Cellulolysis Process Overview

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Cellulolysis Process Overview Summary found at
http//en.wikipedia.org/wiki/Cellulosic_ethanol
Expose Cellulose for Hydrolysis
Break down hemicellulose Cellulose to Sugars
Convert Sugars to alcohol
Separate alcohol from water
Harvest
Chopping or Baling
Chemical Hydrolysis
Pretreatment
Storage
Fermentation
Distillation
OR
OR
Enzymatic Hydrolysis
Combined Storage-Pretreatment (silos, piles,
agribags, dry storage)
Combined Hydrolysis Fermentation
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Cellulolysis Pretreatment Explanations

• 1) Acid Hydrolysis
• 2) Dilute Acid - Steam Explosion
• - feedstock is impregnated with acid (H2S04
  sulfuric acid) H2SO4 is used because of its low
  cost
• - feedstock is then processed in a steam
  explosion reactor
• time in the reactor (residence time) and
  temperature levels of the reactor seem to
  determine the ethanol yield
• down the line
• - A good sample experiment of this using corn
  stover is at http//www.nrel.gov/docs/gen/fy03/32
  119.pdf
• 2b How is sulfuric acid made answer below
  from http//wiki.answers.com/Q/How_is_sulfuric_aci
  d_made
• There are two main ways
• 1. Step 1- Sulfur is burned to produce sulfur
  dioxide. S(solid) O2(gas) ? SO2(gas)
• Step 2- This is then oxidised to sulfur trioxide
  using oxygen in the presence of a vanadium(V)
  oxide catalyst. 2 SO2 O2(g) ? 2 SO3(g) (in
  presence of V2O5)
• Step 3.a-The sulfur trioxide is treated with
  water (usually as 97-98 H2SO4 containing 2-3
  water) to produce 98-99 sulfuric acid. SO3(g)
  H2O(i.e. water) ? H2SO4(liquid) Hey Presto!
• Or, way 2.The SO3, produced at step 2 above,
  can be processed in an alternative way. i.e.
• Step 3.b. The SO3 can be absorbed into H2SO4
  (concentrated sulfuric acid!) to produce oleum
  (H2S2O7) H2SO4(l) SO3 ? H2S2O7(l)
• Step 4- Oleum can then be reacted with water to
  form more concentrated H2SO4. H2S2O7(l) H2O
  ? 2 H2SO4(l)

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Cellulolysis Pretreatment Explanations Continued
3) Ammonia Fiber Expansion Liquid ammonia is
used to pretreat and explode biomass - Ammonia is
recycled - Process is run at 60-100C, 20-80
moisture, and biomas ration is .5 to 1.3-1.0 -
see http//www1.eere.energy.gov/biomass/pdfs/34861
.pdf - Ammonia Fiber Expansion (AFEX) is a
promising pretreatment with no inhibitory effect
in resulting hydrolysate (meaning it leaves no
impurities that hinder Fermentation) 4) Lime
Pretreatment - see http//www1.eere.energy.gov/bio
mass/pdfs/34861.pdf - Takes 1 to 2 months looks
to be done in a pile or bunker 5) Flowthrough
Pretreatment - see http//www1.eere.energy.gov/bio
mass/pdfs/34861.pdf 6) Controlled PH
Pretreatment - see http//www1.eere.energy.gov/bio
mass/pdfs/34861.pdf 7) Ozone Pretreatment 8)
Alkaline Wet Oxidation
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Cellulolysis Chemical (Acid) Hydrolysis
Explanations

• Dilute Acid
• - process uses more heat and pressure
• - sugar degradation is a problem and can lower
  sugar yield and toxins can be left over that
  hamper
• fermentation
• - uses 1 sulfuric acid solution in a continuous
  flow reactor at 215C
• - Sugar conversion efficiency is 50
• - Two step process, since hemicellulose (5
  carbon sugar) degrades faster than 6 carbon
  sugars (Cellulose)
• a) mild conditions to recover 5 carbon sugars
• b) harsher process to recover 6 carbon sugars
• - both resulting hydrolyzed solutions are then
  fermented to alcohol. Lime is used to neutralize
  acids
• prior to fermentation, and
  leftover lignin is used to as boiler fuel or to
  make steam to produce
• electricity
• 2) Concentrated Acid
• - process uses lower heat and pressure
• - uses concentrated sulfuric acid and then
  dilution with water to dissolve and hydrolyze
  material into sugar
• - process converts cellulose to glucose, and
  hemicellulose to 5 carbon sugars
• - acid is recycled in the process
• - Two step process

