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Home  > Question of the Week

Question of the Week

Permalink What can you tell me about small-scale composting?



Composting has numerous advantages for waste materials. Compost contains nutrients that are readily available to plants and yet held against loss through leaching or volatilization. Compost added to soils has also been shown to increase biological activity in the soil, improve soil tilth, and increase the availability of certain plant nutrients already in the soil. Furthermore, the composting process can turn materials such as grass clippings, leaves, yard debris, and other materials -- frequently considered nuisance items -- into a valuable resource. Proper composting can even kill most weed seeds and disease organisms that may be present in the organic debris.

Several conditions are important for proper composting to take place.

1) The materials to be composted should have an appropriate carbon:nitrogen ratio, from 20:1 to 30:1. With a higher ratio (more carbon) the composting process takes place more slowly; with a lower ratio there is increased chance of loss of nitrogen to the atmosphere. In practice, this means using a blend of high carbon materials such as leaves, straw, or yard residue, and high nitrogen materials such as livestock manure or fresh grass clippings.

2) Moisture content between 40% and 60% should be maintained. If the material is too dry, the lack of moisture will slow microbiological activity and the compost pile will not heat up properly. A compost pile with too high a moisture content will not stack properly and will have insufficient oxygen for the microbes. In addition, too much water in the pile may cause soluble forms of nitrogen or other nutrients to leach from the compost.

A simple test for measuring moisture content is to take a handful of the composting materials and squeeze the material into a tight ball in your fist. If the materials stay in the tight ball shape when you open your hand, the materials are probably too wet. If the materials fall apart rapidly, the materials are probably too dry. Properly moistened, the compost materials will form a ball when squeezed, but the ball will break apart readily.

Maintaining the proper moisture content may require some care. During periods of high precipitation, covering the pile with plastic or other water-repellent material may be necessary. During dry weather, the compost may require the addition of water.

3) The microbes, which break down the organic materials in the composting process, require oxygen, so proper aeration is critical. If the compost pile has insufficient air anaerobic organisms are favored. The presence of these organisms as well as other chemical conditions favored by low oxygen increase the chance of loss of valuable nitrogen to the atmosphere. Aeration of compost is usually achieved by physically stirring or turning the pile periodically or by incorporating coarse materials into the pile when it is first built.

4) Compost must be able to achieve and maintain sufficient heat to speed biological activity and to help kill weed seeds and plant pathogens. Although the composting process produces heat, often in excess of 150° Fahrenheit, retaining it can be difficult during cold weather. Building the pile large enough, with each of the three dimensions at least four feet, decreases the surface to volume ratio and helps to keep the center of the pile warm. A covering of plastic sheeting or straw will provide some insulation to help retain heat.

Several considerations for anyone developing a composting plan are odor and appearance, kind and quantity of locally available compostable materials, and where the finished compost will be used. If the compost pile is properly formed and aerated, objectionable odors should not occur. If odor is a problem, a thin layer of soil over the pile should help to solve it. The appearance of a compost pile can be improved by building a bin to contain it. This has the additional advantage of keeping dogs and other animals, domestic and wild, from stirring and scattering your hard-built pile.

High carbon materials are frequently more readily available than are high nitrogen materials. In this case, you may have to obtain some manure, bloodmeal, or other high-nitrogen material. Most organic materials can be composted, and the key to efficient composting is making use of what you have at hand.

Moving compost around is hard work, so most people try to build their piles near to where the compost will be used or easily marketed. This makes the move from finished product to application as short as possible, and also allows residues to be easily incorporated into the pile.


American Horticulture Society. No date. Home composting: The slow & easy method, and Fundamental (and little known) compost truths. Compost Factsheet 1 & 2. 2 p.

Anon. No date. Bag composting. HortIdeas.

Anon. 1997. Compost production and use-part 1. Small Acreage Farming. July. p. 4-6.

Portable wood & wire composting bin

Anon. 1988. Build a three-bin composter. National Gardening. April. p. 40-41.

Baker, B. 1990. Science you can use: Compost. California Certified Organic Farmers Statewide Newsletter. Summer. p. 19-21.

Cline, S. 1994. Get started in composting. Fine Gardening. October. p. 52-55.

Cohen, Ellen. 1986. Compost. Rodale’s Organic Gardening Magazine. June. 6 p.

Cox, Jeff. 1995. And I piled it my way! Organic Gardening. April. p. 61--65.

Rosematrin, L. 1991. Compost more than you ever wanted to know. Tropical Fruit News. March. p. 4-5.



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