In the 19th century, the most efficient fuel was burning coal. If you assumed that the center of the Sun was all coal (why is this reasonable?), how long could the Sun burn at it's present luminosity?
How many molecules are there to burn?
How much energy will be released in the lifetime of the Sun?
How long will the Sun last if it burns coal in the core?
This can be made 10 times longer burning hydrogen (why?), but it is
still much to short to explain the existence of Earth for thousands,
millions, billions of years.