Fractionation of Algal Biomass for Increased Biofuel ... for cost-effective biofuel production ¢â‚¬¢ Advantages

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  • NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

    Fractionation of Algal Biomass for Increased Biofuel Yields and Lower Costs

    Nick Nagle

    Lieve Laurens

    Ryan Davis

    Philip Pienkos

    October 2nd, 2013

  • 2

    Outline

    • Potential for “whole cell” fractionation for cost-effective biofuel production

    • Advantages of targeted fractionation compared to standard process

    • Scale up demonstration to >100 kg of algal biomass into algal biofuel

    • Gallons Gasoline Equivalents (GGE) to make comparisons between fuels and intermediates

    • Techno-economic analysis (TEA) based on pilot scale data to show progress, cost reduction and reduce risk

    Oil

    before after

    Soluble sugars Scenedesmus sp.

  • 3

    Assume national capacity for biomass production at

    1.4 B tons per year (Wigmosta et al. 2011).

    Biomass Fractionation

    336 M tons Lipids (fatty

    acids)

    588 M tons Glucose

    97 M tons Protein (amino

    acids)

  • 4

    Feedstock Composition and Production

    4

    Chlorella sp. Scenedesmus sp. Nannochloropsis sp.

  • 5

    o Varies based on growth/harvest parameters

    o Theoretical yields of combined biofuels process depend on carbohydrate & lipid content

    o Determine best growth/harvest regime

    o Secondary reactions between constituents possible

    Ash Starch Carbohydrates

    (no Starch) Protein Fatty acids

    Scenedesmus sp.

    HP (early) 5.6 6.9 17.4 34.5 6.6

    HC (mid) 1.6 11.6 40.7 9 30.9

    HL (late) 2 7.2 34.3 7.5 40.3

    Chlorella sp.

    HP (early) 4.7 3.3 9.1 40.2 13.0

    HC (mid) 2.7 36.8 5.9 13.1 22.4

    HL (late) 2.6 21.9 5.2 12.7 40.5

    Feedstock Composition and Production

  • 6

    Process and Pathway Overview

    Algal biomass production: Scenedesmus sp.

    - High Carb (HC) - High Lipid (HL) - High Protein (HP)

    Chlorella sp:

    - High Carb (HC) - High Lipid (HL) - High Protein (HP

    Lipid Conversion

    and Upgrading

    Zipperclave prt and

    Fermentation (200-500 g)

    Pilot Scale prt. and

    Fermentation

    Small-scale microwave prt (2-4 g)

    Carbohydrate and Lipid

    Yield

    Carbohydrate and Ethanol

    Yield

    Carbohydrate, Lipid and

    Ethanol Yield

    Techno- economic analysis

    Outputs

    Data Lipids

    Data

  • 7

    Dilute Acid/Base Pretreatment

    Experimental Parameters – CCD Experimental Approach Whole Algae- Non Extracted

    Low High

    Temperature 115o C 180o C

    Time (min) 1 20

    Catalyst conc. (% acid) 0.0 3.0

    Catalyst conc. (% NaOH) 0.0 0.1

    • CEM Explorer Microwave Reactor

    • Automated system w/36-positions

    • 300 watt output

    • Stir bar mixing-rapid heating

    Acid Catalyzed Alkaline Catalyzed

    • Use pretreatment to breach cell wall

    • Tracking both carbohydrate and lipid

    (FAME) release

    Lipid Droplet

  • 8

    Small scale Dilute Acid Microwave Pretreatment

    0

    20

    40

    60

    80

    100

    120

    1%/ 125C/

    10.5 min

    2%/ 145C/1 min

    2%/ 145C/20 min

    % T h e o re

    ca l Y ie ld

    Glucose Yield %

    Lipid Yield %

    0

    20

    40

    60

    80

    100

    1%/ 125C/

    10.5 min

    2%/ 145C/1 min

    2%/ 145C/20 min

    % T h e o re

    ca l Y ie ld

    Glucose Yield %

    Lipid Yield %

    High Lipid Chlorella

    High Lipid Scenedesmus

    • Developed and demonstrated single-step dilute acid pretreatment to hydrolyze polysaccharides to glucose without enzymes or production of inhibitors

    • Hexane extraction of pretreated solids provided good lipid yields

    • Demonstrated carbohydrate release in both Chlorella sp. and Scenedesmus sp., cultivated under high lipid and high carbohydrate regimes

    High Carb Scenedesmus fractionation parameter optimization

  • 9

    Impact of Process Sequence

    Fatty Acids in Extract (g/kg biomass)

    Fatty Acid Recovery (%)

    Glucose in Liquor (g/kg biomass)

    Glucose Recovery (%)

    High Protein SD 9 13 129 94

    High Carb SD 19 7 290 83

    High Lipid SD 20 6 244 94

    Fatty Acids in Extract (g/kg biomass)

    Fatty Acid Recovery (%)

    Glucose in Liquor (g/kg biomass)

    Glucose Recovery (%)

    High Protein SD 53 78 106 77

    High Carb SD 236 97 254 73

    High Lipid SD 268 76 186 72

    Extraction >Pretreatment

    Pretreatment > Extraction

    Scenedesmus sp.

