Compost is organic matter that has been decomposed and
recycled as a fertilizer and soil amendment. Compost is a key ingredient in
organic farming. At the simplest level, the process of composting simply
requires making a heap of wetted organic matter (leaves, "green" food
waste) and waiting for the materials to break down into humus after a period of
weeks or months. Modern, methodical composting is a multi-step, closely
monitored process with measured inputs of water, air, and carbon- and nitrogen-rich
materials. The decomposition process is aided by shredding the plant matter,
adding water and ensuring proper aeration by regularly turning the mixture.
Worms and fungi further break up the material. Aerobic bacteria manage the
chemical process by converting the inputs into heat, carbon dioxide and
ammonium. The ammonium is further converted by bacteria into plant-nourishing
nitrites and nitrates through the process of nitrification.
Compost can be rich in nutrients. It is used in gardens,
landscaping, horticulture, and agriculture. The compost itself is beneficial
for the land in many ways, including as a soil conditioner, a fertilizer,
addition of vital humus or humic acids, and as a natural pesticide for soil. In
ecosystems, compost is useful for erosion control, land and stream reclamation,
wetland construction, and as landfill cover (see compost uses). Organic
ingredients intended for composting can alternatively be used to generate
biogas through anaerobic digestion. Anaerobic digestion is fast overtaking
composting in some parts of the world including central Europe as a primary
means of downcycling waste organic matter.
