Download (4Mb) - USQ ePrints - University of Southern Queensland

Carbon sinks
Planting of mallees to absorb and store carbon based pollutants from the
production of Greenhouse gas emissions.
In consideration of the specific markets that the biomass is to be used for, the fundamental market
characteristics must be considered. If the wood chip is to be used to make charcoal products, larger
chips may be desirable as the smallest dimension (typically the thickness) influences the quality of
the end product. Consistency in chip size is also a factor so that the chips all pyrolyse over a similar
time. If leaf oil is is the target market, a comminution process that strikes an optimum balance
between flowable bulk biomass and minimum leaf damage is preferred, as the leaf oil is volatile and
increased leaf damage increases oil evaporation.
Apart from extractives such as oil, foliage will most likely become bioenergy feedstock which does
not have very specific particle requirements. Many bioenergy processes (e.g. co-firing with coal, fuel
pellet manufacture and pyrolysis for bio-oil) require fine grinding of the biomass prior to the
conversion process. Wood chip for any industrial process needs to be sound and of consistent size.
The comminution step on the harvester must maintain a focus upon wood chip quality.
Sugar system
In addition to raw sugar (the primary output), the mills produce useful by-products such as molasses
and bagasse. Molasses is the dark syrup separated from the raw sugar crystals during the milling
process. It is used as a raw material in distilleries where industrial alcohol (such as ethanol), rum and
carbon dioxide are made. Molasses is also used in feed for animals such as cattle, and is sold to both
the domestic and export markets. Section 4.1 of this document provides further detail.
Bagasse is the expended cane fibre which remains after the juice has been extracted. It provides
nearly all of the fuel required for steam and electricity generation at the mills. In addition, some mills
(e.g. Condong and Broadwater in NSW) have moved towards whole crop harvesting in an endeavor
to generate a significant amount of electricity that is added back into the grid. This is an ongoing
work.
Bagasse is also used as mulch (and potentially as a stockfeed) in areas where excess bagasse is
produced. By-products ash and filter mud are used as a fertiliser on cane farms and gardens. Boiler
ash is "scrubbed" from the mill stacks and filter mud is the residue left after the sugar has been
clarified.
Ash and filter mud are used as soil conditioners on cane farms and gardens. Boiler ash is scrubbed
from the mill stacks before the exhaust gases are released into the atmosphere. Filter mud is the
residue left after the sugar cane juice has been clarified.
Molasses is the black syrup remaining after the sugar syrup has been boiled and passed through the
centrifugal for the last time in the mill or refinery. About 50 percent of the molasses produced in
Australia is exported and the remainder is used in stock feed and in distilleries where industrial
alcohol (ethanol), rum and carbon dioxide are made.
18