MixAlco Process Cesar Granda, Ph.D. Department of Chemical Engineering Texas A&M University College Station, TX
Oil Refinery Crude Oil $431/ton $66/bbl $1.57/gal Oil Refinery Chemicals Fuels Polymers $566/ton $73/bbl $1.73/gal
Biomass Refinery Food Feed Biomass $40/ton $15/bbl* $0.36/gal* Biomass Refinery Chemicals Fuels Polymers $362 543/ton $50 75/bbl $1.20 1.80/gal * Equivalent energy basis Pharmaceuticals Fiber
Chemicals: Thermochemical platform Lignocellulose Gasify CO H 2 Catalyst (Syngas) Chemicals Fischer Tropsch fuels Methanol Mixed alcohols Ammonia
Chemicals: Thermochemical platform Lignocellulose Disadvantages Gasify CO H 2 Catalyst (Syngas) Chemicals Fischer Tropsch fuels Methanol Mixed alcohols Ammonia 30 40% biomass energy lost to heat Must couple to electricity markets Expensive gasifiers Complex downstream processing Difficult to supply enough biomass to achieve economy of scale
Chemicals: Sugar platform Corn Enzymes Sugars Microorganism Chemicals Squeeze Sugarcane Ethanol Butanol Acetone 2,3 Butanediol Glycerol Acetoin Acetic acid Lactic acid Propionic acid Succinic acid Butyric acid Citric acid
Chemicals: Sugar platform Corn Enzymes Disadvantages Sugars Sugarcane Limited availability Competition with food Requires sterility Difficult separations Squeeze Microorganism Chemicals Ethanol Butanol Acetone 2,3 Butanediol Glycerol Acetoin Acetic acid Lactic acid Propionic acid Succinic acid Butyric acid Citric acid
Chemicals: Sugar platform (2 nd Generation) Lignocellulose Enzymes Sugars Microorganism Chemicals Ethanol Butanol Acetone 2,3 Butanediol Glycerol Acetoin Acetic acid Lactic acid Propionic acid Succinic acid Butyric acid Citric acid
Chemicals: Sugar platform (2 nd Generation) Lignocellulose Enzymes Disadvantages Sugars Requires sterility Expensive enzymes Difficult to use all sugars Uses GMOs Lignin not converted to liquid fuels Extensive pretreatment required Difficult to supply enough biomass to achieve economy of scale Microorganism Chemicals Ethanol Butanol Acetone 2,3 Butanediol Glycerol Acetoin Acetic acid Lactic acid Propionic acid Succinic acid Butyric acid Citric acid
Chemicals: Mixed Acids platform Lignocellulose Mixed- Culture Microorganisms Carboxylic acids/salts Chemistry Chemicals Ketones Aldehydes Secondary mixed alcohols Primary mixed alcohols Carboxylic acids Esters Ethers
Chemical Flowchart Formic Acid Aldehyde Formic Acid Carboxylate Salt Ketone H 2 Carboxylic Acid H 2 Secondary Alcohol Ester Primary Alcohol Ether Ether
Anaerobic Digestion Biomass (cellulose, starch, proteins, fats) Mixed culture of microorganisms Hydrolysis (free sugars, amino acids, fatty acids) Carboxylic acids = Volatile fatty acids [VFAs[ VFAs] ] (e.g., acetic, propionic,, butyric,,, heptanoic acid) (C2 to C7) Acidogenesis Acetogenesis (Carboxylic acids, NH 3, CO 2, H 2 S) (Acetic Acid, CO 2, H 2 ) Methanogenesis (CH 4, CO 2 )
Desirable Process Properties No sterility No GMOs Adaptable No pure cultures Energy in lignin ends up in liquid fuel Low capital No enzymes High product yields No vitamin addition Co-products not required
Desirable Fuel Properties
Fuel Properties Ethanol MTBE Mixed Alcohols Octane high high high Volatility high low low Pipeline shipping no yes yes Energy content low high high Heat of vaporization high low low Ground water damage no yes no
Properties of Fuel Oxygenates Blending Reid Vapor Pressure @38 o C (kpa( kpa) Alcohols Blending Octane (R + M)/2 214 Methanol (MeOH( MeOH) 108 124 Ethanol (EtOH( EtOH) 115 97 Isopropanol (IPA) 106 62 tert-butanol (TBA) 100 34 Isobutanol (IBA) 102 Ethers 55 Methy tertiary butyl ether (MTBE) 110 34 Di-isopropyl isopropyl ether (DIPE) 105 17 Isopropyl tertiary butyl ether (IPTBE) 113 Klass,, Biomass for Renewable Energy, Fuels, and Chemicals, Academic Press P (1998).
