Bio-ethanol production

Bio-ethanol production
Bio-Ethanol is produced from the
fermentation of sugars obtained from
biomass.
Fermentation is anaerobic biological process
in which sugars are converted to alcohol by
the action of microorganisms, usually yeast.
The resulting alcohol is bioethanol.
The value of any particular type of biomass as
a feedstock for fermentation depends on the
ease with which can be converted to sugars
 Bio-ethanol…
Feedstock used for the production of bio ethanol that contains ‘
– Sucrose eg sugar cane, sugar beet
– Starch e.g corn, wheat
– Lignocellulose eg sugar cane bagasse, wood straw
 It is possible that wood, straw and household wastes may be
economically converted to bioethanol
 About 60% of global bioethanol production comes from sugarcane
and 40% from other crops.

70% of world Ethanol production

World Leader Brazil US

Ethanol producers

Sugar cane Ethanol Corn Ethanol

Ethanol production
Bioethanol from sugarcane
Bioethanol …..
 Bioethanol…
• Processes that are common to both sugar and ethanol
processing: Reception, preparation and sugar
extraction
• Upon arrival sugarcane will be cleaned using dry
cleaning system to prevent sugar losses
• => mineral and vegetable impurities will be removed
• Then the sugarcane is chopped
• juice will be extracted using mills=> sugarcane is
pressed=> the juice and bagasse will be separated
• The juice will pass on a screen to separate any dragged
fiber with the juice
 Bioethanol…
• Juice treatment
• How can we treat juice? What impurities does
the juice have?
 Ethanol….
• Juice produced in the mills contains several
impurities (minerals, salts, organic acids, dirt and
fine fiber particles)
• a physicochemical treatment
– separation of fibers and sand in screens,
– heating of juice from 30 to 70 oC,
– addition of lime along with a second heating, up to
105 oC,
– removal of air (flash),
– addition of a flocculants polymer and final removal of
impurities through a clarification process.
 Ethanol…

