LPG is a mixture of lowre hydrocarbons. It has very low ignition temperature and the heat evolved per unit mass of LPG called calorific value of the fuel is very high. Coal is an allotropic form fo carbon and as very high ignition temperature. Its calorific value is very low. Apart from these two reasons, LPG undergoes complete combustion and does not produce any ash. Burning coal produces ash and causes acid rain due to the presence of nitorgen and sulphur in it.
