16-19 June 2013, Montreal 10 Annual World …...CO2 Capture Extraction Dewatering Harvesting Photobioreactor Energy Light Waste Water Algae Soil Amendment BYPRODUCTS BIO-OIL Biodiesel

16-19 June 2013, Montreal 10th Annual World Congress on Industrial

Biotechnology and Bioprocessing

Serge R. Guiot [✉[email protected] ☏ +1 (514) 496-6181],

J.-C. Frigon, F. Matteau-Lebrun, B. Tartakovsky

Bioengineering Laboratory, NRC Energy, Mining & Environment

P.J. McGinn, S.J.B. O’Leary

NRC Aquatic & Crops Resource Development

Algal Carbon Conversion

Algal Carbon Conversion Program

2/16

CO2 Capture

Extraction

Dewatering

Harvesting

Photobioreactor

Energy

Light

Waste Water

Algae

Soil Amendment

BYPRODUCTS

BIO-OIL

Biodiesel

Animal Feed

RESIDUAL

Biojet

Pyro Syngas

AD Methane

High Value

Other

Monitoring

FEEDSTOCKS

ALGAE

CULTIVATION

SYSTEMS

Economic Pain Points

Algal Carbon Conversion

Algal Biorefinery Value Chain

Algal Carbon Conversion 3/16

Bioengineering Laboratory Energy, Mining & Environment Portfolio 4/16 ©S.R. Guiot 2013

AD, a must in an algal biorefinery

• Whole-cell perspective:

• microalgae blooms cultivated in open ponds, often for wastewater treatment and

environmental protection purposes → typically diluted & low in lipid content => justifying

lower value use and simple processing approach such as AD

• Algal residue perspective:

• as much as 50% of all cultivated solids can be residue, requiring disposal, particularly if

value added approaches for the use of residual proteins, polysaccharides, and other

chemicals cannot find cost effective separation technologies as well as suitably large and

viable markets

• Both → attractive feedstock for AD

• production of energy and/or fuels as compressed gas

• recovery of associated nutrients, mainly nitrogen and phosphorous

• AD ⇒ significant benefits for reducing energy cost and environmental impacts of an

algal bio-refinery

CO2

Formate

Acetate

Monomers (sugar, amino-acids, fatty acids)

hydrolysis

CH4

methanogenesis

3

Acetogenic bacteria

Ethanol

Butyrate

Propionate

Lactate

H2

2

Acidogenic

fermentative bacteria

4 Methanogenic

archaea

Hydrolytic

fermentative bacteria

1 Anaerobic digestion (AD)

Complex organic matter (cellulose, starch, proteins, lipids …)

Theoretical biochemical methane

potential, from elemental formulas :

CARBOHYDRATES : YCH4 = 0.42 Nm3 / kg

Limiting step: hydrolysis / methanogenesis

Limiting step: proteolysis

PROTEINS : YCH4 = 0.51 Nm3 / kg

Limiting step: LCFA acetogenesis

FATS : YCH4 = 1 Nm3 / kg

Broad feedstock

spectrum + CO2

acetogenesis

5/16 ©S.R. Guiot 2013

Limiting step: hydrolysis

OTHERS (nucleic a., glycoproteins,

…) : YCH4 = 0.5 Nm3 / kg


Algal species screening for biomethane potential (BMP)

Screening of microalgae strains

for methane production was

performed in 500 mL serum

bottles at 35°C and 150 rpm

agitation under optimal conditions

(pH, buffer, nutrients), with

anaerobic sludge as inoculum at

a ratio of 2:1


Typical biphasic time-

courses

Hypothesis: LCFA

accumulation, first

repressing

methanogenesis, then

after adaptation, higher

productivity resumed

Algal species screening for BMP (2)

Incubation (days)

Cu

mu

lati

ve

me

tha

ne

(LS

TP/k

g T

VS

in)





n=15 n=5

Highest YCH4 with

Scenedesmus sp.-

AMDD, Isochrysis sp.

and Scenedesmus

dimorphus: 410, 408

and 397 mLCH4/gVS,

respectively

Degradation efficiency:

72 – 75%


Anaerobic bioprocessing in continuously-fed digesters (CSTR)

• The strain Scenedesmus sp.-AMDD was

chosen as a model strain for processing

testing in continuously-fed digesters (daily

feeding)

• 10 L completely-stirred tank reactor

(CSTR)

• Mechanical mixing at 80 rpm

• Temperature: 35°C

• Feed: 10-20 g TVS/wet kg

• Hydraulic retention time (HRT): 16 to 58 d

• Organic loading rate (OLR): 0.2 - 0.6 g

TVS/Lrx.d


HRT (days) 16 58 58

Cin (g TVS/L) 11 11 20

OLR (g TVS/Lrx.d) 0.7 0.2 0.35

AD in continuous CSTR (2)


Potential factors limiting anaerobic degradation of microalgae

• Hydrolysis limited: cell walls (glycoproteins)

• CSTR : 52% degradation (vs 75% in early BMPs)

• larger portion of recalcitrant organics with the “new” supply of Scenedesmus (modification of the strains, at production, harvesting, storage ?)

255 ± 16 LSTP/g TVSin (46%)

177 ± 43 LSTP/g TVSin(33%)

• inhibition of methanogenic populations by long chain fatty acids (LCFA) • BMP assays with LCFA at concentration of 2.5 and 1.25 g/L showed:

• slow but high yield with palmitic acid (812 ± 10 L/kg),

• strong and permanent inhibition by palmitoleic acid possibly because of transient accumulation

of myristic acid

• fair degradation of eicosapentaenoic acid (EPA) (453 ± 72 L/kg)

• proliferation of sulfate-reducing bacteria


Algal suspension processed in advanced AD technology

• UASB reactor : 3.5 L useful volume - 35°C

• microbial biomass (granules) in reactor (rxr) : 30-40 g VSS/Lrxr

Anaerobic granule

= aggregate of

bacteria, auto-

immobilization

• Inlet concentration : 4 and 8 g TVS/L

• HRT: 2 and 4 days

• OLR: 2 and 4 g TVS/Lrxr·d

• CH4 productivity : 0.54 L (STP) CH4/Lrxr·d

• TVS degradation efficiency : approaching 50% (based on CH4

production)


Pretreatment to improve the digestibility of algae

Crude Microwave Alkaline

Crude Microwave Alkaline

Incubation (days)

Cu

mu

lati

ve m

eth

an

e

(LS

TP/k

g T

VS

ad)


Conclusions

• Target : 20 kg TVS/m3rxr·day; 75% conversion

• Profitable @ FIT $0.15/kWh CHP & C credit $30/t eCO2

• Effective pre-treatment (thermal) combined with advanced AD technology

• Two-stage AD, allowing for targeted optimization 1st stage towards improved hydrolysis, e.g. low pH, high temperature.

Thank you!

Questions – comments ?

Documents

16-19 June 2013, Montreal 10 Annual World …...CO2 Capture Extraction Dewatering Harvesting Photobioreactor Energy Light Waste Water Algae Soil Amendment BYPRODUCTS BIO-OIL Biodiesel