Palm shell and mesocarp fiber were identified as biomass
wastes that produced greater amounts of bio-char
(35.26 wt% and 29.80 wt%, respectively) compared with
the pyrolysis of EFB, which produced 29.05 wt% bio-char.
The weight loss or yield of bio-char may be attributed to
either a more extensive primary decomposition of the raw
material at higher temperatures or to secondary decomposition
of the solid product; as a result of these processes, the
pyrolysis conversion was increased [37–39]. Additionally, a
great difference in the pyrolysis behavior among the three
main components of biomass (cellulose, hemicelluloses and
lignin) plays an important role in the bio-char yield [40].
Yang et al. [40] have reported that cellulose, hemicelluloses
and lignin exhibit the highest to the lowest decomposition
rates, respectively, in the pyrolysis process. When the temperature is increased to more than 400 °C, almost all
of the cellulose will be pyrolyzed with a very small amount
of solid residue. According to the lignocellulosic contents of
palm oil wastes (Table 2), the EFB contains the greatest
amount of cellulose among the investigated biomasses.
Therefore, the low production yield of EFB bio-char can
be attributed to the high cellulose content of raw EFB.
However, mesocarp fiber contains a large amount of hemicelluloses
compared to the other studied biomasses, especially
palm shell. The higher hemicellulose content of
mesocarp fiber makes the yield of these bio-chars lower
than that of palm shell bio-char. Finally, palm shell, which
contains low levels of cellulose and hemicelluloses and a
high level of lignin, shows the highest yield of bio-char
because, among the three components, lignin is the most
difficult to decompose.
As evident from the results in Table 1, EFB shows the
highest volatile percentage compare with the other two
biomasses. Although, mesocarp fiber (Table 6) shows the
highest volatile value after pyrolysis, the high volatiles
(40 %) and ash contents of EFB (12 %) may be responsible