Garbage – Reduce, Recycle and Reuse

Online Lesson Plan
Garbage – Reduce, Recycle and Reuse

lrKathyIn the early 1930s, only a small fraction of the farms in America had electrical power like we have today. Rural residents either made do with kerosene lamps for light and ice boxes for refrigeration, or they bought and rigged up elaborate battery systems. Neither solution put out much light. This lesson builds on these facts to explore batteries and electrical power.

Lesson Plan by Kathy Jacobitz, science education consultant, Pawnee City, Nebraska.


Suggested grade level – 5th-8th.

  • standards02The students will design an experiment given a problem, collect data, graph results and make a conclusion based on the data.
  • The students learn the use of controls and variables in an experiment.
  • The students will recognize the impact of placing manure, a free fertilizer, on fields for better crop production during the 1930s.
  • The students will learn the values of composting during the 1930s and now.
  • The students will investigate the process in which occurs in a compost pile.
  • The students will investigate the parameters, which influence the rate at which decomposition occurs.
  • The students will explore the impact compost has as a chemical fertilizer.


crops0801Composting is a way of using waste products from the kitchen or yard to make nutrient rich humus-like substance. This organic fertilizer can be used instead of chemical fertilizer on garden vegetables or houseplants today.

Composting increases the soil’s ability to hold water and makes the soil easier to cultivate. In China, farmers dig parallel trenches and fill them with organic waste mixed with cocoons of Eisenice Fetida. Soybeans are planted in rows between the trenches and are highly productive.

Composting also helps the soil retain nutrients needed for proper plant growth. Not only do plants need water and sunlight to grow they require nutrients found in the soil to produce a good crop.

Whether you are using organic material on a field or garden you are applying a chemical fertilizer to your soil with the hope of increasing the crop yield.

The students will explore through an investigation the value of composting and answer the question, “What happens during the process of decomposition?”.


  • Fertilizers
  • Composting in the Classroom: Scientific Inquiry for High School Students by N. M. Tratmann and M. E. Krasny. (ISBN 0-7872-4433-3)
  • The Magic School Bus: Meets the Rot Squad by Joanna Cole.
  • Bottle Biology: Using Soda Bottles in the Classroom, 2460 Kerper Boulevard, P. O. Box 539, Dubuque, Iowa 52004-0539.
  • Compost! Growing Gardens from Your Garbage by Linda Glasser.




What happens to the temperature inside a compost chamber?

Students should perform a KWL – What We Know / What We Want to Know / What we Learned – about compost. Each student needs to make a journal entry. Follow the individual KWL with a class KWL. Click here for a KWL format. Click here for journal examples and for a journal assessment. Student investigation sheets are available by clicking here.




Materials Needed:

Materials listed will be for students working in small groups.

  1. A liter or 3 – liter soda bottle.
  2. Thermometer that will fit into the top of the soda bottle and be long enough to reach down into the center of the compost.
  3. A small plug for the top of the bottle with a hole in it for the thermometer to fit through. You may use clear duct tape to seal the bottle top and hold the thermometer in place.
  4. Chopped vegetable scraps such as lettuce leaves, carrots or potato peelings, apple cores, or grass clippings.
  5. Bulking agent such as wood shavings, 1 – 2 cm pieces of paper egg cartons, cardboard, newspaper, scrap paper or wood. (Do not use glossy paper.)
  6. If your room temperature varies greatly you will need to introduce the concept of insulation. Styrofoam peanuts work will to insulate the containers.
  7. Place a straw in the container next to the thermometer. The straw will provide ventilation for the decomposition chambers. Many decomposition designs are available. This is only a starting point. Students may come up with other ideas in designing and building their soda bottle decomposition chamber. If you have each group of students investigating a different question/problem they should have a minimum of three chambers so they can calculate an average.


  1. DO NOT use dog or cat manure because they can contain harmful pathogens.
  2. A few pathogenic organisms are found in vegetative waste. It is very important students wash their hands after working with compost material.
  3. People with asthma or allergies to molds and/or fungi should take extra precautions while working with compost. These individuals should never turn a compost pile since the molds would be released into the air. A dust mask should be used by whoever turns the compost pile.
  4. Use plastic gloves if desired.




The class should decide on the amount and type of garbage to be used in the investigation. Select a location where the chambers will be located during the testing. Decide on the length of the investigation and make a plan for cleaning the chambers at the conclusion of the test. Wash the chambers with a 10% Clorox solution to remove any unwanted organisms. Many compost investigations may take up to six or eight weeks before enough data is collected to make a conclusion. I advise letting others in your building know your students are working on a composting project just in case they report an odor. Soak the bulking agents in water and do not pack down the mix of garbage in the chambers. Examples of possible research groupings would be one group could use carrot scraps, another potato peelings and another group orange peels.

