Two of the bacteria types that work to decompose fall into these categories: aerobic and anaerobic. Aerobic bacteria are living organisms that require oxygen to survive; anaerobic bacteria do not require oxygen for growth and may actually die when exposed to it. The decomposition by these bacteria releases nutrients present in the organic material and releases it back into the environment.
As I mentioned in the earlier article, the microorganisms that break down organic matter require three things: food, water, and oxygen. How you control those three components determines how quickly your pile decomposes. Notice I mention oxygen. You want the aerobic bacteria in your pile. They're efficient and don't produce a bad smell as a byproduct of decomposition like anaerobic bacteria do.
Composting is an activity that offers control over the decomposition process. One part of the process where you influence the make-up of your pile is in the choice of what you compost and how you do it.
You decide what food the microorganisms eat. Just about anything organic is on the menu. These organics fall into the two broad categories of plant-based or animal-based material. Plant-based organics are derived from plants, living or dead. Animal-based organics include actual parts of an animal, but most often consist of animal waste products, usually in the form of manure.
I've already mentioned a number of plant-based items you can throw in your compost pile that come from the kitchen and garden. Some of these things are obvious, like banana peels, celery tops, leftover salad, tea bags, leaves, watermelon rind, and dried out flower arrangements. Don't limit yourself to obvious contributions. Think about things you would throw away that are plant-based products. Things like pizza boxes, stale bread, toilet paper rolls, used cotton balls, leftover rice, stale beer, dryer lint, used paper plates, and shredded bills can all be composted.
Many animal-based items can also be tossed in the compost pile, with some important restrictions. Pet hair, egg shells, and old wool shirts can be used. Manures of all types from plant-eating animals should be a regular addition to your pile. While bones, meat, fat, and fish guts are organic and will decompose, I don't recommend them for most compost piles. Besides smelling bad as they decompose, those ingredients can attract cats, dogs, bears, and many other wild animals that will tear up your pile looking for the smelly food and you probably don't not want them in your garden. Never add cat or dog feces; they can transmit diseases. If you need to add nitrogen to balance the carbon, blood meal and bone meal are good sources, if you don't have local animals that will tear up your pile to eat them.
You have a few options of how you add material to your pile. You can take the easy (semi-lazy) way by adding material when it is available. This is the approach I take most of the time. You rake leaves; throw them on the pile. You prune your raspberry canes; throw them on the pile. You have a bucket of grapefruit halves and watermelon rinds; throw them on the pile. You have a half-dozen broken jack-o-lanterns; throw them on the pile. The pile can grow to a large mass pretty quickly, but the pieces will be big and chunky.
There are things that will never decompose no matter how long you have them in your pile. They can almost always be categorized as inorganic. Stones, rubber chunks, and plastic bottles won't decompose. Some metals will tarnish or rust, but they don't deserve a place in your pile. Glass, ceramic, and clay pots may literally break down in your pile, but they don't add any nutrients and should be avoided. Keep your pile organic.
Once all of the material is in the pile, it decomposes quickly or slowly depending on the amount of water and air that are added to the mix. When the microorganisms are busy they generate heat and that heat encourages the growth of more organisms. More organisms means there's a need for more oxygen. This is where you decide how much effort you'll make in your composting activities. And that's where I'll pick it up again in the next article.