Environmental Engineering Reference
In-Depth Information
Fig. 2.1
Detailed process
of alcohol production
eries are an agro-based industry with around 300
units located mainly in rural, sugarcane-growing
regions. The total installed capacity is 3250 mil-
lion L alcohol per annum with an estimated
production of 2300.4 million L in 2006-2007
(Ethanol India
2007
). Bioethanol is produced
worldwide for beverage, industrial, chemical,
and some fuel use, by fermenting agricultural
products such as molasses, sucrose-containing
juices from sugarcane or sugarbeets, potatoes,
fruits, and grains (notably maize, wheat, grain
sorghum, barley, and rye). With growing popula-
tion, industrialization, and energy consumption,
coupled with an increasing reliance on fossil
fuels, the energy security needs of the world con-
tinue to escalate.
a.
Feed Preparation
Ethanol can be produced from a wide range
of feedstock. These include sugar-based (cane
and beet molasses, cane juice), starch-based
(corn, wheat, cassava, rice, barley), and cellu-
losic (crop residues, sugarcane bagasse, wood,
municipal solid wastes) materials. In gen-
eral, sugar-based feedstock containing read-
ily available fermentable sugars are preferred
while Indian distilleries almost exclusively
use sugarcane molasses The composition of
molasses varies with the variety of cane, the
agroclimatic conditions of the region, sugar
manufacturing process, and handling and stor-
age (Godbole
2002
).
b.
Fermentation
Yeast culture is prepared in the laboratory and
propagated in a series of fermenters. The feed
is inoculated with about 10 % by volume of
yeast (
Saccharomyces cerevisiae
) inoculum.
This is an anaerobic process carried out under
controlled conditions of temperature and pH
wherein reducing sugars are broken down to
ethyl alcohol and carbon dioxide. The reaction
is exothermic. To maintain the temperature be-
2.2
Critical Review
2.2.1
Process of Ethanol Production
Alcohol manufacture in distilleries consists of
four main steps, viz., feed preparation, fermenta-
tion, distillation, and packaging (Fig.
2.1
).
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