Progress and Perspectives of Large Scale Algae Biomass Harvesting: A Case Study at the ATP3 Testbed

Xuezhi Zhang, John McGowen, Milton Sommerfeld and Pierre Wensel

Arizona Center for Technology and Innovation (AzCATI)Arizona State University

Sep 29 – Oct 2, 20142014 Algae Biomass Summit, San Diego

Outline

Introduction

Challenges in algae harvesting

Progress of large scale algae harvesting

Algae harvesting using membrane filtration

Algae harvesting using sedimentation and DAF

Algae harvesting using centrifugation

Techno- economic model analysis for large scale algae harvesting

Perspectives of large scale algae harvesting

Influence of the algae cell surface properties and media characteristics on the algae harvesting using flotation

Growth inhibition of culture media recycling

Qualities of the harvested biomass

CO2 Nutrients

Cultivation Harvesting

Biodiesel

Pharmaceutical/NutraceuticalBioproducts

Production of Algae Biomass, Biofuels and Bioproducts

Extraction/conversion

Water

4

Challenges in Algae Harvesting

• Similar density to water (1010 - 1030 kg m-3)

• Small size (2-50 µm diameters)

• Diversity of algal cell and culture medium characteristics

-Huge volume of water needs to be processed for one gallon biodiesel

Parameter Value

Algae concentration (g L-1) 1

Oil content (%) 30%

Neutral lipid (%) 50%

Extract efficiency (%) 80%

Biodiesel density (g L-1) 900

Algae dry biomass (kg) 28.4

Water volume needed (L) 28,388

-Difficult to separate algae from water

Algal Mass Cultivation at the ATP3 Testbed

15,000 L 100,000 L

1,500 L each 660 L each

Membrane filtrationDissolved air flotation

Centrifugation

Sedimentation

G

Algae Harvesting and Dewater Technologies at the ATP3 Testbed

Freeze dryer

Algae Harvesting using Membrane Filtration

Before Harvesting

AlgaeConcentrate

Filtrate

Membrane algae harvesting unit (Litree)

Pore size: ~10 nm

Feed, concentrate and permeate collectedfor membrane harvesting

waterQ, ρi, Xi

QC, c

ρ, X

Photobioreactor

ρH, XH

Membrane

PermeateQ-QH, ρe, Xe

RQ

ρ, X

QH

CO2

QD

SEM Images of Clean and Fouled Membrane

After algae cake layer buildupClean membrane

3500 3000 2500 2000 1500 1000 500

0.00

0.01

0.02

0.03

0.04

0.05

Ab

sorb

ance

Wave number (cm-1)

Virgin membrane

C-OH Polysaccharides

-NH

3500 3000 2500 2000 1500 1000 500

0.00

0.01

0.02

0.03

0.04

0.05

C-N

Ab

sorb

ance

Fouled membrane

C=O

Zhang et al. Algal Research 2013

Air assisted backwashing

with air scouring

Hollow fiber

(inside out)

Algae cake layer

Algae suspension

in fiber

0 10 20 30 40 50 60 70 80 90 1000

20

40

60

80

100

120

Flu

x (

L m

-2 h

-1)

Time (min)

Air assisted backwash with air scour

Air assisted backwash without air scour

0 10 20 30 40 50 60 70 800

20

40

60

80

100

120

Flu

x (

L m

-2 h

-1)

Time (min)

0.17 m s-1

0.09 m s-1

0.01 m s-1

0 10 20 30 40 50 60 70

0

20

40

60

80

100

120

Flu

x (

L m

-2 h

-1)

Filtration time (min)

10 min

15 min

30 min

60 min

010

020

030

040

050

00

20

40

60

80

100

120

NaClO (mg L-1)

Flu

x (

L m

-2h

-1)

Optimize Operation Conditions of Membrane Harvesting

Operation optimization

Zhang et al. Bioresource Technology 2010Zhang et al. Separation and Purification Technology 2009

Production Scale Membrane Algae Harvesting

Membrane area: 30 m2

Permeate flow : 19 L/m2 hBiomass recovery: 85%Solid content : 4-6%Medium recycle： 90%

Concentrate Permeate

Membrane algae harvesting units (Litree)

15,000 L

Recycled culture media

Modeling of Membrane Algae Harvesting

0 60 120 180 240 300 360 420 480 540 600

20

40

60

80

100

120 Experimental

Model

Flu

x (

L m

-2 h

-1)

