dard of E10 fuel. In order to run an automobile completely with
Bio ethanol production form food sources are called as first
ethanol the engine should be specially designed for that.
generation biofuels. Using food sources as feed stocks for bio
ethanol creates the contest of “food vs fuel”. As a result of this
The first developed ‘model T’ automobile was designed to oper-
now there are ongoing researches to produce bio ethanol from
ate with ethanol and it was the first automobile that many of the
non-food feed stocks that are categorized as second generation
middle class people in America could afford. During that period
bio fuels. The agricultural residues such as corn stover, wheat
ethanol was emerged as a fuel, but the cheap gasoline price
straw and sugar cane bagasse, forest residues such as saw dust,
abandoned that. Now the gasoline price has exceeded the etha-
industry wastes such as black liquor form the paper industry and
nol price. The major feed stocks for bio ethanol production are
municipal waste provide promising substitute for edible feed
corn, sugarcane, sugar beet and wheat. Brazil and United States
stocks for bio ethanol. All these type of residues and wasted are
are branded as the leading countries in bio ethanol production
known as lignocellulose bio mass. Since lignocellulose contain
and China, France and India also have industrial scale bio etha-
cellulose which comprises of glucose, fermentable sugars can
nol productions. The main feed stock used in Brazil is sugar cane
be obtained from them. The production process of ethanol from
while corn is the main feedstock in United States.
residues and wastes is same as the conventional process. The
only difference is lignocellulose bio ethanol production process
Ethanol (C2H5OH) is obtained by fermentation of glucose (C6H12O6).
includes an extra step as pretreatment.
Glucose is a simple sugar contained greatly in sugar cane, sugar
beet and corn compared to other bio masses. However glucose is
Lignocellulose biomasses are mainly structured with cellulose,
not there as it is; it is in the form of carbohydrate. Carbohydrates
hemicellulose and lignin. Cellulose comprises of glucose where-
are long chains comprises of glucose. Therefore, first of all the
as hemicellulose contains some compounds which can be con-
glucose should be hydrolyzed into fermentable sugars; the
verted into fermentable sugars. The lignin consists of aromatic
process is named as hydrolysis. Then the obtained sugars are
compounds, does not have any sugar component. The lignin in
fermented into ethanol. Ethanol has a long history and has been
the plant cell wall binds cellulose and hemicellulose together,
used as an alcoholic drink. The fuel ethanol is a result of the
creating a potential barrier for extracting of fermentable sugars.
evolution of distillation technology. In order to use ethanol as
Thus a pretreatment is needed forbreak downing lignin while
an additive to gasoline, it should be 100% pure. The reason is
increasing the cellulose and hemicellulose solubility. Therefore
if there is water in ethanol it enhances the molecular polarity
nowadays many methods with chemicals and enzymes have
which may become a problem when ethanol and gasoline are
been developed to find out a suitable, cost effective pretreat-
mixed, as they separate into two phases. Distillation has the
ment method for industrial scale with less impact to the environ-
ability to provide maximum ethanol purity only up to 90-95%.
ment. Now the researches are moving into the third generation
Therefore the dehydration process is used to achieve 100%
bio ethanol production too. Algae will be the feedstock belongs
ethanol.
to third generation. Algae fuels are more beneficial than bio
masses. The high yield, easy adaptability and less land requirement of algae fuel were the reasons for the stepping towards the
third generation. Algae fuels have significant similarities with
Fuel ethanol
production
process from
bio masses
BIO MASS
petroleum, thus these biofuels also known as advance biofuels
HYDROLYSIS
Bio ethanol was emerged as a solution for energy crisis as well
or green hydrocarbons.
as for increasing greenhouse gas emission. Several technological and economical challengers are still remaining which act as
FERMENTATION
hurdles to bring the bio ethanol to the market, especially for
second and third generations. Feedstock cost directly affects the
fuel price. Thus obtaining an economical feedstock is the key
DISTILLATION
DEHYDRATION
challenge to next generation of biofuels.
VIVEKA EDUSSURIYA
Department of Chemical & Process Engineering
(Fourth Year)
Gauge Newsletter
University of Peradeniya
35