Although the chemical composition of wood varies from species to species, wood is primarily composed of carbon, hydrogen, oxygen, calcium, potassium, sulfur, nitrogen and magnesium. Most wood contains some amount of water as well.
Wood is a fibrous and porous material composed of cellulose fibers. There are currently around 1 trillion tons of wood on Earth and the rate of growth is around 10 billion tons each year.
Wood is generally categorized into hard and soft wood. Wood is used for everything from furniture and paper to an energy source. When wood is heated, a quarter of its weight is released as water.