Kenaf is herbaceous annual plant with a single, straight
un-branched stem that grows to a height 4 to 6 metres or 12 to 20
ft. and a diameter of 25 - 50 mm or 1 to 2 inch over a 5 to 7 months
growing season in a variety of climatic conditions. Similar to hemp,
the stem is characterized by a relatively thin outer layer (referred
to as bark or bast) and a wood like core.
The bark constitutes on average about 35 to 40% of the dry weight
of the stem, which contains long, slender fibers of length 2.5 to
4mm. The woody core makes up the remaining 60-65% of the stem
weight and consist of short fibers that are reportedly a rather
constant 0.50 to 0.60mm in length.
Chemically, the kenaf stalk overall is similar to wood. bark
fibers of hemp stalk contains significantly more cellulose and
holocellulose and significantly less lignin than either of hardwood
or softwood. Hemp core on the other hand contains less cellulose
than wood.
Non-wood fibers have some features that are superior to wood
fibers and others that represent clear disadvantages. Nonetheless it
is technically possible to manufacture high quality paper from all
of these fibers. A major issue with agriculturally derived fiber is
that in most regions of the world this tends to be harvested within
a narrow window of time, requiring storage of vast quantities of
biodegradable material for periods approaching up to one year.
Inventory and storage costs and costs of fiber loss in storage can
be significant.
Physical Characteristics of Kenaf and Softwood/Hardwood
Characteristics
Hemp
Softwood
Hardwood
Bark
Core
Whole
Length (mm)
2.5- 4.0
0.5-0.6
-
2.5-5.5
0.8-1.9
Alfa Cellulose
(%)
51.0
34.9
40.6
42+/-2
67+/-5
Holocellulose
(%)
81.1
71.6
74.9
69+/-4
80+/-1
Lignin (%)
11.8
18.3
16.0
28+/-3
4+/-2
Extractives (%)
2.8
4.8
4.1
3+/-2
5+/-3
Ash Content (%)
2.8
1.8
2.1
<0.5
<0.5
Kenaf is considered to be one of the highest producers of biomass
among plants in terms of tons/land/time. One hectare of kenaf can produce 15-20 tons of dry matter within a short
period of only 120 days. One hectare can yield 5 -7 tons of high quality fibers.