enhancing performance and assaying nutrient recycling...
TRANSCRIPT
Pavlo Bohutskyi, Ph.D. CandidateDepartment of Geography & Environmental Engineering,
Johns Hopkins University, Baltimore, MD
Wednesday, October 1, 20148th Annual Algae Biomass Summit
San Diego, CA, USA
Enhancing Performance and Assaying Nutrient Recycling Potential for a Sequential Photoautotrophic-Heterotrophic Algal Biofuel Production System
Presented at 8th Annual Algae Biomass Summit September 29 – October 2, 2014 | San Diego, CA, USA
Lipid Content and Biomass Conversion to Energy
High lipid content is essential
Conversion of Lipid Extracted Algae(LEA) to energy is important
biodiesel vs. anaerobic digestion (methane) vs. combined
Fertilizer Demand for Algal Fuel Production
A – Pate et al. (2011) Resource demand implications for US algae biofuels production scale-up. Applied Energy 88/10:3377–3388
Nutrient Recycling is Possible and Required
• Food production and prices
• Only C and H are part of fuel
Fertilizer demand for 20 BGY ( ~6% of US liquid fuel consumption)A
Algal biomass 70-170 M mt/yr
Nitrogen 6.1-15 M mt/yr
Phosphorus 0.8-2.1 M mt/yr
Fertilizer demand for 20 BGY ( ~6% of US liquid fuel consumption)A
Algal biomass 70-170 M mt/yr
Nitrogen 6.1-15 M mt/yr 44-107% of US use in 2006
Phosphorus 0.8-2.1 M mt/yr 20-50% of US use in 2006
Presentation Outline
Part 1. Description of the mixed trophic system
Part 2. Fate of nutrients and their availability for recycling with spent medium
Part 3. Anaerobic digestion (AD) of LEA for methane production and nutrient recovery from algal
air/CO2
air/CO2
glucose
CO2
algal
culture
conce
ntr
ated
alg
ae
heterotrophic
spen
t g
row
th
med
ium
photoautotrophic
1 2 3 4
pH dO2
A750 Temp.
NaOH
air
centrifugeaseptic conditions
lipid-rich
algae
0.025L
800L15cm(depth)
0.25L 2L 40L 5L
nutrients
nu
trie
nts
nu
trie
nts
nu
trie
nts
Mixed Trophic Algal Cultivation Process
• Microalga: Auxenochlorella (formerly Chlorella) protothecoides UTEX 25
• Phototrophic Medium: minerals, ammonium chloride (0.5 g/L) as nitrogen source
• Heterotrophic Medium: minerals, glucose maintained at 20 g/L, no nitrogen
• Centrifugation: stacked-disc centrifuge
*Growth medium: 1.44 g K2HPO4, 0.72 g KH2PO4, 50 mg Tetrasodium EDTA, 20 mg MgSO47H2O, 10 mg CaCl22H2O, 10 mg FeCl36H2O, 5 mg H3BO3, 1.25 mg ZnSO47H2O, 0.38 MnSO4H2O, 0.25 mg CoCl26H2O, 0.25 mg Na2MoO42H2O, 0.08 mg CuSO45H2O. NH4Cl (0.5 g/L).
air/CO2
air/CO2
glucose
CO2
algal
culture
conce
ntr
ated
alg
ae
heterotrophic
spen
t g
row
th
med
ium
photoautotrophic
1 2 3 4
pH dO2
A750 Temp.
NaOH
air
centrifugeaseptic conditions
lipid-rich
algae
0.025L
800L15cm(depth)
0.25L 2L 40L 5L
nutrients
nu
trie
nts
nu
trie
nts
nu
trie
nts
55
Photoautotrophic Step Heterotrophic StepAseptic Conditions
Results: Photoautotrophic Cultivation
Condition Unit Step 1 Step 2 Step 3Step 4 (bag)
Step 5 (pond)
Starting density
g/L <0.03 0.06 0.05 0.07 0.07
Final density
g/L 0.69 0.37 1.08 1.49 0.28
Duration days 1.78 0.96 6.1 6.26 5.01
Total
lipids% dw 15
Results: Heterotrophic Cultivation
Phototrophically grown non-stressed A. protothecoides has unacceptably low culture density and lipid content (15 %dw)
A second heterotrophic stage boosts the biomass concentration over 115 g/L and lipid content over 55%
Aseptic conditions are not essential for last steps of cultivation (including heterotrophic stage)
Part I: Conclusions
Nutrient Consumption in the Photoautotrophic Growth Medium (Pond)
Initial medium concentration
Final medium concentration
Nutrient Consumption in the Heterotrophic Growth Medium (Fermenter)
growth medium – red circles; µg/L or mg/L; algal biomass – blue crosses; µg/g or mg/g.
