In nature, once living material drops to the ground, decays, and eventually decomposes creating compost. This material is essential because it adds nutrients to the soil helping living plants thrive. It is easy to create your own compost and make your garden thrive as well! The first essential ingredient for creating compost is air. The bacteria and fungus microbes that are in your compost pile need oxygen to live. If your pile is too dense or becomes too wet, the air supply to the inside is cut off and the beneficial organisms will die. Decomposition will slow and an offensive odor may arise. To avoid this, turn and fluff the pile with a pitchfork often, perhaps weekly. You can also turn the pile by just re-piling it into a new pile.
Next is water. One of the most common mistakes in composting is letting the pile get too dry. Your compost pile should be moist as a wrung-out sponge. A moisture content of 40 to 60 percent is preferable. To test for adequate moisture, reach into your compost pile and grab a handful of material and squeeze it; if a few drops of water come out, it's probably got enough moisture, if it doesn't, add water. When you water, it is best to put a hose into the pile so that you aren't just wetting the top. You can also water as you are turning the pile. During dry weather, you may have to add water regularly. During wet weather, you may need to cover your pile. A properly constructed compost pile will drain excess water and not become soggy.
Third essential ingredient is carbon. Microbes need carbon for energy to be able to break down the organic material. Brown yard and garden material such as dry leaves, twigs, hay, or shredded paper can provide the carbon balance for a compost pile. Chop or shred large pieces to 12 inches or shorter (thick, woody branches should be chipped, ground up, or left out).
Lastly, composting needs nitrogen. Nitrogen is the protein required to fuel the bodies of the microbes so they can do their job. Green materials such as grass clipping and landscape trimmings are ideal sources of nitrogen for composting. Vegetable and fruit trimmings and peels can also provide nitrogen for composting. Coffee grounds and tea bags may look brown, but are actually potent nitrogen sources. To reduce the potential for pests or odors, avoid meat or dairy scraps and always bury food scraps deep within the compost pile. Avoid pet feces due to concerns about pathogens. However, manure from chickens, turkeys, cows or horses is rich in nitrogen, and can help your compost pile get to proper temperatures, and make very good compost.
You can compost in a contained bin or, if it's ok with your city, have an outside pile right on the ground. Ideally, the compost pile should be at least three feet wide by three feet deep by three feet tall (one cubic yard). This size provides enough food and insulation for the organisms to live. However, piles can be larger or smaller and work just fine if managed well.
The easiest compost recipe calls for blending roughly one part of green or wet material (which is high in nitrogen) and two parts brown or dry material (which is high in carbon). Having the right ratio of carbon to nitrogen is important. "Piles with too much nitrogen tend to smell, because the excess nitrogen converts into an ammonia gas. Carbon-rich piles break down slowly because there's not enough nitrogen for the microbe population to expand. An ideal compost pile should have a 30:1 C/N ratio. Grass clippings alone have about a 20:1 C/N ratio. Adding one part grass clippings, or other green, to two parts dead leaves, or other brown, will give you the right mix."
(source: http://www.organicgardening.com/learn-and-grow/composting-101)
Simply layer or mix these materials in a pile or enclosure; chop or shred large pieces to 12" or shorter. Water and fluff the compost to add air. Then leave it to the microorganisms, which will break down the material over time.
Compost piles that have the right blend of nitrogen and carbon and are kept moist and fluffed regularly, will heat up to temperatures of 120 to 140 degrees Fahrenheit. The high temperature will kill most weed seeds and speed up the decomposition process so that the compost may be ready in 2 to 3 months or less. Casual compost piles are also quite workable since compost will happen even if you just pile on yard and food waste, water sporadically, and wait. Since these piles don't get too hot, often worms will migrate into these and they will help breakdown material as well. Casual composting can take several months.
Composting is finished when the original material has been transformed into a uniform, dark brown, crumbly product with a pleasant, earthy aroma. There may be a few chunks of woody material left; these can be screened out and put back into a new pile. Besides making incredible, nutrient rich soil for your garden, using left over food scraps in your compost cuts down food waste that would otherwise end up in land fills! Composting is a win-win!
