DENSIFYING & HANDLING AFEX BIOMASS: A COOPERATIVE RESEARCH PROJECT

Bruce E. DaleProfessor of Chemical Engineering

Associate Director: Office of Biobased TechnologiesMichigan State University

Presented at:Northern Plains Biomass Economy: What Makes Sense?

Fargo, North DakotaSeptember 22, 2009

Reactor Explosion

AmmoniaRecovery

BiomassTreatedBiomass

RecycleAmmonia

GaseousAmmonia

Reactor Expansion

AmmoniaRecovery

BiomassTreatedBiomass

AmmoniaGaseous

Ammonia

Heat

AFEX Process Overview

AFEX process description and properties•hot, concentrated (~15M) ammonia:water mix, short rxn time•rapid pressure release ends treatment, cools system•little biomass degradation, high yields, residual ammonia value•no separate liquid phase (“dry to dry”)—very high solids loadings possible•Typical process conditions

•Pressure 20-30 atm•Temperature 70-140 C•Residence time 5-10 minutes•Ammonia: dry biomass loading (0.3 -2.0 to 1) (w/w)•Water: dry biomass content (0.2 – 2.5 to 1) (w/w) 2

3

Before and After AFEX

Confocal Microscopy Corn Cob Granule Sclereid Cells

Before AFEX After AFEX

Sclereids Safranin dye binds to lignin-like compounds smeared over the surface(sclerenchyma cells)

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Untreated Corn Cob Granule (100x) AFEX treated Corn Cob Granule (100x)

Surface Characterization by Electron Microscopy

SEM images of corn cob granules indicate that AFEX is responsible for solubilizing and relocating alkali soluble compounds (e.g., lignin phenolics, oligosaccharides and other reaction products) on the biomass surface. Lignin has a reduced glass transition temperature (Tg) after partial cleavage by ammonia that allows it to be relatively easily mobilized at temperatures close to 100 0C.

AFEX Biomass Pellets: No Binder

Ruminant Animals & Biorefineries:Improve Cellulose Conversion for Biorefinery= Improve Cellulose Digestibility for Cows

Mobile Cellulose Biorefinery (a.k.a. Cow)

Stationary Cellulose Biorefinery

Ruminant Bioreactor:

Capacity ~ 40 Gal Fermentor

Biomass Input ~ 26 Lb/Day*

SSCF Bioreactor:Biomass Input ~ 5,000 Dry Ton/Day

= 10 M Dry Lb/DayCapacity ~ 45 M Gal Fermentor

Cow is 3x more efficient than industrial bioreactor7

=

8

9

Sustainable rural economies + Sustainable biofuels

RBPC System Effect 1 – Larger Biorefineries in high yield areas

Effect 2 – biorefiners in remote rural areas

+

10

Feasible Set Pr

ice-

Cos

t-Mar

gin

Delivered Feedstock Price

$0

$10

$20

$30

$40

$50

$60

$10 $15 $20 $25 $30 $35 $40 $45 $50 $55 $60

250 tpd

500 tpd

1,000 tpd

3,000 tpd 6,000 tpd

Only > 6,000 tpd

This is the minimum size facility that will work @ given combo

Feed Cross-Subsidization

$0.00

$5.00

$10.00

$15.00

$20.00

$25.00

$30.00

$35.00

Min

imu

m P

CM

666 888 1333 2666 4444

RBPC Capacity (TPD)

W/O Animal Feed

W/ Animal Feed

NDSU-SDSU-MSU Project IThe overarching goal of this proposal is to develop and validate the

performance of an integrated biomass pretreatment and densification process that will reduce the logistical hurdles facing second generation biofuels. This process will link Ammonia Fiber Expansion (AFEX) pretreatment with a novel compaction process to produce densified biomass particles (hereafter called PAKS) that: 1) retain their original composition, 2) have a bulk density 3-5 times that of baled biomass, and 3) eliminate the need for further pretreatment at the processing plant. A prior study indicated that AFEX/pelletizing would be scalable down to the 250 ton per day level.

Recent AFEX improvements, coupled with the proposed compaction process will enable regional biomass processing centers (RBPCs). This will minimize the distance that low density feedstock bales will be transported. Densified PAKS will then be more efficiently transported to centralized processing facilities. Based on preliminary analysis, we believe these PAKS will integrate seamlessly into existing transportation and handling infrastructure used for grains.

