Algae Under Pressure and in Hot Water Hydrothermal Pathways to Renewable Fuels Phillip E. Savage University of Michigan Chemical Engineering Dept. 1
Energy Usage Trends society transitions to new energy sources when it improves life - not because of scarcity 2
Why Liquid Fuels from Biomass? ~ 15 TW ~ 450 quads We need liquid fuels for transportation. Biomass is recently stored solar energy - renewable energy courtesy A. Yokochi - Oregon State Univ We can grow enough biomass to meet this need. Biofuels are renewable - live off the sun in real time. 3
Can algae be a better biofuel feedstock? 4 Major issues with terrestrial crops: Expensive Food/Feed vs. fuel Require lots of land, water, and fertilizer Less efficient at photosynthesis Indirect land use change Crop Oil Yield (L ha -1 y -1 ) Soybean 450 Camelina 560 Sunflower 955 Rapeseed 1,190 Jatropha 1,890 Oil Palm 5,950 Microalgae 3,800-50,800 Chisti Y. Biodiesel from microalgae. Biotechnol Adv 2007;25(3):294-306. 4
Microalgae Aquatic biomass (lots of water) Can have very high oil content along with protein and polysaccharide No food vs. fuel competition Water provides structural support (no lignin) High biomass growth rates ~ 5000 gal/acre/yr (~ 10X relative to terrestrial biomass) Can grow in salt water (reduce fresh water needed) Industrial ecology possibilities - co-locate with water treatment and coal-fired power plants 5
Land Area to Replace 50% of Petroleum Distillates Algae need much less land than conventional energy crops! Adapted from Bryan, et al. (2008) 6
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Biofuel from Microalgae Standard approach is dewatering, drying, lipid extraction (e.g., with hexane), and oil processing to make biodiesel or green diesel $$$$, requires organic solvents, acids, bases Let s use a potentially greener approach! 8
Overview Develop biofuel processes that use wet algae paste avoid drying minimal dewatering no lipid extraction Feedstock flexible high-lipid algae not required useful for other wet biomass wet biomass Hydrothermal Process Hydrothermal approach - Use high-temperature liquid water to convert biomass into fuels mimic nature break down biomacromolecules in algae fuel product 9
Introduction to High-Temperature Water (HTW) HTW: Liquid H 2 O at 200 350 o C (T C = 374 o C) Properties of HTW different from room-temperature water Fewer and less persistent H-bonds Lower dielectric constant Increased solubility of organic compounds Higher K W = (H + )(OH ) Dielectric Constant log Kw 100-11 80-12 60 40-13 20 enhanced acid catalysis 0 Benzene mole fraction -14 0.1000 0.0100 0.0010 0 0 100 200 300 400 0.0001 25 75 125 175 225 275 T T ( o C) ( o C) Temperature ( o C) 10
Hydrothermal Routes from Wet Algae to Biofuels Crude Biodiesel Wet Biomass (algae) Liquefaction ~ 350 C Fatty Solids Deoxygenation Crude Bio-oil US Patent: 2012/0079760A1 Upgrade Hydrocarbon Fuel Hydrocarbon Fuel or Oil US Patent: 2012/0055077A1 CH 4, H 2 Processes that work with wet biomass (its natural state) and avoid organic solvents could be less costly, more energy efficient, and more environmentally sustainable. Savage, Science, 2012 11
