The microorganisms that are responsible for the decomposition process need both nitrogen and carbon, known as ‘greens’ and ‘browns.’ These are the building blocks of food. Green materials are often, but not always, green in color, and the classic browns are dry leaves.
There are charts and tables that tell you precise ratios of carbon to nitrogen, but all you really need to know is that you need some of both.
To help you compost effectively, a little planning helps, since there are seasonal abundances of different materials at different times of the year. The spring and summer growing seasons bring plenty of fresh green material, but there is little dry brown landscape waste. The converse is true in the fall, when leaves are dropping and nothing new is growing. Some people stockpile leaves over winter to use when necessary, or you can use alternatives such as sawdust or well-shredded newspaper.
While the ‘greens’ and ‘browns’ make up the bulk of your compost, most other organic materials can be composted, with some exceptions. (See next section, ‘Safety Concerns.’) Gardeners often seek out materials that add potassium, calcium, phosphorus, magnesium, and other micronutrients. Using a variety of materials improves compost, according to the same principle that a diet that includes a variety of foods is likely to provide necessary nutrients.
Heat, air, and water
Compost doesn’t have to get ‘hot.’ Compost snobs are always going on about how hot their compost gets. A productive pile can reach temperatures of 150 F or more. This heat is a byproduct of microbial metabolic activities. Hot compost has its benefits; the most important being that heat kills seeds and soil-borne diseases. The catch is that most hot piles are only really hot in their center; materials toward the perimeter won’t be sterilized. Again, unless you are willing to invest the time in perfecting your composting techniques, it’s easier to just accept what nature gives you. Many composters are delighted with the volunteer plants from their compost pile. Just practice a little prudence and don’t add seeds that you don’t want to propagate (e.g. ripe seed heads from a pernicious weed).
Aerate and irrigate.
The composting process will speed up if the microbes have sufficient water and air. Ideally, materials should be as wet as a wrung-out sponge. Add water and fluff up the materials with a tool appropriate to the size of the job (i.e. a pitchfork is ideal outdoors, but not for mixing a 5 gallon bucket.) There’s a tool called a compost aerator that looks like a cane with a pointed end that’s worth the $20.00 investment for any size compost system.
The more surface area exposed, the faster composting occurs.
Consider wood, a brown (carbon-rich) material. A log will eventually rot, but it will take awhile. Wood chips will break down faster, and sawdust, very quickly. Remember this principle if you are wondering why the whole apple you threw in your compost bin still looks about the same three months later. This also illustrates the time and energy issue. If you spend some time shredding your materials prior to composting, the compost will be ‘done’ faster. Some composters swear by running their food waste through the blender or food processor.