Filtration time (min)Zhang et al. Bioresource Technology 2010

Algae Harvesting using Sedimentation

Sedimentation algae harvesting unit (Integrated Engineers)

dp, ρp, Np df, ρf, vf, Nf

Before

Harvesting

Algae

Concentrate

Effluent

Flow rate: 5-8 gpmBiomass recovery: 80%Solid content: <3%

Lamella

Algae Harvesting using Dissolved Air Flotation

dp, ρp, Np

db, ρb, vb, Nb

dfb, ρfb, vfb, Nfb

df, ρf, vf Nf

DAF algae harvesting unit (World Water Works)

Flow rate: 3-5 gpmBiomass recovery: ~75%Solid content: 6-8%

Algae Harvesting using Dissolved Air Flotation

Pond Before screen Final product0.0

2.0

4.0

6.0

8.0

10.0

Soli

d c

on

ten

t (%

)

Other

Penetrate screen

Effluent

Settled

9%

4%

13%

4%

70%

Harvested

0 100 200 300 400 500 600 700

0.0

0.1

0.2

0.3

Dry

wei

gh

t in

res

idu

al (

g L

-1)

Time (min)

Algae Concentration in the DAF Effluent

Solid Contents of DAF Harvested Algae Biomass

Biomass mass balance

Algae Harvesting using Dynamic Settler/Evodos Centrifuge

Evodos Centrifuge

500 1000 1500 2000 2500 3000 35000

20

40

60

80

100

Sep

arat

ion

Eff

icie

ncy

(%

)

Flow rate (L/h)

Scenedesmus sp., Pond

Chlorella sp., Pond

Nannochloropsis sp., Pond

Nannochloropsis sp.

Chlorella sp.

Scenedesmus sp.

Evodos centrifuge

500 1000 1500 2000 2500 3000 35000

20

40

60

80

100

Sep

arat

ion

Eff

icie

ncy

(%

)

Flow rate (L/h)

Scenedesmus sp., Pond

Chlorella sp., Pond

Nannochloropsis sp., Pond

Nannochloropsis sp. PBR

Input goal, VRF

or time

Harvesting

technologies & key

parameters

Calculate efficiency, cost

Optimized harvesting

process

Input algae

characteristics

Techno- economic Model Analysis for Large Scale Algae Harvesting

Summary of Algae Harvesting Technologies

Table TitleParameters Sedimentation Dissolved Air

flotationMembrane

Filtration

Centri-fugation

Process illustration

Concentration factor <15 10~30 5~20 >100

Separation efficiency >90% >85% ~100% >80%

Biomass recovery ~80% ~75% ~85% ~75%

Solid content of harvested

biomass

<3% 6-8% 4-6% >20%

Readiness of culture medium

reuse

Need further

treatment

Need further

treatment

Ready to reuse Need further

treatment

Quality of algae biomass

harvested

Coagulant

contamination

Coagulant

contamination

No

contamination

No

contamination

Cells may break

G

Based on the harvesting of Nannochlorpsis sp, with a process flow of 500 L/h

Perspectives of large scale algae harvesting - 1) Factors Affecting DAF Algae Harvesting

0 100 200 300 400 500 600

0

20

40

60

80

100

Har

ves

tin

g e

ffic

ien

cy (

%)

Coagulant / Algae Dry Weight (mg g-1)

Chitosan Al3+ Fe

3+ CTAB

0 20 40 60 80 1000

20

40

60

80

100

Exponential phase

Stationary phase

Declining phase

Harv

est

ing e

ffic

iency (

%)

Al3+

/Algae dry weight (mg g-1)

0 10 20 30 40 50 60 70 80 90

0

20

40

60

80

100

Haematococcus sp.

Scenedesmus sp.

Chlorella sp.

Har

ves

tin

g E

ffic

ien

cy (

%)

Al3+

(mg g-1)

Influence of growth phases

Influence of coagulant

Influence of algal species

Characterize Algal Cell Surface Functional Groups at Different Growth Phases of Chlorella sp.

-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

pH

0.1 M NaOH (mL)

0 2 4 6 8 10 120.0

0.1

0.2

0.3

0.4

0.5

A

Co

nce

ntr

atio

n (

mm

ol

g-1

)

Culture Time (day)

Carboxyl

Phosphate

Amine/hydroxyl

Declining Exponential Stationary

Zhang et al. Bioresource Technology 2012

Influence of Surface Functional Group on the Harvesting of Chlorella sp.

