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7/29/2019 09 MREC Ruan Algae
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Mass Culture of Algae from Waste Water for
Biofuels Production
Roger Ruan, Ph.D., Professor and Director
Center for Biorefining andDepartment of Bioproducts and Biosystems Engineering
1390 Eckles Ave., St. Paul, MN 55108, USA
Problems with current energy
solutions
n Petroleum oil is not only an energy security
issue but also cause environmental pollutions
n Corn ethanol and soybean biodiesel are not
enough and not long term sustainable
n Cellulosic ethanol are too expensive due to
cellulosic biomass collection, transportation, andprocessing
mailto:[email protected]:[email protected]7/29/2019 09 MREC Ruan Algae
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http://zfacts.com/p/35.html
Rising energy cost
Burning fossil fuels increases
atmospheric levels of carbon dioxide
Graph taken from USF Oceanography webpage
Pollution
http://zfacts.com/p/35.htmlhttp://zfacts.com/p/35.html7/29/2019 09 MREC Ruan Algae
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Problems with current energy
solutions
n Petroleum oil is not only an energy security issue
but also cause environmental pollutions
n Corn ethanol and soybean biodiesel are not
enough and not long term sustainable
n Cellulosic ethanol are too expensive due to
cellulosic biomass collection, transportation,
and processing
MicroalgaeMicroalgae
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Algae a biomass factory
n Microalgae are microscopic aquatic plants that carry out the
same process and mechanism of photosynthesis as higher
plants in converting sunlight, H2O + CO2 into biomass +O2:
H2O + CO2 + NH3 + P2O5 + Photons ->
Biomass (CNxHyOz) + O2
n Fast growing, lipid accumulation
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Nutrients in
waste water
CO2 in flu gas
Algaebiomass
Algae culture
Clean Technologies
Why will micro-algae be an optimal renewable
bio-energy resource?
Oil Starch &
Protein
Solid
Residue
BiodieselFeed
Ethanol
Syngas
Bio-oil
Ethanol
CO2 Emissions from
Biodiesel Combustion
Conversion of CO2 to
Biomass via Photosynthesis
Conversion of Biomass
to Biodiesel
CLOSED CARBON CYCLE
Algaebiodiesel
Algae in carbon cycle
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Advantages of algae
n Much greater productivity than their terrestrial cousins
n Non-food resource
n Utilize non-productive land and saline water
n Can use waste CO2 streams
n Can be used to combined with wastewater treatment
n An algal biorefinery could produce oils, protein, and
carbohydrates
n High oil content algae species: Above 50%, some as highas 75%.
Corn: 18
Soybeans: 48
Safflower: 83
Sunflower: 102
Rapeseed: 127
Oil Palm: 635
Micro Algae: 5000-15000
Gallons of Oil Per Acre per Year
There are over 350 oil producing plants and thousands of varieties
Algae produces more oil than all other plants
0
500
1000
1500
2000
2500
1
Different plants
Oilyield(Gallon/year/acre)
Corn
Soybean
Safflower
Sunflower
Rapeseed
Oil palm
Algae
Why will micro-algae be an optimal renewable
bio-energy resource?
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Scale Issue Fuel Need
Objective: to replace all transportation fuel with
biodiesel
Need: 60 billion gal diesel and 120 billion gal
gasoline per year. Convert gasoline to diesel: 120 x
65% = 78 billion gal. Total need: 60+78=138 billion
gal diesel
Complete replacement: 138 x 102% = 140.8 billiongal biodiesel
Scale issue land need
Assuming 15,000 gal/acre, 140.8 billion acre needs
140.8 b/15,000 = 9.5 million acre land.
To put it in perspective: a little more than 1/6 of the
area of the state of Minnesota would be sufficient to
supply all the transportation fuel for the entire
nation.
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Scale issue land need
Algae Lipids biodiesel
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Goals
n Develop technologies for mass culture of
microalgae utilizing nutrients from wastewater
and carbon source from flue gas.
n Harvested algal biomass will be used as a
biomass feedstock for production of biodiesel and
other renewable energy and materials.
