Co-production of Ethanol and Cellulose Fiber from Southern Pine: A Technical and Economic Assessment

Transcription

1 Co-production of Ethanol and Cellulose Fiber from Southern Pine: A Technical and Economic Assessment Jim Frederick, Steve Lien, Chuck Courchene, Niko DeMartini, Art Ragauskas and Kristiina Iisa Georgia Institute of Technology 1

2 Average Bulk Fuel-grade Ethanol Prices U.S., by State: November 19, 2007 Iowa: 1.92 Illinois: 2.05 Kansas: 2.08 Minnesota: 1.92 Missouri: 1.93 North Dakota: 1.95 Nebraska: 2.12 South Dakota: 2.00 Wisconsin: Ethanol production, million gal/yr World Ethanol Production Capacity Brazil U.S. China Rest of world Source: Ethanol Data from Renewable Fuels Assoc. 2

3 U.S. Ethanol Production Capacity June, 2007 Ethanol production rate, billion gal/yr Jan-99 Jan-00 Producing Under Construction Jan-01 Jan-02 Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Present U.S. Ethanol Production Capacity U.S. target: 35 billion gal Today s ethanol: entirely from corn Projected limits from corn: 15 billion gal/yr from cellulosic biomass: >100 billion gal 3

4 Starting Point for Today Ethanol prices are strong and market is expected to continue increasing Ethanol from starch will not meet the U.S. demand Can ethanol be made economically from lignocellulosic biomass? If it can, how best to integrate ethanol production into the forest products industry? Composition of Loblolly Pine 100% 80% 60% 40% Dry, bark-free, ash-free basis Hemicellulose 21.3% Lignin 26.9% Xylan Mannan Extractives Uronic anhydride Acetal Arabinan Galactan 20% Cellulose 43.8% 0% 4

5 Composition of Loblolly Pine 100% 80% 60% 40% 20% Dry, bark-free, ash-free basis Hemicellulose 21.3% Ethanol Lignin 26.9% Xylan Mannan Cellulose 43.8% Extractives Uronic anhydride Acetal Ethanol Arabinan Galactan Fiber 0% Ethanol from Loblolly Pine 5

6 Ethanol from Loblolly Pine Carbohydrates H 2 SO 4 Lime Wood WOOD HANDLING ACID HEMICELLULOSE HYDROLYSIS PRETREATMENT OF HYDROLYZATE CLEANUP Gypsum Acetic Acid Nutrients CELLULASE PLANT Enzyme SIMULTANEOUS SACCHARIFICATION & FERMENTATION CO 2 Power CHP PLANT Process Biofuel Steam Power DISTILLATION/ DEHYDRATION/ EVAPORATION Ethanol Excess Biofuel Impact of Carbohydrate Recovery 5 Amount relative to ethanol produced Exportable biofuel Internal consumption CO 2 Ethanol 75% 95% Carbohydrates extracted, % 6

7 Cost of Ethanol from Loblolly Pine Carbohydrates Carbohydrates recovered 75% 95% as sugars for fermentation Ethanol production, gal/yr 74x x10 6 Break-even cost of`ethanol $1.61 $1.37 Capital intensity, $/(gal/yr) $4.47 $3.89 Ethanol price 5/25/07 ~$2. (bulk fuel-grade) Note: Capital costs scaled from Wooley, NREL (1999) Ethanol and Fiber from Loblolly Pine 7

8 Ethanol + Fiber from Loblolly Pine Carbohydrates H 2 SO 4 Lime Wood WOOD HANDLING PARTIAL EXTRACTION HYDROLYZATE CLEANUP Gypsum Acetic Acid FERMENTATION CO 2 KRAFT PULP MILL CHP PLANT DISTILLATION/ DEHYDRATION/ EVAPORATION Ethanol Process Biofuel Steam Power Fiber Excess Biofuel Excess Power Original Concept Hemicellulose is easily extracted from wood but cellulose is not Pre-extraction removes hemicellulose that would otherwise end up in black liquor Digester yield will not change Mill will gain recovery boiler capacity Pulp will be the same or at least be of acceptable quality 8

9 Distribution of Cellulose After Extraction and Kraft Pulping Loblolly Pine Distribution of cellulose and glucose from it, wt-% of wood 40 In Fiber In Black Liquor 10 In Hydrolyzate Wood mass extracted prior to pulping, wt-% Fate of Biomass (14% Wood Extraction for Ethanol Production) Products (tons) Basis: 1000 t fiber Distribution of Value Fiber only 22% 9% 9% 12% 91% 69% 69% Fiber + ethanol no cellulose loss 19% Fiber + ethanol with cellulose loss Ethanol CO 2 Biofuels Fiber 9

