09 mrec ruan algae

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

[email protected]

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]


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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.html


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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

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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

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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

[email protected]

612-625-1710

Q u e s t i o n s ?
mailto:[email protected]:[email protected]

09 mrec ruan algae

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