Air + Water + Carbon + Nitrogen = Compost!
Nature is constantly creating compost without our help, but we can speed up the process of making compost by giving it the optimum conditions it needs to work.
Air. Your compost needs air because the bacteria that decompose organic matter and the other living creatures that are in your compost ecosystem breathe air. The compost needs to be porous so that air is able to move in and out of the pile. Also, turning your compost gives it fresh air and keeps it less compact.
Water. Too little moisture in your compost pile slows decomposition and prevents the pile from heating up. On the other hand, too much water reduces airflow, compacts the pile, and can make it smell. Ideally, your compost should feel like a wrung-out sponge. It is important to check the moisture levels, beginners can use a meter.
Carbon. The microbes that break down your compost use carbon as an energy source. Keep them alive and busy working by feeding them carbon, which is in dry, brown organic materials, like leaves, straw, and corn stalks. Even though the straw & stalks are yellow, they are considered brown for the purposes of the compost pile.
Nitrogen. The microbes also need nitrogen. They derive proteins from nitrogen for growth. Materials high in nitrogen are green, fresh plants parts, like leaves, grass or animal manures. These materials may not be green in color but are referred to as greens for the compost.
Carbon/Nitrogen Ratio. In order for you compost pile to work most efficiently, it will need the correct balance between carbon (C) and nitrogen (N). You can tell if your pile has too much nitrogen if it smells, because the excess nitrogen is converting to ammonia gas. If your pile is not breaking down as fast as it should, it probably has too much carbon, it needs more green materials to feed the microbe population. The ideal compost pile will have a 30:1 C/N ratio. Grass clippings alone have about a 20:1 ratio. Adding one part of grass clippings or any green, to two parts dry leaves, or other brown, will give you the right mix.