Environmental Engineering Reference
In-Depth Information
Table 2.2
The feed stock
types with their examples
used for biodiesel production
Feed stock type
Examples
Plant oils
Cottonseed, jatropha oil, soya bean
Animal fats
Tallow, lard, grease
Some of the advantages of biodiesel are that it is a renewable energy source, can de-
compose easily under natural conditions, has high combustible value, is safe, easily
transportable and less toxic as it has less sulphur compounds in it.
The disadvantages include high viscosity, high surface stress, easily subjected
to oxidation and expensive raw material used for its production (Wang et al.
2006
).
3.1.1
Feed Stocks Used for Bio-diesel Production
Biodiesel can be produced by using various feed stocks. The main biodiesel feed
stocks are classified into three types; plant oils, animal fats and waste cooking oils
with industrial wastes. Table
2.2
presents some examples of plant oils and animal
fats used in this connection. Each country develops feed stock for biodiesel produc-
tion in accordance with their geographical conditions. The United States generally
uses soya bean which is genetically modified while Canada and other European
countries use rapeseed to produce biodiesel. Indonesia and Malaysia own plentiful
palm oil so they use it for biodiesel formation (Vyas et al.
2010
).
China is a big agricultural country because of which it faces a lot of problems
regarding food supply. In order to produce biodiesel they use a principle by which
they never get to compete with food grains as they use waste cooking oil for bio-
diesel production.
3.1.2
Bio-diesel Production via Trans-esterification
The main chemical composition of animal fats along with vegetable oils is triglyc-
erides. The industrial method used for the production of biodiesel is trans esterifi-
cation also called alcoholysis (Wang et al.
2006
). Trans esterification is a process
which involves a reaction of an oil or fat with an alcohol (with or without using a
catalyst) to produce esters and glycerol. This reaction is extremely reversible so
additional amount of alcohol is used to shift equilibrium towards the product pro-
duction side (Fukuda et al.
2001
).
Jatropha
is a good source of biodiesel formation
as it grows on waste land with really less amount of water and minimum need of
fertilizer. This oil is non-edible because of toxic phorbol esters (Tan et al.
2010
).
This reaction takes place in three steps. These three steps are shown in Fig.
2.1
. It
involves the alteration of triglycerides as a result of which diglycerides are formed,
which is trailed by transformation of glycerol through various high glycerides. The
whole process yields one methyl ester molecule from each glyceride at every stage.
This reaction proceeds by mixing the reactant and it may accelerate with the pres-
ence of a catalyst (Fukuda et al.
2001
).
