Bio-mass and hydroelectricity as sources of energy. The following points compare them:

a) Both Bio-mass and Hydro-Electricity are renewable sources of energy.

b) The use of bio-mass by burning causes air pollution but the use of hydroelectricity do not.

c) Bio-mass gives heat energy which can be used for cooking and heating whereas hydroelectricity can be used for running all types of electrical appliances.

d) Bio-mass energy can be obtained without using any special devices but hydroelectricity can be produced only by establishing hydro-power plants.