Question

what is a fuel? why gaseous fuel are more advantageous that solid fuels?

Answer 1

The machine provides the power to work; gas fuels are useful in comparison to concrete enhancements because there is no residue

Answer 2

A fuel is any material that can be made to react with other substances so that it releases chemical or nuclear energy as heat or to be used for work.
Calorific value is defined as the amount of heat energy produced on complete combustion of 1 kilogram of a fuel. It is expressed in a unit called kilojoule per kg. The higher the calorific value of a fuel, the more is its efficiency.The calorific value of gaseous fuels are more.When a gaseous fuel  burns, it gives off a great deal of energy. And unlike other solid and liquid fuels it does not leaves any ash. 
and it produces very little air pollution.
Due to the above reasons gaseous fuel is always better than solid and liquid fuels