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Cellulolysis Enzymatic Hydrolysis Explanations
Enzymatic Hydrolysis In this process, enzymes are
used to hydrolyze the cellulose (C6 Sugar) and
hemicellulose (C5 sugars) Trichoderma reesei
produces cellulase enzymes needed to convert
cellulose and hemicellulose to sugars (glucose
molecules) Enzyme Producers Iogen -
http//www.iogen.ca/ Genecor - http//www.genencor
.com/wps/wcm/connect/genencor/genencor Novozymes
- http//www.novozymes.com/en Dyadic
International Inc - http//www.dyadic.com/wt/home
Verenium - http//www.verenium.com/ Direct
Microbial Conversion In this process, ethanol and
required enzymes are produced from the same
microorganism
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Combined Hydrolysis Fermentation
Some bacteria have been found to convert
cellulose directly to ethanol. Examples of these
bacteria are Clostridium thermocellum (C.
thermocellum) this bacterium will convert
cellulose directly to ethanol, but has some other
byproducts that can reduce efficiency during
fermentation
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Cellulolysis Fermentation Process Explanations
Do C5 and C6 sugars need to be fermented
separately? Zymomonas mobilis (Z. mobilis)
bacterium that converts sugars to pyruvate, which
is then fermented to ethanol
and carbon dioxide. NREL has
developed a version that leads to more efficient
fermentation of both C5 and C6
sugars. Arkenol will be using the NREL
version. Saccharomyces cerevisiae bakers yeast
used in brewery industry to produce ethanol from
C6 sugars Escherichia coli (E. coli) uses
mixed-acid fermentation in anaerobic conditions,
producing lactate, succinate, ethanol,
acetate and carbon dioxide
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Cellulolysis Distillation Process Explanations
This process of separating alcohol from water is
that same as is used in making corn ethanol in
simplistic terms, the beer is heated to the
point where the Alcohol (which boils at a lower
temperature than water evaporates up leaving
water behind. The alcohol vapor is contained and
cooled which turns it back to a liquid, with this
liquid being mainly alcohol (some water will/may
remain, so to purify the alcohol it may be run
thru the distillation system repeatedly until the
desired of alcohol is achieved.
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Cellulolysis Process Definitions
Assistance with definitions found at
http//dictionary.reference.com/
Pretreatment separation of 4 components of
biomass hemicellulose, cellulose, lignin, and
extractives so that they can then
be broken down into their sugar
components Saccharification - the process of
breaking a complex carbohydrate (as starch or
cellulose) into simple sugars Hydrolyze to
subject to hydrolysis, which is the breaking down
of a chemical compound into two or more simpler
compounds by reacting with water. The proteins,
fats, and complex carbohydrates in food are
broken down in the body by hydrolysis that is
catalyzed by enzymes in the digestive tract
Hemicellulose - (5 carbon sugar) - any of a
group of gummy polysaccharides, intermediate in
complexity between sugar and cellulose,
that hydrolyze to monosaccharides more readily
than cellulose Cellulose - (6 carbon sugar) - a
polysaccharide(C6H10O5) of glucose units that
constitutes the chief part of the cell walls of
plants, occurs naturally in
such fibrous products as cotton andkapok, and is
the raw material of many manufactured goods
(as paper, rayon, and cellophane)
Lignin - A complex polymer, the chief
noncarbohydrate constituent of wood, that binds
to cellulose fibers and hardens and
strengthens the cell walls of plants xylose
(C5H10O5) 5 carbon sugar (C5 sugar) derrived
from hemicellulose arabinose 5 carbon sugar
(C5 sugar) derrived from hemicellulose hexoses
6 carbon sugars (C6 sugars) Glucose (C6H12O6)
6 carbon sugar (C6 sugar) derrived from
cellulose Mannose (C6H12O6) 6 carbon sugar (C6
sugar) Galactose (C6H12O6) 6 carbon sugar (C6
sugar) that is derrived from hemicellulose
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Gasification Process Overview
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My Fantasy Local Cellulosic Ethanol then Pellet
Production
Fuel to sell at local gas station
Home heat fuel to sell at local stores
Transport feedstock to local plant
Central Local Processing
Drying of Material
Harvest
Ethanol Production
Pellet Pressing
Clean Energy Sources
Electric and pellet heat sources for distillation
and drying and cooling