Energy Content Energy (MJ/L) (Btu/gal) Gasoline Mixed Alcohols Version 1 Mixed Alcohols Version 2 Ethanol 34.9 125,000 29.0 104,000 26.5 95,000 23.4 84,300
MixAlco Process Version 1 Mixed Alcohol Fuels Biomass Pretreat Ferment Carboxylate Salts Dewater Thermal Conversion Mixed Ketones Hydrogenate Lime Lime Kiln Calcium Carbonate Hydrogen
Pretreatment Mixed Alcohol Fuels Biomass Pretreat Ferment Carboxylate Salts Dewater Thermal Conversion Mixed Ketones Hydrogenate Lime Lime Kiln Calcium Carbonate Hydrogen
Pretreatment is needed Source: Michael Ladisch, Purdue Univ.
Lime Treatment Biomass + Lime Gravel
In-Situ Digestion 48-h h Digestion (g digested/g fed) 1.0 0.8 0.6 0.4 0.2 0.0 Sugar- cane bagasse African millet straw Sorghum straw Tobacco stalks Untreated Lime-treated
Advanced Lime Treatment Air Biomass + Lime Gravel
Lignin Removal Lignin Removal 30 25 20 10 Lignin Content in Treated Bagasse (g lignin/100 g of bagasse) 30 30 25 25 20 15 10 5 0 5 0 50 100 150 200 250 300 50 100 150 200 250 300 Time(days) Time (days) 0 0 50 100 150 200 250 300 50 100 Time 150 (days) 200 250 300 Time (days) Lignin Content in Treated Bagasse (g lignin/100 g treated bagasse) 20 15 10 5 0 No Air Air 30 25 20 10 5 0 Lignin Content (g lignin/100 g bagasse) Lignin Content (g lignin/100 g bagasse) 25 o C 50 o C 15 15 57 o C 25 o C 50 o C 57 o C
Mixed-Acid Fermentation Lime Treatment: 2 weeks, 25 o C Terrestrial Inoculum Total acid concentration (g/l) 60 50 40 30 20 10 0 No Air Air 18 14 11 0 0.2 0.4 0.6 0.8 1 Conversion 8 VSLR (g/(l d)) 4 2 LRT (days) 20.5 15 10 5
Building the Pile ~100 ft
Building the Pile
Building the Pile Crew directing the flow
Fermentation Mixed Alcohol Fuels Biomass Pretreat Ferment Carboxylate Salts Dewater Thermal Conversion Mixed Ketones Hydrogenate Lime Lime Kiln Calcium Carbonate Hydrogen
Environments where organic acids naturally form animal rumen - cattle - sheep - deer - elephants anaerobic sewage digestors swamps termite guts
Why are organic acids favored? C 6 H 12 O 6 2 C 2 H 5 OH + 2 CO 2 ΔG G = -48.56 kcal/mol glucose ethanol C 6 H 12 O 6 3 C 2 H 3 OOH ΔG G = -61.8 kcal/mol glucose acetic acid The actual stoichiometry is more complex C 6 H 12 O 6 acetate + propionate + butyrate + CO 2 + CH 4 + H 2 O
Typical Product Spectrum at Different Culture Temperatures 40 o C 55 o C C2 Acetic 41 wt % 80 wt % C3 Propionic 15 wt % 4 wt % C4 Butyric 21 wt % 15 wt % C5 Valeric 8 wt % <1 wt % C6 Caproic 12 wt % <1 wt % C7 Heptanoic 3 wt % <1 wt % 100 wt % 100 wt %
Storage + Pretreatment + Fermentation Tarp Cover Air Biomass + Lime + Calcium Carbonate Gravel
Technology Evolution Source of inoculum Type of buffer
Marine Inoculum Total acid concentration (g/l) 90 80 70 60 50 40 30 20 10 0 Terrestrial Inoculum No Air VSLR (g/(l d)) 18 14 Marine Inoculum Air 11 0 0.2 0.4 0.6 0.8 1 Conversion 8 4 2 LRT (days) 20.5 15 10 5
Ammonium Bicarbonate Buffer 40 o C Total acid concentration (g/l) 35 30 25 20 15 10 5 0 CaCO3 NH4HCO3 step NH4HCO3 Total Ammonium Bicarbonate Calcium Carbonate 0 5 10 15 20 25 30 35 Time (days)
Ammonium Bicarbonate Buffer 45 55 o C 40 NH 4 HCO 3 35 step size addition Total Acid Concentration (g/l) 30 25 20 15 CaCO 3 10 batch addition 5 batch addition NH 4 HCO 3 0 0 10 20 30 40 50 60 Time (Days)
Dewatering Mixed Alcohol Fuels Biomass Pretreat Ferment Carboxylate Salts Dewater Thermal Conversion Mixed Ketones Hydrogenate Lime Lime Kiln Calcium Carbonate Hydrogen