Microalgae HTL Process http://www.igb.fraunhofer.de/www/ Presse/Jahr/2000/en/PI_Algae.en.html CO 2 H 2 O aqueous by-product Microalgae Growth Energy Recovery Hydrothermal Liquefaction (HTL) bio-oil components N, P recycling liquid fuel OIL Energy Recovery Recover energy & nutrients in aqueous stream essential for energy-positive & sustainable process Hydrothermal Catalytic Processing 12
Hydrothermal Liquefaction of Microalgae wet algal biomass Hydrothermal Liquefaction Crude bio-oil Brown, Duan, Savage, Energy & Fuels, 2010 Valdez, Dickinson, Savage, Energy & Fuels, 2011 Duan, Savage, Ind. Eng. Chem. Res., 2011 Valdez et al., Biomass & Bioenergy, 2012 Valdez & Savage, Algal Research, 2013 13
Experimental Procedure Aqueous Phase HTL Products Biocrude (Organic Phase) Solids Light Biocrude Heavy Biocrude Pressure (MPa) 30 25 20 15 10 5 Liquid Water 300 C 250 C 350 C 400 C Water Vapor 0 100 200 300 400 500 Temperature ( C) 14
Elemental Analysis of Bio-Crude Temp. ( C) C H O N S Dry Algae 43.3 6.0 25.1 6.4 0.53 200 74.6 10.8 11.8 2.4 0.44 300 75.2 10.3 9.8 4.3 0.79 400 76.7 10.3 8.7 3.6 0.91 Crude Oil 2 83-87 10-14 0.1-1.5 0.1-2.0 0.5-6.0 From Brown, Duan, & Savage., Energy & Fuels. 2010 O decreased with temp. S increased with temp. Nannochloropsis sp. 2 Data from h6p://en.ci9zendium.org/wiki/petroleum 15
Biocrude Yields (wt%) from Isothermal HTL 50 Total Biocrude 40 yield (wt %) 30 20 10 50 80% energy recovery in biocrude 0 0 15 30 45 60 75 90 time (min) Valdez et al., Biomass & Bioenergy, 2012 16
Total Ion Chromatogram of Bio-Crude C16 fatty acids O OH O OH 350 C, 60 min O HO H N OH 17
C C & N distributions at 20 min Solids Watersoluble Products 250 C 350 C 400 C Light Biocrude Heavy Biocrude Solids Watersoluble Products Gas Light Biocrude Heavy Biocrude Solids Watersoluble Products Gas Heavy Biocrude Light Biocrude N Solids Light Biocrude Heavy Biocrude Watersoluble Products Solids Watersoluble Products Light Biocrude Heavy Biocrude Watersoluble Products Solids Light Biocrude Heavy Biocrude 18
Reaction Network? 80 70 Solids 350ºC 1 Aqueous-phase Products Yield (wt %) 60 50 40 30 Aqueous-phase Products Light Biocrude Solids 2 3 Light Biocrude Heavy Biocrude 20 10 Heavy Biocrude Gas 0 0 30 60 90 time (min) P. Valdez, et al., Hydrothermal Liquefaction of Nannochloropsis sp.: Systematic study of process variables and analysis of the product fractions, Biomass and Bioenergy, (2012) 19
Reactions of Intermediate Products 350 C, 40min 15 wt % slurry Solids 350 C, 10-40min 5 wt % loading Aqueous-phase Products Product Workup 200mL Induction-heated Parr Reactor Light Biocrude Heavy Biocrude 4mL Swagelok Reactor + Gas 20
Reaction of Aqueous-phase Products Aqueous-phase produces Light and Heavy Biocrudes and relatively large amounts of CO 2 (~3 wt %) yield (wt %) 120 100 80 60 40 T = 350 C Aqueous-phase Products Solids 1 2 3 Aqueous-phase Products 4 Light Biocrude Heavy Biocrude 5 6 Gas 20 Heavy Biocrude Light Biocrude 0 0 10 20 30 Gas 40 Solids time (min) Valdez & Savage, Algal Research, under review 21
Reaction of Light Biocrude Light Biocrude produces Aqueous-phase and Heavy Biocrude 100 T = 350 C Light Biocrude 80 yield (wt %) 60 40 Aqueous-phase Products 1 6 7 4 2 Solids Light Biocrude 3 5 Aqueous-phase Products 8 Heavy Biocrude Gas 20 Heavy Biocrude 0 0 10 20 30 40 time (min) (c) Solids Gas Valdez & Savage, Algal Research, under review 22
