We are clearly hooked on fossil fuels. Our consumption went down during the mid 1970 s, but has started increasing again. At the present rate of 22 billion barrels a year, our global reserves of 990 billion barrels is good for approx. We have 200 to 500 years of coal supplies on Earth. The remains of dead plants.
Plants convert sunlight to stored fuel which is used for energy.
So fossil fuels are essentially stored solar energy . Through metamorphism, water and volatiles are squeezed out, leaving essentially carbon. Generally Carboniferous and Permian in age. Bituminous coal from the Eastern U.S. is dirty. Contains lots of sulfur.