Cellulosic ethanol and the future of biofuels: From carbohydrates to hydrocarbons Efthymios Kallos & Theodora Apostolopoulou "The fuel of the future is going to come from apples, weeds, sawdust – almost anything. There is fuel in every bit of vegetable matter..." – Henry Ford, 1925 Outline • Energy Consumption • Why Biofuels? • Corn Ethanol • Cellulosic Ethanol • Other Biofuels World Energy Demand 15TW • Demand up to x2 in 30 years • Transportation is 15%: 35M bbl per day Source: IEA WEO 2004 World oil consumption 80M bbl per day • 50% of oil consumption goes to transport • U“A o su es 5% of orld’s total • 65% of that is imported Sources: Steve Koonin, Caltech, 10/5/07; https://www.cia.gov/library/publications/the-world-factbook/print/us.html Outline • Energy Consumption • Why biofuels? • Corn Ethanol • Cellulosic ethanol • Other Biofuels Motivation for biofuels • Get liquid fuel from plants • Self-sustained + reliable • Small net CO2 emissions • “olar, i d, et . a ’t e stored for tra sport dire tly • Plants are great batteries! Source: Steve Koonin, Caltech, 10/5/07 Motivation for biofuels We need to burn carbon for fuel • Carbon is the central element in most energy sources (burns well) •100 Gtons of C go back and forth between plants and atmosphere • 0.5% needs to be captured to get 15% of all transportation fuels Source: Steve Koonin, Caltech, 10/5/07 A natural battery Photosynthesis efficiency Solar power in kW per acre captured from plants (energy averaged over 1 year) 800 Solar power on surface (100%) 560 Incident on foliage (70%) 140 Proper wavelengths (25%) 50 Stored Chemically (CH2O) (35%) Actual storage Per capita power consumption (US) 8 10 • Crops (corn, wheat etc) store 0.1%, sugarcane = 1% • Note: We only need 100W to survive (2000 Kcal per day) Source: Whitmarsh and Govindjee, http://www.life.uiuc.edu/govindjee/paper/gov.html Other batteries Energy density [MJ/kg] 160 140 120 100 80 60 40 20 0 142 44 50 35 16 16 1.2 • Fission: 77x106 • E=mc2 : 90x109 Source: http://en.wikipedia.org/wiki/Energy_density; Assume 10 tons of Biomass per acre Outline • Energy Consumption • Why Biofuels? • Corn Ethanol • Cellulosic Ethanol • Other Biofuels United States Corn Ethanol: 7B gallons/year US Power Consumption (2005) Total = 3 TW Commerce Residential 18% 21% Transport 28% Industrial 32% US Corn Crop Yield Total = 90M acres Food Gas + Diesel 97% Ethanol 20% 80% Ethanol 3% • Biomass total energy contribution is 3% (largest renewable source) • 2005 Energy Bill: +60% ethanol by 2012 (15 days of oil imports) • 2030 Goal: 30% of motor fuel (+1000%) Sources: http://en.wikipedia.org/wiki/Energy_use_in_the_United_States; http://www.doi.gov/iepa/EnergyPolicyActof2005.pdf; Chum and Overend, Adv. Solar Energy 15, 83 (2003) Corn Ethanol Infrastructure 138 refineries, 1200 E85 Stations • $0.51/gallon tax credit: $2.2/gallon (but has % less e ergy… • E10 blend: 10% ethanol + 90% gasoline runs OK on current engines (non-corrosive) • E85 blend: 85% ethanol + 15% gasoline need flex engines: currently 6M/240M cars Sources: http://www.ethanolproducer.com; http://e85vehicles.com/e85-stations.htm; http://e85prices.com/; http://www.usfarmsinc.com Corn Ethanol The Cycle O2 Yeast (amylases) Starch Saccharification (Hydrolysis) Heat Photosynthesis Enzymes H2O Sources: Matthew Wald, Scientific American, January 2007 Glucose O2 CO2 Fermentation Ethanol CO2 Combustion Heat CO2 H2O Corn Ethanol Why it o ’t ork • 30% less energy content than gasoline • It’s a food rop de a d dri es ost • It’s ot e ough! % of U“ or crop for 15% of fuel consumption) • 80% of the energy input is fossil fuels! • Requires a lot of fertilizers (causes soil erosion) • Max +30% net energy gain • CO2 emissions similar to fossil fuels Outline • Energy Consumption • Why Biofuels? • Corn Ethanol • Cellulosic ethanol • Other Biofuels Cellulosic Ethanol • Most abundant naturally occurring molecule (helps plants stay upright) US Surface Area Total = 2.2B acres • Non-edible crops (e.g. switchgrass, willow, poplar, wood chips, grass, magazines) • Easier to grow (less water, fertilizers) Corn 90M Useful Biomass: 130M x 8kW = 1TW Other Sources: http://feedstockreview.ornl.gov/; Matthew Wald, Scientific American, January 2007; Assume 10 tons of biomass per acre Cellulosic Ethanol Energy yields MJ of energy delivered per MJ of fossil energy required 10 9 8 7 6 5 4 3 2 1 0 10 8 2.5 0.45 Electricity 0.8 Gasoline Biodiesel 1.3 Corn Ethanol Sources: Matthew Wald, Scientific American, January 2007; http://ngm.com/0710 Sugar Ethanol Cellulosic Ethanol Cellulosic Ethanol CO2 emissions Pounds of CO2 emissions per 130MJ (= 1 gallon of gasoline) 50 45 40 35 30 25 20 15 10 5 0 50 21 20 12 11 3 Electricity Gasoline Biodiesel Corn Ethanol Sources: Matthew Wald, Scientific American, January 2007; http://ngm.com/0710 Sugar Ethanol Cellulosic Ethanol Cellulosic Ethanol Present state • Cellulosic ethanol used commercially: 0 • 2007: Demo power plants only • 2009: 6 commercial plants - 130M gallons/yr = 350MW (Corn ethanol: 18GW) • $385M DoE grant (2007) Sources: Science News Focus, Vol.315, p.1488 (2007) Cellulose Where is it? Sugar producers in plant walls Cellulose Hemicellulose Lignin Other 5% 25% 45% C6H12O6 25% C5H10O5 Sources: Somerville et al., Science 306:2206 (2004); Breaking the Biological Barriers to Cellulosic Ethanol, DOE/SC-0095 (2006) Cellulose Where is it? • For the enzymes to get the cellulose out, lignin must be penetrated • Lignin is structurally similar to asphalt (or we ould ’t ha e trees… •  Pretreatment! Easier to hydrolyze! 1nm Sources: Breaking the Biological Barriers to Cellulosic Ethanol, DOE/SC-0095 (2006) Cellulose Pretreatment: Reducing recalcitrance • Enzymes that convert cellulose to sugars a ’t pe etrate easily without it • Very expensive process! • Not green-friendly Sulfuric Acid + Heat Hydrolysis w/o pretreatment Hydrolysis w/ pretreatment Sources: Breaking the Biological Barriers to Cellulosic Ethanol, DOE/SC-0095 (2006) Cellulosic Ethanol The Cycle Bound cellulose $ Enzymes $ Pretreatment 200o C Cellulose Hydrolysis Yeast Glucose CO2 Fermentation Ethanol O2 CO2 Combustion Heat Acid Heat Photosynt hesis O2 Heat CO2 H2O Sources: Matthew Wald, Scientific American, January 2007; Breaking the Biological Barriers to Cellulosic Ethanol, DOE/SC-0095 (2006) H2O Cellulose In search of the right microbes • Lignin is not understood well • Enzymes are hard to make from scratch • Currently using enzymes from living organisms (slow + expensive) Future: 1. “uper ug: E gi eer yeast that fer e ts he i ellulosi 5 ar o 2. … that a tolerate > % etha ol 3. Lignin modification/breakdown Sources: Chen and Dixon, Nature Biotechnology, Vol.25, No.7 (2007) sugars… Outline • Energy Consumption • Why biofuels? • Corn Ethanol • Cellulosic ethanol • Other Biofuels Brazil Sugarcane ethanol: 4B gallons/year • 1970: Importing 75% of its oil • 2005: Importing 30% • 85% of cars are flex (USA:3%) • 40% of them run on ethanol (USA:2%) • Tropical climate favors crops • Sugarcane is 20% sugars • Easier conversion to biofuel! Sources: https://www.cia.gov/library/publications/the-world-factbook/print/br.html; National Geographic, October 2007 Europe Biodiesel • Production of diesel from plant oils (soybeans, corn) • 85% of world total in Europe! • ¢ heaper tha diesel • 2M vehicles in Germany • 2K stations (10% of total) Potential Sources: Frost & Sullivan; http://en.wikipedia.org/wiki/Biodiesel_around_the_World#Germany; http://www.sage.wisc.edu/energy/ Biodiesel from Algae CO2 Natural oil (waste form of energy) (usable energy) Biofuel production per acre [gallons] 5000 5000 4000 3000 2000 1000 0 300 700 1000 60 • Fastest growing plant on the planet • Daily harvest • Captures CO2 massively • Currently in private sector • $$$ Sources: http://peswiki.com/index.php/Directory:Biodiesel_from_Algae_Oil; Biodiesel from Algae, NREL/TP-580-24190 BioButanol Butanol Energy Density [MJ/gallon] 140 120 100 • • 121 116 C4H10O : 4 carbon alcohol derived from biomass fermentation Structurally similar to gasoline • Can ship through existing pipes 80 60 89 • No need for flex engines 40 20 0 gasoline ethanol butanol • First BioButanol: end of 2007 (Dupond, BP) Sources: http://www.butanol.com/ But: • Low yields (for now)  Synthetic Biology Summary • Biofuels can renewably and cleanly supply 30% of motor fuels • Cor etha ol is ot e ough a d ot gree • Cellulosic ethanol will be successful when yield increases Thank You! Backup Slides Source: CO2 emissions • Energy demand will go up by a factor of 2 • CO2 emissions will go up factor of 2 •  We need 4 times more carbon efficient systems! Source: Steve Koonin, Caltech, 10/5/07