Reaction of Heavy Biocrude Heavy Biocrude produces Aqueous-phase products, Light Biocrude and H 2, C 1, and C 2 gases yield (wt %) 100 80 60 40 Heavy Biocrude Aqueous-phase Products T = 350 C Solids 1 2 3 Aqueous-phase Products 7 4 9 Light Biocrude 10 8 Heavy Biocrude 5 6 11 Gas 20 Light Biocrude Solids 0 Gas 0 10 20 30 40 time (min) Valdez & Savage, Algal Research, under review 23
Building a Kinetics Model Write & solve governing equations x i = mass fraction of each product dx i dt = ν ijk j x i 1 st order kinetics Estimate rate constants by minimizing objective function Objective Function = x exp. calc. ( i x i ) 2 Used MATLAB, Constrained, non-linear multivariable function Solids 1 2 3 i Aqueous-phase Products 7 4 9 Light Biocrude 10 8 Heavy Biocrude i 5 j 6 11 Gas 24
Model & Exptl. Results for HTL 80 250ºC 80 300ºC 70 60 Solids Aqueous-phase Products 70 60 Solids Aqueous-phase Products yield (wt %) 50 40 30 20 10 Heavy Biocrude Light Biocrude 0 Gas 0 30 60 90 Solids time (min) yield (wt %) 50 40 30 Heavy Biocrude 20 Light Biocrude 10 Gas 0 0 30 60 90 time (min) 80 350ºC 80 400ºC yield (wt %) 70 60 50 40 30 20 Solids Aqueous-phase Products Light Biocrude 10 Heavy Biocrude Gas 0 0 30 60 90 time (min) yield (wt %) 70 60 50 40 30 20 10 Solids Aqueous-phase Products Light Biocrude Gas Heavy Biocrude 0 0 30 60 90 time (min) 25
50 40 Model Predictions Biocrude Yield Prediction 90 75 biocrude yield (wt %) 30 20 10 Brown et al. 3 Faeth et al. 18 Li & Savage 19 0 300 350 400 450 500 550 temperature (ºC) Biocrude yields from liquefaction of Nannochloropsis sp. at 60 min gas yield (wt %) 60 45 30 15 0 0 20 40 60 80 time (min) Gas yields from hydrotherrmal treatment of Nannochloropsis sp. at 60 min Valdez & Savage, Algal Research, 2013 26
Model Predictions High temp, short time gives highest biocrude yields Rapidly heat to high temperature Fast liquefaction Valdez & Savage, Algal Research, 2013 27
Fast Hydrothermal Liquefaction Nannochloropsis sp. 1.5 ml stainless steel batch reactors Thermocouple dummy reactors Setpoint temperatures 300-600 C Reaction times 1, 3, 5 min Quench in cold water 28
Temperature Profile Temperature ( C) 600 500 400 300 200 100 297 C 176 C 593 C 565 C 600 C Setpoint Temperature 283 C 297 C 300 C Setpoint Temperature 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Time (minutes) 29
Total Biocrude Yield (wt.%) Temperature ( C) 600 500 400 300 200 100 66 ± 11 13 ± 7 10 ± 3 14 ± 4 600 C Setpoint Temperature 38 ± 0.5 44 ± 1 300 C Setpoint Temperature 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Time (minutes) Uncertainty given is standard deviation 30
Total Biocrude Yields - 1 minute Biocrude Yield (wt.% d.a.f.) 80 70 60 50 40 30 20 10 0 25 300 350 400 450 500 550 600 Setpoint Temperature ( C) Faeth, Valdez & Savage, Energy & Fuels, 2013 31
Reaction Ordinate Severity index that combines effects of time and temperature 1 Used previously with wood pulping Numerical integration using experimental temperature trajectory 1 T. Rogalinski, T. Ingram, and G. Brunner, e Journal of Supercritical Fluids, 2008, 47, 54 63. 32
