The wood chips consist of a mixture of wood species resulting
from forest cutting. Wood mainly consists of cellulose, hemicellulose
and lignin and in general they cover respectively 40–60, 20–40
and 10–25 wt% [11]. The pyrolysis and combustion processes of
wood are complex because of the simultaneous degradation of
the three components. The decomposition temperature range of
the components is 315–400 C, 220–315 C and 150–900 C,
respectively [11]. Because lignin has such a wide temperature
range for decomposition, it decomposes less easily than hemicellulose
and cellulose. For temperatures below 300 C the wood
decomposition is mainly attributed to hemicellulose.