2.1 Chemical composition of bamboo
The macrostructure of bamboo stem is similar to many species of grass family with distinct
nodes and internodes. Analyzing chemical components of bamboo shows the bamboo is
mainly composed of cellulose, hemicellulose, lignin, carbohydrates, fat and protein, etc. The
cell wall mainly consists of cellulose, hemicellulose and lignin (Chen 1984).
The cellulose of bamboo is a natural linear macromolecular compound which is jointed with
ß-D-glucoseⅠ - 4 glycocidic. The cellulose content in bamboo varies from 40% to 50% with
different species.
Hemicellulose is a kind of non-cellulose polysaccharide, inhomogeneous high polymeric
glycan, which consists of two glycosyl or more in the cell wall and the intercellular layer. It
has a branch structure. The hemicellulose’s content is in the range of 20% to 30%.
Lignin is an aromatic macromolecular compound together with cellulose and hemicellulose
in lignified tissue, and it is concentrated in intercellular layers. In the lignified tissue, the
lignin is mainly to stick the cellulose and hemicellulose and its content ranges from 15% to
35%.
The materials such as carbohydrate, fat, protein and nitride etc can be extracted from
bamboo. The cold-water extractive is 3.92%, and the hot-water extractive is 7.72%. The
alcohol-ether extractive is 4.55%, and the alcohol-benzene extractive is 5.45%. The
extractive with 1% sodium hydroxide is 27.26%,
Bamboo material can be burned to ash in high temperature. The ash content is in the range of
1% to 2%. The compounds of the ash exist in following forms: Potassium exists as
potassium oxide which is in the range of 0.5% to 2%; Silicon exists as silica is about 1.3%;
Phosphate exists as phosphorus pentoxide and is the range of 0.11%~0.24%. Besides these
compounds, there are some metallic elements with little content such as copper, iron,
calcium, magnesium and manganese.
Compared with the chemical composition of wood and grass plant, the cellulose content of
bamboo is higher than grass plant, less than hardwood, and similar to softwood. The lignin
content of bamboo is between softwood and hardwood but higher than grass. The ash
content in bamboo is 3 to 4 times more than wood but far less than grass (Ye et al 1989).