Total Biocrude Yield with R 0 Biocurde Yield (wt.% d.a.f.) 90 80 70 60 50 40 30 20 10 0 Fast HTL Unreacted Algae 0 2 4 6 8 10 12 14 16 Log(R 0 ) Faeth, Valdez & Savage, Energy & Fuels, 2013 33
Total Biocrude Yield with R 0 Biocurde Yield (wt.% d.a.f.) 90 80 70 60 50 40 30 20 10 0 Unreacted Algae Fast HTL Conv HTL 0 2 4 6 8 10 12 14 16 Log(R 0 ) Conv. HTL Data from Valdez et al., Biomass and Bioenergy, 2012 34
Biocrude O/C, N/C Ratios Atomic Ratio 0.20 0.18 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0.00 Algae O/C = 0.353 Algae N/C = 0.145 N/C O/C Fast HTL O/C Fast HTL N/C Conv HTL O/C Conv HTL N/C 0 2 4 6 8 10 12 Log(R 0 ) Faeth, Valdez & Savage, Energy & Fuels, 2013 35
Model Compound Approach Chemical details likely to be obscured starting with algae directly Triglycerides Ester Algae Proteins Amino Acid Chlorophyll Phytol Bio-oil Carbohydrates Sugars Specific How do model compounds react individually and interact with each other in HTW? 36
Phenylalanine Ethyl Oleate Protein Lipids 37
Phenylalanine Reaction Pathway [Changi et al., ChemSUSChem (2012)] 38
Ethyl Oleate Hydrolysis Sigmoidal shape - autocatalysis Adding oleic acid increases conversion Catalysis by product (oleic acid) confirmed Effect of Added Oleic Acid Moles Oleic Acid Moles Ethyl Oleate Conversion (240 C, 30 minutes) 0 0.07 ± 0.03 0.25 0.27 ± 0.07 0.5 0.41 ± 0.05 1 0.61 ± 0.09 [Changi et al., Ind.Eng.Chem.Res. (2011)] 39
Phenylalanine + Ethyl Oleate 40
Effect of Adding Ethyl Oleate Phenylethylamine (primary product) yield decreases with added ester Styrene, 2-phenylethanol (2 products) yields increase with added ester Reactions enhanced in presence of ester [Changi et al., ChemSUSChem (2012)] 41
Effect of Adding Phenylalanine Formation of new products - oleic acid amides, phenylacetaldehyde Molar Yield of Phenylacetaldehyde 0.025 0.02 0.015 0.01 0.005 0 At 350 C and 10 min 0.0 0.2 1.0 5.0 Ethyl Oleate : Phenylalanine [Changi et al., ChemSUSChem (2012)] 42
Reaction Network for Binary System [Changi et al., ChemSUSChem (2012)] 43
Reaction Network for Binary System Increased Rates [Changi et al., ChemSUSChem (2012)] 44
Parity Plot for Binary System 45
Insights to Chemistry of Algae Liquefaction Oligomerization in amino acid system at high temperatures Decreases quality of bio-oil Use hydrogenation strategy to prevent oligomers Binary mixtures of amino acids and esters form amides Decreases yield of fatty acid components in bio-oil Adds nitrogen to crude bio-oil Rates of individual reactions increase 46
Summary Hydrothermal Liquefaction (HTL) converts wet biomass into crude bio-oil Reaction network for HTL of algae established Reaction modeling, reactor engineering Fast HTL produces biocrude in higher yield and shorter time than conventional HTL 66 wt.% yield in 1 min. Reaction ordinate unifies results from conventional and fast HTL Model compounds provide insights into HTL chemistry 47
Acknowledgements Peter Valdez, Julia Faeth, Shujauddin Changi NSF EFRI 0937992 EPA, NSF Graduate Fellowships College of Engineering University of Michigan Rackham Graduate School University of Michigan 48