algal biomass – blue crosses
growth medium – red circles
Overall Process Nutrient Distribution -Potential for Reuse with Spent Growth Medium
air/CO2
air/CO2
glucose
alga
lcu
ltu
re
con
cen
trat
ed
alga
e
heterotrophicstage
spen
tg
row
th
med
ium
photoautotrophicstage
NaOH
air
centrifuge
asepticconditions
CO2 800L,15cm(depth)0.25L 2L 40L
racewaypond
bag
5L
lip
id-r
ich
al
gae sp
ent
gro
wth
m
ediu
m
centrifuge
1 2 3 4 5 6
air/CO2
air/CO2
glucose
alga
lcu
ltu
re
con
cen
trat
ed
alga
e
heterotrophicstage
spen
tg
row
th
med
ium
photoautotrophicstage
NaOH
air
centrifuge
asepticconditions
CO2 800L,15cm(depth)
potentialnutrientrecycling
0.25L 2L 40L
racewaypond
bag
5L
nu
trie
nts
lip
id-r
ich
al
gae sp
ent
gro
wth
m
ediu
m
centrifuge
potentialnutrientrecycling
1 2 3 4 5 6
Composition of A. protothecoides biomass (% dw)
ElementPhotoautotrophic
Stage
Heterotrophic
Stage (120 h)
Carbon 49.12 59.2
Oxygen 32.26 26.1
Hydrogen 7.026 9.57
Nitrogen 8.068 1.54
Phosphorus 1.176 0.31
Magnesium 0.19 0.025
Sulfur 0.11 0.012
Iron 0.12 0.018
Calcium 0.045 0.0057
Zinc 5.1x10-3 0.64x10-3
Copper 2.7x10-3 0.2 x10-3
Manganese 4.1x10-3 0.58x10-3
Cobalt 0.31x10-3 0.045x10-3
Molybdenum 0.093x10-3 0.054x10-3
Boron 0.04x10-3 0.003x10-3
ElementPhotoautotrophic
Stage
Heterotrophic
Stage (120 h)
% Difference
Heterotrophic/
Photoautotrophic
Required for 1 L
of produced TAGs
Carbon 49.12 59.2 20.5 1.32
Oxygen 32.26 26.1 (-19.1) 0.58
Hydrogen 7.026 9.57 36.2 0.21
Nitrogen 8.068 1.54 (-80.0) 0.034
Phosphorus 1.176 0.31 (-73.6)0.0069
Magnesium 0.19 0.025 (-86.8)0.56x10-3
Sulfur 0.11 0.012 (-89.1) 0. 27x10-3
Iron 0.12 0.018 (-85.0) 0. 40x10-3
Calcium 0.045 0.0057 (-87.3) 0. 13x10-3
Zinc 5.1x10-3 0.64x10-3 (-87.5) 0.014x10-3
Copper 2.7x10-3 0.2 x10-3 (-92.6) 0. 0044x10-3
Manganese 4.1x10-3 0.58x10-3 (-85.9)0. 013x10-3
Cobalt 0.31x10-3 0.045x10-3 (-85.5) 0. 0010x10-3
Molybdenum 0.093x10-3 0.054x10-3 (-41.1)0. 0012x10-3
Boron 0.04x10-3 0.003x10-3 (-92.5) 0. 067x10-6
Part II: Conclusions
>99% overall nutrients supplied to photoautotrophic stage - significantly larger volume
Photoautotrophic stage nutrient consumption –
• 10-35% Mn, S, Fe, N, Mg, Cu
• < 5% of the P, Mo, Co, B, Zn, and Ca
Heterotrophic stage - Zn, Mo, Mn, Mg, Ca and N, were exhausted (90-99% removal) during the first 25 h.
Total for both stages:
• 10-20% of S, Mn, Fe, N, Cu and less than 5% of Ca, Zn, Mo, Co, P, B were assimilated into algal biomass
Fertilizer demand for algal biofuel maybe overestimated if composition of low-lipid algae is used for estimation
Anaerobic Digestion (AD) of Lipid Extracted Algae
Semi-continuous AD system:
Bioreactor - 3 L spinner flasks at 35C;
Biogas flow - wet-tip gas meter;
Methane - Shimadzu GC-TCD, Hayes Q80/100 column.
Effluent nutrients - filtered (0.45 µm),
N & P Hach TNTplus kits, other by ICP-MS
Run HRT, days Feed, gVS/L OLR, gVS/L-day
1 20 40.91.5 0.970.06
2 20 38.02.0 2.050.08
Operational parameters
Biogas and Methane Production
Energy: Biodiesel vs. Methane vs. Combined
Nutrient Recovery from LEA with the AD Effluent
Recovered Fraction of Nutrient from LEA content
Part III: Conclusions
Lipid extracted algal biomass is a suitable substrate for AD but the
conversion has been limited to ~50% possibly due to recalcitrance;
Inhibition effects from the solvent residues;
Integrated biodiesel-biogas process increased energy yield from
biomass by 30%;
Up to 40-60% of N, P, Mg, Ca, S, and 15-25% of Mn and Fe
contained in the LEA are soluble in AD effluent and potentially
available for recycling;
Soluble Zn, Mo, Co did not exceed 5% in general.
Phycal Inc.:
Ben A. Kessler
Thomas Kula
Dr. F. C. Thomas Allnutt
Funding was provided by: U.S. NSF CBET Program. Grant #1236691 to JHU and by U.S. DOE CCS Program Grant No.DE-FE0001888 to Phycal Inc.
JHU:
Kexin Liu, DOGEE
Dr. Edward J. Bouwer, DOGEE
Dr. Michael J. Betenbaugh, ChemBE
Dr. Yongseok Hong, DOGEE
Our Team
JOHNS HOPKINS
UNIVERSITY