good morning now we will start discussion
on a new module energy production from organic
wastes through fermentation we know that fermentation
is a metabolic process in which sugar is converted
to acids gases or alcohol basically ethanol
and butanol are produced in this suit already
we have discussed in the previous module on
anaerobic digestion organic compounds are
converted to low molecular weight organic
acids through fermentation and which further
converted to methane through methanogenesis
steps so in this module we will be concentrated
basically on the alcohol production from the
organic feed stocks so the contents of this
module will be fermentation and energy production
production of ethanol from three different
feed stocks and preprocessing steps production
of ethanol from starchy crops then production
of ethanol from lingo cellulosic biomass which
will include pretreatment of lingo cellulosic
biomass detoxification and hydrolysis and
then fermentation microorganisms and product
recovery than ethanol production through gasification
route that means from syngas to ethanol
and then finally butanol production from l
c b that is lingo cellulosic biomass now we
will at first see fermentations and energy
productions so if we use organic wastes or
biomass for energy productions we have some
options one is directly through fermentation
we can get ethanol and butanol we can make
syngas after drying this waste and then gasification
then we will get syngas and syngas can further
be converted to ethanol through fermentation
process and already we have discussed that
anaerobic digestion in which fermentation
process converts the organic compounds to
acids and then which is further converted
to methane so we have not concentrating here
we will be concentrating basically ethanol
and butanol production through these two routes
now ethanol and butanol which is produced
through these routes can be used in various
applications but as a fuel these compounds
can also be used because the heating value
of ethanol is twenty six point eight mega
joule per kg which is significant amount and
for butanol it is thirty two point five mega
joule per kg whereas the gasoline is forty
two point nine mega joule per kg so this two
can be blended with gasoline and can be used
as a fuel now we will see the methanol fermentation
so what is methanol fermentation it is a series
of biological or chemical reactions for converting
sugars to ethanol in presence of suitable
microorganisms and then basically what type
of reactions takes place in this case sugar
is converted to ethanol and carbon dioxide
yeast is normally used for hexose there are
two types of sugars may be used pentose and
hexose if hexose is used then yeast is used
and this reaction is represents the ethanol
fermentation reaction so how this higher form
this will come that sugar will come sugar
can come from three types of sources that
is sugar crops starchy crops and lingo cellulosic
biomass so these three types of feed stocks
we will be using separately and con discuss
separately how to produce sugar and then the
ethanol and sugars may contains six carbons
and five carbons just we have discussed then
production of ethanol from three different
feed stocks three types of different feed
stocks basically
so sugar crops starchy crops and lingo cellulosic
biomass so whatever may be the type of feed
stocks if we want to produce ethanol our first
step will be preprocessing then we will go
for fermentation that is the heart of the
reactions or the process so the after fermentation
the products which will form that has to be
purified and the distillation and followed
by dehydration is normally followed for the
production of ethanol from this feed stocks
so if sugar is there the preprocessing steps
will be very simple then the starchy crops
it will be relatively complex and thus lingo
cellulosic more complex more steps are required
so after fermentation ethanol production the
concentration here is around four to ten percent
distillation gives us ethanol with ninety
five to ninety six percent purity but we need
ninety nine point five percent purity for
using in blend of gasoline and etha ethanol
so some another step that is dehydration step
is added for the further purification of this
ethanol particularly to reduce the water content
in the methanol which is produced through
the distillation process so we will discuss
later on the detail of hy dehydration methods
so ultimately we will get the ethanol and
other some bi products we will get so this
is the process flow sheets now we will consider
on preprocessing steps for different types
of feed stocks so this things already we have
discussed so if it is a sugar crops then sugar
sugar crops to sugar then sugar to fermentation
simplest method then it is starchy crops we
will get starch from the starchy crops then
starch has to be hydrolyzed to convert it
into sugar
then sugar will be further fermented if it
is a lingo cellulosic biomass pretreatment
is must pretreatment then it will give us
cellulose and hemi cellulose and then cellulose
hemi cellulose will be hydrolyzed to get sugars
and then that will be the fermentation steps
