The increasing demand for energy is largely being met by the use of fossil fuel - coal and petroleum. But these fuels are exhaustible and non-renewable sources of energy. Moreover, burning of fossil fuels causes air pollution. Release of acidic oxides leading to acid rain affects our water and soil resources. These gases also produce greenhouse effect leading to rise in temperature. Then, there is a problem of disposal of ash produced due to burning of coal. Thus, our environment is being degraded.