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Cellulosic Biomass Chemical Pretreatment

TechnologiesSeptember 5-6, 2007

Keith Pauley

Keith.Pauley@matricresearch.com

800-611-2296

Chemical and Environmental

Technologies

Health and Life Sciences Advanced EngineeringSystems

Life-changing Research and Development

www.matricresearch.com

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MATRIC 2

Industrialization of Cellulosic Ethanol

Five factors control the ability for

cellulosic ethanol to becomeeconomically viable: Process rateslow process step

kinetics requires larger capitalequipment costs

Conversion efficiencypoorutilization of feed materials driveshigher operating costs

Capital equipment costsexoticMOC, high pressure or temperaturematerials drive adversely impactcost of goods produced

Operating costshigh temperaturesor pressures require significantamounts of energy

Product quality/consistencyInconsistency increases the cost ofthe overall process

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MATRIC 3

Cellulosic Ethanol Process

Pretreatment phase, tomake the lignocellulosicmaterial such as woodor straw amenable tohydrolysis

Cellulose hydrolysis(cellulolysis), to breakdown the moleculesinto sugars

Separation of the sugarsolution from theresidual materials,

notably ligninMicrobial fermentationof the sugar solution

Distillation to produce99.5% pure alcohol

Chart courtesy of the National Renewable Energy Lab andappears on the Renewable Fuels Association website.

http://www.ethanolrfa.org/http://www.ethanolrfa.org/

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MATRIC 4

Key Processing Cost Elements

www.everythingbiomass.org

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MATRIC 5

Pretreatment Technologies

Mosieret al., Bioresour. Technol. 2005

Pretreatment technologies aremostly used as precursor toenzymatic hydrolysis Acid Hydrolysis

Steam Explosion

Ammonia Fiber Expansion (AFEX)

Alkaline Wet Oxidation

Ozone Pretreatment (Ozonolysis)

Each method has advantages anddisadvantages No one method is best for all types

of feedstock

Optimum reaction parameters of thevarious pretreatments, liketemperature, pressure, and reactiontime, are specific to each feedstock

High yield of sugars does not alwaysresult in high conversion to ethanol lignocellulosic components or

chemicals used in pretreatment mayform compounds that inhibitfermentation

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MATRIC 6

Acid Hydrolysis

Concentrated or dilute mineralacids penetrate biomass,breaking down hemicelluloseinto monomeric sugars, andremoving part of the lignin First cellulosic pretreatment

technology dating from Germanyin 1898

Reaction is carried out atelevated temperatures

Sulfuric acid is most often used,because it is available at low cost

Low moisture content ispreferred, since less energy isneeded to heat the biomass

http://www1.eere.energy.gov/biomas

s/images/photo_05208_sugar_platform.jpg

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MATRIC 7

Acid Hydrolysis

Advantages good hemicellulose sugar

yields

high cellulose digestibility

removal of hemicellulose andlignin exposes more cellulosefor enzymes to attack

can solubilize heavy metals

that may contaminate the

feedstock

Disadvantages requires downstream

neutralization

some degradation of

hemicellulose sugars lower yield of sugars

may form compounds such asacetic acid and furfural which

inhibit bacteria or yeasts

during fermentation

equipment costs are high reactors must be corrosion

resistant, suitable for high

temperature and pressures

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MATRIC 8

Steam Explosion

Physico-chemical pretreatmentin which biomass is subjected to

high-pressure saturated steam,

followed by rapid

depressurization

Expansion of water vapor exertsforce, causing mechanical

breakdown of biomass

degrades hemicellulose and

lignin, thus increasing the

potential of cellulose hydrolysis

acids or bases may be

incorporated into the steam to

increase hydrolysis

www.biogasol.dk/2me2.htm

http://www.biogasol.dk/2me2.htmhttp://www.biogasol.dk/2me2.htm

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MATRIC 9

Steam Explosion

Advantages economical for hardwoods

effectively hydrolyzes

hemicellulose

promotes delignification enlarges pore size in plant

cells which is beneficial for

subsequent cellulose

hydrolysis

Disadvantages increases crystallinity of

amorphous regions of

cellulose, which decreases

cellulose digestibility

high equipment costs

need for high temperatureand high pressure reactors

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MATRIC 10

Ammonia Fiber Expansion (AFEX)

Physico-chemical pretreatment in which prewetted

lignocellulosic material is treated with liquid

anhydrous ammonia at high temperature and

pressure, then pressure is rapidly released

Created and patented by Michigan State University

In contrast to most pretreatments, AFEX does not

significantly solubilize hemicellulose

Pressures exceeding 12 atm are required for operation at

ambient temperature

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MATRIC 11

Ammonia Fiber Expansion (AFEX)

Advantages Much less sugar degradation

than acid pretreatment

inhibitor formation is verylimited

Fast reaction time (~5min)

Improves hydrolysis rates of

hemicellulose and cellulose in

herbaceous crops and grasses

Ammonia can serve as a

nitrogen source for organisms

downstream Ammonia is all volatilized and

can be recovered as gas

neutralization is notnecessary

Disadvantages High energy utilization to

achieve very high pressures

Relatively new and undeveloped

process

Not proven effective onhardwoods or softwoods

AFEX effectiveness decreases

with increasing lignin content

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MATRIC 12

Alkaline Wet Oxidation

Water, sodium carbonate, and oxygen at elevatedtemperature and pressure interact with biomass bybreaking ester bonds Mechanism believed to be saponification of intermolecular

ester bonds that crosslink hemicelluloses with othercomponents

Porosity of the material is increased due to the removal ofthe crosslinks, so enzymes can attack sugars more easily

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MATRIC 13

Alkaline Wet Oxidation

Advantages Readily oxidizes lignin

Significant decrease incellulose crystallinity

more accessible to enzymes

Low formation of furfural, amicrobial inhibitor oftenproduced by other pretreatmentmethods

Disadvantages Degradation of lignin and

hemicellulose to produce

carboxylic acids

hemicellulose sugarslargely decompose, thus

cannot be converted to

ethanol

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MATRIC 14

Ozone Pretreatment (Ozonolysis)

Ozone acts primarily by degrading lignin, via attack and

cleavage of aromatic ring structuresIn one study using wheat straw, ozone pretreatment removed60% of lignin, which increased enzymatic hydrolysis rates five-fold

Sugimoto et al., Ozone Pretreatment for Ethanol Production Using Lignocellulose Materials, Forestry and

Forest Products Research Institute

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MATRIC 15

Ozone Pretreatment (Ozonolysis)

Advantages Effective delignification Ozone does not form any toxic

compounds that inhibithydrolysis

ozone can be easily

decomposed to oxygen usinga catalytic bed or hightemperatures, thus extensivedownstream processing isavoided

Can be conducted at ambienttemperature and pressure

Disadvantages Requires large amounts of

ozone, which is expensive

Generation of carboxylic

acids from extensive lignin

degradation

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MATRIC 16

Summary

None of the current pretreatment technologies

described in this presentation meet the criteria for

economic viability

Each of these technologies is currently being

demonstrated at scale

Further information may change the verdict

MATRIC is currently developing a proprietary

chemical pretreatment technology that has the

potential to satisfy all of the requirements outlinedherein