- Wood has been used by man from the time he discovered fire. Over half the global population still depends on wood for cooking and heating.
- Wood is also used as fuel in many industries. The consumption of fuel wood in the world was estimated at 1.7 billion m3 in 1984.
- Two-thirds of this was utilised by the developing countries in Africa and Asia. Such massive use of fuel wood has resulted in extensive deforestation and consequent environmental degradation.
A major quantity of wood is used as firewood. The principal advantages of firewood are:
- It is a widely distributed source of renewable energy.
- It can be harvested by unskilled labour, using simple equipment
- When perfectly dry, 99 percent of it is combustible.
- It is a fuel which produces flame and is well-adapted to heating large surfaces.
- As all wood is composed essentially of the same substances, wood from most species can be used as fuel.
Plantation of trees for fire wood is called energy plantation.
What determines the value of particular wood as fuel.
There are hundred types of wood in a vast country like India. Of these only a few are selected as suitable fuel. Good firewood must:-
- be highly combustible,
- have a high calorific value,
- be easy to dry,
- not split when ignited,
- be non-resinous and non-smoky and
- be free from offensive odours.
Generally speaking hardwood (dicotyledonous) is better than soft wood (gymnospermous) as fuel. The former produces uniform heat over a long period of time. Soft wood burns rapidly to produce intense heat but only for a short period.