so the preprocessing steps is varying depending
on the feed stocks and sugar crops is less
than the starchy crops and then the lingo
cellulosic biomass now we will concentrate
on the production of ethanol from to starchy
crops so one example is your corns so in this
case the corn it contains germ it contains
gluten it contains starch and it concerns
bran so these are the composition of the corn
so if we want to use these feed stocks for
the production of ethanol there are basically
two routes one is wet process another is dry
process in the wet process before fermentation
different fragments have been separated different
parts have been separated from the corn kernel
and then in the dry process the separation
does not take place at the initial stage later
on the product recovery takes place so at
first we will see the wet process so in the
wet process the cleaning and steeping of grains
is the first step so in this case this is
cleaned and this is put in dilute sulphuric
acid solution for a longer time within this
period the different parts are more becomes
more separable and then after that steeping
it goes through the grinding step so grinding
step helps to get the jumps out from other
materials
so germ without without any further fragmentations
in the germ so that is the grinding step and
then third step is washing and filtering so
after getting out the germs so watching and
filtering will help to get the fiber out so
once the fiber is out then all will be in
this phase that is solution phase so gluten
starch etcetera will be there so gluten is
full of protein and germ is full of oil and
so starch and gluten that are separated in
the gluten separation steps there are number
of steps for this separation after the separation
of gluten the remaining solution will be containing
starch and that starts has to be converted
to sugar and that process is called cooking
so this cooking means some heat is applied
as well as some enzymes are added for the
conversion of starch to sugar and once sugar
is produced through this cooking steps then
that sugar is sent for the fermentation that
it is the step number six
so once the fermentation is over then we have
to go for distillations and dehydrations we
will get the ethanol and we we can get some
here glucose and some emissions and wastewater
etcetera so these are the flow sheets for
the production of ethanol through wet process
so some highlights are that grinding is used
to liberate intact germ from the kernel germ
separation is done by a series of hydro cyclones
and the high oil content of the germ imparts
low density so it comes off so and it is separated
and other things the starch and ah etcetera
are are available in the lower part and then
fiber separation consists of four steps that
is initial screening of coarse fibers than
a milling or grinding step to liberate and
disperse all the starch and gluten from the
remaining fiber and then another washing step
and dewatering and drying step
so these are the steps through which the fibers
are separated and after the fiber removal
starch protein and miscellaneous soluble components
these are present in the solution and gluten
separation takes place and then finally ah
cooking process starts and that cooking alpha
amylase enzyme is added for the conversion
of starch to sugar the dry process does not
separate the different components of the corns
at the fast step before fermentation so it
after cleaning it goes for milling so after
milling we get the floor and that is liquefied
we add water here to make a slurry and that
is liquefaction then it is going for saccharifications
the liquids slurry is heated and ah enzymes
are added to convert the starch to sugar so
then sugar is going for fermentation then
fermentation will give some fermented product
and those products will be separated through
distillations and dehydration
so distillation will give us eternal and remaining
products go for co product processing that
have some commercial value on can be used
for if other applications like say animal
feed and other co products production so here
the enzymes are like gluco amylase which converts
liquefied starch to fermentable sugars so
this is the dry process for the production
of ethanol from starchy materials now we will
see the flow sheets for the production of
ethanol from the lingo cellulosic biomass
as you have discussed that when the material
is lingo cellulosic biomass it will be requiring
stringent preprocessing step that is pretreatment
so lingo cellulosic biomass and waste after
drying and grinding it will go for slurry
formation and then that is ten to fifteen
percent dry solids will be there then it will
go for pretreatment step
so that pretrea pretreatment can be done by
physical means by chemical means or by biological
means and then after pretreatment we will
be getting the cellulose and hemi cellulose
lignin will be separated from this and that
cellulose and hemi cellulose will go for detoxifications
and hydrolysis and then it will be converted
to sugar and then it will go for fermentation
for the production of ethanol and once fermentation
is over then we will get different products