0 500 1000 1500 2000

20

40

60

80

100

Exponential phase, DOM removed

Stationary phase, DOM removed

Declining phase, DOM removed

Harv

est

ing e

ffic

iency

(%

)

Al3+

/Functional group (mg mmol-1)

0 500 1000 1500 2000

20

40

60

80

100

Exponential phase, DOM removed

Stationary phase, DOM removed

Declining phase, DOM removed

Exponential phase

Harv

est

ing e

ffic

iency

(%

)

Al3+

/Functional group (mg mmol-1)

0 500 1000 1500 2000

20

40

60

80

100

Exponential phase, DOM removed

Stationary phase, DOM removed

Declining phase, DOM removed

Exponential phase

Stationary phaseHarv

est

ing e

ffic

iency

(%

)

Al3+

/Functional group (mg mmol-1)

0 500 1000 1500 2000

20

40

60

80

100

Exponential phase, DOM removed

Stationary phase, DOM removed

Declining phase, DOM removed

Exponential phase

Stationary phase

Declining phase

Harv

est

ing e

ffic

iency

(%

)

Al3+

/Functional group (mg mmol-1)

Zhang et al. Bioresource Technology 2012

Perspectives of large scale algae harvesting - 2) Reduced Growth in the Recycled Media

0 2 4 6 8 1012 0 2 4 6 8 1012 0 2 4 6 8 1012 0 2 4 6 8 10120.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

2.7

3.0

Dry

wei

gh

t (g

L-1

)

Time (d)

32 mg/L N, fresh

32 mg/L N, recycled

0 2 4 6 8 10 12

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

Dry

Wei

gh

t (g

L-1

)

Time (d)

Fresh, N 32 mg/L

Recycled, N 32 mg/LN

0 2 4 6 8 1012 0 2 4 6 8 1012 0 2 4 6 8 1012 0 2 4 6 8 10120.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

2.7

3.0

Dry

wei

gh

t (g

/L)

Time (d)

64 mg/L Recycled

64 mg/L Fresh

0 2 4 6 8 10 120.0

0.5

1.0

1.5

2.0

2.5

3.0

Dry

Wei

gh

t (g

L-1

)

Time (d)

Fresh, N 64 mg/L

Recycled, N 64 mg/LN

100000 10000 1000 100

0.0

2.0

4.0

6.0

8.0 Culture Blank

Recycled medium

Res

po

nse

(m

V)

Molecular Weight (Dalton)250 300 350 400 450 500 550 600

250

275

300

325

350

375

400

EX

(nm

)

EM (nm)

0

800

1600

2400

3200

4000

4800

5600

6400

7200

8000

Identification of Growth Inhibitors in the Recycled Media

5000 4500 4000 3500 3000 2500 2000 1500 1000 500 00.0

0.2

0.4

0.6

0.8

1.0

1.2

Abso

rben

ce

Wavelength Number, cm-1

Culture Blank

Recycling Culture

Perspectives of large scale algae harvesting - 3) Quality of Harvested Biomass and Culture Media

separated

Centrifuge Chitosan Mg Al Fe

0

2

4

6

60

80

100

120

140

Met

al C

on

ten

t (m

g g

-1) Ca

Mg

Al

Fe

*

(c) Biomass washed with 0.1 M HCl

Centrifuge Chitosan Mg Al Fe

0

2

4

6

60

80

100

120

140

Met

al C

on

ten

t (m

g g

-1) Ca

Mg

Al

Fe

(b) DAF harvested biomass

*

*

*

No coagulant Chitosan Mg Al Fe

0.0

2.0

4.0

6.0

8.0

10.0

(a) DAF separated media

*

*

Met

al C

on

cen

trat

ion

(m

g L

-1)

Ca

Mg

Al

Fe

0 100 200 300 400 500

0

20

40

60

80

100

Mg2+

Chitosan

Al3+

Fe3+H

arv

esti

ng

eff

icie

ncy

(%

)

Coagulant / Algae Dry Weight (mg g-1)

Summary

Huge amount of water needs to be processed for algae harvesting. Economic and efficient algae harvesting consist of volume reduction process and dewateringprocess

Algal strain, growth conditions, and the usages of harvested biomass needs to be considered when select the harvesting method

Qualities of the harvested biomass, and culture media recycling needs to be considered

Techno-economic model helps to guide the selection of algal harvesting technologies.

Acknowledgements

Dr. Qiang Hu

Dr. Milton Sommerfeld

Dr. John McGowen

Dr. Thomas Dempster

Dr. Yongsheng Chen

Dr. John Hewson

Dr. Mark Edwards

Dr. Danxiang Han

Dr. Peter Zemke

Dr. Wei Chen

Dr. Yingchun Gong

Dr. Wen Zhang

Zixuan Hu

Pasquale Amendola

Wei Zhang

Monica Reynoso

Michael BellefeuilleThis work funded in part by DOE Awards EE0003372 and EE0005996