Introduction

After a big holiday meal, what happens to all the leftovers, packaging, and scraps? While much of it might look like “waste,” these materials actually store energy and resources that can be recovered through smart systems and community action. In this activity, students explore how holiday waste can be transformed — from food scraps turned into compost or biogas, to containers recycled into new products, or even extra food redirected to families in need. By sorting, reasoning, and discussing, students will discover how everyday disposal choices connect to broader systems of energy recovery, material reuse, and environmental conservation.

Student Objectives

Students will be able to

• Classify post-meal materials into different recovery pathways — composting, recycling, food donation, and landfill — based on their characteristics and potential for energy or resource recovery.
• Analyze how various waste recovery and reduction strategies conserve or recover energy and reduce environmental impact.
• Apply quantitative reasoning to estimate the energy and emissions implications of different waste-handling choices.
• Evaluate and propose individual or community-level actions that could improve waste recovery or reduce waste generation during the holidays and beyond.

Materials

Per Group

• Student Handout
• Printed Energy Pathway Bin Cards (included below)
• Printed Meal Item Cards (included below)

Procedure

1. Introduction

• Bell Ringer: Waste is created and discarded every day. If we think of waste as stored energy, what kinds of energy could be recovered from it? What would it take to do that?
• Explain that in this activity, students will explore what could happen if communities had the systems to recover energy and materials from holiday waste.
• Show students the Introduction to Energy video to introduce students to the basics of energy and embedded energy.

2. Introduce Categories

• Display or project the Energy Pathway Bin categories on the board and provide a brief description for each (also included in the Student Handout):
  • Compost/Biogas (organic waste): Organic materials can break down naturally into nutrient-rich compost or be processed in special systems (anaerobic digesters) that produce methane gas for heat or electricity.
  • Recycling (uncontaminated paper, metal, plastic): Clean packaging can be reprocessed into new materials, saving large amounts of manufacturing energy.
  • Food Donation (unopened shelf-stable food): Unopened, shelf-stable foods can be donated to prevent food waste and support the community.
  • Landfill (non-recyclable waste): Non-recyclable, contaminated, or synthetic materials end up here, where most of their energy potential is lost.
• Class discussion: Ask:
  • What examples of each category can you think of? 
  • Which of these systems exist in our community? 
  • Where might energy be recovered or conserved in each case? 

3. Sorting Activity

• Divide students into small groups of 2 or 3. Provide each group with a set of meal item cards, a set of energy pathway bin cards, and the Student Handout.
• Following instructions on the Student Handout, each small student group will work together to sort each meal item card under one of the Energy Pathway Bin cards. 

For example: 
A student may start with the meal item card “plastic bags.” The team will decide which Energy Pathway Bin to place that card under – Compost/Biogas, Recycling, Food Donation, or Landfill – and be ready to defend their reasoning.

4. Sharing and Discussion

• After groups have finished sorting all of the meal item cards under energy pathway bins, go through each meal item card as a class. Invite teams to share what energy pathway bin they chose and why. (See Answer Key included below)
• Encourage respectful debate when opinions differ, emphasizing evidence-based reasoning and real-world context. This is a good opportunity to address any misconceptions or assumptions students may have.
• If time allows, continue the discussion until all items are reviewed.

5. Embedded and Recovered Energy Activity

• Introduce the big idea that every material and food item contains energy, either because energy went into producing it (growing, processing, transporting), or it can release energy again (biogas, incineration, etc.).

Key Concepts: 

• Embedded (Embodied) Energy: The total amount of energy consumed (directly or indirectly) to produce a material or product, from raw-material extraction through processing and manufacturing.
• Recovery Potential: How much of that embedded energy is saved or regained through recycling or recovery processes.

Show students the following table of sample values: (also included in the Student Handout)
*Note: Values are indicative and vary by context (energy mix, transport, efficiency, etc.)

Have students complete the Quantitative Reasoning activity in the Student Handout using these data. Encourage comparative reasoning instead of exact precision.

6. Reflect and Analyze Activity

• After completing the sorting and quantitative reasoning activities, students will complete the Reflect and Analyze activity in the Student Handout.
• They will work with their group to answer a series of questions that help them connect their learning about energy recovery and waste systems to everyday decision-making, community practices, and environmental impact.
• Reminding students that local recycling/composting capabilities vary, which can lead to valuable regional comparisons.
• Students will analyze their choices, reflect on challenges and opportunities for waste reduction, and articulate how individual actions fit into broader energy systems.