that has to be recovered that can give us
ethanol solid residue and waste water the
ethanol is our major concern here so in this
process water is used for the slide formation
and fermenting micros are added hear that
is fermentations ah micros are added so now
we will see different types of organic feed
stocks are waste which are available for this
production of ethanol
so here agricultural residues and agro waste
municipal solid waste forest biomass and wastes
and industrial wastes and whole plants so
some examples are given here in this slide
now we will discuss thus pretreatment step
so what happens during pretreatment of the
lingo cellulosic biomass if we see the lingo
cellulosic biomass here before pretreatment
so here we are getting lignin we are getting
cellulose we are getting hemi cellulose so
very tightly packed these are very tightly
packed so we have to break it we have to break
it and we have to separate this cellulose
and hemi cellulose from the lignins lignins
are not desirable for the biological activity
so cellulose cellulose is also having some
ah crystalline structure amorphous structure
here amorphous crystalline structure and which
we these are well structured we have to break
the structure of this cellulose and after
pretreatment if we see here the figure the
lignin serving separated the hemi cellulose
are converted to sugar to some extent and
cellulose are broken down into smaller pieces
so altered cellulose so see pretreatments
alters the cellulose converts the hemi cellulose
to some sugar and lignins are also removed
so this is the main job of the pretreatment
process we do not need more glucose from the
ah cellulose or more sugar from the cellulose
in this step so this pretreatment step we
need the breakdown of these the regular structure
of the cellulose and altered cellu cellulose
is formed
so altered cellulose and simple sugar from
hemi cellulose both are produced during pretreatment
steps so this is the main objective of this
pre pretreatment step so here the the macroscopic
some microscopic and microscopic structure
of the biomass to make it make easily accessible
to the microorganisms and enzymes so if this
is the role of the pretreatment step how can
we define the performance of this pretreatment
step or the energy efficiency of any pretreatment
step so that is defined as efficiency equal
to t s y by t e c what is t s y t s y is the
total soluble sugar yield how much total solve
sugar we are getting in kg and total energy
consumptions during the free treatment in
mega joule
so kg per mega joule that will be the efficiency
of this pretreatment process so during pretreatment
process what are the favorable characteristics
let us see those things so obtainment of cellulose
with high digestibility so our main objective
is to get more cellulose and not to convert
cellulose into sugar in this step our objective
to remove all lignins ok so no one little
degradation of sugars and sugar derivative
products sugar has to be remained here in
significant amount that will be going through
the fermentation otherwise we will be losing
some sugar avoiding distractions of hemi cellulose
and cellulose we cannot allow the destructions
of this hemi cellulose and cellulose in this
step and production of minimum amount of toxic
compounds
so toxic compounds are also formed during
pretreatment steps because the lignins are
present so some phenolics compounds some organic
acids will also be produced those compounds
harms the growth of the microorganism so that
is not desirable so our ah our can condition
should be such that that will not favor this
toxic formation then capable of operating
in reasonable size and moderate cost reactors
ok no production of solid waste residues we
do need any solidate residues in this step
and effectiveness at low moisture content
and recovery of high amounts of carbohydrates
so we have to recover high amounts of carbohydrates
through this process and ah fermentation compatibility
then minimum heat and power requirements so
these are some characteristics of this process
now we will see the comparison of different
types of pretreatment process so one is physical
process chemical process and physicochemical
and biological process system four types of
processes have been classified here so physical
process means cutting and grinding chemical
process means acid treatment and alkali treatment
and this is physicochemical process means
steam expressions ammonia fiber exploration
and ammonia recycling percolations and soaking
aqueous ammonia wet oxidation carbon dioxide
expressions so and biological methods we use
some white rot brown rot and soft rot fungi
those are used and brown rot attack cellulose
while white and soft rots attack both cellulose
and lignin
so these are the ah type of pretreatment process
which are used for the pretreatment of the
lingo cellulosic biomass and basically to
get the sugar from it cellulose and hemi cellulose
so out of this processes chemical process
is more suitable which gives in which increases
the delignification decreases the degree of
polymerization and crystallization of cellulose
associated with its swelling and and porosity
