What is it?
Composting is the natural process of decomposition and recycling of organic material into a humus-rich soil know as compost. As a natural process it is occurring all of the time whether we assist it or not, but we can speed up the process if we chose. The important variables are:
- available moisture
- how often the pile is aerated (turned to allow oxygen in)
- size of material
- type of organic materials
Why do we do it?
In the United States, roughly 30% of our household waste is organic material, which includes kitchen scraps and yard and leaf waste. Traditionally everything we generated went to the landfill or the incinerator, but with landfills closing and incinerators prohibitively expensive in cost and to the environment, alternative disposal methods have been explored.
Composting is an easy, effective, and cost efficient way to manage organic waste generated in homes, with an added benefit. The soil amendment which results from the composting process is rich in the very nutrients necessary for healthy plant growth. When compost is mixed in with soil, it improves the soil structure, texture, aeration, and increases its water-holding capacity, there by promoting soil fertility and healthy root development in plants.
What's a good compost recipe?
Just like baking bread, a good compost pile has a specific recipe. The idea is to mix organic materials containing nitrogen like most kitchen scraps, with materials containing carbon like dry leaves and woodchips, and make sure there is the right amount of water and oxygen. Give it a little time to heat up properly and the result is a nutrient rich humus. The major ingredients are:
Water: A compost pile requires enough moisture for the tiny biological agents like worms, insects, bacteria, and micro-organisms to survive. A good way to tell if your pile has enough moisture is to squeeze a handful. If you see moisture seep between your fingers, then your pile has enough water. Remember, damp is good...soggy is bad. See troubleshooting tips
Oxygen: Aerating a compost pile is necessary for microbes to efficiently decompose organic wastes. Some decomposition will occur in the absence of oxygen (aerobic conditions); however the process is slow and foul odors may occur. Turning the pile several a month is enough to provide the necessary oxygen. A well mixed pile will also reach higher temperatures which will help destroy weed seeds and pathogens. See troubleshooting tips
Organic Materials... The Browns and the Greens: The ideal compost pile has a thirty to one ratio of Carbon to Nitrogen. The high carbon materials or the Browns are dry leaves, woodchips, straw, and sawdust. The high nitrogen materials, the Greens, are generally anything from your kitchen, green grass, and plant trimmings. The importance of the C:N ratio is that the organisms ‘munching' all of those organic materials require a certain amount of nitrogen for their metabolism and growth.
Material size: The smaller the size of the organic materials the faster the compost will decompose. Cut kitchen scraps into smaller pieces before putting on the pile. For leaves, either mow your lawn before raking it or run your lawnmower through the pile of already raked leaves.
Heat: If you have managed to put a compost pile together successfully (which isn't hard), you will notice that the center of the pile becomes quite warm. In fact the center of a healthy pile can reach temperatures of up to 160+ degrees. The heat is a result of all of the biological activity taking place and is important in destroying pathogens and any weed seeds that might have gotten into your compost. Compost thermometers can be bought that can tell you how hot the pile is. By following the temperature of your pile, you will know when is the best time to turn your pile. Aerate the pile after it has reached peak heat and has begun to cool down. See troubleshooting tips
Organic materials that should be AVOIDED:
- Anything organic will eventually breakdown, but certain things can cause problems.
- Avoid putting bones, meat, and dairy products into your pile, they take longer to break down and attract pests.
- It is recommended that human and animal wastes not be integrated into your pile due the possibility of pathogens.
- Don't put organic materials that have been treated with pesticides or herbicides in your pile, especially if you are using the finished amendment in a vegetable garden. If your grass has been fertilized recently, it is best to leave the grass on the lawn where it has fallen. The cut grass provides nutrients and acts like a mulch which holds in water.
Adding organic material
The easiest way to begin a compost pile is to layer the different materials. Start with a base of dry leaves, add kitchen scraps, wood chips or twigs, more leaves, and so on...Green/Brown, Green/Brown. Each layer should be between 5"-8". Be sure to add some regular soil or recently composted humus. This helps mask any potential odors, but more importantly it transports the necessary micro-organisms into your new pile. Continue to add material as you go along, remembering to cover new material with a layer of soil and to keep the pile moist.
Pile isn't heating up:
1 - There isn't enough moisture for the organisms responsible for decomposition to thrive. Turn pile and check moisture level. If it seems dry, add water.
2 - It is possible that there isn't enough nitrogen in the compost mix. Add nitrogen-rich material like grass, kitchen scraps, or manure.
3 - The mass of the pile might be too small to hold heat in. This is especially a problem if you are composting in cold weather.
Pile is soggy:
When the pile is too wet, the decomposition process slows down. Turn pile and add dry materials like leaves, saw dust, or wood chips.
Compost smells bad:
Don't be alarmed if your compost smells at one time or another. A smelly pile indicates that anaerobic bacteria (living without oxygen) are doing the decomposing rather than the pleasant smelling aerobic bacteria. Turn pile thoroughly to aerate and add nitrogen-rich material like grass or manure.
What kind of container is best for home composting?
It is recommended that urban composting be done in a container that has a lid. The reason for a contained system is to discourage pests, and also to minimize any possible odors. A lid is also important for controlling the amount of moisture entering and leaving the pile. The ideal compost bin design has a base which allows air movement, and sides with small holes for aeration. You can easily build your own or buy one that will suit your needs.