Organic and Inorganic Recycling
Composting
What about our food scraps and organic household waste? The next section of this unit deals with just that. In introducing composting as a method of recycling I will explain how compost is natureís way of recycling. Composting is a natural way of replenishing needed nutrients to soil, improving it and creating an environment which plants thrive in. It is also one of our easiest ways to reduce our household garbage volume. Composting turns organic materials into a rich mixture that improves soil and supplies nutrients to plants. Besides building good soil and controlling erosion, composting helps conserve resources and reduces the need to use chemical fertilizers. In the book, All I Really Need to Know I Learned in Kindergarten, Robert Fulghum states very simply, ìIf you make a mess, clean it up.î3 Learning to compost is the first step we can take in cleaning up our mess and reducing our household waste. It is an appealing method of recycling because it is easy to learn. Types of compost, benefits of composting, how toís, materials and uses of compost are covered in this section. Student activities are designed to simulate this concept.
Composting is one of the easiest ways to reduce vegetative waste and turn it into a usable product. It is the biological reduction of organic wastes to humus.4 In early days when hunting for food was common, man began to compost. Sir Albert Howard, a British government agronomist, studied an organic method of gardening and farming in India from 1905-1934. He devised the Indore method of compost making, in which materials are layered sandwich fashion, then are turned (or are mixed by earthworms) during decomposition. Worms, insects, fungi and bacteria are important decomposers.4 Today farmers realize that these organic methods restore life to the soil and reduce their use of chemical fertilizers. Plants, animals, insects and people are all linked together in a web of interrelationships with natural resources. Nature is a continuous composting program. Leaves which fall from the trees are composted and become available nutrients to the trees. Birds, animals and insects also contribute their wastes to help grow food. If we look around us at the earthís greenness we are able to see the vast possibilities of natureís composting program. In summary, compost builds good soil texture and structure, helps control erosion, recycles biological wastes, provides and releases plant nutrients, protects against drought, controls pH, supports essential bacteria, feeds helpful earthworms, stops nutrient loss through leaching, acts as a buffer against toxins in the soil, controls weeds, stretches the growing season and conserves our nationís nonrenewable energy resources.4
Decomposition is accomplished by the enzymatic digestion of plant and animal material by soil microorganisms. Processes of oxidation, reduction and hydrolysis are going on simultaneously. Their end products are used by the microorganisms for further breakdown.4 Bacteria use the products to provide energy for their life processes. This energy is obtained by oxidizing the products. Raw materials have to be of biological origin for decomposition to occur. Then they are broken down to simple forms of proteins and carbohydrates. Carbohydrates break down into simple sugars, organic acids and carbon dioxide. Proteins break down into peptides and amino acids. Through this biological process, the decomposition eventually forms humus. Humus is the finely divided organic matter in soil, derived from microbial decomposition of plant and animal materials. Humus is valued by farmers and gardeners because it provides nutrients essential for plant growth, increases soil water absorption, and improves soil workability.5
Because recycling garden and food wastes is a natural process it is important to practice this for maintaining a good environment. Backyard composting is one step we can take towards conserving our energy supplies and regaining control of our food supplies. To begin a compost pile, first you need to choose an area. Once youíve chosen the proper area, you can spread the bottom with twigs, corn stalks or wood ships. Next you need a layer of finer materials such as grass clippings or small pieces of kitchen waste. Then a layer of dirt is placed over the garbage and moistened. This ìlayeringî is repeated into the compost pile until the pile is about five feet high. A plastic sheet with small holes in it is sometimes placed on top. The compost pile has to be able to support the activity of the compost organisms. Moisture, temperature, pH and oxygen availability all influence the process. Composting can be done with or without oxygen. Decomposition in nature is mostly aerobic, i.e. done with oxygen. If the compost heap begins to smell there is not enough oxygen. Aerobic composting promotes high temperatures. The decomposition process is slower when the temperature is high, however high temperature is important to destroy weed seeds, insect eggs and harmful organisms. The compost pile also needs to be moist so organisms can thrive. If it is too moist, anaerobic conditions can develop and an unpleasant odor can occur. The pH should be between 6 and 7.5 and can be tested with litmus paper. Acid conditions can be controlled by adding some absorbent materials to the heap.5
Once a compost pile has been activated, it is easy to provide a balance of nutrients for it. Kitchen wastes are one of the best sources of nutrients. Some of them to consider are banana skins, citrus rinds, coffee grounds, corn cobs, eggshells, nutshells and tea leaves. These materials decompose more rapidly when chopped or shredded. Other sources of nutrients include: hair and feathers, cut into short pieces (they are high in nitrogen content); leaves which are made up of fibrous organic matter gives good soil building quality; grass clippings, weeds, manure, straw, sawdust, wood ash, limestone, phosphate, rock, cottonseed meal and seaweed are all great nutrients.
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Worm Composting
Another method of natural composting is through the use of earthworms. The process of using worms to convert organic waste into black, earthy-smelling, nutrient-rich humus is called vermicomposting. Vermicomposting is a simple process which can be achieved inside oneís home by setting up a ìworm bin.î It is a convenient method used to convert organic wastes into usable end products. Vermicompost contains worm castings as well as partially decomposed bedding and organic waste. Casting is the material deposited after it has moved through the digestive tract of a worm.6 Worms need proper temperature, moisture and ventilation conditions to thrive. The first step in setting up a worm bin is to set up a proper container. The container needs to be shallow and of a proper size. Wooden boxes tend to work best and last longest. Once you have a container it is necessary to set up proper bedding for the worms. Beddings which are most desirable are light and fluffy. These conditions are essential for air exchange which helps control odors. Shredded corrugated cardboard makes one of the best beddings for worms. Shredded newspapers or computer paper are also good choices as are animal manure, leaf mold or peat moss. Soil is recommended for the initial bedding because it provides some grit to aid in breaking down food particles within the wormís gizzard.6
Redworms are the best worms to use in worm bins. They process large amounts of organic material in their natural habitats of manure, compost piles or decaying leaves. They reproduce quickly and in confinement. The scientific name for redworms is Eisenia foetida.6 Nightcrawlers are another type of worm that usually do well in gardens but arenít as productive in worm boxes.