growth and then acid pretreatments solubilizes
the hemi cellulosic fractions of the biomass
and makes the cellulose more accessible to
the enzymes so these are the characteristics
of these and chemical process is more suitable
now we will see the detoxification
so just now we have seen that in your pretreatment
method the lignin compounds are removed so
during this those some amount of lignin can
also produce different types of compounds
like say furfurals and levulinic acid formic
acids and acetic acid all those things are
formed in this step so we can get these compounds
which harms the microbial growth i will as
we we have already discussed and biological
physical and chemical methods are used for
the removal of these toxic compounds or inhibitors
so how this the chemical detoxification may
be carried out by using sodium dithionite
sodium sulphate and sodium borohydride so
this three compounds can be used during pretreatment
steps so they so that detoxification compounds
will not be available in the product
then we are going to discuss on hydrolysis
so hydrolysis once the pretreatment is over
then the objective of the pretreatment is
what to breakdown the lingo cellulosic biomass
in to lignin cell cellulose and hemi cellulose
say hemi cellulose so next is this is removed
this is removed so after this removal we will
consider these two and hydrolysis that will
give us sugar that will give us sugar so this
is the part the hydrolysis the major portions
of cellulose and hemi cellulose are converted
to sugar so what is this cellulose and hemi
cellulose this is having glucan and this having
xylan what is glucan and xylan glucan is the
polysaccharide and xylan is also polysaccharide
the pentose this monomer contents five carbon
sugar this is six carbon sugar so glucan and
xylan respectively
so digestibility of both glucan and xylan
can be determined from the yield of their
respective monomer and disaccharides what
are the disaccharides one is your cellobiose
another is your xylobiose so xy glucan we
will give us one is monosaccharide another
is disaccharide so monosaccharide is glucose
and disaccharide is cellobiose and what xylan
will give us xylan will give us xylose and
xylobiose it will give us xylose plus xylobiose
it will give us xylose and xylobiose so this
monosaccharide disaccharide so depending upon
the amount of monosaccharide and disaccharide
we can get the digestibility of glucan and
digestibility of xylan as per the expression
given here and this is reported here in this
journal into two thousand eight
so digestibility of glucan is equal to amount
of glucose plus one point zero five three
into amount of cellubiose in gram unit divided
by one point one one one into amount of glucan
in gram into hundred so this is digester how
much glucan was present out of those glucan
how much glucose and how much cellubiose has
been produced so this ratio this this express
gives us the digestibility similarly for xylan
amount of xylose plus one point zero six four
into amount of xylobiose divided by one point
one three six amount of xylan into hundred
this gives us the digestibility of the xylan
now total sugar conversions so how much total
sugar is converted we are interested to know
that so in that case glucose yield plus xylose
yield glucose yield plus yield divided by
theoretical glucose yield plus theoretical
xylose yield
what do we mean by theoretical glucose yield
and theoretical xylose yield that means if
we know the glucan content and if we know
the xylan content then we can get the theoretical
yield of glucose and theoretical yield of
xylan because the relationship is that the
theoretical glucose yield is equal to w in
to glucan content divided by zero point nine
and theoretical xylan xylose yield is equal
to w into xylan content divided by zero point
eight eight so if we know the glucose yield
that is g is the glucose concentration in
hydrolysis liquid that is glucosely glu glucose
yield and then zero zereo or o is the initial
glucose concentration initial glucose concentration
in this case is how much zero be because hydrolysis
is taking place no glucose was there so this
minus this into v be the initial volume of
the biomass slurry that is m l and then x
and x o x is what is the xylose concentration
is hydrolysis liquid and x o is the initial
xylose concentration
so what is the initial xylan concentration
in this case there is also zero so we will
be putting this value if we get the analysis
of the solution after this hydrolysis we will
get the value of g we will get the value of
x and then we will put here and w if we know
w is the initial dry weight of biomass then
w into glucan content and xylan content also
we have to know of this biomass so then or
the waste so glucan content into w by zero
point nine plus glu xylan content into w by
zero point eight eight so that will be the
theoretical glucan and xylan yield and then
this is this in the nominator this is glucose
yield plus xylose yield so as a whole we will
be getting the total sugar conversion so after
this in this part of this module so rest part
we will discuss in the next part of this module
thank you very much for your patience
