Composting is the controlled biological decomposition of moist organic solid matter to produce a soil conditioner. Because it requires oxygen, the process cannot be completed in water (saturated).
Composters are extremely helpful to the environment for several reasons. They improve the soil structure, porosity, and density, thus creating a better plant root environment. They increase moisture infiltration and permeability of heavy soils, thus reducing erosion and runoff.
Composters also improve water-holding capacity, as well as reduce water loss and leaching in sandy soils. They also supply a variety of macro and micronutrients and may control or suppress certain soil-born plant pathogens.
Composters supply significant quantities of organic matter to their environment. They improve cation exchange capacity (CEC) of soils and growing media, thus improving their ability to hold nutrients for plant use and bind and degrade specific pollutants.