Vapor-Compression Dewatering Compressor Work Distilled Water Salt Crystals Filter Salt Solution (Fermentor Broth)
Dewatering Energetics Ethanol Distillation (5% to 99.9%) kg steam MJ heat 3 = 8.4 = 28.5% of the combustion heat L ethanol kg ethanol Source: B.L. Maiorella, Ethanol, Comprehensive Biotechnology, Vol. 3, Pergamon Press (1985). MixAlco: Carboxylate Salt Vapor-Compression Dewatering (5% to 100%) 54.3 MJ heat 1000 kg water 95 kg water 5 kg acid = 1.03 MJ kg acid = 5.9% of the combustion heat Source: Jorge Lara, An Advanced Vapor-Compression Desalination System, PhD Dissertation, Texas A&M (2005).
Thermal Conversion Mixed Alcohol Fuels Biomass Pretreat Ferment Carboxylate Salts Dewater Thermal Conversion Mixed Ketones Hydrogenate Lime Lime Kiln Calcium Carbonate Hydrogen
Thermal Conversion Stoichiometry O O O H 3 CCOCaOCCH 3 Η 3 CCCH 3 Calcium Acetate Acetone + CaCO 3 O O O H 3 CCH 2 COCaOCCH 2 CH 3 Η 3 CCH 2 CCH 2 CH 3 + CaCO 3 Calcium Propionate Diethyl Ketone O O O H 3 CCH 2 CH 2 COCaOCCH 2 CH 2 CH 3 Η 3 CCH 2 CH 2 CCH 2 CH 2 CH 3 + CaCO 3 Calcium Butyrate Dipropyl Ketone
Thermal Conversion Stoichiometry Commonly known as dry distillation. Used before and during WWI to make acetone from calcium acetate
Thermal Conversion Kinetics 45 40 35 30 t (min) 25 20 15 10 5 0 380 400 420 440 460 480 500 T ( C) Conversion (%) 99 95 90
Hydrogenation Mixed Alcohol Fuels Biomass Pretreat Ferment Carboxylate Salts Dewater Thermal Conversion Mixed Ketones Hydrogenate Lime Lime Kiln Calcium Carbonate Hydrogen
Ketone Hydrogenation Stoichiometry O OH H 3 CCCH 3 + H 2 H 3 CCCH 3 H Acetone Isopropanol O OH H 3 CCCH 2 CH 3 + H 2 H 3 CCCH 2 CH 3 H Methyl Ethyl Ketone 2-Butanol O OH H 3 CCH 2 CCH 2 CH 3 + H 2 H 3 CCH 2 CCH 2 CH 3 H Diethyl Ketone 3-Pentanol
Ketone Hydrogenation Liquid Ketones Catalyst = 200 g/l Raney nickel Temperature = 130 o C Time = 35 min @ P = 15 atm (220 psi) H 2
MixAlco Process Version 2 Mixed Alcohol Fuels Biomass Lime Pretreat Lime Kiln Ferment Carboxylate Salts Dewater Calcium Carbonate Acid Springing Mixed Acids Esterification Hydrogenolysis Hydrogen
Acid Springing Calcium Salts R 3 N HAc Ca(Ac) 2 R 3 NHAc H 2 O CO 2 CaCO 3 R = - CH 2 CH 3 R= - CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 R 3 NHAc R 3 N
Acid Springing Ammonium Salts NH 3 HAc NH 4 Ac R= - CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 R 3 NHAc R 3 N
MixAlco Process Version 2 Mixed Alcohol Fuels Biomass Lime Pretreat Lime Kiln Ferment Carboxylate Salts Dewater Calcium Carbonate Acid Springing Mixed Acids Esterification Hydrogenolysis Hydrogen
Hydrogenation Stoichiometry O H 3 CCOH + HOCH 2 CH 2 CH 2 CH 2 CH 3 Heavy Alcohol O H 3 CCOCH 2 CH 2 CH 2 CH 2 CH 3 + 2 H 2 Ester O H 3 CCOCH 2 CH 2 CH 2 CH 2 CH 3 + H 2 O Ester H H 3 CCOH + HOCH 2 CH 2 CH 2 CH 2 CH 3 H Heavy Alcohol O H 3 CCOH + 2 H 2 Acetic Acid Ethanol H H 3 CCOH + H 2 O H
Esterification + Hydrogenolysis Water Mixed Alcohols Carboxylic Acids Esters Alcohols H 2 Heavy Alcohols
Esterification + Hydrogenolysis Water + NH 3 Mixed Alcohols NH 4 Carboxylate Salts Esters Alcohols H 2 Heavy Alcohols
MixAlco Process Version 2 Ammonium Salts CO 2 NH 4 HCO 3 NH 3 Esters Mixed Alcohol Fuels Biomass Pretreat Ferment Dewater Esterification Hydrogenolysis Lime Carboxylate Salts Hydrogen
Esterification Acid catalyzed (H 2 SO 4 ) or solids acid catalysts. Same reaction as free fatty acids esterification in biodiesel production.
