Environmental Engineering Reference
In-Depth Information
energy credits, and even a carbon credit. An Integrated Mallee Processing plant in each mallee
growing area could convert 100,000 Mg per year of mallee (i.e., 50,000 Mg each of leaves and
wood) into approximately (1)
Eucalyptus
oil 1600 Mg, charcoal 8300 Mg, and activated carbon
5000 Mg; (2) electrical energy 2.3 MWh and energy 8.6 MWh; or (3) electrical energy 5.1 MWh,
depending on the conversion process.
A harvester/chipper was developed to produce material suitable for large-volume materials han-
dling systems and low-cost feedstock for oil, charcoal, and thermal energy (Baker et al. 1999). The
machine can harvest and chip mallee stems up to 6 m height and 150 mm basal diameter. The leaf
material is separated from the other material before oil distillation. Although the system is for the
oil mallee industry, it may be applied to any SRWC. Processes and conversion techniques for utiliz-
ing biomass for energy included cogeneration, cofiring, gasification, charcoal, gas, liquids, diges-
tion, and fermentation.
Larger scale plants may follow because the dryland salinity problem extends over millions of
hectares. Direct liquefaction of
eucalyptus
mallee costs less and has higher transportation efficiency
to a central user or processing facility (Bridgwater et al. 2007).
SRWCs and their bioenergy products in the South Australian River Murray Corridor could have
both local and global environmental benefits (Bryan et al. 2008). Some 360,000 ha could produce
over 3 million tons of green biomass annually and reduce annual carbon emissions by over 1.7 million
tons through bioenergy production and reduced coal-based electricity generation. River salinity could
be reduced by 2.65 EC (mS/cm) over 100 years, and over 96,000 highly erosive ha could be stabilized.
Despite these significant opportunities, forest bioenergy has developed little in Australia, except
for firewood for domestic heating. Public acceptance and support are lacking, especially for the use
of natural forest residues, the main biomass source.
15.2.1.5 new zealand
New Zealand has 18 million ha of short rotation hardwoods for multiple use, but only 6.3% of
its energy is obtained from biomass (Wright 2006). Of several
Eucalyptus
species evaluated as
SRWCs, after five 3-year rotations,
E. brookerana
and
E. ovata
were the most productive, achieving
yields as high as 50 dry ton/ha per year (Sims et al. 1999a, 1999b). At an even higher initial planting
densit y,
E. pseudoglobulus
yielded more after the second 3-year rotation than the top performing
E. viminalis
clone did in the first (Sims et al. 2001). SRWC genotype selection appears to require
evaluation over several coppice rotations.
15.2.1.6 united states
In the United States, which at 103 EJ is the most energy-consumptive country, bioenergy contributes
approximately 2.8%, with approximately 60% of this produced and consumed by the forest products
industry (Wright 2006). Annually, approximately 40% of 250 million dry ton of wood is used for
energy. By 2030, forest bioenergy could double (1.7 EJ) with improvements in forest productivity
and biomass conversion. At present, approximately 50,000 ha of SRWCs are planted in the United
States, with
Eucalyptus
deployed in California, Hawaii, and Florida.
Hawaii
. An extensive, broad research and development program examined how to grow SRWC
Eucalyptus
for bioenergy on up to 100,000 ha of former sugarcane land on the island of Hawaii
(Whitesell et al. 1992). Techniques were developed for seedling production and plantation site prep-
aration, weed control, planting, fertilization, and yield estimation. Tree biomass equations were
derived for
EG
,
E. saligna
,
Albizia falcataria
,
Acacia melanoxylon
,
E. globulus
,
E. robusta
, and
EU
(Schubert et al. 1988, Whitesell et al. 1988). Mean annual increment of SRWC
Eucalyptus
did not peak before significant competition-related mortality, slightly beyond likely harvest age.
Although stand densities of 3364-6727 trees/ha had the highest production, their trees did not reach
the minimum tree diameter, suggesting that yields at lower densities will equal or surpass higher
density yields in longer rotations. To achieve a minimum tree DBH of 15 cm in 5 years, stand den-
sity must be less than 1500 trees/ha.
