Any material which cannot be used in the form in which it is produced is called a waste. It is no longer needed by us because it has lost its value. If thrown around, it can cause soil, air or water pollution. It poses a serious threat to normal life, plants, animals and human beings.

Types of Waste on the Basis of their Physical State
    Wastes can be divided into the following three categories on the basis of their physical states.
    1. Solid waste
    2. Liquid waste
    3. Gaseous waste

    •    Garbage : Municipal solid waste is commonly called garbage. It includes only non-liquid wastes generated from households and other commercial places. Waste includes all the three types of wastes whereas garbage includes only solid wastes.