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Bulk density will be a key consideration in the efficiency of infield and road transport. Therefore, if
the load was sufficiently fluffed up by tipping, then transport efficiency will be affected.
Due to the small proportion of particles that are long, and the flat shapes of the chip and leaf
particles, it is probable that tipping from bin to bin will agitate the material and reduce the bulk
density. It is known that tipping sugarcane billets from bin to bin in side-tipping sugarcane haulouts
reduces the bulk density of the product after transfer.
The effect of product composition on bulk density is not known. It is hypothesised that leaf may
increase the bulk density in an undisturbed sample because they are quite dense and could potentially
fill the voids between the wood chips. The fact that chip trucks achieve similar mass loads whether
loaded with clean chip or whole tree biomass suggests that the foliage and residues have little impact
on bulk density within the ranges of biomass composition observed during trials, such as the one
illustrated in Figure 2.9.
Wood chippers are also known to achieve some packing when the particles are thrown out of a chute
rather than allowed to tumble off the end of an elevator. Therefore, one strategy to avoid reducing
bulk density may be to fill bins and then handle and transport the bins from the harvester to the
destination without tipping to avoid agitating the product.
The bulk density of product in large capacity infield transport, after transfer onto road transport or at
the final destination point has not been determined. Data on material bulk density should be
collected when the harvester commences full scale infield trials.
2.3.4 Product quality
For agricultural commodities with no post-harvest processing, a clean wholesome product is of
primary importance in marketing. Losses in quality are thus evidenced by a decrease in the market
value of the product.
For agricultural produce which are subject to post-harvest processing, the aim is to maintain or
enhance the quality of the products and make it readily marketable. Higher product quality after
harvest will lead to lower processing costs, better quality processed products and thereby maximising
the value of the product.
Sugar System
Sugarcane is a perishable commodity and must be processed into sugar quickly after it is harvested
otherwise its commercial value deteriorates. Australian sugarcane mills organise their railway
scheduling to ensure that most harvested cane is crushed within 12-16 hours of harvesting, with only
a small proportion crushed 16-24 hours after harvesting. All cane is crushed within 24 hours of
harvesting unless there is a temporary transport problem (Dawson, 2004).
Cane supply quality (high extraneous matter) and post-harvest sucrose losses are linked with low
sugar recovery and several problems during sugar processing.
Post-harvest sucrose losses can be attributed to bio-deterioration which is associated with the
inordinate delays between harvest to milling and aggravated by many intrinsic and extrinsic factors
causing enormous depreciation in cane tonnage as well as sugar recovery. Besides harvest-to-mill
delays, other factors such as ambient temperature, humidity, cane variety, period of storage, activities
of invertases and maturity status are responsible for a decline in sugar recovery. The activity of
invertases and proliferation of acid, ethanol and polysaccharides (dextran) producing microbes play a
crucial role in the loss of recoverable sugars in cane and milled juice. In addition to loss in sugar
recovery, its adverse affects has been noticed in the sugar manufacturing process and sucrose quality.
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