Water is heated to the boiling point and changes to steam.
At that point, either the steam is used for heating, or it is used to turn turbines to generate electricity. The amount of energy recovered from waste is a function of the amount of waste combusted, the energy value of the waste stream, and the efficiency of the combustion process. Most of the MSW incineration currently practiced in industrialized countries incorporates energy recovery in the form of steam, which is used either to drive a turbine to generate electricity or directly for heating or cooling. In past years it was common to simply burn MSW in incinerators to reduce its volume and weight, but energy recovery has become more prevalent since the 1980s. This trend is due partly to a preference for relatively stable electricity markets, such as utilities, as compared to industrial customers of steam, who are perceived as less reliable purchasers.