Challengesn Unique to algae-wastewater combination
n Algae species that are accustomed to wastewater
environment
n Light transmission
n General
n High oil producing species
n Cost effective photobiorectors (PBR)
n Cost efficient harvest techniques
n Algal biomass processing strategies and techniques
n Large scale demonstration
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Screening algae species based on:
Fast growing in wastewater;
High biomass production;
High oil content;
Require simple culture nutrients.
Algae species screening from local
ponds & lakes
Algae From a Local Ponds
Open pond issues: light penetration depth,
temperature and nutrient control;
Species: environment tolerance,
oil and biomass yields
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Algae from local ponds
Screening algae species and culture
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None Survival
Wastewater Dilutions with H2O
1:8 1:16 1:32
Approach A:
Algal Collections from Local Ponds Placed in
Wastewaters
Single green colonies were found in 5 among 37 collections tested
in a mixture of medium and wastewater. But none in or wastewaters
medium medium + wastewater wastewater
Approach B:
Subcultures of Algal Collections in Media
Placed in Wastewaters
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Fifteen among 46 unialgal strains can grow well in medium + wastewater,
Some of the 15 strain when transferred to and then wastewaters
can still survive. So far, three strains survived in wastewater.
medium medium + wastewater wastewater
Approach C: Local Unialgal Strains
Placed in Wastewaters
Chisti Y (2007)
Oil content of some microalgae
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I II III I II III
K23 7225e
I, medium
II, medium + wastewaterIII, wastewater
Differential Responses of Two Strains
to High-dose Wastewaters
Algae Screening
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Scale up experiments
Some algae strains such as, 12b and r2c,can grow well in the 50% centrate + 50%
media. However 12b is able to suspend inthe media, but r2c will precipitate at the
bottom. The precipitation sometime is due
to the residue polymer which flocculatethe algae biomass.
Algae strain 10b was inoculated intobio-coil with ratio 1:15. After three days
lagging time, algae start growing. In fourdays, the OD can reach 3.5 and the
density is 1.8 gram dry biomass per
liter.
Summary on algae screeningn A optimized strategy for screening was developed, i.e., use
the survived strain in a mixture of medium and wastewateras effective starting materials, then acclimate the strains tohigh-dose wastewaters.
n Fifteen mutation strains grew well in a mixture of mediumand wastewater, their growth is comparable to and evenbetter than that in sole media, including a strain with higheroil yield (K18, 27.2% dry weight in its wild type 6-15-1).
n Three mutation strains survived in sole wastewater, theirgrowth is slower so far. The acclimation is underway.
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Overview of different types of
algae culture systems
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Types of algae culture system
n Open culture system
n Open pond
n Closed culture systems
n Flat-plate
n Tubular
n Vertical-column
n LED PBR
Outdoor/Pond-Powered Biofuels: Turning
Algae into America's New Energy -
Colorado
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Open Pond System
n Prosn Relatively economical in capital
n Consn Little control of culture
conditions, difficulty in growingalgal cultures for long periods
n Poor productivity
n Expensive harvestingn Occupy large land area,
n Limited to few strains of algaen Cultures are easily contaminated
n Major issues with long termsustainability of the system
Flat Plate PBR
n Pros
n Large surface area, good light path, good biomass
productivities
n Low oxygen buildup
n Cons
n Scale-up requires many compartments and supportmaterials, difficulty in controlling culture temperature
n some degree of wall growth, possibility ofhydrodynamic stress to some algal strains
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Tubular PBR
n Prosn Fairly good biomass productivities
n Fairly good mass transfer, good mixing with lowshear stress for large tubes
n Reduced photo-inhibition and photo-oxidation
n Consn Gradients of pH, dissolved oxygen and CO2 along
the tubes, oxygen build upn Some degree of wall growthn Requires large land spacen Construction requires sophisticated materialsn Shear stress to algal cultures
n Decrease of illumination surface area upon scale-up
LED PBR
n Pros
n Good mixing with low shear stress
n Fast light utilization rate
n Cons
n Small illumination surface area
n Relative expensive
n Some degree of wall growth
n Heat generated by LEL light is high
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Algae biomass productivity in some
outdoor PBRs
* C.U. Ugwu et al. / Bioresource Technology 99 (2008) 40214028
Greenhouse Based PBR
n Pros
n Large illumination surface area, good biomass
productivities
n Some control of culture conditions
n Occupy less land mass
n No blockage of light by wall growth, no build up of
dissolved oxygen and CO2
n Cons
n May need supplemental artificial illumination such
as LED lights
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Algae 6-6-9 grows in indoor
condition and greenhouse condition
0.00
0.50
1.00
1.50
2.00
2.50
3.00
0 100 200 300 400
Tim e (h)
O
D
(680nm
)
0.00
0.50
1.00
1.50
2.00
2.50
0 50 100 150 200
Tim e (h)
O
D
(680nm
)
(a) (b)
Algae 6-6-9 grows in (a) indoor condition with light and (b) greenhouse
condition with sunlight and artificial light. The production rate is 1 g /
L/day.
