What is Composting and what are its basic steps?

Composting is an aerobic microbial process which degrades organic matter to produce a relatively stabilised residue; carbon dioxide is the main gaseous product. The composting methods may use either manual or mechanical means and are accordingly termed as manual and mechanical composting processes.

Composting yields a product that contains plant nutrients (nitrogen, phosphorus and potassium) as well as micronutrients, which can be utilised for plant growth? Prior to composting, some salvageable materials are removed, recycled and reused. Thus, a major portion of the input waste material is reused, resulting in conservation of natural resources. Composting is thus a useful method, especially in predominantly agricultural countries. .

Process description

Most composting operations consist of three basic steps:

(i) preparation of the solid wastes

(ii) decomposition of the solid wastes

(iii) product preparation and marketing.

Receiving, sorting, separation, size reduction and moisture and nutrient addition are part of the preparation step. To accomplish the decomposition step, the following techniques have been followed:

(i) traditional windrow composting

(ii) aerated static pile composting

(iii) mechanical composting (in-vessel composting)

(iv) vermi composting.

For each method, the key factors are sufficient moisture and effective distribution of air. Disadvantages include the requirement of relatively large areas on which to place the material to be composted, and unless special precautions are taken, the potential for nuisance due to odour, vermin, insects, rodents and birds are much probable.