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.

Diluted acid pretreatment for an integrated microalgae bio-refinery to produce lipid- and

carbohydrate-based biofuels

Tao Dong, Lieve Laurens, Nick Nagle, Stefanie Van Wychen,

Nicholas Sweeney, Philip Pienkos

Algae Biomass Summit

San Diego, California

Sep. 30, 2014

Introduction

• Integrated bio-refinery process for multiple products recovery from algal biomass

• Response of carbohydrate and lipids recovery under diluted acid pretreatment

• Biomass morphological changes in cellular structure after pretreatment

• Conclusion

Biomass fractionation for fuels & value-added chemicals

Proteins

Ethanol

Succinic acid

FarneseneFermentation

Blend stocks

Aviation Fuel

Green DieselHDO/HI

Lipids

ADfermentation, etc

Animal feed

Isobutanol

Bio-plastics

Methane

Proteins

Scheme for integrated algal biomass processing

Fuel HL NC HL SD

Fatty acids (FAME)(% DW)

57.3 38.6

Diesel equivalent (gallon/ton)

138.4 93.2

Fermentable Sugars(% DW)

10.9 39.4

Ethanol(gallon/ton)

13.8 59.0

Total fuel energy (103 Btu/ton)

18060 15965

Total GGEper ton biomass (GGE/ton)

155.6 137.5

A-100Feedstock

A-200Pretreatment

A-300S/L

Separation

A-500Fermentation

A-600EtOH

Recovery

A-325Extraction

A-375Protein Extract.

A-400Butanol Ferm

A-350Lipid

Recovery

A-360AnaerobicDigestion

A-450Butanol

Recovery

Algae Water Acid Steam

Slurry Liquor

Media KOH

Solids Liquor

Hexane

Liquor

Solids

Solids

Solids NaOH

Algal feedstock production at ASU

Using a Combination of PBR’s and Open Raceways

Three Production Strains:• Chlorella sp.• Scenedesmus sp. • Nannochloropsis sp.

Three Growth Regimes:•High Protein (Early)•High Carbohydrate(Mid)•High Lipid (Late)

Feedstock Composition and Rates of Lipid Accumulation

Chlorella sp. Scenedesmus sp.Nannochloropsis sp.

Early (high protein)Mid (high carbohydrate)Late (high lipid)

Dilute-acid pretreatment to release lipid & carbohydrate

• CEM Explorer Microwave Reactor• Automated system w/36-positions• 300 watt output• Stir bar mixing• Rapid heating

Aci

d

Temperature

145 ºC, 2% H2SO4

• Track both fatty acid and carbohydrate release

• Central Composite Design

1751170%

4.1%

FFA

TAG

FFA

TAG

FFA

TAG

HC CZ HL CZ

HC SD HL SD

HL NC

Response of lipids recovery from different strains

SD

CZ

NC

Mid HC Late HL

Element HL CZ HC CZ HL SD HC SD HL NC

Carbon 76.83 77.42 77.53 76.61 76.87

Hydrogen 11.74 11.54 12.00 11.91 11.77

Nitrogen 0.04 0.05 0.03 0.10 0.09

Oxygen 11.86 11.37 11.04 11.93 11.96

Sulfur 0.004 0.006 0.005 0.026 0.036

Phosphorus <0.001 <0.001 <0.001 0.001 0.039

80%

90%

100%

80%

90%

100%

MicroalgaeGlucose

Galactose/Rhamnose

Mannose

% (based on total carb)HCNC 69.6 21.4 8.9HLNC 72.5 18.3 9.2

HCCZ 80.1 17.0 2.9HLCZ 84.9 12.1 3.0

HCSD 81.7 3.8 14.5HLSD 75.9 3.3 20.8

NC: LaminarinCZ: StarchSD: Glucomannan

Response of carbohydrate recovery from different strains

SD

CZ

NC

Mid HC Late HL

Energy yield from integrated algal biomass processing

SD CZ NC

mid late late late

Gasoline equivalent

(gal/ton)** 34 27 23 8

Btu equivalent

(x10e3) 3959 3156 2700 948

Diesel equivalent

(gal/ton) 37 84 50 111

Btu equivalent

(x10e3) 4541 10311 6171 13605

Total fuel energy

(x10e3 Btu/ton) 8500 13467 8871 14553

Total GGE

(GGE/ ton) 73 116 76 125

SD

CZ

NC

Mid HC Late HL

Biomass morphological changes in cellular structure

HL NC

HL CZ

HC SD

Conclusion

• Integrated microalgae biomass processing is able to recovery lipids and fermentable sugar.

• Acid concentration and temperature have combined effects for lipids and sugar recovery.

• The response of microalgae biomass to pretreatment is strain-dependent

• Achieve >100 GGE/ton for the late harvest Scenedesmussp. and Nannochloropsis sp. strains.

Acknowledgements

NREL

Deborah Hyman

Kelsey Ramirez

Robert Sebag

Paris Spinelli

Chandler Ridler

Earl Christensen

ASU:

John McGowen (ASU)

Thomas Dempster (ASU)

BETO

THANKS! QUESTIONS?

% DW FAME Lipids ash Carbohydrates Glucose Xylose Galactose Arabinose Mannose ProteinHP NC 12.3 14.2 8.9 5.1 0.0 2.9 0.0 0.9 32.7HC NC 25.6 13.6 11.1 7.8 0.0 2.4 0.0 1.0 23.1HL NC 57.3 5.1 10.9 7.9 0.0 2.0 0.0 1.0 9.4

HP SD 9.1 4.5 16.9 7.5 0.0 2.8 0.0 6.6 46.3HC SD 17.0 1.8 49.7 40.6 0.0 1.9 0.0 7.2 17.4HL SD 38.6 2.2 39.4 29.9 0.0 1.3 0.0 8.2 7.8

HP CZ 12.1 6.7 11.1 3.6 0.5 5.6 0.5 1.0 43.2HC CZ 15.0 4.4 35.7 27.8 0.5 5.9 0.5 1.0 24.0HL CZ 23.1 5.3 38.0 31.5 0.5 4.5 0.4 1.1 15.2

Integrated processing of microalgae biomass

Hydrodeoxygenation (HDO) of Algae Oil

• Left: high-lipid Chlorellaoil at 25 wt% in hexane

• Right: Chlorella oil HDO product over Pd/C– 450 °C, 1300 psi H2

– Residence time ~2 min; LHSV = 1 hr-1

– GC-MS: primarily C15 and C17 n-alkanes

Before After