Algae Harvesting
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Flocculation
Developing harvesting technology
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Metroplant experiments
37%37%1.7960.500%2.8700.00Control
91%82%0.2470.5052%1.3710.1013
62%54%1.1000.5016%2.4030.1012
83%68%0.4820.5047%1.5290.1011
92%80%0.2330.5059%1.1810.1010
71%59%0.8290.5029%2.0330.109
86%79%0.4100.5031%1.9680.108
74%66%0.7520.5022%2.2300.107
78%74%0.6230.5015%2.4400.106
73%69%0.7890.5011%2.5600.105
93%86%0.2030.5051%1.4130.104
73%70%0.7770.509%2.6200.103
73%70%0.7700.5011%2.5400.102
64%55%1.0280.5021%2.2600.101
TotalPercent
Reduction
ODReduced
(polymersand Salt)
OD (680nm)
Salt (g/l)
ODReduced
withPolymers
OD (680nm)
Polymer(ml/l)
Polymer
Harvest rate of polymer and salt
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0%
10%
20%
30%
40%
50%
60%
70%
1 2 3 4 5 6 7 8 9 10 11 12 13
Con
trol
Polymers
Algae harvested by 10 type of
polymer
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
1 2 3 4 5 6 7 8 9 10 11 12 13
Con
trol
Polymers with Al2(SO4)3
Algae harvested with both of
polymers and salt
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Algal lipid extraction processesn Expeller/press method:
n Commercially used for vegetable oil extraction
n Dried algae retains its oil content
n Press oil out with an expeller/press
n Hexane solvent oil extraction:n Used in isolation or combined with expeller/press
n Mix dried algae or pulp with cyclohexane
n Oil dissolves in cyclohexane
n Solid can be filtered out
n Separate oil and hexane by distillation
Algal lipid extraction processesn Supercritical fluid/CO2 extraction
n It has the properties of both liquid and gas
n Liquefied fluid is the solvent in extracting the oil
n Require special equipments for pressure
n Other potential methods: making the cell wall fragile
and lipid accessible to solvent
n Enzymatic extraction: enzyme degrades cell walln Osmotic shock treatment: sudden reduction in osmotic
pressure ruptures cell wall
n Ultrasonic extraction: shock waves and liquid jets breakdown the cell wall
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Algal lipid extraction processes
n Pretreatment
n Grinding
n Homogenization
n Nano dispersion
n Ultrasonication
n Supercritical CO2
n Solvent extraction
n Type of solvent: Hexane, chloroform, and methanoln Extraction time: 3hr, 5hr, 7hr, 9hr, 11hr, 13hr, 15hr, and
26 hr
Typical GC profile of fatty
acids obtained from algae
cells (retention time between
28 min to 29 min=16-C fatty
acids, retention time between
31 min to 32 min=18-C fattyacids)
Results and Discussion
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Optimal organic solvent: methanol
Optimal extraction time in terms of extractable
fatty acids: 5 hours
Influence of organic solvent and reaction
time on fatty acids extraction
Effect of ultrasonication and homogenization on extracted fatty
acids content. These two pretreatments conducted in available
equipments in our lab do not have significant influence on fatty
acids extraction from algae cells.
