HOW TO: Compost in your Classroom
What is composting?
Compost is the decomposition of organic material into a rich and fertile soil substance known as humus. Organic matter in our everyday lives include banana peels, apple cores, orange peels, egg shells, vegetable stems and scraps, plants, grass clippings, leaves and much more! When left in a state where chemical, mechanical and biological breakdown can occur, what is left is some of the best growing material there is! Gardeners call it “black gold” because of its dark, rich color. Composting is natures way of recycling!
Why should I compost?
Composting as a class science project is a relatively low cost endeavor that is rich in science. All you need is a bin with a lid and organic material which is already in your everyday life! This project can be done in a few weeks or over an entire term, semester or year. The resulting organic material will be a valuable product that can be used in a school garden, donated to a community garden, contributed to nearby areas to help improve soil health or added to individual potted plants and around the base of trees on the school property. The composting possibilities are endless!
How to Make a Compost Bin:
What you need:
- Compost bin
- Source of moisture- either rainwater or water you will be adding
- Carbon rich materials
- Nut shells, bread and grains, egg shells, shredded paper, dead leaves, hay and straw, pine leaves, small twigs and bark chips
- Nitrogen rich materials
- Fruit and vegetable scraps, coffee grounds, fresh leaves and plant stems, grass clippings, clover
Your goal should be to have two parts carbon rich ingredients to every one part nitrogen rich ingredients.
- Pitch fork or shovel to churn the compost
- Earthworms (optional)
What NOT to Add:
Weeds that have seeds, diseased plants, sand, charcoal, colored or glossy paper, animal waste products (feces, meat, bones, and fat renderings), herbicides/pesticides, food scraps that are oily, cheese or dairy products, branches that are too large, non compostable materials (plastic and metal)
- Acquire several bins that can be used to gather compost materials
- Trash cans
- Plastic totes or pallet boxes.
- When selecting your bin, keep in mind that having a bottomless bin will allow easy access for water, oxygen, earthworms and decomposing bugs, but it’s not a necessary component.
- Drill a few small holes in your compost bin if it is air tight
- Gather green/fresh materials, these will add nitrogen.
- Gather brown materials which will add carbon.
- Make sure your compost bin is close to a water source and is inaccessible to rodents and vermin.
- Chop larger materials into smaller pieces less than six inches wide and long.
- Using a pitch fork or shovel, mix leaves, soil, greens and waste.
- Moisten the pile, you want it to be wet, but not soggy.
**Note: If you are using worms in your compost bin, do not add too many citrus products (orange, lemon, lime peels) as it will become toxic to the worms.
What will students learn?
Scientific Investigation and Discovery
- Biology: Worms, bacteria, fungi, amniotes, and hundreds of other microorganisms are essential to the biological aspect of material breakdown. They convert organic materials into a source of energy for plants to utilize through the process of their digestion.
- Temperatures: Compost goes through two phases, a thermophilic phase, over 40 degrees Celsius, then a mesophilic phase, between 10 and 40 degrees Celsius. During the thermophilic phase, bacteria, amniotes and heat-tolerant fungi break down proteins, hemicellulose and cellulose. During the mesophilic stage bacteria, fungi and invertebrates slowly degrade lignin and highly resistant compounds.
- Chemistry– The chemical properties of compost materials change during the breakdown process. Chemical breakdown is triggered by enzymes secreted by fungi, bacterial, and microorganisms in the soil. Enzymes catalyze reactions that result in the sugar, starch and proteins being broken down into carbon dioxide, water and energy.
- Physics: A compost pile must be large enough to retain moisture and heat but not so large that it looses air circulation. It must be moist enough to support microbial growth but too wet that it creates an anaerobic environment. The particle size has to be just right as well, too large of particles will inhibit decomposition but too small of particles will create not enough pore space for effective water filtration.
- Waste Management/ Environmental Care: Through a composting project, students will be able to identify the differences between what can and cannot be composted. This knowledge may encourage them to start their own compost bin at home! According to the EPA, in 2013, Americans threw away 254 million TONS of garbage to be sent to landfills! Composting organic materials overtime can create a difference in the longevity and sustainability of our society’s environmental health.
Potential Projects Using Compost
- Entire class project- learn about waste management and environmental care
- Scientific Inquiry Project- Using a control compost bin and two to four variable bins, students can easily identify the differences in what makes the best compost
- Ideas for variable bins: Add worms, add too much/little water, different Carbon:Nitrogen ratio, turned/mixed more/less often
By feeling like they are making a positive change through proactive waste management in the form of composting, students can begin to conceptualize their role as an individual in society who can help better the world we live in.
For further education on composting with your students, visit our online library resources!
Lessons and Activities:
Books and Resources
- Do the Rot Thing: A Teacher’s Guide to Compost Activities