Transcript Slide 1

Bio Ethanol as an
alternative source
of energy
Bioethanol is produced from plants
that harness the power of the sun
to convert water and CO2 to sugars
(photosynthesis),
therefore it is a renewable fuel.
R. Shanthini
06 Feb 2010
Bio Ethanol as an
alternative source
of energy
Bioethanol is produced from plants
that harness the power of the sun
to convert water and CO2 to sugars
(photosynthesis),
therefore it is a renewable fuel.
R. Shanthini
06 Feb 2010
Bio Ethanol as an
alternative source
of energy
oxygen in the ethanol molecule
helps in complete combustion,
which means less emissions
R. Shanthini
06 Feb 2010
R. Shanthini
06 Feb 2010
Ethanol is a high-octane fuel, and is widely
used as a blending ingredient in petrol.
A growing number of cars and trucks
designated as FlexFuel Vehicles (FFV)
can use ethanol blended up to
85% with petrol (E85 fuel).
Today there are more than 6 million FFV's on
U.S. roads alone.
R. Shanthini
06 Feb 2010
R. Shanthini
06 Feb 2010
Source: http://www.distill.com/World-Fuel-Ethanol-A&O-2004.html
Bioethanol from simple sugars:
Sugar cane and sugar beets store the energy as
simple sugars, glucose (C6H12O6)
yeast
2 CH3CH2OH + 2 CO2
this simple-looking reaction is a
bioreaction and thus very complex
glucose molecule
R. Shanthini
06 Feb 2010
impure cultures of yeast produce
glycerine and various organic acids
Yeast can be replaced by the
bacterium Zymomonas mobilis
- gives up to 98% yields
- minimal by-products
- simple fermentation requirements
- several-fold the production rates of yeast
Z. mobilis industrial strain CP4,
originating from Brazil,
vigorously fermenting glucose.
Photo courtesy Katherine M. Pappas
R. Shanthini
06 Feb 2010
sugar
cane
yeast
sugar cane crushed and
soluble sugar washed out
fermentation of sugars
produces 5 - 12% ethanol
distilled to concentrate to
80 – 95% ethanol
used as a petrol
replacement
R. Shanthini
06 Feb 2010
sugar cane
residue
CO2
wet
solids
dehydrate to
100% ethanol
used as a petrol
additive
Bioethanol from starch:
Corn, wheat and cassava store the energy as
more complex sugars, called starch
}
starch
(glucose polymer)
α-amylase
dextrins
amyloglucosidase
R. Shanthini
06 Feb 2010
glucose monomer
cassava flour + water +
alpha-amylase enzyme
Liquification
(at 90 – 95 deg C;
pH = 4 - 4.5; 400 rpm)
Saccharification with
glucosidase enzyme
(at 55 - 65 deg C, pH = 4 - 4.5)
Fermentation with
yeast (40 – 50 hrs)
Distillation
R. Shanthini
06 Feb 2010
80-95% ethanol
Cooling (32 deg C)
Dehydration
100% ethanol
Dry grind process
is the most common method used to make fuel
grade ethanol.
The whole corn kernel is ground and converted
into ethanol.
It is relatively cost effective and requires less
equipment, but is not ideal for mass producing.
R. Shanthini
06 Feb 2010
In the wet milling process,
corn is separated into its four basic
components: starch, germ, fiber, and protein,
which are each made into different products.
Advantage: valuable co-products such as
corn oil
Disadvantages: equipment is expensive and
the process uses hazardous sulfur dioxide
R. Shanthini
06 Feb 2010
Bioethanol from Biomass
(except sugars and starches):
Rice straw
Paddy husks
Saw dust
Grasses
Bagasse
R. Shanthini
06 Feb 2010
Bioethanol from Biomass
(except sugars and starches):
Cellulose (40 to 60% by weight of the biomass)
made from the six-carbon sugar, glucose.
Its crystalline structure makes it resistant to
hydrolysis (the chemical reaction that releases simple,
fermentable sugars).
R. Shanthini
06 Feb 2010
Bioethanol from Biomass
(except sugars and starches):
Hemicellulose (20 to 40% by weight) made mainly
from the five-carbon sugar, xylose.
Its relatively easy to hydrolyze hemicellulose into
simple sugars but normal yeast can't ferment xylose.
Celunol Corp. has acquired genetically engineered
E. coli bacteria which can turn almost all xylose into
ethanol.
R. Shanthini
06 Feb 2010
Bioethanol from Biomass
(except sugars and starches):
Lignin (10 to 24% by weight of biomass) is a
complex polymer, which provides structural
integrity in plants.
It remains as residual material after the sugars in
the biomass have been converted to ethanol.
It contains a lot of energy and can be burned to
produce steam and electricity for the biomass-toethanol process.
R. Shanthini
06 Feb 2010
R. Shanthini
06 Feb 2010
Obstacles to commercial production of
cellulosic ethanol:
Accelerating the breakdown of
cellulose fibers
Research on acid / enzymatic hydrolysis is ongoing.
Lignin waste problem
Lignin can fuel Combined Heat and Power plants,
however, CHP plants are expensive.
Use of GM microorganisms
R. Shanthini
06 Feb 2010
Source: DOE's 2006 Annual Energy Outlook
A cellulosic ethanol plant with 50 million
gallons per year capacity and a lignin-fired
CHP will cost about $300 million to build.
A corn ethanol plant with the same capacity
could be built for about $65 million.
R. Shanthini
06 Feb 2010
Source: DOE's 2006 Annual Energy Outlook
Currently, ethanol yields 25% more energy
output than input to produce it.
Research is on for less costly ways of producing
ethanol,
and better ways to blend it with petrol.
R. Shanthini
06 Feb 2010
Is bioethanol a
sustainable energy source?
R. Shanthini
06 Feb 2010
Bioethanol will be used in engines that
convert heat into work
Engines that convert heat
into work are very
inefficient
Take a look at some examples
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06 Feb 2010
Power generation
type
Diesel engine
Unit size
(MW)
Energy
wasted (MW)
10 - 30
7 – 22
Gas Turbine
50 - 100
36 – 78
Steam Turbine
200 - 800
120 – 560
Combined (ST & GT)
300 - 600
150 – 380
Nuclear (BWR & PWR)
500 - 1100
330 – 760
According to the
2nd Law of Thermodynamics
when heat is converted into work,
part of the heat energy must be wasted
R. Shanthini
06 Feb 2010
We throwaway energy that rightfully
belong to the future generations
“Development that meets the
needs of the present without
compromising the ability of future
generations to meet their own
needs."
Our Common Future (1987)
R. Shanthini
06 Feb 2010