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7. Supply Chain Modelling and Economic
Considerations
Chapter six has discussed broad supply chain planning and management issues relevant to the sugar
and mallee industry. It was beyond the scope of this project to undertake a comprehensive value chain
assessment for the mallee industry. A desk-top assessment of the logistics for mallee supply in
Western Australia was undertaken to provide economic consideration of alternative harvest haul
systems and in particular identification of key drivers and cost sensitivity. The basis for this
assessment was the harvest-haul model discussed in section 6.5 (Sandell and Prestwich, 2004)
7.1 The Harvest-Haul Model
The Harvest Haul model is a deterministic model that estimates the time and cost performance of
harvest at a block level and aggregates results to the farm, group and regional levels. While the model
was originally developed for use in the sugar cane industry it is applicable to and has been used for a
variety of harvesting operations.
Industry issues that the Harvest Haul Model has been used to investigate include:
• Modelling new projects and conducting sensitivity analyses.
• Modelling harvesting cost changes for farm re-configuration.
• Comparison of current harvesting practices to Harvest Best Practice
• Modelling harvesting cost changes for full trash collection for co-generation
• Harvest group restructure or amalgamations
• Siding or pad location re-arrangements
• Haulout optimisation within a group to determine the cost effective number of haulouts
The Harvest-Haul Model has been used extensively in the Australian sugar industry from Condong
mill to Mossman mill and internationally for Fiji Sugar and Ramu Sugar in Papua New Guinea and is
applicable to biomass harvesting operations.
The model estimates the time performance of harvest and applies costs on an hourly basis. Block
area, tonnes, row spacing, row length, maximum ground speed and a target elevator pour rate are used
to estimate the time spent cutting. The time taken to turn at the end of the row is assumed.
Time spent waiting for haul transport is estimated by assuming that the first haulout has just left the
harvester. If this haulout can travel to the delivery point, unload and return in less time than the
harvester can fill the remaining haul capacity then the haulout waits for the harvester. Alternatively,
the harvester must wait for the haulout to return and this time is added to the total harvest time.
Variables such as haul distance, haul speed, unloading time, haul capacity and number are used for
this calculation.
This basic cut-turn-wait time is then increased by 6% to account for servicing (regular and scheduled),
3% for repairs (unscheduled break-downs) and 3%, 6% and 9% for moving between fields as
discussed later.
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