  1. Build the decomposition chambers and place a sketch in the journal.
  2. Select the materials to go into the chambers.
  3. Insulate the chambers if the room is cold during a 24-hour period of time.
  4. Chop the compost material into small pieces (1 – 2 cm works well). A later investigative question could be does the size of the compost material make a difference in the rate of decomposition.
  5. Soak the bulking agents in water until thoroughly moist, and drain off excess water.
  6. Mix roughly equal amounts of bulking agents and food scraps.
  7. Place the mix into the chamber.
  8. Place the thermometer and straw in the top and seal them into place. The thermometer needs to be down in the middle of the mix and the straw needs to be above the mix.
  9. If you are concerned about flies getting into the compost cover the opening with a piece of nylon or fine meshed fabric.
  10. Have students mark the height of the compost material on the chamber. They should observe the height throughout the investigation. Will the height of the compost change over time?

Odor Issue:

The most common cause of excess odor (ammonia odor) are:

(1) excess moisture
(2) inadequate porosity
(3) a rapidly degrading material
(4) excess pile size.

Observations/Data Collection:

Chart Idea for Investigation:

Material Tested Temperature Date Group

Make a class chart so students may keep the data in their journal for later graphic exercises.
Record the beginning temperature in the science journal in both C and F degrees. A great place to spend some time converting back and forth between two temperature scales. Ask students to write about what they think will happen to the temperature in the different chambers. The students need to explain why they think their prediction is correct.



Have students write about the investigation as it relates to proving or disproving their hypothesis. The explanation based on the data collected needs to be in the journal. Remind students it is okay to disprove a hypothesis as well as prove it. Many times in science we learn more by disproving our hypothesis then proving it correct. A journal response on this idea of proving or disproving would be an excellent reflection for students to explore.

New questions will surface following an investigation. Give your students time to journal about the questions before you make a class list of questions. Record the questions on the KWL and then perform a class KWL.

Revisit the KWL to see what the student and class can have to add to what we know and have learned through the investigation. Keep the class KWL for recording more information at the end of the compost unit.

My compost chamber had an increase in temperature over time yet never got hot. Graph the results and explain them in the journal. The students have experienced the initial study on compost and are ready to answer even more questions on the topic. Students now need to research composting and record the information in their journal. Share the information with the class and record new information.


Additional Investigations

  • Does surface area of the compost result in different rates of decomposition?
  • Does adding corrugated cardboard between layers of compost increase the rate of decomposition?
  • Does adding grass clippings between layers impact the rate of decomposition?
  • Does turning the pile increase rate of decomposition?
  • Does composting allow the soil to hold more water?
  • Will the compost help a plant to grow?
  • How can we reduce the odor produced by organic decay?
  • During composting will the pH level vary?
  • Does the amount of moisture affect the composting process?
  • How do earthworms affect the composting process?
  • Does a sterile soil allow decomposition to occur?
  • How does the compost product work as a chemical fertilizer?
  • Why is it important to recycle organic material?
  • Does turning or stirring the compost impact the temperature of the compost pile?
  • How does the pH of initial ingredients affect the pH of the final compost?
  • Will a chemical change occur in the soil when compost is added to it?
  • Will compost tea, the liquid collected at the base of the compost chamber, be beneficial to plants?
  • How does the size of the compost chamber impact the internal temperature of the compost material?
  • Will the compost weight and volume change over time?
  • What is filling up the landfills?
  • Will all material decay?


Assessment Activities

Click on the following to view assessment suggestions:

  1. KWL Charts.
  2. Journal Assessment Rubric.
  3. Rubric for Scientific Research.
  4. Assessment Checklist for the Scientific Research.
  5. Venn Diagram.
  6. Rubric for the Research Paper.
  7. Rubric for Group Work.


General Notes

I recommend soda bottle reactor chambers for student work. There are some plans for trash can reactors if you want a larger testing chamber. You may want to build a compost pile outside if you want to make a bigger project out of composting.

The most common things to vary in a compost study are: size of the particles, materials for decomposition, temperature, turning the materials, layering, and location (light vs. dark).


Sometimes compost may produce an odor. The anaerobic odors from a compost chamber or pile usually are a sign that something is not being controlled successfully. The most common conditions, which result in odor formation are: excess moisture, inadequate porosity, a rapidly decaying substance and excess pile size.

Since moisture is usually the major problem resulting in slow decomposition, odor production in an aerobic pockets and nutrient leaching, one needs to control moisture content. You can use a “squeeze test” (not 100% precise) to gauge moisture content. Using the squeeze test, the compost mixture should feel damp to the touch, with about as much moisture as a wrung-out sponge.

Materials high in moisture are recommended mixed with dry materials. Peaches are about 80% moist on a wet basis, lettuce about 87%, dry dog food about 10% and newspaper at 5%. Do not use any eggs, meat or dairy products because they get too sticky.


