Environmental Engineering Reference
In-Depth Information
dollars per bushel, which is extremely high (Luque et al.
2010
). The prices of
corn will also vary in various places due to shipping expenses. USA bioethanol
manufacture is 1.1, which is visibly less than the percentage of 3.7 for bioetha-
nol produced in Brazil using sugar cane (De Oliveira et al.
2005
). Other reasons
for the high cost of starch based bioethanol are that the yeast
Saccharomyces
cerevisiae
is not able to utilize starch, so large amount of amylytic enzymes are
needed and the starchy material is essentially cooked at a quite high temperature
to acquire a great bioethanol harvest. The two-step enzymatic hydrolysis of corn
meal at a lower temperature yields bioethanol of more than 80 % just after 4 h
(Mojovic et al.
2006
).
c.
Ligno cellulosic biomass
The chief structure of all lignocellulosic biomass is: cellulose, hemicelluloses
and lignin. This feedstock is used for bioethanol fuel production since it is the
most abundant resource all around the globe (Luque et al.
2010
). Lignocellu-
losic biomass could go up to 442 billion/year. The entire possible bioethanol
making from crop left over and crop wastes is 491 billion/year, which is 16
times greater than the present world bioethanol production (Karimi et al.
2006
).
The highly overflowing lignocellulosic waste material in the world is rice straw.
It has the potential to produce about 205 billion bio-ethanol (Hamelinck et al.
2005
). Lignocellulosic perennial crops are a good feedstock as they give exces-
sive yield, least expenses, worthy suitability for low quality land, and great envi-
ronmental resistance. Pine has the highest collective sugar content, involving
the extreme potential of bioethanol production. The lignin content is about 27 %
for most feed stock while grasses contain visibly lesser amount and thus result
in less electricity production (Hamelinck et al.
2005
). The bioethanol formed
using lignocellulosic materials has a moderately greater cost, based on the chief
encounters and at hand technologies, such as high price of the hydrolysis process
(Dhavala et al.
2006
). The feedstock can signify 440 % of all process charges;
a money-making biomass-to-bioethanol process analytically relies on the fast
and effective transformation of the sugars into both cellulose and hemicellulose
portions (Hamelinck et al.
2005
). Lignin fermentation, which is coproduced in
bioethanol prepared from lignocellulose, can actually produce 458 terra-watt-
hours of current and 2.6 EJ of steam unit (Weber et al.
2010
).
ii.
Thermochemical method of bioethanol production:
Two leading methods for bioethanol production, which use thermochemical
reactions in their processes are:
a.
Hybrid biological and thermochemical system
In this process cellulosic biomass is first thermochemically converted in gas
phase and the synthesis is bubbled through specifically aimed fermenters
(Dhavala et al.
2006
). Also a microorganism with the ability of converting syn-
gas is present in the fermentation containers thus permitting bioethanol to get
fermented (Jansson et al.
2009
).
