Page 72 - Biofuels Refining and Performance

Photosynthetic Plants as Renewable Energy Sources 55

varieties of this species (Hawaiian, Cunningham, and Brazilian) are
commonly used for plantations in Hawaiian, Salvador, and Peru. The
Hawaiian and the Cunningham varieties are used for energy plantation
in India and Australia, respectively. A Hawaiian plantation of 1.27
hectares can support a 1-MW power plant. In Brazil and the Philippines,
it is converted into charcoal that has 70% of the heating value of oil.
Charcoal can be used to produce calcium carbide, acetylene, vinyl plas-
tics, pig iron, and ferroalloys. The low silica, ash, and lignin contents and
high cellulose content make this plant good for paper and pulp materi-
als, and also for rayons and cellophanes. It not only gives a prolific fuel-
wood yield but is also a nutrient-rich fodder for livestock.

Sugarcane. Sugarcane (Saccharum officinale) is a hardy plant that can
tolerate poor drainage, can be cultivated as a rotation crop, and can be
maintained for years. It is grown in fertile areas with more than 1000 mm
of rain and an abundant supply of water. The ethanol yields from this
are in the range of 3.8–12 kL/(ha
yr) [7].

Cassava. Cassava (Manihot esculenta), like sugarcane, is grown in trop-
ical climates with an average rainfall of 1000 mm. As it is relatively
drought resistant, it can withstand lower annual rainfall. It needs to be
grown annually and is difficult to mechanize, and compared to sugar-
cane, it is less energy efficient. Ethanol yields are estimated in the
range of 0.5–4.0 kL/(ha
yr).

Sorghum. Sorghum embraces a wide variety of plant types and, unlike
sugarcane and cassava, is found in the tropical summer rainfall zones.
While it can grow in as little as 200–250 mm annual rainfall, maximum
yields are obtained in a minimum of 500–600 mm rainfall. Compared
to other cereals, it can tolerate high temperatures. Due to its deep root
system and low rate of transpiration, it is exceptionally resistant to
drought. Ethanol yields of stems and grains of sorghum are in the range
of 1.0–5.0 and 2.0–5.0 kL/(ha
yr), respectively.

Babassu. Babassu (Orbignya sp.) is a palm popular in Brazil for the
ethanol derived from it. The mesocarp of coconut is the raw material for
ethanol production, with an estimate of 0.24 kL/(ha
yr).

Oil-bearing crops. Vegetable oils are the most promising alternatives to
diesel fuel. About 97% of all oil-bearing plants are grown in tropical
and subtropical climates. There has been some research into the use of
plant oils from sunflower, peanut, rapeseed, soybean, and coconut oils
as biofuels in unmodified/slightly modified engines. Seed-based oils are
shown to lead to slightly higher fuel consumption, probably due to their