In waste-to-energy plants, heat from the burning waste is absorbed by water in the wall of the furnace chamber, or in separate boilers. 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.