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Michigan State University Extension
Home Maintenance And Repair - 01500589
06/24/03

Composting



Composting of yard wastes such as leaves, grass clippings, dead garden plants and hedge trimmings, along with kitchen scraps, is popular with home gardeners who long ago discovered the benefits of the dark, rich, sweet-smelling, earthy end product called humus.

Benefits of composting

In about as much time as it takes to burn or bag yard debris for disposal, you can prepare these same materials for composting and use them as a soil conditioner. Home composters can use humus to lighten heavy, clay soils or enrich sandy soils to improve water-holding capacity. Plants grow well in well-drained soils that hold some moisture and the result should be a healthy, vigorous garden.

Understanding and assisting the compost process

Heaping organic materials into a pile generates heat through the activity of the microorganisms. This heat encourages activity of other microorganisms which speeds up the composting process. High temperatures also help destroy weed seeds and disease organisms.

Before piling, shred or chop yard debris to give organisms a larger surface area to decompose.

Because nitrogen is consumed by tiny decomposers, the addition of nitrogen fertilizer or manure assists in rapid and thorough decomposition. A proper ratio of carbon to nitrogen is also important to the composting process. While table scraps have a 15:1 carbon to nitrogen ratio, fallen leaves are more in the range of 60:1. Grass clippings have a 20:1 carbon to nitrogen ratio. A C:N  ratio of 30:1 is ideal for microbial activity, although a 50:1 ratio is adequate for a slower compost. A complete mixing of a variety of materials will provide the desired ratio.

Frequent turning of the compost pile also speeds up the decay process by providing a supply of oxygen.

Building your compost pile

Backyard composting is appropriate for all lifestyles, because it can be done on a small, medium or large scale, using a low, medium or high effort.

Soil incorporation is perhaps the easiest way to compost in the backyard, when space is limited and yard wastes are minimal. Kitchen scraps, minus meat, bones and fatty foods, can be incorporated directly into the garden.Bury scraps at least six to eight inches beneath the surface.

Mulching is another simple way of utilizing organic materials. Simply spread leaves, grass clippings or shredded woody wastes beneath ornamental plantings for initial use as mulch, and later, as they decompose, as a soil enrichment. Chippers or shredders can be rented or purchased and used to chip materials for these purposes or for informal garden paths.

Turning and holding units can be built to help contain backyard compost piles. For yard wastes, a three-foot square holding bin made of wire provides the simplest method of composting. Place the bin in a shady place and gradually deposit weeds, grass clippings, leaves and harvest remains as they are collected. Remember to layer plant materials and if desired, add a handful of nitrogen fertilizer between each four-inch layer to achieve the proper carbon:nitrogen ratio. Layering with topsoil adds additional decomposers to the heap.

Moisture and aeration are essential. Keep the pile damp but not soaking. This produces a usable compost in six months to two years, depending on the mixture of materials. Occasional turning, shredding of materials and addition of high-nitrogen materials or fertilizer will speed the process.

Gardeners with large volumes of yard wastes may want to build a series of two or three turning units or bins. (Vis. 2) The compost can be turned and moved to an adjacent bin on a regular schedule. Bins can be built of wood, a combination of wood and wire, or concrete blocks. Begin the compost pile by alternating layers of organic materials. Monitor the moisture of the pile and check the pile temperature regularly. The pile will heat up to between 130 and 160 degrees in the middle, and the outside will be warm to the touch. During this period of intense activity, be sure the pile does not become dry.  When the pile begins to cool, turn the pile into an adjacent bin with a shovel or manure fork. This mixes uncomposted material from the outer edges of the pile and the temperature should start rising again. After a few days, turn the pile into the finishing bin and start new layers of compost in the first bin. Through persistence and a little extra effort, you can have finished compost in a few weeks instead of a few months.

Remember, you can build simple wire bins, use wooden pallets, or build more complex turning units. Depending on your time commitment and quantity of materials, you can select the compost method that works best for you.
Example of compost holding bins(Vis. 1)
Household garbage can be easily composted by building a worm box in your basement or backyard. Prepare a 3' by 2' by 1' wooden box with a hinged cover (this size will accommodate the kitchen wastes from a family of four to five). 

round compost bins(Vis. 2) Use shredded cardboard, newspaper strips, animal manure, partially decomposed leaves or peat moss as a bedding material.

