Bioengineers design systems to destroy wastes and clean up contaminated soil and water. Today, some of our household garbage is recycled and the rest goes to landfills — pits with a protective liner — and each trash layer is covered with a thin layer of soil. Environmental engineers are developing new, innovative landfills to breakdown garbage and create gases, such as methane, used to generate electricity.

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.

Suggest an alignment not listed above

Learning Objectives

After this lesson, students should be able to:

  • Understand and explain different methods of waste disposal.
  • Explain some of the major problems caused by waste disposal and use of landfills.
  • Understand and explain the role of engineers in solid waste management.
  • Suggest ways to reduce the amount of solid waste going to a landfill.


Did you know that most living organisms produce waste products that are safely recycled by the ecosphere? Did you also know that humans are the only species that produce unnatural waste (and we produce it in huge quantities)? Basically, this means that we humans create lots and LOTS of trash. What do you throw away? Do you throw away soda, milk or water bottles, candy and food wrappers, boxes, and/or plastic or paper bags? Does the trash collector remove bags or cans of garbage from your home — and on a larger scale — your neighborhood every week? Do you wonder where all this trash goes? Where is it hauled to after it leaves your home/neighborhood? What happens to it after it gets to where its going? Ask students to brainstorm a list of different ways to dispose of garbage (e.g., burning, burying, shooting into space, etc.) Write the list on the board.

Paper is the largest category of trash that we throw away. Can you think of some paper items you have thrown away just today (e.g., paper bags, candy or other wrappers, newspapers, writing paper, etc.). We call this trash that we throw away in great amounts solid waste. It can be very harmful to the environment. As plastics and other garbage break down and begin to rot, there can be many negative effects to the environment: a dangerous gas — methane — can be released into the air, chemicals that are in or on the garbage might leak out into the ground during rainstorms, and germs, flies, vultures and other nuisances are often attracted to the continual build up of solid waste.

There are several methods that are used to dispose of garbage: creation of landfills (making large piles or pits of trash), incineration or burning of trash, and burying dangerous trash — such as toxic waste. Engineers deal with this enormous trash problem by developing better methods for decreasing, and ultimately, eliminating our nation's overabundance of garbage. For example, household garbage used to be taken to the dump, where it was thrown into a big pit, pile on top of pile, adding mass and height with each dumping. Not only was this an unpleasant sight, it emitted an obnoxious smell and attracted copious amounts of bugs and rats. Today, engineers have developed landfills, which are similar to a dump, but they are lined with a heavy-duty plastic to prevent leaking. Then, every layer of garbage is compressed and covered with a thin layer of soil to prevent air and pests from getting at the garbage. Engineers have also developed systems to collect the methane gas — which is caused from the anaerobic breakdown of garbage — to avoid a gas buildup and subsequent explosion or spontaneous combustion. Some landfills actually use the methane for energy to burn this excess methane gas!

Before beginning the activities associated with this lesson, read students the poem "Sarah Cynthia Sylvia Stout Would Not Take The Garbage Out" by Shel Silverstein (found in Where the Sidewalk Ends, by Shel Silverstein, New York, NY: Harper & Row, 1974). Afterwards, ask the students to describe what they think happened to Sarah. Then, ask what they think happens to garbage when they put it out at the curb or into a trash bin for collection.

Lesson Background and Concepts for Teachers


Scientists are able to learn some about ancient people by studying the methods for their trash disposal (i.e., dumps vs. burying vs. other). Originally, we used dumps (garbage piled on top of more garbage in a big open pit) instead of using landfills, but this created ugly mountains of garbage, attracting rodents and bugs. With every rain, toxic substances were filtered out of the garbage and deposited into the underlying soil. Today, landfills are lined with plastic, and sometimes clay, to prevent leakage into the surrounding soil. Each day's (or a limited amount of) garbage is compressed and covered with a thin layer of soil so that air and pests do not have access to the garbage to either build nests, eat it or spread the trash — potentially spreading harmful diseases. In order to avoid an explosion or spontaneous combustion, pipes placed throughout the layers of garbage collect the build up of methane gas that is generated by the compressed garbage. Some landfills use the methane gas to create energy for other purposes.