Ester Hydrogenolysis Copper chromite high temperatures (> 200 o C ) high pressures (> 600 psi) widely used in industry (e.g., for making detergent alcohols from fatty acids) Reduced CuO-ZnO catalyst low temperature (~150 o C) low pressure (<350 psi) preferred
Plant Capacity Plant Capacity (tonne/h)) (mill gal/yr) Version 1 Version 2 *City Population Base Case 2 1.5 2.3 40,000 10 7.6 11.3 200,000 40 30.3 45.1 800,000 160 121 181 3,200,000 800 606 903 16,000,000 * Feedstock = Municipal solid waste + Sewage sludge
Effect of Scale on Capital Cost Versions 1&2 300 250 Capital Cost (mill $) 200 150 100 50 0 0 100 200 300 400 500 600 700 800 900 Capacity (tonne/h)
Mixed Ketone Selling Price Version 1 (15% ROI) 1.00 2 10 Capacity (tonne/h) Ketone Selling Price ($/gal) 0.80 0.60 0.40 0.20 0.00-40 -20 0 20 40 Biomass Cost ($/tonne) 40 160 800
Mixed Alcohol Selling Price Version 1 (15% ROI) Alcohol Selling Price ($/gal) 1.00 0.80 0.60 0.40 0.20 2 10 40 160 800 Capacity (tonne/h) 0.00-40 -20 0 20 40 Biomass Cost ($/tonne)
Mixed Secondary Alcohols (e.g., isopropanol) (Version 1) Secondary Alcohols 1.5 7.6 30.3 121 606 Yield = ~ 86 gal/dry ton
Mixed Acid Selling Price Version 2 (15% ROI) 0.10 2 Capacity (tonne/h) Acid Selling Price ($/lb) 0.08 0.06 0.04 0.02 0.00-40 -20 0 20 40 Biomass Cost ($/tonne) 10 40 160 800
Carboxylic Acids
Mixed Alcohol Selling Price Version 2 (15% ROI) Alcohol Selling Price ($/gal) 1.00 0.80 0.60 0.40 0.20 2 10 40 160 800 Capacity (tonne/h) 0.00-40 -20 0 20 40 Biomass Cost ($/tonne)
Mixed Primary Alcohols (e.g., ethanol) (Version 2) Yield = ~ 130 gal/dry ton
Enzymatic route/ethanol fermentation Source: http://www1.eere.energy.gov/biomass/ethanol_yield_calculator.html Yield = ~100 gal/dry ton for bagasse (90% of theoretical)
Energy Content Energy (MJ/L) (Btu/gal) Gasoline Mixed Alcohols Version 1 Mixed Alcohols Version 2 Ethanol 34.9 125,000 29.0 104,000 26.5 95,000 23.4 84,300
Yield on an ethanol equivalent basis 130 gal/ton 95,000/84,300 = 147 gal/ton ~50% more than enzymatic/ethanol fermentation route
Conclusions The technology is - green - profitable - world-wide wide - simple Many potential products - ketones - alcohols - organic acids
Conclusions Near-term applications - waste chemicals Mid-term applications - waste fuels Far-term applications - crops fuels
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