What is Composting?

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SWBAT describe the importance of decomposers in composting.

Big Idea

In this lesson, students will sort biodegradable and non-biodegradable materials. Then, teams of students will research the question, "What is composting?" and will make an idea web on a team poster.

Lesson Overview

Inquiry Based Instructional Model

To intertwine scientific knowledge and practices and to empower students to learn through exploration, it is essential for scientific inquiry to be embedded in science education. While there are many types of inquiry-based models, one model that I've grown to appreciate and use is called the FERA Learning Cycle, developed by the National Science Resources Center (NSRC):

1. Focus

2. Explore

3. Reflect

4. Apply

A framework for implementation can be found here

I absolutely love how the Center for Inquiry Science at the Institute for Systems Biology explains that this is "not a locked-step method" but "rather a cyclical process," meaning that some lessons may start off at the focus phase while others may begin at the explore phase. 

Finally, an amazing article found at Edudemic.com, How Inquiry-Based Learning Works with STEMvery clearly outlines how inquiry based learning "paves the way for effective learning in science" and supports College and Career Readiness, particularly in the area of STEM career choices. 

Unit Explanation

In this unit, students will first develop an understanding of the biotic and abiotic factors within ecosystems, the characteristics and classification of living organisms, and how plants and animals obtain and use energy to fulfill their needs. 

Then, students will delve deeper into the NGSS standards by examining the interdependent relationships within an ecosystem by studying movement of matter between producers, consumers, and decomposers by creating models of food chains and food webs.  

At the end of this unit, students will study ways that individual communities can use science ideas to protect the Earth's resources and environment.  

Summary of Lesson

Today, I will open the lesson by asking students to sort biodegradable and non-biodegradable materials. Students will then research the meaning of composting and create a team poster. At the end of the lesson, students will reflect and apply their new understanding of composting by sharing their research with the rest of the class.

Next Generation Science Standards  

This lesson will support the following NGSS Standard(s):

5-LS2-1.    Develop a model to describe the movement of matter among plants, animals, decomposers, and the environment.  

5-ESS3-1.  Obtain and combine information about ways individual communities use science ideas to protect the Earth’s resources and environment.

Scientific & Engineering Practices

For this lesson, students are engaged in the following Science & Engineering Practice:

Science & Engineering Practice 8: Obtaining, Evaluating, and Communicating Information

Studnets will read an online resource to obtain ideas on composting. Then students will communicate this information by creating an idea web on a team poster. 

Crosscutting Concepts

To relate ideas across disciplinary content, during this lesson I focus on the following Crosscutting Concept

Crosscutting Concept 5: Energy and Matter

Students will examine how decomposers help recycle matter (chemical nutrients) back to the soil during the composition process. 

Disciplinary Core Ideas

In addition, this lesson also aligns with the following Disciplinary Core Ideas

LS2.A:  Interdependent Relationships in Ecosystems

The food of almost any kind of animal can be §traced back to plants. Organisms are related in food webs in which some animals eat plants for food and other animals eat the animals that eat plants. Some organisms, such as fungi and bacteria, break down dead organisms (both plants or plants parts and animals) and therefore operate as “decomposers.” Decomposition eventually restores (recycles) some materials back to the soil. Organisms can survive only in environments in which their particular needs are met. A healthy ecosystem is one in which multiple species of different types are each able to meet their needs in a relatively stable web of life. Newly introduced species can damage the balance of an ecosystem. (5-LS2-1)

LS2.B:  Cycles of Matter and Energy Transfer in Ecosystems

Matter cycles between the air and soil and among plants, animals, and microbes as these organisms live and die. Organisms obtain gases, and water, from the environment, and release waste matter (gas, liquid, or solid) back into the environment. (5-LS2-1)

ELA Integration

To add depth to student understanding, when I can, I'll often integrate ELA standards with science lessons. Today, students will work on meeting CCSS.ELA-LITERACY.RI.5.2: Determine two or more main ideas of a text and explain how they are supported by key details; summarize the text. In this lesson, students will be locating key details that answer the question, "What is Composting?" 

Choosing Science Teams

With science, it is often difficult to find a balance between providing students with as many hands-on experiences as possible, having plenty of science materials, and offering students a collaborative setting to solve problems. Any time groups have four or more students, the opportunities for individual students to speak and take part in the exploration process decreases. With groups of two, I often struggle to find enough science materials to go around. So this year, I chose to place students in teams of three! Picking science teams is always easy as I already have students placed in desk groups based upon behavior, abilities, and communication skills. Each desk group has about six kids, so I simply divide this larger group in half. 

