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product partitioning incorporating multi-phase separation, probably including size grading, a degree
of “gravity” separation and pneumatic separation. This equipment would be anticipated to be either
fixed or re-locatable, but not mobile for “infield” use.
Case by case evaluation of the economics of different strategies will be required, with factors such as
eventual Industry size and distribution having a significant impact on future development paths.
4.3 Mallee Products and Conversion Technologies.
A range of products can potentially be derived from mallee trees, with three main processes being
utilised:
• Extraction of oils. Whilst a number of processes can be utilised for the extraction of oils from
biomass, with mallee the main source of oils is in the leaf material and steam extraction is
considered the most appropriate technology;
• Thermal conversion. Thermal conversion ranges from combustion, where the aim is to
maximise heat recovery for process heat or electricity generation, to a range of processes
where the combustion process is controlled and targeted products are produced. The process
can be manipulated to maximise output of a range of products from charcoal to combustible
gasses. Gasses can then be further converted into liquid fuels (e.g “bio-crude”). Heat is also
liberated. The process is well described by El Bassam (2010). Figure 4.5a illustrates the mass
balance of the process of gasification and bio-oil production from a biomass crop, with the
basis being 1000 kg of feedstock dry-material prior to the conversion process. Figure 4.5b
gives the energy balance for material at 25% moisture content initial condition. The actual
conversion efficiencies to the nominated end products can be manipulated by the temperature
of the process, with higher temperatures favouring higher production of gasses and oil, and
lower temperatures favouring the production of char.
• Physical conversion. Physical conversion of biomass is in the context of a bioenergy crop is
primarily by processes such as briquetting or pelleting. This strategy is primarily used to
“standardise” the product and maximise density for transport.
Whilst the oil extraction process and physical conversion require the addition of energy, thermal
conversion is essentially exothermic. Whilst thermal conversion technology has been used on a large
scale for many years (charcoal production, Fischer Tropsch for liquid fuel production and “producer
gas” for stationary applications) technology is developing rapidly.
Figure 4.5(a) Mass balance of biomass conversion using fast pyrolysis.(El Bassam 2010)
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