Add one to two pounds of red worms (can be purchased or obtained from manure piles). Bedding material helps the worms escape when compost gets too hot. Household garbage such as lettuce and cabbage leaves, carrot tops, potato peels, citrus rinds, coffee grounds, eggshells and moldy left-overs can be fed to the worms. Bury the garbage in the bedding and cover it with more bedding and let the worms go to work. Two pounds of worms can process a pound of garbage a day. Keep the bedding damp but not soaking. In several months you will have to move the vermicompost (worm castings, uneaten garbage, bedding) and worms to one side of the box. Begin placing fresh garbage and bedding on the other side and the worms will leave the finished compost, which can then be used as a potting soil supplement.

Neighborhood Composting

Community garden projects are ideal for apartment dwellers and homeowners with small backyards. Participants can get rid of kitchen wastes harvest remains and yard debris at the garden site. Kitchen wastes can be incorporated directly into the soil and neighbors can join together to develop active compost piles.

Uses of Finished Compost

Compost contains some nutrients, but its greatest benefit is in improving soil characteristics. If you've added fertilizer or manure during the composting process, however, you may find the compost is all you need to achieve good plant growth and production.

To use compost for lawns, screen the material and use a seed-starting material or as a top-dressing.

When working the compost into the soil of flower beds or the vegetable garden, (before or after planting) apply at a depth of two-to-three inches.

Compost can be mixed with topsoil for use with indoor potting plants. Sterilize by baking in a 200-degree oven for one hour.

References

Backyard Composting Made Easy, Wisconsin Department of Natural Resources.

Composting.- A Solid Waste Alternative, Michigan Department of Natural Resources, Community Assistance Division, P.0. Box 30028, Lansing, MI 48909.

Composting.: A Study of the Process and its Principles, Rodale Press, Emmau, PA, 1977, Golueke, Clarence G., author.

Composting Your Garbage with Worms, Kalamazoo Nature Center, Inc.

Guide to Composting, City of San Jose Parks and Recreation Department.

Home Composting, the Community Composting Education Program, Seattle Engineering Department and the Seattle Tilth Association.

Making and Using Compost, fact sheet from the U.S. Department of Agriculture. Office of Communication, Washington, D.C. 20250.

The Rodale Guide to Composting, Rodale Press, Emmaus, PA, l979, Minnich, J. and M. Hunt, authors.

Compost Do's and Don'ts

Don't use unfinished compost. It will rob your plant's nitrogen instead of acting as a fertilizer. You can also spread garden diseases with unfinished compost.

Do mix finished compost with topsoil to prepare garden flower beds or for potting mixtures.

Do mix manure (if available) or high nitrogen fertilize with yard wastes. Sprinklings of fish fertilizer, ammonium sulfate (20 percent nitrogen) or urea (45 percent nitrogen) also work well.

Do not use more than one-fourth pound of fertilizer per 15 square feet of compost. When composting low-nitrogen materials such as sawdust, paper and woody plants, increase fertilizer rates.

Do add lime, small amounts of wood ashes or crushed eggshells to neutralize acids which may form in compost and cause an odor problem.

Do layer materials two to six inches thick, taking care to mix up grass clippings (they tend to compact).

Do add topsoil to layers to provide a good source of microorganisms.

Don't compost weeds that are heavily laden with seeds (some will not be killed during the heating process).

Don't ignore strong odors. Simply turn the pile when odors are detected.

Don't add meat or fish scraps to the compost mixture. They may attract animals (dogs, cats, rats, etc.) and they do not decompose easily.

Don't add diseased vegetable plants to the pile if compost will be used on a vegetable garden. The disease organisms may reappear the next year.

References

This information comes from Michigan State University Extension bulletin WM 02, Backyard Composting.

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MSU is an affirmative-action, equal-opportunity employer. Michigan State University Extension programs and materials are open to all without regard to race, color, national origin, gender, gender identity, religion, age, height, weight, disability, political beliefs, sexual orientation, marital status, family status or veteran status. Issued in furtherance of MSU Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Thomas G. Coon, Director, MSU Extension, East Lansing,MI 48824. This information is for educational purposes only. Reference to commercial products or trade names does not imply endorsement by MSU Extension or bias against those not mentioned.

This information.was reviewed as of June 2008.  For more information about the contents please contact costner@msu.edu for webpage problems strausc@msu.edu .