    [Same result seen with Chlorella biomass]

  • 10

    Morphological Changes

    HP

    HC

    HL

    Scenedesmus sp. Chlorella sp.

  • 11

    Fermentation Results-Shake Flasks

    0

    20

    40

    60

    80

    100

    120

    0 5 10 15 20 25 30

    % Y ie ld

    Time (Hr)

    HPCZ

    HLCZ

    HCCZ

    0

    20

    40

    60

    80

    100

    0 5 10 15 20 25 30

    % Y ie ld

    Time (hr)

    HPSD

    HLSD

    HCSD

    • Fermentation completed at 6-21 hr. • HMF concentration ranged from 0.5-1.5 g/L • No furfural measured • Shake flask setup using neutralized prt

    hydrolyzates • Yeast peptone addition at 0.5X (3-4g/L) • Yeast (D5a) fermentation organism • No pH control

    Scenedesmus sp.

    Chlorella sp.

    Dilute acid pretreatment at 100 g (dwt.) scale in Zipperclave reactor.

  • 12

    Fuel Yields Per Ton of Biomass

    HP SD HC SD HL SD HP CZ HC CZ HL CZ

    Combined fermentable sugars (kg) 193 324 220 5 234 182

    Ethanol yield (%) 82 100 81 73 91 100

    Ethanol-fermentation (kg) 81 165 91 2 109 93

    Ethanol (Gallons) 28 55 30 1 36 31

    Gasoline Gallon Equivalent (GGE) 19 36 20 0 24 20

    Btu equivalent (x10e3) 2206 4224 2329 43 2778 2378

    Fatty Acids (FAME in ext) (kg) 48 214 243 46 43 163

    Hydrocarbon (kg) 37 167 189 36 33 127

    Diesel Equivalent (gallon) 13 57 65 12 11 43

    Btu equivalent (x10e3) 1573 7005 7954 1514 1395 5342

    Total Fuel Energy (x10e3 Btu) 3779 11229 10283 1557 4173 7721

    Total GGE 32 97 88 13 36 66

  • 13

    Solid/Liquid Separation (NREL)

    Sugar Fermentation (NREL)

    Biomass Production (ASU)

    Integrated Scale-Up Demonstration

    Pretreatment (NREL) Solids Lipid Extraction (NREL)

    Nutrient Recycle

    Protein Fermentation (SNL)

    Protein

    Lipids

  • 14

    Integrated Algal Biomass Processing

    Outcome:

    • High carb Scenedesmus sp. (highest

    biofuel potential and shortened growth)

    • Dilute acid pretreatment > solids liquid

    separation > hexane extraction

    • Established biofuel potential of fractions:

    • Lipid yields based on FAME analysis

    • Ethanol fermentation of carbohydrates

    • Biobutanol fermentation of protein fraction

    • Established value of ethanol fermentation

    broth for nutrient recycle

  • 15

    Fermentation Results- Demonstration Scale

    0

    20

    40

    60

    80

    100

    0 5 10 15 20 25 30

    Et h an

    o l %

    Time hr.

    Final Yield (%)

    1 Based on initial composition 2 Based on 0.51g EtOH/g glucose 3 Recovery based on initial composition

    Key Findings

    • Demonstrated scalable process

    from mg to g to kg scale

    • Minimal fermentation inhibitors

    produced from dilute acid

    pretreatment

    • Carbohydrate release and

    FAME recovery demonstrated

    • Ethanol fermentation is a good

    proxy for other fuels/chemicals

    • Pretreatment of algae followed

    by extraction offers a new

    process paradigm.

    Glucose1 Ethanol2 Lipid3

    68 80 45-73

  • 16

    Theoretical Yields HP SD HC SD HL SD HP CZ HC CZ HL CZ

    Total Carbohydrates 220 435 356 112 378 246

    Glucose/Mannose 190 420 343 52 333 214

    Ethanol 97 214 175 27 170 109

    Ethanol (gallon) 32 72 59 9 57 36

    Gasoline equivalent (gallon) 21 47 39 6 37 24

    Btu equivalent (x10e3) 2478 5481 4476 678 4344 2787

    Total FAMEs 60 240 371 118 200 367

    Hydrocarbon 47 187 289 92 156 286

    Diesel equivalent (gallon) 16 64 99 31 53 98

    Btu equivalent (x10e3) 1959 7865 12139 3858 6559 12021

    Amino Acids 266 69 60 304 104 82

    Butanol 106 28 24 122 42 33

    Butanol (gallon) 34 9 8 39 13 11

    Gasoline equivalent Btu equivalent (x10e3) 3425 890 775 3914 1341 1057

    Total fuel energy (x10e3 Btu) 7861 14236 17390 8451 12244 15865

    Total GGE/short ton 68 123 150 73 105 137

    Algal Biofuel Potential