Interesting Facts

  • Mile High Stadium — the former home of the Denver Broncos football team and now a parking lot — is built on a sanitary landfill.
  • The world's largest landfill is Fresh Kills Landfill on Staten Island, NY. This monstrous landfill, which officially closed on July 4, 2001, is comprised of 3,000 acres of swampy land 5,000 feet high. This is the largest manmade structure on Earth today (for the 5,000 years previous to today it was the Great Wall of China). Information and a photo tour of the Fresh Kills landfill can be found at: http://www.nycgovparks.org/park-features/freshkills-park.
  • Every day, Americans produce an estimated four million pounds of dangerous (hazardous) household waste. The different types of hazardous waste are described in the Table 1.
  • Sometimes, people do not use appropriate methods for garbage disposal (i.e., landfills). It is estimated that 14 billion pounds of garbage are thrown into the world's oceans each year.

Table 1. Listing of Toxic Household Waste
Table 1. Listing of Toxic Household Waste


Incineration — or the burning of trash — often occurs at temperatures above 1800º F. Because incineration can produce huge amounts of air pollution, the incinerators are often placed on ships that sail at great distances from populated areas. Incineration is beneficial because it can dispose of great amounts of trash very quickly. However there are some downsides to the method of incineration: copious amounts of ash are created as a result of the burning process, which then must be disposed of, and toxic fumes ( dioxins) are emitted into the air (in addition to steam). In fact, the resultant ash can be poisonous if hazardous chemicals (or dangerous solid materials) are not removed from the garbage before it is burned. Engineers are developing methods to reduce air pollution from incineration processes — such as scrubbers that clean the air before it is released into the atmosphere.

In some areas — for example, Denmark — garbage is actually burned to create energy. Another challenge for engineers, then, is to develop alternate ways for this energy conversion to be more efficient, thus creating a method for a viable energy resource.

Burying Toxic/Radioactive Waste

Toxic waste is generated from a variety of sources: from things we use in our homes (see Table 1) or from industrial processes. Radioactive waste comes from nuclear weapons testing (atomic bombs, etc.) and nuclear power plants, and it is most often put into metal containers and buried underground in shallow pits. It is critical that radioactive waste not come in contact with water or air; if such contact exists, the result could be an enormous, devastating explosion. Unfortunately, many of these sites leak, and the toxic waste leaches into our soil and water. Some waste will remain dangerous for thousands of years to come.

Engineers are striving to develop new methods to deal with all types of toxic waste. For example, they are exploring ways to turn toxic waste into glass.

Sometimes trash has nowhere to go. For example, the Mobro garbage barge carried 3,000 tons of garbage from Long Island, NY in 1987. It visited many states and countries, but no one would take the trash (why would they want it, after all!). It wound up back in New York, was incinerated, and left 400 tons of ash that ended up in the landfill anyway! Clearly, sometimes situations just don't work out the way that they were originally planned.


biodegradable: A substance that naturally turns into soil.

composting: Organic trash, such as apples, eggs or bread that very small bacteria, oxygen and moisture are able to turn into "soil."

decompose: An organic process where matter breaks down into its component parts (basic elements) or, in other words, "rots." This process forms methane — a gas.

dioxins: Family of chemicals found in herbicides, bleached paper, incinerated toxic waste, etc. Dioxins are poisonous in extremely small amounts (1 part per billion).

garbage: Food waste or refuse (worthless or discarded items) that is thrown away.

incineration: Burning trash at very high temperatures, which then produces ash.

landfill: A huge pile of trash. Modern "sanitary landfills" are often lined with clay or plastic to prevent leaking of toxic substances, and the solid waste burial is controlled and managed.

leachate: Contaminated liquid produced by water seeping through solid waste (i.e., rainfall seeping through a landfill or mine tailings).

methane: A gas that is colorless, odorless and flammable. Methane is formed when organic matter decomposes.

