Solid Waste Lesson Plan: Composting: Get “the Dirt” on Humus!
(Developed by the York County Solid Waste Authority © 2001) 

Students will learn about the world’s oldest form of recycling…composting! Composting is a practical method of turning leaves, grass, and other organic materials into a valuable resource. Students will learn about the natural process of decomposition that changes organic matter into a dark, rich and crumbly substance called humus. Humus is an excellent soil conditioner. Students will also understand the environmentally beneficial role composting plays in removing yard waste from our overall waste stream.

Ages:  6 and up
Group Size: Up to 100

Via an interactive demonstration, students will learn how to start and maintain a compost pile. Includes an overview of the materials needed, different bin or storage options, identification of materials that can be put in the bin to be composted, and a discussion of plant nutrient needs.

Overhead projector, screen or blank wall, leaves, nitrogenous fertilizer or commercial compost starter, grass, compost bin or container, water, pitchfork. Materials provided by the Authority.

Science, biology. Discussion, measuring, observation, recording.

30 minutes to 1 hour (adaptable to grade-appropriate length).

Indoors or outdoors.

Using the overheads and provided materials, a speaker will combine a visual presentation with audience participation to communicate key areas of emphasis. Those key areas emphasize recycling, waste reduction, and an illustration of exactly how a waste-to-energy facility operates,

Vocabulary Words:
Microbe, decompose, natural resource, nitrogen, fertilizer, organic, humus.

Gardeners have always appreciated the benefits of using nutrient-rich compost. Adding compost improves the quality of soil and increases water retention. The result is healthier plants requiring less water and fertilizer. If you have a garden, lawn, trees, shrubs or even planter boxes, you have a use for compost. Composting also benefits the environment and the community by removing yard waste from our waste stream.

Composting speeds natural decomposition. Microbes feed on organic materials and churn out humus–a process requiring moisture and oxygen. As microbes work, their activity causes temperatures within a compost pile to rise to 120°F -160°F, accelerating the decomposition process and killing many disease organisms and weed seeds.

A compost pile can be started any time, but some people prefer autumn with its abundance of leaves. The simplest way to compost is to place organic materials together in a pile. A compost bin will provide an easy way to contain your compost pile. You can make your own bin with chicken wire, snow fencing or wood pallets or purchase one commercially. For most people, a four-foot long by four foot wide by three-foot high bin will serve.

Place your compost bin in a convenient location protected from overexposure to wind and direct sunlight. Add grass, leaves and organic materials as they collect. You need microbes to assist in the decay process. They can be added by layering with top soil. Wet each layer well. Try to maintain a 3 to 1 ratio of browns (leaves, dried plants, coffee grounds, etc.) to greens (grass, manure, etc.). Turn the pile at least monthly. Turning provides ventilation and shifts the materials from the outer edges of the pile to the center, where they are heated and broken down. Wet the pile thoroughly, but not to the point of soaking. This method can produce usable compost in about six months. You can turn your compost pile more often to speed the process.

If you want to make compost quickly, add other natural materials to your leaves. Good additions are fresh grass and green plant materials, nitrogen-containing fertilizers and farm manure. You can also compost food waste such as fruit and vegetable scraps, eggshells, coffee grounds, and other non-meat or non-fat products. You can speed up composting by shredding or chopping materials to be composted. Covering the compost pile with a tarp helps retain moisture and heat during winter months. This also protects the pile from becoming too wet when it rains. Turning or mixing is not recommended in cold weather because it allows too much heat to escape.

A properly heated compost pile has no odor. If you detect ammonia or any other offensive odor, turn the pile immediately. Allow enough time for the organic materials to decay. Compost that is not fully decomposed may cause nitrogen starvation when used on plants. Once compost is ready, mix thoroughly into the soil and plant your flowers and vegetables!

Using the overheads and provided materials, a speaker will combine a visual presentation with audience participation to demonstrate how a compost pile is started. Key areas of emphasis include recycling, waste reduction, plant nutrient needs, and a step-by-step demonstration of how to start a compost pile.

Evaluation Tool:
Quiz questions (and answers) will be provided for teacher use. Students will have the knowledge to start their own compost pile at home, be able to describe the environmental benefits of composting, and understand how using compost as a soil amendment improves plant growth.


  1. Start your own compost pile at school and recycle lunch room waste. The Authority can provide a compost bin to get you started!
  2. Grow tomato plants in the classroom. Have half the class plant tomatoes in soil that has not been incorporated with compost. Have the rest of the class plant tomatoes in compost-enhanced soil. Have students observe and chart plant growth. What are the differences? Do the tomatoes produced in the different soil types look or taste different?
  3. Visit the Authority’s Yard Waste Compost Site. Call 717-845-1066 to schedule a visit and observe a 5-acre compost site in action!

How to Get this Lesson Plan Into Your Classroom
This lesson is available at no cost to any York County school or civic group and is presented by a member of the Authority’s Education Center staff. All materials and handouts associated with this lesson plan are provided by the Authority. Call 717-845-1066 to schedule a presentation of this lesson plan for your class or assembly program.