Government of New Brunswick

When leaves drop from a tree, they decay into soft black humus over time, without any help from people. When an animal dies, its remains slowly return to the earth. Anything that once lived will eventually decompose.

Composting is based on this natural process and begins with the thousands of microorganisms which live naturally in soil. They feed on a moist heap of organic waste materials, generating considerable heat in the process. Other groups of "decomposer" organisms go to work as the temperature rises, an ever-changing workforce of bacteria, fungi, and insects.

When the temperature drops, turning or stirring the pile gives the decomposers more oxygen and the heat builds again, helping to kill harmful bacteria. When all the easily decomposed material has been consumed, the temperature drops for the last time and earthworms and ants may move in, signalling that the compost is ready to feed new plants with its "recycled" nutrients.

Finished compost has the distinctive fresh smell of newly-turned soil or a forest floor in spring, and won't heat up again no matter how often you turn air into the pile. The ideal result of the composting process is crumbly, dark, soil-like humus where none of the original material can be identified. The nutrients stored in compost depend on the richness and variety of its ingredients, and on its exposure to harsh weather. But experienced gardeners know there is no such thing as bad compost!