Where the natural gas found? Why is natural gas called a clean fuel?

India has huge reserves of natural gas. It has been found in Tripura, Rajasthan, Maharashtra and in the Krishna Godavari delta. It is advantageous to use CNG as a fuel because it is less polluting than petrol. It is a clean burning fuel. It produces 45% less hydrocarbons than petrol. The great advantage of CNG is that it can be used as fuel in homes and factories where it can be supplied through pipes.