Influence of pretreatment with wet
biomass on fatty acids extraction
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Effect of supercritical CO2 with wet biomass on extracted
fatty acids content
Extracted fatty acids content doubled after supercritical
CO2 treatment.
Extractable
components
(% of dry weight )
Fatty acids components
(% of extract)
Total fatty acids
content
(% of dry weight)
component % of extract
Before supercritical
CO2
(dried powder)
24.11 16-C fatty acids 19.00 10.7018-C fatty acids 25.40
Total fat ty acids 44.4
Solid part aftersupercritical CO2(dried powder)
38.92
16-C fatty acids 27.64
23.1118-C fatty acids 31.75Total fat ty acids 59.39
Influence of nano dispersion on fatty acids
extraction
After nano dispersion treatment, 14-C fatty acids were released , and total
extracted fatty acids increased 62%.
Nano dispersion treated
sample
Untreated sample
C/N ratio 5.1:1.0 4.9:1.0
Extractable components
(% of dry weight)
21.88 22.57
Fatty acid components
(% of extract)
14-C fatty acids 8.89 0.0016-C fatty acids 42.86 43.55
18-C fatty acids 32.51 12.78
Total fatty acids 84.25 51.09
Total fatty acids content
(% of dry weight)18.43 11.39
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Influence of grinding with algae powder on
fatty acids extraction
Grinding has a significant effect on algal fatty acids extraction. After
grinding the extracted fatty acids doubled than that of untreated samples.
Grinded sample Ungrinded sample
Extractable components
(% of dry weight)
37.16 32.96
Fatty acid components
(% of extract)
16-C fatty acids 30.11 20.55
18-C fatty acids 43.04 17.41
Total fatty acids 73.15 37.96
Total fatty acids content
(% of dry weight)
27.20 12.41
Summary on oil extraction
n Optimum extraction organic solvent is methanol and optimal extraction
time is 5 hours.
n Effects of ultrasonication and homogenization were not significant in
terms of total extractable fatty acids.
n Supercritical CO2 with wet and dry biomass were both effective in algal
fatty acids extraction, but the total extractable fatty acids content after
treating the wet biomass was much higher than that with algae powder.
n Nano dispersion is effective in reducing the particle size and releasing
the lipid droplets. It can bring additional benefit to the process by easing
the following drying and grinding.
n Grinding the dried algae chuck can effectively reducing the particle size
and facilitate the Soxhlet extraction process.
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Continuous Hydrothermal Biomass Pyrolysis System
Direct Conversion of
Algal Biomass into
Biofuels
Algae slurry was pumping
into the reactor
Algalbiofuel
productcomingout the
reactor
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Pilot systems
n Small testing systems
n In BBE lab
n Green house
n MECS wastewater treatment plant
n Large system
n ????
Greenhouse growth curve
When using 1/2 harvesting rate and harvesting algae biomass at 1.2 gdry biomass per liter, it took 3 days to get the biomass density back to
the OD of 3.2 that the productivity is 0.4 g L-1 day-1 = 110 g m-2 day-1
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Theoretical greenhouse growth curve
0
0.5
1
1.5
2
2.5
3
0 1 2 3 4 5 6 7
Time (day)
OD(680nm)
When using 1/2 harvesting rate and harvesting algae biomass at 0.9 g
dry biomass per liter per day with OD of 2.5 that the productivity is 0.9 g
L-1 day-1 = 247 g m-2 day-1
Growth curve of batch experiment using 100%,
50% and 25% media
0
0.5
1
1.5
2
2.5
3
3.5
0 2 4 6 8
Days
ODat680nm
Based on the growth curve using batch experiment, using 100% mediaand 1/2 harvesting rate at 0.8 g dry biomass per liter, it took one day to
grow back to the OD of 2.5 that the potential productivity is 0.8 g L-1
day-1 = 220 g m-2 day-1. The light efficiency will reach 80%.
