Page 214 - Biofuels Refining and Performance

Ethanol and Methanol as Fuels in Internal Combustion Engines 197

mixed with water and enzymes, and cooked at 150 C to convert starch
to sugar. The mixture is then cooled and sent to fermentation tanks,
where yeast is added and the sugar is allowed to ferment into ethanol.
After 60 h in the tanks, the mixture is sent to distillation columns, where
ethanol is evaporated out, condensed, and mixed with unleaded gaso-
line to form gasohol, which contains 90% gasoline and 10% ethanol.

Tapioca materials. Tapioca is available in plenty in Asia, the United
States, central Europe, and Africa. Its production can be increased
through modern cultivation techniques. The process consists of con-
verting the tapioca flour into fermentation sugars with enzymes prior to
fermentation with yeast. Modern technology uses -amyl glycosidase,
one of two enzymes required in the process, and then saccharification
of the material into alcohol by using yeast.

Anhydrous alcohol from vegetable wastes. The Philippines has embarked
on an “alcogas program” to produce its own anhydrous alcohol from
local vegetable wastes for blending with petrol. The program is cur-
rently based on sugarcane juice and molasses, but it plans to diversify
by using other raw materials. In the basic process, cellulose conversion
begins with the pretreatment of the raw materials, which may include
coffee hulls, rice straw, grass—even sawmill wastes. Enzymes then take
over by converting the feedstock into a sugary liquid that is fermented
and finally distilled into anhydrous alcohol. After distillation, waste
residues can be evaporated into syrup to feed animals, while uncon-
verted cellulose is used as the primary fuel for the plant. If the
Philippines could engineer a breakthrough in this area, its agricultural
and forestry wastes could supply energy equivalent to 9720 mL of oil
annually. In the years to come, this new energy source could make a sig-
nificant economic impact on a country that depends on imports of crude
oil for 95% of its energy.
Manioc. As oil prices continue to rise, more and more work is being done
on alternatives. Manioc is one such staple crop in many tropical lands.
Brazil has planned to use manioc in its ethanol production plants, aiming
3
to make 35,000 bbl a day from 400 10 ha of manioc plantation.
Conversion of manioc to ethanol is somewhat more complex than is the
case with sugarcane. The raw material has to be turned into sugar by fer-
mentation. This first step requires the use of enzymes. Danish Co. has
developed the necessary heat-resistant enzymes in a pilot plant in Brazil.
Manioc does not grow in higher temperature zones; so scientists have
turned to other plants, and there is work being done in Sweden that is
in an advanced stage. They have developed fast-growing poplars and wil-
lows. Their yield is 30 ton/ha, which is equal to 12 tons of fuel oil.