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Table 2.4 EM levels in cane supply
Cane Supply Percent Percent Percent
Component Biomass Weight Biomass Weight Biomass Weight
SRDC (2006) SRDC (2004) Whiteing (2001)
Clean Cane 90.4 87 89.4
Tops 4 5.0 5.0
Trash 5 6.5 4.8
Dirt 0.6 1.5 0.8
Mallee System
Product specifications for woody biomass are most likely less when compared to other agricultural
commodities. Lower chip specifications are acceptable for energy or oil utilisation. However,
chipping of whole trees introduces other considerations, particularly the production of long particles
such as sections of small branches, which add significantly to the difficulty of handling the bulk
biomass (McCormack et al. 2009).
The chipped biomass in its unsorted state is a mixture of wood chip, leaf, and residues of assorted
fines, bark and small twigs (see section 1.2.1 for more detail). The proportions of wood, leaf and
residues is about one third each, but these values vary widely according to tree species and age at
harvest. Younger, smaller trees have high proportions of leaf and less wood, and the proportion of
wood increases with age (Peck et al, 2011). The leaf proportion also declines with increasing
competition between mallees as the leaf area is regulated by the availability of soil moisture, so
mallees grown in blocks rather than belts can be expected to have higher proportions of wood.
However higher proportions of any one component does not equate to higher yields – the most
important factor remains to maximise productivity because in most instances this will increase the per
hectare yield of all constituents of the biomass.
It is expected that mineral content other than traces of dust will be minimal as the trees don’t touch
the ground with chipper harvesting and the saw works at least 50 mm above ground level. The
harvesting head of the current prototype is attached on the tractor’s three point linkage and supported
by wheels to maintain its position above the ground, and future harvesters will also be designed to
avoid contact of the ground by the saw.
The size and shape of the chips will also impact on the bulk density of the material. The size and
shape of the chips is known to vary with the chipper’s linear feed rate as this determines the length of
fibre in each chip, and chip length and thickness are positively correlated.
The product is not perishable over periods of a few days but the impact of this product composition
on spoilage should be investigated. It is known from the forest industries that clean chip, properly
stacked, can be stored for extended periods, but the leaf and other fine materials, either alone or
mixed with the chip, will cause stack heating, decomposition, and potentially result in fire. Fine
materials will need to be dried prior to storage for more than about a week.
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