The first cavemen took firewood from the forests as fuel. Even today firewood is still the main source of fuel for cooking in many parts of the world.
The material contained in the bodies of plants and animals is called 'biomass'. When the organisms die the biomass can be used as fuel for domestic purposes.
Firewood
Wood is a raw fuel. It is also a primary fuel which can be used directly to produce heat. It contains carbon compounds. Most of the fuels in use today consists of compounds of carbon and hydrogen.