6. Optional Extension: CER Activity – Recover or Conserve? 

• Provide students with the Extension worksheet from the Student Handout. 
• Using the Claim-Evidence-Reasoning (CER) framework, students apply data from earlier parts of the lesson, along with research, to take a position on the guiding question: Is it better to recover energy from waste, or to conserve it by producing less waste in the first place?

Energy Pathway Bin Cards

Meal Item Cards

Answer Key

Below is a suggested categorization of meal items. While multiple answers may be reasonable depending on local waste systems, this key represents the most accurate pathways based on national recycling and composting guidelines. Encourage students to justify and compare their reasoning to these suggestions.

Quantitative Reasoning: Estimation Questions Sample Student Responses

1. Sample Student Response: Aluminum requires the most energy to produce at 372 MJ/kg and food waste requires the least amount of energy to produce at 7-8 MJ/kg. If the goal is to save the most energy per kilogram, prioritize capturing aluminum for recycling. Materials like food waste have far lower embedded energy, so energy savings per kg are smaller. 
2. Sample Student Response: At a 95% rate of energy recovery, about 353.4 MJ (0.95 x 372) per kilogram of recycled aluminum is saved. 
3. Sample Student Response: Some reasons for paper being recycled more than PET plastic could be the high volumes of paper in households, schools and offices, the established, simple collection and recycling systems in place, and often lower contamination and clearer sorting rules than mixed plastics. I would still target paper first because of its high volume and simpler recycling process, while continuing to improve PET plastic recycling where feasible to tap into its higher per kg savings.
4. Sample Student Response: Source reduction avoids 100% of embedded energy, plus the extra energy used in collection and processing. For example, avoiding 1 kg of PET plastic avoids 60 MJ. Recycling 1 kg of PET saves ~45 MJ. The extra benefit from reduction vs. recycling would be around 15 MJ/kg. 
5. Sample Student Response: I think that the best balance would be achieved when systems for both are established and put in place. Aluminum needs to be targeted because of its high per kg savings, while paper and food also need to be targeted because of their higher usage. 

Analyze and Reflect: Sample Student Responses

1. Sample Student Response: I think that diverting food waste into compost and biogas has the greatest potential benefit locally. Our community generates a lot of organic waste that could be used to create compost for local gardens and, with digesters, be helpful to produce biogas for cooking. It addresses a large waste stream with meaningful environmental and energy benefits.
2. Sample Student Response: We could plan portions and menus better to avoid overbuying. We could use reusable plates, cups and tablecloths instead of single-use plastics and paper. We could set up a compost bin for vegetable scraps, and choose items with minimal packaging. 
3. Sample Student Response: We could reuse glass jars as pantry containers and storage; clean and reuse trays for baking or potlucks; break down cardboard boxes for storage, repackaging and crafts; make stock from bones and vegetable scraps and compost the remainder. 
4. Sample Student Response: Barriers include lack of curbside service and the time it takes to transport to donation sites; confusing rules; limited space (e.g. apartments). Solutions include expansion of curbside programs; educational campaigns promoting clear guidelines; provision of compost kitchen caddies; place public drop-offs. 
5. Sample Student Response: My call to action would be “Plan Smart, Sort Right.” This holiday, prevent waste first, then carefully recycle and compost what’s left. Return cans, recycle clean packaging, and feed soil, not landfills, with food scraps.

Extension Challenge: CER Activity Sample Student Response

Claim: Sample Student Response: I think it’s better to conserve energy by reducing unnecessary or excessive energy use in the first place, rather than relying only on recovering energy from waste afterward. 

Evidence: Sample Student Response: According to the data table, producing new aluminum requires about 372 MJ/kg and recycling saves about 90-95% of that (roughly 335-353 MJ/kg). While those savings are significant, if we can avoid making aluminum packaging that isn’t really needed (like single use cans when reusable containers would work) we save the entire 372 MJ/kg. 

Reasoning: Sample Student Response: The evidence shows that recovery systems like recycling and composting are important, but they happen after energy has already been spent to make, transport, and sell those materials. If we focus on reducing unnecessary energy use, such as making disposable items that quickly become waste, we can prevent the largest energy losses in the system. 

This doesn’t mean stopping energy use altogether. Energy is essential for modern life. But we can be more thoughtful about which energy adds real value and which is wasteful. For example reusing containers, buying durable goods, and planning meals to prevent food waste all conserve energy without reducing quality of life. 

Because of this I can conclude that the most effective approach is to minimize unnecessary energy use first, and then recover as much as possible from what remains.