Compost: the mixture of decomposed remnants of organic matter (those with plants and animal origins) used to improve soil structure and provide nutrients.
Basically, a compost pile consists of plants, lawn clippings, kitchen scraps and the like. Formed into a pile and turned occasionally, nature takes its course and the materials break down. We add compost to our garden soil because it provides nutrition for vigorous plant growth, improves soil structure by creating aeration, increases the ability of soil to retain water, moderates soil pH, and encourages microorganisms whose activities contribute to the overall health of plants.
How do you create compost? Air + Water + Carbon + Nitrogen = Compost
Like most living things, the bacteria that decompose organic matter, and the other creatures that make up the compost ecosystem, need air. We occasionally turn our compost pile to ensure good air flow throughout. These microbes also need the right amount of water; think “wrung out” sponge. If too wet or too dry, optimum conditions for bacteria activity will not be met and decomposition will be slowed or halted.
Carbon is used for energy by the microbes and comes in the form of leaves, straw, hay, sawdust, etc. These are the “browns” of composting. Microbes also need nitrogen for the proteins that makeup their tiny bodies. Matter high in nitrogen are the “greens” of composting (though not always the color green) and consist of “fresh” plants, grass clippings, kitchen scraps, and the byproduct of animals such as manure and worm castings.
What not to compost? Diseased plants, weeds gone to seed, coal ashes, dog/cat manure, lawn clippings that may contain herbicides.
Once you’ve established a location for your compost pile, it’s important to know how much carbon versus how much nitrogen to include. Too much nitrogen and your pile will smell, because excess nitrogen converts to ammonia gas. Too much carbon and the pile breaks down to slow, because microbes need nitrogen to increase their population. The ideal is a 30:1 C/N ratio.
There are two types of composting: hot and cold. Hot composting is accomplished more quickly and best done within a bin. Made up all at one time, it’s allowed to compost without further addition of material, although it does require frequent turning and proper moisture control. Bacteria give off heat as they digest the material. The enclosed pile will insulate the heat raising the internal temperature to 120 – 190 degrees. This attracts more bacteria whose breakdown continues more rapidly. Hot compost is good because it kills pathogens and many weed seeds.
A cold pile (70 – 90 degrees) takes longer though it manages a steady stream of material additions; perfect for the family backyard pile! Simply begin your pile with the organic material of your choice, ie. leaves, kitchen scraps, etc. and continually add to the top of the pile. Within 6 – 24 months (depending on climate conditions) the material will break down–though turning the pile will speed up this process. The bottom of the pile composts first (higher heat due to insulation) and when ready, your material will be unrecognizable from its original form.