Question

Why do we not use coal gas as a cooking fuel???

Answer 1

Thanks for asking the question. 
Well, coal is a natural resource. This is because we get coal from dead plants and animals buried in the Earth's crust millions of years ago. Fossil fuels take a lot of time for their formation. As they are not present in large quantities therefore, we cannot use coal excessively. This is the reason why we do not use coal as a cooking fuel.
Hope it helps.

Answer 2

we do not use coal gass as acooking fyel because it consists of 3 combustible gases namely hydrogen, methane and carbon monoxide. coal gas has high calorific value as both hydrogen and methane have high calorific values.