A redworm has both sexes which allows each worm to produce both eggs and sperm. There is a swollen region between the head and tail of a worm called the clitellum. The clitellum is an indication that the worm is sexually mature. The worms extend themselves from their burrows to seek other worms to mate with. Through glandular secretions, they find each other and lie with their heads in opposite directions, and their bodies closely joined. Their clitella secrete large quantities of mucus that forms a tube around each worm. Sperm from each move down a groove into receiving pouches of the other worm. The sperm, in a seminal fluid, enters the opening of sperm storage sacs where they are held for some time. After the worms separate, the clitellum secretes another substance containing albumin. This material hardens on the outside to form a cocoon. Here the eggs are fertilized and the baby worms hatch. When the adult worm backs out of the hardened band it deposits eggs from its own body and the stored sperm from its mate. The sperm fertilize the eggs and set up a home for developing worms known as cocoons.6
Cocoons are lemon shaped objects about the size of a grain of rice. As baby worms develop, they change color from pearly white to yellow to brown. When ready to hatch the cocoons are a reddish color. The baby worms develop in the cocoons for about three weeks before they are ready to hatch. Each cocoon can contain up to about twenty fertilized eggs but only two to three worms actually emerge from each egg. For a redworm to become sexually mature, proper temperature, moisture and food availability is necessary. Once they are sexually active redworms can breed and lay about two or three cocoons per week for up to a year. Worm survival depends on the availability of food and space in the bin.
Vermicomposting is easy and requires very little upkeep. After the proper environment is provided, burial of garbage is done maybe once or twice a week. Because bedding and garbage is converted to earthworm casting and bedding should be kept fresh. This means changing it and adding to it about every two to three months.
The number of worms needed in the bind depends on the amount of food waste buried daily and the size of the bin. The worm: garbage ratio should be 2:1óone pound of worms to 1/2 pound of garbage. Good food choices for the worms include potato peels, citrus rinds, outer leaves of lettuce or cabbage, celery ends, plate scrapings from carbohydrates, coffee grounds, tea bags, eggshells, and meat waste. You should not use non-biodegradable materials in the binóplastic bags, bottle caps, rubber bands, aluminum foil and glass would cause problems in the bin. The garbage should be added about twice a week and then covered with bedding. The garbage creates a perfect natural environment for other organisms to feed and reproduce. Worms keep the conditions aerobic and odor free. They reduce the mass of material to be processed and produce castings.6
Once decomposition begins to occur in the worm bin you will begin to see some other creatures present. They play important roles in breaking down organic materials to simpler forms that can be reassembled into other kinds of living things.6 The food web in a compost pile is varied. (Figure 1).7 Organic residue is eaten by first level consumers, such as molds and bacteria. Earthworms, beetle mites, sowbugs, enchytralids and flies are also responsible for consuming waste directly. The first level consumers are eaten by second level consumers, such as springtails, mold mites, feather-winged beetles, protozoa and rotifers. Third level consumers are flesh eaters or predators. These include centipedes, rove beetles, ants and predatory mites.6
Many of the organisms are microscopic. Enchytracids are usually known as white worms. They are not harmful in the worm bin. Springtails are primitive insects that jump all over the place. They live in almost all types of soil. Isopods or sowbugs look like tiny armadillos. They are vegetation and eat leaf litter so they present no harm to the worms. Centipedes are predators and do kill worms so if they are present get rid of them. Mites are very small with eight legs and a round body. They are not desirable organisms to have in your bin. Although there are a few organisms which can pose a threat to the worm bin, most of the organisms serve as food for each other, clean up each otherís debris, convert materials to forms that others can utilize and control each otherís population.6
When a worm bin is set up in a classroom, students will have the opportunity to participate in various activities. Besides helping to prepare the bin and care for the worms, students will be able to observe and study many aspects of a wormís behavior and biology. Food preferences, mating habits, identifying castings, charting the distribution of cocoons and the rate of growth development are all areas to be studied. These studies also integrate important math skills such as graphing and estimation as students keep records and journals of their observations and findings.
Once the worms have done their job effectively you can begin to use the vermicompost on your house plants and in your garden and almost immediately you will begin to notice healthier plants. Vermicompost is a mixture of worm castings, organic materials and bedding in various stages of decomposition, plus the living earthworms, cocoons and other organisms present and composting continues after a worm casting has been deposited.6 Humus is an important component achieved in the mixture formed during the breakdown of organic matter. It contains humic acid which is released as plants require it. Humus has been known to stimulate growth and organic gardening encourages carrying out procedures that increase humus content in soil. The vermicompost developed in the worm bin also holds in moisture in soil so its uses are diverse. It can be used in seed beds, in transplanting garden vegetables and as a topódressing for plant growth in both outdoor gardens and potted plants.
Contact Information
Yale National Initiative
P.O. Box 203563 Yale Station
New Haven, Connecticut 06520-3563
Phone: (203) 432-1080
Facsimile: (203) 432-1084
Electronic Mail: teachers@yale.edu
© 2008 by the Yale-New Haven Teachers Institute
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