The Nutrient Cycle! (10 minutes - Review)
Begin your lesson with a brief discussion of the nutrient cycle.
In ecology the nutrient cycle is a pathway by which a chemical element or molecule moves through compartments of earth. In effect, the element is recycled. In the nitrogen (N) cycle, organic nitrogen exists in materials formed from animal, human, and plant activities that produce manures, sewage waste, compost, and decomposing roots or leaves. These organic products transform into organic soil material called humus. Nitrogen is a primary element in soil and is an essential nutrient for plant growth.
Millions of microorganisms live in most soils, most too small to see with the naked eye. They eat organic matter such as grass clippings, fallen plant leaves, and algae. In doing so, they reduce dead organic matter on Earth's surface and release nutrients from the decomposing organic matter for living plants to use. One of the most common organisms found in the soil are worms. Worms are a part of the phylum Annelida. Earthworms in particular are classified into three main categories: (1) leaf litter/compost dwelling worms (epigeic), (2) topsoil or subsoil dwelling worms (endogeics); and (3) worms that construct permanent deep burrows through which they visit the surface to obtain plant material for food, such as leaves (anecic).
Explain that today's topic is leaf litter or compost dwelling worms. You can setup a simple observation/experiment by bringing in fresh leaf litter (leaves and brush) and some soil for students to observe. Divide students into teams and setup trays with leaf litter and soil. Provide spoons and hand lens for students to observe worms in their natural habitat. Encourage respect for the worms, many students may try to harm or kill the worms.
Environmental Impacts and Solutions: From Leachate to Compost (10 minutes - Investigate)
After engaging in a worm observation activity, talk about organic wastes. What is organic waste? Things like food scraps, leaves and other wastes that were once alive. Where do these wastes go? Commonly, they get thrown in the garbage and end up in landfills. In many communities organic wastes are 10-20 percent of the volume of a landfill. When these wastes are thrown into a landfill the organic matter breaks down. When combined with water and other chemicals that can collect in the landfill, a harmful substance is formed called leachate. Leachate is the liquid that drains or 'leaches' from a landfill; it varies widely in composition regarding the age of the landfill and the type of waste that it contains. Leachate can produce methane and other gases that affect air quality and make the landfill dangerous because the gases are explosive.
So this system of throwing away organic matter presents many problems - wasted space in landfills, toxic leachate and worst of all, we are wasting a resource that could be used to help fertilize gardens or food crops!
What’s the solution? Composting! Composting is the process of breaking down organic matter into a useable fertilizer that can be used as a nutrient source for plants. The problem with setting up a composting system in many homes and schools in setting is challenge of DESIGN! Facilities like classrooms, kitchens and other spaces are not designed to compost organic wastes and because of this it is usually not attempted or becomes difficult to integrate into existing designs.
Simple wooden bins such as the one pictured above are commonly used for composting.
In this activity, we are going to use a popular form of composting. Vermicomposting - or using red worms to help speed up the composting process and break down organic wastes faster. Vermicomposting is a great way to compost indoors, saving space and reducing odors.
Your challenge in this activity is to design a composting system for your classroom that addresses common design challenges that impact the use of composting in your school.
Local Connections (10 minutes - Frame/ReFrame)
To begin addressing this design challenge with students, start by investigating your school building and classroom. What kinds of problems do you see with how the space in your classroom is designed? Is it setup for compost? What about the cafeteria? Have students investigate this problem in relationship to their school. Ask each student or teams of students to conduct research that can help fill out the following table:
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Area of the School
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Challenge
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Observation
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Potential Solution
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Cafeteria
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Lots of food wastes thrown away
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Classrooms
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Hallways
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Library
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Gym
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Teachers Lounge
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Bathrooms
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Other Areas
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Also discuss with students some examples of materials designed for easy breakdown through the composting process referenced in the 2010 National Design Triennial:
• AgroResin: AgroResin is a sustainable packaging material that can be made from any type of plant fiber including rice and wheat straw, corn stalk, and residue from cotton and sugarcane harvesting—that would otherwise be incinerated or dumped in a landfill. AgroResin can be recycled like paper or composted.
• Bioware Packaging: Bioware, a biodegradable packaging material and dinnerware made from bagasse, or the fibrous remains after sugarcane is crushed. This environmentally friendly material is engineered to biodegrade in forty-five days.
• Kraftplex: Kraftplex is a 100% biodegradable alternative to plastic and metal sheeting.
• PLMS6040 Compostable Polymer: Kareline’s PLMS is a natural, fiber-reinforced PLA (polylactic acid) that is biodegradable and has applications for consumer electronics, packaging, toys, and other goods
• Wasara Tableware: The Wasara collection is made from a mix of reed pulp, bamboo, and bagasse, or sugarcane pulp. Bagasse is a waste product of the sugar-processing industry, while reed and bamboo are fast-growing, non-timber plants.
Compost Design Lab: Part One (20 minutes - Generate)
After investigating the situation locally, it’s time for a design-challenge. Divide your students into design teams of 4-5 students each.
Each team will be challenged to design their own composting system for a classroom in the school. Teams will be given the following criteria and asked to design a vermicompost unit:
1. The unit must remain at or around 65 degrees Fahrenheit
2. The composter has to remain dark with a minimal amount of sunlight reaching the confines of the unit
3. The unit should have proper ventilation (using screens is a good idea)
4. It should be easily accessible and identifiable for students/teachers to use (ie. Lid should come off easily, signs of what you can put in the composter and what you can’t should be available as well)
5. Has to be able to be emptied easily
6. Has a chamber for liquid drainage/collection
Ask students to first brainstorm and then to sketch out some designs. Ask them to consider this a habitat for worms - ie. what would make a good home for them? Ask each student to also write a story from the Worm’s perspective about his or her new home.
What is compostable?
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banana skins
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leather
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feathers
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grains
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flour
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rice
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stale bread
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grass clippings
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newsprint (soy based ink)
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manures
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egg shells
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oatmeal
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wood chips
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old seed packets
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flour
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seaweed
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fish scraps (buried)
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straw and hay
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powdered milk
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tobacco
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pine needles
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stale cereal
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hair (human, animal)
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wood shavings
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natural fibers (cotton, linen, wool)
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rock powder (greensand, granite dust)
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coffee grounds (with paper filter)
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dead insects
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tea bags
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crop waste
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cornmeal
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paper/cardboard
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flowers
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bone meal
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seashells (crushed)
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peanut shells
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cottonseed meal
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kitchen scraps
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yard waste
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watermelon rind
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vacuum bag wastes
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potato peels
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leaves
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sawdust (not treated)
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shredded hardwood
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corncobs
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ground bones
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bird cage "stuff"
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old potting soil/mix
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weeds (most, but not all)
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fruits & vegetables
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DO NOT COMPOST: Meat and dairy products, oils, bones, treated wood, colored newsprint that is not soy-based
Compost Design Lab: Part Two (20 minutes - Edit and Develop)
If materials and time allow - each design team should construct a working model of their composting unit. Provide students with opaque storage bins, mesh for ventilation, newspaper and brown paper scraps, leaf litter and other materials needed for each design.
Finally, after testing out the units, share your final designs with other classes. Setup designated worm habitat areas in classrooms around the school. Mobilize with sanitation staff to create a working composting system for the school. Maintenance and upkeep are the most essential elements of any composting system. (Share and Evaluate)