NDSU-SDSU-MSU Project IISpecific project objectives:1. Optimize AFEX conditions for corn stover, switchgrass, and prairie cordgrass to simultaneously enhance binding properties and increase hydrolysis efficiency following densification and storage.2. Determine optimal ComPAKco operating conditions to convert pretreated biomass into densified PAKS, while minimizing energy requirements.3. Evaluate the effects of short and long term storage of the PAKS on Physical characteristics (e.g., flowability, compression strength,water solubility/absorption, etc).4. Determine the effects of densification and storage on ratesand yields of hydrolysis and fermentation.5. Conduct economic and energy analyses of process to determine optimal and minimal scale.

Questions ??

Learning Curve: Sugar Ethanol Production Cost( O

ct. 2

002)

US$

/ G

J

Accumulated Ethanol Production ( Million m3)

Ethanol Producers: Brazil

Gasoline:Rotterdam

0 50

(J. Goldemberg, 2003)

100 150 200 2501

10

100

1980

19861990

1993

1996

1999

2002

9112.56.5

$/GJ

11 (generated)23 (delivered)

Energy Carrier Representative Price

FossilPetroleum $50/bblNatural gas $10/kscfCoal $55/ton

w/ carbon capture @ $150/ton C

BiomassSoy oil $0.50/lbCorn kernels $3.5/buSugar cane $93/tonCellulosic cropsa $60/tonCellulosic residues

Electricity $0.045/kWh$0.085/kWh

a e.g. switchgrass, short rotation poplar

30.0106.0 4.0

Some < 0

Common Units

Modified from Lynd et al., Nature Biotech., 2008

At $4/GJ, the purchase price of cellulosic biomass is competitive with oil at $23/bbl.

Cellulosic Biomass: The Cheapest GJ in a Carbon-Constrained World

Distillation BiofuelsDrying

Co-Product Recovery

Animal FeedChemicals

Sugar Cane Process

Cellulose Conversion

Hydrolysis

Corn Process

Cellulose Process

Cellulose PretreatmentCellulose

• Corn Stover• Grasses• MSW• Forest Residues• Ag Residues• Wood Chips

Ferment-ationSugarSugar

Cane

CornKernels

Starch Conversion(Cook or

Enzymatic Hydrolysis)

Biofuel Production Flowchart: Sugar Platform

MY LAB WORKS HERE-AFEX

PROCESS

Objective is to generate clean, fermentable sugars @ about 6¢ per pound- big challenge!

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Glucan conversion for various AFEX treated Feed stocks

0

20

40

60

80

100

UT

AFEX

Glu

can

conv

ersi

on

Different Feed Stock

SwitchgrassSugarcaneBagasse

DDGS

Rice straw

Corn stover

Miscanthus

Enzymatic hydrolysis: 25 mg of Cellulase and 2.5 mg of xylanase/g of glucan, 50 oC,for 168h. About 70% xylan conversion achieved for most feedstocks.

Biomass Conversion for Different FeedstocksBefore and After AFEX Pretreatment

0

100

200

300

400

500

600

700

800

900

1000

SI AF OG RS SO CS CS - N SG SG - N WS BG MS

ND

F D

iges

ted

(g/k

g bi

omas

s)

UntreatedAFEX - Treatment + rumenTotal NDF

Rumen and AFEX Digestion of NDF

SI Corn silage SO Forage sorghum BG BagasseAF Alfalfa CS Corn stover MS MiscanthusOG Orchardgrass SG SwitchgrassRS Rice Straw WS Wheat straw -N NH3 treated

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Why Regional Biomass Processing Centers?• Concept: separate pretreatment operations from

hydrolysis & fermentation (“distributed biorefining”)• Pretreatment enhances value of cellulosic biomass for

animal feeding and biofuel production• Advantages:

– Logistics: aggregate, process, store, supply biomass – Densify, homogenize different biomass materials for

cheaper, easier, thus more distant transport– Diversify biorefinery supply– reduce feedstock risk– Reduce capital cost of biorefinery, reduce capital risk– Reduce cost of pretreated biomass by $20-$30/ton– Provide rural economic development/wealth creation– Address “Food vs Fuel” concerns directly– Increase land use efficiency of biofuels- “indirect land

use change” is positive, fewer acres required– Combined effect of integrating protein recovery &

cellulosic feeds production is ~500 hundred million tons of cellulosic biomass with no new acres 21