100% media
50% media
25% media
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Growth curve at Metroplant using 50% centrate and 50%
media
Using 1/3 harvesting rate at 0.75 g dry biomass per liter, it took twodays to grow back to the OD of 1.5 that the productivity is 0.36 g L-1
day-1 = 50 g m-2 day-1.
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1/29/09 1/31/09 2/2/09 2/4/09 2/6/09 2/8/09 2/10/09 2/12/09 2/14/09 2/16/09
Days
OD(680nm)
Growth curve from biocoil using
centrate
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
1 3 5 7 911
13
15
17
19
21
23
25
27
29
31
Days
OD(680nm)
When harvest at using 2.5 g dry biomass per liter and 1/3 harvestingrate daily, the productivity is 2.5 g L-1 day-1
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Human activities have increased the entry of chemical and
biological contaminants, particularly nitrogen and phosphorus, into
water.
Microalgae have a great potential for the removal of nitrogen (N)
and phosphorus (P) in wastewater because N and P can be
consumed by algae.
Wastewater treatment
Sample TKN (mg/L) PO4
-3 - P (mg/L) TSS (mg/L)
Centrate 225.62 181.81 912.10
Contents of TKN and PO4-3-P in the Centrate from Metro plant in St. Paul
0.000
0.500
1.000
1.500
2.000
2.500
3.000
1 2 3 4 5 6 7 8 9 10
Time (Day)
OD(680
nm)
100% centrate
75% centrate
50% centrate
100% effluent
100% influent
Wastewater treatment
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Nitrogen and phosphorus consumption analysis in
batch experiment
0
25
50
75
100
125
150
175
200
225
0 1 2 3 4 5 6 7
Full media
1/2 media
1/4 media
NH3-N
Elaps ed me (day)
Ammonia consumption rate using batch
experiment at 100%, 50% and 25% media level
Nitrogen and phosphorus consumption analysis in
batch experiment
0
10
20
30
40
50
60
70
80
90
0 1 2 3 4 5 6 7
Full media
1/2 media
1/4 media
TP(mg/L)
Total phosphorus consumption rate using batchexperiment at 100%, 50% and 25% media level
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Almost half of phosphorous and nitrogen were used. Nutrients were consumed in a
higher rate in the first three days than the latter four days. After day 3, nutrients
consumption became a plateau illustrating that algae growth reached a relatively
slower state compared to the first three days.
Phosphorous and nitrogen consumption analysis in
batch experiment using 50% centrate and 50% media
Nutrients analysis for centrate and normal TAP media
The concentration of carbon source in wastewater was about 47% of TAP
media, the concentration of ammonia was about 39% of TAP media, but the
phosphorous concentration was 6 times higher than TAP media.
COD (mg/L) Total P
(mg PO43-/L)
Ammonia
(mg/L)
Waste water 1730 606 75.9
TAP media 3715 85.1 194
mixture 2620 396 138
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Summary
n Coupling mass algae culture with wastewater
treatment is an economically viable option.
n More than 120 acquired and local algal
species have been tested. Some species
adapted well in waste water.
n Numerous PBRs have been evaluated. Our
model has shown many advantages.
Summaryn Algae can be harvested efficiently and the process
can be easily implemented in wastewater treatmentplan environment.
n Efficient oil extraction options will need to bedeveloped.
n Direct hydrothermal conversion of algae to bio-oilhas great potential in efficient algal biomass
utilization.n Small pilot scale system worked well but scale-up
related data are needed to develop large scaledemonstration system.
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R. Roger Ruan, Ph.D.
Professor and DirectorCenter for Biorefining
Department of Bioproducts and Biosystems EngineeringDepartment of Food Science and Nutrition
University of Minnesota1390 Eckles Ave., St. Paul, MN 55113
612-625-1710
Q u e s t i o n s ?
mailto:[email protected]:[email protected]