Page 70 - Biofuels Refining and Performance

Photosynthetic Plants as Renewable Energy Sources 53

High yield/high conversion efficiency
Low level of contaminants

Energy plantations and cropping are means of growing selected
species of trees or crops that can be harvested in a shorter time for fuel,
energy, and other resources. Each type of popular plant species is dis-
cussed in brief, with respect to renewable resources.

Euclayptus. It is a fast growing plant for firewood (see Fig. 2.5).
Different species such as Eucalyptus nitens, E. fastigata, and E. globu-
lus are used in many countries such as Australia and Brazil. Eucalyptus,
an exotic species from Australia, is a versatile tree which adopts itself
to a variety of edaphic and climatic conditions. It comes up in different
types of soils and climates varying from tropical to warm temperatures
and with annual rainfall ranging from 400 to 4000 mm. It grows well
in deep, fertile, and well-drained loamy soils with adequate moisture.
A large eucalyptus plantation program has been successfully launched
in Brazil to serve as the feedstock for its methanol plant. Amatayakul
et al. suggest that if eucalyptus wood is used for electricity generation,
the cost of electricity generation would be 6.2 US cents/kWh, and con-
sequently, the cost of substituting a wood-fired plant for a coal-fired
plant and a gas-fired plant would be US $107 and $196 per ton of C,
respectively [6]. Eucalyptus plantations could offer economically attrac-
tive options for electricity generation and CO abatement.
2
Casuarina. Casuarina is a genus of shrubs and trees of the Casurinacea
family, native to Australia and islands of the Pacific. The species involve
Casuarina equisetifolia Linn. It is a big evergreen tree with a trunk
diameter of 30 cm and height 15 m, and is harvested after 5–7 years (see
Fig. 2.6). The plant fixes nitrogen through symbiotic bacteria and thus
adds fertility to the soil. It is very useful for afforesting sandy beaches
and sand dunes. The wood is used for fuel purposes.

Figure 2.5 Eucalyptus plantation.