Oxygen is essential for the metabolism and respiration of aerobic microorganisms, and for oxidating the various organic molecules present in waste material. Mixing and turning maybe the easiest way to increase aeration by loosening up and increasing the porosity of the compost mixture.

Compost Pile Size:

A compost pile must be of sufficient size to prevent rapid dissipation of moisture and heat, yet small enough to allow good airflow. This is why in your classroom you may need to insulate your smaller chambers to have good heat retention. It is suggested for a compost pile or container to have enough heat retention that it is at least four cubic feet in volume.

Compost pH:

One can use pH measurements to monitor the process of decomposition. Compost microorganisms operate best under neutral to acidic conditions with the phs in the range of 5.5 to 8. In the first stage of decomposition organic acids are formed increases the growth of fungi and the breakdown of organic material. (Especially cellulose)

As the process continues the organic acids are neutralized and mature compost generally has a pH between 6 and 8.


Nitrogen is another ingredient needed for composting. It usually is provided from the atmosphere which is usually 78%, or from other organic materials like grass clippings. Nitrogen is an essential element, which helps bacteria to break down organic matter faster.

Surface Area:

Making materials smaller by shredding increases the amount of surface area, which can be colonized by the microorganisms. This increases the rate of decomposition.

Benefits of Composting:

1. Supplies part of the essential elements needed by the plants.

2. Reduces the use or need for some chemical fertilizers.
3. Aids in preventing soil erosion by keeping the soil covered.
4. Helps in controlling the growth of weeds in the garden.
5. Recycles usable materials from waste.


Unit Application

Relate the knowledge from the compost unit to farming practices during the 1930s. How does composting impact the ecosystem?

Perform the KWL to bring the unit to a close and point out applications for the use of composting today.

Have the students make a list of all the ways they can reduce, reuse, and recycle today vs. the 1930s.


  • Take along a bag when you go shopping.
  • Instead of paper towels use a sponge.
  • Don’t buy aerosol cans, shop for spray bottles.
  • Cut down on junk mail – request to have your name removed from mailing lists.
  • Use both sides of a piece of paper.


  • Donate used toys or clothing rather than throwing them away.
  • Create a compost pile.
  • Share a subscription to a magazine with a friend.


  • Collect empty aluminum cans and take them to a recycle center.
  • Buy products made from recycled materials. (Like paper)
  • Invest in a battery charger and use rechargeable batteries.

Worm Bins:

Worm bins are a popular form of composting. Students can feed lunch scraps to a worm bin and use the worms for additional studies. Earthworm droppings or castings help fertilize the soil. The best worms to use in a compost chamber are red worms. Red worms eat a large amount of organic material during their life cycle. Flower Field Enterprises in Kalamazoo, MI sells red worms by the pound. A pound of red worms equals about 200 red worms. (1-616-327-0108)


Do organic wastes in compost break down faster in the presence of red worms or earthworms?Additional Activities:



  • A Rot Race: Use a plastic bag with a zip-lock closing. Add a spoon of dirt to all bags, in some bags add bread; in another newspaper clippings; fruit peels; etc. Place some in the sunlight and some in the dark. Open after one week for observation or observe through the bag. (Less odor this way.) You may want your students to wear plastic gloves. Remember to wash hands following examination of organic material. Journal about the results based up on what you have learned about composting.
  • Study worm anatomy, worm life cycle, worm food chains, or study other worm bin organisms. (Ants, mites, millipedes, centipedes, or sow bugs.)


Worms are hermaphrodites, which means they have both female and male anatomy. In order to mate they still require two worms.

Questions for a worm study:

  1. How much can a worm eat in a day?
  2. Do worms have teeth?
  3. Do worms have eyes?
  4. Do worms respond to light?
  5. Are worms male or female? How do worms reproduce?
  6. Why do worms come up on the sidewalk when it rains?
  7. How do worms breathe?
  8. What do worms eat?
  9. What is the life cycle of worms?
  10. How long do earthworms get?
  11. What so worms do in the soil?
  12. How many species of earthworms are there in the world? Which are found in Nebraska?
  13. Why do earthworms die in a landfill?
  14. Do worms like coffee grounds?
  15. Compare and contrast red worms and earthworms.
  16. What is the yellow liquid, which worms release?
  17. Do earthworms have a heart?

Language Arts:

  1. In the journal write a story about recycling on the farm during the 1930s.
  2. Create a newspaper about composting.
  3. Write to the Department of Sanitation requesting information on recycling.


  1. Use metric measurement conversions, like degrees C to degrees F.
  2. Calculate area and volume of the compost chambers.
  3. Average all data and graph results.


  1. Climate and worms around the world. (Red worms are native to the south.)
  2. Farming techniques and crops around the world, 1930s vs. now.

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