Gathering Supplies & Assigning Roles

To encourage a smooth running classroom, I ask students to decide who is a 1, 2, or 3 in their groups of three students (without talking). In no time, each student has a number in the air. I'll then ask the "threes" to get certain supplies, "ones" to grab their computers, and "twos" to hand out papers (or whatever is needed for the lesson). This management strategy has proven to be effective when cleaning up and returning supplies as well!  


20 minutes

Lesson Introduction & Goal 

I introduce today's learning goal: I can describe the importance of decomposers in composting. Can anyone remind me... what is a decomposer? Students refer to the Decomposer Poster from a previous lesson. (A decomposer is a living organism that breaks down organic matter, making nutrients available to plants.) 

I continue: Today, you are going to begin researching what composting means! This is important because tomorrow, you'll need your research to create three different compost bins. 

Biodegradable & Non-Biodegradeable Materials

In order to create compost bins, it is first important for you to understand the difference between biodegradable and non-biodegradable materials. 

Prior to this lesson, I print and cut out the following Biodegradable Sort "cards." At this time, I place the biodegradable and non-biodegradable headings on the board and explain: Biodegradable materials can be decomposed by bacteria and other living organisms. On the other hand, non-biodegradable materials can't be decomposed by bacteria and other living organisms. Turn and talk! What's the difference between biodegradable materials and non-biodegradable materials? 

As students turn and talk, I take this opportunity to hand out the biodegradable sort cards to random students. Then, I ask students to discuss the materials on their cards and to determine if the materials are biodegradable or non-biodegradable. During this time, I conference with students: Teams Discussing Biodegradable Materials. They ended up with one of the trickiest materials - a cotton shirt. We discuss how a cotton shirt is composed of cotton fiber, which come from the cotton plant. For this reason, a cotton shirt would be biodegradable. 

Next, I ask students to place their cards under the correct heading on the board: Biodegradable & Non-Biodegradable Lists. I ask other students to turn and talk about both lists: Do you agree with the placement of materials? Are there any you respectfully disagree with? 

After some time, we discuss the lists as a class: Group Discussion. A pretty powerful conversation resulted as some students disagreed with the placement of man-made materials, such as paper, cardboard, and cotton shirts under the biodegradable column. We then discuss how all of these materials are made with cotton or wood, which is biodegradable.


I want to inspire interest in today's lesson and capitalize on student curiosity, so I show the following video clip featuring a boy that uses worms to decompose organic waste: Kevin's Worm Farm. In particular, I love how he addresses the importance of composting. He explains that organic waste just adds to the piles of garbage at landfills. This makes it all the more meaningful for students to create compost bins as well. 


35 minutes


Following the video, I ask students what types of questions they want to research today before creating compost bins tomorrow. I list student questions on the board as they share them with the class: Student Questions. The letters at the beginning of each question correspond with first letter of the student's name asking the question. I'm impressed with each of the questions and am reminded of the importance of allowing student inquiry to guide student research. 

Compost Web

I hand out a poster (11x17 paper) to each group and show students how to create a compost idea web: Composting Web Model. I ask one student from each group (such as the #3 students) to get their computer and to go to the following composting resource (pages 3-5). I also ask for each student to write with a different colored marker to ensure that all students are equally participating. 

Monitoring Student Understanding

Once students begin researching, I conference with every group. My goal is to support students by asking guiding questions (listed below). I also want to encourage students to engage in Science & Engineering Practice 7: Engaging in Argument from Evidence

  1. What patterns have you noticed? 
  2. Why do you suppose ____? 
  3. What have you found so far? 
  4. Has your thinking changed? 
  5. What evidence do you have? 
  6. How did you decide _____?
  7. What conclusion can you draw about ____?

Student Conferences

During this conference, Conference #1, the students explain why composting is important. I like how one student makes personal connections with his research by explaining how his mother could use composting in her garden.

Here, Conference #2, the students explain how they plan to make holes in their compost bins to make sure the scavengers in their compost piles have enough air. 

Student Work

Here are a few examples of student research posters during this time: 


Overall, I felt that all students did a great job participating and collecting relevant information! 

Reflect & Apply

5 minutes

Sharing Findings

Now that students have built meaning and understanding through research, it is important to provide students with the opportunity to share their findings. For this reason, I invite students to discuss their findings with the rest of the class.

During this time, I create a list of student findings on the board: Student Findings. In particular, I try to record the facts that are pertinent to know when constructing your own compost bins. For example, tomorrow, students might tear up their organic matter (such as the piece of bread) because the text says that "small pieces of organic matter decompose faster."