1 DENSIFYING & HANDLING AFEX BIOMASS: A COOPERATIVE RESEARCH PROJECT Bruce E. Dale Professor of Chemical Engineering Associate Director: Office of Biobased Technologies Michigan State University Presented at: Northern Plains Biomass Economy: What Makes Sense? Fargo, North Dakota September 22, 2009
2 AFEX Process Overview Recycle Ammonia Ammonia Recovery Gaseous Ammonia Biomass Reactor Heat Explosion Expansion Treated Biomass 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 atm Temperature C Residence time 5-10 minutes Ammonia: dry biomass loading ( to 1) (w/w) Water: dry biomass content ( to 1) (w/w) 2
3 Before and After AFEX 3
4 Confocal Microscopy Corn Cob Granule Sclereid Cells Before AFEX After AFEX Sclereids (sclerenchyma cells) Safranin dye binds to lignin-like compounds smeared over the surface
5 Surface Characterization by Electron Microscopy Untreated Corn Cob Granule (100x) AFEX treated Corn Cob Granule (100x) 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 C. 5
6 AFEX Biomass Pellets: No Binder
7 Ruminant Animals & Biorefineries: Improve Cellulose Conversion for Biorefinery = Improve Cellulose Digestibility for Cows Stationary Cellulose Biorefinery Mobile Cellulose Biorefinery (a.k.a. Cow) = SSCF Bioreactor: Biomass Input ~ 5,000 Dry Ton/Day = 10 M Dry Lb/Day Capacity ~ 45 M Gal Fermentor Ruminant Bioreactor: Biomass Input ~ 26 Lb/Day * Capacity ~ 40 Gal Fermentor Cow is 3x more efficient than industrial bioreactor 7
9 RBPC System Effect 1 Larger Biorefineries in high yield areas + Effect 2 biorefiners in remote rural areas Sustainable rural economies + Sustainable biofuels 9
10 Feasible Set Delivered Feedstock Price $10 $15 $20 $25 $30 $35 $40 $45 $50 $55 $60 $0 Price-Cost-Margin $10 $20 $30 $40 $50 $ tpd 250 tpd 3,000 tpd This is the minimum size facility that will given combo Only > 6,000 tpd 1,000 tpd 6,000 tpd 10
12 NDSU-SDSU-MSU Project I The 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.
13 NDSU-SDSU-MSU Project II Specific 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 rates and yields of hydrolysis and fermentation. 5. Conduct economic and energy analyses of process to determine optimal and minimal scale.
15 Learning Curve: Sugar Ethanol Production Cost 100 (J. Goldemberg, 2003) ( Oct. 2002) US$ / GJ Ethanol Producers: Brazil Gasoline: Rotterdam Accumulated Ethanol Production ( Million m 3 )
16 Cellulosic Biomass: The Cheapest GJ in a Carbon-Constrained World Energy Carrier Fossil Representative Price Common Units $/GJ Petroleum $50/bbl Natural gas $10/kscf Coal $55/ton w/ carbon $150/ton C Electricity Biomass Soy oil Corn kernels Sugar cane Cellulosic crops a Cellulosic residues $0.045/kWh $0.085/kWh $0.50/lb $3.5/bu $93/ton $60/ton (generated) 23 (delivered) Some < 0 a e.g. switchgrass, short rotation poplar Modified from Lynd et al., Nature Biotech., 2008 At $4/GJ, the purchase price of cellulosic biomass is competitive with oil at $23/bbl.
18 Biofuel Production Flowchart: Sugar Platform Cellulose Process Corn Process Sugar Cane Process MY LAB WORKS HERE- AFEX PROCESS Corn Kernels Sugar Cane Starch Conversion (Cook or Enzymatic Hydrolysis) Sugar Fermentation Distillation Co-Product Recovery Animal Feed Chemicals Drying Biofuels Cellulose Cellulose Pretreatment Cellulose Conversion Hydrolysis Corn Stover Grasses MSW Forest Residues Ag Residues Wood Chips Objective is to generate clean, fermentable about 6 per pound- big challenge!
19 100 Biomass Conversion for Different Feedstocks Before and After AFEX Pretreatment Glucan conversion for various AFEX treated Feed stocks 80 Glucan conversion Switchgrass Corn stover Sugarcane Bagasse Rice straw Miscanthus DDGS 20 UT 0 Different Feed Stock AFEX Enzymatic hydrolysis: 25 mg of Cellulase and 2.5 mg of xylanase/g of glucan, 50 o C, for 168h. About 70% xylan conversion achieved for most feedstocks. 19
20 Rumen and AFEX Digestion of NDF Untreated AFEX - Treatment + rumen Total NDF NDF Digested (g/kg biomass) SI AF OG RS SO CS CS - N SG SG - N WS BG MS SI Corn silage SO Forage sorghum BG Bagasse AF Alfalfa CS Corn stover MS Miscanthus OG Orchardgrass SG Switchgrass RS Rice Straw WS Wheat straw -N NH3 treated 20
21 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