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