What is "Compost" and "Composting"?

Note added 2010:
Check out the What is Composting article I wrote for CompostMania's LEARN section.


The wonderful smell of a forest floor is the smell of humus, or completely rotted plants and animals. Decomposed organic matter is compost. The original organic matter is no longer discernable and you have rich, black, sweet-smelling, crumbly, soil-like substance.

Composting your organic wastes not only keeps them out of the landfills, but when applied back into your lawn or garden, it also increases the health of your soil. Nutrients were stored in the decaying organic matter. Compost holds these nutrients in a form that is easily absorbed by plant roots.

Use of Natural Process

Home composters use nature's process to reduce yard trimmings and organic matter to compost. After a plant or animal dies, bacteria go to work to decompose the remains. Bacteria initiate decomposition of plants. Various types of bacteria thrive in environments with specific conditions. In order to speed the composting process, we manipulate the environment in the compost pile to attract bacteria which will reduce the pile with greatest speed.

The environmental factors we will manipulate are:

  • Air
  • Moisture
  • Carbon and Nitrogen Materials (Food for Microorganisms)
  • Mass
  • Time (Well, we won't "manipulate" time so much as just realize it is necessary)

Environment as Home to Bacteria

All living organisms require air, moisture, and a mix of carbon and nitrogen food. In the compost pile, we strive to have levels of moisture, air, carbon and nitrogen that will attract three types of bacteria: first, psychrophilic; second, mesophyllic; and third, thermophilic.

The psychrophylic bacteria join the pile when the temperature of the pile is between 0 degrees F to 55 degrees F. This is the pile temperature when you first build it. The psychrophylic bacteria begin to decompose the pile by breaking down the particles. If there is enough air, moisture, and food in a pile in this temperature range, the phychrophilic bacteria will be very happy. When bacteria are happy, they eat and reproduce. Reproduction occurs by literally splitting themselves in half down the middle and becoming two bacteria. Bacteria reproduce at amazing speed. One gram of Escherichia coli in favorable conditions takes only three hours to become a pound. This amazing rate of reproduction, in addition to the eating frenzy which occurs, builds heat. If the compost pile is a minimum of 3 x 3 x 3 feet, the center of the pile will retain the heat that is generated. If the pile is smaller, the heat will escape into the air and the pile remains cool. Mass is one of the variables we control by building piles of at least 1 cubic yard.

As the heat in the center builds to between 50 and 100 degrees F, the mesophyllic bacteria are attracted to the pile. If the pile is between 70 and 90 degrees F, the mesophyllic bacteria will eat and reproduce at their peak rate. The result is heat, and the center of the compost pile is raised further.

If the heat of the pile reaches 104 to 170 degrees F, the thermophilic bacteria will begin their work on the pile. To get compost quickly, you must attract this type of fast-working bacteria. As the food and water source begin to dwindle in the hot center of the pile, the thermophilic bacteria slow down their activity. When your pile starts to cool off, you must turn it (i.e., stir up the contents) so that the middle of the pile has the moisture, air, and food to rekindle activity of the thermophilic bacteria and keep the pile hot. Every time the pile starts to cool off, turn again. (This is for the fastest compost, of course. If you can wait, don't turn the pile and let the mesophyllic work on your pile.)

Eventually, the pile will not be able to retain enough heat to remain over 100 degrees F. The mesophyllics will take over at the center (they have been operating outside the center all along), and other microorganisms, fungi, protozoans and other invertebrates will turn out to assist. As the process continues, they will be joined by other macroorganisms, including centipedes, millipedes, beetles, and earthworms.

Given enough time, all organic matter will decompose. In a forest, you will find layers which have been deposited on the ground over a period of years, in various stages of decomposition. Tips, instructions, and information on this site are intended to speed up this process so that you can more quickly create nutrient-rich compost for your garden.

Online Stores
Compost Tea Brewer
Build a brewer with a bucket and less than $15 worth of components, and make aerated compost tea.
Composting the Holidays
Compost fall leaves, hay bales, holly wreaths, pine trees, etc. Compost pumpkins (food waste) in a compost pile.



  1. ** What is Compost?**
  2. Why Not Throw It Away?
  3. Benefits of Healthy Soil

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