10 Thermal Load to Recovery Boiler Capacity required, % of base case 1% 125% 100% 75% % With cellulose loss No cellulose loss 25% 0% 0% 5% 10% 15% 20% Wood extracted, wt-% (dry basis) Basis for Analysis Constant pulp production Additional wood processed when ethanol is produced 10

11 Summary for Constant Pulp Production 469,000 ODT/yr bleachable grade brown pulp Wood mass extracted before pulping With Cellulose Loss 0% 6% 10% 14% 18% Ethanol, 10 6 gal/yr Exportable power, MW Exportable biomass, thousand ODT/yr Break-even ethanol price, $/gal $2.92 $2.57 $2.45 $2.45 Without Cellulose Loss Ethanol, 10 6 gal/yr Exportable power, MW Purchased biomass, thousand ODT/yr Break-even ethanol price, $/gal $2.10 $1.55 $1.36 $1.33 Impact of Retaining Cellulose in Fiber (14% of wood mass extracted) Cellulose Lost No Cellulose Lost Biomass input, t/d Biomass output, t/d as ethanol as CO as fiber a as black liquor as bark as biomass fuel Total, t/d a A kraft pulp mill would consume 3036 ODt/day undebarked wood to produce this pulp without ethanol 11

12 Capacity Utilization of Pulping & Recovery Operations (Constant Pulp Production) Capacity utilization, % of base case 1% 125% 100% 75% % 25% BL Evaporators Recovery Boiler 0% 0% 5% 10% 15% 20% Wood extracted, wt-% (dry basis) Recaust, Lime Kiln Brownstock washers Digesters Summary 14% Wood Extraction Prior to Pulping Complete Cellulose Hydrolysis Scenario Cellulose loss? Wood consumed, thousand ODT/yr, bark-free Brownstock production, thousand ODT/yr Ethanol, 10 6 gal/yr Yes 1, Constant Pulp Production No Ethanol Only Exportable power, MW Exportable biomass, thousand ODT/yr Break-even ethanol price, $/gal $2.45 $1.36 $

13 Sensitivity of Break-even Cost of Ethanol from Hemicellulose (Loblolly Pine, 14% Extraction) % change in break-even cost for ethanol 60% 40% 20% 0% -20% -40% Wood Power Oil Hog Fuel -100% -% 0% % 100% 1% % change in raw material, energy, or fuel cost Comparison of Cost Study Results Feedstock Dry Milled Corn 1 Corn Stover 1 Yellow Poplar 2 Loblolly Pine EtOH only EtOH+fiber Ethanol product, 10 6 gal/yr 20 Ethanol yield, gal/t biomass Total Prod n Costs, $/gal $1.52 $1.74 $1.48 $1.78/ $1.59 $2.45/ $1.36 Total Capital Invest, $10 6 $48 a $232 $327 $260 $279/ $177 Capital intensity, $/(gal/yr) $0.96 $4.64 $6.53 $5.20 $14.0/ $8.9 Basis: late year 2006 costs, with capacities adjusted to million gal/yr. 1. McAloon et al., USDA/NREL (2000) 2. Wooley et al., NREL (1999) 13

14 Biochemical versus Thermochemical Ethanol Feedstock Ethanol product, 10 6 gal/yr Yellow Poplar (Wooley) Loblolly Pine (Frederick) Loblolly Pine (Phillips) Black Liquor (Larson) 15.3 Range Fuels (Soperton, GA) Ethanol yield, gal/t biomass Total Prod n Costs, $/gal $1.48 $1.78 $1.19 $1.52 Total Capital Invest, $10 6 $327 $260 $168 $260 Capital intensity, $/(gal/yr) $6.53 $5.20 $2.72 $17.0 $4.6 Conclusions Ethanol can be produced competitively from loblolly pine Co-production of ethanol and fiber may be competitive Need to decrease cellulose loss Competitiveness will increase as extraction and fermentation technologies for wood carbohydrates improve 14

15 Technical Gaps Cellulose loss during pulping of pre-extracted chips needs to be reduced More rapid/efficient hemicellulose extraction methods are needed to improve profitability of coproduction of ethanol and fiber Rapid and efficient conversion of pentose sugars is required in both cases High hydrolysis conversion of cellulose to sugars is needed to improve profitability of stand-alone ethanol plant 15