effect of heavy metal contamination on microalgae growth...
TRANSCRIPT
Effect of heavy metal contamination on microalgae growth and conversion to
biofuel through acid catalyzed conversion
Derek Hess, Katerine Napan, Brian McNeil, Jason C.
Quinn
Mechanical and Aerospace Engineering Utah State University 1
Acknowledgements
2
• Utah Water Research Laboratory
– Joan McLean – Tessa Guy – Joe Stewart
• Research Students – Eric Torres – Laura Birkhold – Christine Inkley – Mike Morgan – Hailey Summers
BioEnergy Center
TRANSESTERIFICATION
Outline
3
0% 5%
10% 15% 20% 25% 30% 35% 40%
LIPID YIELD
PRODUCTIVITY
0%
20%
40%
60%
80%
100%
120%
As Cd Co Cr FATE OF METALS
PRODUCTION PROCESS
RESULTS
CO2
PHOTOBIOREACTORS
ALGAE
BIOFUEL
LEA COAL POWER PLANT
HEAVY METALS &
ACID CATALYZ
ED
SUPERCRITICAL
METHANOL
‹#›
Growth Setup
5
14 Heavy metals used Nannochloropsis salina
1X
Element Fly Ash PBR
(mg metal·kg-1) (mg metal * L-1) As 391.0 0.078 Cd 76.0 0.015 Co 79.0 0.016 Cr 651.0 0.130 Cu 655.0 0.131 Hg 49.5 0.010 Mn 745 0.149 Ni 1270.0 0.250 Pb 273.0 0.054 Sb 203.0 0.041 Se 49.5 0.010 Sn 18.8 0.004 V 565.0 0.113 Zn 2200.0 0.440
Acid Catalysed Conversion
• Demonstrated on small and medium scale sys.
• 6 mL H2SO4, 294 mL methanol, 30 g biomass
• 6 hr. reaction at 62 °C 6
H2SO4 + Methanol + Heat
Microalgae
Biodiesel & CHCl3 Extraction
Biodiesel
in situ Transesterificati
on
Chloroform Distillation
Wahlen et al., Bioresource Technology (2011).
Supercritical Methanol Conversion
• Demonstrated on a small scale system
• 100 mL methanol, 10 g biomass • 1.5 hr. reaction at 250 °C 7
Biodiesel Extraction Supercritical Meth.
Transesterification Methanol + Heat
Microalgae
Chloroform Distillation
TRANSESTERIFICATION
Growth Results
8
PRODUCTION PROCESS
CO2
PHOTOBIOREACTORS
ALGAE
BIOFUEL
LEA COAL POWER PLANT
HEAVY METALS &
ACID CATALYZ
ED
SUPERCRITICAL
METHANOL
0% 5%
10% 15% 20% 25% 30% 35% 40%
LIPID YIELD
PRODUCTIVITY
0%
20%
40%
60%
80%
100%
120%
As Cd Co Cr FATE OF METALS
RESULTS
0
5
10
15
20
25
30
35
0 1 2 3 4 5 6 7
OD
750
Time (days)
0 1 2 3 4 5 6 7 8 9
10
0 1 2 3 4 5 6 7
Gro
wth
den
sity
(g/L
)
Time (days)
Biomass Productivity
Productivity and Lipid Results
9
• Average productivity: – Control: 1.1 g L-1 d-1
– Metals : 0.6 g L-1 d-1
Combined impact: 56% decrease in lipid production
• Lipid Yield: – Control: 38.8% ± 0.59% – Metals : 31.58% ± 0.48%
0%
5%
10%
15%
20%
25%
30%
35%
40%
Per
cent
Lip
id C
onte
nt
Lipid Yield
0%
20%
40%
60%
80%
100%
120%
140%
As Cd Co Cr Cu Hg Ni Pb Sb V
ICPMS: Fate of Metals Significant sorption of heavy metals to the biomass.