Juice treatment for

Ethanol Production
 Ethanol…
Juice Concentration
Clarified juice must be concentrated to
achieve adequate sugar concentration for
fermentation
When mixing molasses from sugar factory
can’t achieve the required sugar
concentration=> evaporators will be used
 Ethanol….
Fermentation
A fed-batch fermentation process with cells recycle;
yeast (Saccharomyces cerevisiae) recovered from a previous
fermentation batch is fed to the fermentor prior to the juice
After addition of the juice, the mixture remains in the reactor for a
few hours, and the sugars are fermented
The process takes place at temperatures around 30–34 oC and
produces wine with relatively low ethanol content due to yeast
inhibition related to substrate, product and temperature
The fermented liquor (wine) produced in the fermentation is
centrifuged to remove yeast cells, which undergo a chemical
treatment using water and sulfuric acid to reduce bacterial
contamination.
Yeast cells are used on the next batch, while centrifuged wine is
sent to distillation.
continuous fermentation=>based on the use of 3–5 reactors in
series, using the same system for cells recycle
described above.
 Ethanol….
Distillation
A conventional distillation columns will be used
to get the hydrated ethanol (93wt%)
To use ethanol for a blend it should be
concentrated to 99.3% but at around 95wt%
ethanol makes an azeotrope with water. So
how we can concentrate the ethanol to the
required level?
 Ethanol…
• To make the anhydrous ethanol from hydrated ethanol we can use one
of the following methods
– Azeotropic distillation
cyclohexane is added to an azeotropic column, along with hydrated ethanol,
and it forms a new tertiary heterogeneous azeotrope with ethanol and water.
The azeotrope is removed at the top of the azeotropic column, while
anhydrous ethanol is produced at the bottom.
– Extractive distillation
Monoethyleneglycol added which alters the relative volatility of ethanol and
water, promoting separation of anhydrous ethanol in an extractive column. In
this case the solvent-water mixture is obtained at the bottom of the column.
Anhydrous ethanol is obtained at the top of the extractive column.
– Adsorption on molecular sieves
In the adsorption no chemical solvent is used, but a zeolite bed is responsible
for removal of water from the hydrated ethanol. In this process hydrated
ethanol vapor is fed to the zeolite beds; three beds are usually used, in which
one is regenerating and the other two are removing water, in a cyclic
operation. When hydrated ethanol contacts the zeolites, water molecules are
adsorbed while anhydrous ethanol is obtained at the bottom of the bed.
Production of Ethanol from Molasses
Molasses as being technically the most ideal raw
material in ethanol production compared with other
substrates giving the reason that they do not require
additional preparation.
It contains about 62% of carbohydrates in the form
of 30% un-crystallized sucrose and about 32% of
invert sugar which is a mixture of glucose and
fructose
The most employed microorganism is
Saccharomyces cerevisiae due to its capability to
hydrolyze cane sucrose into glucose and fructose,
two easily assimilable hexoses
 Ethanol from Molasses…..
Although this microorganism has the ability to
grow under anaerobic conditions, small amounts
of oxygen are needed for the synthesis of
substances like fatty acids and sterols.
The oxygen may be supplied through the
addition to the medium of some chemicals like
urea hydrogen peroxide (carbamide peroxide),
which also contributes to the reduction of
bacterial contaminants.
 Ethanol from Molasses…..
Salts and other compounds have negative influence on
the fermentation
To avoid the negative influence of salts and other
compounds on the fermentation conditioning of
molasses addition of different compounds to neutralize
the inhibitory effects of the medium components
In addition, molasses should be supplemented with
nutritional factors promoting the yeast growth.
The addition of a commercial enzymatic complex of
amylases, cellulases and amylopectinases allows the
conversion of non-fermentable substances into
assimilable compounds improving the alcoholic
fermentation
 Bio-Ethanol from Corn
Water
• Dry grid of corn to Enzymes
Ammonia
Ethanol process
– Pretreatment
– Cooking
– Fermentation
– Distillation
 Production of Ethanol from
lignocellulosic biomass
Lignocellulosic complex is the most abundant biopolymer in
the Earth.
It is considered that lignocellulosic biomass comprises about
50% of world biomass
lignocellulosic materials for fuel ethanol production
– crop residues (cane bagasse, corn stover, wheat straw, rice straw,
rice hulls, barley straw, sweet sorghum bagasse, olive stones and
pulp),
– hardwood (aspen, poplar),
– softwood (pine, spruce),
– cellulose wastes (newsprint, waste office paper, recycled paper
sludge),
– herbaceous biomass (alfalfa hay, switchgrass, reed canary grass,
coastal Bermudagrass, thimothy grass), and
– municipal solid wastes (MSW).
 Ethanol from lignocellulse
Steps to produce bioethanol from lignocellulosic
biomass
–Pretreatment of lignocellulosic
biomass
–Detoxification of lignocellulosic
hydrolyzates
–Hydrolysis of cellulose
–Fermentation of biomass hydrolyzates
 Ethanol from lignoce…
1. Pre-treatment of
lignocellulosic
biomass
• This step is the main
challenge
• The lignocellulosic
complex is made up of
a matrix of cellulose
and lignin bound by
hemicellulose chains.
 Ethanol from lignoce…
For the pretreatment of lignocellulosics, several
physical, physical–chemical, chemical and biological
processes can be used
One of the main problems during the pretreatment
and hydrolysis of biomass is the variability in the
content of lignin and hemicellulose.
This variability depends on factors as the type of plant
from which the biomass is obtained, crop age, method
of harvesting, etc. =>No one of the pretreatment
methods could be applied in a generic way for many
different feedstocks
 Ethanol from lignoce…
Physical methods
– chipping, grinding and milling to reduce cellulose
crystallinity.
Physical–chemical methods
– Eg. The steam explosion
– During this process, the use of saturated steam at high
pressure causes autohydrolysis reactions in which
part of the hemicellulose and lignin are converted into
soluble olygomers.
– The factors affecting steam explosion pretreatment
are residence time, temperature, chip size and
moisture content.
 Ethanol from lignoce…
Chemical methods
– Chemical pretreatments employ different
chemical agents as ozone, acids, alkalis, peroxide
and organic solvents.
– Inorganic acids as H2SO4 and HCl have been
preferably used for biomass pretreatment.
– Hydrolysis with dilute sulfuric acid has been
successfully developed given that high reaction
rates can be achieved improving significantly the
subsequent process of cellulose hydrolysis.
 Ethanol from lignoce…
Biological methods
– Biological pretreatment has low energy
requirements and mild environmental conditions.
– However, most of these processes are too slow
limiting its application at industrial level
 Ethanol from lignoce…
2. Detoxification of lignocellulosic hydrolyzates
During pretreatment and hydrolysis of lignocellulosic biomass,
a great amount of compounds that can seriously inhibit the
subsequent fermentation are formed in addition to
fermentable sugars.
Inhibitory substances are generated as a result of the
hydrolysis of the extractive components, organic and sugar
acids esterified to hemicellulose (acetic, formic, glucuronic,
galacturonic), and solubilized phenolic derivatives.
In the same way, inhibitors are produced from the degradation
products of soluble sugars (furfural, HMF) and lignin
(cinnamaldehyde, p-hydroxybenzaldehyde, syringaldehyde),
and as a consequence of corrosion (metal ions)
Detoxification methods can be physical, chemical or biological.
 Ethanol from lignoce…
Alkali treatment is considered one of the best
detoxification methods. By this method, furaldehydes
and phenolic compounds are mainly removed leading
to great improvement in fermentability, especially in
the case of dilute-acid hydrolyzates
Other very diverse detoxification methods have been
proposed as: neutralization with lime followed by the
addition of activated carbon and filtration for acetic
acid removal; partial removal of acetic acid, furfural
and soluble lignin by molecular sieves; vapor stripping
for removal of volatile inhibitors ; and adsorption using
activated carbon, diatomite, bentonite and zeolite
after neutralization or over liming
 Ethanol from lignoce…
3. Hydrolysis of cellulose
For fermentation of lignocellulosic materials,
cellulose should be degraded into glucose
(saccharification) using acids or enzymes
4. Fermentation of biomass hydrolyzates
 Why Ethanol?
Bioethanol can be used directly in cars designed
to run pure ethanol (Anhydrous ethanol ) or
blended with gasoline to make “gasohol”.
No engine modification is typically needed to use
the blend.
Ethanol can be used as an octane boosting,
pollution reducing additive in unleaded gasoline.
We can use a wide variety of raw materials
Environmentally sustainable.
 Sucrose containing materials are
more cost effective
The use of sucrose-containing materials as
cane molasses allows producing ethanol with
the lowest costs compared to the starchy
materials (mostly grains).
The ethanol yield from corn is higher than that
from sugar cane but the lower annual yield of
corn per cultivated hectare makes it necessary
to use larger cropping areas
 Why lignocellulose biomass?
The availability and low cost of a wide range of
lignocellulosic materials
Will have a large contribution to the reduction
of greenhouse gas emissions worldwide
Questions?
Thank You!