Biomass is the primary source of energy used by man.
The first people used only biomass fuels. The heat released during combustion was used by early humans:
a) to keep them warm
b) for protection (i.e. fire in order to scare wild animals).
c) to help them see in the evening (animal fat and oil in oil lamps, candles and torches etc.)
d) for cooking.
Later, fire was used for firing clay objects like jars, pots, vases, plates, to melt metals in order to build more powerful weapons or tools, but also for eliminating diseases.
In many parts of the world even today there are people who use biomass for the same purposes.
Many years passed until the man managed to use other renewable energy sources such as water and wind, creating mostly windmills, watermills and other simple mechanical construction.