A. Composting (the Process)

When biodegradable organic materials containing sufficient moisture and inorganic nutrients (especially nitrogen) are placed in a pile or windrow (elongated pile), a natural process known as self-heating often occurs. Microorganisms, mainly bacteria and fungi, begin to grow rapidly on the organics, using them as a food source and decomposing them. Because the microbes are not 100% efficient, some of the chemical energy stored in the organics is wasted and released as heat. A large enough pile will act as an insulator, retaining heat and leading to an increase in temperature, which up to a point helps to speed up decomposition. Thus, the organic material "self-heats" through the intense metabolic activity of the microorganisms. Eventually the readily biodegradable food supply becomes exhausted, growth and heat generation slow down, and the pile cools.

The process which employs self-heating for waste treatment objectives is called composting. It has been used for many years for treatment of agricultural wastes and in more recent times for treating sewage sludge, municipal solid waste fractions, certain industrial wastes, food scraps, and leaves and grass clippings.

 B. Compost (the Product)
As composting progresses, the original material becomes less recognizable, although certain structures, such as twigs and the veins of oak leaves, persist longer than others. The material darkens, acquires a granular texture, increases in water-holding capacity, becomes almost neutral in pH, and eventually develops the pleasant odor characteristic of freshly turned soil. Compost bears little resemblance to the original starting material.

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