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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
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)
5
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.
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
=
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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.
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
20
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