Media reuse plausible
10 * Metals Se and Sn did not fall within quality control ** Metals Mn and Zn removed due to contamination
TRANSESTERIFICATION
Acid Catalyzed Results
11
PRODUCTION PROCESS
CO2
PHOTOBIOREACTORS
ALGAE
BIOFUEL
LEA COAL POWER PLANT
HEAVY METALS &
ACID CATALYZ
ED
SUPERCRITICAL
METHANOL
0% 5%
10% 15% 20% 25% 30% 35% 40%
LIPID YIELD
PRODUCTIVITY
0%
20%
40%
60%
80%
100%
120%
As Cd Co Cr FATE OF METALS
RESULTS
Acid Catalysed Results
12
• Impact of metals on extraction: – Control: 80% ± 7% – Metals : 89% ± 7%
• Impact on Lipid Profile: – Change in Profile – Metals decrease lipid content
0%
20%
40%
60%
80%
100% Recovery Efficiencies
0% 5%
10% 15% 20% 25% 30% 35% 40%
14:0 16:0 16:1 18:0 18:1 18:2 20:5 FAME
Lipid Profiles
Transesterification impact: 9% increase in lipid recovery efficiency Combined impact (productivity & recovery): 51% decrease in lipid
production
ICPMS: Fate of Metals • ICPMS analyses of the biodiesel, and all by-
products
13 * Metals Mn and Zn removed due to contamination
0% 10% 20% 30% 40% 50% 60% 70% 80% 90%
100% 110%
As Cd Co Cr Cu Ni Pb Se Sb V Biodiesel LEA Methanol / Water Losses Other
** Metals Sn and Hg conc. below ICPMS detection limit
Majority of heavy metals found in LEA and Methanol / Water by-products.
Minimal Biodiesel Contamination
TRANSESTERIFICATION
Supercritical Methanol Results
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PRODUCTION PROCESS
CO2
PHOTOBIOREACTORS
ALGAE
BIOFUEL
LEA COAL POWER PLANT
HEAVY METALS &
ACID CATALYZ
ED
SUPERCRITICAL
METHANOL
0% 5%
10% 15% 20% 25% 30% 35% 40%
LIPID YIELD
PRODUCTIVITY
0%
20%
40%
60%
80%
100%
120%
As Cd Co Cr FATE OF METALS
RESULTS
Supercritical Methanol Results
15
• Impact of metals on extraction: – Control: 98% ± 8% – Metals : 100% ± 3%
• Impact on Lipid Profile: – Change in Profile – Metals shifted lipid content
Combined impact (productivity & recovery): 55% decrease in lipid production
0%
20%
40%
60%
80%
100%
Recovery Efficiencies
0%
5%
10%
15%
20%
25%
30%
35%
14:0 16:0 16:1 18:0 18:1 18:2 20:5
FAME
Lipid Profiles
Transesterification impact: 2% increase in lipid production efficiency
Concentrated Growths
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Nannochloropsis salina Scenedesmus Obliquus
• Light intensity: 1000 µmol m-2 s-1 • Salt water species • 14 heavy metals
• Light intensity: 200 µmol m-2 s-1 • Fresh water species • 10 heavy metals
All metals conc. limit productivity Metals conc. over 1X limit productivity
0 1 2 3 4 5 6 7 8 9
10
Har
vest
Den
sity
(g/L
)
Metals Concentration 0X 1X 2X 5X 10X
0 1 2 3 4 5 6 7 8 9
10
Har
vest
Den
sity
(g/L
)
1X 0X 5X 2X 10X Metals Concentration
Conclusion • Metals negatively impact system
– Productivity decrease of 56% – Acid Catalyzed Biodiesel yield decrease of 51% – Supercritical Methanol Biodiesel yield decrease of 55%
• End Fate – Biomass sorbes majority of metals – Media reuse plausible – By-products (LEA and Methanol/Water) contain majority of metals – Minimal Biofuel contamination
• Metals impact processes and productivity – Metals at any concentration negatively impact productivity – Metal impact of biofuel conversion varies with conversion type
17
Future Work
• Supercritical Methanol – Fate of Heavy Metals work (ICPMS)
• Downstream Processing – Biochemical Methane Potential Testing – Fermentation
• Modeling – Life Cycle Analysis
18
