Teacher resources and professional development across the curriculum

Teacher professional development and classroom resources across the curriculum

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The Science and Problem of What We Throw Away

What Happens to What We Throw Away?

Learning Targets

  • I can describe types of waste and what happens to them in my community.
  • I can discuss pros and cons of different ways of dealing with garbage, such as landfilling, recycling, and composting.
  • I can collect data and present it in percentages (and if appropriate, in graphs and tables).


Garbage is complex. Even when citizens make an effort to sort their waste into glass, paper, recyclable plastic, and food, many items are hard to classify or contain a mixture of materials. Some items will always escape the collection system and end up where they can be harmful, such as parks, roadsides, or the ocean.

A majority of waste in the United States is sent to landfills to be buried, and for items that do not break down over time, stored. The United Kingdom, Spain, and Portugal also send about 50 percent or more of their trash to landfills. In Northern Europe, 30 to 50 percent of rubbish is burned in modern incinerators that trap pollutants and use the energy for heat and electricity. Some U.S. waste is also burned: in 2011, according to the U.S. Environmental Protection Agency (EPA), 25 states had facilities to burn waste for energy. (Use the Columbia University Waste map to see your state. See link in References and Further Reading.) Also according to the EPA, in the United States in 2011, about 35 percent of the 250 million tons of garbage generated in a single year was recycled and composted. This activity focuses on garbage that is destined for landfills, recycling, or composting.

Note: When discussing this topic with students, best practices in environmental education advise sharing information only, not imposing values. For this topic, pointing out the value of reusing, recycling, or composting could be balanced with discussions or assignments about the costs of transporting and processing reused, recycled, or composted materials, or about the difficulties of recycling in a city that does not have a widespread recycling program.

The photographs in this exercise show typical American garbage; however, landfills around the world generally look the same.

Begin the Activity


  • Photos printed large enough to identify individual waste items
  • Information on school or community recycling, reusing, and composting policies
  • Rulers, pencils, graph paper

Review the categories of items that the school or the community recycles, reuses, or composts. In pairs or small groups, give students handouts of the photos that are large enough to identify and count individual items. Ask students to categorize and count items that they think might be recycled, reused, or composted. Have them describe why they think the item could be removed from potential landfilling and why. For mixed-material items, ask what processing or disassembling might be needed.

Based on counts from the photographs generated in the pairs or small groups, have students estimate or calculate the percentage of garbage from the collections in the photographs that might be recycled, reused, or composted. If time permits, data from the entire class could be combined for an estimate or calculation from all photographs.

Optional: Depending on the data-organizing and data-presenting methods that your class has been learning, students might make T-charts, bar graphs, or tables of their waste counts. If they have learned percentages and pie charts, they might categorize the waste items they see in the photographs into the same categories as those designated in figure 3 on the EPA Municipal Solid Waste website (http://www.epa.gov/epawaste/nonhaz/municipal/index.htm).  Students can convert category counts into percentage of total garbage, and put the results into a pie chart for comparison with the EPA chart. In any case, remind students to label the entire graph and, if appropriate, divide and mark the X and Y axes and label divisions, categories, and axes. For numerical divisions, start axes at zero. For all tables or charts, provide a title and legend if needed.

Encourage students to be objective. They should categorize and count items without judging what should have been done with them. Note that they must make decisions about what categories to make and how to define the categories (e.g., what counts as plastic, paper, etc.). Remind them that this is what scientists do when they plan experiments and collect data. Tell them to write down their methods: how they defined different types of waste—for example, by identifying particular colors, shapes, or textures; how they resolved unclear items; whether they counted the entire collection in the photograph or counted a representative sample area; and so on. Have them convert category counts into percent of the total waste counted to make comparisons easier.

Ask students to share their results, describing the decisions they made and why they made them; what items were particularly difficult and how they decided to categorize challenging items; and their interpretations about the amount of garbage that might be reused, recycled, or composted. Ask which results were expected and why, and which results were surprising and why.

Questions to Consider

Q: Compare your results to the EPA estimates of percent of waste in different categories. Do the photographs and your results confirm or contradict EPA estimates of categories of waste? (Option: use local numbers if available.) If results are different among student groups or compared to local or national numbers, what are some possible reasons?

A: Answers will depend on students’ results. See the EPA site in References and Further Reading and local resources for comparisons. For differences in results, have students look at the methods they wrote. They might name sample size, sample representativeness, and decisions about what to include in each category.

Q: Does the source of the photo (researcher, news media, blog post, etc.) affect your opinion about whether the photographs were manipulated or staged? Does the photograph present a particular point of view that makes the waste appear a certain way?

A: Photo sources are in the photo captions.

 Q: Can you think of any applications for your data? (For example, if you analyzed your school’s waste, how might the school use the data? Why might the city or the EPA be interested in this kind of data?) What features of your data do you think are the most convincing? (Which calculations or estimates do you have the most confidence in and why?)

A: A school, community, or country might be interested in knowing if it is meeting recycling goals or what types of items are being thrown away. It might use this data to evaluate its recycling and composting policies and make decisions about whether to focus waste-management resources on landfills, recycling, combustion facilities, or other methods.

Q: If your results were different from other groups, what features of your group’s data collection methods might have led to the differences?

A: Students might have had different photos, with garbage collected from different places. Groups might have defined plastics, paper, and so on more broadly or narrowly. They might have made different decisions about mixed-material items or other items that were difficult to categorize. They might have used different methods to identify difficult-to-categorize items (for example by color or shape). Groups might have decided to count the entire photo or a section.

Q: What are some advantages and disadvantages of reusing, recycling, and composting compared to: 1) sending waste to a landfill? 2) burning waste for energy?

A: Students might think of the costs in machines and employee time of sorting items for recycling. They might think of transport costs. In 2010, according to Edward Hume’s book Garbology, our two highest exports to China, by volume, were waste paper and scrap metal shipped to the country for recycling. The MIT Trash Track project used cell phone technology to monitor individual discarded items. It found that hazardous waste items such as electronics traveled more than 1500 kilometers (900 miles) on average to get to specialized recycling facilities. One printer cartridge traveled more than 6000 kilometers (3800 miles). Students might also think of the water, chemicals, and energy used to process recycled and reused items. The Slate articles in the References and Further Reading section give some considerations.

next: Processing Waste

Grade Level

Middle & High School


Earth and Space Science
Life Science
Social Studies


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