Not In My Back Yard: (NIMBY) It represents a reaction that community members might have when faced with the prospect of a hazardous waste facility being located near their homes.

pollutant: Any substance that is present in the environment in unnatural quantities, whether it is directly harmful or not.

solid waste: All solid, semi-solid, liquid and gaseous wastes (trash, garbage, yard waste, ashes, industrial/construction waste, appliances/furniture, etc.).

trash: Items that are considered worthless, unnecessary, or offensive and that are usually thrown away. Usually, it is defined as dry material and excludes food waste (garbage) and ashes.

Associated Activities

  • Trash Talkin' - Students will collect, categorize, weigh and analyze classroom solid waste.
  • This Landfill Is a Gas! - Students build and observe a model landfill in order to understand the process and pitfalls of landfill use.

Lesson Closure

Reiterate how important proper waste disposal is and how recycling is important for the environment. Why do we want to recycle? (Answers may vary. Tell students that recycling will help future generations enjoy the environment, too.) What happens to solid waste when it is disposed? (Answer: It can release dangerous gasses, such as methane into the air; chemicals that are on the garbage can leak out into the ground during rainstorms; and a build up of solid waste attracts germs and flies.)

Write the acronym NIMBY on the board. Explain to students that this stands for: Not In My BackYard. Discuss what this means. Is there something they have learned about solid waste that would make NIMBY true for them?



Pre-Lesson Assessment

Brainstorming: Ask students to brainstorm a list of different ways to dispose of garbage (e.g., burning, burying, shooting out into space, etc.) Write the list on the board.

Post-Introduction Assessment

Vocabulary: Read some of the terms from the lesson Vocabulary list and ask students to raise their hands if they know the definition. Tell students they will learn more about these terms during the lesson.

Lesson Summary Assessment

Quiz: Give students the Solid Waste Quiz. Before Question #4, read the poem "We Are the Plooters," to the students (from It's Raining Pigs and Noodles, by Jack Prelutsky, New York: Greenwillow, 2000).


NIMBY (Not In My Backyard) Homework: Have students create a poster, flyer, comic or poem about solid waste and the NIMBY response. Another alternative is to have each student write down and finish the following sentence: "Not in MY backyard will I allow _______________________________." Have students read their answers aloud in class.

Lesson Extension Activities

Try putting the numbers in the How Much Garbage? Worksheet into scientific notation.

Make and implement a plan to reduce solid waste at your school.

Visit your local landfill.

Invite person involved in solid waste management into your classroom as guest speakers (trash companies, recycling centers, EPA employees, city council, etc.)

Watch the video "Garbage Day" available from Child Vision Educational Films, P.O. Box 2587, Los Angeles, CA 90078, (213)463-3165.

Interview grandparents or other senior citizens about solid waste disposal, packaging, etc. during their youth.

Look at "Garbage: How can my community reduce waste?" at: http://www.learner.org/exhibits/garbage/intro.html. Click on the different links to learn about tips to reduce garbage.


Chandler, Gary and Graham, Kevin. Recycling (Making a Better World), New York, NY: 21st Century, 1997.
Prelutsky, Jack. It's Raining Pigs and Noodles, New York: Greenwillow, 2000.
Sakamoto Steidl, Kim. Environmental Portraits – People Making a Difference for the Environment, Boulder, CO: Good Apple, Inc., 1993.
Silverstein, Shel. Where the Sidewalk Ends, New York, NY: Harper & Row, 1974.
Wisconsin Department of Natural Resources, http://dnr.wi.gov/org/caer/ce/eek/earth/recycle/waste.htm
Woodburn, Judith. Garbage and Recycling, Milwaukee, WI: Gareth Stevens Publishing, 1992.


Amy Kolenbrander; Jessica Todd; Malinda Schaefer Zarske; Janet Yowell


© 2005 by Regents of the University of Colorado.

Supporting Program

Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder


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.