A compost machine is a piece of equipment designed to store waste material while it decomposes, or becomes “composted.” Since it is often barrel-shaped with a lift-up door to deposit material through, it is sometimes called a compost bin. The machine may be made of various materials, but they are most commonly constructed of thick lumber or heavy-duty plastic. In addition, many compost machines are made of recycled materials.
The purpose of composting is to turn yard waste into organic fertilizer. However, other waste matter can be composted in addition to grass clippings and brush trimmings. In fact, shredded newspaper can be composted, as well as kitchen waste such as eggshells, vegetables, and some fruits. Citrus fruits should never be added to the compost machine since their acidic content will destroy the beneficial bacteria needed to produce compost.
The composting “recipe” depends upon just a few simple ingredients. For example, in addition to organic matter (i.e., grass and leaves), the compost heap needs some soil to provide a source of microorganisms. The task of the microorganisms is to degrade the organic material by breaking down the carbon content into fertilizing nutrients, such as nitrogen and potassium. However, in order for this biological reaction to occur, water and oxygen are also needed.
Oxygen is added to the compost mix by periodically turning the compost in order to allow air to circulate through it. This simple action will promote aerobic respiration, which allows the microorganisms to multiply and release carbon dioxide. The latter activity generates heat, which helps to “cook” the compost. In fact, the temperature inside a compost machine can reach up to 150 degrees Fahrenheit (66° Celsius).
Water is needed to keep the compost “alive.” However, the mixture should be kept moist, not saturated. The addition of water not only helps to facilitate decomposition, but also assists in the migration of other forms of beneficial organisms throughout the compost. For instance, tiny predators, such as nematodes, feed on the bacteria and fungus that develops in the compost and contributes to the nutritional value of the final product.
There are different types of compost machines available for purchase. A simple compost machine can also be made at home from scrap wood and chicken wire. To promote aerobic respiration, the container is vertically situated, left open at the bottom, and the compost manually turned with a shovel or rake. Other systems involve using multiple bins into which the organic matter is stacked and rotated. Finally, a rotary compost machine is mounted so that it — or some of its parts — can turn freely to provide oxygen.