Composting is a relatively simple process. The point is to take waste organic matter from the yard and home and turn it into viable bedding and fertilizer for the yard and garden. However, there are many ways or systems used in order to make compost, each intent on providing high-quality compost as quickly as possible.
The three-bin compost system, as the name suggests, uses three separate receptacles in order to allow the gardener to generate a near-constant supply of compost. A compost pile is begun in the first bin, as normal. The decay process begins, and the rapid breakdown of plant matter and reproduction of bacteria produces heat. The compost pile is turned into the second bin once the internal temperature reaches 140 to 150 degrees Fahrenheit. Turning the compost into the second bin aerates and cools it, providing it with the oxygen it needs to keep decaying. Meanwhile, another pile of compost is started in the emptied first bin. The compost in the second bin is turned again into the third bin when its internal temperature climbs back up. The compost in the third bin is ready to be spread throughout the garden, and the process with the first two bins is repeated as necessary.
Tumbler compost systems utilize a large enclosed container, such as a plastic drum set on a central spindle. Composting ingredients are poured into it, the lid is closed tightly and the drum is spun. This serves two purposes: to more thoroughly mix the various composting ingredients, and to increase the amount of oxygen infusing the ingredients. The belief behind this system is that by consistently aerating the compost it increases its rate of decay. To this system's credit, compost is typically produced a week faster than normal bin composting systems, but it falls short of the claims that compost can be produced in as little as two weeks. It typically takes four or five weeks instead of six.
Worm-bin compost systems are typically used indoors in places where city and town ordinances prohibit outdoor compost piles for fear of attracting animals. They are normally plastic or Tupperware containers with a few holes in the top for ventilation into which a thick bedding of yard debris is cast along with kitchen scraps. Red worms, a species used to living in rotting refuse, will churn through the debris, aerating it, while eating much of the kitchen scraps. The resultant dung is used as a very effective fertilizer.